JP2011062043A - Power factor improving circuit and led luminaire using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power factor improving circuit that improves a power factor and can constitute a power supply that need to comply with harmonic guidelines, and also to provide an LED luminaire using the same. <P>SOLUTION: The power factor improving circuit includes: an AC power supply AC; a rectifier circuit RC1 for rectifying the AC voltage of the AC power supply; a transformer T1 having a primary winding P1, a secondary winding S1, and a tertiary winding P2; a series circuit consisting of the primary winding of the transformer and a switching element Q1 and connecting to both output terminals of the rectifier circuit; rectifying and smoothing circuits D1, C1 that rectify and smooth the voltage appearing on the secondary winding of the transformer and supply the obtained DC voltage to a load; and a control circuit 10 that generates an on-pulse width signal having a predetermined width based on the DC voltage of the rectifying and smoothing circuit and turns on/off the switching element based on the on-pulse width signal. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a power factor correction circuit and an LED lighting apparatus using the circuit, and more particularly to a technique for improving a power factor and suppressing noise.

  FIG. 9 shows a circuit diagram of a DC power supply device having a conventional power factor correction circuit (Patent Document 1). The direct-current power supply device shown in FIG. 9 is obtained by eliminating a smoothing capacitor composed of an electrolytic capacitor that is normally connected to both ends of the output of the rectifier bridge 101. In FIG. 9, the AC voltage of the AC power supply AC is rectified by the rectifier bridge 101 and converted into a full-wave rectified voltage. The full-wave rectified voltage is switched by the switching control circuit 105, and a predetermined DC voltage is obtained at the DC power supply output circuit 106.

  The switching control circuit 105 includes a primary winding Np, MOSFETs 1SHOT as switching elements, and elements (Ct, Rt) that determine a time constant. By connecting the resistor Rt to the full-wave rectified voltage line, when the instantaneous voltage is high, the capacitor Ct is charged faster and the pulse width is reduced. Conversely, when the instantaneous voltage is low, the pulse width increases.

  FIG. 10 shows a current waveform flowing through the primary winding Np, and the angle of the hatched portion of the triangle increases as the voltage rises. By shortening Ton as the voltage rises, the peak current Ip is set to a constant value and output. The voltage is stabilized by frequency control.

  The auxiliary power circuit 102 supplies DC power to the IC power circuit 104 and monitors the voltage of the DC power output circuit 106. A voltage dividing resistor for controlling the gate of the PUT is connected to the output of the auxiliary power supply circuit 102, and the PUT oscillation circuit 103 changes the oscillation frequency so as to make the output voltage of the auxiliary power supply circuit 102 constant, and the switching control circuit 105 A trigger pulse is output at 1 SHOT.

JP 2000-32748 A

  However, in the conventional DC power supply device, since the peak current Ip of the switching current is averaged, the input current waveform is a trapezoidal current waveform, and the power factor is about 0.6. Also, since the input current waveform approximates a trapezoidal wave, the current flow starts and ends with a steep slope. For this reason, abnormal noise is generated from the transformer, or the power factor becomes about 0.6, so that there is a problem that it is not possible to configure a power source that requires harmonic regulation such as an AC adapter and a lighting fixture.

  The subject of this invention is providing the power factor improvement circuit which can improve the power factor, and can comprise the power supply which needs a harmonic regulation response | compatibility, and an LED lighting fixture using the same.

  In order to solve the above problems, a power factor correction circuit according to the present invention includes an AC power source, a rectifier circuit that rectifies an AC voltage of the AC power source, a primary winding, a secondary winding, and a tertiary winding. A series circuit composed of a primary winding and a switching element connected to both ends of the output of the rectifier circuit, and a DC voltage obtained by rectifying and smoothing a voltage generated in the secondary winding of the transformer. And a control circuit for generating an on-pulse width signal having a constant width based on a DC voltage of the rectifying and smoothing circuit and turning on / off the switching element by the on-pulse width signal. .

  The LED lighting apparatus of the present invention includes an AC power source, a rectifier circuit that rectifies an AC voltage of the AC power source, a transformer having a primary winding, a secondary winding, and a tertiary winding, and both ends of the output of the rectifier circuit. A series circuit including a primary winding and a switching element connected to each other, a rectifying / smoothing circuit for supplying a DC voltage obtained by rectifying and smoothing a voltage generated in the secondary winding of the transformer to a load, A current detection circuit for detecting an output current flowing through a load, and generating an on-pulse width signal having a constant width based on a DC voltage of the rectifying and smoothing circuit, and turning on / off the switching element by the on-pulse width signal and the current detection circuit A control circuit that controls the output current detected at a constant value; a voltage detection circuit that detects a DC voltage of the rectifying and smoothing circuit; and the voltage detection circuit and the control circuit. And a time constant circuit having a phase compensation resistor and a phase compensation capacitor, and the time constant of the phase compensation resistor and the phase compensation capacitor is a rectified waveform of the AC voltage of the AC power supply. The control circuit is set to have a response time of ½ times or more of the cycle, and the control circuit detects a zero voltage based on a voltage generated in the tertiary winding of the transformer, and the zero voltage detection circuit And a pulse width control circuit that generates the on-pulse width signal for turning on the switching element by the zero voltage detected in step (1).

  According to the power factor correction circuit of the present invention, a constant width on-pulse width generated based on a feedback signal which is a DC voltage from the secondary side of the transformer, regardless of the input voltage waveform of substantially one cycle of the full-wave rectified waveform. Power is supplied to the output on the secondary side of the transformer by turning on / off the switching element with a signal. Since the on-pulse width signal has a constant on-pulse width, an input current flows according to the input voltage. Therefore, the power factor is greatly improved.

  Further, according to the LED lighting apparatus of the present invention, the power factor is greatly improved, the recovery current of the secondary diode can be eliminated, noise can be suppressed, and the output current can be controlled to a constant value. The LEDs can be turned on uniformly.

It is a block diagram which shows the structure of the power factor improvement circuit which concerns on Example 1 of this invention. It is a circuit diagram which shows the detail of the zero voltage detection circuit and pulse width control circuit in the power factor improvement circuit based on Example 1 of this invention. It is a figure which shows the operation | movement waveform of the pulse width control circuit of Example 1. FIG. It is a figure which shows the switching current waveform at the time of 50% load and 100% load at the time of AC100V input in the power factor improvement circuit of Example 1. FIG. It is a figure which shows the waveform of the input voltage and input current at the time of AC100V input in the power factor improvement circuit of Example 1. FIG. It is a figure which shows the power factor and efficiency with respect to each voltage in the power factor improvement circuit of Example 1. FIG. It is a block diagram which shows the structure of the power factor improvement circuit which concerns on Example 2 of this invention. It is a block diagram which shows the structure of the power factor improvement circuit which concerns on Example 3 of this invention. It is a block diagram which shows the structure of the direct-current power supply device provided with the conventional power factor improvement circuit. FIG. 10 is a current waveform diagram during switching by control of the conventional DC power supply device shown in FIG. 9.

  Hereinafter, some of the power factor correction circuits according to the embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration of a power factor correction circuit according to Embodiment 1 of the present invention. In FIG. 1, a capacitor Co and a reactor L1 are connected to both ends of the AC power supply AC, and an input terminal of a full-wave rectifier circuit RC1 that rectifies the AC voltage of the AC power supply AC is connected to the output of the reactor L1.

  A series circuit of a primary winding P1 of the transformer T1 and a switching element Q1 made of a MOSFET is connected to the output terminal of the full-wave rectifier circuit RC1.

  The transformer T1 is formed of a flyback transformer, and includes a primary winding P1, a secondary winding S1, and a tertiary winding P2.

  A series circuit of a diode D1 and a smoothing capacitor C1 is connected to both ends of the secondary winding S1 of the transformer T1. The diode D1 and the smoothing capacitor C1 constitute a rectifying and smoothing circuit, and supply a DC voltage obtained by rectifying and smoothing the voltage generated in the secondary winding S1 of the transformer T1 to a load (not shown).

  A series circuit of a resistor R2 and a resistor R3 is connected to both ends of the smoothing capacitor C1, and an inverting input terminal of the error amplifier OP1 is connected to a connection point between the resistor R2 and the resistor R3. A reference power supply Ref1 is connected to the non-inverting input terminal of the operational amplifier OP1. A series circuit of a resistor R1, a photodiode of the photocoupler PC1, and a diode D2 is connected between the output terminal of the error amplifier OP1 and one end of the smoothing capacitor C1. The error amplifier OP1 amplifies and outputs the difference voltage between the divided voltage obtained by dividing the output voltage of the smoothing capacitor C1 by the resistors R2 and R3 and the voltage of the reference power source Ref1. A current flows through the photocoupler PC1 according to this differential voltage, and the pulse width control circuit 12 controls the on width of the pulse.

  The error amplifier OP1, the reference power supply Ref1, the resistor R2, and the resistor R3 constitute an output voltage detection circuit.

  The control circuit 10 generates an on-pulse width signal having a constant width based on the voltage (feedback signal) from the photocoupler PC1, and turns on / off the switching element Q1 based on the on-pulse width signal.

  The control circuit 10 detects a zero voltage based on the voltage generated in the tertiary winding P2 of the transformer T1, and turns on the switching element Q1 using the zero voltage detected by the zero voltage detection circuit 11. A pulse width control circuit 12 that generates an on-pulse width signal and a drive control circuit 13 that generates a drive signal for turning on / off the switching element Q1 based on the on-pulse width signal from the pulse width control circuit 12 are provided.

  FIG. 2 is a circuit diagram showing details of a zero voltage detection circuit and a pulse width control circuit in the power factor correction circuit according to Embodiment 1 of the present invention. In FIG. 2, the zero voltage detection circuit 11 includes a comparator CP1, a reference power supply Vro, and a one-shot circuit 111. The comparator CP1 compares the voltage of the reference power source Vro with the voltage generated in the tertiary winding P2 of the transformer T1, and outputs an H level when the voltage generated in the tertiary winding P2 of the transformer T1 becomes zero voltage. .

  The one-shot circuit 111 generates a negative one-shot pulse when the H level is input from the comparator CP1, and outputs this negative one-shot pulse to the capacitor Cs in the pulse width control circuit 12.

  The pulse width control circuit 12 includes a current source I1, a current source I2, a comparator CP2, and a capacitor Cs. A parallel circuit of a phototransistor of the photocoupler PC1, a phase compensation resistor Rf, and a phase compensation capacitor Cf is connected between the non-inverting input terminal of the comparator CP2 and the ground. The non-inverting input terminal of the comparator CP2 is connected to the non-inverting input terminal of the comparator CP2. A current source I2 is connected.

  The inverting input terminal of the comparator CP2 is connected to the current source I1 and one end of the capacitor Cs, and the other end of the capacitor Cs is connected to the ground. One end of the capacitor Cs is connected to the output of the one-shot circuit 111. The output of the comparator CP2 is connected to the drive control circuit 13.

  The phase compensation resistor Rf and the phase compensation capacitor Cf constitute a time constant circuit, and the time constant of the phase compensation resistor Rf and the phase compensation capacitor Cf represents the rectified waveform of the AC voltage of the AC power supply AC. The response time is set to be 1/2 or more times the period. That is, the time constant is selected so that the collector-emitter voltage of the photocoupler PC1 does not fluctuate significantly within the period of the full-wave rectification waveform of the AC voltage (that is, becomes substantially constant).

  Next, the operation of the control circuit 10 will be described. First, a predetermined current flows from the constant current source I1 to the capacitor Cs of the pulse width control circuit 12, and the capacitor Cs is charged. Further, a predetermined current flows from the constant current source I2 to the parallel circuit of the phase compensation capacitor Cf, the phase compensation resistor Rf, and the photocoupler PC1, and the phase compensation capacitor Cf is charged.

  The capacitor Cs is charged by the current flowing through the constant current source I1, and the voltage Vcs of the capacitor Cs rises linearly in proportion to time.

  As shown in FIG. 3A, the comparator CP2 compares the voltage Vcs of the capacitor Cs with the voltage Vcf of the phase compensation capacitor Cf (the collector-emitter voltage of the photocoupler PC1) and compares the voltage Vcs of the phase compensation capacitor Cf. During the period when the voltage Vcf is equal to or lower than the voltage Vcs of the capacitor Cs, an on-pulse width signal (CP2 output) is generated and the H level is output to the drive control circuit 13.

  Note that the collector-emitter voltage of the photocoupler PC1 changes according to the feedback signal from the secondary side of the transformer T1, and in the example shown in FIG. 1, when the output voltage on the secondary side of the transformer T1 rises, the photocoupler PC1. Collector-emitter voltage, that is, the voltage Vcf across the capacitor Cf rises from the value shown in FIG. 3A to the value shown in FIG. For this reason, the on-pulse width of the on-pulse width signal (CP2 output) increases.

  When the voltage Vcs of the capacitor Cs rises and exceeds the collector-emitter voltage of the photocoupler PC1, the output of the comparator CP2 becomes L level. For this reason, the output of the drive control circuit 13 also becomes L level, and the switching element Q1 is turned off.

  At this time, the energy stored in the primary winding P1 of the transformer T1 is output to the smoothing capacitor C1 and the load via the secondary winding S1 and the diode D1. When the release of the energy stored in the primary winding P1 of the transformer T1 is completed, the winding voltage of the transformer T1 decreases and starts linking. For this reason, the polarity of the voltage is inverted to change to zero voltage.

  The comparator CP1 of the zero voltage detection circuit 11 compares the voltage of the tertiary winding P2 of the transformer T1 with the voltage Vro of the reference power supply (a voltage slightly higher than the zero voltage), and the voltage of the tertiary winding P2 becomes zero voltage. Sometimes H level is output to the one-shot circuit 111. The one-shot circuit 111 outputs an L level of one pulse to one end of the capacitor Cs based on the input H level. For this reason, since the capacitor Cs is discharged, the pulse width control circuit 12 outputs an H-level on-pulse width signal to the drive control circuit 13.

  The drive control circuit 13 turns on the switching element Q1 based on the on-pulse width signal.

  The time constant between the phase compensation resistor Rf and the phase compensation capacitor Cf is selected so that the collector-emitter voltage of the photocoupler PC1 does not fluctuate significantly within the period of the full-wave rectification waveform of the input voltage. . Specifically, the time constant of the phase compensation resistor Rf and the phase compensation capacitor Cf is selected to be a response time that is 1/2 times or more the period of the full-wave rectified waveform of the input voltage. For this reason, the on-pulse width of the pulse signal is constant.

  That is, the switching element Q1 is turned on / off by a constant width on-pulse width signal generated based on a feedback signal that is a DC voltage from the secondary side of the transformer T1, regardless of the input voltage waveform of substantially one cycle of the full-wave rectified waveform. By turning it off, power is supplied to the output on the secondary side of the transformer T1. Since the on-pulse width signal has a constant on-pulse width, an input current flows according to the input voltage, so that the power factor is greatly improved.

  4A shows the AC input voltage Vin and the input current Id when the voltage of the AC power supply is 100V and 50% load, and FIG. 4B shows the AC input when the voltage of the AC power supply is 100V and 100% load. The voltage Vin and the input current Id are shown. 4 (a) and 4 (b), since the on-pulse width is constant, the input current Id consisting of a sinusoidal switching current flows according to the sinusoidal input voltage Vin, and the power factor is greatly improved. The

  FIG. 5 shows waveforms of the input voltage and the input current when AC 100 V is input in the power factor correction circuit of the first embodiment. FIG. 6 shows the power factor and efficiency for each voltage in the power factor correction circuit of the first embodiment. By performing constant control of the on-pulse width, as shown in FIG. 6, the power factor becomes 0.99 at 100 VAC and 0.935 at 240 VAC, and a power factor of 0.9 or more can be realized.

  In addition, since the zero voltage detection circuit 11 detects that the voltage of the tertiary winding P2 is zero and turns on the switching element Q1, the recovery current of the secondary diode D1 is eliminated and the generation of noise is suppressed. can do.

  Further, when the present invention is compared with a power source combining a general power factor correction circuit (PFC) and a DC-DC converter, the PFC and the input smoothing capacitor (smoothing capacitor connected to the output of the full-wave rectifier circuit RC1). ) Is eliminated, so parts can be greatly reduced.

  FIG. 7 is a block diagram showing the configuration of the power factor correction circuit according to Embodiment 2 of the present invention. The power factor correction circuit of the second embodiment shown in FIG. 7 is obtained by adding an output constant current circuit 20 and a diode D3 to the power factor improvement circuit of the first embodiment shown in FIG. The output constant current circuit 20 corresponds to a current detection circuit, and includes a resistor R4, an error amplifier OP3, and a reference power supply Ref2. A load RL such as an LED is connected to both ends of the capacitor C1.

  The diode D3 is connected between the photodiode of the photocoupler PC1 and the output terminal of the error amplifier OP3. The resistor R4 is connected between one end of the secondary winding S1 of the transformer T1 and one end of the load RL.

  The error amplifier OP3 amplifies the difference voltage between the voltage generated by the current flowing through the resistor R4 through the load RL and the voltage of the reference power supply Ref2, and controls the pulse width control of the amplified difference voltage via the diode D3 and the photocoupler PC1. Is transmitted to the circuit 12.

  The pulse width control circuit 12 controls the on pulse width based on the comparison output. That is, the pulse width control circuit 12 controls the on pulse width so that the voltage generated by the current flowing through the resistor R4 via the load RL becomes the voltage of the reference power supply Ref2. That is, the output current can be made constant by controlling the on-pulse width.

  In addition, this power factor improvement circuit can be utilized for the LED lighting fixture which lights this LED by load being LED. In this case, since the output current can be controlled to a constant value, the LEDs can be lit uniformly.

  FIG. 8 is a block diagram showing the configuration of the power factor correction circuit according to Embodiment 3 of the present invention. The power factor correction circuit of the third embodiment shown in FIG. 8 is obtained by connecting the primary side voltage detection circuit 30 to the primary winding P2 of the transformer T1 and simplifying the secondary side circuit of the transformer T1. .

  The primary side voltage detection circuit 30 is configured as follows. A series circuit of a diode D2 and a capacitor C2 is connected to both ends of the tertiary winding P2 of the transformer T1. A series circuit of a resistor R2 and a resistor R3 is connected to a connection point between the diode D2 and the capacitor C2.

  The error amplifier OP1 amplifies the difference voltage between the voltage of the reference power source Ref1 and the voltage obtained by dividing the DC voltage generated at both ends of the capacitor C2 by the resistor R2 and the resistor R3, and controls the pulse width of the amplified difference voltage. Output to the circuit 12. The pulse width control circuit 12 can turn on / off the switching element Q1 by controlling the on-pulse width to make the output voltage constant.

  Note that the time constant of the capacitor C2 and the resistors R2 and R3 is selected to be a response time that is 1/2 times or more the period of the full-wave rectified waveform of the input voltage.

  The present invention is applicable to power supply devices such as LED lighting fixtures, AC adapters, and chargers.

AC AC power supply RC1 Full wave rectifier circuit 10 Control circuit 11 Zero voltage detection circuit 12 Pulse width control circuit 13 Drive control circuit 20 Output constant current circuit 30 Primary side voltage detection circuit 111 One shot circuit Q1 Switching elements D1, D2, D3 Diodes C0, C1, C2, Cs Capacitor Cf Phase compensation capacitor Rf Phase compensation resistor L1 Reactor T1 Transformer P1 Primary winding S1 Secondary winding P2 Tertiary windings OP1 to OP3 Error amplifier CP1. CP2 Comparator I1, I2 Constant current source PC1 Photocoupler

Claims (4)

AC power supply,
A rectifier circuit for rectifying the AC voltage of the AC power source;
A transformer having a primary winding, a secondary winding and a tertiary winding;
A series circuit connected to both ends of the output of the rectifier circuit and including a primary winding and a switching element of the transformer;
A rectifying and smoothing circuit for supplying a DC voltage obtained by rectifying and smoothing a voltage generated in the secondary winding of the transformer to a load;
A control circuit for generating an on-pulse width signal having a constant width based on a DC voltage of the rectifying and smoothing circuit, and for turning on / off the switching element by the on-pulse width signal;
A power factor correction circuit comprising: A voltage detection circuit for detecting a DC voltage of the rectifying and smoothing circuit;
A time constant circuit connected to the voltage detection circuit and the control circuit and having a phase compensation resistor and a phase compensation capacitor;
The time constant between the phase compensation resistor and the phase compensation capacitor is set so that the response time is at least 1/2 times the period of the rectified waveform of the AC voltage of the AC power supply. The power factor correction circuit according to claim 1. The control circuit includes:
A zero voltage detection circuit for detecting a zero voltage based on a voltage generated in the tertiary winding of the transformer;
A pulse width control circuit for generating the on-pulse width signal for turning on the switching element by the zero voltage detected by the zero voltage detection circuit;
The power factor correction circuit according to claim 2, further comprising: AC power supply,
A rectifier circuit for rectifying the AC voltage of the AC power source;
A transformer having a primary winding, a secondary winding and a tertiary winding;
A series circuit connected to both ends of the output of the rectifier circuit and including a primary winding and a switching element of the transformer;
A rectifying and smoothing circuit for supplying a DC voltage obtained by rectifying and smoothing a voltage generated in the secondary winding of the transformer to a load;
A current detection circuit for detecting an output current flowing through the load;
A control for generating an on-pulse width signal having a constant width based on the DC voltage of the rectifying and smoothing circuit, turning on / off the switching element by the on-pulse width signal, and controlling the output current detected by the current detection circuit to a constant value. Circuit,
A voltage detection circuit for detecting a DC voltage of the rectifying and smoothing circuit;
A time constant circuit connected to the voltage detection circuit and the control circuit and having a phase compensation resistor and a phase compensation capacitor;
The time constant of the phase compensation resistor and the phase compensation capacitor is set to have a response time that is at least 1/2 times the period of the rectified waveform of the AC voltage of the AC power supply,
The control circuit includes:
A zero voltage detection circuit for detecting a zero voltage based on a voltage generated in the tertiary winding of the transformer;
A pulse width control circuit for generating the on-pulse width signal for turning on the switching element by the zero voltage detected by the zero voltage detection circuit;
An LED lighting apparatus comprising:

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