JP2011160508A - Switching power unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a long-life and compact switching power unit that reduces a loss of standby electric power, allows a drive circuit to properly change a rectification system of a rectifying circuit in response to an input voltage without using any high breakdown-voltage electrolytic capacitors. <P>SOLUTION: The switching power unit includes a triac 8 for switching whether the rectifying circuit 2 is operated by a voltage doubler rectifier system and the drive circuit 31 for drive to turn on or off the triac 8. The drive circuit 31 includes the rectifying circuit 32 for rectifying the input voltage Vin and a trigger generation circuit 38 for generating a trigger current for turning on or off the triac 8 with a rectifying output from the rectifying circuit 32 as a supply voltage. Rectifying output from the rectifying circuit 32 is taken in as it is as a supply voltage of the trigger generation circuit 38, and the triac 8 is driven by the trigger current generated by the trigger generation circuit 38. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an input automatic switching circuit for various electrical devices, and more particularly to a switching power supply apparatus including an input automatic switching circuit that detects a different input voltage and switches and controls the operation of a rectifier circuit so as to correspond to the input voltage. .

  Currently, the world's commercial power supply is divided into two regions, 100V and 200V. For example, Patent Literature 1 and Patent Literature 2 disclose an input automatic switching circuit that detects input voltages in different regions and controls switching of the operation of the rectifier circuit so as to correspond to the input voltages.

  In these Patent Documents 1 and 2, the rectifier circuit is configured by a diode bridge in which four diodes are bridge-connected, and a smoothing circuit in which two smoothing capacitors are connected in series is provided between the output terminals of the rectifier circuit. It has been. Further, a triac (bidirectional three-terminal thyristor) is connected as a switching element of the input automatic switching circuit between the connection point of the smoothing capacitor paired with one input terminal of the rectifier circuit, and the input voltage of the 100V system is In this case, the switching element is turned on and the rectifier circuit is set to a voltage doubler rectification method. On the other hand, when the input voltage is 200V, the switching element is turned off and the rectifier circuit is set to a full-wave rectification method. A desired DC voltage is always obtained between both ends of the smoothing circuit.

  In the automatic input switching circuit of Patent Document 1, a comparator such as an operational amplifier is incorporated in a switching element drive circuit. This comparator compares a detection voltage obtained by dividing the voltage across the smoothing circuit with a reference voltage set inside the drive circuit, and generates an operating voltage and a reference voltage for the comparator. In addition, a control power source is provided which rectifies the AC input voltage into DC and uses this as the power source voltage of the drive circuit.

  In addition, the input automatic switching circuit of Patent Document 2 also includes an operational amplifier having an equivalent function in the drive circuit of the switching element. Here, in order to rectify the AC input voltage to DC and use it as the power supply voltage of the drive circuit. A rectifying / smoothing circuit including a diode rectifier and an electrolytic capacitor is provided in the drive circuit.

Japanese Patent No. 3024330 JP-A-63-89061

  However, the above prior art has the following problems.

  In the automatic input switching circuit of Patent Document 1, since a voltage obtained by converting an AC input voltage into a direct current is used as the power supply voltage of the drive circuit, a fixed loss (standby power) always occurs in the control power supply that generates the power supply voltage.

  Further, in the automatic input switching circuit of Patent Document 2, it is necessary to use an electrolytic capacitor having a high withstand voltage that can withstand the application of an AC input voltage, and there is a problem in increasing the size and life of components in the drive circuit.

  Therefore, the present invention aims to reduce standby power loss and to appropriately switch the rectification method of the rectifier circuit in response to the input voltage without using a high-voltage electrolytic capacitor, thereby extending the life and It is an object of the present invention to provide a switching power supply device that can be miniaturized.

  In order to achieve the above object, the switching power supply device of the present invention is connected to a first rectifier circuit that rectifies an input voltage from an AC power supply, and whether or not the first rectifier circuit is operated in a voltage doubler rectification system. In the automatic input switching circuit comprising a switching element for switching between and a drive circuit for driving the switching element on or off, the drive circuit includes a second rectifier circuit for rectifying the input voltage, And a signal generation circuit for generating a drive signal for turning on or off the switching element, using a rectified output from the rectifier circuit as a power supply voltage.

  In this case, the switching element is a bidirectional three-terminal thyristor, and the signal generation circuit is an optical coupling comprising a light emitting element to which the power supply voltage is applied and a light receiving element connected to the gate of the bidirectional three-terminal thyristor. It is preferable to provide an element.

  The switching element may be an electromagnetic relay switch, and the electromagnetic relay may include a coil for opening and closing the switch.

  According to the switching power supply device of the present invention, the rectified output from the second rectifier circuit is directly taken as the power supply voltage of the signal generation circuit without rectifying and smoothing the input voltage from the AC power supply into a DC voltage. The switching element for switching whether or not to operate the first rectifier circuit by the voltage doubler rectification method can be driven by the drive signal generated by the signal generation circuit of the drive circuit. As a result, standby power loss is reduced as an automatic input switching circuit, and the drive circuit rectifies the first rectifier circuit in response to the input voltage without using a smoothing high-voltage electrolytic capacitor as in the prior art. The system can be switched appropriately, and the life and size can be reduced.

  According to the preferred switching power supply device of the present invention, when the input voltage is stopped for some reason, the light emitting element having the rectified output from the second rectifier circuit as the power supply voltage is also stopped at the same time, and the bidirectional three-terminal thyristor is immediately Can be turned off. Therefore, it is possible to prevent the occurrence of an inrush current due to the bidirectional three-terminal thyristor being kept on, particularly when the input voltage is turned on again after a momentary power failure.

  Further, according to the preferred switching power supply device of the present invention, the drive circuit can appropriately switch the rectification method of the first rectifier circuit using the electromagnetic relay.

1 is a circuit diagram of a switching power supply device including an automatic input switching circuit according to a first embodiment of the present invention. FIG. 4 is a waveform diagram of a trigger current generated by the trigger generation circuit. It is a circuit diagram of the switching power supply device including the input automatic switching circuit in 2nd Example of this invention.

  Hereinafter, a preferred circuit example of the automatic input switching circuit will be described in detail with reference to the accompanying drawings. In addition, the same code | symbol is attached | subjected to the same structure in each Example, and description of the same location is abbreviate | omitted as much as possible in order to avoid duplication.

  FIG. 1 is a circuit diagram of a switching power supply apparatus including an automatic input switching circuit according to a first embodiment of the present invention. In the figure, reference numeral 1 is an AC 100V system or AC 200V system commercial power source, which is an input power source, and 2 is a rectifier circuit for rectifying an AC input voltage Vin from the commercial power source 1, which includes four bridge-connected diodes (not shown). Z)). A smoothing circuit 5 in which two smoothing capacitors 3 and 4 are connected in series is connected between the output terminals of the rectifier circuit 2, and a DC voltage Vc generated between both ends of the smoothing circuit 5 is applied to a load (for example, not shown) , A DC-DC converter) is supplied to the load as an input voltage.

  As a switching element for switching the rectifier circuit 2 to either the full-wave rectifier system or the double voltage rectifier system between the connection points of the smoothing capacitors 3 and 4 paired with one input terminal of the rectifier circuit 2, a triac is used. (Bidirectional three-terminal thyristor) 8 is connected. Here, the first main terminal of the triac 8 is connected to one input terminal of the rectifier circuit 2, and the second main terminal of the triac 8 is connected to the connection point of the smoothing capacitors 3, 4. A series circuit of a resistor 9 and a light receiving element 13 of the phototriac 11 is connected between the main terminal and the gate, and a resistor 15 and a capacitor 16 are connected between the second main terminal of the triac 8 and the gate. A parallel circuit is connected. The resistors 9, 15 and the capacitor 16 are added as necessary to prevent erroneous firing of the triac 8, and together with the triac 8 and the photo triac 11, the operation of the rectifier circuit 2, that is, the rectification method is switched and controlled. A part of the automatic input switching circuit 21 is configured.

  Reference numeral 31 denotes a drive circuit that monitors the AC input voltage Vin and drives the triac 8 on or off. The drive circuit 31 monitors the rectification voltage 32 from the rectification circuit 32 that rectifies the AC input voltage Vin, and the rectification voltage level from the rectification circuit 32. A high-input detection circuit 33 that outputs a signal by judging that the input voltage Vin is applied, and a resistor 34, a light-emitting element 12 of the phototriac 11, a MOS-type FET 35, and a resistor 36 are sequentially connected in series to the output terminal of the rectifier circuit 32. And a constant current circuit 39 for controlling the MOS type FET 35 so that the trigger current generated by the trigger generation circuit 38 becomes a constant current using the rectified voltage from the rectifier circuit 32 as a power supply voltage, When the high input detection circuit 33 determines that the input is high and a pulse signal is output from the detection terminal D, the MOS FET 35 is turned on. Held in off state, composed of a latch circuit 40 for continuously stopping the trigger current flowing through the trigger generation circuit 38.

  The configuration of each part of the drive circuit 31 will be further described. The rectifier circuit 32 is configured by combining, for example, four bridge-connected diodes (not shown), and a full-wave rectified voltage is applied to the output terminal of the drive circuit 31. Generated as a power supply voltage. In addition, in order to reduce the loss of the rectifier circuit 32, another rectification method replacing the full-wave rectification method in the embodiment may be operated. The phototriac 11 constituting the trigger generation circuit 38 electrically insulates the trigger current generated by the trigger generation circuit 38 and transmits it to the gate of the triac 8. Specifically, the phototriac 11 is a light-emitting element made of a light-emitting diode. 12 and an optical gate input type triac. Other such optical coupling elements are known, but when the switching element is a triac 8 capable of flowing a current bidirectionally between main terminals, the optical coupling element of the trigger generation circuit 38 also uses the photo triac 11. preferable.

  Further, the MOS FET 35 connected in series with the light emitting element 12 of the phototriac 11 is provided as a switching element that enables or prevents the trigger current from flowing into the light emitting element 12. Here, when the gate voltage of the N-channel MOS type FET 35 becomes H (high) level, the MOS type FET 35 is turned on, and the trigger current using the full-wave rectification from the rectifier circuit 32 as a power source is passed through the resistor 34. On the other hand, when the gate voltage of the MOS type FET 35 becomes L (low) level while flowing into the light emitting element 12, the MOS type FET 35 is turned off, and the flow of the trigger current to the light emitting element 12 is cut off. As the switch element, a semiconductor element with various control terminals other than the MOS FET 35 may be used.

  In the constant current circuit 39, a resistor 45 and a parallel circuit including a Zener diode 46, a capacitor 47, and a resistor 48 are connected in series to the output terminal of the rectifier circuit 32, and a resistor 49 is connected to a connection point of the resistor 45 and the parallel circuit. The gate of the MOS FET 35 is connected via Here, the capacitor 47 only needs to be able to store charges that can turn on the MOS FET 35 and transistors 51 and 52 of the latch circuit 40 to be described later, and can have a withstand voltage much lower than that of a conventional electrolytic capacitor.

  The latch circuit 40 includes a thyristor in which the base and collector of the PNP transistor 51 are connected to the collector and base of the NPN transistor 52, respectively, and a resistor 53 connected between the base and emitter of the transistor 52, and the gate of the thyristor. The detection terminal D of the high input detection circuit 33 is connected to the base of the transistor 52 corresponding to, and the gate which is the control terminal of the MOS type FET 35 is connected to the emitter of the transistor 51 corresponding to the anode of the thyristor.

  Next, the operation of the above configuration will be described based on the waveform diagram of FIG. In FIG. 2, the upper stage is a rectified voltage waveform from the rectifier circuit 32, and the lower stage is a waveform of the trigger current generated by the trigger generation circuit 38.

  When the input voltage Vin from the commercial power source 1 starts to be applied, the input voltage Vin is rectified by the rectifier circuit 2 and the rectifier circuit 32 of the input automatic switching circuit 21, respectively. The rectified voltage from the rectifier circuit 2 is smoothed by the smoothing capacitors 3 and 4, but the rectified voltage from the rectifier circuit 32 is not smoothed by the high withstand voltage electrolytic capacitor as shown in the waveform diagram of FIG. The power supply voltage is supplied to the trigger generation circuit 38 and the constant current circuit 39 as they are.

  Here, when the commercial power supply 1 is an AC100V system low input, since the rectified voltage level from the rectifier circuit 32 is always below a predetermined value in the high input detection circuit 33, the detection pulse signal from the detection terminal D is The thyristor of the latch circuit 40 is turned off, and the constant current circuit 39 operates without being influenced by the latch circuit 40. Therefore, when the rectified voltage from the rectifier circuit 32 rises from 0 V, the constant current circuit 39 charges the capacitor 47 through the resistor 45, maintains the voltage across the capacitor 47 at the zener voltage of the zener diode 46, and rectifies When the rectified voltage from the circuit 32 decreases and approaches 0 V, the operation of discharging the charge accumulated in the capacitor 47 with the resistor 48 is repeated, so that the current flowing from the drain to the source of the MOS FET 35 (that is, in the trigger generation circuit 38). The trigger current flowing from the rectifier circuit 32 through the resistor 34 and the light emitting element 12 into the MOS type FET 35 in this order is connected to the capacitor 47 via the resistor 49 so that it becomes a constant value except near the zero cross of the input voltage Vin. The gate voltage of the MOS type FET 35 to be controlled is controlled.

  Thus, when a trigger current under constant current control as shown in FIG. 2 is generated in the trigger generation circuit 38, the trigger current is signal-transmitted from the light emitting element 12 of the phototriac 11 to the light receiving element 13. Therefore, when the trigger current increases and reaches the trigger level of the triac 8, the triac 8 is turned on, and the connection between one input terminal of the rectifier circuit 2 and the connection point of the smoothing capacitors 3 and 4 is conducted. The circuit 2 performs voltage doubler rectification by the action of the smoothing capacitors 3 and 4 connected in series, and generates a required DC voltage Vc across the smoothing capacitors 3 and 4.

  On the other hand, when the commercial power source 1 is an AC200V system high input, the high input detection circuit 33 periodically exceeds the predetermined value of the rectified voltage level from the rectifier circuit 32, and a pulse signal is repeatedly output from the detection terminal D. . When this happens, a pulse signal is applied to the gate of the thyristor constituting the latch circuit 40, the thyristor is turned on, the gate voltage of the MOS FET 35 under constant current control is set to L level, and the MOS FET 35 is turned off. .

  When the MOS type FET 35 is kept off by the latch circuit 40, no trigger current is generated in the trigger generation circuit 38, the triac 8 is turned off, and the connection between one input terminal of the rectifier circuit 2 and the smoothing capacitors 3 and 4 is established. It becomes non-conductive between points. Therefore, in this case, the voltage that has been full-wave rectified by the rectifier circuit 2 is smoothed by the smoothing capacitors 3 and 4, and a DC voltage Vc equivalent to that during double voltage rectification is generated across the smoothing capacitors 3 and 4.

  In the circuit configuration in which the triac 8 and the photo triac 11 shown in FIG. 1 are combined, when the input voltage Vin is stopped for some reason, the triac 8 is immediately turned off. This is because the power supply voltage for operating the light-emitting element 12 of the phototriac 11 is the full-wave rectified voltage from the rectifier circuit 32, so that the full-wave rectified voltage is also stopped at the same time as the input voltage Vin is stopped. Because it stops. Therefore, when the input voltage Vin is momentarily stopped and then turned on again, the triac 8 turned off when the input voltage Vin is turned off is turned on again by zero cross detection by the phototriac 11 when the input voltage Vin is turned on again, and rectified. The operation of the voltage doubler rectification method by the circuit 2 can be resumed. That is, when the input voltage Vin is instantaneously stopped, the operation of the voltage doubler rectification method by the rectifier circuit 2 does not stop immediately, and if the input voltage Vin is turned on again while the triac 8 is kept on, the inrush current to the load In the circuit shown in FIG. 1, since the rectified voltage from the rectifier circuit 32 is a power supply voltage for operating the light emitting element 12 of the phototriac 11, it is possible to prevent such an inrush current from occurring. it can.

  As described above, in this embodiment, the rectifier circuit 2 is connected to the rectifier circuit 2 that is the first rectifier circuit that rectifies the input voltage Vin from the commercial power source 1 that is an AC power source. A second rectifier circuit for rectifying the input voltage Vin in the input automatic switching circuit 21 of the switching power supply device including the triac 8 as a switching element for switching whether or not and the drive circuit 31 for driving the triac 8 on or off. A rectifier circuit 32, and a trigger generation circuit 38 as a signal generation circuit that generates a drive signal (trigger current) for turning on or off the triac 8 using a rectified output from the rectifier circuit 32 as a power supply voltage, The drive circuit 31 is provided.

  In this case, the AC input voltage Vin is not rectified and smoothed into a DC voltage, but the rectified output from the rectifier circuit 32 is directly used as the power supply voltage of the trigger generation circuit 38, so that the rectifier circuit 2 operates in a voltage doubler rectification system. The TRIAC 8 that switches whether or not to be driven can be driven by the trigger current generated by the trigger generation circuit 38 of the drive circuit 31. Therefore, the standby power loss is reduced as the automatic input switching circuit 21 and the drive circuit 31 rectifies the rectifier circuit 2 in response to the input voltage Vin without using a conventional high-voltage electrolytic capacitor for smoothing. It becomes possible to switch the method appropriately.

  In particular, the switching element of the present embodiment is a triac 8, and the trigger generation circuit 38 is an optical coupling element including the light emitting element 12 to which the power supply voltage is applied and the light receiving element 13 connected to the gate of the triac 8. The photo triac 11 is provided.

  In this case, when the input voltage Vin stops for some reason, the light emitting element 12 using the rectified output from the rectifier circuit 32 as the power supply voltage also stops light emission at the same time, and the triac 8 can be immediately turned off. Therefore, it is possible to prevent the occurrence of an inrush current due to the TRIAC 8 being kept on, particularly when the input voltage Vin is turned on again after a momentary power failure.

  FIG. 3 is a circuit diagram of a power supply apparatus including an automatic input switching circuit according to the second embodiment of the present invention. In this figure, the switching element is not a triac 8 but a switch 62 of an electromagnetic relay 61, and a trigger generation circuit 38 connects a coil 63 of the electromagnetic relay 61, a MOS type FET 35, and a resistor 36 in series. Configured. The coil 63 of the electromagnetic relay 61 is wound around an iron core (not shown) as a core, and the switch 62 is electromagnetically opened and closed by a trigger current flowing through the coil 63. The trigger current is less than a predetermined value. Then, the switch 62 is opened and turned off, and when the trigger current exceeds a predetermined value, the switch 62 is closed and turned on. Other configurations are the same as those in the first embodiment.

  Also in this embodiment, when the input voltage Vin from the commercial power source 1 starts to be applied, the input voltage Vin is rectified by the rectifier circuit 2 and the rectifier circuit 32 of the input automatic switching circuit 21, respectively. The rectified voltage from the rectifier circuit 2 is smoothed by the smoothing capacitors 3 and 4, but the rectified voltage from the rectifier circuit 32 is not smoothed by the high withstand voltage electrolytic capacitor as shown in the waveform diagram of FIG. The power supply voltage is supplied to the trigger generation circuit 38 and the constant current circuit 39 as they are.

  Here, when the commercial power source 1 is an AC100V low input, no pulse signal is output from the detection terminal D of the high input detection circuit 33, the thyristor of the latch circuit 40 is turned off, and the constant current circuit 39 is latched. The circuit 40 operates without being affected by the circuit 40. Therefore, the constant current circuit 39 is configured so that the trigger current flowing from the rectifier circuit 32 through the coil 63 of the electromagnetic relay 61 into the MOS FET 35 in order is a constant value except for the vicinity of the zero cross of the input voltage Vin. Control the gate voltage. 2 is generated in the trigger generation circuit 38, and when the trigger current exceeds a certain value, the switch 62 of the electromagnetic relay 61 is closed. As a result, the connection between one input terminal of the rectifier circuit 2 and the connection point of the smoothing capacitors 3 and 4 is conducted, and the rectifier circuit 2 performs double voltage full-wave rectification by the action of the smoothing capacitors 3 and 4 connected in series. The required DC voltage Vc is generated between both ends of the smoothing capacitors 3 and 4.

  On the other hand, when the commercial power source 1 is an AC200V system high input, since the pulse signal is repeatedly output from the detection terminal D of the high input detection circuit 33, the gate voltage of the MOS FET 35 under constant current control is set to the L level. Thus, the MOS FET 35 is turned off. When the MOS FET 35 is kept off by the latch circuit 40, no trigger current is generated in the trigger generation circuit 38, the switch 62 of the electromagnetic relay 61 is opened, and one input terminal of the rectifier circuit 2 and the smoothing capacitor 3, No connection between the four connection points. Therefore, in this case, the voltage that has been full-wave rectified by the rectifier circuit 2 is smoothed by the smoothing capacitors 3 and 4, and a DC voltage Vc equivalent to that during double voltage rectification is generated across the smoothing capacitors 3 and 4.

  In the waveform diagram of FIG. 2, the trigger current is below a predetermined value near the zero cross of the input voltage Vin, but the electromagnetic relay 61 used here opens and closes the switch 62 after the current flowing through the coil 63 changes. Since the time lag until switching is large, the switch 62 does not turn off even near the zero cross of the input voltage Vin. Thereby, the lifetime reduction of the electromagnetic relay 61 by the switch 62 opening and closing periodically can be prevented.

  As another means, a circuit that raises the trigger current level near the zero cross of the input voltage Vin may be incorporated in the drive circuit 31. In this case, if the electromagnetic relay 61 having a lower trigger current level at which the switch 62 is switched from on to off than the trigger current level at which the switch 62 is switched from off to on, the electromagnetic relay 61 based on the same cause is used. It is possible to reliably prevent a decrease in life.

  As described above, in this embodiment, the switching element is connected to the rectifier circuit 2 that rectifies the input voltage Vin from the commercial power source 1 that is an AC power source, and switches whether the rectifier circuit 2 is operated by the double voltage rectification method. In the automatic input switching circuit 21 including a switch 62 of the electromagnetic relay 61 and a drive circuit 31 that drives the switch 62 on or off, a rectifier circuit 32 that rectifies the input voltage Vin, The drive circuit 31 includes a trigger generation circuit 38 that generates a trigger current for turning on or off the switch 62 of the electromagnetic relay 61 using the rectified output of the power supply voltage as a power supply voltage.

  In this case, the AC input voltage Vin is not rectified and smoothed into a DC voltage, but the rectified output from the rectifier circuit 32 is directly used as the power supply voltage of the trigger generation circuit 38, so that the rectifier circuit 2 operates in a voltage doubler rectification system. It is possible to drive the switch 62 of the electromagnetic relay 61 that switches whether or not to perform the trigger current generated by the trigger generation circuit 38 of the drive circuit 31. Therefore, the standby power loss is reduced as the automatic input switching circuit 21 and the drive circuit 31 rectifies the rectifier circuit 2 in response to the input voltage Vin without using a conventional high-voltage electrolytic capacitor for smoothing. The system can be switched appropriately, and the life and size can be reduced.

  The switching element of this embodiment is a switch 62 of an electromagnetic relay 61. The electromagnetic relay 61 includes a coil 63 for opening and closing the switch 62, and the trigger generation circuit 38 is applied with the power supply voltage. A coil 63 of the electromagnetic relay 61 is provided.

  In this case, the drive circuit 31 can appropriately switch the rectification method of the rectifier circuit 2 using the electromagnetic relay 61.

  The present invention is not limited to the present embodiment, and various modifications can be made within the scope of the gist of the present invention. The voltage double here is not limited to twice, but also includes a voltage of an integer multiple higher than that. Moreover, the rectifier circuit 2 may operate another rectification method instead of the full-wave rectification method in the embodiment.

1 Commercial power supply (AC power supply)
2 Rectifier circuit (first rectifier circuit)
8 Triac (switching element)
11 Phototriac (Optical coupling device)
12 Light emitting element 13 Light receiving element 32 Rectifier circuit (second rectifier circuit)
38 Trigger generation circuit (signal generation circuit)
61 Electromagnetic relay 62 Switch (switching element)
63 coils

Claims (3)

A switching element that is connected to a first rectifier circuit that rectifies an input voltage from an AC power supply, and that switches whether or not the first rectifier circuit is operated in a double voltage rectifier system;
In a switching power supply device comprising: a drive circuit that drives the switching element on or off;
The drive circuit includes a second rectifier circuit that rectifies the input voltage, and a signal generation circuit that generates a drive signal for turning on or off the switching element using a rectified output from the second rectifier circuit as a power supply voltage. And a switching power supply device. The switching element is a bidirectional three-terminal thyristor;
2. The switching according to claim 1, wherein the signal generation circuit includes an optical coupling element including a light emitting element to which the power supply voltage is applied and a light receiving element connected to a gate of the bidirectional three-terminal thyristor. Power supply.   2. The switching power supply device according to claim 1, wherein the switching element is a switch of an electromagnetic relay, and the electromagnetic relay includes a coil for opening and closing the switch.

Images