JP6300610B2 - LED power supply device and LED lighting device - Google Patents

Description

  The present invention relates to an LED power supply device and an LED lighting device using the LED power supply device.

  Patent Document 1 discloses an LED lighting device that reduces flash light generated when switching from a light-off state to a light-on state. The LED lighting device includes an isolated flyback converter that supplies a drive current to the LED, and a control circuit unit that controls the switching operation so that the detected forward current of the LED becomes a target value. The control circuit unit switches the on-time of the switching element from the time when the switching operation of the isolated flyback converter is started to turn on the off-state LED until the voltage applied to the LED increases to the lighting start voltage. After providing the first switching period having a longer period, a second switching period having a shorter on-time is provided.

JP 2013-69766 A

  By the way, in an LED power supply device using a switching power supply circuit such as a flyback converter as in Patent Document 1, a flash can be generated not only at the start of lighting but also at the time of turning off. This is because when the input power is turned off, the control voltage of the control circuit is lowered while the charging voltage remains in the smoothing capacitor on the primary side of the flyback converter, and the output control on the secondary side becomes ineffective. . Thereby, for example, the switching power supply circuit is in a maximum output state immediately before the light is turned off, and the electric charge of the smoothing capacitor is discharged at once in the secondary side LED, and flashing is generated. However, unlike the flash at the start of lighting, such a flash when the LED is turned off is a phenomenon contrary to the user's intention to turn off the light and darken, and the visual discomfort to the user is more than the flash at the start of lighting. It will be big. Furthermore, due to the afterglow applied to the user's eyes by the flash before turning off, it takes time for the user's eyes to adapt to the darkness after turning off, resulting in discomfort. In this way, the user's visual discomfort, discomfort, and the like are brought about by the flash just before turning off.

  Therefore, an object of the present invention is to provide a configuration for preventing flashing immediately before the LED is turned off in an LED power supply device including a DC / DC converter having a smoothing capacitor on the primary side.

  The LED power supply apparatus of the present invention transforms the voltage of the smoothing capacitor by transforming the voltage of the smoothing capacitor by the AC / DC conversion unit that converts the AC input voltage to DC and charges the smoothing capacitor, and the switching operation of the primary side switching element. A DC / DC converter that supplies the secondary output of 1 to the LED, an input power source detection unit that detects an AC input voltage, and a second secondary output of the DC / DC converter is fed to drive the switching element. A controller configured to control driving of the switching element so as to reduce a ratio of the first secondary output to the second secondary output when the stop of the AC input voltage is detected.

  According to the LED power supply device of the present invention, when the stop of the AC input voltage is detected by the input power supply detection unit and the control unit, the control unit is a DC / DC converter for the secondary output from the DC / DC converter to the control unit. The driving of the switching element is controlled so as to reduce the ratio of the secondary output from the LED to the LED. Therefore, after the input power is stopped, a state in which the residual energy of the smoothing capacitor on the primary side of the DC / DC converter is released at once in the LED is avoided, and flashing immediately before the LED is turned off is prevented.

  Here, the control unit is configured to control the driving of the switching element so that the voltage of the first secondary output becomes less than the forward voltage drop of the LED when the stop of the AC input voltage is detected. . As a result, as in normal use, a light-off state can be obtained immediately after the AC input power supply is stopped, and flashing in the LED is reliably prevented.

  As one form, the AC / DC converter includes a full-wave rectifier that rectifies an AC input voltage, and a power factor correction circuit that includes the smoothing capacitor and boosts the pulsating output of the full-wave rectifier to charge the smoothing capacitor. An input power supply detection part and a control part are comprised so that the stop of alternating current input voltage may be detected based on a pulsating flow output. As a result, the above-described extinguishing control is started promptly within several tens of ms after the input power supply is stopped, and flashing can be prevented with high responsiveness.

  As another form, the input power source detection unit includes a rectifier that rectifies the AC input voltage, and the input power source detection unit and the control unit are configured to detect the stop of the AC input voltage based on the pulsating output of the rectifier. You may be made to do. As a result, even in the capacitor input type circuit, the above-described extinguishing control is started quickly in about several tens of milliseconds after the input power supply is stopped, and flashing can be prevented with high responsiveness.

  As still another form, the input power supply detection unit is configured to detect the smoothing voltage of the smoothing capacitor, and when the smoothing voltage becomes less than a predetermined threshold, the input power supply detection unit and the control unit are connected to the AC input voltage. It may be configured to detect the stop of the. According to this configuration, since the output of the input power source detection unit is a direct current, the degree of freedom in design increases in the control state switching configuration in the control unit.

  Further, the control unit is configured to control the driving of the switching element in accordance with the dimming rate indicated by the dimming command signal from the outside, and the alternating current is when the dimming rate is equal to or less than the predetermined dimming rate. It is configured to reduce the ratio of the first secondary output to the second secondary output when a stop of the input voltage is detected. As a result, in a lighting state where there is no fear of flashing (for example, all light), the LED power supply device can be stopped relatively quickly after the input power supply is stopped. For example, the predetermined dimming rate is set to 20%.

  The DC / DC converter is preferably an insulating flyback converter having a transformer, and the controller is preferably connected to the auxiliary winding of the transformer. Thus, the LED power supply device of the present invention is suitably applied to a DC / DC converter composed of an insulating flyback converter.

  The LED lighting device of the present invention includes the above-described LED power supply device and an LED. Since the LED power supply device having the above effects is employed, an LED illumination device that can eliminate the visual discomfort and uncomfortable feeling when the lights are turned off is realized.

It is a figure which shows the LED power supply device and LED lighting apparatus by the 1st Embodiment of this invention. It is a figure explaining operation | movement of the LED power supply device by a comparative example. It is a figure explaining operation | movement of the LED power supply device by 1st Embodiment. It is a figure explaining operation | movement of the LED power supply device by 1st Embodiment. It is a figure which shows the LED power supply device and LED lighting apparatus by the 2nd Embodiment of this invention. It is a figure which shows the input power supply detection part in the modification of 2nd Embodiment. It is a figure which shows the input power supply detection part in the other modification of 2nd Embodiment. It is a figure which shows the LED power supply device and LED lighting apparatus by the 3rd Embodiment of this invention. It is a figure explaining operation | movement of the LED power supply device by 3rd Embodiment. It is a figure explaining a part of auxiliary power supply part and drive control part in the modification of this invention.

Embodiment 1. FIG.
In FIG. 1, the circuit block diagram of the LED power supply device 1 which concerns on the 1st Embodiment of this invention, and the LED lighting apparatus 3 using the same is shown. The LED lighting device 3 includes an LED power supply device 1 and an LED 2. The input voltage from the AC power supply AC is input to the input terminals T1 and T2 of the LED power supply device 1, and the DC outputs from the high potential output terminal T3 and the low potential output terminal T4 of the LED power supply device 1 are respectively connected via the wirings W1 and W2. Are supplied to the terminals T5 and T6 of the LED module 2. A dimming command signal from an external dimmer is input from terminals T7 and T8 of the LED power supply device 1.

  The LED power supply device 1 includes an AC / DC conversion unit 10, a DC / DC converter 20, a drive control unit 30, an output control unit 40, an auxiliary power supply unit 50, and an input power supply detection circuit 60. The drive control unit 30, the output control unit 40, and the auxiliary power supply unit 50 are collectively referred to as a control unit (30, 40, 50). LED2 includes a plurality of LED elements connected in series between terminal T5 and terminal T6. Note that the LED power supply device 1 and the LED 2 may be integrated in one housing, or may be configured as separate bodies in the two housings. In the description of the present specification, it is convenient for each block to which each circuit or component belongs, and the present invention is not bound thereto.

  The AC / DC converter 10 includes a full-wave rectifier 101, an input capacitor 102, a power factor correction circuit (hereinafter referred to as “PFC”) 110, and, if necessary, a current fuse, a noise filter, and the like before the full-wave rectifier 101. Prepare. The input AC voltage is full-wave rectified by the full-wave rectifier 101, and the pulsating voltage generated in the input capacitor 102 is supplied to the PFC 110. The PFC 110 includes an inductor 111, a switching element 112, a diode 113, a capacitor 114 (smoothing capacitor), and a PWM control circuit 115. In the following description, a node having the same potential as the negative electrode of the capacitor 114 is referred to as a primary side ground.

  The switching element 112 is PWM-controlled by high-frequency switching by the PWM control circuit 115, thereby improving the input power factor. During the period when the switching element 112 is on, energy is stored in the inductor 111 by the pulsating voltage from the full-wave rectifier 101 flowing to the inductor 111 and the switching element 112. During the period when the switching element 112 is off, the energy stored in the inductor 111 is charged to the capacitor 114 via the diode 113. As a result, the capacitor 114 is charged with a voltage boosted from the input power supply voltage. The PWM control circuit 115 drives the switching element 112 by PWM by appropriately controlling the ON width in PWM control. By this operation, the PFC 110 outputs a boosted DC voltage. The capacitor 114 may be an electrolytic capacitor of about 1 μF to 1000 μF, preferably about 10 μF to 100 μF, depending on the rated power of the LED power supply device 1.

  In the present embodiment, the DC / DC converter 20 is an insulating flyback converter. The DC / DC converter 20 includes a switching element 201, a transformer 202, a diode 203, and a capacitor 204, and includes a demagnetizing resistor 205 and a capacitor 206 as necessary. The capacitor 204 may be an electrolytic capacitor (shown) or a film capacitor. A node having the same potential as the negative electrode of the capacitor 204 is referred to as a secondary side ground. In the DC / DC converter 20, the switching element 201, the primary main winding N <b> 1 of the transformer 202, the resistor 205 and the capacitor 206 constitute a primary circuit, and the secondary main winding N <b> 2 of the transformer 202, the diode 203 and the capacitor 204 are two. Configure the secondary circuit.

  In the DC / DC converter 20, the energy from the capacitor 114 is accumulated in the primary main winding N <b> 1 of the transformer 202 during the ON period of the switching element 201, and the energy is transferred to the secondary main winding of the transformer 202 during the OFF period of the switching element 201. The capacitor 204 is charged through the diode 203 from the N2 side. The step-down ratio may be set to be approximately the same as the turn ratio of the secondary main winding N2 to the primary main winding N1 in consideration of circuit efficiency, and the output current is set to ON duty (ON width) in the PWM control of the switching element 201. ). The switching element 201 is driven by the drive control unit 30. In the following description, the output current of the DC / DC converter 20 is referred to as “output current Iout”, and the output voltage of the DC / DC converter 20 is referred to as “output voltage Vout”. In the following embodiments, the output current Iout is equal to the LED current, and the output voltage Vout is equal to the LED voltage.

  The drive control unit 30 includes a drive control IC (hereinafter also referred to as “drive control IC 30”). The reference potential of the drive control IC 30 is a primary side ground, and operates by receiving a primary side control voltage Vcc1 described later. The drive control IC 30 has an FB terminal (FB) connected to the collector terminal of the phototransistor of the photocoupler 417, an output terminal (OUT) connected to the gate terminal of the switching element 201, and the like. In the drive control IC 30, the FB terminal is connected to an internal reference voltage source 301 (for example, a constant voltage source of 5 V) via a resistor 302, and the OUT terminal is connected to the gate circuit 303. In the gate circuit 303, the pulse width of the gate signal from the output terminal is determined in accordance with the input voltage at the FB terminal. Specifically, the drive control IC 30 is configured to increase the pulse width of the gate signal with respect to the increase in the input voltage (control signal) of the FB terminal, thereby (the voltage of the capacitor 114 is constant). The output current Iout increases with increasing input voltage at the FB terminal. The output state of the phototransistor of the photocoupler 417 that determines the input voltage of the FB terminal is determined by the output control unit 40.

  The output control unit 40 includes a constant current control circuit 410 and a dimming control circuit 420, and functions to limit the output of the DC / DC converter 20 by the drive control unit 30. The reference potential of the output control unit 40 is a secondary side ground, and operates by receiving a secondary control voltage Vcc2 described later.

  The constant current control circuit 410 includes a current detection resistor 411, an operational amplifier 412, resistors 413 to 416, and a photocoupler 417. A resistor is further connected around the operational amplifier 412 as necessary.

The current detection resistor 411 includes a low resistance element inserted between the secondary side ground and the low potential side output terminal T4, and a voltage proportional to the output current Iout is generated in the current detection resistor 411.
The operational amplifier 412 is a constant current control operational amplifier having a function of making the output current Iout constant. That is, the switching element 201 is PWM controlled via the drive control unit 30 by constant current control by the output control unit 40. The current detection value detected by the current detection resistor 411 is input to the negative input terminal (−) of the operational amplifier 412 via a resistor (not shown), and the positive input terminal (+) corresponds to the target value of the output current Iout. The current reference value to be input is input. The current reference value is a divided value by the resistors 413 and 414 of the secondary side control voltage Vcc2 when all the lights are lit, and is adjusted by the dimming control circuit 420 when dimming. A feedback resistor 415 is connected between the negative input terminal and the output terminal of the operational amplifier 412. The output terminal of the operational amplifier 412 is connected to the cathode of the photodiode of the photocoupler 417 via the resistor 416, and the secondary side control voltage Vcc2 is supplied to the anode of the photodiode of the photocoupler 417. The operational amplifier 412 amplifies and outputs an error between the current detection value input to the negative input terminal and the current reference value input to the positive input terminal. In other words, the operational amplifier 412 determines the ON width in the PWM control so that the current detection value matches the current reference value.

  The dimming control circuit 420 includes an AC photocoupler 421, a resistor 422, a microcontroller (MCU) 423, and a D / A converter (DAC) 424. A resistor, a capacitor, and the like are further connected around the MCU 423 and the DAC 424 as necessary. The AC photocoupler 421 includes a photodiode connected in reverse parallel on the input side and a phototransistor on the output side. The AC photocoupler 421 converts the level of a dimming command signal from an external dimmer (in this embodiment, the dimming command signal is a PWM dimming signal whose duty ratio corresponds to the dimming rate). To do. The PWM dimming signal level-converted by the AC photocoupler 421 is input to the MCU 423. The MCU 423 calculates a dimming rate according to the input signal, and outputs a digital current reference value according to the calculated dimming rate. The digital current reference value from the MCU 423 is converted into an analog signal by the DAC 424, and the analog value is output to the constant current control circuit 410 (the operational amplifier 412) as a current reference value via a resistor (not shown). As a result, the DC / DC converter 20 is subjected to constant current control through the dimming control circuit 420, the constant current control circuit 410, and the drive control unit 30 in accordance with the dimming command signal from the external dimmer.

  In this embodiment, when the current detection value is smaller than the current reference value, the output terminal voltage of the operational amplifier 412 swings to the high side, the current flowing through the photodiode of the photocoupler 417 decreases, and the output current from the phototransistor also increases. Decrease. On the other hand, when the current detection value is larger than the current reference value, the output terminal voltage of the operational amplifier 412 swings to the low side, the current flowing through the photodiode of the photocoupler 417 increases and the output current from the phototransistor also increases. As described above, the drive control IC 30 is configured to increase the pulse width of the PWM control with respect to the decrease in the output current of the phototransistor of the photocoupler 417 (increase in the FB terminal voltage). Therefore, when the current detection value is smaller than the current reference value, the operational amplifier 412 acts in the direction of increasing the PWM control pulse width of the switching element 201, that is, in the direction of increasing the output current Iout. On the contrary, when the current detection value is larger than the current reference value, the operational amplifier 412 acts in the direction of decreasing the pulse width of the PWM control of the switching element 201, that is, the direction of decreasing the output current Iout. Thus, constant current control is performed by feedback of the output current Iout during normal lighting.

  The auxiliary power supply unit 50 includes an auxiliary power supply circuit 510 that uses the primary side ground as a reference potential and an auxiliary power supply circuit 520 that uses the secondary side ground as a reference potential. The auxiliary power circuit 510 includes a primary side auxiliary winding N3 of the transformer 202, a diode 511, and a capacitor 512. A voltage corresponding to the turn ratio of the primary side auxiliary winding N3 to the primary main winding N1 is generated in the primary side auxiliary winding N3. The voltage generated in the primary side auxiliary winding N3 is rectified and smoothed by the diode 511 and the capacitor 512, and becomes a control power source of the drive control IC 30. Note that the voltage of the capacitor 512 is referred to as a primary control voltage Vcc1.

  The auxiliary power circuit 520 includes a secondary auxiliary winding N4 of the transformer 202, a diode 521, a capacitor 522, and a three-terminal regulator 523 (regulator circuit). A voltage corresponding to the turn ratio of the secondary auxiliary winding N4 to the primary main winding N1 is generated in the secondary auxiliary winding N4. The voltage generated in the secondary auxiliary winding N4 is rectified and smoothed by the diode 521 and the capacitor 522, and the smoothed voltage is stepped down and stabilized by the three-terminal regulator 523. The input voltage of the three-terminal regulator 523 is referred to as a secondary side auxiliary voltage Vs, and the output voltage of the three-terminal regulator 523 is referred to as a secondary side control voltage Vcc2. In the present embodiment, a secondary control voltage Vcc2 of 5V is supplied to the output control unit 40.

  The power supply voltage detection unit 60 includes a photocoupler 601, a resistor 602, and a resistor 603. The photodiode of the photocoupler 601 is connected to the output terminal of the full-wave rectifier 101 via the resistor 602. The emitter terminal of the phototransistor of the photocoupler 601 is connected to the secondary side ground, and the collector terminal is connected to the secondary control power supply Vcc2 via the resistor 603 and also to a predetermined input terminal of the MCU 423. The photodiode of the photocoupler 601 generates a light amount approximately proportional to the input power supply voltage, and a current corresponding to the light amount flows through the phototransistor.

  That is, when the input power is turned on (on), a light output corresponding to the pulsating current output of the full-wave rectifier 101 is generated in the photodiode of the photocoupler 601, and the pulsating current corresponding to the light output is a photocurrent. It flows to the transistor. As a result, an inverted pulsating voltage obtained by inverting the pulsating voltage is generated at the collector terminal of the phototransistor of the photocoupler 601. On the other hand, when the input power is cut off (off), no light output is generated in the photodiode of the photocoupler 601 and no current flows through the phototransistor. The voltage at the collector terminal of the phototransistor of the photocoupler 601 becomes constant at the voltage of the secondary control power supply Vcc2. The resistor 603 may be connected between the emitter terminal of the phototransistor of the photocoupler 601 and the secondary side ground and connected to the MCU 423, and the collector terminal may be connected to the secondary control power supply Vcc2. In this case, the input voltage to the MCU 423 (the emitter voltage waveform of the phototransistor of the photocoupler 601) has a voltage waveform having the same polarity as the pulsating voltage waveform (that is, not inverted).

  The MCU 423 can determine on / off of the input power supply voltage from the collector voltage waveform of the phototransistor of the photocoupler 601. The MCU 423 switches the current reference value according to on / off of the input power supply under the dimming rate specified by the dimming command value. As will be described in detail later, the MCU 423 operates to reduce the current reference value to a value corresponding to the LED extinguishing when the input power is turned off. Since the output from the photocoupler 601 is based on the full-wave rectified waveform of the input power supply voltage, the on / off of the input power supply voltage can be detected within a half cycle of the input power supply voltage (within 10 ms at 50 Hz). In order to increase detection accuracy, a period corresponding to several cycles to several tens of cycles of the input power supply voltage (for example, several tens of milliseconds to several hundreds of milliseconds) may be set as the determination period.

  Next, the operation of the LED power supply device 1 will be described. First, FIG. 2 shows waveforms of respective parts when the input power supply of the LED power supply device according to the comparative example is turned off (that is, during the extinguishing operation). The LED power supply device according to the comparative example is obtained by removing the input power supply detection unit 60 from the LED power supply device 1. FIG. 2 shows (a) the smoothing voltage Vdc of the capacitor 114, (b) the primary side control voltage Vcc1, (c) the secondary side auxiliary voltage Vs (solid line), and the secondary side control voltage Vcc2 (dashed line), (d) driving. The FB terminal voltage Vfb of the control IC 30 and (e) the output current Iout (that is, the LED current) are shown, and the horizontal axis is time. In addition, a figure is a schematic diagram and is not as the dimension.

  Until time t1, the smoothing voltage Vdc is 400V, the primary side control voltage Vcc1 is 18V, the secondary side auxiliary voltage Vs is 18V, the secondary side control voltage Vcc2 is 5V, the FB terminal voltage Vfb is 1.1V, and the output current Iout is It shall be 100 mA. The output current during all light is 600 mA, and in this example, the case where the input power source is turned off in a dimming state of about 17% is exemplified. In the comparative example and each embodiment, the voltage supply capability of the auxiliary power circuit 510 on the primary side is substantially the same as that of the auxiliary power circuit 520.

  At time t1, the input power supply AC is turned off. Thereby, the smoothing voltage Vdc begins to decrease, and the secondary side auxiliary voltage Vs also begins to decrease. On the other hand, since the input voltage of the three-terminal regulator 523 is higher than the operable voltage, the normal operation is continued, and the secondary control voltage Vcc2 is maintained at 5 V as in the normal lighting. Since the primary side control voltage Vcc1 is also higher than the operable voltage of the drive control IC 30 (for example, about 8V), the operation is continued in the same way as during normal lighting, and the FB terminal voltage Vfb is 1.1V as before time t1. Maintained. However, the output current Iout decreases as the smoothing voltage Vdc decreases.

  At time t2, the primary side control voltage Vcc1 is equal to or higher than the operable voltage (about 8V) of the drive control IC 30, while the secondary side auxiliary voltage Vs falls below the operable voltage of the three-terminal regulator 523. The control voltage Vcc2 starts to decrease and becomes 5V or less. As a result, the current of the photodiode and the phototransistor of the photocoupler 417 decreases, and the FB terminal voltage Vfb starts to increase.

  At times t2 to t3, the drive control IC 30 increases the ON width in the PWM control according to the increase in the FB terminal voltage Vfb after time t2, and the output current Iout increases sharply. This steep rise in the output current Iout becomes a flash. By the flashing of light at times t2 to t3, the electric charge of the capacitor 114 is discharged all at once, and the smoothing voltage Vdc decreases instantaneously. Thereby, at time t3, the LED 2 is turned off, and the LED power supply device 1 is completely stopped. In this example, the times t1 to t2 are several seconds, and the times t2 to t3 are about several tens of milliseconds.

  FIG. 3 shows the waveforms of the respective parts when the input power supply of the LED power supply device 1 according to the present embodiment is off (that is, during the extinction control). Similar to FIG. 2, FIG. 3 shows (a) the smoothing voltage Vdc of the capacitor 114, (b) the primary side control voltage Vcc1, (c) the secondary side auxiliary voltage Vs (solid line), and the secondary side control voltage Vcc2 (broken line). ), (D) The FB terminal voltage Vfb of the drive control IC 30 and (e) the output current Iout (that is, the LED current) are shown, and the horizontal axis is time. In addition, a figure is a schematic diagram and is not as the dimension.

  As in the example of FIG. 2, until time t1, the smoothing voltage Vdc is 400V, the primary side control voltage Vcc1 is 18V, the secondary side auxiliary voltage Vs is 18V, the secondary side control voltage Vcc2 is 5V, and the FB terminal voltage Vfb is The output current Iout is 1.1 mA and 100 mA. The output current at the time of all light is 600 mA, and the state where the input power source is turned off in the dimming state of about 17% is exemplified. The output voltage Vout is about 35V to 90V.

  At time t1, the input power supply AC is turned off. As a result, the input from the input power supply detection unit 60 to the MCU 423 becomes constant at the secondary side control voltage Vcc2 (see FIG. 1), and the MCU 423 decreases the current reference value in the operational amplifier 412 via the DAC 424. Thereby, the FB terminal voltage Vfb of the drive control IC 30 is reduced from 1.1V to 0.8V. In this state, the current feedback does not have to act substantially. For example, the minimum secondary output is maintained. Due to the decrease in the FB terminal voltage Vfb, the output voltage on the secondary side (secondary main winding N2 side) of the DC / DC converter 20 becomes less than the forward voltage drop Vf of the LED 2, and the LED 2 is turned off. Thereafter, the switching element 201 continues to be driven in a state where the pulse width of the PWM control is narrowed (for example, the minimum pulse width). By this switching operation, the smoothing voltage Vdc, the primary side control voltage Vcc1, and the secondary side auxiliary voltage Vs gradually decrease. In this state, the pulse width in driving the switching element 201 is minimized, but the smoothing voltage Vdc is relatively high, so that the slopes of the primary and secondary control voltages Vcc1 and Vcc2 are gradually lowered. It becomes. At this time, since the input voltage of the three-terminal regulator 523 is higher than the operable voltage, the normal operation is continued, and the secondary control voltage Vcc is maintained at 5 V as in the normal lighting. Further, since the primary side control voltage Vcc1 is also higher than the operable voltage of the drive control IC 30 (for example, about 8V), the operation is continued in the same manner as during normal lighting.

  When the primary control voltage Vcc1 falls below the operable voltage (8 V) of the drive control IC 30 at time t2 (in this example, the secondary control voltage Vcc2 is 5 V at time t2), drive control is performed. The driving of the IC 30 and the switching element 201 is stopped, and the entire operation of the LED power supply device 1 is stopped. The time from time t1 to time t2 is about 30 to 50 seconds in this example.

  In the example shown in FIG. 3, at time t2, the drive control unit 30 to which the primary control voltage Vcc1 is fed operates before the output control unit 40 to which the secondary control voltage Vcc2 is fed. Although an example of stopping is shown, the order of operation stop may be reversed. FIG. 4 shows an example in which the output control unit 40 to which the secondary control voltage Vcc2 is fed stops operating before the drive control unit 30 to which the primary control voltage Vcc1 is fed.

  Similar to FIG. 3, FIG. 4 shows (a) the smoothing voltage Vdc of the capacitor 114, (b) the primary side control voltage Vcc1, (c) the secondary side auxiliary voltage Vs (solid line), and the secondary side control voltage Vcc2 (dashed line). , (D) shows the FB terminal voltage Vfb of the drive control IC 30 and (e) the output current Iout (that is, the LED current), and the horizontal axis represents time. In addition, a figure is a schematic diagram and is not as the dimension.

  Similar to the example of FIG. 3, until time t1, the smoothing voltage Vdc is 400V, the primary side control voltage Vcc1 is 18V, the secondary side auxiliary voltage Vs is 18V, the secondary side control voltage Vcc2 is 5V, and the FB terminal voltage Vfb is The output current Iout is 1.1 mA and 100 mA. The output current at the time of all light is 600 mA, and the state where the input power source is turned off in the dimming state of about 17% is exemplified.

  At time t1, as in the example of FIG. 3, when the input power supply AC is turned off, the FB terminal voltage Vfb of the drive control IC 30 is reduced from 1.1V to 0.8V, and the secondary side of the DC / DC converter 20 (Secondary main winding N2 side) The output voltage becomes less than the forward voltage drop Vf of the LED 2, and the LED 2 is turned off. Thereafter, the switching element 201 continues to be driven in a state where the pulse width of the PWM control is narrowed (for example, the minimum pulse width). By this switching operation, the smoothing voltage Vdc, the primary side control voltage Vcc1, and the secondary side auxiliary voltage Vs gradually decrease. Since the input voltage of the three-terminal regulator 523 is higher than the operable voltage, the normal operation is continued, and the secondary control voltage Vcc is maintained at 5 V as in the normal lighting. Further, since the primary side control voltage Vcc1 is also higher than the operable voltage of the drive control IC 30 (for example, about 8V), the operation is continued in the same manner as during normal lighting.

  At time t2, when the secondary side control voltage Vcc2 decreases in a state where the primary side control voltage Vcc1 is equal to or higher than the operable voltage (8V), the FB terminal voltage Vfb rises steeply as in the comparative example. However, since the smoothing voltage Vdc is sufficiently lowered by the operation from time t1 to time t2, the LED 2 is not re-lit or flashed. In other words, when the forward voltage drop of LED2 is Vf, the number of turns of the primary main winding N1 is T1, and the number of turns of the secondary main winding N2 is T2, Vdc <Vf × (T2 / T1) by time t2. ), No flash can occur in the LED 2.

  As described above with reference to FIGS. 3 and 4, after the input power supply is stopped, the supply ratio of the energy of the capacitor 114 via the transformer 202 is supplied to the LED2 side connected to the secondary main winding N2 (first secondary The output (second secondary output) to the control unit (30, 40, 50) to which the secondary auxiliary windings N3 and N4 are connected increases. As a result, the flashing phenomenon in which the energy of the capacitor 114 is released at once in the LED 2 just before extinguishing in the state where the secondary output control is not effective as shown in the comparative example is prevented.

  In the above description, the case where the dimming rate is 17% has been described. However, the present invention can be similarly applied to the turn-off control at other dimming rates. However, when the dimming rate is shallow (bright) or all lights, the voltage of the capacitor 114 is immediately discharged by driving the switching element 201 immediately after the input power supply AC is cut off, so that the flash using the residual voltage of the capacitor 114 as an energy source. Is unlikely to occur. Therefore, when the dimming rate is equal to or lower than the predetermined dimming rate, the above-described output reduction control to the LED 2 when the input power is off may be performed. For example, the predetermined dimming rate may be about 20%.

As described above, according to the LED power supply device 1 according to the present embodiment, the following effects can be obtained.
(1) Flash prevention In this embodiment, when the stop of the AC input voltage AC is detected by the input power supply detection unit 60, the control unit (30, 40, 50) is transferred from the DC / DC converter 20 to the control unit. The driving of the switching element 201 is controlled so as to reduce the ratio of the secondary output (first secondary output) from the DC / DC converter 20 to the LED 2 with respect to the secondary output (second secondary output). Therefore, a state in which the residual energy of the capacitor 114 on the primary side of the DC / DC converter 20 is released at a stroke after the input power is shut off is avoided, and flashing immediately before the LED is turned off is prevented. In particular, since the switching element 201 is driven and controlled so that the output voltage to the LED 2 becomes less than the forward drop voltage Vf when the stop of the AC input voltage AC is detected, flashing in the LED 2 is surely prevented. .

(2) High Responsiveness In the present embodiment, the input power supply detection unit 60 and the MCU 423 are configured to detect the stop based on the pulsating flow output based on the input power supply voltage. As a result, the above-described extinguishing control is started promptly within several tens of ms after the input power supply is stopped, and flashing is prevented with high responsiveness.

(3) Timely extinction control Further, in the present embodiment, the above extinction control is performed when the dimming rate is equal to or lower than the predetermined dimming rate and when the stop of the input voltage AC is detected. Therefore, in the lighting state where there is no fear of flashing (for example, in the case of all light), the LED power supply device 1 can be stopped relatively quickly after the input power supply is stopped.

Embodiment 2. FIG.
In the first embodiment, the configuration in which the AC / DC conversion unit 10 includes the power factor correction circuit is shown. However, in the present embodiment, the AC / DC conversion unit 10 is configured by a so-called capacitor input type circuit. In FIG. 5, the circuit diagram of the LED power supply device 1 by this embodiment and the LED lighting apparatus 3 using the same is shown. The difference from the first embodiment shown in FIG. 1 resides in the AC / DC converter 10 and the input power source detector 60. 5, elements denoted by the same reference numerals as those in FIG. 1 are substantially the same as those in FIG. 1 unless otherwise specified, and detailed description thereof is omitted.

  The AC / DC converter 10 includes a full-wave rectifier 101 and a capacitor 114, and an output terminal of the full-wave rectifier 101 is directly connected to the capacitor 114. The input power supply detection unit 60 includes a photocoupler 601, a resistor 602, a resistor 603, and a full-wave rectifier 604 (rectifier). In the AC / DC converter 10, the output of the full-wave rectifier 101 is smoothed by the capacitor 114, so that the voltage of the input power supply AC is detected in a pulsating state (that is, without delay) at the output terminal of the full-wave rectifier 101. Can not do it. Therefore, the full-wave rectifier 604 is connected to the AC line between the input power supply AC and the full-wave rectifier 101, and a pulsating output obtained by full-wave rectifying the input power supply voltage is input to the photocoupler 601. Since the current flowing through the full-wave rectifier 604 is limited by the resistor 602, an element having a smaller current capacity than the full-wave rectifier 101 can be used for the full-wave rectifier 604.

  6A, a diode 605 (rectifier) may be connected instead of the full-wave rectifier 604. As shown in FIG. In this case, the anode of the diode 605 is connected to one AC line, the cathode of the photodiode of the photocoupler 601 is connected to the other AC line, and a half-wave rectified waveform is input to the photocoupler 601. Since the input from the photocoupler 601 to the MCU 423 is based on a half-wave rectified waveform of the input power supply voltage, the on / off of the input power supply voltage is detected within one cycle of the input power supply voltage (within 20 ms for 50 Hz). obtain. In order to improve detection accuracy, a period corresponding to several cycles to several tens of cycles of the input power supply voltage (for example, several tens of milliseconds to several hundreds of milliseconds) may be set as the determination period.

  Alternatively, as shown in FIG. 6B as another modification, the AC photocoupler 606 may be connected instead of the photocoupler 601 without connecting the full-wave rectifier 604 and the diode 605. In this case, the parallel photodiode of the AC photocoupler 606 is connected to the AC line via the resistor 602.

  In the form shown in FIGS. 5, 6A, and 6B, the turn-off control when the input power is off is the same as that of the first embodiment shown in FIG. 3 or FIG. Thereby, also in this embodiment, the same effects as the effects (1) prevention of flash, (2) high responsiveness, and (3) timely turn-off control described above with respect to the first embodiment can be obtained.

Embodiment 3. FIG.
In the first and second embodiments, the configuration in which the input power source detection unit 60 detects the pulsating output from the input power source AC is shown. However, in this embodiment, the input power source detection unit 60 uses the smoothed voltage of the capacitor 114. The structure to detect is shown. In FIG. 7, the circuit diagram of the LED power supply device 1 by this embodiment and the LED lighting apparatus 3 using the same is shown. The difference from the first embodiment shown in FIG. 1 is in the connection of the input power source detection unit 60 and the operation of the MCU 423. 7, elements denoted by the same reference numerals as those in FIG. 1 are substantially the same as those in FIG. 1 unless otherwise specified, and detailed description thereof is omitted.

  The resistor 602 of the input power source detection unit 60 is connected to the positive terminal of the capacitor 114. As a result, a direct current flows through the photodiode and the phototransistor of the photocoupler 601, and a direct current voltage is input to the MCU 423. The MCU 423 is configured to perform the above-described extinguishing control when the input voltage from the photocoupler 601 exceeds a predetermined value (that is, when the smoothed voltage Vdc of the capacitor 114 falls below a threshold value). Therefore, the calculation in the MCU 423 may be simple. The threshold value may be a voltage that is about 80 to 90% of the smoothing voltage Vdc during normal lighting.

  FIG. 8 shows respective waveforms of the LED power supply device 1 according to the present embodiment when the input power is turned off (that is, during extinguishing control). Similar to FIG. 3, FIG. 8 shows (a) the smoothing voltage Vdc of the capacitor 114, (b) the primary side control voltage Vcc1, (c) the secondary side auxiliary voltage Vs (solid line), and the secondary side control voltage Vcc2 (broken line). ), (D) The FB terminal voltage Vfb of the drive control IC 30 and (e) the output current Iout (that is, the LED current) are shown, and the horizontal axis is time. In addition, a figure is a schematic diagram and is not as the dimension.

  Similar to the example of FIG. 3, until time t1, the smoothing voltage Vdc is 400V, the primary side control voltage Vcc1 is 18V, the secondary side auxiliary voltage Vs is 18V, the secondary side control voltage Vcc2 is 5V, and the FB terminal voltage Vfb is The output current Iout is 1.1 mA and 100 mA. The output current at the time of all light is 600 mA, and the state where the input power source is turned off in the dimming state of about 17% is exemplified. The output voltage Vout is about 35V to 90V.

  At time t1, the input power supply AC is turned off. As a result, as in the case of the comparative example shown in FIG. 2, the smoothing voltage Vdc begins to decrease, and the secondary side auxiliary voltage Vs also begins to decrease. On the other hand, since the input voltage of the three-terminal regulator 523 is higher than the operable voltage, the normal operation is continued, and the secondary control voltage Vcc2 is maintained at 5 V as in the normal lighting. Since the primary side control voltage Vcc1 is also higher than the operable voltage of the drive control IC 30 (for example, about 8V), the operation is continued in the same way as during normal lighting, and the FB terminal voltage Vfb is 1.1V as before time t1. Maintained. However, the output current Iout decreases as the smoothing voltage Vdc decreases.

  When the smoothed voltage Vdc falls below a threshold value (for example, 350 V) at time t <b> 2, this state is detected by the input power supply detection unit 60 and the MCU 423, and the MCU 423 decreases the current reference value in the operational amplifier 412 via the DAC 424. Thereby, the FB terminal voltage Vfb of the drive control IC 30 is reduced from 1.1V to 0.8V. Due to the decrease in the FB terminal voltage Vfb, the output voltage on the secondary side (secondary main winding N2 side) of the DC / DC converter 20 becomes less than the forward voltage drop Vf of the LED 2, and the LED 2 is turned off. Thereafter, the switching element 201 continues to be driven in a state where the pulse width of the PWM control is narrowed (for example, the minimum pulse width). By this switching operation, the smoothing voltage Vdc, the primary side control voltage Vcc1, and the secondary side auxiliary voltage Vs gradually decrease. Since the input voltage of the three-terminal regulator 523 is higher than the operable voltage, the normal operation is continued, and the secondary control voltage Vcc is maintained at 5 V as in the normal lighting. Further, since the primary side control voltage Vcc1 is also higher than the operable voltage of the drive control IC 30 (for example, about 8V), the operation is continued in the same manner as during normal lighting.

  When the primary control voltage Vcc1 falls below the operable voltage (8 V) of the drive control IC 30 at time t3 (in this example, the secondary control voltage Vcc2 is 5 V or more at time t3), drive control The driving of the IC 30 and the switching element 201 is stopped, and the entire operation of the LED power supply device 1 is stopped. The time from the time t1 to the time t3 is slightly shorter than the time from the time t1 to the time t2 in the first embodiment (FIG. 3) by the amount that the energy of the capacitor 114 is released by the LED 2 at the time t1 to t2.

  As in the example shown in FIG. 4 of the first embodiment, even if the operation stop of the output control unit 40 occurs before the operation stop of the drive control unit 30, no flashing occurs. Conversely, when the smoothing voltage Vdc <forward voltage drop Vf × (secondary main winding N2 number of turns T2 / primary main winding N1 number of turns T1), the output control unit 40 applies the maximum duty to the drive control unit 30. The switching element 201 may be driven with (maximum ON width). As a result, the remaining voltage of the capacitor 114 can be discharged when the possibility of flashing disappears, and the extinguishing control can be terminated quickly.

  As described above, in this embodiment as well, the following effect (4) can be obtained in addition to the effect (1) flash prevention and (3) timely turn-off control described above with respect to the first embodiment. The present embodiment can also be applied to the second embodiment (capacitor input type circuit).

(4) Improvement in design freedom According to the present embodiment, the output of the input power source detection unit 60 is a direct current. Therefore, the degree of freedom of design increases in the current reference value switching configuration in the output control unit 40. For example, when the collector voltage of the phototransistor of the photocoupler 601 exceeds a predetermined value (that is, when the smoothing voltage Vdc is less than the threshold value), an additional resistor is connected in parallel to the resistor 414, and the current reference value is reduced. can do.

<Modification>
Although preferred embodiments of the present invention have been described above, the present invention can be modified into various modes as shown below, for example.

(1) Modification of DC / DC Converter 20 In each of the above-described embodiments, a flyback converter is shown as the DC / DC converter 20, but the DC / DC converter 20 is a switching power supply circuit composed of a converter of another type. May be. For example, the DC / DC converter 20 may be a forward converter, a non-insulated step-down chopper circuit, or the like.

(2) Modification of output control unit 40 In each of the above embodiments, the configuration in which the output control unit 40 performs constant current control (current feedback control) has been described. However, if the output of the drive control unit 30 can be limited, the constant current control is performed. It does not have to be done. For example, even if the output control unit 40 is configured to feedforward control the output current, the advantageous effects of the present invention can be enjoyed. In each of the above-described embodiments, in the extinguishing control, the LED 2 is extinguished by setting the voltage of the first secondary output to be less than the forward drop voltage Vf of the LED 2. However, the first second output is within the range in which flashing is prevented. The LED 2 may be dimmed by setting the next output voltage in the vicinity of the forward voltage drop Vf.

(3) Modification 1 of the auxiliary power supply unit 50
In each of the embodiments described above, the auxiliary power supply circuit 510 on the primary side of the auxiliary power supply unit 50 generates the control power from the secondary auxiliary winding N3. However, from the snubber circuit provided for the switching element 201 It is good also as a structure which produces | generates control power supply. For example, as shown in FIG. 9, the capacitor 513 is connected to the drain terminal of the switching element 201, and the anode of the diode 514 is connected to the source terminal (primary ground). The connection point between the capacitor 513 and the diode 514 is connected to the anode of the diode 515, and the cathode of the diode 515 is connected to the positive terminal of the capacitor 512. Thereby, the pulsed voltage generated in the capacitor 513 when the switching element 201 is turned on / off can be used to generate the primary control voltage Vcc1. Note that the voltage generated in the capacitor 513, that is, the power generation capability of the auxiliary power circuit 510 depends on the switching frequency rather than the pulse width in driving the switching element 201 (if the smoothing voltage Vdc is the same). Therefore, even when the drive pulse width of the switching element 201 is narrowed during the extinction control, the supply capability of the primary power supply voltage Vcc1 is ensured in a relatively high state.

(4) Modification 2 of the auxiliary power supply unit 50
In each of the above embodiments, the three-terminal regulator 523 is used as a regulator circuit that generates the secondary side control voltage Vcc2 from the secondary side auxiliary voltage Vs. However, a step-down circuit using a series regulator may be used, or a step-down chopper circuit. A ringing choke converter circuit or the like may be used. In each of the above embodiments, the DC / DC converter 20 is constituted by a flyback converter, and the primary control voltage Vcc1 and the secondary auxiliary voltage Vs are generated from the auxiliary winding of the transformer of the flyback converter. However, the configuration in which these control voltages are generated is not limited to this. For example, when the DC / DC converter 20 is a forward type converter, the primary side control voltage Vcc1 and the secondary side auxiliary voltage Vs are auxiliary windings provided in a choke coil connected in series to the transformer secondary winding. It can also be generated from.

1 LED power supply 2 LED
3 LED lighting device 10 AC / DC converter 20 DC / DC converter 30 Drive controller 40 Output controller 50 Auxiliary power source 60 Input power source detector 101 Full wave rectifier 110 Power factor improving circuit 114 Capacitor (smoothing capacitor)
201 switching element 202 transformer 604 full-wave rectifier (rectifier)
605 Diode (rectifier)

Claims (9)

An LED power supply,
An AC / DC converter that converts an AC input voltage into a DC voltage to charge a smoothing capacitor;
A DC / DC converter that transforms the voltage of the smoothing capacitor by the switching operation of the primary side switching element and supplies the transformed first secondary output to the LED;
An input power source detection unit for detecting the AC input voltage;
The second secondary output of the DC / DC converter is fed to drive the switching element, and when the stop of the AC input voltage is detected , the driving of the switching element is continued and the switching element is driven. LED that includes a control unit in which the second secondary output controls the driving of the switching element so as to reduce the rate of the first secondary output for the previous SL second secondary output in a state of being supplied Power supply.   2. The LED power supply device according to claim 1, wherein when the stop of the AC input voltage is detected, the control unit causes the voltage of the first secondary output to be less than a forward voltage drop of the LED. An LED power supply device that controls driving of the switching element.   3. The LED power supply device according to claim 1, wherein the AC / DC converter boosts a pulsating current output of the full-wave rectifier including a full-wave rectifier that rectifies the AC input voltage and the smoothing capacitor. An LED power supply device including a power factor correction circuit for charging the smoothing capacitor, wherein the input power supply detection unit and the control unit detect a stop of the AC input voltage based on the pulsating output.   3. The LED power supply device according to claim 1, wherein the input power supply detection unit includes a rectifier that rectifies the AC input voltage, and the input power supply detection unit and the control unit are based on a pulsating flow output of the rectifier. An LED power supply device configured to detect a stop of the AC input voltage.   3. The LED power supply device according to claim 1, wherein the input power supply detection unit is configured to detect a smoothing voltage of the smoothing capacitor, and the input power supply when the smoothing voltage becomes less than a predetermined threshold value. 4. The LED power supply device comprised so that a detection part and the said control part might detect the stop of the said AC input voltage.   6. The LED power supply device according to claim 1, wherein the control unit is configured to control driving of the switching element according to a dimming rate indicated by an external dimming command signal. And reducing the ratio of the first secondary output to the second secondary output when the dimming rate is equal to or less than a predetermined dimming rate and when the stop of the AC input voltage is detected. LED power supply device configured as described above.   The LED power supply device according to claim 6, wherein the predetermined dimming rate is set to 20%.   8. The LED power supply device according to claim 1, wherein the DC / DC converter is an insulating flyback converter having a transformer, and the control unit is connected to an auxiliary winding of the transformer. Power supply.   An LED lighting device comprising the LED power supply device according to claim 1 and the LED.

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