JP3493647B2 - Power supply device, discharge lamp lighting device and lighting device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for outputting a high frequency voltage using a switching circuit, and a power supply device, a discharge lamp lighting device, and a lighting device for compensating for variations in input voltage from an AC power supply.

[0002]

2. Description of the Related Art Conventionally, as an apparatus of this type (an apparatus for outputting a high frequency voltage at a high rate by using a switching circuit), Japanese Patent Application No. 6-178925 and Japanese Patent Application No.
What is shown in the specification of 254344 is known. An example of these will be described below with reference to the drawings.

FIG. 12 is a circuit diagram showing an example of the prior art of the present invention. In FIG. 12, a commercial AC power supply 41 is connected to a filter circuit 43 including a choke coil 42 and a capacitor C5, and a rectifier circuit 44 is connected to the filter circuit 43. The rectifier circuit 44 is composed of, for example, a high-speed switching diode.
A first switching circuit 45 (for example, the drain of a MOSFET) is connected to the positive terminal of the output end of the rectifier circuit 44, and a second switching circuit 46 (for example of the MOSFET) is connected to the negative terminal of the output end of the rectifier circuit 44. The source) is connected, and the first switching circuit 45 and the second switching circuit 46 are connected in series. The switching circuits 45 and 46 are composed of, for example, MOSFETs (field effect transistors) as described above, and the parasitic diodes of the respective elements are used as diodes for reverse current flow. .

Further, in parallel with the first switching circuit 45, the primary side winding L1 of the leakage transformer T1 and the first winding L1
And a capacitor C3 is connected in series. The first capacitor C3 has a smoothing effect on the output frequency of the rectifier circuit 44. A fluorescent lamp (discharge lamp) 49 is connected to the secondary winding L2 of the leakage transformer T1.
A condenser C2 for preheating the filament is connected between the filaments of both electrodes. The leakage inductance of the leakage transformer T1 also acts as the current limiting impedance of the fluorescent lamp 49.

Further, in parallel with the second switching circuit 46, a series circuit composed of a primary side winding L1 of the leakage transformer T1 and a second capacitor C5 is connected. The capacity of the second capacitor C5 is extremely smaller than that of the first capacitor C3, and is set (to a value) so as to resonate at the switching frequency of the switching circuits 45 and 46 together with the leakage inductance of the leakage transformer T1. Has been done.

On the other hand, the control circuit 52 controls ON / OFF of the switching circuits 45 and 46,
The control circuit 52 performs on / off control of the switching circuits 45 and 46 at a frequency higher than the output frequency of the rectifying circuit 44, which is substantially constant, and outputs the output voltage of the AC power supply 41 (rectifying circuit 44).
The control is performed so that the ON period of the second switching circuit 46 has a relationship as shown in FIG. 13 in accordance with the peak value of the output voltage). That is, while the peak value of the output voltage of the rectifier circuit 44 is large, the second switching circuit 4 is
Control is performed so that the ON period of 6 is short and the ON period is long in a period where the peak value is small. In addition, the ON period of the first switching circuit 45 is as shown in FIG.
As shown in FIG. 5, control is performed so that the relationship is opposite to that in the case of the second switching circuit 46. Incidentally, FIG. 13 shows the first voltage with respect to the output voltage of the rectifier
FIG. 6 is a diagram showing a change state of the ON periods of the second switching circuits 45 and 46.

Specifically, the control circuit 52 comprises a detecting means 52a for detecting the output voltage of the rectifying circuit 44, and an oscillating means 52b for changing the ON period according to the detecting voltage of the detecting means 52a. There is. The oscillating means 52b is composed of, for example, a PWM (pulse width adjustment) control function and a switching circuit drive function.
Specific means having a control function includes, for example, a PWM control IC that is mainly composed of this IC (circuit, device, etc.). Specific means having a switching device driving function include a buffer and a transformer. And a transmission means such as a photocoupler (circuit, device, etc.). The oscillation means 5
It is also possible to provide an external control signal input section 52c in 2b and control the ON period of the switching circuits 45 and 46 by an external control signal.

Next, the operation of FIG. 12 will be described with reference to FIGS.
Will be described with reference to. Incidentally, FIG. 14 is a simplified diagram showing only a main part necessary for explanation in the circuit diagram showing an example of the prior art of the present invention, and the same parts as those in FIG. 12 are designated by the same reference numerals. is there. Further, FIGS. 15 and 16 show voltage and current waveforms of respective parts, where V is voltage and I
Indicates the current, and the respective symbols are the same as those in FIG. 12 (however, VG in FIG. 15 and FIG. 16A)
S5 indicates the gate-source voltage of the first switching circuit (MOSFET) 45, and (5) indicates the gate-source voltage of the second switching circuit (MOSFET) 46, respectively. The horizontal axis (time axis) of 16 corresponds to the cycle of each switching frequency.
Further, FIG. 17 shows the voltage and current waveforms of each part,
The horizontal axis corresponds to the cycle of the output frequency of the rectifier circuit 44.

First, a period in which the peak value of the output voltage (non-smoothed DC voltage) of the rectifier circuit 44 is large will be described with reference to FIGS. 14 and 15. During this period, as shown in FIG.
In this period, the ON period of the second switching circuit 46 is controlled to be relatively short according to the detected voltage detected by a.

Now, the period (a), that is, the period a on the horizontal axis (time axis) of FIG. 14A and FIG.
(Same below), the first capacitor C3, the first
The switching circuit 45 and the closed circuit of the primary winding L1 of the inductor T1 are formed. As a result, the electric charge accumulated in the first capacitor C3 flows (discharges) through the closed circuit, and the current I45 and IC3 as shown in FIGS. 15B and 15H flow.

On the other hand, in the period (b), the first switching circuit 45 is turned off, and the second switching circuit 46 is turned on in the direction shown in FIG. 2 (b) by its parasitic diode. As a result, the primary winding L1 of the inductor T1 and the second capacitor C5 exhibit series resonance, and as shown in FIGS.
Will flow, and the primary winding L1 of the inductor T1 will flow.
And the second capacitor C5 have a resonance voltage V5
1, V47 appears. Also, the second capacitor C5
A resonance voltage also appears in the voltage V44 across the rectifier circuit 44, which is equal to the sum of the voltage of the first capacitor C3. The peak value of the resonance voltage is the energy stored in the primary winding L1 of the inductor T1, that is, the current (I4 flowing in the first switching circuit 45 at the end of the period (a)).
5), and the voltage across the second capacitor C5 (V5
1).

In the period (c), the second switching circuit 46 is turned on, the polarity of the resonance current is inverted,
A resonance current as shown in FIG. 14C flows in the opposite direction to that in the period (b) (FIGS. 15D and 15D). By the way, in the period (b) and the period (c), the peak value of the resonance voltage is the output voltage (non-smoothed DC voltage) of the rectifier circuit 44 because the resistance component of the resonance circuit is small.
Get bigger. That is, the pressure is increased.

Then, in the period (d), the resonance voltage decreases (attenuates), and similarly the first capacitor C3.
In addition, the voltage across the terminals of the second capacitor C5 also decreases, and the rectifier circuit 44 causes the first capacitor C3 and the inductor T1 to
Primary winding L1, and second switching circuit 46
Currents I44 and I46 flow through (FIG. 15).
(F), (H), (D)).

Further, in the period (e), the second switching circuit 46 is turned off, and the first switching circuit 45 is turned on in the direction shown in FIG. 6 (e) by its parasitic diode. As a result, the current I45 and IC3 flow through the parasitic diode of the first switching circuit 45 and the first capacitor C3 due to the energy stored in the primary winding L1 of the inductor T1 (FIG. 15 (b),
(H)). Then, the state returns to the state of the period (a).

Next, the period during which the peak value of the output voltage (non-smoothed DC voltage) of the rectifier circuit 44 is small will be described. FIG. 16 is a diagram showing the voltage and current waveforms of each part in a period in which the peak value of the output voltage of the rectifier circuit 44 is relatively small, corresponding to the switching frequency.

During the period when the peak value of the output voltage (non-smoothed DC voltage) of the rectifier circuit 44 is small, as shown in FIG. 13, the control circuit 52 operates in accordance with the detection voltage detected by the detection means 52a. Second switching circuit 46
Is a period in which control is performed so that the ON period of is relatively long. The circuit operation in this case is basically the same as that in the case of FIG. 14, but the voltage and current waveforms of the respective parts are as shown in FIG. What should be noted in FIG. 16 is that the peak value of the resonance voltage is larger than that in FIG. 15 as shown in FIGS. this is,
While the peak value of the unsmoothed DC voltage output from the rectifier circuit 44 is small, the voltage charged in the second capacitor C5 becomes small in accordance with this peak value (see FIGS. 15 and 1).
This is because the current flowing into the second capacitor C5 by this amount, that is, the initial resonance current value in the period (b) increases. Therefore, during the period when the peak value of the non-smoothed DC voltage is small, the voltage can be further boosted and the valley portion of the non-smoothed DC voltage can be raised. In the circuit shown in FIG. 12, the ON period of the switching circuits 45 and 46 is controlled in the relationship shown in FIG. 13 as described above. First switching circuit 45
The ON period of is relatively small. This allows
The value of the current flowing through the first switching circuit 45 is cut off when the current value is relatively small. This acts to reduce the initial resonant current value in the period (b), so
As described above, the resonance voltage increases due to the charging voltage of the second capacitor C5, but the resonance voltage does not extremely increase and the voltage value of the valley portion does not increase excessively.

As described above, high-frequency alternating current is induced in the secondary winding L2 of the inductor T1, and the fluorescent lamp 49 is lit at high frequency. The input current I44 from the commercial AC power supply 41 at this time is as shown in FIG. This is because, as described above, the current from the rectifier circuit 44 in the period (d) flows over substantially the entire period of the unsmoothed DC voltage output from the rectifier circuit 44. Therefore, this current increases the input power factor and contributes to the low distortion of the input current. Note that FIG. 17 is a diagram showing the input current, the output end-to-end voltage, and the load current waveform of the rectifier circuit 44 in correspondence with the output frequency of the rectifier circuit 44. Also,
The high frequency component of the input current I44 can be easily absorbed (removed) by a filter circuit or the like.

Further, the voltage V44 between the output terminals of the rectifying circuit 44
17 (b), and the current flowing through the fluorescent lamp 49 is as shown in FIG. 17 (c). This is because the envelope of the first capacitor C3 is smoothed by the first capacitor C3 and the ripple of the non-smoothed DC voltage is reduced. In FIG. 17B, the white sine wave part shows the unsmoothed DC voltage output from the rectifier circuit 44, and the part superimposed on this sine wave shows the voltage boosted by resonance. Shows. In order to make the voltage V44 between the output terminals smoother, the switching circuit 4
The ON period control of Nos. 5 and 46 may be changed more greatly than that shown in FIG.

By the way, as described above, FIG.
A device for outputting a high-frequency voltage with a high power factor and an input current with a low distortion by using a switching circuit as shown in (1) is extremely effective (excellent). However, in such a device, there is no description of how to deal with the case where the input power supply voltage fluctuates, for example, the input voltage exceeding the rating is supplied or the input voltage lower than the rating is supplied. That is, in the former case, the high voltage (high power) supplied may damage the lamp, and in the latter case, the low voltage may reduce the brightness of the lamp (for example, a discharge lamp) or cause flicker, Alternatively, it may be turned off.

[0020]

As described above, a device which uses a conventional switching circuit to output a high-frequency voltage with a high power factor and an input current with a low distortion is extremely effective (excellent), but When the supplied power supply voltage fluctuates, there is a problem that the brightness of a lamp (for example, a discharge lamp) is lowered or flickers.

Therefore, the present invention has been made in view of the above problems.
It is an object of the present invention to provide a power supply device, a discharge lamp lighting device, and a lighting device that do not reduce the lamp brightness or flicker even when the supplied power supply voltage fluctuates.

[0022]

According to a first aspect of the present invention, there is provided a power supply device which rectifies an AC power supply voltage and outputs a non-smoothed DC voltage. The rectification circuit is connected in parallel between output terminals of the rectification circuit. First and second switching circuits connected in series, which are alternately turned on / off to switch at a frequency higher than the output frequency of the rectifier circuit; and are provided in parallel to the first switching circuit. During the ON period of the second switching circuit, the output frequency of the rectifier circuit, which is charged by the output of the rectifier circuit through the second switching circuit, is subjected to smoothing processing, and the first switching circuit is turned on. a connection point of said first and second switching circuits; the first capacitor and a relatively large capacity for discharge through said first switching circuit to charge electric charges during the period An inductor provided between the first capacitor and a charge / discharge current of the first capacitor; and a inductor that resonates with the inductor according to ON / OFF of the first and second switching circuits. A second capacitor having a small capacity; a current detection circuit for detecting a current flowing through the first switching circuit; and controlling an ON period of the first switching circuit based on a detection signal of the current detection circuit. An on-duty variable circuit; a power supply voltage detection circuit that detects a change in the AC power supply voltage and outputs a detection signal; a switching frequency of the first and second switching circuits based on a detection signal from the power supply voltage detection circuit An output control circuit for changing the output voltage; and an output circuit for obtaining a high frequency output by resonance of the inductor and the second capacitor. Characterized in that it was.

A power supply device according to a second aspect of the present invention is the power supply device according to the first aspect, wherein the power supply voltage detection circuit detects the fluctuation of the power supply voltage by the first capacitor having a relatively large capacity. The power supply device according to claim 3 is the power supply device according to claim 1, wherein the power supply voltage detection circuit is configured to detect the fluctuation of the power supply voltage. The detection is performed by detecting a peak value of a current flowing through the second switching circuit connected in a path for charging the relatively large-capacity first capacitor. Although the first and second switching circuits are field effect transistors (MOSFETs), they may be replaced with a bipolar transistor and a diode connected in anti-parallel to the bipolar transistor. Further, the means for detecting the peak value of the current includes an Isw detection circuit and an Isw (peak) detection circuit, and the Isw detection circuit is connected to the drain terminal side of the second switching circuit (for example, MOSFET). However, it may be arranged on the source terminal side.

A power supply device according to a fourth aspect of the present invention is the power supply device according to any one of the first to third aspects, wherein the output control circuit is configured to detect the power supply voltage by the detection signal from the power supply voltage detection circuit. When an increase is detected, the switching frequencies of the first and second switching circuits are increased according to the degree of the increase, and the decrease in the power supply voltage is detected by the detection signal from the power supply voltage detection circuit. In this case, the switching frequency of the first and second switching circuits is controlled so as to be lowered according to the degree of the reduction, and the power supply device according to the invention of claim 5 is characterized in that In the power supply device according to any one of 1 to 3, the output control circuit may change the oscillation frequency based on a detection signal from the power supply voltage detection circuit that detects a power supply voltage. The power supply device according to claim 6 is characterized in that a switching frequency of the first and second switching circuits changes in proportion to an oscillation frequency of the oscillator. In the power supply device, the output control circuit raises the oscillation frequency of the oscillator according to the degree of the rise when the rise of the power supply voltage is detected by the detection signal from the power supply voltage detection circuit, When a decrease in the power supply voltage is detected by the detection signal from the power supply voltage detection circuit, the oscillation frequency of the oscillator is controlled so as to be decreased according to the degree of the decrease.

A power supply device according to the invention of claim 7 is
A rectifier circuit that rectifies an AC voltage and outputs an unsmoothed DC voltage; connected in parallel between the output terminals of the rectifier circuit, and alternately turns on / off to switch at a frequency higher than the output frequency of the rectifier circuit First and second switching circuits connected in series; provided in parallel with the first switching circuit, and rectifying via the second switching circuit during an ON period of the second switching circuit. A relatively large capacity that is charged by the output of the circuit, performs smoothing processing on the output frequency of the rectifier circuit, and discharges the charged electric charge through the first switching circuit during the ON period of the first switching circuit. A first capacitor; provided between a connection point of the first and second switching circuits and the first capacitor, and charging and discharging the first capacitor. An inductor that flows through; a second capacitor having a relatively small capacity that resonates with the inductor in response to ON / OFF of the first and second switching circuits; and an unsmoothed output terminal of the rectifier circuit. An overvoltage detection circuit connected in parallel with the rectifier circuit for detecting that an overvoltage is applied to the DC voltage; comparing the voltage value output from the overvoltage detection circuit with a predetermined reference value level to detect the overvoltage A comparator circuit that outputs a protection signal when the voltage value output from the circuit exceeds the reference value level; and a switching control circuit that turns off the operation of the second switching circuit when the protection signal is input. It is characterized by having. In the present invention, as the first and second switching circuits, a field effect transistor (MOSFET),
Examples include a bipolar transistor and a diode circuit that is connected in antiparallel to the bipolar transistor. Further, the overvoltage detection circuit may be a circuit configured by using a means capable of detecting a voltage such as a resistor or a capacitor.

A power supply device according to an eighth aspect of the present invention is the power supply device according to the seventh aspect, wherein the first switching circuit and the first capacitor are connected to a low potential side of the circuit, and the second The switching circuit and the second capacitor are connected to the high potential side of the circuit, and the power supply device according to the invention of claim 9 is the power supply device of claim 7 or 8. In the above, the turn-off control in the second switching circuit is performed during a period in which the voltage value output from the overvoltage detection circuit exceeds the reference value level. Since the comparison circuit determines whether or not the output of the overvoltage detection circuit exceeds the reference level after the second switching circuit is turned on, the turn-off control is not actually performed. A slight delay in response occurs.

A power supply device according to a tenth aspect of the present invention is the power supply device according to the seventh or eighth aspect, wherein the turn-off control in the second switching circuit is such that the voltage value output from the overvoltage detection circuit is: It is characterized in that it is carried out for a period from when the reference value level is exceeded to when a predetermined time has elapsed. Incidentally, the second
Since the comparison circuit determines whether or not the output of the overvoltage detection circuit exceeds the reference level after the switching circuit is turned on, there is a slight delay in response until the turn-off control is actually performed. Occurs.

The power supply device according to an eleventh aspect of the present invention is the power supply device according to the seventh or eighth aspect, wherein the turn-off control in the second switching circuit is such that the voltage value output from the overvoltage detection circuit is: it is characterized in that the dividing line to any long period of time if the period from the period started exceeds the reference value level until the period ends, or from the period start until after a predetermined time has elapsed. Since the comparison circuit determines whether or not the output of the overvoltage detection circuit exceeds the reference level after the second switching circuit is turned on, the turn-off control is not actually performed. A slight delay in response occurs.

A power supply device according to a twelfth aspect of the present invention is the power supply device according to any one of the seventh to eleventh aspects, wherein the first and second switching circuits have a duty ratio under a constant switching frequency. The power supply device according to claim 13 is controlled in the power supply device according to any one of claims 7 to 11, wherein each of the first and second switching circuits has an ON time. It is characterized by being controlled.

A discharge lamp lighting device according to a fourteenth aspect of the present invention comprises the power supply device according to any one of the first to thirteenth aspects; and a discharge lamp that is energized by the output of the power supply device. It is characterized by being present.

An illumination device according to a fifteenth aspect of the present invention comprises the illumination device body and the discharge lamp lighting device according to the fourteenth aspect.

[0032]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the first of the present invention.
3 is a circuit diagram showing an embodiment of FIG. The embodiment of the present invention relates to a device that compensates for the fluctuation of the power supply voltage by detecting the average value of the power supply voltage input to the device.

In FIG. 1, the commercial AC power supply 16 is supplied to the rectifier circuit 15 via a line filter 17,
The rectifier circuit 15 rectifies the AC voltage supplied from the commercial AC power supply 16 and outputs it as an unsmoothed DC voltage. The positive output terminal of the rectifier circuit 15 is connected to the positive input terminal 51 of the inverter circuit 18, and the negative output terminal is connected to the negative input terminal 52 of the inverter circuit 18, respectively.

The inverter circuit 18 is, for example, an MO.
A charge side SW circuit 21 (second switching circuit) and a discharge side SW circuit 22 (first switching circuit) each including an SFET, an output control circuit 23, and a first capacitor C3 that is a smoothing large-capacity capacitor, A second capacitor C5 having a smaller capacity than the first capacitor C3, an inductor T1 including an inverter transformer, an Isw detection circuit 4 for detecting a current, and an Isw (peak) detection circuit 5 for detecting a current peak value. It is composed by.

The inverter circuit 18 will be described in detail below. Input terminal 5 on the positive side of the inverter circuit 18
1 is the drain-source path of the charge side SW circuit 21, Is
The drain of the w detection circuit 4 and the discharge side SW circuit 22
Inverter circuit 18 via a series circuit composed of a source path
Is also connected to the negative input terminal 52 of the inverter circuit 18 through a series circuit including the second capacitor C5 and the first capacitor C3. The connection point between the charge side SW circuit 21 and the Isw detection circuit 4 is connected to the connection point between the second capacitor C5 and the first capacitor C3 via the primary side winding L1 of the inductor T1. By being connected in this way, the second capacitor C5 and the first capacitor C3, each of the charging-side SW circuit 2
It will be provided in parallel to one and the discharge collector side SW circuit 22.

Then, the Isw detection circuit 4 detects the current flowing through the discharge side SW circuit 22 and outputs Is as the detection voltage V1.
It is supplied to the w (peak) detection circuit 5. Further, the Isw (peak) detection circuit 5 detects the peak value of the voltage V1 and supplies the peak value of this detection result to the terminal 53 of the output control circuit 23 as the peak value voltage V2. That is, the Isw detection circuit 4 and the Isw (peak) detection circuit 5 configure a current peak value detection circuit that detects the peak value of the current flowing through the discharge side SW circuit 22.

Further, the output control circuit 23 outputs the oscillation signal a1.
And b1 are respectively supplied to the gates of the charge side and discharge side SW circuits 21 and 22 to alternately turn on / off the charge side SW circuit 21 and the discharge side SW circuit 22, and from the Isw (peak) detection circuit 5. Peak value detection voltage V
The on-duty ratio of the charge side SW circuit 21 and the discharge side SW circuit 22 is kept constant by controlling 2 to keep constant.

On the other hand, the filaments at both ends of the discharge lamp 49 have a filament heating capacitor C2 and an inductor T.
1 is connected to the secondary winding L2. That is, the discharge lamp 4
9 and the capacitor C constitute an output circuit of the inductor T1.

Next, the output control circuit 23 constituting the inverter circuit 18 will be described. Output control circuit 2
3 is largely the on-duty variable circuit 31 and the FET
And a driver (driving circuit) 14.

The on-duty variable circuit 31 uses the Is
The FET driver 14 detects the peak value detection voltage V2 from the w (peak) detection circuit 5, and based on the detection result.
The variability control of the duty ratio of the oscillation signals a1 and b1 output by That is, when the peak value detection voltage V2 is high, the duty ratio with which the oscillation signal b1 is at a high level is reduced, and the duty ratio with which the oscillation signal a1 is at a high level is increased, so that the discharge side S
The on-duty ratio of the W circuit 22 is reduced and the charging side SW
The control is performed so that the on-duty ratio of the circuit 21 is increased. On the other hand, when the peak value detection voltage V2 is low, the duty ratio at which the oscillation signal b1 becomes high level is increased,
Control is performed so that the on-duty ratio of the discharge side SW circuit 22 is increased and the on-duty ratio of the charge side SW circuit 21 is decreased by decreasing the duty ratio at which the oscillation signal a1 becomes high level.

The on-duty variable circuit 31 includes a resistor R
1, R2, capacitor C1, error amplifier 6, DC constant voltage source E1, VFO (voltage / frequency conversion circuit) 7, and P
A terminal 53 of the on-duty variable circuit 31, which is composed of a WM (pulse width control circuit) 13 and is supplied with the peak value detection voltage V2, is connected to the inverting input terminal (-) of the error amplifier 6 via the resistor R1. ing. The DC constant voltage source E1 is connected to the non-inverting input terminal (+) of the error amplifier 6 and supplies the DC constant voltage V3 to the non-inverting input terminal (+) of the error amplifier 6.

Further, a resistor R2 is provided between the inverting input terminal (-) of the error amplifier 6 and the output terminal of the error amplifier 6.
And a parallel circuit consisting of a capacitor C1 is connected,
The output terminal of the error amplifier 6 is PWM (pulse width control circuit)
It is connected to 13. When the error amplifier 6 tries to increase the peak value detection voltage V2 with respect to the DC constant voltage (reference voltage) V3 from the DC constant voltage source E1,
When the output voltage V5 from the output terminal of the error amplifier 6 is reduced and the peak value detection voltage V2 becomes smaller than the reference voltage V3, the output voltage V5 from the output terminal is increased.

On the other hand, PWM (pulse width control circuit) 13
Is configured to output a pulse signal p1 having a predetermined frequency based on an oscillation signal from a VFO (voltage / frequency conversion circuit) 7, and when the output voltage V5 from the error amplifier 6 is large, the pulse signal The time width of the pulse of the signal p1 is lengthened, and when the output voltage V5 from the error amplifier 6 is small, the time width of the pulse of the pulse signal p1 is shortened.

Based on this, the FET driver (driving circuit) 14 turns on the discharge side SW circuit 22 during the period when the pulse signal p1 from the PWM (pulse width control circuit) 13 is "H" (pulse period). , The oscillation signal b1 for turning off the discharge side SW circuit 22 in the other period of "L" is supplied to the control signal input terminal (eg, gate) of the discharge side SW circuit 22, and the PWM (pulse width control circuit) 13 The oscillation signal a1 that turns off the charging side SW circuit 21 during the period when the pulse signal p1 from H is "H" (pulse period) and turns on the charging side SW circuit 21 during the other period when the pulse signal p1 is "L" is charged. The control signal input terminal (eg, gate) of the side SW circuit 21 is supplied.

By the way, the VFO (voltage / frequency conversion circuit) 7 is supplied with the average value V4 of the power supply voltage from the power supply voltage detection circuit 8, and the VFO 7 generates an oscillation signal based on the average value V4 of the power supply voltage. The signal is supplied to the PWM (pulse width control circuit) 13. The power supply voltage detection circuit 8 includes the rectification circuit 15, low-speed power supply rectification diodes 9a and 9b, and a smoothing circuit 10 having a time constant capable of sufficiently smoothing the supplied power supply voltage. The smoothing circuit 10 is composed of resistors R3, R4 and a capacitor C4.

On the other hand, in the power supply voltage detection circuit 8, the anodes of the diodes 9a and 9b are respectively connected to the two AC power supply terminals of the rectifier circuit 15, and the cathodes of the diodes 9a and 9b are commonly connected. Along with
It is connected to a reference potential point (ground) via the resistor R3 and a parallel circuit composed of a capacitor C4 and a resistor R4. Then, the average value V4 of the power supply voltage, and the resistor R3, and is supplied to the VFO7 from the connection point between the parallel circuit consisting of the capacitor C4 and the resistor R4.

Next, referring to FIG. 2, the operation (operation) of the device configured as described above for outputting a high-frequency voltage with a high power factor and an input current with a low distortion using the switching circuit according to the present invention will be described. While explaining. FIG. 2 is a timing chart showing the relationship between the output voltage of the rectifier circuit 15 controlled by the output control circuit 23 of FIG. 1 and the ON time of each of the charge side SW circuit 21 and the discharge side SW circuit 22, 2A shows the output voltage of the rectifier circuit 15, and FIG. 2B shows the on-time of the charge side and discharge side SW circuits 21, 22 with respect to the output voltage of the rectifier circuit 15.

As shown in FIG. 2, the charging side SW circuit 21 and the discharging side SW circuit 22, which are the two switching circuits, have a large peak value of the output voltage of the rectifier circuit 15 (the output voltage of the commercial AC power supply 16). Sometimes the discharge side SW circuit 2
2 has a long ON period, the charging SW circuit 21 has a short ON period, and when the peak value of the output voltage of the rectifier circuit 15 (the output voltage of the commercial AC power supply 16) is small, the discharging SW circuit 2
The ON period of 2 is short and the ON period of the charging side SW circuit 21 is controlled to be long. That is, the charge side SW circuit 21 and the discharge side SW that are two switching circuits
The ON period of each of the circuits 22 is as shown in FIG.
It is designed to change in the opposite relationship.

Now, assuming that the power supply voltage supplied from the commercial AC power supply 16 is constant, the output voltage of the commercial AC power supply 16 is supplied to the rectifier circuit 15 via the line filter 17 and full-wave rectified, and the inverter is used. It is supplied to the circuit 18 and the power supply voltage detection circuit 8. On the other hand, the output control circuit 23 that constitutes the inverter circuit 18 includes the charging side SW.
The circuit 21 and the discharge side SW circuit 22 are alternately switched at a frequency higher than that of the commercial AC power supply 16 to induce a high frequency AC voltage in the secondary winding L2 of the inductor T1 to light the discharge lamp 49 at a high frequency.

At this time, a resonant voltage is generated in the capacitor C5 and the inductor T1, and the voltage of the capacitor C3 is switched by the resonant voltage for one cycle of the charging side SW circuit 21 and the discharging side SW circuit 22. It is suppressed to be lower than the unsmoothed DC voltage rectified by the rectifier circuit 15. As a result, the power factor improving current flows during the period when the peak value of the voltage rectified by the rectifying circuit 15 is low, the input power factor of the commercial AC power source 16 is improved, and the distortion of the input current is reduced.

If the power supply voltage supplied from the commercial AC power supply 16 fluctuates for some reason, as described above, for example, when an input voltage exceeding the rating is supplied, the supplied high voltage is supplied. The voltage (high power) may damage the lamp (eg discharge lamp), and when an input voltage lower than the rating is supplied, the low voltage may cause the lamp to flicker, reduce the brightness of the lamp, or turn off the lamp. Problems such as doing occur.

On the other hand, in a device which outputs a high-frequency voltage with a high power factor and an input current with a low distortion using the above-mentioned switching circuit, for example, as shown in FIG. 3, the switching circuit (the charge side SW circuit 21 and When the operating frequency (switching frequency) of the discharge side SW circuit 22) is increased, the high frequency output voltage (power), that is, the output voltage (power) supplied to the discharge lamp 49 in the embodiment of the present invention is lowered. It has characteristics (there may be the opposite depending on the circuit configuration). 3 is a characteristic diagram showing an example of the relationship between the operating frequency (switching frequency) and the output voltage (power).

Therefore, when the power supply voltage supplied from the commercial AC power supply 16 fluctuates and an input voltage exceeding the rating is supplied, the switching circuit (charging side S
The damage of the lamp can be prevented by increasing the operating frequency (switching frequency) of the W circuit 21 and the discharge side SW circuit 22). On the contrary, when an input voltage lower than the rating is supplied, the switching circuit (charge side SW circuit 2
By reducing the operating frequency (switching frequency) of 1 and the discharge side SW circuit 22), it is possible to prevent the flickering of the lamp, the decrease of the lamp brightness, and the extinguishment (mismatch) of the lamp.

That is, according to the present invention, when a fluctuation occurs in the power supply voltage supplied from the commercial AC power supply 16 for some reason, and an input voltage exceeding the rating is supplied, the power supply voltage is detected. A power supply voltage value exceeding the rating smoothed (averaged) by the smoothing circuit 10 constituting the circuit 8 is supplied to the VFO (voltage / frequency conversion circuit) 7 as an average value V4 of the power supply voltage, and VFO 7 is As shown in FIG. 4, the PWM (pulse width control circuit) 1 generates an oscillation signal having a higher frequency than the rated time based on the average value V4 of the power supply voltage.
3 and the FET driver 14 operates at the operating frequency based on the high-frequency oscillation signal from the PWM 13 and outputs the switching circuit (the charge side SW circuit 21 and the discharge side SW circuit 2).
By driving 2), a constant output voltage that does not exceed the rating is supplied to the discharge lamp (load) 49.

When an input voltage with a lower rating is supplied, the power supply voltage value that has not reached the rating and is smoothed by the smoothing circuit 10 constituting the power supply voltage detection circuit 8 is the average value V4 of the power supply voltage. Is supplied to the VFO (voltage / frequency conversion circuit) 7, and as shown in FIG. 4, the VFO 7 generates an oscillation signal of a lower frequency than the rated time based on the average value V4 of the power supply voltage by the PWM (pulse width control circuit). 13 and the FET driver 14 drives the switching circuit (the charge side SW circuit 21 and the discharge side SW circuit 22) at an operating frequency based on the low frequency oscillation signal from the PWM 13 to discharge the discharge lamp (load) 49. In contrast, a constant output voltage that does not drop below the rated value is supplied. FIG. 4 is a characteristic diagram showing an example of the relationship between the smoothed output voltage output by the power supply voltage detection circuit 8 and the oscillation frequency (operating frequency) of the VFO 7.

As described above, according to the first embodiment of the present invention, a constant high frequency voltage is always output even if the power supply voltage supplied from the commercial AC power supply 16 fluctuates for some reason. can do.

Next, a second embodiment of the present invention will be described. FIG. 5 is a circuit diagram showing a second embodiment of the present invention. The embodiment of the present invention relates to a device for compensating the fluctuation of the power supply voltage by detecting the average value of the voltage after rectifying the power supply voltage input to the device.

In FIG. 5, the same parts as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. Also, the description of the components other than the essential parts of the invention is omitted.

The power supply voltage detection circuit 8 which is the main part in FIG. 5 is composed of a rectifier circuit 15 and a smoothing circuit 10 having a time constant capable of sufficiently smoothing the supplied power supply voltage. Circuit 10 includes resistors R3, R4
And a capacitor C4.

The positive side terminal of the rectifier circuit 15 which constitutes the power supply voltage detection circuit 8 outputs the unsmoothed DC voltage, and the resistor R3 which constitutes the smoothing circuit 10 and the capacitor C4 which is connected in series to the resistor R3. It is connected to the reference potential point GND through a parallel circuit composed of the resistor R4. Further, the average value V4 of the power supply voltage is configured to be supplied to the VFO (voltage / frequency conversion circuit) 7 from the connection point of the resistor R3 and the parallel circuit including the capacitor C4 and the resistor R4.

Next, the operation will be described. When the power supply voltage supplied from the commercial AC power supply 16 fluctuates for some reason, and an input voltage exceeding the rating is supplied to the inverter circuit 18, for example, the smoothing which constitutes the power supply voltage detection circuit 8 is performed. A power supply voltage value exceeding the rating, which is the unsmoothed DC voltage of the rectifier circuit 15 smoothed by the circuit 10, is supplied to the VFO (voltage / frequency conversion circuit) 7 as an average value V4 of the power supply voltage. As shown in FIG. 4, the VFO 7 outputs the oscillation signal of a higher frequency than the rated time based on the average value V4 of the power supply voltage to the PWM (pulse width control circuit).
13, and the FET driver 14 drives the switching circuit (the charge side SW circuit 21 and the discharge side SW circuit 22) at the operating frequency based on the high frequency oscillation signal from the PWM 13. As a result, as shown in FIG. 3, the output power of the inverter circuit 18 (the inductor T1
It is possible to supply the discharge lamp (load) 49 with a constant output voltage that does not exceed the rating.

When an input voltage lower than the rating is supplied to the inverter circuit 18, it is the unsmoothed DC voltage of the rectifier circuit 15 smoothed by the smoothing circuit 10 constituting the power supply voltage detection circuit 8. A power supply voltage value that does not reach the rating is supplied to a VFO (voltage / frequency conversion circuit) 7 as an average power supply voltage value V4, and the VFO 7 is rated based on the average power supply voltage value V4 as shown in FIG. An oscillation signal of a lower frequency than the time is supplied to the PWM (pulse width control circuit) 13, and the FET driver 14 operates at an operating frequency based on the low frequency oscillation signal from the PWM 13 to switch the switching circuit (the charge side SW circuit 21 and the discharge side SW). Drive circuit 22). As a result, as shown in FIG. 3, the output power of the inverter circuit 18 (the inductor T1
The discharge lamp (load) 49 can be supplied with a constant output voltage which does not fall below the rated value.

As described above, according to the embodiment of the present invention, a constant high frequency voltage can always be output even if the power supply voltage supplied from the commercial AC power supply 16 fluctuates for some reason. it can.

Next, a third embodiment of the present invention will be described. FIG. 6 is a circuit diagram showing a third embodiment of the present invention. In the embodiment of the present invention, the power supply voltage input to the device is obtained by detecting the average value of the voltage generated at the connection point of the large-capacity capacitors C3 and C5, and from this voltage average value, The present invention relates to a device that compensates for power supply voltage fluctuations.

In FIG. 6, the same parts as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. Also, the description of the components other than the essential parts of the invention is omitted.

The power supply voltage detection circuit 8 which is a main part in FIG. 6 is composed of only a smoothing circuit 10 having a time constant capable of sufficiently smoothing the supplied power supply voltage. The smoothing circuit 10 has a resistor R8. , R9, and capacitor C
It is composed of 8.

The connection point between the large-capacity capacitors C3 and C5 forming the inverter circuit 18 is a parallel circuit including the resistor R8 forming the smoothing circuit 10 and the capacitors C8 and R9 connected in series to the resistor R8. Is connected to the reference potential point via. Further, the average value V4 of the power supply voltage generated at the connection point of the large-capacity capacitor C3 and the capacitor C5 is V from the connection point of the resistor R8 and the parallel circuit composed of the capacitor C8 and the resistor R9.
It is configured to be supplied to an FO (voltage / frequency conversion circuit) 7.

Next, the operation will be described. When the power supply voltage supplied from the commercial AC power supply 16 fluctuates for some reason and, for example, an input voltage exceeding the rating is supplied to the inverter circuit 18, the large-capacity capacitor C3 and the capacitor C5 are connected. The voltage generated at the point exceeds a predetermined reference value (rating), and the power supply voltage value smoothed by the smoothing circuit 10 is VF as the average value V4 of the power supply voltage.
It is supplied to O (voltage / frequency conversion circuit) 7. VFO7
Is the average value V4 of this power supply voltage, as shown in FIG.
Based on the
(Pulse width control circuit) 13 to supply the FET driver 1
Reference numeral 4 drives the switching circuit (charge side SW circuit 21 and discharge side SW circuit 22) at an operating frequency based on the high frequency oscillation signal from the PWM 13. As a result, as shown in FIG. 3, the output power of the inverter circuit 18 (taken from the inductor T1) is reduced, and a constant output voltage that does not exceed the rating is supplied to the discharge lamp (load) 49. be able to.

When a lower rated input voltage is supplied to the inverter circuit 18, the predetermined reference value (rating) that occurs at the connection point between the large-capacity capacitors C3 and C5 is not reached. The power supply voltage value smoothed by the smoothing circuit 10 is the average value V4 of the power supply voltage,
The VFO (voltage / frequency conversion circuit) 7 is supplied with the VFO.
7 is the average value V4 of this power supply voltage as shown in FIG.
Based on the
(Pulse width control circuit) 13 supplied, FET driver 14
Drives the switching circuit (charge side SW circuit 21 and discharge side SW circuit 22) at an operating frequency based on the low frequency oscillation signal from the PWM 13. This allows
As shown in FIG. 3, the output power of the inverter circuit 18 (taken out from the inductor T1) increases, and a constant output voltage that does not fall below the rated value can be supplied to the discharge lamp (load) 49. .

As described above, according to the embodiment of the present invention, even if the power supply voltage supplied from the commercial AC power supply 16 fluctuates for some reason, a constant high frequency voltage can always be output. it can.

Next, a fourth embodiment of the present invention will be described. FIG. 7 is a circuit diagram showing a fourth embodiment of the present invention. In the embodiment of the present invention, the Isw detection circuit 11 for detecting the current provided between the charging side SW circuit 21 and the capacitor C5 is used as the power source voltage input to the device. C5
The present invention relates to a device that detects a current flowing between the two, obtains a peak value of the detected current by detecting it with an Isw (peak) detection circuit 12, and compensates the power supply voltage fluctuation from the peak value.

In FIG. 7, the same parts as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. Also, the description of the components other than the essential parts of the invention is omitted.

The power supply voltage detection circuit 8 which is a main part in FIG. 7 includes an Isw detection circuit 11 for detecting a current and an Isw (peak) detection circuit 1 for detecting a peak value of the input current.
And an Isw detection circuit 11 configured to detect a current provided on the drain side of the charging side SW circuit 21.
Is detected by the Isw (peak) detection circuit 1
2, the peak value is detected, and the peak value (voltage) is supplied to the VFO (voltage / frequency conversion circuit) 7. The Isw detection circuit 11 is composed of, for example, a current transformer or a photo coupler, and the Isw (peak) detection circuit 12 is composed of, for example, a resistor and a diode. The Isw detection circuit 1
1 may be provided on the source side of the charging side SW circuit 21.

By the way, the circuit shown in FIG.
Using the switching circuit described above, high frequency voltage
In the device that outputs the input current with low distortion, as described above, when the operating frequency (switching frequency) of the switching circuits (the charge side SW circuit 21 and the discharge side SW circuit 22) is increased as shown in FIG. It generally has a characteristic that the high-frequency output voltage (power) decreases (there may be the opposite depending on the circuit configuration). Therefore, the circuit according to the embodiment of the present invention has a similar tendency, and the relationship between the detected value of the Isw (peak) detection circuit 12 and the operating frequency is as shown in FIG. By the same processing as that of the embodiment described above, it is possible to compensate for the power supply voltage fluctuation when the power supply voltage fluctuates for some reason. FIG. 8 is a characteristic diagram showing an example of the relationship between the operating frequency (switching frequency) and the detection value of the Isw (peak) detection circuit 12.

The compensation operation of the power supply voltage fluctuation in the embodiment of the present invention will be described below. If the power supply voltage supplied from the commercial AC power supply 16 fluctuates for some reason, and an input voltage exceeding the rating is supplied to the inverter circuit 18, the Isw (peak) detection circuit 12 sets a predetermined value. The peak value (voltage) that exceeds the reference value (rating) of is detected, and the peak value (voltage) is VFO (voltage / frequency conversion circuit) as the average value V4 of the power supply voltage.
7 is supplied. The VFO 7 is, as shown in FIG.
An oscillation signal having a higher frequency than the rated time based on the average value V4 of the power supply voltage is supplied to the PWM (pulse width control circuit) 13, and the FET driver 14 switches at the operating frequency based on the high frequency oscillation signal from the PWM 13. The circuits (charge side SW circuit 21 and discharge side SW circuit 22) are driven. As a result, as shown in FIG. 3, the output power of the inverter circuit 18 (taken from the inductor T1) is reduced, and a constant output voltage that does not exceed the rating is supplied to the discharge lamp (load) 49. can do.

When an input voltage lower than the rated value is supplied to the inverter circuit 18, the Isw (peak)
The detection circuit 12 detects a peak value (voltage) that does not reach a predetermined reference value (rating), and the peak value (voltage) is VFO (voltage / frequency conversion circuit) as an average value V4 of the power supply voltage.
7, the VFO 7 supplies the PWM (pulse width control circuit) 13 with an oscillation signal of a frequency lower than that at the rated time based on the average value V4 of the power supply voltage, as shown in FIG.
The FET driver 14 drives the switching circuit (charge side SW circuit 21 and discharge side SW circuit 22) at an operating frequency based on the low frequency oscillation signal from the PWM 13. As a result, as shown in FIG. 3, the output power of the inverter circuit 18 (taken out from the inductor T1) increases, and a constant output voltage that does not drop below the rated value is supplied to the discharge lamp (load) 49. It

As described above, according to the embodiment of the present invention, even if the power supply voltage supplied from the commercial AC power supply 16 fluctuates for some reason, a constant high frequency voltage can always be output. it can.

FIG. 9 is a circuit diagram showing another example of the configuration of the power supply voltage detection circuit 8, which is the characteristic opposite to the operating frequency (switching frequency) and output voltage (power) characteristics shown in FIG. That is, the switching circuit (the charge side and the discharge side SW
Operating frequency of circuits 21 and 22) (switching frequency)
Is effective in a device (inverter circuit) that outputs a high power factor of a high frequency voltage and a low distortion of an input current by using the switching circuit having the characteristic that the high frequency output voltage (electric power) decreases when the voltage is lowered.

Next, a fifth embodiment of the present invention will be described. FIG. 10 is a circuit diagram showing a fifth embodiment of the present invention. FIG. 11 is a diagram showing operation waveforms of the circuit according to the fifth embodiment of the present invention. still,
In the embodiment of the present invention, the power supply voltage input to the device is
For example, the present invention relates to a device for protecting an inverter circuit or the like from being damaged when the input exceeds a predetermined reference value (rating).

The circuit shown in FIG. 10 includes a commercial AC power supply 16 for supplying a predetermined power supply voltage to the device, a rectifier circuit 24, an overvoltage detection circuit 25, a comparator 26, a charging side SW circuit 28 which is a second switching circuit, and a second switching circuit. The discharge side SW circuit 29 which is one switching circuit, the switching control circuit 27 which controls the switching of the charge side SW circuit 28 and the discharge side SW circuit 29, the large capacity capacitor C3 which is the first capacitor, and the second capacitor A small-capacity capacitor C5, inductor T1, primary winding L of inductor T1
1, and a discharge lamp 49.

Further, the commercial AC power source 16 has a rectifier circuit 24.
Is connected to the rectifier circuit 24, and the rectifier circuit 24 is composed of a diode having a high-speed switching characteristic, for example.
A second switching circuit 28 (for example, the drain of a MOSFET) is connected to the positive terminal of the output terminal of the rectifier circuit 24, and a first switching circuit 29 (for example the MOSFET) is connected to the negative terminal of the output terminal of the rectifier circuit 24. Source) of the first switching circuit 29
And the second switching circuit 28 are connected in series. The switching circuits 28 and 29 are composed of MOSFETs (field effect transistors) or the like as described above, and the parasitic diodes of the respective elements are used as diodes for reverse current flow.

[0082] Further, in parallel with the first switching circuit 29, the series circuit comprising the primary winding L1 of the leakage type transformer T1 first capacitor C3 Metropolitan is connected. The first capacitor C3 has a smoothing effect on the output frequency of the rectifier circuit 24. A fluorescent lamp (discharge lamp) 49 is connected to the secondary winding L2 of the leakage transformer T1.
A condenser C2 for preheating the filament is connected between the filaments of both electrodes. The leakage inductance of the leakage type transformer T1 also acts as a current limiting impedance of the fluorescent lamp 49.

Further, in series with the second switching circuit 28, a series circuit composed of the primary winding L1 of the leakage transformer T1 and the second capacitor C5 is connected. The capacity of the second capacitor C5 is extremely smaller than that of the first capacitor C3, and is set to a value that resonates at the switching frequencies of the switching circuits 28 and 29 together with the leakage inductance of the leakage transformer T1.

On the other hand, the switching control circuit 27 controls ON / OFF of the switching circuits 28 and 29. The switching control circuit 27 outputs the switching circuits 28 and 29 to the output of the rectifying circuit 24 which is substantially constant. ON / OFF control at a frequency higher than the frequency, AC power supply 16
The ON period of the first switching circuit 29 is controlled according to the magnitude of the peak value of the output voltage (output voltage of the rectifier circuit 24) of FIG. That is, control is performed so that the ON period of the first switching circuit 28 is long during the period when the peak value of the output voltage of the rectifier circuit 24 is large, and the ON period is shortened during the period when the peak value is small. Has become. The ON period of the second switching circuit 28 is controlled so as to have an inverse relationship to that of the first switching circuit 29 as shown in FIG.

An overvoltage detection circuit 25 is connected in parallel with the non-smoothed DC voltage output terminal of the rectifier circuit 24, the output terminal of which is connected to the non-inverting terminal (+) of the comparator 26, and the comparator 26 The inverting terminal (-) of is connected to the constant voltage supply source E2, and the output terminal of the comparator 26 is connected to the switching control circuit 27.

Next, the operation will be described. The operation of this circuit in the normal state has already been described, and the description thereof will be omitted. The current from the power supply of this circuit is the rectifier circuit 24 → the second switching circuit 28 → the primary side winding L1 of the leakage transformer T1 → the first capacitor C.
3 → Flows in the route of the rectifier circuit 24. It should be noted that the overvoltage detection circuit 25 is provided at a place where it is possible to quickly detect that an overvoltage is applied to the AC current supplied from the AC power supply 16.
It may be arranged in the very this.

When an overvoltage is applied from the AC power supply 16,
This current flows through the above-mentioned path and damages, for example, the discharge lamp (load) 49 on the secondary side of the leakage transformer T1. Therefore, if overvoltage application is detected,
The circuit can be protected by cutting off the overcurrent flow route. The compensation operation (control) at the time of overvoltage application in the embodiment of the present invention will be described below.

Now, assuming that an overvoltage is applied from the AC power supply 16, the overvoltage detection circuit 25 detects it and outputs the detected voltage value to the non-inverting terminal (+) of the comparator 26, for example. On the other hand, the comparator 26 has the non-inverting terminal (+)
The voltage value (overvoltage) input to the constant voltage supply source E2 (reference value) input to the inverting terminal (-) is compared. When the voltage value exceeds the reference value, the comparator 26 outputs the protection signal p3 from its output terminal to the switching control circuit 27. The switching control circuit 27 which receives the protection signal p3 controls the second switching circuit 28 to open (turn off) the circuit. As a result, it is possible to prevent an overcurrent flowing from the AC power supply 16 from flowing through the current distribution route, and protect the circuit (for example, the discharge lamp (load) 49 on the secondary side of the leakage transformer T1). it can.

By the way, in order to prevent the overcurrent flowing from the AC power supply 16 from flowing through the current flow route, the following three timings are used to turn off the operation of the second switching circuit 28. be able to. The timing of the control operation (turn-off control) of the switching control circuit 27 for shutting off (blocking) the overcurrent with respect to the second switching circuit 28 will be described below with reference to FIG. 11.

In the control method shown in FIG. 11A, the output of the overvoltage detection circuit 25 determines the control operation (turn-off control) period of the switching control circuit 27 for the second switching circuit 28 by the constant voltage supply source E2. This is a case where it is the same as the period in which the reference level is exceeded (set period A). That is, as described above, the second switching circuit 28 is the first switching circuit 2
9 and alternately control the on / off so that the divided line, during which the output of the overvoltage detecting circuit 25 between (turn-off control period of the setting period A exceeds the reference level
And those) is one that is not performed on the control of the second switching circuit 28.

Next, a control method shown in FIG. 11B is used, in which a control operation (turn-off control) period of the switching control circuit 27 for the second switching circuit 28 is performed when the output of the overvoltage detection circuit 25 is Constant voltage supply E
2 shows a case (setting period B) in which the period exceeding the reference level determined by 2 and the period after the end (after the period elapses) until the elapse of a predetermined time are added (set period B). That is, (which was during the period in which the output is combined adding a duration and a predetermined period after the period end exceeds the reference level of the overvoltage detection circuit 25 turn-off control period) during the setting period B the second The ON control of the switching circuit 28 is not performed. Finally, the control method shown in FIG. 11C is used, in which the control operation (turn-off control) period of the switching control circuit 27 for the second switching circuit 28 is the constant voltage when the output of the overvoltage detection circuit 25 is constant. When the period from the start of the period exceeding the reference level determined by the supply source E2 to the end thereof, or the period from the start of the period to the elapse of a predetermined time, whichever is longer (setting period C), It is shown. That is, during the set period C (the period during which the turn-off control period is set to be equal to or less than the period in which the output of the overvoltage detection circuit 25 exceeds the reference level or is exceeded).
The ON control of the second switching circuit 28 is not performed during a period when a predetermined time has elapsed from the current period . The second switching circuit 28 is turned on in the set periods A, B, and C of the turn-off control shown in (a), (b), and (c) of FIG. Is on for a short period of time)
After the switching circuit 28 is turned on, a slight delay occurs in the response before the turn-off control is actually performed after determining whether the output of the overvoltage detection circuit 25 exceeds the reference level. Is.

As described above, according to the embodiment of the present invention, even if the power supply voltage supplied from the commercial AC power supply 16 fluctuates for some reason and an overvoltage occurs, the current flowing through the circuit in the normal state. The route of, that is,
The second switching circuit 28 is turned off through the passage of the current flowing from the rectifier circuit 24 to the second switching circuit 28, to the primary winding L1 of the leakage transformer T1, to the first capacitor C3 to the rectifier circuit 24 (ON. This device (circuit) can be protected from overvoltage by disconnecting the device (circuit).

[0093]

In a device that uses a switching circuit to output a high-frequency voltage with a high power factor and an input current with a low distortion, generally, the operating frequency (switching) of the switching circuit (two SW circuits on the charging side and the discharging side) is used. When the frequency is increased, the high frequency output voltage (power) is lowered. Therefore, in the invention described in claims 1 to 8, by utilizing this characteristic, when the power supply voltage supplied from the commercial AC power supply fluctuates for some reason and the input voltage exceeding the rating is supplied, Detecting it, VFO
(Voltage / frequency conversion circuit) and supplies this average voltage value V
The oscillation signal of a frequency higher than that at the time of rating according to 4 is applied to the VFO
To control the FET driver by driving the switching circuit at an operating frequency based on the high-frequency oscillation signal, so that the high-frequency voltage has a high power factor and an input current. It is possible to supply a constant output voltage (electric power) that does not exceed the rating to the discharge lamp (load) by reducing the output power of the device that outputs with low distortion.

When the power supply voltage supplied from the commercial AC power supply fluctuates for some reason and an input voltage lower than the rated voltage is supplied, the average voltage value is detected and VFO (voltage / voltage / Frequency converter circuit), and controls the FET driver by supplying an oscillation signal of a frequency lower than that at the time of rating from the VFO to the PWM (pulse width control circuit) according to the average voltage value. Since the switching circuit is driven at the operating frequency based on the oscillation signal, the high frequency voltage can be set to a high power factor,
It is possible to supply a constant output voltage (power) that does not fall below the rating to the discharge lamp (load) by increasing the output power of the device that outputs the input current with low distortion.

As described above, even if the power supply voltage supplied from the commercial AC power supply fluctuates for some reason, a constant high frequency voltage can be output.

On the other hand, according to the invention described in claims 9 to 15, when an overcurrent is applied from the commercial AC power supply, the overvoltage detection circuit detects it and outputs the detected voltage value to the comparator. Then, in the comparator, the voltage value is the switching circuit (two SW circuits on the charging side and the discharging side).
When it is determined that the overvoltage is present at the current operating frequency (switching frequency), the comparator outputs a protection signal to the switching control circuit to control the switching control circuit and opens (turns off) the second switching circuit. Since the operation to perform is performed by a device (circuit) that outputs the high-frequency voltage with a high power factor and low-distortion input current, the overcurrent flowing from the commercial AC power source is the high-frequency voltage in a steady state. Can be prevented from flowing into the route of the current flowing through the device (circuit) that outputs a high power factor and a low distortion of the input current, and protects the discharge lamp (load) on the secondary side of the leakage transformer, for example. can do.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention.

FIG. 2 is an output voltage of a rectifier circuit 15 and a charge side SW circuit 2
5 is a timing chart showing the relationship between the ON times of the discharge circuit 1 and the discharge side SW circuit 22.

FIG. 3 is a characteristic diagram showing an example of a relationship between an operating frequency (switching frequency) and an output voltage (power).

FIG. 4 is a characteristic diagram showing an example of the relationship between the smoothed output voltage output by the power supply voltage detection circuit 8 and the oscillation frequency (operating frequency) of the VFO 7.

FIG. 5 is a circuit diagram showing a second embodiment of the present invention.

FIG. 6 is a circuit diagram showing a third embodiment of the present invention.

FIG. 7 is a circuit diagram showing a fourth embodiment of the present invention.

FIG. 8: Operating frequency (switching frequency) and Isw
FIG. 6 is a characteristic diagram showing an example of a relationship between detection values of a (peak) detection circuit 12.

FIG. 9 is a circuit diagram showing another configuration example of the power supply voltage detection circuit 8.

FIG. 10 is a circuit diagram showing a fifth embodiment of the present invention.

FIG. 11 is a diagram showing operation waveforms of the circuit according to the fifth embodiment of the present invention.

FIG. 12 is a circuit diagram showing an example of a prior art of the present invention.

FIG. 13 is a diagram showing a change state of ON periods of the first and second switching circuits 45 and 46 with respect to the output voltage of the rectifier 44.

FIG. 14 is a diagram in which only a main part necessary for explanation is simplified in a circuit diagram showing an example of a prior art.

FIG. 15 is a diagram showing voltage and current waveforms at various parts.

FIG. 16 shows voltage and current waveforms at various parts.

FIG. 17 is a diagram showing an input current, a voltage between output terminals, and a load current waveform of the rectifier circuit 44 corresponding to an output frequency of the rectifier circuit 44.

[Explanation of Codes] 4 ... Isw detection circuit 5 ... Isw (peak) detection circuit 6 ... Error amplifier 7 ... VFO (voltage / frequency conversion circuit) 8 ... Power supply voltage detection circuits 9a, 9b ... Low speed power supply rectifying diode 10 ... Smoothing Circuit 13 ... PWM (pulse width control circuit) 14 ... FET driver 15 ... Rectifier circuit 16 ... Commercial AC power supply 17 ... Line filter 18 ... Inverter circuit 21 ... Charge side SW circuit (second switching circuit) 22 ... Discharge side SW circuit (First switching circuit) 23 ... Output control circuit 31 ... On-duty variable circuit 49 ... Load (discharge lamp) R1 to R4 ... Resistors C1, C2, C4 ... Capacitor C3 ... First capacitor (relatively large capacity) C5 ... Second capacitor (relatively small capacity) T1 ... Leakage type transformer E1 ... DC constant voltage source

Front page continuation (72) Keiichi Shimizu Inventor Keiichi Shimizu 4-3-1, Higashishinagawa, Shinagawa-ku, Tokyo Inside Toshiba Lighting & Technology Corporation (56) Reference JP-A-8-103081 (JP, A) JP-A-6- 311753 (JP, A) JP 5-182783 (JP, A) JP 8-103082 (JP, A) JP 7-73983 (JP, A) JP 8-78174 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) H02M 7/48 H02J 1/00 H02M 7/5387 H05B 41/24

Claims (15)

(57) [Claims] 1. A rectifier circuit for rectifying an AC power supply voltage to output an unsmoothed DC voltage; a rectifier circuit connected in parallel between output terminals of the rectifier circuit, and alternately turned on / off to output a frequency higher than the output frequency of the rectifier circuit; First and second switching circuits connected in series that switch at a high frequency; and provided in parallel to the first switching circuit,
While being charged by the output of the rectifier circuit via the second switching circuit during the ON period of the second switching circuit, smoothing processing is performed on the output frequency of the rectifier circuit, A relatively large-capacity first capacitor that discharges the charged electric charge through the first switching circuit during an ON period; and a connection point between the first and second switching circuits and the first capacitor An inductor for passing a charging / discharging current of the first capacitor; and a relatively small-capacity second inductor that resonates with the inductor in response to ON / OFF of the first and second switching circuits. A capacitor; a current detection circuit that detects a current flowing through the first switching circuit; and the first switch based on a detection signal of the current detection circuit An on-duty variable circuit for controlling an ON period of a switching circuit; a power supply voltage detection circuit that detects a change in the AC power supply voltage and outputs a detection signal; a first and a second output circuit based on a detection signal from the power supply voltage detection circuit A power supply device comprising: an output control circuit that changes a switching frequency of a second switching circuit; and an output circuit that obtains a high frequency output by resonance of the inductor and the second capacitor. 2. The power supply voltage detection circuit detects the power supply voltage fluctuation by detecting a voltage generated across the first capacitor having a relatively large capacity. 1. The power supply device according to 1. 3. The power supply voltage detection circuit detects the fluctuation of the power supply voltage based on a current flowing through the second switching circuit connected in a path for charging the relatively large-capacity first capacitor. The power supply device according to claim 1, which is performed by detecting a peak value. 4. The output control circuit, when an increase in the power supply voltage is detected by a detection signal from the power supply voltage detection circuit, the first and second switching circuits according to the degree of the increase. And the switching frequency of the first and second switching circuits is decreased according to the degree of the decrease when the decrease of the power supply voltage is detected by the detection signal from the power supply voltage detection circuit. The power supply device according to claim 1, wherein the power supply device is controlled as described above. 5. The output control circuit comprises an oscillator capable of changing an oscillation frequency based on a detection signal from the power supply voltage detection circuit for detecting a power supply voltage, and the first control circuit according to the oscillation frequency of the oscillator. The power supply device according to claim 1, wherein the switching frequency of the second switching circuit is changed. 6. The output control circuit, when an increase in the power supply voltage is detected by a detection signal from the power supply voltage detection circuit, increases the oscillation frequency of the oscillator according to the degree of increase, 6. The oscillation frequency of the oscillator is controlled to be lowered according to the degree of the decrease when the decrease of the power supply voltage is detected by the detection signal from the power supply voltage detection circuit. Power supply. 7. A rectifier circuit for rectifying an AC voltage to output a non-smoothed DC voltage; a rectifier circuit connected in parallel between output terminals of the rectifier circuit, and alternately turned on / off to output a frequency higher than the output frequency of the rectifier circuit. First and second switching circuits connected in series that switch at a high frequency; provided in parallel with the first switching circuit, and the second switching circuit during an ON period of the second switching circuit Is charged by the output of the rectifier circuit via the smoothing process for the output frequency of the rectifier circuit, and the charge is discharged through the first switching circuit during the ON period of the first switching circuit. A large-capacity first capacitor; provided between the connection point of the first and second switching circuits and the first capacitor, and the first capacitor An inductor for flowing the charging / discharging current; a second capacitor having a relatively small capacity that resonates with the inductor according to ON / OFF of the first and second switching circuits; and an output terminal of the rectifier circuit. An overvoltage detection circuit connected in parallel with the rectifier circuit for detecting that an overvoltage is applied to the unsmoothed DC voltage between; a voltage value output from the overvoltage detection circuit and a predetermined reference value level; A comparator circuit that outputs a protection signal when the voltage value output from the overvoltage detection circuit exceeds the reference value level; and the second circuit when the protection signal is input.
And a switching control circuit for turning off the operation of the switching circuit. 8. The first switching circuit and the first capacitor are connected to a low potential side of the circuit, and the second switching circuit and the first capacitor are connected to each other.
8. The switching circuit of claim 2 and the second capacitor are connected to the high potential side of the circuit.
The power supply device according to. 9. The turn-off control in the second switching circuit is performed only during a period in which the voltage value output from the overvoltage detection circuit exceeds the reference value level. The power supply device according to item 8. 10. The turn-off control in the second switching circuit is performed for a period from when the voltage value output from the overvoltage detection circuit exceeds the reference value level until a predetermined time elapses. Claim 7 characterized by
Alternatively, the power supply device according to item 8. 11. The turn-off control in the second switching circuit is a period from a start of a period when a voltage value output from the overvoltage detection circuit exceeds the reference value level to an end of the period, or the period. and wherein the dividing lines to any long period of time from the start until after a predetermined time has elapsed, the power supply device according to claim 7 or 8. 12. The power supply device according to claim 7, wherein the first and second switching circuits are duty-controlled under a constant switching frequency. 13. The power supply device according to claim 7, wherein each of the first and second switching circuits has an on-time controlled. 14. A discharge lamp lighting device, comprising: the power supply device according to claim 1; and a discharge lamp that is energized by an output of the power supply device. 15. A lighting device, comprising: a lighting device main body; and the discharge lamp lighting device according to claim 14.