JP4234691B2 - Switching power supply - Google Patents

Description

  The present invention relates to a switching power supply device, and more particularly to a technique for configuring a magamp control circuit that controls an output voltage on the secondary side.

  In the conventional switching power supply device, the output voltage on the secondary side of the transformer is fed back to the primary side of the transformer, and the output voltage on the primary side of the transformer is PWM-controlled by the fed back voltage, thereby stabilizing the output voltage. Has been done.

  On the other hand, in a power supply that outputs a plurality of types of voltages, a magamp control circuit is used to stabilize each output voltage individually. Since the output voltage is controlled on the secondary side, this mag-amplifier control circuit is suitable for individually stabilizing each output voltage of a power supply that outputs a plurality of types of voltages.

  FIG. 5 is a diagram showing a circuit configuration of a conventional full-bridge switching power supply device that outputs two types of voltages, a low voltage and a high voltage. The primary side of the transformer T1 of the switching power supply device includes a primary-side smoothing electrolytic capacitor C1 provided between the input terminals IN1 and IN2 to which a primary-side smoothed voltage obtained by rectifying and smoothing an AC voltage is input, and a full side. A bridge circuit 1 and a full bridge control circuit 2 for controlling the full bridge circuit 1 are configured.

  The full bridge circuit 1 is connected between the input terminals IN1 and IN2 and is connected in parallel to a first series circuit composed of a field effect transistor (hereinafter referred to as “FET”) Q1 and FET Q3, and the first series circuit. And a second series circuit composed of FETQ2 and FETQ4.

  The connection point of FETQ1 and FETQ3 is connected to the winding start (shown by a black circle) of the primary winding N0 of the transformer T1, and the connection point of FETQ2 and FETQ4 is connected to the winding end of the winding N0. Yes.

  The full bridge control circuit 2 turns on the FETs Q1 to Q4 constituting the full bridge circuit 1 according to the feedback voltage fed back through the output voltage detection circuit 3 and the photocoupler DS1 to the secondary low voltage output of the transformer T1. Control off / on.

  That is, when the full bridge control circuit 2 turns on FETQ1 and FETQ4 (FETQ2 and FETQ3 are off) with a duty according to the feedback voltage from the low-voltage output on the secondary side, IN1 → Q1 → N0 → Q4 → A current flows through the path IN2, and when the FET Q2 and the FET Q3 are turned on (FET Q1 and FET Q4 are turned off) at the next timing, a current flows through the path IN1 → Q2 → N0 → Q3 → IN2. Thereby, the direction of the current flowing through the winding N0 of the transformer T1 is switched alternately.

  On the secondary side of the transformer T1, a low voltage generation circuit, a high voltage generation circuit, and an output voltage detection circuit 3 are provided. The low voltage generation circuit includes a secondary side winding N1 and winding N2, transformer rectifier diodes D1 and D2, a flywheel diode D3, a smoothing coil L1, an output smoothing electrolytic capacitor C2, and an output discharge resistor R1. ing.

  The anode of the rectifier diode D1 is connected to the winding start of the winding N1 (indicated by a black circle). The winding end of the winding N1 is equal to the winding start of the winding N2 (indicated by a black circle), and is connected to the low voltage output terminal OL2. The anode of the rectifier diode D2 is connected to the end of the winding N2. The cathode of the rectifier diode D1 and the cathode of the rectifier diode D2 are connected, and the cathode of the flywheel diode D3 and one end of the smoothing coil L1 are connected to this connection point. The anode of the flywheel diode D3 is connected to the connection point between the winding N1 and the winding N2, that is, the low voltage output terminal OL2, and the other terminal of the smoothing coil L1 is connected to the low voltage output terminal OL1. . The output smoothing electrolytic capacitor C2 and the output discharge resistor R1 are connected between the low voltage output terminals OL1 and OL2.

  In the low voltage generating circuit configured as described above, the alternating voltage induced in the secondary winding N1 and the winding N2 by the alternating current flowing in the primary winding N0 is a rectifier diode. Full-wave rectification is performed by a rectifier circuit composed of D1 and D2, smoothed by a smoothing circuit composed of a smoothing coil L1 and an output smoothing electrolytic capacitor C2, and is output between low voltage output terminals OL1 and OL2.

  As described above, the voltage output between the low voltage output terminals OL1 and OL2 is detected by the output voltage detection circuit 3 and fed back to the primary side full bridge control circuit 2 via the photocoupler DS1. The As a result, the FETs Q1 to Q4 of the full bridge circuit 1 are PWM-controlled to stabilize the low voltage output.

  The high voltage generation circuit includes a secondary side winding N3 and winding N4 of the transformer T1, rectifier diodes D4 and D5, a flywheel diode D8, a smoothing coil L2, an output smoothing electrolytic capacitor C3, an output discharge resistor R2, and a mag amplifier control. It consists of a circuit. The mag-amplifier control circuit includes saturable reactors L3 and L4, voltage detection resistors R3 and R4, resistors R5 to R8, diodes D6 and D7, a transistor Q5, and a shunt regulator IC1.

  The anode of the rectifier diode D1 is connected to the beginning of winding (shown by a black circle) of the winding N3 via a saturable reactor L3. The winding end of the winding N3 is equal to the winding start of the winding N4 (indicated by a black circle), and is connected to the high voltage output terminal OH2. The anode of the rectifier diode D5 is connected to the winding end of the winding N4 via a saturable reactor L4. The cathode of the rectifier diode D4 and the cathode of the rectifier diode D5 are connected, and the cathode of the flywheel diode D8 and one end of the smoothing coil L2 are connected to this connection point. The anode of the flywheel diode D8 is connected to the connection point between the winding N3 and the winding N4, that is, the high voltage output terminal OH2, and the other terminal of the smoothing coil L2 is connected to the low voltage output terminal OH1. . The output smoothing electrolytic capacitor C3 and the output discharge resistor R2 are connected between the high voltage output terminals OH1 and OH2.

  Further, voltage detection resistors R3 and R4 connected in series are connected between the high voltage output terminals OH1 and OH2, and the connection point of the voltage detection resistors R3 and R4 is connected to the reference terminal of the shunt regulator IC1. In addition to being connected, the resistor R5 is connected to the cathode of the shunt regulator IC1. The shunt regulator IC1 has an anode connected to the high voltage output terminal OH2 and a cathode connected to the base of a PNP type transistor Q5 via a resistor R7. The emitter of the transistor Q5 is connected to the high voltage output terminal OH1 and is connected to the base of the transistor Q5 via the resistor R6. The collector of the transistor Q5 is connected to the anodes of the diode D6 and the diode D7 via the resistor R8. The cathode of the diode D6 is connected to the connection point between the saturable reactor L3 and the diode D4, and the cathode of the diode D7 is connected to the connection point between the saturable reactor L4 and the diode D5.

  In the high voltage generation circuit configured as described above, the alternating voltage induced in the secondary winding N3 and the winding N4 due to the alternating current flowing in the primary winding N0 is the rectifier diode D4. And D5 are full-wave rectified, smoothed by the smoothing coil L2 and the output smoothing electrolytic capacitor C3, and output between the high voltage output terminals OH1 and OH2.

  Further, in order to stabilize the high voltage output separately from the low voltage output, PWM control is performed by a mag amplifier control circuit using the saturable reactors L3 and L4. That is, in the magamp control circuit, a voltage obtained by resistance-dividing the high voltage output by the voltage detection resistors R3 and R4 is applied to the reference terminal of the shunt regulator IC1. The shunt regulator IC1 controls the voltage applied to the base of the transistor Q5 according to the voltage input to the reference terminal, and varies the current flowing through the transistor Q5. The current output from the collector of the transistor Q5 is supplied to the connection point a between the saturable reactor L3 and the diode D4 via the resistor R8 and the diode D6, and the saturable reactor L4 and the diode via the resistor R8 and the diode D7. It is supplied to the connection point b of D5.

  When the connection point a becomes a negative potential, a reset current flows from the transistor Q5 to the saturable reactor L3 via the resistor R8 and the diode D6, and the magnetic flux of the saturable reactor L3 corresponding to the magnitude of the reset current is reset. Done. When the magnetic flux is reset, the saturable reactor L3 changes from the saturated state to the unsaturated state. Similarly, when the connection point b becomes a negative potential, a reset current flows from the transistor Q5 to the saturable reactor L4 via the resistor R8 and the diode D7, and the magnetic flux of the saturable reactor L4 corresponding to the magnitude of the reset current. Is reset. When the magnetic flux is reset, the saturable reactor L4 changes from the saturated state to the unsaturated state.

  When the saturable reactor L3 becomes non-saturated, the inductance of the saturable reactor L3 increases, and even if the voltage E is applied in the positive direction from the winding N3 to the saturable reactor L3, it corresponds to the reset amount ΔΦ of the magnetic flux. The current begins to flow with a delay of the time ΔT. Here, from the relationship of magnetic flux (ΔΦ) = voltage time product (time ΔT × area E), ΔT = ΔΦ / E, and the pulse current flowing through the winding N3 of the transformer T1 is controlled by controlling the magnetic flux reset amount ΔΦ. Varying the pulse width.

Similarly, when the saturable reactor L4 becomes non-saturated, the inductance of the saturable reactor L4 increases, and even if the voltage E is applied in the positive direction from the winding N4 to the saturable reactor L4, the amount of magnetic flux resetting Current begins to flow with a delay of time ΔT corresponding to ΔΦ. Here, the pulse width of the pulse current flowing through the winding N4 of the transformer T1 is changed by controlling the magnetic flux reset amount ΔΦ as described above. Thereby, the high voltage output is PWM controlled on the secondary side.
Japanese Patent No. 3469565

  By the way, in the conventional switching power supply device described above, the VCE withstand voltage rating of the transistor Q5 is 4 to 5 times the output voltage because a pulsed voltage induced in the secondary windings N3 and N4 is applied. The above is necessary. For example, when a high voltage output of 250V is to be obtained, a pulse voltage of 1000V or higher is generated in the secondary windings N3 and N4, and therefore a transistor Q5 having a breakdown voltage of 1000V or higher is required. .

  However, a transistor having a withstand voltage of 1000 V or more is a special transistor in the PNP type. Therefore, it is difficult to obtain and the price is high. Further, the shunt regulator IC1 may be damaged due to a high voltage applied due to an overload or the like.

  The present invention can employ a low withstand voltage element as an element for controlling a current flowing in a saturable reactor for a magamp, and can suppress a voltage applied to a control circuit including the element to a low level even during an overload. Is to provide.

In order to achieve the above object, a switching power supply according to the present invention supplies a voltage obtained by rectifying and smoothing an AC voltage or a DC voltage to a winding on a primary side of a transformer by turning on / off a switching circuit. In a switching power supply device that outputs a rectified and smoothed AC voltage induced in a secondary winding of a transformer in a secondary circuit, a saturable reactor connected in series to the secondary winding; A rectifying / smoothing circuit that rectifies and smoothes the output of the saturable reactor, a current output element that outputs a current according to a voltage output from the rectifying / smoothing circuit by operating at a low voltage, and the saturable reactor separate a second winding, said Allowed movable wound with turns less than the saturation reactor in the same core as saturable reactors, output and said secondary winding of said current output device A reset winding connected between the tap drawn from, an auxiliary power supply for supplying a low voltage to the current output device, the current output device has a first electrode connected to the auxiliary power supply It comprises a transistor having a second electrode connected to the reset winding and a control electrode to which a voltage obtained by dividing the voltage output from the rectifying and smoothing circuit is applied.

According to the switching power supply device of the present invention, the reset current is supplied to the reset winding connected to the tap drawn from the secondary winding from the current output element operated by the low voltage supplied from the auxiliary power supply. Since the current flowing through the saturable reactor is controlled, the high voltage generated in the secondary circuit is not directly applied to the current output element. As a result, an element with a low withstand voltage can be employed as an element used in a control circuit that controls the current flowing through the saturable reactor. A transistor having a first electrode connected to the auxiliary power supply, a second electrode connected to the reset winding, and a control electrode to which a voltage obtained by dividing the voltage output from the rectifying and smoothing circuit is applied; Therefore, an element having a low VCE withstand voltage rating can be adopted, and if the element is composed of an FET, an element having a low VDS withstand voltage rating can be adopted. Further, the voltage applied to the control circuit including the element at the time of overload can be kept low.

  Hereinafter, a switching power supply device according to an embodiment of the present invention will be described in detail with reference to the drawings. In the following description, parts that are the same as or equivalent to the configuration of the conventional switching power supply device described in the background art section are denoted by the same reference numerals as those used in the background art section.

  The switching power supply according to Embodiment 1 of the present invention is a full-bridge switching power supply that outputs two types of voltages, a low voltage and a high voltage. FIG. 1 is a diagram illustrating a circuit configuration of the switching power supply device according to the first embodiment. The switching power supply device shown in FIG. 1 differs from the conventional switching power supply device shown in FIG. 5 only in the secondary high voltage generation circuit, so only the high voltage generation circuit will be described.

  The high voltage generation circuit includes a secondary side winding N3 and winding N4 of the transformer T1, rectifier diodes D4 and D5, a flywheel diode D8, a smoothing coil L2, an output smoothing electrolytic capacitor C3, an output discharge resistor R2, and a mag amplifier control. It consists of a circuit. The mag-amplifier control circuit includes saturable reactors L3 and L4, reset windings L3N1 and L4N1, voltage detection resistors R3 and R4, resistors R5 to R8, diodes D6 and D7, a PNP type transistor Q5, and a shunt regulator IC1. . The transistor Q5 corresponds to the current output element of the present invention. The current output element of the present invention is not limited to a PNP type transistor but can be an FET.

  The anode of the rectifier diode D1 is connected to the beginning of winding (shown by a black circle) of the winding N3 via a saturable reactor L3. The winding end of the winding N3 is equal to the winding start of the winding N4 (indicated by a black circle), and is connected to the high voltage output terminal OH2. The anode of the rectifier diode D5 is connected to the winding end of the winding N4 via a saturable reactor L4. The cathode of the rectifier diode D4 and the cathode of the rectifier diode D5 are connected, and the cathode of the flywheel diode D8 and one end of the smoothing coil L2 are connected to this connection point. The anode of the flywheel diode D8 is connected to the connection point between the winding N3 and the winding N4, that is, the high voltage output terminal OH2, and the other terminal of the smoothing coil L2 is connected to the low voltage output terminal OH1. . The output smoothing electrolytic capacitor C3 and the output discharge resistor R2 are connected between the high voltage output terminals OH1 and OH2.

  Further, voltage detection resistors R3 and R4 connected in series are connected between the high voltage output terminals OH1 and OH2, and the connection point of the voltage detection resistors R3 and R4 is connected to the reference terminal of the shunt regulator IC1. In addition to being connected, the resistor R5 is connected to the cathode of the shunt regulator IC1. The shunt regulator IC1 has an anode connected to a high voltage output terminal OH2 (magamp drive power supply input terminal MG2) and a cathode connected to the base of the transistor Q5 via a resistor R7. The emitter of the transistor Q5 is connected to an input terminal MG1 of a power source for a mag amp drive (not shown), and is connected to the base thereof via a resistor R6. The power source for the mag amplifier drive is an auxiliary power source that outputs a low voltage of about 5V or 12V provided in the switching power supply device. The collector of the transistor Q5 is connected to the anodes of the diode D6 and the diode D7 via the resistor R8. The cathode of the diode D6 is connected to one end of the reset winding L3N1, and the cathode of the diode D7 is connected to one end of the reset winding L4N1.

  The reset winding L3N1 is a control winding having the same magnetic core as the saturable reactor L3, and the number of turns is less than the number of turns of the saturable reactor L3. As described above, one end of the reset winding L3N1 is connected to the cathode of the diode D6, and the other end is connected to a tap drawn from the middle of the winding N3. The winding between this tap and the end of winding N3 is referred to as winding T1N1 for convenience. This tap position can be provided, for example, at a quarter position of the winding N3. In this case, assuming that a voltage of 1000 V is generated in the winding N3, a voltage of 250 V is generated in the winding T1N1, and this voltage is applied to the reset winding L3N1.

  Similarly, the reset winding L4N1 is a control winding having the same magnetic core as the saturable reactor L4, and the number of turns is smaller than the number of turns of the saturable reactor L4. As described above, one end of the reset winding L4N1 is connected to the cathode of the diode D7, and the other end is connected to a tap drawn from the middle of the winding N4. The winding between this tap and the start of winding of the winding N4 is referred to as winding T1N2 for convenience. This tap position can be provided, for example, at a quarter position of the winding N4. In this case, assuming that a voltage of 1000 V is generated in the winding N4, a voltage of 250 V is generated in the winding T1N2, and this voltage is applied to the reset winding L4N1.

  In the high voltage generation circuit configured as described above, the alternating voltage induced in the secondary winding N3 and the winding N4 due to the alternating current flowing in the primary winding N0 is the rectifier diode D4. And D5 are full-wave rectified, smoothed by a smoothing circuit comprising a smoothing coil L2 and an output smoothing electrolytic capacitor C3, and output between high voltage output terminals OH1 and OH2. These rectifying circuit and smoothing circuit correspond to the rectifying and smoothing circuit of the present invention.

  Further, in order to stabilize the high voltage output separately from the low voltage output, PWM control is performed by a mag amplifier control circuit using the saturable reactors L3 and L4. That is, in the magamp control circuit, a voltage obtained by resistance-dividing the high voltage output by the voltage detection resistors R3 and R4 is applied to the reference terminal of the shunt regulator IC1. The shunt regulator IC1 controls the voltage applied to the base of the transistor Q5 according to the voltage input to the reference terminal, and a mag-amp drive power source (not shown) varies the current flowing through the transistor Q5. The current output from the collector of the transistor Q5 is supplied to the reset winding L3N1 through the resistor R8 and the diode D6, and is supplied to the reset winding L4N1 through the resistor R8 and the diode D7.

  When the tap potential of the winding N3 becomes a negative potential, a reset current flows from the mag-amp drive power source through the transistor Q5, resistor R8, diode D6, reset winding L3N1 and winding T1N1 in sequence. Accordingly, a current having a magnitude corresponding to the reset current flows through the saturable reactor L3, and the magnetic flux of the saturable reactor L3 is reset. When the magnetic flux is reset, the saturable reactor L3 changes from the saturated state to the unsaturated state.

  Similarly, when the tap potential of the winding N4 becomes a negative potential, a reset current flows from the mag-amp drive power source through the transistor Q5, resistor R8, diode D7, reset winding L4N1, and winding T1N2. Accordingly, a current having a magnitude corresponding to the reset current flows through the saturable reactor L4, and the magnetic flux of the saturable reactor L4 is reset. When the magnetic flux is reset, the saturable reactor L4 changes from the saturated state to the unsaturated state.

  When the saturable reactor L3 becomes non-saturated, the inductance of the saturable reactor L3 increases, and even if the voltage E is applied in the positive direction from the winding N3 to the saturable reactor L3, it corresponds to the reset amount ΔΦ of the magnetic flux. The current begins to flow with a delay of the time ΔT. Here, from the relationship of magnetic flux (ΔΦ) = voltage time product (time ΔT × area E), ΔT = ΔΦ / E, and the pulse current flowing through the winding N3 of the transformer T1 is controlled by controlling the magnetic flux reset amount ΔΦ. Varying the pulse width.

  Similarly, when the saturable reactor L4 becomes non-saturated, the inductance of the saturable reactor L4 increases, and even if the voltage E is applied in the positive direction from the winding N4 to the saturable reactor L4, the amount of magnetic flux resetting Current begins to flow with a delay of time ΔT corresponding to ΔΦ. Here, the pulse width of the pulse current flowing through the winding N4 of the transformer T1 is changed by controlling the magnetic flux reset amount ΔΦ as described above. Thereby, the high voltage output is PWM-controlled on the secondary side.

  With the above configuration, a current of the same magnitude as that in the conventional case is supplied to the saturable reactor L3 with a voltage that is smaller by the turn ratio between the saturable reactor L3 and the reset winding L3N1 and the turn ratio between the winding N3 and the winding T1N1. be able to. Similarly, a current having the same magnitude as that of the conventional case can be supplied to the saturable reactor L4 with a voltage that is smaller by the turn ratio between the saturable reactor L4 and the reset winding L4N1 and the turn ratio between the winding N4 and the winding T1N2. it can.

  Therefore, the voltage controlled by the transistor Q5 can be reduced by the turn ratio described above, so that the VCE withstand voltage rating of the transistor Q5 can be lowered. For example, when the number of turns of the winding T1N1 is 1/4 that of the winding N3 and the number of turns of the reset winding L3N1 is 1/4 that of the saturable reactor L3, a transistor Q5 having a VCE withstand voltage rating of 1000 V is conventionally required. The transistor Q5 having a VCE withstand voltage rating of about 250V, which is ¼ of the above, can be used.

  Further, since the voltage applied to the elements constituting the mag amplifier control circuit at the time of overload or the like may be low, the possibility of failure can be reduced.

  The switching power supply according to Embodiment 2 of the present invention is a full-bridge resonance type switching power supply that outputs two kinds of voltages such as a low voltage and a high voltage.

  FIG. 2 is a diagram illustrating a circuit configuration of the switching power supply device according to the second embodiment. This switching power supply apparatus is configured by adding a resonance circuit to the output side of the full bridge circuit 1 in the switching power supply apparatus according to the first embodiment. Only the parts different from the switching power supply according to the first embodiment will be described below.

  The resonance circuit includes a capacitor Cs, a choke coil Ls, and a primary winding N0 of the transformer T1. The connection point of FETQ1 and FETQ3 constituting the full bridge circuit 1 is connected to the winding start (shown by a black circle) of the primary winding N0 of the transformer T1 via the capacitor Cs, and the connection point of FETQ2 and FETQ4 is It is connected to the winding end of the winding N0 via the choke coil Ls. According to the switching power supply device according to the second embodiment, since the sine wave is supplied to the primary winding N0, the conversion efficiency can be increased.

  The switching power supply according to Embodiment 3 of the present invention is a half-bridge switching power supply that outputs two types of voltages, a low voltage and a high voltage.

  FIG. 3 is a diagram illustrating a circuit configuration of the switching power supply device according to the third embodiment. In this switching power supply device, FETs Q1 and Q3 constituting the full bridge circuit 1 in the switching power supply device according to the first embodiment are replaced with capacitors C10 and C11, respectively, and the full bridge control circuit 2 is replaced with a half bridge control circuit 4. Configured. Only the parts different from the switching power supply according to the first embodiment will be described below.

  In this switching power supply device, FETQ2 and FETQ4 are alternately turned on / off. When the FET Q2 is turned on, a current flows to the rectifier diode D2 and the rectifier diode D5 via the secondary windings N2 and N4, and when the FET Q4 is turned on, the rectifier diode is passed via the secondary windings N1 and N3. A current flows through D1 and the rectifier diode D4.

  The surge voltage generated in the winding N0 is absorbed by the circuit formed by the body diode of the FET Q2 and the capacitor C10 and the winding N0 when the FET Q2 is turned on, and the body diode of the FET Q4 when the FET Q4 is turned on. Each is absorbed by the circuit formed by the capacitor C11 and winding N0.

  According to the configuration according to the third embodiment, in addition to the effects of the switching power supply device according to the first embodiment described above, a switching power supply device having various advantages of the half-bridge method can be realized.

  The switching power supply according to Embodiment 3 of the present invention is a forward-type switching power supply that outputs two kinds of voltages such as a low voltage and a high voltage.

  FIG. 4 is a diagram illustrating a circuit configuration of the switching power supply device according to the fourth embodiment. In this switching power supply device, a series circuit of the winding N0 of the transformer T2 and the FET Q1 is connected between the input terminal IN and the input terminal IN2 of the primary side smoothing voltage. The forward method control circuit 5 controls the low voltage output to a constant voltage by performing on / off control of the FET Q1 in accordance with the voltage detected by the output voltage detection circuit 3.

  Further, the secondary side circuit of the transformer T2 is for processing the voltage induced by the current flowing in the negative direction through the winding N0 from the secondary side circuit of the transformer T1 in the switching power supply device according to the first embodiment. The circuit is removed.

  According to the configuration according to the fourth embodiment, in addition to the effects of the switching power supply device according to the first embodiment described above, a switching power supply device with a simple configuration can be realized.

  In the first to fourth embodiments, a voltage obtained by rectifying and smoothing an AC voltage is input as the input voltage. For example, a DC voltage may be input to the primary side of the transformer.

It is a figure which shows the circuit structure of the switching power supply device which concerns on Example 1 of this invention. It is a figure which shows the circuit structure of the switching power supply which concerns on Example 2 of this invention. It is a figure which shows the circuit structure of the switching power supply apparatus which concerns on Example 3 of this invention. It is a figure which shows the circuit structure of the switching power supply apparatus which concerns on Example 4 of this invention. It is a figure which shows the circuit structure of the conventional switching power supply device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Full bridge circuit 2 Full bridge control circuit 3 Output voltage detection circuit 4 Half bridge control circuit 5 Forward system control circuit C1 Primary-side smoothing electrolytic capacitor Q1-Q4 FET
T1, T2 Transformers D1, D2, D4, D5 Rectifier diode D3, D8 Flywheel diode L1, L2 Smoothing coil C2, C3 Output smoothing electrolytic capacitor DS1 Photocoupler R1, R2 Output discharge resistor L3, L4 Saturable reactor R3, R4 Voltage detection resistors R5 to R8 Resistors D6 and D7 Diode Q5 Transistor IC1 Shunt regulator Cs Capacitor Ls Choke coil

Claims (5)

A voltage obtained by rectifying and smoothing an AC voltage or a DC voltage is turned on / off by a switching circuit to be supplied to the primary winding of the transformer, and the AC voltage induced in the secondary winding of the transformer is secondary. In the switching power supply that rectifies and smoothes the output on the side circuit,
A saturable reactor connected in series to the secondary winding;
A rectifying / smoothing circuit for rectifying and smoothing the output of the saturable reactor;
A current output element that outputs a current corresponding to a voltage output from the rectifying and smoothing circuit by operating at a low voltage;
The saturable reactor is a second winding independent of the saturable reactor, wound in the same magnetic core as the saturable reactor with a smaller number of turns than the saturable reactor, and the output of the current output element and the secondary winding A reset winding connected between the tap drawn from
An auxiliary power supply for supplying a low voltage to the current output element ,
The current output element includes a first electrode connected to the auxiliary power supply, a second electrode connected to the reset winding, and a control electrode to which a voltage obtained by dividing a voltage output from the rectifying and smoothing circuit is applied. A switching power supply device comprising a transistor having: The switching circuit is connected between terminals for inputting a voltage obtained by rectifying and smoothing the AC voltage or a DC voltage, and includes a first series circuit including a first switching element and a second switching element,
A second series circuit connected in parallel to the first series circuit and comprising a third switching element and a fourth switching element;
Have
A connection point between the first switching element and the second switching element is connected to one end of a primary winding of the transformer, and a connection point between the third switching element and the fourth switching element is The first switching element, the fourth switching element, the second switching element, and the second switching element are connected to the other end of the primary winding of the transformer, and complementarily turn on / off. The switching power supply device according to claim 1.   In addition to the primary winding, a capacitor is connected between a connection point between the first switching element and the second switching element and a connection point between the third switching element and the fourth switching element. The switching power supply device according to claim 2, wherein a resonance circuit including a reactor and a reactor is provided. The switching circuit is connected between terminals that input a voltage obtained by rectifying and smoothing the AC voltage or a DC voltage, and includes a first series circuit including a first capacitor and a second capacitor;
A second series circuit comprising a first switching element and a second switching element connected in parallel to the first series circuit;
Have
A connection point between the first capacitor and the second capacitor is connected to one end of a primary winding of the transformer, and a connection point between the first switching element and the second switching element is 2. The switching power supply device according to claim 1, wherein the first switching element and the second switching element are connected to the other end of the primary winding, and the first switching element and the second switching element are complementarily turned on / off.   The switching circuit includes a switching element that inputs a voltage obtained by rectifying and smoothing the AC voltage or a DC voltage via a primary winding of the transformer, and the switching element performs an on / off operation. The switching power supply device according to claim 1.

Images