JP6619238B2 - Auxiliary power supply circuit and switching power supply device including the same - Google Patents

Description

  The present invention relates to a lighting device for controlling lighting of a light emitting device such as a light emitting diode (hereinafter referred to as “LED (Light Emitting Diode)”), and other switching power supply devices, and more particularly to operating a control circuit of the switching power supply device. The present invention relates to an improvement of an auxiliary power supply circuit that supplies a control voltage.

In recent years, the performance of LED elements has increased, and lighting fixtures using LED elements are being used in place of conventional light sources because of their long life. If the performance of LED elements is further improved in the future, it is considered that lighting fixtures using LED elements will be adopted in the field of general-purpose lighting fixtures.
In a lighting fixture using a large number of LED elements, there is no structural limitation due to the shape of the lamp as compared with a lighting fixture using a conventional HID lamp, and a lighting fixture having a free lamp shape is realized. Moreover, although the light output per LED element is small, if it is a lighting fixture which combined many LED elements in series-parallel, light output will become large. For these reasons, conventional HID lamps are replaced by lighting fixtures using LEDs.

Japanese Utility Model Publication No. 6-7197

Unlike conventional HID lamps, there is no global standard in the field of lighting fixtures using LED elements, and a number of independent vendors can combine various LED elements in series and parallel to provide various lighting fixtures. Is manufacturing. Since the voltage and current to be applied to the light emitting device composed of a plurality of LED elements vary, it is necessary to develop a lighting device for each lighting fixture. In other words, general-purpose products cannot be used for coils, transformers, etc., and it is necessary to redesign the choke coil, flyback transformer, etc. of the power factor correction circuit each time a new lighting device is developed.
In addition, the control power used in the LED lighting device is often taken out from the lighting power. In general, from the viewpoint of reducing the number of parts, a method is adopted in which a winding is added to a choke coil or flyback transformer of a power factor correction circuit (PFC) and control power is extracted from this winding. The However, as described above, since general-purpose products cannot be used for coils, transformers, etc., the lighting device must be redesigned from the beginning, including the winding for control power, and the delivery time is delayed. There was a problem.

  The lighting device of Patent Document 1 discloses a transformerless auxiliary power supply circuit that does not use a conventional winding as an auxiliary power supply circuit that extracts control power from the lighting power. However, in the auxiliary power supply circuit of Patent Document 1, when the light amount is narrowed down by the dimming operation, the control voltage is too low, and the operation of the control circuit stops or becomes unstable. There was a point.

  The present invention has been made in view of the above-described problems, and in a switching power supply device such as a lighting device, control power can be supplied without using a power transformer, and the output to the load side is narrowed down. Another object of the present invention is to provide an auxiliary power supply circuit capable of stably supplying control power, and a switching power supply device including the auxiliary power supply circuit.

  The inventor connects a first insulation capacitor to a high-potential side output terminal of a half-bridge circuit via a current-limiting inductor in a switching power supply device including a half-bridge circuit that converts a DC voltage into a high-frequency voltage. -A second insulation capacitor is connected to the low potential side output terminal of the bridge circuit, and the high frequency current generated in the pair of insulation capacitors is output to the load side. A rectifier circuit that connects a high-frequency current bypass capacitor to a connection point (point c) between the current-limiting inductor and the first insulation capacitor, steps down the output voltage of the current-limiting inductor, and further rectifies the stepped-down voltage. Was established. A DC power supply based on this rectified voltage was used as a power supply for the control circuit. By employing such an auxiliary power supply circuit including a bypass capacitor (a high-frequency current bypass circuit) and a rectifier circuit in a switching power supply device having the above-described half-bridge circuit, the problem of the present invention has been solved. Furthermore, it has been found that the output voltage of the auxiliary power supply circuit can be adjusted by configuring the bypass capacitor with a series circuit of two capacitors and adding an on / off function of the operation of the bypass capacitor.

That is, the auxiliary power circuit according to the present invention is
A half bridge circuit having a first switch on the high potential side and a second switch on the ground side connected in series with the first switch, an inductor for current limiting connected to the high potential side output terminal of the half bridge circuit, An auxiliary power supply circuit for a switching power supply comprising a first insulation capacitor connected in series to the current limiting inductor, and a second insulation capacitor connected to the ground side output terminal of the half bridge circuit,
The auxiliary power circuit is
A high-frequency current bypass capacitor connecting a connection point between the current-limiting inductor and the first insulation capacitor and a ground-side output terminal of the half-bridge circuit;
A rectifier circuit that rectifies the voltage stepped down by the bypass capacitor,
The voltage rectified by the rectifier circuit is output as a control voltage.

The effect of this invention is demonstrated. First, regarding the operation of the switching power supply device, the current limiting inductor and the first insulation capacitor are connected in series to the high potential side output terminal of the half bridge circuit. The connection point of the insulating capacitor (point c in FIG. 1) is held at “plus potential”. Subsequently, when the second switch is turned on (the first switch is turned off), a closed loop including a current limiting inductor and two insulating capacitors is formed including the load, so that the charge stored in the first insulating capacitor is used for current limiting. It flows through the inductor to the second insulating capacitor. In this way, even when the second switch is turned on, a period in which the connection point is “plus potential” occurs. The potential at this connection point once decreases to a minus potential during the ON period of the second switch, but rises again to a “plus potential”. Then, the first switch is turned on in the positive potential state.
The auxiliary power supply circuit of the present invention utilizes such an operation of the switching power supply device, and the “plus potential” is kept relatively long at the connection point (point c) connecting the bypass capacitor of the high-frequency current. In addition, since the control power is extracted from the circuit configuration including the current-limiting inductor and the insulating capacitor, no circuit loss occurs in the process in which the auxiliary power supply circuit acquires and supplies the control voltage. Therefore, the control power can be stably taken out.

Here, the bypass capacitor in the auxiliary power supply circuit of the present invention is configured by a series circuit of a first bypass capacitor on the high potential side and a second bypass capacitor on the ground side, and the rectifier circuit includes the first and second bypass capacitors. It is provided to rectify the divided voltage at the connection point of the capacitor . Alternatively, the bypass capacitor is configured by a series circuit of a step-down capacitor on the high potential side and a diode that blocks current from the high potential side to the ground side, and the rectifier circuit is connected at a connection point of the step-down capacitor and the diode. It is provided to rectify the divided voltage.

The bypass capacitor is preferably connected in series with a third switch that opens and closes the connection of the second bypass capacitor.
According to this configuration, since the divided voltage by the bypass capacitor is changed by opening and closing the third switch element, the output voltage of the auxiliary power supply circuit can be adjusted accordingly.

On the other hand, the switching power supply device according to the present invention is
A half bridge circuit having a first switch on the high potential side and a second switch on the ground side connected in series with the first switch;
A current-limiting inductor connected to the high-potential side output terminal of the half-bridge circuit;
A first insulation capacitor connected in series to the current limiting inductor;
A second insulation capacitor connected to the ground-side output terminal of the half-bridge circuit;
And an auxiliary power circuit.

According to the present invention, the bypass current capacitor is connected to the connection point between the current-limiting inductor and the first insulation capacitor of the switching power supply device, and the control power is taken out from this connection point. An auxiliary power circuit that is not present can be configured. In addition, since the control power is extracted from the circuit configuration using the inductor and the capacitor, there is no circuit loss in the process in which the auxiliary power supply circuit acquires and supplies the control voltage. In addition, the “plus potential” at the connection point between the current-limiting inductor and the insulating capacitor is maintained for a relatively long time.
As described above, even when the output of the switching power supply device is changed and the output to the load side is narrowed down, the supply voltage to the control circuit or the like does not decrease excessively, and the control circuit is stopped or It can avoid becoming stable.

It is a whole block diagram of the LED lighting device of 1st embodiment of this invention. It is the figure which showed the voltage waveform in the point a of FIG. FIG. 2 is a diagram showing voltage waveforms at points b and c in FIG. 1 on the same time axis. It is the figure which showed each voltage waveform at the time of narrowing down a lighting device output in FIG. The figure for demonstrating the voltage change of the g point according to operation | movement of switch Q1 of FIG. It is a whole block diagram of the switching power supply device of 2nd embodiment of this invention.

The circuit configuration and circuit operation of the LED lighting device according to the first embodiment of the present invention will be described with reference to the drawings.
First Embodiment The LED lighting device of FIG. 1 is a half-bridge type, in which 1 is an input AC power supply AC, 2 is a full wave that converts an AC voltage from the AC power supply 1 into a DC pulsating voltage. Rectifiers DB1, 3 are start-up circuits, 4 is a power factor correction circuit PFC that boosts the pulsating voltage to generate a DC voltage, 5 is a control circuit, 6 is a half-bridge circuit, and 7 is a full-frequency rectifier DB2 in a high frequency band. , 8 is an LED light emitter or lighting fixture, and 9 is an auxiliary power circuit for the control circuit.

Further, C1 in FIG. 1 is a smoothing capacitor that smoothes the harmonic component (ripple) of the current generated by the full-wave rectifier 2 in the commercial frequency band. A series circuit including a resistor R1, a diode D1, and a starting circuit 3 is connected between both terminals of the smoothing capacitor C1. The startup circuit 3 generates a startup signal to the power factor correction circuit 4 and the half-bridge control circuit 5 by using the divided voltage of the inter-terminal voltage of the smoothing capacitor C1 as a power source.
C2 is a smoothing capacitor (electrolytic capacitor) that is charged by the DC voltage boosted by the power factor correction circuit 4, and supplies DC power to the half-bridge circuit 6 at the subsequent stage. The cathode terminal of the smoothing capacitor C2 is connected to a ground wiring having a reference potential in the lighting device.

  The half bridge circuit 6 is a series circuit of two switches Q2 and Q3 formed of FETs, and is connected to both ends of the smoothing capacitor C2. The switch Q2 is on the high potential side, and the switch Q3 is on the ground side. The two switches Q2 and Q3 are turned on / off according to the drive signal from the control circuit 5, respectively. When the two switches Q2 and Q3 are alternately turned on and off at a high frequency f, a rectangular wave voltage (high frequency voltage) having a frequency f is generated from the connection point b.

  The connection point b forms an output terminal on the high potential side of the half bridge circuit 6, and the connection point e on the source side of the FET of the switch Q3 forms an output terminal on the ground side of the half bridge circuit 6. An LC series circuit composed of a small impedance current-limiting inductor L1 and a small-capacity first insulating capacitor C3 is connected to the connection point b. The other end of the capacitor C3 is connected to one input end of a high-frequency full-wave rectifier 7 composed of a diode bridge. A small-capacitance second insulating capacitor C4 is connected to the connection point e, and the other end of the capacitor C4 is connected to the other input end of the full-frequency rectifier 7 in the high frequency band.

The first and second insulation capacitors C3 and C4 are small-capacitance capacitors having an insulation resistance of at least 0.1 MΩ or more, preferably 0.2 MΩ or more, more preferably 0.4 MΩ or more with respect to an external AC power supply. Is preferred. Specifically, the capacitance of the insulating capacitors C3 and C4 is the maximum of the alternating current that flows to the ground through a person when the insulation between the LED element and the radiator is broken in the light emitter and the person contacts the radiator. The pF order is such that the value is 1 mA or less, which is a current value that does not affect the human body. For example, when the individual capacities of the insulating capacitors C3 and C4 are set to 7000 pF or less, the capacitive reactance 1 / (ωC) of the insulating capacitor can be about 0.2 MΩ or more at an alternating current of 60 Hz and 200 V.
Therefore, ceramic capacitors having the same pF order capacitance may be used for the small-capacity insulating capacitors C4 and C5.

Further, the capacitance of the capacitor C3 and the inductance of the inductor L1 are set so that the impedance of the LC series connection circuit including the inductor L1 and the first insulating capacitor C3 is capacitive. Specifically, the absolute impedance value of the inductor L1 may be set to 0.5 times or less, preferably 0.1 times or less, more preferably 0.05 times or less than the impedance absolute value of the capacitor C3.
In the present embodiment, the current flowing through the connection point c between the inductor L1 and the capacitor C3 is represented by is, and the direction of the current is from the inductor L1 to the capacitor C3 is positive.

  The full-frequency rectifier 7 in the high frequency band includes four rectifying elements D2 to D5, and converts the current is flowing through the connection point c into a direct current. This DC current charges the smoothing capacitor C5 connected in parallel to the LED light emitter 8. The smoothing capacitor C5 smoothes the high frequency component (ripple) of the direct current, and sets the load current to the LED light emitter 8 to a value corresponding to the dimming rate. The high-frequency band full-wave rectifier 7 is composed of a high-speed diode having a sufficiently short reverse recovery time with respect to the high-frequency f.

The lighting operation of the LED lighting device of this embodiment will be described.
The input AC voltage is rectified by the full-wave rectifier 2 and becomes a pulsating flow as shown in FIG.
Next, the pulsating voltage is boosted by the power factor correction circuit 4 and becomes a DC voltage near 400 V, for example, to charge the smoothing capacitor C2. The inter-terminal voltage of the smoothing capacitor C2 becomes a high-frequency rectangular wave (square wave) voltage by the half-bridge circuit 6 driven by a command from the control circuit 5. The upper waveform in FIG. 3 is a waveform of a rectangular wave voltage generated at the connection point b. Since the inductor L1 limits the pulse current accompanying the rectangular wave voltage, the maximum current at the connection point c is limited. As a result, the voltage waveform at the connection point c is a high-frequency voltage waveform in which a positive potential and a negative potential are alternately generated, as shown on the lower side of FIG. This high-frequency voltage waveform is stepped down by the insulating capacitors C3 and C4, becomes DC again by the full-frequency rectifier 7 in the high frequency band, is smoothed by the smoothing capacitor C5, and then the LED light emitter 8 is turned on.

  Detailed operation is as follows. When the switch Q2 is turned on and the switch Q3 is turned off in the half bridge circuit 6, a rectangular wave voltage is applied to the connection point b, and a pulse current flows toward the inductor L1. While the forward pulse current is limited by the inductor L1, the charge stored in the smoothing capacitor C2 flows in the order of C2-> Q2-> L1-> C3-> D2-> C5-> D5-> C4-> C2 and flows through the smoothing capacitor C5. It becomes a direct current that charges and turns on the light source LA. During this period, the insulating capacitors C3 and C4 are charged.

  Next, when the switch Q2 is turned off and the switch Q3 is turned on, the voltage at the connection point b becomes a ground level voltage. Then, the electric charge stored in the insulating capacitors C3 and C4 becomes a pulse current in the negative direction while being limited by the inductor L1, and flows into the connection point b. The pulse current in the negative direction flows in the order of C3-> L1-> Q3-> C4-> D3-> C5-> D4-> C3, and during this period, the smoothing capacitor C5 is charged and becomes a direct current that turns on the light source LA.

<Configuration of auxiliary power circuit>
Next, the auxiliary power supply circuit 9 for supplying control power to the power factor correction circuit 4 and the control circuit 5 will be described. The auxiliary power supply circuit 9 is provided between the high-potential side connection point c and the ground-side connection point f, and generates a predetermined control voltage by taking out control power from the high-potential side connection point c. Specifically, it includes a series circuit of bypass capacitors C6 and C7 and a switch Q1, a series circuit of a diode D6 and an electrolytic capacitor C8, and a diode D7.
The series circuit of the bypass capacitors C6 and C7 and the switch Q1 is used to divide the voltage at the connection point c which is an input point. When Q1 is ON, the potential divided at the connection point g of the capacitors C6 and C7 is divided. Cause it to occur. The capacitor C6 alone or the series circuit of the capacitors C6 and C7 functions as a high-frequency current bypass capacitor.

The series circuit of the diode D6 and the electrolytic capacitor C8 connects the connection point g of the capacitors C6 and C7 and the ground level (connection point f), and stores control power in the electrolytic capacitor C8 by the voltage at the connection point g. Here, the diode D6 is connected in such a direction that only the current from the connection point g side flows in order to prevent the electrolytic capacitor C8 from discharging.
The diode D7 is also connected in such a direction as to connect the connection point g of the capacitors C6 and C7 and the ground level (connection point f) and to allow only the current from the ground side to flow toward the connection point g. The purpose is to allow the bypass capacitor C6 to discharge even when the switch Q1 is in the OFF state.
The connection point d between the diode D6 and the electrolytic capacitor C8 is connected to the power supply terminals of the power factor correction circuit 4 and the control circuit 5, and supplies DC power charged in the electrolytic capacitor C8 as control power.
The switch Q1 is composed of an FET or the like, and is turned on when a drive voltage is applied to the gate from the half-bridge control circuit 5.

The auxiliary power supply circuit 9 configured as described above operates as follows.
First, a case where the switch Q1 is off will be described.
The voltage (potential) at the connection point c is stepped down by the capacitor C6. As shown in the lower side of FIG. 3, the voltage waveform at the connection point c alternately has a positive potential period and a negative potential period as the half bridge circuit 6 operates. Accordingly, the flow of charges in the auxiliary power supply circuit 9 changes under the influence of the voltage waveform at the connection point c. When the potential at the connection point g is higher than the positive electrode of the electrolytic capacitor C8, the current passes through the diode D6 and charges the electrolytic capacitor C8.

The flow of charges in the auxiliary power supply circuit 9 will be described in detail.
During a period in which the rectangular wave voltage is at a high potential (switch Q2 on period: period I), the connection point c is held at a positive potential. When Q2 is turned on, the current in the positive direction (rightward) of inductor L1 gradually increases, and charging of insulating capacitors C3 and C4 proceeds. When the insulating capacitors C3 and C4 become full, the current of the inductor L1 stops, and then the discharging of the insulating capacitors C3 and C4 starts, and a negative (leftward) current starts to flow through the inductor L1. Thus, during the on period of Q2, the voltage waveform at the connection point c has a mountain shape (always a positive potential). Therefore, in the auxiliary power circuit 9, charging of the electrolytic capacitor C8 proceeds by the voltage stepped down by the bypass capacitor C6. The current in the auxiliary power circuit 9 flows from the connection point c → C6 → D6 → C8 → connection point f.

  On the other hand, during a period in which the rectangular wave voltage is at a low potential (switch Q3 on period: period II), first, the connection point c when the switch Q3 is on exhibits a positive potential. When Q3 is turned on, a closed loop of C3.fwdarw.L1, Q3.fwdarw.C4.fwdarw.D3.fwdarw.C5.fwdarw.D4.fwdarw.C3 is formed, so that the discharge of the charge of the insulating capacitor C3 (the current in the negative direction of the inductor L1) proceeds. The potential at the connection point c drops to a negative potential, and the current in the inductor L1 stops. Subsequently, due to the release of the energy stored in the magnetic field of the inductor L1, a positive current flows again to the inductor L1, and the connection point c rises to a positive potential. As described above, the voltage waveform at the connection point c in the ON period of the switch Q3 has a valley shape including the period of the negative potential.

  Then, the operation of the auxiliary power supply circuit 9 during the ON period of the switch Q3 is such that the charging of the electrolytic capacitor C8 proceeds with the voltage stepped down by the bypass capacitor C6 when the connection point c is a positive potential. The current flows from connection point c → C6 → D6 → C8 → connection point f. Conversely, when the connection point c is a negative potential, the electrolytic capacitor C8 is not charged, and the discharge of the bypass capacitor C6 proceeds by the current flowing through the diode D7. The current flows from the connection point f → D7 → C6 → connection point c.

  Here, FIG. 4 shows waveforms when the on-duty of the half-bridge circuit 6 is reduced by dimming control. Although the ON period of the switch Q2 is shortened, the voltage waveform at the connection point c has a mountain shape (always a positive potential) while Q2 is ON, and the voltage waveform at the connection point c has a valley shape (a negative potential) while Q3 is OFF. Including the period. That is, regardless of the dimming rate, the voltage waveform at the connection point c alternates between a positive potential period and a negative potential period.

  Immediately after the commercial AC power is turned on, the power required for the operation is supplied from the start-up circuit 3 to the power factor correction circuit 4 and the control circuit 5 for several seconds. The supply from the starting circuit 3 is stopped when the DC voltage charged in the electrolytic capacitor C8 of the auxiliary power circuit exceeds a specified value, and thereafter, the control DC voltage is supplied from the auxiliary power circuit 9.

<Function of switch Q1>
Next, a case where the switch Q1 of the auxiliary power circuit 9 is turned on will be described. When Q1 is on, the voltage at the connection point c is divided by the bypass capacitors C6 and C7, and the voltage at the connection point g is lower than when Q1 is off. Therefore, by turning on and off the gate voltage of the switch Q1 as shown in FIG. 5 according to a command from the control circuit 5, the divided voltage can be switched as shown in the lower side of FIG. (Control voltage) can be adjusted.

The circuit operation of the auxiliary power supply circuit 9 when the switch Q1 is on will be described.
First, during the ON period of the switch Q2, the voltage waveform at the connection point c has a mountain shape (always a positive potential). In the auxiliary power circuit 9, charging of the electrolytic capacitor C8 proceeds by the voltage divided by the bypass capacitors C6 and C7. That is, the current in the auxiliary power supply circuit 9 has two types of flows: a flow from the connection point c → C6 → C7 → Q1 → connection point f and a flow from the connection point c → C6 → D6 → C8 → connection point f. Become a flow.

  On the other hand, in the ON period of the switch Q3, a closed loop of C3-> L1-> Q3-> C4-> DB2-> C5-> DB2-> C3 is formed, and the voltage waveform at the connection point c has a valley shape including a negative potential period. In the auxiliary power supply circuit 9, when the connection point c is a positive potential, charging of the electrolytic capacitor C8 proceeds by the voltage divided by the capacitors C6 and C7. Conversely, when the connection point c is a negative potential, the electrolytic capacitor C8 is not charged, and the current in the auxiliary power supply circuit 9 flows from the connection point f → D7 → C6 → connection point c and the connection point f. → Q1 → C7 → C6 → Flow to connection point c. Thereby, the electric charge stored in the capacitors C6 and C7 is released.

<Effect of this embodiment>
According to the LED lighting device of the present embodiment, the distribution capacitor C6 is connected as a high-frequency current bypass capacitor to the connection point c between the current limiting inductor L1 and the first insulation capacitor C3, and the control power is supplied from the connection point c. Since the auxiliary power supply circuit 9 obtains and supplies the control voltage, no circuit loss occurs. Further, by cooperation of the current limiting inductor L1 and the insulating capacitors C3 and C4, the “plus potential” at the connection point c between them is maintained for a relatively long time. Therefore, even when the light intensity of the LED light emitter is narrowed down, the power supply voltage to the control circuit or the like does not decrease excessively, and the power factor correction circuit 4 or the control circuit 5 stops or becomes unstable. Can be avoided.

  In this embodiment, since the switch Q1 is further provided, the voltage at the connection point g can be switched as shown in the lower side of FIG. 5, and the output voltage of the auxiliary power supply circuit 9 can be adjusted. In particular, by repeating on / off of the switch Q1 in a short cycle, the positive terminal voltage of the electrolytic capacitor C8 can be set to an intermediate voltage value between the on-time voltage and the off-time voltage. That is, the control circuit 5 can arbitrarily adjust the control voltage between the on-time voltage and the off-time voltage by changing the on-duty of the switch Q1.

Second Embodiment A switching power supply device according to a second embodiment of the present invention will be described with reference to FIG. In the power supply device of FIG. 6, portions common to the first embodiment are denoted by the same reference numerals and description thereof is omitted. This power supply device generates a high-frequency voltage in the half-bridge circuit 6 using a DC power supply 11 and supplies power to a load via a pair of insulating capacitors C3 and C4.
This power supply device also includes an auxiliary power supply circuit 19 for the control circuit, and can supply a stable control voltage. That is, the auxiliary power supply circuit 19 includes a series circuit of a step-down capacitor C6 and a diode D7 connected between a connection point c on the high potential side and a connection point f on the ground side, and a series circuit of a diode D6 and an electrolytic capacitor C8. Consists of. Here, the step-down capacitor C6 functions as a high-frequency current bypass capacitor. The series circuit of the diode D6 and the electrolytic capacitor C8 connects the connection point g between the capacitor C6 and the diode D7 and the ground level (connection point f), and the control power is supplied to the electrolytic capacitor C8 by the voltage at the connection point g. store. That is, the auxiliary power supply circuit 19 of FIG. 6 has a circuit configuration equivalent to a state in which the switch Q1 is on in the auxiliary power supply circuit 9 of the first embodiment.

  In each of the above embodiments, the case of the half-bridge circuit 6 is shown as the high-frequency voltage generation circuit, but the present invention can also be applied to the case of a full-bridge circuit. In each embodiment, the current limiting inductor L1 is connected in series with the first insulating capacitor C3. In addition to this configuration, another current limiting inductor is also connected in series with the second insulating capacitor C4. May be. Alternatively, instead of the inductor L1, a similar inductor may be connected in series only to the second insulating capacitor C4.

1: AC power supply 2: Commercial waveband full wave rectifier 3: Start-up circuit (start circuit)
4: Power factor correction circuit 5: Control circuit 6: Half bridge circuit 7: Full-wave rectifier in high frequency band 8: LED light emitter (or LED lighting fixture)
9: Auxiliary power supply circuit for control

Claims (4)

A half bridge circuit having a first switch on the high potential side and a second switch on the ground side connected in series with the first switch, an inductor for current limiting connected to the high potential side output terminal of the half bridge circuit, In an auxiliary power supply circuit for a switching power supply comprising a first insulation capacitor connected in series to the current limiting inductor, and a second insulation capacitor connected to the ground side output terminal of the half bridge circuit,
A high-frequency current bypass capacitor connecting a connection point between the current-limiting inductor and the first insulation capacitor and a ground-side output terminal of the half-bridge circuit;
A rectifier circuit that rectifies the voltage stepped down by the bypass capacitor,
The bypass capacitor is composed of a series circuit of a first bypass capacitor on the high potential side and a second bypass capacitor on the ground side,
The rectifier circuit is provided to rectify a divided voltage at a connection point of the first and second bypass capacitors,
An auxiliary power supply circuit that outputs a voltage rectified by the rectifier circuit as a control voltage. A half bridge circuit having a first switch on the high potential side and a second switch on the ground side connected in series with the first switch, an inductor for current limiting connected to the high potential side output terminal of the half bridge circuit, In an auxiliary power supply circuit for a switching power supply comprising a first insulation capacitor connected in series to the current limiting inductor, and a second insulation capacitor connected to the ground side output terminal of the half bridge circuit,
A high-frequency current bypass capacitor connecting a connection point between the current-limiting inductor and the first insulation capacitor and a ground-side output terminal of the half-bridge circuit;
A rectifier circuit that rectifies the voltage stepped down by the bypass capacitor,
The bypass capacitor is composed of a series circuit of a step-down capacitor on the high potential side and a diode that blocks current from the high potential side to the ground side,
The rectifier circuit is provided to rectify a divided voltage at a connection point of the step-down capacitor and the diode,
An auxiliary power supply circuit that outputs a voltage rectified by the rectifier circuit as a control voltage. The auxiliary power circuit according to claim 1 ,
3. The auxiliary power supply circuit according to claim 1, wherein a third switch for opening and closing the connection of the second bypass capacitor is connected in series to the bypass capacitor. A half bridge circuit having a first switch on the high potential side and a second switch on the ground side connected in series with the first switch;
A current-limiting inductor connected to the high-potential side output terminal of the half-bridge circuit;
A first insulation capacitor connected in series to the current limiting inductor;
A second insulation capacitor connected to the ground-side output terminal of the half-bridge circuit;
The auxiliary power supply circuit according to any one of claims 1 to 3,
A switching power supply device comprising:

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