JP2003317979A - Power supply circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply circuit which is used in a signal lamp using an LED, is normally operated even in winder or summer seasons, and in which a luminous source rapidly emits light after supplying power. <P>SOLUTION: An alternating current AC is rectified in a rectifier 100. An error amplifier 204 is provided in the inner part of an integrated circuit IC1. A reference voltage Vref and an output voltage of an output voltage detector 300 are inputted in the error amplifier 204. The output voltage V0 is detected by a detecting voltage Vfb, and the error amplifier 204 amplifies and outputs an error amount, comparing the reference voltage Vref and the detecting voltage Vfb. In such a control operation, the Vfb approaches to the Vref unlimitedly, and V0 determined in the Vref is obtained. A temperature detector comprises a diode D4 and a thermistor R10. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply circuit used for a signal lamp using an LED (light emitting diode).

[0002]

2. Description of the Related Art Recently, attempts have been made to use a signal light using an LED for a traffic signal. LEDs can obtain various colors, have higher luminous efficiency than incandescent bulbs, and are excellent in energy saving as a light source of lighting equipment.

[0003]

By the way, in order to use the LED light source as a light source of a traffic light or a general lighting fixture safely and with a long life indoors or outdoors, a wide environmental temperature change from winter to summer is considered in advance. Then need to use.

For example, in a signal light using an LED, at a subzero temperature in winter, a rapid heat generation occurs around the light emitting portion in the LED at the time of lighting, and the internal substances constituting the LED cause thermal expansion. When the LED is in a low temperature state, the structure of the entire LED is in a contracted state, so that the internal expansion generated at the time of lighting causes mechanical stress between the inside and the outside of the LED structure.

Therefore, the repetition of lighting and extinction results in a severe usage condition, which may lead to destruction of the LED depending on the conditions. For this reason, in order to obtain the required amount of light emission and alleviate the above phenomenon, it is necessary to use a method of energizing a current amount suitable for various temperatures in consideration of the temperature characteristics of the LED.

Further, the following points must be taken into consideration at high temperatures in summer. LED manufacturers have indicated various absolute ratings for use. According to this,
At high temperatures where the ambient temperature of the LED exceeds the room temperature, a current amount that is less than the current amount allowed at the room temperature is allowed.

That is, in actual use, when the ambient temperature of the LED is higher than about 40 ° C., in order to avoid thermal breakage such as fusing due to temperature rise of internal substances constituting the LED, electricity is applied. The amount of current applied must be reduced from that at room temperature. In this case as well, it is necessary to obtain a required amount of light emission and satisfy a current amount equal to or less than various allowable current values at various high temperatures. Further, the signal lamp using the LED has a problem that it takes some time from power input to lighting. The present invention has been made in view of such demands and problems, and an object thereof is to be used for a signal light or the like using an LED, and the LED operates normally even in a severe cold season or the summer, and the power is turned on. After that, it is to provide a power supply circuit in which an LED emits light promptly.

[0008]

In order to achieve the above object, the present invention provides a rectifying section for rectifying an AC power source, a stabilized power supply circuit section for extracting a constant voltage from a voltage rectified by the rectifying section, A light emitting diode driven by the output voltage of the stabilized power supply circuit section, wherein the stabilized power supply circuit has a start assist circuit that accelerates the rising at the start.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a power supply circuit according to an embodiment of the present invention.
The power supply circuit 1 includes a rectification unit 100 and a stabilized power supply circuit unit 20.
0, an output voltage detection unit 300, and a light source unit 400.

The rectifying section 100 rectifies the AC voltage. The stabilized power supply circuit unit 200 includes a reference voltage and output voltage detection unit 3
The output voltage of the transformer is compared with the output voltage of 00, the control signal is obtained, and the current switched by the signal corresponding to the control signal amount is input to the transformer, and the output of the transformer is supplied to the light source unit 400 and the output voltage detection unit 300. Sent.

The output voltage detection unit 300 includes a temperature detection unit to detect the external temperature, and considers the external temperature with respect to the output voltage from the stabilized power supply circuit unit 200, and the temperature of the light emitting diode of the light source unit 400. A signal suitable for the characteristic is generated and fed back to the stabilized power supply circuit unit 200. The light source unit 400 includes a large number of LEDs and emits light according to the voltage output from the stabilized power supply circuit unit 200.

2, 3, and 4, the rectifying section 100, the stabilizing power supply circuit section 200, the output voltage detecting section 300, and the light source section 4 are shown.
00 is a circuit diagram showing a specific configuration of 00. Rectifier 100
Then, AC is applied between the terminals 104 and 106.
R1 is a circuit protection resistor, ZNR1 is a surge absorber, and C1 is a noise absorbing capacitor.
AC line filter L1 in the noise absorbing capacitor C1
Is connected, and the noise absorbing capacitor C2 is connected to the AC line filter L1.

D1 is a bridge diode for rectifying an AC voltage into a DC voltage, and C3 is a capacitor for absorbing high frequency noise and ripple voltage after rectification.
Next, the stabilized power supply circuit unit 200 will be described with reference to FIG. The stabilized power supply circuit unit 200 includes a resistor R2,
R3, R4, R5, R6, R7, capacitors C4, C
5, C6, C7, C8, transformer L2, diode D2,
D3, integrated circuit IC1, MOS-FET (Q1) and the like. The start assist circuit 202 is composed of the capacitor C7 and the resistor R5.

The resistors R2 and R3 are resistors as a voltage supply circuit for operating the built-in multiplier of the integrated circuit IC1.
The capacitor C4 absorbs noise. Capacitor C5
Compensates the phase of the integrated circuit IC1.

The resistor R4 serves to reduce the voltage drop as well as the integrated circuit I.
It is a resistor for supplying the operating voltage of C1. Capacitor C6
Is a smoothing capacitor for absorbing ripple voltage. The resistor R5 is connected to the points 204 to 206 immediately after the AC power is turned on.
At, the current value for rapidly assisting charging into the capacitor C6 is limited to an appropriate value, and at the steady state, points 204 and 2
Proper impedance is provided between 06. Capacitor C
The differential operation 7 rapidly charges the capacitor C6 immediately after the AC power is turned on, and accelerates the operation of the integrated circuit IC1.

The transformer L2 is composed of primary coils L2-1 and L2-1.
It has secondary coils L2-2 and L2-3. Diode D
2 is a transformer L2 during steady switching operation.
AC generated from the secondary side coil L2-2 is rectified and a DC power supply voltage is supplied to the integrated circuit IC1.
Block backflow from 06.

The resistor R6 is a resistor for the zero current detection circuit for the integrated circuit IC1. MOS-FET (Q1) is
Switching control is performed by turning on and off the current flowing through the primary coil L2-1 of the transformer L2. The resistor R7 is a transformer L
The current flowing through the primary winding L2-1 of No. 2 is detected. The diode D3 AC-rectifies the output of the secondary winding L2-3 of the transformer L2. The capacitor C8 is a smoothing capacitor.

Next, referring to FIG. 4, the output voltage detector 30 will be described.
0 and the light source unit 400 will be described. The output voltage detector 300 has a light emitting diode D4, a thermistor R10, a resistor R8, and a resistor R9. The thermistor R10 and the light emitting diode D4 constitute a temperature detecting section, and the outside temperature is detected. The light emitting diode D4 is a light emitting part LED.
The same type of light emitting diode as the 402, and the light source unit LE
It is an LED for temperature detection mainly used for correcting the low temperature characteristic of D402.

The thermistor R10 is a light source section LED402.
Is a temperature detection resistor mainly used for correction of high temperature characteristics. The light source unit 400 has a light source unit LED 402.
The light source unit LED 402 includes the stabilized power supply circuit unit 200.
It emits light according to the output voltage of.

Next, an outline of the operation of the power supply circuit 1 will be described. The rectification unit 100 rectifies AC AC to obtain rough DC including ripple. This rough direct current is supplied as a power source for all circuits. In the stabilized power supply circuit unit 200, the integrated circuit IC
1 has a reference voltage built therein, and compares the reference voltage value with the detection voltage from the output voltage detection unit 300 and performs error amplification to obtain a control signal.

A current corresponding to the control signal is passed through the primary side coil L2-1 of the transformer L2 by switching the MOS-FET (Q1) to the secondary side coil L2-3 of the transformer L2.
Then, an AC voltage is generated. The AC voltage of the secondary coil L2-3 is rectified by the diode D3, smoothed by the capacitor C8, and becomes a DC output voltage.

The output voltage detecting section 300 includes a temperature detecting section, and is required for the light source section LED 400 under a wide environmental temperature change from winter to summer in consideration of respective temperature characteristics unique to LEDs of various emission colors. It is a circuit for controlling so as to secure the function. The light source unit 400 has a large number of light source unit LEDs 402 in order to have a function suitable for the amount of light required as a light source and the purpose of use.

Next, the output voltage detector 300 and the start assist circuit 202, which are the features of the present invention, will be described in more detail. FIG. 5 is a schematic configuration diagram of the power supply circuit 1 when the stabilized power supply circuit unit 200 is schematically drawn. The stabilized power supply circuit unit 200 operates with the coarse DC voltage obtained by rectifying the AC AC by the rectification unit 100 as a power source. An error amplifier 204 is provided inside the integrated circuit IC1. The reference voltage Vref and the output voltage Vfb of the output voltage detection unit 300 are input to the error amplifier 204.

The output voltage V0 is detected by the detection voltage Vfb,
The error amplification unit 204 has a reference voltage Vref and a detection voltage Vref.
It is compared with fb and the error is amplified and output. With this control operation, Vfb approaches Vref as much as possible, and Vr
V0 determined by ef is obtained.

Then, the output voltage V0 is expressed as follows. V0 = A (Vref−Vfb) (1) Here, A: gain Vref: reference voltage Vfb: output voltage V0 is divided, and a detection voltage R101 obtained by applying an operation suitable for the temperature characteristics of the LED is R9. Resistance value R102 is diode D4, thermistor R10, resistance R
8 combined resistance.

Since Vfb = R101V0 / (R101 + R102) (2), the equation (2) is substituted into the equation (1) and V0 = AVref-AR101V0 / ( R101
+ R102) (1 + A · R101 / (R101 + R102)) V0 =
A ・ Vref

Therefore, V0 = A.Vref / (1 + A.R101 / (R101
+ R102))

If A> 1, V0 is almost (R101 + R102) .Vref / R1.
01 ………… (3)

According to the equation (3), Vref is constant, and V0 is determined by (R101 + R102) / R101. Therefore, stability independent of the AC power supply voltage can be obtained.

In the present embodiment, the output voltage V0
In order to obtain a value in consideration of the temperature characteristics of the light source unit LED 402, R102 is provided with characteristics suitable for high temperature and low temperature.

First, the operation at a subzero temperature in winter will be described. In the output voltage detection unit 300, at a low temperature, the resistance value of the thermistor R10 increases, so that the current stops flowing and the current flows only in the light emitting diode D4.

In the light emitting diode D4, a substantially constant rising voltage is applied, but its temperature dependence can be positively utilized to cancel the temperature characteristic of the light source LED 402. As a temperature characteristic of the light source LED 400, there is a decrease in current due to an increase in rising voltage at a low temperature. As the temperature characteristic of the light emitting diode D4, the increase of the rising voltage at low temperature is used to lower the detection voltage, and the control operation
The output voltage is increased to increase the current of the light source LED400.

The built-in reference voltage Vr of the integrated circuit IC1
As a temperature characteristic of ef, there is an increase in current due to an increase in output voltage resulting from a control operation that occurs due to an increase in reference voltage Vref at a low temperature. As described above, the temperature characteristics of the light source LED 402, the temperature characteristics of the light emitting diode D4, and the integrated circuit IC
In combination with the temperature characteristic of the built-in reference voltage Vref of No. 1, the current value is reduced little by little from room temperature to low temperature, and the temperature dependence of the light emission amount is reduced.

Next, the operation under high temperature in summer will be described. In the thermistor R10 of the temperature detecting section and the light emitting diode D4, when the external temperature rises, the resistance value of the thermistor R10 decreases, so that a large amount of current flows in the thermistor R10, and the voltage value between both terminals of the thermistor R10 decreases. When the voltage becomes lower than the rising voltage, the light emitting diode D4 is not energized.

Therefore, as the temperature rises, the thermistor R1
The voltage decrease of 0 increases the detection voltage Vfb, and the integrated circuit IC
The temperature characteristic of the built-in reference voltage Vref of 1 is canceled and the output voltage V0 is reduced by the control operation, and the light source unit L at high temperature is reduced.
The current flowing through the ED 400 is set to the allowable current value or less.

FIGS. 10 to 15 are diagrams showing experimental results of fluctuations in the illuminance of the LED bulb when the temperature is changed, and FIGS. 10 and 11 show the case of the red LED bulb, and FIGS. 13 is a case of a yellow LED light bulb, and FIG.
FIG. 15 shows the case of a green LED light bulb. And FIG.
0, FIG. 12, and FIG. 14, the diode D4 and the thermistor R
It does not have a temperature detection unit consisting of 10.

For example, FIG. 10 shows a red LED in which the external temperature is changed.
The illuminance of the light bulb is measured, and the fluctuation rate of the illuminance is calculated based on the case where the temperature is 23 degrees. -40 degrees to 6
At 0 degrees, the fluctuations range from 150% to 65%,
In the case of FIG. 11, the fluctuation is about 80% to 102%,
It can be seen that there is little fluctuation. The same applies to FIGS. 12 to 15. Thus, according to the present embodiment, the LED light bulb operates properly even in winter and summer.

Next, the start assist circuit, which is the second feature of the present invention, will be described in detail. As shown in FIG. 3, in the stabilized power supply circuit 200, points 204 and 20 are provided.
A start assist circuit 202 including a capacitor C7 and a resistor R5 is provided between the start assist circuit 202 and the control circuit 6. With this start assist circuit 202, it is possible to shorten the delay time from immediately after the AC power supply is turned on to the power supply circuit 1 until the light source section 400 starts lighting.

First, the operation when the start assist circuit 202 does not exist will be described. Integrated circuit IC1
However, in order to start the functional operation, it is necessary to apply a voltage of approximately 12 V DC to the power supply connection terminal (8).

Immediately after the AC power is turned on, the integrated circuit IC1
The time change of the voltage supplied to the power supply connection terminal is as follows. From a DC power supply with a substantially constant voltage value at point 204,
Charging of the capacitor C6 is started through the resistor R4, and the DC voltage value thereof is almost zero from the resistor R4 and the capacitor C6.
It rises after a time constant time, which is the product of and. For this reason,
It takes time for the integrated circuit IC1 to reach the voltage value for starting the operation, and as a result, there is a time delay before the lighting of the light source unit LED 402 is started.

FIG. 6 shows an AC voltage 500 and an AC current 502 at point 102 (FIG. 2) without the start assist circuit.
Indicates. FIG. 8 shows the voltage 508 at the point 206 and the voltage 51 at the point 404 when the start assist circuit 202 does not exist.
Indicates 0.

Next, the operation when the start assist circuit 202 is present will be described. If the start assist circuit 202 is present, immediately after the AC power is turned on, the resistance R4 and the path of the start assist circuit 202, 2
Since the charging of the capacitor C6 starts via the route, the charging current increases as compared with the case where the start assist circuit 202 is not provided and the resistor R4 is used alone.

The start assist circuit 202 accelerates the charging of the capacitor C6 and the voltage supplied to the power supply connection terminal (8) of the integrated circuit IC1 increases rapidly, so that the IC operation starts earlier and, as a result, the light emitting section LED 400 lights up. The time to start is shortened.

This acceleration effect is performed by the charging current by the differential operation (phase advance) of the capacitor C7,
After charging 7, the IC power supply current is supplied only through the resistor R4. The resistor R5 limits the current value for the rapid charge assist to an appropriate value, and provides an appropriate impedance between the point 204 and the point 206 in a steady state.

FIG. 7 shows the AC voltage 504 and the AC current 506 at point 102 when the start assist circuit 202 is present, and FIG. 9 is the voltage 512 at point 206 when the start assist circuit 202 is present and the point 512. The voltage 514 at 404 is shown. As can be seen by comparing FIG. 6 and FIG. 7, even when the start assist circuit 202 is provided, the current and voltage waveforms at the point 102 are almost sine waves.

Further, as can be seen by comparing FIGS. 8 and 9, by providing the start assist circuit 202,
The voltage 512 at the point 206 rises faster,
It can be seen that the rise of the voltage 514 at is also quickened. By providing the start assist circuit 202 in this manner, the light source unit LED 40 is instantly provided after the AC power is turned on.
2 lights up. The power supply circuit 1 according to the present embodiment
Can be used for lighting other than traffic lights.

[0047]

As described above, according to the present invention, it is possible to provide a power supply circuit which operates normally even in a severe cold season or summer and the light source section emits light immediately after the power is turned on.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a power supply circuit 1 according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a configuration of a rectification unit 100.

FIG. 3 is a circuit diagram showing a configuration of a stabilized power supply circuit section 200.

FIG. 4 is a circuit diagram showing configurations of an output voltage detection unit 300 and a light source unit 400.

FIG. 5 is a schematic diagram showing a schematic configuration of a power supply circuit 1.

FIG. 6 is a waveform diagram of a voltage 500 and a current 502 at a point 102 when the start assist circuit 202 is not present.

FIG. 7 is a waveform diagram of voltage 504 and current 506 at point 102 in the presence of start assist circuit 202.

FIG. 8 is a waveform diagram of a voltage 508 at a point 206 and a waveform of a voltage 510 at a point 404 when the start assist circuit 202 is not present.

9 is a waveform of voltage 512 at point 206 and voltage 5 at point 404 when start assist circuit 202 is present. FIG.
Waveform diagram of 14

FIG. 10 is a diagram showing a change in illuminance when the temperature is changed.

FIG. 11 is a diagram showing a change in illuminance when the temperature is changed.

FIG. 12 is a diagram showing a change in illuminance when the temperature is changed.

FIG. 13 is a diagram showing a change in illuminance when the temperature is changed.

FIG. 14 is a diagram showing a change in illuminance when the temperature is changed.

FIG. 15 is a diagram showing a change in illuminance when the temperature is changed.

[Explanation of symbols]

1 ... Power supply circuit 100 ………… Rectification unit 200 ... Stabilized power supply circuit 202 ... Start assist circuit 300 ... Output voltage detector 400 ......... LED light source C7 ......... Capacitor R5, R8, R9 ......... Resistance R10 ......... Thermistor D4 ......... Light emitting diode

Continued front page    (72) Inventor Noriko Akimoto             1-11-6 Higashiueno, Taito-ku, Tokyo Tokiwa Denki             Within the corporation F term (reference) 3K072 AC01 BA01 BB01 GB04 GC04                 3K073 AA16 AA49 BA31 CA05 CG18                       CJ17 CJ22 CL14

Claims (2)

[Claims] 1. A rectifying unit that rectifies an AC power supply, a stabilized power supply circuit unit that extracts a constant voltage from the voltage rectified by the rectification unit, and a light emitting diode that is driven by an output voltage of the stabilized power supply circuit unit. The stabilized power supply circuit includes a start assist circuit that accelerates the rising at the start. 2. The power supply circuit according to claim 1, wherein the start assist circuit includes a capacitor and a resistor connected in series.