JP2006121808A - Switching power supply device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely protect thyristors arranged at a rush-current preventing circuit against a lightning surge by using a simple circuit. <P>SOLUTION: The rush-current preventing circuit 3 comprises the thyristors SCR1, SCR2 that are connected to a current limit resistor R1 in parallel therewith arranged on an input line of an active filter circuit 4, and bypasses the current limit resistor by on-passage-controlling the thyristors SCR1, SCR2 by using a trigger signal based on an output of an auxiliary winding L1 generated at the operation start of the active filter circuit 4. Surge protection circuits 12a, 12b make trigger currents flow by turning on Zener diodes ZD1, ZD2 by using a surge voltage of the lightning surge 13 applied to an input side, and perform surge protections by forcibly turning on the thyristors SCR1, SCR2. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a switching power supply device including an inrush current prevention circuit that turns on a thyristor connected in parallel to a current limiting resistor after the power is turned on, and more particularly to a switching power supply device that protects the thyristor of the inrush current prevention circuit from a lightning surge.

  Conventionally, in this type of switching power supply device, an abnormally high surge voltage, such as during a lightning strike, is superimposed on the AC voltage and may damage the inverter switching element. An absorption circuit is provided.

  This surge absorption circuit includes a surge absorber such as a surge absorber and an abnormal voltage elimination filter. There has been proposed a switching power supply device that absorbs surge voltage by turning on a thyristor and allowing surge current to flow through a large-capacity input capacitor provided in an input stage of an inverter.

  In recent years, switching power supply devices with large capacities have been provided with an active filter in the AC input stage of the switching regulator as a measure against electromagnetic interference (EMI), and the phase of the AC voltage and AC current are matched by switching control of the inverter. When the power factor is improved and an active filter is provided, a large inrush current flows when the AC power supply is turned on. Therefore, an inrush current prevention circuit is provided.

The inrush current prevention circuit provides a current limiting resistor on the input line of the active filter to limit the inrush current that flows transiently until the inverter starts up, and uses the voltage generated by the auxiliary winding of the inverter coil when the startup is completed. The thyristor is turned on to bypass the current limiting resistor to prevent power loss.
JP 2002-101650 A

  However, in such a switching power supply device having a conventional inrush current prevention circuit, a trigger signal for driving a thyristor provided in the inrush current prevention circuit is used as a boost choke coil provided in an inverter or an auxiliary winding of a transformer. Since the voltage is rectified and a pulse-like trigger signal synchronized with the switching of the inverter is obtained, the generation state of the trigger signal changes depending on the AC input phase and the weight of the load, especially with AC voltage or full-wave rectified voltage. In the vicinity of the zero cross of the input voltage, the forward voltage between the anode and the cathode is lower than the conduction maintaining voltage, so that it is turned off. If a lightning surge voltage is applied during this off period, the withstand voltage of the thyristor may occur, causing damage.

  For this reason, a surge absorber is connected between the phases of the AC input line to attenuate the surge voltage applied between the phases, or a surge absorber is connected between the anode and cathode of the thyristor to suppress the surge voltage. Absorbing parts have become large, and there have been problems such as increased costs and equipment.

SUMMARY OF THE INVENTION An object of the present invention is to provide a switching power supply device capable of reliably protecting a thyristor provided in an inrush current prevention circuit against a lightning surge with a simple circuit.

  In order to achieve this object, the present invention is configured as follows. The present invention relates to an active filter circuit that performs switching control of an inverter so that the phases of an AC voltage and an AC current coincide with each other when the AC input is rectified and DC output, and the DC input from the active filter circuit is switched by the inverter. In a switching power supply device having a switching regulator circuit that converts the output to a constant voltage DC output and supplies the load to a load, it has a thyristor connected in parallel to a current limiting resistor provided in the input line of the active filter circuit. And an inrush current prevention circuit that bypasses the current limiting resistor by controlling conduction of the thyristor based on the output of the auxiliary power supply generated when the active filter circuit or the switching regulator circuit starts operating, and a surge voltage applied to the input line of the active filter circuit When detecting Characterized in that a surge protection circuitry to conduct controlling the thyristors of the inrush current preventing circuit as issue source.

  Here, the surge protection circuit is a diode that rectifies the surge voltage and supplies a trigger signal to the gate terminal between the anode terminal and the gate terminal of the thyristor, a Zener diode that conducts by applying a surge voltage exceeding a predetermined Zener voltage, And a resistor for limiting the trigger current flowing in the gate terminal is connected in series.

  In the switching power supply device of the present invention, the inrush current prevention circuit is provided in the rectification output line of the full-wave rectification circuit provided on the input side of the active filter circuit. In this case, the thyristor of the inrush current prevention circuit is a one-way thyristor.

  In the switching power supply device of the present invention, an inrush current preventing circuit may be provided on the AC input line of the full-wave rectifier circuit provided on the input side of the active filter circuit. In this case, the thyristor of the inrush current prevention circuit is a triac that functions as a bidirectional thyristor.

The auxiliary power supply for the inrush current prevention circuit is an auxiliary winding of an inverter coil provided in the active filter circuit or the switching regulator circuit.

According to the present invention, a diode, a Zener diode, and a resistor are connected in series between the anode and gate of the thyristor of the inrush current prevention circuit, and the thyristor is turned off in the vicinity of the zero cross of the full-wave rectified voltage or AC voltage. When a lightning surge enters the thyristor's withstand voltage, the zener diode is turned on using the surge voltage, a trigger current is sent to the gate of the thyristor, and the thyristor is forcibly turned on. Prevents voltage breakover and improves lightning surge capability. For this reason, it is not necessary to provide a surge absorbing element for the thyristor, and it is realized by a simple circuit that full-wave rectifies the auxiliary winding signal of the inverter as a trigger circuit for the thyristor, thereby achieving cost reduction and downsizing.

  FIG. 1 is a circuit diagram showing an embodiment of a switching power supply device according to the present invention. In FIG. 1, the switching power supply device of the present invention is provided with two circuit diode bridges 2a and 2b following the AC input terminals 1a and 1b, and the positive side rectified output line of the diode bridges 2a and 2b is connected to the current limiting resistor. The input is connected to the active filter circuit 4 via R1.

  Further, thyristors SCR1 and SCR2 are connected to the lines from the AC input terminals 1a and 1b as parallel lines for bypassing the current limiting resistor R1, respectively. For the thyristors SCR1 and SCR2, the voltage generated in the auxiliary winding L1 of the boost choke coil CH1 provided in the active filter circuit 4 is rectified by a diode D5 and applied as a trigger signal to the gate terminal.

  The current limiting resistor R1, the thyristors SCR1 and SCR2, the auxiliary winding L1, and the diode D5 constitute an inrush current prevention circuit 3. A surge absorbing element SK1 is connected between the AC input terminals 1a and 1b to attenuate the surge voltage applied between the phases. As the surge absorbing element SK1, an appropriate surge absorbing element such as a gap discharge element, a silicon PN junction element, a zinc oxide varistor, or a molybdenum element can be used.

  An active filter circuit 4 provided subsequent to the inrush current prevention circuit 3 includes a boost choke coil CH1, diodes D1 and D2, a capacitor C1, a control circuit 6, and a transistor 7 as a switching element, and constitutes a boost inverter. . The control circuit 6 controls the switching of the transistor 7, and with respect to the voltage waveform of the full-wave rectified voltage input from the diode bridges 2a and 2b and the thyristors SCR1 and SCR2, a high-frequency switching current is caused to flow by switching of the transistor 7, By controlling so that the phase of the alternating current due to the average current matches the phase of the alternating voltage of the full-wave rectification, the power factor is controlled to 1 and electromagnetic interference is suppressed.

  The boost choke coil CH1 charges the boosted voltage to the capacitor C1 through the diode D1 with the converted output of power energy by switching of the transistor 7. For example, if the input voltage is 100 volts, the voltage of the capacitor C1 is, for example, 140 volts.

  The diode D2 charges the capacitor C1 at the time of startup when the AC power is turned on. When the inverter of the active filter circuit 4 is started, the voltage of the capacitor C1 exceeds the input voltage, so that the diode D2 receives a reverse bias and is turned off.

  A switching regulator circuit 5 provided subsequent to the active filter circuit 4 includes an inverter transformer 8 having a primary winding 8a and a secondary winding 8b, an FET 9 as a switching element, a control circuit 10, and a diode D3 constituting a rectifier circuit. , D4, choke coil CH2, and smoothing capacitor C2. The control circuit 10 performs switching control of the FET 9 so that the output voltages of the output terminals 11a and 11b with respect to the load are kept constant.

  Note that the efficiency of the switching power supply device is increased by providing two circuits of the diode bridges 2a and 2b and the thyristors SCR1 and SCR2.

  With respect to the switching power supply device constituted by the inrush current prevention circuit 3, the active filter circuit 4, and the switching regulator circuit 5, in the present invention, the thyristors SCR1 and SCR2 provided in the inrush current prevention circuit 3 are further provided. Surge protection circuits 12a and 12b are provided.

  Taking the surge protection circuit 12a as an example, a diode D7, a Zener diode ZD1, and a resistor R2 are connected in series between the anode and gate of a thyristor SCR1 provided in the inrush current prevention circuit 3. This also applies to the surge protection circuit 12b, in which a diode D8, a Zener diode ZD2, and a resistor R3 are connected in series between the anode and gate of the thyristor SCR2.

  The Zener diodes ZD1 and ZD2 of the surge protection circuits 12a and 12b are turned on when the surge voltage due to the lightning surge 13 applied to the AC input terminals 1a and 1b exceeds a predetermined Zener voltage, and the thyristors SCR1 and SCR1 are used with the surge voltage as a signal source. A trigger current is supplied to the gate terminal of SCR2 to forcibly turn thyristors SCR1 and SCR2 into a conductive state.

  The diodes D7 and D8 rectify the trigger current supplied by the conduction of the Zener diodes ZD1 and ZD2. The resistors R2 and R3 limit the trigger current that flows to the gate terminals of the thyristors SCR1 and SCR2.

  Next, the operation of the embodiment of FIG. 1 will be described. When AC power is input to the AC input terminals 1a and 1b by a switch operation or the like, the rectified output of the diode bridges 2a and 2b is supplied to the active filter circuit 4 through the current limiting resistor R1, and the capacitor C1 is first charged through the diode D2. Further, the control circuit 6 starts a switching operation.

  Similarly, in the switching regulator circuit 5, the control circuit 10 operates upon receiving power supply accompanying charging of the capacitor C <b> 1, and starts an inverter operation by switching control of the FET 9.

  In the transient state at the start immediately after the active filter circuit 4 and the switching regulator circuit 5 are turned on, an excessive inrush current tends to flow from the rectified output lines of the diode bridges 2a and 2b. Is provided with a current limiting resistor R1, so that an inrush current associated with startup is limited.

  Immediately after the power is turned on, since the inverter of the active filter circuit 4 is stopped, the trigger signal is not supplied to the thyristors SCR1 and SCR2, and the thyristors SCR1 and SCR2 are off.

  When the inverter operation is started by switching control of the transistor 7 by the control circuit 6 of the active filter circuit 4, a voltage is induced in the auxiliary winding L1 according to the switching current flowing through the boost choke coil CH1 as the transistor 7 is switched. .

  By rectifying the induced voltage of the auxiliary winding L1 with the diode D5, a pulse-like trigger signal synchronized with the switching of the transistor 7 is supplied to the gates of the thyristors SCR1 and SCR2, and the thyristor SCR1 is activated when the start of the inverter is completed. , SCR2 are turned on by a trigger signal, and the turned on thyristors SCR1, SCR2 form a full-wave rectifier circuit that bypasses the current limiting resistor R1.

  Here, an AC voltage is applied between the anode and cathode of the thyristors SCR1 and SCR2, and during the positive voltage half-cycle period in which the AC voltage is applied in the forward direction, the ON state is maintained by the trigger signal, but the AC voltage is reversed. The half cycle period of the negative voltage applied in the direction is off regardless of the trigger signal.

  On the other hand, if an excessive surge voltage due to the lightning surge 13 is applied during the operation of the switching power supply device, the Zener diodes ZD1 and ZD2 provided in the surge protection circuit 12a are turned on, and the diodes D7 and D8 are used with the surge voltage as a signal source. The trigger current flows to the gates of the thyristors SCR1 and SCR2 through the respective series circuits of the Zener diodes ZD1 and ZD2 and the resistors R2 and R3, and even if the thyristors SCR1 and SCR2 are in the off period, they are forcibly turned on. Thus, the current accompanying the surge voltage flows from the thyristors SCR1 and SCR2 in the on state through the diode D2 provided in the active filter circuit 4 to the large-capacitance capacitor C1, thereby absorbing the surge.

  For this reason, it is not necessary to provide surge protection by connecting surge absorbing elements in parallel to the thyristors SCR1 and SCR2 of the inrush current preventing circuit 3 as in the prior art, and diodes D7 and D8, zener diodes ZD1 and ZD2, and resistor R2 , R3, it is possible to protect the thyristors SCR1 and SCR2 from breakage of the forward breakdown voltage and to reliably protect against lightning surges.

  FIG. 2 shows another embodiment of the switching power supply device according to the present invention. In this embodiment, the inverter transformer 8 of the switching regulator circuit 5 is used as the gate circuit of the thyristors SCR1 and SCR2 provided in the inrush current prevention circuit 3. Auxiliary winding 8c is provided, and a voltage generated by the auxiliary winding 8c is rectified by a diode D5, and the thyristors SCR1 and SCR2 are driven and controlled as trigger signals.

  The configurations and operations of the surge protection circuits 12a and 12b, the active filter circuit 4 and the switching regulator circuit 5 provided for the thyristors SCR1 and SCR2 are the same as those in the embodiment of FIG.

  FIG. 3 is a circuit diagram showing another embodiment of the switching power supply device according to the present invention. In this embodiment, an inrush current prevention circuit is provided in the rectified output line of the diode bridge of the AC input stage. It is characterized by that.

  In FIG. 3, a diode bridge 2 of one circuit is provided following the AC input terminals 1a and 1b, a current limiting resistor R1 is provided on the rectified output line on the plus side of the diode bridge 2, and rectification is performed via the current limiting resistor R1. The output is input to the active filter circuit 4.

  A thyristor SCR1 is connected in parallel to the current limiting resistor R1. The gate circuit of the thyristor SCR1 includes an auxiliary winding L1 of a boost choke coil CH1 provided in the active filter circuit 4 and a rectifying diode D5.

  Here, the inrush current prevention circuit 3 includes a current limiting resistor R1, a thyristor SCR1, an auxiliary winding L1, and a diode D5. The active filter circuit 4 and the switching regulator circuit 5 are the same as those in the embodiment of FIG.

  A surge protection circuit 12 is provided for the thyristor SCR 1 provided in the inrush current prevention circuit 3. In the surge protection circuit 12, a diode D7, a Zener diode ZD1, and a resistor R2 are connected in series between the anode and gate of the thyristor SCR1.

  In the operation of the embodiment of FIG. 3, when AC power is supplied to the AC input terminals 1a and 1b by switching on or the like, the thyristor SCR1 is turned off at this time, so that the rectified output of the diode bridge 2 passes through the current limiting resistor R1. Are supplied to the active filter circuit 4 and the switching regulator circuit 5. For this reason, the inrush current which flows at the time of starting can be suppressed by the current limiting resistor R1.

  The active filter circuit 4 charges the capacitor C <b> 1 via the diode D <b> 3 at the time of activation, and the control circuit 6 operates in this state, and starts the inverter operation by switching of the transistor 7. In the switching regulator circuit 5, the control circuit 10 starts an inverter operation for setting the output voltage to a constant voltage by switching control of the FET 9.

  When the active filter circuit 4 enters the operating state after the transient state immediately after the power is turned on, a voltage is generated in the auxiliary winding L1 by switching of the boost choke coil CH1 by the transistor 7, and a trigger signal by rectification of the diode D5 is generated by the thyristor SCR1. In addition to the gate, the thyristor SCR1 is turned on, and an input line bypassing the current limiting resistor R1 is formed.

  When a surge voltage due to the lightning surge 13 is applied during operation, the Zener diode ZD1 of the surge protection circuit 12 becomes conductive, and a trigger current flows to the gate of the thyristor SCR1 via the diode D7, the Zener diode ZD1, and the resistor R2, and the thyristor SCR1. Is forcibly turned on to prevent a forward voltage breakover applied when the thyristor SCR1 is in an off state, and a surge current is forced from the thyristor SCR1 to a conductive state to flow through the diode D3 to the capacitor C1. In order to absorb surge.

  In the embodiment of FIG. 3, only one circuit of the diode bridge 2 and the thyristor SCR1 is provided. Therefore, the efficiency of the switching power supply apparatus is lower than that of the embodiment of FIGS. Become.

  FIG. 4 is a circuit diagram of another embodiment of the switching power supply device of the present invention. In this embodiment, a choke coil CH1 is used as a trigger circuit for the thyristor SCR1 provided in the inrush current prevention circuit 3 of FIG. Instead of the auxiliary winding L1, an auxiliary winding 8c of the inverter transformer 8 provided in the switching regulator circuit 5 is used. Other configurations and operations are the same as those in the embodiment of FIG.

  FIG. 5 is a circuit diagram showing another embodiment of the switching power supply device according to the present invention. In this embodiment, an inrush current prevention circuit and a surge protection circuit are provided on the AC input line to the diode bridge on the input side. It is characterized by that.

  In FIG. 5, a current limiting resistor R1 is provided on one of the input lines to the diode bridge 2 of the AC input terminals 1a and 1b, and a triac TR1 functioning as a bidirectional thyristor is connected in parallel with the current limiting resistor R1.

  As a trigger circuit for the gate of the triac TR1, the trigger signal is supplied by rectifying the voltage generated in the auxiliary winding L1 of the boost choke coil CH1 provided in the active filter circuit 4 by the diode D5.

  A surge protection circuit 12 is provided for the triac TR1, and the surge protection circuit 12 directly connects a diode D7, a Zener diode ZD1, and a resistor R2 between the cathode and the gate of the triac TR1.

  The rectified output of the diode bridge 2 is supplied to the active filter circuit 4 and the subsequent switching regulator circuit 5. The configurations and operations of the active filter circuit 4 and the switching regulator circuit 5 are the same as those in the embodiment of FIG.

  In the operation of the embodiment of FIG. 5, when AC power is supplied to the AC input terminals 1a and 1b by a switch operation or the like, the AC input to the diode bridge 2 flows through the current limiting resistor R1, thereby switching the active filter circuit 4 and the switching. The inrush current as an AC input accompanying the rectified output from the diode bridge 2 to the regulator circuit 5 is suppressed by limiting the AC current by the current limiting resistor R1.

  When the inverter operation of the active filter circuit 4 is started, a voltage is generated in the auxiliary winding L1 of the choke coil CH1, the triac TR1 is turned on in response to a trigger signal generated by the rectified output of the diode D5, and the current limiting resistor R1 is turned on. Bypassing and supplying an AC input to the diode bridge 2, the current limitation is released.

  Further, when a surge voltage is applied by the lightning surge 13 during the operation of the switching power supply device, the Zener diode ZD1 of the surge protection circuit 12 is turned on, and a trigger using the surge as a signal source through the diode D7, the Zener diode ZD1, and the resistor R2. Current flows to the gate of the triac TR1, and the triac TR1 is forcibly turned on, so that a breakdown voltage breakover due to a surge voltage applied in the off state of the triac TR1 is suppressed, and a surge current is caused to flow and be absorbed by the triac TR1 being forcibly turned on. .

  FIG. 6 is a circuit diagram showing another embodiment of the present invention. In this embodiment, the auxiliary winding 8c of the inverter transformer 8 provided in the switching regulator circuit 5 is provided in the trigger circuit of the inrush current prevention circuit 3. In FIG. Other features and operations are the same as those in the embodiment of FIG.

  The present invention may be an appropriate switching power supply device as long as it is a switching power supply device provided with an inrush current prevention circuit, and is a surge that turns on and forcibly turns on the thyristor of the inrush current prevention circuit when receiving a surge voltage. A protection circuit may be provided.

In addition, the above embodiment is an example of a switching power supply device including an active filter circuit and a switching regulator circuit. However, the above embodiment can be applied as it is to a device having only an active filter circuit and only a switching regulator circuit. it can.

The circuit diagram which showed embodiment of the switching power supply device by this invention provided with two inrush current prevention circuits The circuit diagram which showed other embodiment of the switching power supply device by this invention provided with two inrush current prevention circuits The circuit diagram which showed embodiment of the switching power supply device by this invention provided with one circuit of inrush current prevention The circuit diagram which showed other embodiment of the switching power supply device by this invention provided with one inrush current prevention circuit The circuit diagram which showed embodiment of the switching power supply device by this invention provided with the inrush current prevention circuit in the alternating current input line The circuit diagram which showed other embodiment of the switching power supply device by this invention provided with the inrush current prevention circuit in the alternating current input line

Explanation of symbols

1a, 1b: AC input terminals 2, 2a, 2b: Diode bridge 3: Inrush current prevention circuit 4: Active filter circuit 5: Switching regulator circuit 6, 10: Control circuit 7: Transistor 8: Inverter transformer 9: FET
11a, 11b: Output terminals 12, 12a, 12b: Surge protection circuit 13: Lightning surge SCR1, SCR2: Thyristor TR1: Triac R1: Current limiting resistors ZD1, ZD2: Zener diode CH1: Boost choke coil L1, 8c: Auxiliary winding SK1: Surge absorbing element

Claims (7)

An active filter circuit that performs switching control of the inverter so that the phases of the AC voltage and the AC current match when the AC input is rectified and DC output;
A switching regulator circuit that converts a DC input from the active filter circuit to a DC output of a constant voltage by switching with an inverter and supplies the load to a load; and
In a switching power supply device with
A thyristor connected in parallel to a current limiting resistor provided on an input line of the active filter circuit, and the thyristor is turned on based on an output of an auxiliary power source generated at the start of the operation of the active filter circuit or the switching regulator circuit; An inrush current prevention circuit for controlling and bypassing the current limiting resistor;
A switching power supply comprising a surge protection circuit for controlling conduction of a thyristor of the inrush current prevention circuit using a surge voltage as a signal source when a surge voltage applied to an input line of the active filter circuit is detected.
2. The switching power supply device according to claim 1, wherein the surge protection circuit includes a diode that rectifies a surge voltage between the anode terminal and the gate terminal of the thyristor and supplies a trigger signal to the gate terminal, and a predetermined Zener voltage. A switching power supply device comprising: a Zener diode that is turned on by application of a surge voltage that exceeds that; and a resistor that limits a trigger current flowing through the gate terminal.
2. The switching power supply device according to claim 1, wherein the inrush current prevention circuit is provided in a rectification output line of a full-wave rectification circuit provided on an input side of the active filter circuit.
4. The switching power supply device according to claim 3, wherein the thyristor of the inrush current prevention circuit is a unidirectional thyristor.
2. The switching power supply device according to claim 1, wherein the inrush current prevention circuit is provided on an AC input line of a full-wave rectifier circuit provided on an input side of the active filter circuit.
6. The switching power supply device according to claim 5, wherein the thyristor of the inrush current prevention circuit is a triac that functions as a bidirectional thyristor.
  2. The switching power supply device according to claim 1, wherein the auxiliary power supply of the inrush current prevention circuit is an auxiliary winding of an inverter coil provided in the active filter circuit or the switching regulator circuit. .

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