JP2014155300A - Power supply control circuit for semiconductor lighting, semiconductor integrated circuit, and power supply for semiconductor lighting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply for semiconductor lighting which more stably drives (operates for step-down action) a step-down chopper circuit DCH.SOLUTION: The power supply for semiconductor lighting includes: an AC power supply AC; a rectification circuit REC for outputting a rectified version of an AC voltage output from the AC power supply to a power terminal and a ground terminal; a power factor correction circuit PFC for suppressing harmonics caused by the voltage output from the AC power supply; the step-down chopper circuit DCH for outputting a stepped-down version of a voltage of a first output node to a second output node; a semiconductor light emitting element EM connected between the second output node and the ground terminal; and a power supply control circuit 100 for semiconductor lighting for controlling the power factor correction circuit and the step-down chopper circuit. The power supply control circuit for semiconductor lighting starts the step-down chopper circuit after the power factor correction circuit starts operating to bring the voltage output to the first output node to not less than a set value set higher than a forward voltage of the semiconductor light emitting element.

Description

  The present invention relates to a power supply control circuit for semiconductor lighting, a semiconductor integrated circuit, and a power supply for semiconductor lighting.

  For example, a power factor correction circuit that suppresses harmonics due to a voltage output from an AC power supply, and a DC voltage output from the power factor correction circuit is stepped down and supplied to a semiconductor light emitting element (for example, an LED element). There is a semiconductor illumination power source including a step-down chopper circuit that controls a constant current to flow through a light emitting element (see, for example, Patent Document 1).

JP 2010-1113924 A

  In the conventional power supply for semiconductor illumination, the forward voltage of the semiconductor light emitting elements connected in series may be set higher than the output voltage that is full-wave rectified by the rectifier circuit.

  In this case, if the step-down chopper circuit starts operating before the power factor correction circuit, the necessary output voltage is lower than the input voltage of the step-down chopper circuit, so that there is a problem that the step-down chopper circuit cannot operate normally.

  Further, in order to drive the high-side switch element of the step-down chopper circuit, a high-side drive voltage is required. The high-side drive voltage is generated by charging a capacitor connected between the source of the high-side switch element and the high-side drive power supply. This capacitor is charged when the high-side switch element and the low-side switch element connected between the high-side switch element and the ground terminal are turned on, and charging and power control are performed by alternately turning on / off. Is called.

  Thus, the conventional step-down chopper circuit of the power supply for semiconductor illumination requires a low-side switch element.

  In addition, when starting the step-down chopper circuit, the capacitor of the soft start circuit is charged to prevent excessive current from flowing through the switch element, and the ON width of the switching element depends on the charge voltage of the capacitor until a certain threshold is reached. It is common to make it move gradually. This prevents excessive current from flowing. However, when the power factor correction circuit and the step-down chopper circuit operate simultaneously, the forward voltage of the semiconductor light emitting element (the sum of the forward voltages when a plurality of semiconductor light emitting elements are connected in series) is full-wave rectified by the rectifier circuit. When the output voltage is higher than the output voltage, the step-down chopper circuit cannot operate, but the capacitor of the soft start circuit starts charging. When the step-down chopper circuit operates at the stage where the capacitor of the soft start circuit has completed charging, the soft start circuit does not operate, an excessive current flows, stresses the switch element, and is destroyed in the worst case.

A power supply control circuit for semiconductor lighting according to an embodiment of one aspect of the present invention includes:
An AC power source, a rectifier circuit that rectifies an AC voltage output from the AC power source and outputs the rectified voltage to a power supply terminal and a ground terminal, a power factor correction circuit that suppresses harmonics due to the voltage output from the AC power source, and the first A power supply for semiconductor illumination, comprising: a step-down circuit that steps down the voltage of the output node of the first output node and outputs the step-down voltage to a second output node; and a semiconductor light emitting element connected between the second output node and the ground terminal In a power supply control circuit for semiconductor lighting that is applied to the power factor correction circuit and controls the step-down circuit,
The power supply control circuit for semiconductor lighting activates the step-down circuit after the power factor correction circuit starts operating and the voltage output to the first output node becomes equal to or higher than a preset value. And
The set value is set higher than a forward voltage of the semiconductor light emitting element.

In the semiconductor lighting power control circuit,
The set value is an input voltage required by the step-down circuit and is set higher than a forward voltage of the semiconductor light emitting element.

In the semiconductor lighting power control circuit,
A starting power supply circuit that starts when a divided power supply voltage obtained by dividing the voltage between the power supply terminal and the ground terminal is equal to or higher than a preset power supply threshold;
A PFC control circuit for controlling the switch element provided in the power factor correction circuit to drive the power factor correction circuit when the voltage output from the start-up power supply circuit exceeds a preset threshold for the power factor improvement circuit When,
A PFC output voltage detection circuit for detecting a divided voltage of the power factor correction circuit;
When the divided voltage of the power factor correction circuit detected by the PFC output voltage detection circuit reaches a threshold for a step-down circuit that is higher than a preset forward voltage of the semiconductor light emitting element, the drive of the step-down circuit is stopped. A stop circuit for canceling the requested output stop signal;
A driver circuit that drives the step-down circuit by controlling the high-side switch element and / or the low-side switch element provided in the step-down circuit when the output stop signal is released and the step-down circuit is activated. It is characterized by.

In the semiconductor lighting power control circuit,
The choke of the power factor correction circuit is provided with a secondary winding composed of a transformer, and the secondary winding is used as a power source for the high-side switch element of the step-down circuit so that the low-side switch element can be eliminated. It is characterized by that.

A semiconductor integrated circuit according to an embodiment of one aspect of the present invention includes:
The power factor correction circuit and the step-down circuit controlled by the power supply control circuit for semiconductor lighting are formed on the same semiconductor substrate.

A power source for semiconductor lighting according to an embodiment of one aspect of the present invention is:
AC power supply,
A rectifier circuit that rectifies an AC voltage output from the AC power source and outputs the rectified voltage to a power supply terminal and a ground terminal;
A power factor correction circuit that suppresses harmonics due to the voltage output from the AC power supply;
A step-down circuit for stepping down a voltage of the first output node and outputting the step-down voltage to a second output node;
A semiconductor light emitting device connected between the second output node and the ground terminal;
A power control circuit for semiconductor lighting that controls the power factor correction circuit and the step-down circuit, and
The power supply control circuit for semiconductor lighting activates the step-down circuit after the power factor correction circuit starts operating and the voltage output to the first output node becomes equal to or higher than a preset value. And
The set value is set higher than a forward voltage of the semiconductor light emitting element.

In the semiconductor lighting power source,
The power factor correction circuit is:
A winding having one end connected to the power terminal;
A switch element having one end connected to the other end of the winding;
A resistor connected between the other end of the switch element and the ground terminal;
A diode having an anode connected to the other end of the winding and a cathode connected to the first output node;
A power factor improving voltage dividing circuit for outputting a power factor improving divided voltage obtained by dividing a voltage between the first output node and the ground terminal;
And an output capacitor connected between the first output node and the ground terminal.

In the semiconductor lighting power source,
The step-down circuit is
A high-side switch element having one end connected to the first output node and the other end connected to an intermediate node;
A low-side switch element having one end connected to the intermediate node and the other end connected to the ground terminal;
A step-down diode having a cathode connected to the intermediate node and an anode connected to the ground terminal;
A primary winding having one end connected to the intermediate node and the other end connected to the second output node;
One end connected to the ground terminal, and the secondary winding constituting the transformer and the primary winding;
A first capacitor having one end connected to the intermediate node;
A first diode having an anode connected to the other end of the secondary winding;
A second diode having a cathode connected to the other end of the first capacitor and an anode connected to the cathode of the first diode;
A second capacitor having one end connected to the cathode of the first diode and the other end connected to one end of the secondary winding;
And an output capacitor connected between the second output node and the ground terminal.

In the semiconductor lighting power source,
The power factor correction circuit is:
It further has an additional winding constituting the winding and the transformer,
The step-down circuit is
A high-side switch element having one end connected to the first output node and the other end connected to one end of the additional winding;
A step-down diode having a cathode connected to one end of the additional winding and an anode connected to the ground terminal;
A primary winding having one end connected to one end of the additional winding and the other end connected to the second output node;
One end connected to the ground terminal, and the secondary winding constituting the transformer and the primary winding;
A first capacitor having one end connected to one end of the additional winding;
A first diode having an anode connected to the other end of the secondary winding;
A second diode having a cathode connected to the other end of the first capacitor and an anode connected to the other end of the additional winding;
A second capacitor having one end connected to the cathode of the first diode and the other end connected to one end of the secondary winding;
And an output capacitor connected between the second output node and the ground terminal.

In the semiconductor lighting power source,
The step-down circuit is
A resistor having one end connected to the ground terminal;
A step-down diode having a cathode connected to the first output node and the second output node;
A switching element having one end connected to the anode of the step-down diode and the other end connected to the other end of the resistor;
A primary winding having one end connected to the anode of the step-down diode;
One end connected to the ground terminal, and the secondary winding constituting the transformer and the primary winding;
A first diode having an anode connected to the other end of the secondary winding;
And an output capacitor connected between the second output node and the other end of the primary winding.

  A power source for semiconductor lighting according to one embodiment of the present invention includes an AC power source, a rectifier circuit that rectifies an AC voltage output from the AC power source and outputs the rectified voltage to a power supply terminal and a ground terminal, and harmonics generated by the voltage output from the AC power source. A power factor improving circuit for suppressing, a step-down circuit for stepping down the voltage of the first output node and outputting the voltage to the second output node, and a semiconductor light emitting element connected between the second output node and the ground terminal A power control circuit for semiconductor lighting for controlling the power factor correction circuit and the step-down circuit.

  Then, the power supply control circuit for semiconductor lighting activates the step-down circuit after the power factor correction circuit starts operating and the voltage output to the first output node becomes equal to or higher than a preset set value. Further, the set value is set higher than the forward voltage of the semiconductor light emitting element.

  Thus, since the step-down circuit operates after the output voltage of the power factor correction circuit reaches the set value, the step-down circuit can operate with a stable input voltage.

  In particular, the power factor is improved even when the forward voltage of the semiconductor light-emitting element (the sum of the forward voltages when multiple semiconductor light-emitting elements are connected in series) is higher than the output voltage that has been full-wave rectified by the rectifier circuit. The step-down circuit can be stably started immediately after the circuit operates.

  Furthermore, it is possible to prevent the step-down circuit from operating while the power factor correction circuit does not operate due to a failure or the like, that is, without suppressing harmonics.

  In addition, since the step-down circuit can operate with a stable input voltage, it is possible to prevent variations in the current flowing through the semiconductor light emitting element even if there is a delay in current feedback during soft start when the step-down circuit is activated.

  In addition, since the power factor correction circuit starts operating earlier than the step-down circuit, a high-side drive voltage can be generated using the winding of the power factor correction circuit.

  That is, when the step-down circuit is started, the high-side drive voltage is more reliably secured. Thereby, the low side switch element required for the conventional power supply control circuit for semiconductor illumination can be omitted.

FIG. 1 is a diagram illustrating an example of a configuration of a semiconductor lighting power supply 1000 according to a first embodiment which is an aspect of the present invention. FIG. 2 is a waveform diagram showing an example of operation waveforms of the semiconductor illumination power supply 1000 shown in FIG. FIG. 3 is a diagram illustrating an example of the configuration of a semiconductor lighting power supply 2000 according to the second embodiment which is an aspect of the present invention. FIG. 4 is a diagram illustrating an example of a configuration of a semiconductor lighting power supply 3000 according to the third embodiment which is an aspect of the present invention.

  Embodiments according to the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram illustrating an example of a configuration of a semiconductor lighting power supply 1000 according to a first embodiment which is an aspect of the present invention.

  As shown in FIG. 1, the power supply for semiconductor illumination 1000 includes an AC power supply AC, a rectifier circuit REC, a power supply voltage dividing circuit DC1, a power factor correction (PFC) circuit PFC, and a step-down chopper circuit DCH. A semiconductor light emitting element EM, an output resistor Rout, and a semiconductor illumination power supply control circuit 100.

  The AC power supply AC outputs an AC voltage between one end and the other end.

  The rectifier circuit REC rectifies the AC voltage output from the AC power supply AC and outputs the rectified voltage to the power supply terminal TS and the ground terminal TGND.

  For example, as shown in FIG. 1, the rectifier circuit REC includes a first rectifier diode DREC1, a second rectifier diode DREC2, a third rectifier diode DREC3, and a fourth rectifier diode DREC4. Have.

The first rectifying diode DREC1 has an anode connected to one end of the AC power supply AC and a cathode connected to the power supply terminal TS.
The second rectifying diode DREC2 has a cathode connected to one end of the AC power supply AC and an anode connected to the ground terminal TGND.
The third rectifying diode DREC3 has an anode connected to the other end of the AC power supply AC and a cathode connected to the power supply terminal TS.
The fourth rectifying diode DREC4 has a cathode connected to the other end of the AC power supply AC and an anode connected to the ground terminal TGND.
With such a configuration, the rectifier circuit REC rectifies the AC voltage output from the AC power supply AC and outputs it to the power supply terminal TS and the ground terminal TGND.

  The power supply voltage dividing circuit DC1 outputs a power supply divided voltage MULTI obtained by dividing the voltage between the power supply terminal TS and the ground terminal TGND.

  The power factor correction circuit PFC boosts the voltage of the power supply terminal TS and outputs the boosted voltage to the first output node Nout1.

  For example, as shown in FIG. 1, the power factor correction circuit PFC includes a winding Lx, a switch element CSW, a resistor R, a diode CD, a power factor correction voltage dividing circuit DC2, an output capacitor CSM1, The step-up chopper circuit is configured.

  One end of the winding Lx is connected to the power supply terminal TS.

  For example, as shown in FIG. 1, the switch element CSW is a MOS transistor that is turned on / off by a signal GD supplied from the semiconductor illumination power supply control circuit 100 to the gate. One end of the switch element CSW is connected to the other end (drain) of the winding Lx.

  The resistor R is connected between the other end (source) of the switch element CSW and the ground terminal TGND.

  The diode CD has an anode connected to the other end of the winding Lx and a cathode connected to the first output node Nout1.

  The power factor improving voltage dividing circuit DC2 outputs a power factor improving divided voltage VFB obtained by dividing the voltage between the first output node Nout1 and the ground terminal TGND.

  The output capacitor CSM1 is connected between the first output node Nout1 and the ground terminal TGND.

  The power factor correction circuit PFC performs a boost operation from the above configuration and also performs a power factor improvement operation.

  Further, as shown in FIG. 1, the step-down chopper circuit DCH steps down the voltage of the first output node Nout1 and outputs it to the second output node Nout2.

  As shown in FIG. 1, for example, the step-down chopper circuit DCH includes a high-side switch element HSW, a low-side switch element LSW, a step-down diode AD, a primary winding Lx1, a secondary winding Lx2, A first diode D1, a second diode D2, a first capacitor C1, a second capacitor C2, and an output capacitor CSM2.

For example, as shown in FIG. 1, the high-side switch element HSW is a MOS transistor whose signal HO is supplied to the gate from the semiconductor illumination power supply control circuit 100 to be turned on / off. The high side switch element HSW has one end (drain) connected to the first output node Nout1, and the other end (source) connected to the intermediate node NM.
The low-side switch element LSW is, for example, as shown in FIG. 1, a MOS transistor that is turned on / off by supplying a signal LO to the gate from the semiconductor illumination power supply control circuit 100. The low side switch element LSW has one end (drain) connected to the intermediate node NM and the other end (source) connected to the ground terminal TGND.

  The step-down diode AD has a cathode connected to the intermediate node NM and an anode connected to the ground terminal TGND.

  The primary winding Lx1 has one end connected to the intermediate node NM and the other end connected to the second output node Nout2.

  One end of the secondary winding Lx2 is connected to the ground terminal TGND. The secondary winding Lx2 forms a transformer Tx with the primary winding Lx1.

  One end of the first capacitor C1 is connected to the intermediate node NM.

  The first diode D1 has an anode connected to the other end of the secondary winding Lx2.

  The second diode D2 has a cathode connected to the other end of the first capacitor C1, and an anode connected to the cathode of the first diode D1.

  The anode of the second diode D2 is supplied with a control power supply voltage Vcc from the semiconductor illumination power supply control circuit 100 when the step-down chopper circuit DCH is started. The first capacitor C1 is charged by the control power supply voltage Vcc, and a high side drive voltage is generated.

  The second capacitor C2 has one end connected to the cathode of the first diode D1, and the other end connected to one end of the secondary winding Lx2.

  The step-down output capacitor CSM2 is connected between the second output node Nout2 and the ground terminal TGND.

  The step-down chopper circuit DCH is configured to perform a step-down operation with the above configuration.

  The control power supply voltage Vcc is generated by this step-down operation.

  In addition, the semiconductor light emitting element EM is connected between the second output node Nout2 and the ground terminal TGND. In particular, in the example of FIG. 1, a plurality (three in this case) of semiconductor light emitting devices EM are connected in series between the second output node Nout2 and the ground terminal TGND.

  For example, as shown in FIG. 1, the semiconductor light emitting element EM is an LED element or an organic EL element having an anode connected to the second output node Nout2 and a cathode connected to the ground terminal TGND.

  As shown in FIG. 1, the output resistor Rout is connected between the semiconductor light emitting element EM and the ground terminal TGND.

  The semiconductor illumination power supply control circuit 100 is a circuit applied to the semiconductor illumination power supply 1000 as described above. The semiconductor lighting power supply control circuit 100 controls the power factor correction circuit PFC and the step-down chopper circuit DCH.

  In particular, the power supply control circuit 100 for semiconductor lighting uses the step-down chopper circuit after the power factor correction circuit PFC starts operating and the voltage output to the first output node Mout1 becomes equal to or higher than a preset set value. It is designed to start up.

  The set value described above is an input voltage required by the step-down chopper circuit DCH and is set higher than the forward voltage of the semiconductor light emitting element EM. Further, as described above, the present invention assumes a setting in which the forward voltage of the semiconductor light emitting element EM is higher than the output voltage that is full-wave rectified by the rectifier circuit REC.

  In particular, the set value described above is stepped down when the set value Nout1 of the output voltage of the power factor correction circuit PFC is set higher than the forward voltage of the semiconductor light emitting element EM and sufficiently exceeds the set value of the semiconductor light emitting element EM. The circuit DCH is activated.

  That is, the step-down chopper circuit DCH can be driven more stably (step-down operation) more reliably.

  As described above, in the example of FIG. 1, a plurality (three in this case) of semiconductor light emitting elements EM are connected in series between the second output node Nout2 and the ground terminal TGND. In this case, the set value is set higher than the sum of forward voltages of a plurality (here, three) of semiconductor light emitting elements EM.

  Here, for example, as shown in FIG. 1, the power supply control circuit 100 for semiconductor lighting includes a start-up power supply circuit SC, a PFC control circuit PCC, a PFC output voltage detection circuit VDC, an input power failure detection circuit BDS, and a stop. The circuit SPC includes a driver circuit DR, a current detection circuit IDC, an oscillator OSC, a malfunction prevention circuit UVLO, a comparator COM, a control unit CONT, and a soft start circuit SSC.

  The above-described control power supply voltage Vcc is also supplied as the power supply voltage of each of the above components of the semiconductor lighting power supply control circuit 100.

  The input power failure detection circuit BDS detects the power supply divided voltage MULTI generated in the power supply voltage dividing circuit DC1.

  When the input power failure detection circuit BDS detects the divided power supply voltage MULTI and the divided power supply voltage MULTI is equal to or higher than a preset power supply threshold Vtha, that is, the voltage supplied to the power factor correction circuit PFC is When the voltage exceeds a predetermined value, the startup power supply circuit SC starts up and supplies the control power supply voltage Vcc.

  The PFC control circuit PCC controls the switch element CSW by the signal GD to control the power factor improvement circuit PFC when the control power supply voltage Vcc output from the startup power supply circuit SC becomes equal to or higher than a preset power factor improvement circuit threshold Vthb. Is supposed to be driven.

  In the power factor correction circuit PFC, when the switch element CSW is on, energy is accumulated in the winding Lx by the output voltage from the rectifier circuit REC. When the switch element CSW is turned off, the energy accumulated in the winding Lx is changed. The output voltage of the corresponding power factor correction circuit PFC and the output voltage from the rectifier circuit REC are added. The added DC voltage is smoothed by the capacitor CSM1 and output to the step-down chopper circuit DCH. The voltage is controlled by detecting the power factor improving divided voltage VFB.

  The PFC output voltage detection circuit VDC detects the power factor improving divided voltage VFB generated by the power factor improving voltage dividing circuit DC2 by another step-down circuit threshold Vthc.

  The driver circuit DR drives the step-down chopper circuit DCH by controlling the high-side switch element HSW and the low-side switch element LSW with the signals HO and LO.

  In particular, for a step-down circuit that is higher than a forward voltage of a preset semiconductor light emitting element EM that is lower than a threshold value of a voltage that is detected by the PFC output voltage detection circuit VDC and detected by the PFC control circuit. When the threshold value Vthc is reached, a signal is transmitted to the stop circuit SPC, the current output stop signal requesting the stop from the stop circuit SPC is released, and the driver circuit DR of the step-down chopper circuit is started and turned on from the low side switch LSW To start. As a result, one end of the first capacitor C1 is grounded, and the first capacitor C1 is charged from the control power supply voltage Vcc via the second diode D2. As a result, a high-side drive voltage HVcc (a voltage across the first capacitor C1) is secured.

  The step-down chopper circuit DCH is driven by alternately controlling the high-side switch element HSW and the low-side switch element LSW, and constant current control is performed by changing the on-duty of the high-side switch element HSW in one example of the embodiment. Do. When the high-side switch element HSW is on and the low-side switch element LSW is off, energy is accumulated in the primary winding Lx1 of the transformer Tx by the DC voltage output from the power factor correction circuit PFC, and this DC voltage Is made constant, the energy of the primary winding Lx1 is regenerated through AD and output to the semiconductor light emitting device EM when the high side switch element HSW is off and the low side switch LSW is on. . Thereby, the semiconductor light emitting element EM emits light.

  The current detection circuit IDC detects a current flowing through the semiconductor light emitting element EM, and outputs a current detection signal corresponding to the detection result.

  The oscillator OSC outputs an oscillation signal SF.

  The comparator COM compares the oscillation signal SF with the current detection signal and outputs a comparison signal corresponding to the comparison result.

  Based on the comparison signal output from the comparator COM, the control unit CONT drives the high-side switch element HSW and the low-side switch element LSW by the driver circuit DR so that the current flowing through the semiconductor light emitting element EM becomes a target current value. Control.

  For example, when the control unit CONT determines that the current flowing through the semiconductor light emitting element EM is less than the target current value based on the comparison signal, the on-duty of the high-side switch element HSW becomes small and the on-duty of the low-side switch element LSW Is controlled to be large.

  On the other hand, when the control unit CONT determines that the current flowing through the semiconductor light emitting element EM is equal to or greater than the target current value based on the comparison signal, the on-duty of the high-side switch element HSW becomes small and the on-duty of the low-side switch element LSW Is controlled to be large.

  As a result, the output voltage between the second output node Nout2 of the step-down chopper circuit DHC and the ground terminal TGND is controlled to be the target voltage value described above. This is a case of a PWM (pulse wide modulation) system with a fixed frequency generated by the oscillator OSC shown in the embodiment, and a current critical type step-down circuit as shown in FIG. 4 may be used.

  The stop circuit SPC uses the drive gate signal GD of the PFC control circuit PCC, the control operation of the driver circuit DR, and the oscillator OSC when the divided power supply voltage MULTI detected by the input power failure detection circuit BDS is less than the power supply threshold Vtha. The output of the oscillation signal SF is stopped.

  On the other hand, the stop circuit SPC cancels the control operation stop of the drive gate signal GD of the PFC control circuit PCC when the power supply divided voltage MULTI detected by the input power failure detection circuit BDS is equal to or higher than the power supply threshold Vtha. It has become. Further, the stop circuit SPC has a power factor improvement divided voltage VFB detected by the PFC output voltage detection circuit VDC equal to or higher than a preset step-down chopper circuit threshold Vthc (that is, the power factor improvement circuit RFC outputs the first output). When the voltage output to the node Mout1 is equal to or higher than a preset value, the output of the oscillation signal SF by the oscillator OSC and the stop of the driver circuit DR are released.

  The malfunction prevention circuit UVLO controls the stop circuit SPC to stop the control operation of the PFC control circuit PCC and the driver circuit DR and the output of the oscillation signal SF by the oscillator OSC when the control power supply voltage Vcc is less than a predetermined value. It has become.

  Further, the soft start circuit SSC outputs a signal for controlling the on-duty of the high-side switch element HSW and the low-side switch element LSW to the control unit CONT so that the soft-start circuit SSC soft-starts when the step-down chopper circuit DCH is activated. ing.

  Next, an example of the operation of the semiconductor illumination power supply control circuit 100 in the semiconductor illumination power supply 1000 having the above-described configuration will be described.

  FIG. 2 is a waveform diagram showing an example of operation waveforms of the semiconductor illumination power supply 1000 shown in FIG.

  For example, as shown in FIG. 2, the voltage supplied between the power supply terminal TS and the ground terminal TGND increases due to the operation of the AC power supply AC before the time t1. As a result, the power supply divided voltage MULTI output from the power supply voltage dividing circuit DC1 increases.

  After that, when the divided power supply voltage MULTI detected by the input power failure detection circuit BDS becomes equal to or higher than a preset power supply threshold value Vtha (time t1), the activation power supply circuit SC is activated, and a voltage is applied to the control power supply voltage Vcc. Supply.

  After that, at time t2 when the control power supply voltage Vcc rises, the PFC control circuit PCC controls the switch element CSW by the signal GD when the power factor improvement circuit threshold Vthb or more is reached to control the power factor improvement circuit PFC. Drive.

  In the power factor correction circuit PFC, when the switch element CSW is on, energy is accumulated in the winding Lx by the output voltage from the rectifier circuit REC. When the switch element CSW is turned off, the energy accumulated in the winding Lx is changed. The output voltage of the corresponding power factor correction circuit PFC and the output voltage from the rectifier circuit REC are added. The added DC voltage is smoothed by the capacitor CSM1 and output to the step-down chopper circuit DCH. The control of the output voltage is fed back by a power factor improving divided voltage terminal VFB and boosted to a predetermined voltage.

  Thereafter, at time t3 in the middle of being controlled to a predetermined boosted voltage, the power factor improving divided voltage VFB generated by the power factor improving voltage dividing circuit DC2 detected by the PFC output voltage detecting circuit VDC is preset. When the step-down chopper circuit threshold Vthc is exceeded (that is, the voltage output from the power factor correction circuit RFC to the first output node Mout1 is equal to or higher than a preset set value), the output of the oscillation signal SF by the oscillator OSC is started. The driver circuit DR is activated.

  Accordingly, the control unit CONT controls the driver circuit DR based on the comparison signal output from the comparator COM so that the current flowing through the semiconductor light emitting element EM becomes the target current value.

  Then, the driver circuit DR starts to be turned on from the low side switch LSW. As a result, one end of the first capacitor C1 is grounded, and the first capacitor C1 is charged from the control power supply voltage Vcc via the second diode D2. As a result, the high-side drive voltage HVcc (the voltage across C1) is secured. Then, by controlling the high-side switch element HSW and the low-side switch element LSW with the signals HO and LO, the step-down chopper circuit DCH is driven, and the constant current control is performed by changing the PWM on-duty.

  When the high-side switch element HSW is on and the low-side switch element LSW is off, energy is accumulated in the primary winding Lx1 of the transformer Tx by the DC voltage output from the power factor correction circuit PFC, and the high-side switch element HSW When the low side switch LSW is off and the energy of the primary winding Lx1 of the transformer Tx is regenerated through AD, this DC voltage is made constant by the current detection circuit IDC and output to the semiconductor light emitting device EM. Is done. Thereby, the semiconductor light emitting device EM emits light.

  As described above, the voltage output from the power factor correction circuit RFC to the first output node Mout1 by the operation of the semiconductor lighting power supply control circuit 100 is the target voltage value of the output voltage of the step-down chopper circuit DCH. After that, the step-down chopper circuit DCH is started.

  That is, the step-down chopper circuit DCH can be driven more stably (step-down operation) more reliably.

  As described above, the semiconductor lighting power supply 100 according to the first embodiment includes the AC power supply AC, the rectifier circuit REC that rectifies the AC voltage output from the AC power supply AC and outputs the rectified voltage to the power supply terminal TS and the ground terminal TGND. A power factor correction circuit PFC that suppresses harmonics due to a voltage output from the AC power supply AC, a step-down chopper circuit DCH that steps down the voltage of the first output node Nout1 and outputs the voltage to the second output node Nout2, and a second A semiconductor light emitting device EM connected between the output node Nout2 and the ground terminal TGND, and a semiconductor lighting power control circuit 100 for controlling the power factor correction circuit PFC and the step-down chopper circuit DCH are provided.

  Then, the power supply control circuit 100 for semiconductor illumination starts the step-down chopper circuit DCH after the power factor correction circuit PFC starts operating and the voltage output to the first output node Nout1 exceeds a preset value. Start. Further, the set value is set higher than the forward voltage of the semiconductor light emitting element EM.

  Thus, since the step-down chopper circuit DCH operates after the output voltage of the power factor correction circuit PFC reaches the set value, the step-down chopper circuit DCH can operate with a stable input voltage.

  In particular, even when the forward voltage of the semiconductor light emitting device EM (the sum of the forward voltages when a plurality of semiconductor light emitting devices EM are connected in series) is higher than the output voltage that is full-wave rectified by the rectifier circuit REC, The step-down chopper circuit DCH can be stably started immediately after the power factor correction circuit PFC operates.

  Furthermore, it is possible to prevent the step-down chopper circuit DCH from operating while the power factor correction circuit PFC does not operate due to a failure or the like, that is, without suppressing harmonics.

  Further, since the step-down chopper circuit DCH can operate at a stable input voltage, even if there is a delay in current feedback at the time of soft start at the time of starting the step-down chopper circuit DCH, variation in the current flowing through the semiconductor light emitting element EM is prevented. be able to.

  When the step-down chopper circuit DCH is started, the capacitor of the soft start circuit SSC is charged in order to prevent an excessive current from flowing through the high-side switch element HSW and the low-side switch element LSW. In general, the switch element HSW and the low-side switch element LSW are operated to gradually widen the ON width according to the charging voltage of the capacitor. This prevents excessive current from flowing. However, if the power factor correction circuit PFC and the step-down chopper circuit DCH are operated simultaneously, the forward voltage of the semiconductor light emitting element EM (a plurality of semiconductor light emitting elements are connected in series). If the sum of these forward voltages is higher than the output voltage that has been full-wave rectified by the rectifier circuit, the step-down chopper circuit DCH cannot operate, so there is no output, but the capacitor of the soft start circuit SSC starts charging. Resulting in. When the step-down chopper circuit DCH operates at the stage where the capacitor of the soft start circuit SSC has completed charging, the soft start circuit SSC does not operate and excessive current flows, causing stress on the high side switch element HSW and the low side switch element LSW. Can be prevented from being destroyed in the worst case.

  FIG. 3 is a diagram illustrating an example of the configuration of a semiconductor lighting power supply 2000 according to the second embodiment which is an aspect of the present invention. 3, the same reference numerals as those in FIG. 1 indicate the same configurations as those in the first embodiment.

  As shown in FIG. 3, the semiconductor lighting power source 2000 includes an AC power source AC, a rectifier circuit REC, a power source voltage dividing circuit DC1, a power factor correction circuit PFC, a step-down chopper circuit DCH, and a semiconductor light emitting device EM. , An output resistor Rout, and a power supply control circuit 100 for semiconductor illumination.

  For example, as shown in FIG. 3, the power factor correction circuit PFC includes a winding Lx, a switch element CSW, a resistor R, a diode CD, a power factor correction voltage dividing circuit DC2, and an output capacitor CSM1. , An additional winding Ly, and a PFC boost chopper circuit.

  That is, the power factor correction circuit PFC further includes an additional winding Ly as compared with the first embodiment.

  Here, the additional winding Ly constitutes the winding Lx and the transformer Ty.

  Other configurations of the power factor correction circuit PFC are the same as those of the power factor correction circuit PFC of the semiconductor lighting power supply 1000 according to the first embodiment shown in FIG.

  As shown in FIG. 3, the step-down chopper circuit DCH includes a high-side switch element HSW, a step-down diode AD, a primary winding Lx1, a secondary winding Lx2, a first diode D1, Two diodes D2, a first capacitor C1, a second capacitor C2, and an output capacitor CSM2.

That is, in the step-down chopper circuit DCH, the low-side switch element LSW is omitted as compared with the first embodiment.
Here, the high side switch element HSW has one end (drain) connected to the first output node Nout1, and the other end (source) connected to one end of the additional winding Ly.

  The step-down diode AD has a cathode connected to one end of the additional winding Ly, and an anode connected to the ground terminal TGND.

  The primary winding Lx1 has one end connected to one end of the additional winding Ly and the other end connected to the second output node Nout2.

  The secondary winding Lx2 has one end connected to the ground terminal TGND, and constitutes the transformer Tx with the primary winding Lx1.

  One end of the first capacitor C1 is connected to one end of the additional winding Ly.

  The first diode D1 has an anode connected to the other end of the secondary winding Lx2.

  The second diode D2 has a cathode connected to the other end of the first capacitor C1, and an anode connected to the other end of the additional winding Ly.

  The second capacitor C2 has one end connected to the cathode of the first diode D1, and the other end connected to one end of the secondary winding Lx2.

  The output capacitor CSM2 is connected between the second output node Nout2 and the ground terminal TGND.

  The step-down chopper circuit DCH is configured to perform a step-down operation with the above configuration.

  By this step-down operation, the control power supply voltage Vcc is generated from the configuration of the secondary winding Lx2, the first diode D1, and the second capacitor C2.

  Other configurations of the step-down chopper circuit DCH are the same as those of the step-down chopper circuit DCH of the semiconductor illumination power source 1000 according to the first embodiment shown in FIG.

  The other configuration of the semiconductor illumination power source 2000 is the same as that of the semiconductor illumination power source 1000 according to the first embodiment shown in FIG.

  The operation of the semiconductor illumination power supply control circuit 100 in the semiconductor illumination power supply 2000 having the above-described configuration is the same as that of the first embodiment.

  That is, as in the first embodiment, since the step-down chopper circuit DCH operates after the output voltage of the power factor correction circuit PFC reaches the set value, the step-down chopper circuit DCH can operate with a stable input voltage.

  In particular, since the power factor correction circuit PFC starts operating earlier than the step-down chopper circuit DCH, in the second embodiment, the winding (additional winding Ly) of the power factor correction circuit PFC is used to It is possible to generate a voltage HVcc for charging both ends of one capacitor C1, that is, for driving the high-side drive of the step-down chopper circuit DCH. That is, the power factor correction circuit PFC surely operates first before the step-down chopper circuit DCH operates. As a result, when the step-down chopper circuit DCH is activated, the high-side drive voltage is more reliably ensured without the low-side switch element LSW. In the case of FIG. 1, the low-side switch element LSW is turned on, one end of the first capacitor C1 is grounded, and the first capacitor C1 is charged from the control power supply voltage Vcc through the second diode D2 for the first time. That is no longer necessary. Therefore, the low side switch element LSW can be omitted.

  FIG. 4 is a diagram illustrating an example of a configuration of a semiconductor lighting power supply 3000 according to the third embodiment which is an aspect of the present invention. 4, the same reference numerals as those in FIG. 1 indicate the same configurations as those in the first embodiment.

  As shown in FIG. 4, the semiconductor lighting power supply 3000 includes an AC power supply AC, a rectifier circuit REC, a power supply voltage dividing circuit DC1, a power factor correction circuit PFC, a step-down chopper circuit DCH, and a semiconductor light emitting device EM. , An output resistor Rout, and a semiconductor illumination power supply control circuit 300.

  As shown in FIG. 4, the step-down chopper circuit DCH includes a switch element SW, a step-down diode AD, a primary winding Lx1, a secondary winding Lx2, a first diode D1, and a second diode It has a diode D2, a first capacitor C1, a second capacitor C2, an output capacitor CSM2, and a resistor Rx.

  That is, in the step-down chopper circuit DCH, the high-side switch element HSW and the second diode D2 are omitted and a resistor Rx is added as compared with the first embodiment. Note that the switch element SW corresponds to the low-side switch element LSW of the first embodiment described above.

  Here, one end of the resistor Rx is connected to the ground terminal TGND.

  The step-down diode AD has a cathode connected to the first output node Nout1 and the second output node Nout2.

  The switch element SW has one end (drain) connected to the anode of the step-down diode AD and the other end (source) connected to the other end of the resistor Rx.

  The primary winding Lx1 has one end connected to the anode of the step-down diode AD.

  The secondary winding Lx2 has one end connected to the ground terminal TGND, and constitutes the transformer Tx with the primary winding Lx1.

  The first diode D1 has an anode connected to the other end of the secondary winding Lx2.

  The output capacitor CSM2 is connected between the second output node Nout2 and the other end of the primary winding Lx1.

  The step-down chopper circuit DCH is configured to perform a step-down operation with the above configuration.

  By this step-down operation, the control power supply voltage Vcc is generated from the secondary winding Lx2 and the first diode D1.

  The semiconductor illumination power supply control circuit 300 is a circuit applied to the semiconductor illumination power supply 3000 as in the first embodiment. The semiconductor illumination power supply control circuit 300 controls the power factor correction circuit PFC and the step-down chopper circuit DCH.

  In particular, in the power supply control circuit 300 for semiconductor lighting, as in the first embodiment, the voltage output from the power factor correction circuit RFC and output to the first output node Mout1 is equal to or higher than a preset set value. After that, the step-down chopper circuit DHC is started.

  Note that the set value described above is set higher than the forward voltage of the semiconductor light emitting element EM, as in the first embodiment. Further, as described above, in this embodiment, it is assumed that the forward voltage of the semiconductor light emitting element EM is set higher than the output voltage that is full-wave rectified by the rectifier circuit.

  In particular, the set value is set to a value higher than the target voltage value of the output voltage output from the step-down chopper circuit DCH to the second output node Nout2.

  Thus, as in the first embodiment, after the power factor correction circuit RFC starts operating and the voltage output to the first output node Mout1 becomes equal to or higher than the target voltage value of the output voltage of the step-down chopper circuit DCH, The step-down chopper circuit DCH is activated.

  That is, the step-down chopper circuit DCH can be driven more stably (step-down operation) more reliably.

  Here, for example, as shown in FIG. 3, the power supply control circuit 300 for semiconductor lighting includes a start-up power supply circuit SC, a PFC control circuit PCC, a PFC output voltage detection circuit VDC, and an input power failure detection circuit BDS. The circuit includes a circuit SPC, a driver circuit DR, a malfunction prevention circuit UVLO, a control unit CONT, a soft start circuit SSC, a peak current detection circuit PDC, and a zero current detection circuit ZDC.

  The peak current detection circuit PDC detects the peak current flowing through the other end of the step-down resistor Rx.

  The zero current detection circuit ZDC detects a current flowing through the cathode of the first diode D1 (that is, the secondary winding Lx2).

  The driver circuit DR drives the step-down chopper circuit DCH by controlling the switch element SW with the signal LO.

  In particular, the driver circuit DR determines that the power factor improving divided voltage VFB detected by the PFC output voltage detecting circuit VDC is equal to or higher than a preset step-down chopper circuit threshold Vthc (that is, the power factor improving circuit RFC is When the voltage output to the first output node Mout1 is equal to or higher than a preset setting value), the step-down chopper circuit DCH is driven by controlling the switch element SW.

  For example, the driver circuit DR turns off the switch element SW when the value of the current detected by the peak current detection circuit PDC becomes equal to or greater than a preset current threshold value (peak value). When the switch element SW is turned off, the current stored in the primary winding Lx1 is regenerated through the step-down diode AD.

  Thereafter, the driver circuit DR turns on the switch element SW when the zero current detection circuit ZDC detects that the current flowing through the cathode of the first diode D1 (ie, the secondary winding Lx2) has become zero. To do.

  By repeating ON / OFF of the switch element SW as described above, a current averaged with respect to the set peak current of the switch element SW is supplied to the semiconductor light emitting element EM.

  The other configuration of the semiconductor illumination power supply 3000 is the same as that of the semiconductor illumination power supply 1000 according to the first embodiment shown in FIG.

  Other operations of the semiconductor illumination power supply control circuit 300 in the semiconductor illumination power supply 3000 having the above-described configuration are the same as those in the first embodiment.

  That is, as in the first embodiment, since the step-down chopper circuit DCH operates after the output voltage of the power factor correction circuit PFC reaches the set value, the step-down chopper circuit DCH can operate with a stable input voltage.

  In particular, in the third embodiment, as described above, the high side switch element HSW can be omitted.

  The examples are illustrative and the scope of the invention is not limited thereto. In particular, the power supply control circuits 100 and 300 for semiconductor lighting can be formed on the same semiconductor substrate to be integrated. Further, although the step-down chopper circuit DCH is used as the step-down circuit, for example, a current resonance type DC / DC converter may be used.

100, 300 Semiconductor lighting power supply control circuit 1000, 2000, 3000 Semiconductor lighting power supply AC AC power supply REC Rectifier circuit DC1 Power supply voltage dividing circuit PFC Power factor correction (PFC) circuit DCH Step-down chopper circuit EM Semiconductor light emitting device DREC1 First rectifier diode DREC2 Second rectifier diode DREC3 Third rectifier diode DREC4 Fourth rectifier diode Lx Winding CSW Switch element R Resistance CD Diode DC2 Power factor improving voltage dividing circuit CSM1 Output capacitor HSW High-side switch element LSW Low-side switch element SW Switch element AD Step-down diode Lx1 Primary winding Lx2 Secondary winding D1 First diode D2 Second diode C1 First capacitor C2 First Capacitor CSM2 Output capacitor Rout Output resistance SC Start-up power supply circuit PCC PFC control circuit VDC PFC output voltage detection circuit BDS Input power failure detection circuit SPC Stop circuit DR Driver circuit IDC Current detection circuit OSC Oscillator UVLO Malfunction prevention circuit COM Comparator CONT Control unit SSC Software Start circuit

Claims (11)

An AC power source, a rectifier circuit that rectifies an AC voltage output from the AC power source and outputs the rectified voltage to a power supply terminal and a ground terminal, a power factor correction circuit that suppresses harmonics due to the voltage output from the AC power source, and the first A power supply for semiconductor illumination, comprising: a step-down circuit that steps down the voltage of the output node of the first output node and outputs the step-down voltage to a second output node; and a semiconductor light emitting element connected between the second output node and the ground terminal In a power supply control circuit for semiconductor lighting that is applied to the power factor correction circuit and controls the step-down circuit,
The power supply control circuit for semiconductor lighting activates the step-down circuit after the power factor correction circuit starts operating and the voltage output to the first output node becomes equal to or higher than a preset value. And
The set value is set to be higher than a forward voltage of the semiconductor light emitting element. A power supply control circuit for semiconductor illumination, wherein: The power supply control circuit for semiconductor lighting according to claim 1, wherein the set value is set to an input voltage required by the step-down circuit and higher than a forward voltage of the semiconductor light emitting element. A plurality of the semiconductor light emitting elements are connected in series between the second output node and the ground terminal,
The power supply control circuit for semiconductor illumination according to claim 2, wherein the set value is set higher than a sum of forward voltages of the plurality of semiconductor light emitting elements. A starting power supply circuit that starts when a divided power supply voltage obtained by dividing the voltage between the power supply terminal and the ground terminal is equal to or higher than a preset power supply threshold;
A PFC control circuit for controlling the switch element provided in the power factor correction circuit to drive the power factor correction circuit when the voltage output from the start-up power supply circuit exceeds a preset threshold for the power factor improvement circuit When,
A PFC output voltage detection circuit for detecting a divided voltage of the power factor correction circuit;
When the divided voltage of the power factor correction circuit detected by the PFC output voltage detection circuit reaches a threshold for a step-down circuit that is higher than a preset forward voltage of the semiconductor light emitting element, the drive of the step-down circuit is stopped. A stop circuit for canceling the requested output stop signal;
A driver circuit that drives the step-down circuit by controlling the high-side switch element and / or the low-side switch element provided in the step-down circuit when the output stop signal is released and the step-down circuit is activated. The power supply control circuit for semiconductor lighting according to claim 1. The choke of the power factor correction circuit is provided with a secondary winding composed of a transformer, and the secondary winding is used as a power source for the high-side switch element of the step-down circuit so that the low-side switch element can be eliminated. The power supply control circuit for semiconductor lighting according to claim 4, wherein: The semiconductor integrated circuit, wherein the power factor correction circuit and the step-down circuit controlled by the power supply control circuit for semiconductor lighting according to claim 1 are formed on the same semiconductor substrate. AC power supply,
A rectifier circuit that rectifies an AC voltage output from the AC power source and outputs the rectified voltage to a power supply terminal and a ground terminal;
A power factor correction circuit that suppresses harmonics due to the voltage output from the AC power supply;
A step-down circuit for stepping down a voltage of the first output node and outputting the step-down voltage to a second output node;
A semiconductor light emitting device connected between the second output node and the ground terminal;
A power control circuit for semiconductor lighting that controls the power factor correction circuit and the step-down circuit, and
The power supply control circuit for semiconductor lighting activates the step-down circuit after the power factor correction circuit starts operating and the voltage output to the first output node becomes equal to or higher than a preset value. And
The power supply for semiconductor illumination, wherein the set value is set higher than a forward voltage of the semiconductor light emitting element. The power factor correction circuit is:
A winding having one end connected to the power terminal;
A switch element having one end connected to the other end of the winding;
A resistor connected between the other end of the switch element and the ground terminal;
A diode having an anode connected to the other end of the winding and a cathode connected to the first output node;
A power factor improving voltage dividing circuit for outputting a power factor improving divided voltage obtained by dividing a voltage between the first output node and the ground terminal;
The power supply for semiconductor lighting according to claim 7, further comprising: an output capacitor connected between the first output node and the ground terminal. The step-down circuit is
A high-side switch element having one end connected to the first output node and the other end connected to an intermediate node;
A low-side switch element having one end connected to the intermediate node and the other end connected to the ground terminal;
A step-down diode having a cathode connected to the intermediate node and an anode connected to the ground terminal;
A primary winding having one end connected to the intermediate node and the other end connected to the second output node;
One end connected to the ground terminal, and the secondary winding constituting the transformer and the primary winding;
A first capacitor having one end connected to the intermediate node;
A first diode having an anode connected to the other end of the secondary winding;
A second diode having a cathode connected to the other end of the first capacitor and an anode connected to the cathode of the first diode;
A second capacitor having one end connected to the cathode of the first diode and the other end connected to one end of the secondary winding;
The power supply for semiconductor lighting according to claim 7, further comprising: an output capacitor connected between the second output node and the ground terminal. The power factor correction circuit is:
It further has an additional winding constituting the winding and the transformer,
The step-down circuit is
A high-side switch element having one end connected to the first output node and the other end connected to one end of the additional winding;
A step-down diode having a cathode connected to one end of the additional winding and an anode connected to the ground terminal;
A primary winding having one end connected to one end of the additional winding and the other end connected to the second output node;
One end connected to the ground terminal, and the secondary winding constituting the transformer and the primary winding;
A first capacitor having one end connected to one end of the additional winding;
A first diode having an anode connected to the other end of the secondary winding;
A second diode having a cathode connected to the other end of the first capacitor and an anode connected to the other end of the additional winding;
A second capacitor having one end connected to the cathode of the first diode and the other end connected to one end of the secondary winding;
The power supply for semiconductor lighting according to claim 7, further comprising: an output capacitor connected between the second output node and the ground terminal. The step-down circuit is
A resistor having one end connected to the ground terminal;
A step-down diode having a cathode connected to the first output node and the second output node;
A switching element having one end connected to the anode of the step-down diode and the other end connected to the other end of the resistor;
A primary winding having one end connected to the anode of the step-down diode;
One end connected to the ground terminal, and the secondary winding constituting the transformer and the primary winding;
A first diode having an anode connected to the other end of the secondary winding;
The power supply for semiconductor lighting according to claim 10, further comprising: an output capacitor connected between the second output node and the other end of the primary winding.

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