JP4877926B2 - Switching power supply - Google Patents

Description

The present invention relates to a switching power supply device including an inrush current prevention circuit.

  Conventionally, as a thyristor driving method for an inrush current preventing circuit of this type of switching power supply, for example, there is the one shown in FIG.

  In FIG. 3, the switching power supply includes single-phase AC input terminals 1a and 1b, a noise reduction circuit 2, a bridge rectifier circuit 3, an inverter 4, an inrush current prevention resistor R4, a bypass circuit 5, and a bypass control circuit 6. .

  The noise reduction circuit 2 includes an interphase capacitor C1 connected to reduce the noise terminal voltage on the input side, and a discharge resistor Rc1 that discharges the interphase capacitor C1 when the input is cut off.

  The bridge rectifier circuit 3 is constituted by rectifier diodes D1, D2, D4, and D5 when power is turned on, but when the inrush current prevention resistor R4 is bypassed to reduce resistance loss, the rectifier diodes D4 and D5 Are switched to the thyristors SCR1 and SCR2 of the bypass circuit 5 to form a bridge circuit.

  The inverter 4 includes a boost choke coil L1, an inverter element TR7, a rectifier diode D12, and a smoothing capacitor C4. The inverter element TR7 is pulse width modulated by the control circuit 12. The inverter 4 is switched so that the phase of the rectified current matches the rectified voltage that is full-wave rectified by the bridge rectifier circuit 3 to improve the power factor.

  The bypass control circuit 6 includes a control power supply circuit 7 and a gate circuit 8. The control power supply circuit 7 has an inrush current limiting resistor R14, a charging capacitor C6, and a rectifying diode D11 in the secondary winding N2 of the boost choke coil L1. And another rectifier diode D10 is connected to the cathode of the diode D11.

  A smoothing capacitor C5 is connected between the anode of the diode D11 and the cathode of the diode D10. The anode of the diode D11 is connected to the cathodes of the bypass thyristors SCR1 and SCR2 of the bypass circuit 5, and the cathode of the diode D10 is connected to the gates of the bypass thyristors SCR1 and SCR2 via the limiting resistors R8 and R9 of the gate circuit 8.

  Here, when a single-phase alternating current is input to the single-phase alternating current input terminals 1a and 1b, the current immediately after the input is supplied from the rectifier diodes D4 and D5 to the inrush current preventing resistor R4, the primary winding N1 of the boost choke coil L1, the rectifier diode. It flows to the rectifier diodes D1 and D2 through D12 and the smoothing capacitor C4. The inrush current is suppressed by the inrush current preventing resistor R4.

  Since the input current flows through the inrush current prevention resistor R4 even after the inrush current converges, the loss of the current prevention resistor R4 continues as it is, so that the switching of the inverter element TR7 is started when the charging of the smoothing capacitor C4 is finished. If the path is changed by turning on the bypass thyristors SCR1 and SCR2, the current does not pass through the current prevention resistor R4 and the loss of the current prevention resistor R4 is eliminated.

  At that time, if the voltage of the smoothing capacitor C4 is bypassed before converging near the peak value of the input voltage, the inrush current does not pass through the inrush current preventing resistor R4, but charges the smoothing capacitor C4 through the thyristors SCR1 and SCR2. Since the thyristors SCR1 and SCR2 may be stressed, the inverter 4 is started after the voltage of the smoothing capacitor C4 is collected.

  The control power supply circuit 7 forms a voltage doubler rectifier circuit with the diodes D10 and D11, the resistor R14, and the capacitors C5 and C6. Double voltage rectification generates a DC control voltage, and a gate current is supplied to thyristors SCR1 and SCR2 to turn on bypass thyristors SCR1 and SCR2.

  When the bypass thyristors SCR1 and SCR2 are turned on, the current supplied to the single-phase AC input terminals 1a and 1b is supplied from the bypass thyristor SCR1 and SCR2 to the primary winding N1 of the boost choke coil L1, the rectifier diode D12, and the smoothing capacitor. The path changes to a path that flows to the rectifier diodes D1 and D2 through C4, and loss due to the inrush current prevention resistor R4 does not occur.

  In this configuration, the thyristors SCR1 and SCR2 are driven by the switching operation of the inverter element TR7. Therefore, the thyristors SCR1 and SCR2 are activated at the timing when the power supply circuit having the inverter element TR7 is activated and a steady input current is required. There is an advantage that can be turned on.

  Furthermore, when the inverter element TR7 is short-circuited, the DC control voltage is cut off and the gate current is not supplied promptly, so that the thyristors SCR1 and SCR2 are turned off, and the short-circuit current of the inverter element passes through the inrush current prevention resistor R4. Flowing. In this case, if a resistor with a fuse is used as the inrush current preventing resistor R4, there is an advantage that the power source body can be safely stopped by fusing due to heat generation.

As a circuit in which the circuit of FIG. 3 that is a single-phase AC input is directly applied to a three-phase AC input, for example, FIG. 4 can be considered.
JP 2001-298857 A JP 2004-112963 A

  However, since the inverter element TR7 continues to perform the switching operation, if the current continues to flow to the gates of the bypass thyristors SCR1, SCR2, and SCR3, and a reverse voltage is applied to the thyristor with the gate current flowing, However, there is a problem that the reverse current of the thyristor increases, resulting in an increase in loss and thermal escape.

  Further, the limiting resistors R8, R9, and R10 for limiting the gate currents of the bypass thyristors SCR1, SCR2, and SCR3 also continue to be lost because the current continues to flow.

  The adverse effect is that when the single-phase input structure of FIG. 3 is changed to the three-phase input structure of FIG. 4, the number of thyristors to which a reverse voltage is applied is reduced from one to two, and the loss due to the reverse current is reduced. Doubled. In addition, an increase in the number of thyristors that must be driven from two to three causes an increase in the adverse effect such that the loss of resistance for limiting the gate current also increases by 1.5 times.

In order to solve such a conventional problem, an object of the present invention is to provide a switching power supply device that optimizes a gate current flowing in a thyristor that bypasses an inrush current limiting resistor to achieve miniaturization by reducing loss. .

  In order to achieve this object, the switching power supply device of the present invention is configured as follows. First, the present invention is provided between a bridge rectifier circuit and an inverter, a bridge rectifier circuit that rectifies and outputs input AC power, an inverter that switches the rectified output of the bridge rectifier circuit to convert it to DC power, An inrush current limiting resistor that limits the inrush current flowing to the inverter when the power is turned on, and an anode connected to each of the AC input points of the bridge rectifier circuit, and a cathode bypassing the current limiting resistor and commonly connected to the input position of the inverter And a switching power supply device including a bypass circuit including a plurality of thyristors and a bypass control circuit that generates a DC control voltage by switching by starting an inverter and causes a gate current to flow through the thyristor.

  The bypass control circuit supplies a gate current to the thyristor based on the output of the control power circuit that generates a DC control voltage from the induced voltage of the secondary winding provided for the primary winding of the inverter. A gate circuit is provided.

  For such a switching power supply device, the present invention allows the gate current to be supplied to the thyristor at the start timing of the positive half cycle of the AC input voltage in which the forward voltage is applied between the anode and the cathode of the bypass thyristor, A gate current suppression circuit is provided that cuts off the gate current supply in the positive half cycle of the AC input voltage after the thyristor is turned on and in the subsequent negative half cycle of the AC input voltage.

  The gate current suppression circuit inputs a first switching circuit disposed between the control power supply circuit and the gate circuit, and an AC input voltage applied between the anode and cathode of the thyristor as a bias control voltage, and positive half of the AC input voltage. At the start timing of the cycle, the first switching circuit is turned on to supply a gate current to the thyristor to turn it on. After the thyristor is turned on, the positive half cycle of the AC input voltage and the negative AC input voltage following the negative cycle. A second switching circuit is provided that turns off the first switching circuit in a half cycle to cut off the supply of the gate current.

  The first switching circuit has a PNP transistor having an emitter connected to the control power circuit side and a collector connected to the gate circuit side of the thyristor, and the second switching circuit is applied between the base and emitter between the anode and cathode of the thyristor. An AC input voltage is input as a bias control voltage, and the collector is connected to the base of a PNP transistor to have an NPN transistor that is turned on and off.

That is, in the switching power supply device of the present invention, the gate current suppression circuit turns on and off the gate current of the bypass thyristor in synchronization with the cycle of the AC input voltage, so that the gate current is reduced when a reverse voltage is applied to the thyristor. The purpose of avoiding the flow is achieved.

  According to the present invention, the effects listed below can be obtained.

  Since the gate current is supplied to the thyristor only when the anode voltage of the bypass thyristor becomes higher than the cathode voltage (positive voltage applied state), the average value of the gate current is compared with the conventional method in which the gate current is always supplied. Is reduced. That is, the bypass control circuit can be reduced in size by reducing the loss of the gate circuit.

  When the AC input is a single phase, there are two bypass thyristors. However, in the case of a three-phase driving three thyristors, this loss reduction effect is even greater.

  Since the gate current of the thyristor is stopped when the cathode voltage of the bypass thyristor is higher than the anode voltage (reverse voltage application state), the cathode of the thyristor that increases when the reverse voltage is applied to the thyristor with the gate current flowing. To the anode is reduced. That is, it is possible to reduce a loss due to a reverse current when a reverse voltage is applied to the thyristor.

  When the AC input is a single phase, the number of thyristors that are turned off is always one, but when the three phases are always turned off, this loss reduction effect is even greater.

When an interphase capacitor for noise suppression is provided between the AC input terminal and the bridge rectifier circuit, a resistor for discharging the interphase capacitor when the AC input is interrupted is provided, but the transistor driving resistor of the second switching circuit is the discharge resistor. Also works. Since the discharge resistor for the interphase capacitor is exposed to the input voltage and line noise, it is necessary to consider the withstand voltage. However, by using the same as the transistor driving resistor of the second switching circuit, the discharge-dedicated resistor can be omitted.

  Next, preferred embodiments of the present invention will be described based on preferred examples shown in the accompanying drawings.

  FIG. 1 is a circuit diagram showing an embodiment of the present invention. In FIG. 1, the switching power supply includes three-phase AC input terminals 1a, 1b, 1c, a noise reduction circuit 2a, a bridge rectifier circuit 3a, an inverter 4a, an inrush current prevention resistor R4, a bypass circuit 5a, a bypass control circuit 6a, a gate. A current suppression circuit 9a is provided.

  The noise reduction circuit 2a includes interphase capacitors C1, C2, and C3 connected to reduce the noise terminal voltage on the input side.

  The bridge rectifier circuit 3a is constituted by diodes D1, D2, D3, D4, D5, and D6 when power is turned on, but when the inrush current preventing resistor R4 is bypassed to reduce resistance loss, the diode D4 , D5, D6 are switched to thyristors SCR11, SCR2, SCR3 of the bypass circuit 5a, respectively, and a bridge circuit is configured.

  The inverter 4a is a non-insulated boost chopper method. The boost choke coil L1, the inverter element TR7, the diode D12, and the capacitor C4 are configured. The inverter element TR7 is pulse-width modulated by the control circuit 12a, and the back electromotive force of the boost choke coil L1 when the inverter element TR7 is turned off. Utilizing this, a direct current is output through the diode D12. The inverter 4a performs switching so that the phase of the rectified current matches the rectified voltage that is full-wave rectified by the bridge rectifier circuit 3a to improve the power factor.

  The bypass control circuit 6a includes a control power supply circuit 7a and a gate circuit 8a. The control power supply circuit 7a includes a resistor R14, a capacitor C6, and a diode D11 connected to the secondary winding N2 of the boost choke coil L1, and the diode D11. Another diode D10 is connected to the cathode. A capacitor C5 is connected between the anode of the diode D11 and the cathode of the diode D10.

  The anode of the diode D11 is connected to the cathodes of the bypass thyristors SCR1, SCR2 and SCR3 of the bypass circuit 5, and the cathode of the diode D10 is the gate of the bypass thyristors SCR1, SCR2 and SCR3 via the resistors R8, R9 and R10 of the gate circuit 8a. Connected to.

  The gate current suppression circuit 9a includes a first switching circuit 10a and a second switching circuit 11a. The first switching circuit 10a has a PNP in which an emitter is connected to the control power circuit side 7a and a collector is connected to the gate circuit 8a side. Transistors TR2, TR4, TR6 and bias resistors R5, R6, R7, R15, R16, R17 connected to the bases of the PNP transistors TR2, TR4, TR6 are provided.

  The second switching circuit 11a has NPN transistors TR1, TR3, TR5 having collectors connected to the bases of the PNP transistors TR2, TR4, TR6 of the first switching circuit 10a, and emitters connected to the cathodes of the bypass thyristors SCR1, SCR2, SCR3. And bias resistors R1, R2, R3, R11, R12, R13 connected to the bases of the NPN transistors TR1, TR3, TR5.

  Here, when three-phase AC power is input to the three-phase AC input terminals 1a, 1b, and 1c, the capacitor C4 is charged, so that an inrush current immediately after the input is applied from the diodes D4, D5, and D6 to the inrush current prevention resistor R4, the booster The choke coil L1 flows through the primary winding N1, the rectifier diode D12, and the capacitor C4 to the diodes D1, D2, and D3, and the inrush current is suppressed by the inrush current prevention resistor R4.

  When the charging of the capacitor C4 is completed and the inrush current converges, the control circuit 12a is activated by receiving the control power supply voltage, and starts switching of the inverter element TR7.

  When the secondary winding N2 is induced by the switching voltage associated with the ON / OFF of the inverter element TR7, the control power supply circuit 7a that constitutes the voltage doubler rectifier circuit with the diodes D10 and D11, the resistor R14, and the capacitors C5 and C6 A control voltage is output, and a DC control voltage is supplied to the gate circuit 8a and the gate current suppression circuit 9a.

  In parallel with the start of supply of the control power supply voltage of the control power supply circuit 7a, the second switching circuit 11a applies the bias voltage between the anode and the cathode of the thyristors SCR1, SCR2, SCR3 of the bypass circuit 5a via the drive resistors R1, R2, R3. When detected and the anode voltage becomes higher than the cathode voltage, the NPN transistors TR1, TR3, TR5 are turned on by the base current flowing from the resistors R1, R2, R3.

  Specifically, since the three-phase AC voltage has a phase difference of 120 °, the anode voltage of the thyristors SCR1, SCR2, and SCR3 sequentially becomes higher than the cathode voltage with this phase difference, and the resistors R1, R2, R3 NPN transistors TR1, TR3, and TR5 are sequentially turned on by the base current flowing in from

  When the NPN transistors TR1, TR3, TR5 of the second switching circuit 11a are turned on, a base current flows through the PNP transistors TR2, TR4, TR6 of the first switching circuit 10a, and the PNP transistors TR2, TR4, TR6 are turned on.

  Therefore, a gate current flows from the control power supply circuit 7a to the thyristors SCR1, SCR2, SCR3 of the bypass circuit 5a through the transistors TR2, TR4, TR6 and the resistors R8, R9, R10 of the gate circuit 8a, and the thyristors SCR1, SCR2, SCR3 It turns on at the timing of a positive half cycle in which the anode and cathode are forward-biased by the three-phase AC voltage.

  If the bypass thyristors SCR1, SCR2 and SCR3 are turned on, the current input to the three-phase AC input terminals 1a, 1b and 1c is rectified by the thyristors SCR1, SCR2 and SCR3 of the bypass circuit 5a and supplied to the inverter 4a. Loss due to the inrush current prevention resistor R4 does not occur.

  Here, when the bypass thyristors SCR1, SCR2 and SCR3 are turned on, the voltage between the anode and the cathode of the bypass thyristors SCR1, SCR2 and SCR3 decreases. The resistance values of the resistors R1, R2, R3, R11, R12, R13 so that the anode-cathode voltage is lower than the minimum operating bias voltage (threshold voltage) of the NPN transistors TR1, TR3, TR5 of the second switching circuit 11a. Is set, NPN transistors TR1, TR3, TR5 are turned off, and PNP transistors TR2, TR4, TR6 are cut off to cut off the gate currents of thyristors SCR1, SCR2, SCR3.

  Since the gate current does not flow through the bypass thyristors SCR1, SCR2, and SCR3, the loss of the gate circuit 8a is reduced.

  On the other hand, in the negative half-cycle state of the three-phase AC voltage in which the cathode voltage of the bypass thyristors SCR1, SCR2, and SCR3 is higher than the anode voltage, that is, in the reverse voltage application state, the NPN transistors TR1, TR3, and TR5 are turned off. The PNP transistors TR2, TR4, TR6 are also turned off, and no gate current is supplied to the thyristors SCR1, SCR2, SCR3 of the bypass circuit 5a.

  Thus, the gate current does not flow through the bypass thyristors SCR1, SCR2, and SCR3, so that the reverse current of the thyristor is reduced and the loss of the bypass circuit 5a is reduced.

  When the AC input is stopped, the reverse voltage application preventing diodes D7, D8, D9 are connected to the bases of the NPN transistors TR1, TR3, TR5 of the second switching circuit 11a. A discharge path is formed through the diodes D7, D8, D9 and the resistors R1, R2, R3 from the interphase capacitors C1, C2, C3 of the noise reduction circuit 2a provided in the circuit 1 to discharge the interphase capacitors C1, C2, C3.

  Thereby, for example, the resistors RC1, RC2, RC3 for discharging the interphase capacitors C1, C2, C3 provided in the conventional noise reduction circuit shown in FIGS. 3 and 4 can be eliminated.

  Further, when the inverter element TR7 is broken by a short circuit, the rectified and smoothed voltage is not supplied from the secondary winding N2 of the boost choke L1, so that the thyristors SCR1, SCR2, and SCR3 are not turned on, and the short circuit current is an inrush current limiting resistor. It is suppressed by flowing through R4. At this time, by using a resistor with a thermal fuse for the inrush current limiting resistor R4, the fuse is blown by the short circuit current to be in an open state, and the power supply can be safely stopped.

  FIG. 2 is a circuit diagram showing another embodiment of the present invention, in which a single-phase AC input is used, and the inverter is an isolation transformer type single forward switching regulator.

  In FIG. 2, the switching power supply of this embodiment includes single-phase AC input terminals 1a and 1b, a noise reduction circuit 2b, a bridge rectifier circuit 3b, an inverter 4b, an inrush current prevention resistor R4, a bypass circuit 5b, and a bypass control circuit. 6b and a gate current suppression circuit 9b.

  The inverter 4b includes a transformer T1, a boost choke coil L1, an inverter element TR7, rectifying diodes D12 and D13, and a smoothing capacitor C4. The inverter element TR7 is subjected to pulse width modulation by a control circuit 12a insulated from the output side. Has been.

  The inverter 4b rectifies the switching power induced on the secondary side when the inverter element TR7 is turned on and off by the diodes D12 and D13, and then smoothes the switching power by the choke coil L1 and the capacitor C4 and outputs DC power of a constant voltage. ing.

  The bypass control circuit 6b includes a control power supply circuit 7b and a gate circuit 8b. The control power supply circuit 7b has a resistor R14, a diode D10, and a capacitor C5 connected to the secondary winding (auxiliary winding) N2 of the transformer T1, The rectified and smoothed DC control voltage is supplied to the gate circuit 8b and the gate current suppression circuit 9b.

  This embodiment is different from the embodiment of FIG. 1 in that the inverter 4b is different, except that the number of components is changed from three to two with the change from the three-phase AC input to the single-phase AC input. The configuration and operation are the same.

  In addition, this invention is not limited to said embodiment, If it is a switching power supply device which rectifies | straightens input alternating current power and operate | moves an inverter, it can be applied to an appropriate | suitable apparatus.

The present invention includes appropriate modifications that do not impair the objects and advantages thereof, and is not limited by the numerical values shown in the above embodiments.

1 is a circuit diagram showing an embodiment of the present invention. Circuit diagram showing another embodiment of the present invention Circuit diagram of conventional example with single-phase input Circuit diagram of conventional example with three-phase input

Explanation of symbols

1a, 1b, 1c: AC input terminals 2, 2a, 2b: Noise reduction circuits 3, 3a, 3b: Bridge rectifier circuits 4, 4a, 4b: Inverters 5, 5a, 5b: Bypass circuits 6, 6a, 6b: Bypass control Circuits 7, 7a, 7b: control power supply circuits 8, 8a, 8b: gate circuits 9a, 9b: gate current suppression circuits 10a, 10b: first switching circuits 11a, 11b: second switching circuits 12, 12a, 12b: inverter control Circuits SCR1, SCR2, SCR3: Thyristors C1-C6: Capacitors R1-R3, R5-R17: Resistor R4: Inrush current limiting resistors D1-D13: Diode L1: Boost choke T1: Transformer N1: Primary winding N2: Secondary Winding TR2, TR4, TR6: PNP transistors TR1, TR3, TR5: NPN transistor TR7: In Barter element

Claims (6)

AC input section,
A bridge rectifier circuit that rectifies and outputs input AC power; and
An inverter that switches the rectified output of the bridge rectifier circuit to convert it into DC power;
An inrush current limiting resistor that is provided between the bridge rectifier circuit and the inverter and limits an inrush current flowing to the inverter when the power is turned on;
A bypass circuit comprising a plurality of thyristors for connecting an anode to each of the AC input points of the bridge rectifier circuit and bypassing the current limiting resistor to connect the cathode to the input position of the inverter in common;
A DC control voltage is generated by switching by starting the inverter, a gate current is caused to flow through the thyristor, and a forward voltage is applied between the anode and cathode of the thyristor, and is turned on at every positive half cycle timing of the AC input voltage. A bypass control circuit;
In a switching power supply device with
The gate current is allowed to be supplied to the thyristor at the start timing of the positive half cycle of the AC input voltage in which a forward voltage is applied between the anode and cathode of the thyristor, and the AC input voltage after the thyristor is turned on is positive. A gate current suppression circuit that cuts off the supply of the gate current in the half cycle of the following and the negative half cycle of the AC input voltage that follows ,
The bypass control circuit includes:
A control power supply circuit for generating the DC control voltage from the induced voltage of the secondary winding provided for the primary winding of the inverter;
A gate circuit for supplying a gate current to the thyristor based on an output of the control power supply circuit;
With
The gate current suppression circuit is
A first switching circuit disposed between the control power supply circuit and the gate circuit;
An AC input voltage applied between the anode and cathode of the thyristor is input as a bias control voltage, and the first switching circuit is turned on at the start timing of the positive half cycle of the AC input voltage to supply a gate current to the thyristor. The first switching circuit is turned off in the positive half cycle of the alternating current input voltage after the thyristor is turned on and the negative half cycle of the alternating current input voltage after that, and the supply of the gate current is cut off. A switching circuit;
Switching power supply apparatus characterized by comprising a.
In the switching power supply device according to claim 1 ,
The first switching circuit has a PNP transistor having an emitter connected to the control power circuit side and a collector connected to the gate circuit side of the thyristor,
The second switching circuit inputs an AC input voltage applied between the anode and cathode of the thyristor between the base and emitter as a bias control voltage, and connects the collector to the base of the PNP transistor to turn on and off the NPN transistor A switching power supply device comprising:
In the switching power supply device according to claim 1 ,
The NPN transistor connects the anode of the thyristor to the base via a bias resistor, and a diode for preventing reverse voltage application between the base and emitter, and the diode is a noise terminal connected between AC input lines. A switching power supply comprising a discharge path passing through the bias resistor when an AC input of an interphase capacitor for reducing voltage is cut off.
3. The switching power supply device according to claim 1, wherein the AC power input is a single-phase AC power input or a three-phase AC power input. 4.
3. The switching power supply device according to claim 1, wherein the inverter is switched so that a phase of a rectified current coincides with a rectified voltage full-wave rectified by the bridge rectifier circuit to improve a power factor. A switching power supply comprising a power factor correction circuit.
3. The switching power supply device according to claim 1, wherein the inverter is a switching regulator that switches rectified and smoothed DC power and supplies DC power of a constant voltage to a load. 4. Switching power supply.

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