JP7413301B2 - switching power supply - Google Patents

Description

The present invention relates to a half-bridge type or full-bridge type switching power supply device including a snubber circuit for reducing surge voltage of a switching element.

First, general half-bridge converters and full-bridge converters will be briefly explained. The switching power supply device 10 shown in FIG. 5A is an example of a non-resonant half-bridge type converter. The switching power supply device 10 has an input line 14 and a ground line 16 to which an input voltage Vi is supplied from an input power supply 12, and a series circuit of two switching elements 18a and 18b is connected between the input line 14 and the ground line 16. A first arm 18 consisting of is connected. The input winding 20a of the transformer 20 has one end connected to the midpoint of the first arm 18, and the other end connected to the ground line 16 via a bias capacitor 22. The bias capacitor 22 is a capacitor that biases the other end of the input winding 20a to a potential of Vi/2 with respect to the ground line 16. Here, one end is connected to the ground line 16, but the input line 14 It may also be connected to.

A bypass capacitor circuit 24 is connected between the input line 14 and the ground line 16. The bypass capacitor circuit 24 is a circuit that suppresses the switching current flowing through the first arm 18 from flowing out to the input power supply 12 side. Here, the bypass capacitor circuit 24 is composed of a series circuit of two bypass capacitors 24a and 24b having the same capacity. ing.

In general, capacitor elements with lower withstand voltages are becoming smaller and have larger capacities. In addition, high dielectric constant ceramic capacitors have the property that their capacitance decreases significantly when a bias close to the rated voltage is applied, so when using a ceramic capacitor, make sure that the bias is sufficiently higher than the rated voltage during actual use. It is preferable to make it low. Therefore, when configuring a smoothing or decoupling capacitor circuit, it is better to configure it by connecting multiple low voltage products in series than to configure it with a single high voltage product. There are times when it is advantageous to aim for this. Therefore, the bypass capacitor circuit 24 has a configuration in which two capacitor elements with low breakdown voltage and large capacity are connected in series.

Assuming that the voltages generated in the bypass capacitors 24a and 24b are V24a and V24b, respectively, it is assumed in design that the output voltage Vi is divided by the ratio of each capacitance, so that V24a=V24b=Vi/2. Note that when there is a possibility that the voltage division ratio of the capacitors 24a and 24b varies due to variations in capacitance or leakage current, a balance resistor (not shown) is connected in parallel to each capacitor element.

A rectifying and smoothing circuit 26 is connected to both ends of the output winding 20b of the transformer 20. The rectifying and smoothing circuit 26 is a circuit that rectifies and smoothes the voltage generated in the output winding 20b to generate an output voltage Vo. The load 28 to which the output voltage Vo and output current are supplied is an electronic device or the like externally connected to the switching power supply 10, or a circuit network built into the switching power supply 10.

Although the switching power supply device 10 is a non-resonant type converter, it can be changed to a current resonant type converter by providing a current resonance capacitor in series with the input winding 20a of the transformer 20. In this case, it is common to make the bias capacitor 22 also function as a current resonance capacitor by reducing the capacitance of the bias capacitor 22 (a capacitor that biases one end of the input winding 20a to a potential of Vi/2). It is. For example, the switching power supply device disclosed in Patent Document 1 is a current resonance half-bridge type converter, and is provided with a current resonance capacitor Ci and a bias capacitor Ci in series with the input winding Lp. Further, a polar capacitor provided after the input rectifier corresponds to a bypass capacitor circuit.

The switching power supply device 30 shown in FIG. 5(b) is another example of a non-resonant half-bridge type converter. The switching power supply device 30 has many features in common with the switching power supply device 10, but the difference is that the bias capacitor 22 is omitted, and the input winding 20a of the transformer 20 is connected to the middle point of the first arm 18 and the bypass capacitor circuit 24. It is a point connected between the midpoint of That is, in the case of the switching power supply device 30, the operation of biasing one end of the input winding 20a to the potential of Vi/2 is performed by the bypass capacitor circuit 24 instead of the bias capacitor 22. The configuration of other parts is the same as that of the switching power supply device 10.

Although the switching power supply device 30 is a non-resonant type converter, it can be changed to a current resonant type converter by inserting a current resonance capacitor (not shown) in series with the input winding 20a of the transformer 20. can be done. For example, the power converter disclosed in Patent Document 2 is a current resonance half-bridge type converter, and is provided with a current resonance capacitor Cr in series with the input winding N1. Further, a series circuit of capacitors Cdc1 and Cdc2 provided in parallel with the input power supply Ed corresponds to a bypass capacitor circuit.

The switching power supply device 32 shown in FIG. 6 is an example of a full-bridge type converter. The switching power supply device 32 has a first arm 18 formed of a series circuit of two switching elements 18a and 18b and a second arm 18 formed of a series circuit of two switching elements 34a and 34b between the input line 14 and the ground line 16. The arm 34 is connected. The input winding 20a of the transformer 20 is connected between the midpoint of the first arm 18 and the midpoint of the second arm 34.

A bypass capacitor circuit 24 (bypass capacitors 24a, 24b) is connected between the input line 14 and the ground line 16, as described above. The bypass capacitor circuit 24 is a circuit that suppresses the switching current flowing through the first arm 18 and the second arm 34 from flowing out to the input power supply 12 side. Further, a rectifying and smoothing circuit 26 similar to the above is connected to both ends of the output winding 20b of the transformer 20.

A full-bridge type converter similar to the switching power supply device 32 is disclosed in, for example, Patent Document 3. In the case of the DC power converter of Patent Document 3, the capacitor Cp provided in parallel with the input power supply 1 corresponds to a bypass capacitor circuit.

Although the switching power supply device 32 is a non-resonant type converter, it can be changed to a current resonant type converter by inserting a current resonance capacitor (not shown) in series with the input winding 20a of the transformer 20. can be done.

Japanese Patent Application Publication No. 2012-170218 JP2017-204972A Japanese Patent Application Publication No. 2005-168266

In a switching power supply device, since each switching element performs a switching operation, a surge voltage (or ringing voltage) is generated across each switching element regardless of whether it is a half-bridge type or a full-bridge type. Even if a current resonance type is used, it is difficult to completely eliminate surge voltage. Therefore, a snubber circuit for reducing surge voltage is usually connected to both ends of each switching element.

For example, in the case of the half-budge type switching power supply devices 10 and 30 shown in FIGS. 5A and 5B, snubber circuits 36a and 36b are individually connected to the two switching elements 18a and 18b. Therefore, if one snubber circuit is composed of a capacitor element and a resistor element, a total of four snubber-dedicated elements are required.

Further, in the case of the full-bridge type switching power supply device 32 shown in FIG. 6, snubber circuits 36a, 36b, 36c, and 36d are individually connected to the four switching elements 18a, 18b, 34a, and 34b. Therefore, if one set of snubber circuits is composed of a capacitor and a resistor, a total of eight snubber-dedicated elements are required.

As described above, since the half-bridge method and the full-bridge method include a plurality of switching elements, there has been a problem in that each switching element snubber circuit has a large number of parts.

The present invention has been made in view of the above-mentioned background art, and provides a half-bridge type or full-bridge type switching power supply device equipped with a simple snubber circuit that can effectively reduce the surge voltage of a switching element. With the goal.

The present invention includes an input line and a ground line to which an input voltage is supplied from an input power source, a first arm consisting of a series circuit of two switching elements connected between the input line and the ground line, and an input winding. a transformer having a wire and an output winding, one end of the input winding being connected to the midpoint of the first arm; A bias capacitor connected between the other end and the ground line, and a circuit for suppressing a switching current flowing through the switching element from flowing out to the input power supply side, the circuit including a bias capacitor connected between the input line and the ground line. a bypass capacitor circuit consisting of a series circuit of two bypass capacitors connected to the line; a rectifier and smoothing circuit that rectifies and smoothes the voltage generated in the output winding to generate an output voltage; and the bypass capacitor circuit. a first snubber circuit connected between a midpoint and a midpoint of the first arm to reduce surge voltage generated across each switching element of the first arm , the bypass capacitor comprising: This is a half-bridge type switching power supply device in which an aluminum electrolytic capacitor and a ceramic capacitor having a smaller capacity than the aluminum electrolytic capacitor are connected in parallel . In each bypass capacitor of the bypass capacitor circuit, a midpoint of the aluminum electrolytic capacitor and a midpoint of the ceramic capacitor may be separated. The bias capacitor may also be used as a current resonance capacitor.

The present invention also provides a first arm comprising an input line and a ground line to which an input voltage is supplied from an input power source, and a series circuit of two switching elements connected between the input line and the ground line; A transformer having an input winding and an output winding, one end of the input winding being connected to the middle point of the first arm, and suppressing a switching current flowing through the switching element from flowing to the input power source side. a bypass capacitor circuit comprising a series circuit of two bypass capacitors connected between the input line and the ground line, the other end of the input winding being connected to the midpoint of the series circuit; , a rectifying and smoothing circuit that rectifies and smoothes the voltage generated in the output winding to generate an output voltage; and a rectifying and smoothing circuit that is connected between the midpoint of the bypass capacitor circuit and the midpoint of the first arm; and a first snubber circuit for reducing surge voltage generated across each of the switching elements , and the bypass capacitor is configured by connecting an aluminum electrolytic capacitor and a ceramic capacitor having a smaller capacity than the aluminum electrolytic capacitor in parallel. This is a half-bridge switching power supply. A current resonance capacitor may be provided in series with the input winding.

The present invention also provides a first arm comprising an input line and a ground line to which an input voltage is supplied from an input power source, and a series circuit of two switching elements connected between the input line and the ground line; The second arm includes a series circuit of two switching elements connected between the input line and the ground line, and has an input winding and an output winding, and the input winding is connected to the first arm. a transformer connected between a midpoint and a midpoint of the second arm;
a circuit for suppressing the switching current flowing through the switching element from flowing out to the input power source side, the bypass comprising a series circuit of two bypass capacitors connected between the input line and the ground line; a capacitor circuit, a rectifier and smoothing circuit that rectifies and smoothes the voltage generated in the output winding to generate an output voltage, and is connected between the midpoint of the bypass capacitor circuit and the midpoint of the first arm; a first snubber circuit that reduces surge voltage generated across each of the switching elements of the first arm; and a first snubber circuit connected between the midpoint of the bypass capacitor circuit and the midpoint of the second arm; and a second snubber circuit for reducing the surge voltage generated across each of the switching elements.

A current resonance capacitor may be provided in series with the input winding. Further, the bypass capacitor can be configured such that an aluminum electrolytic capacitor and a ceramic capacitor having a smaller capacity than the aluminum electrolytic capacitor are connected in parallel.

The switching power supply device of the present invention includes a simple snubber circuit that uses a bypass capacitor circuit to bypass switching current. By operating this unique snubber circuit, surge voltage generated across the switching element can be easily and effectively removed. can be reduced.

1 is a circuit diagram showing a configuration of a first embodiment of a switching power supply device of the present invention, in which FIG. 1A is a circuit diagram showing a non-resonant type configuration, and FIG. 1B is a circuit diagram showing a current resonance type configuration. FIG. 2 is a circuit diagram showing the configuration of a second embodiment of the switching power supply device of the present invention, in which FIG. 1A is a circuit diagram showing a non-resonant type configuration, and FIG. FIG. 2 is a circuit diagram showing a configuration of a third embodiment of a switching power supply device of the present invention, in which FIG. 1A is a circuit diagram showing a non-resonant type configuration, and FIG. 1(a) and (b) are circuit diagrams showing two modified examples of the switching power supply device shown in FIG. 1(a). FIGS. 2A and 2B are circuit diagrams showing the configuration of a conventional half-bridge switching power supply device. FIGS. FIG. 1 is a circuit diagram showing the configuration of a conventional full-bridge switching power supply device.

Hereinafter, a first embodiment of a switching power supply device of the present invention will be described based on FIGS. 1(a) and (b). Here, the same configuration as the conventional switching power supply device 10 is given the same reference numeral, and the description thereof will be omitted.

The switching power supply 38 of this embodiment is a non-resonant half-bridge type converter, as shown in FIG. 1(a). The difference from the conventional switching power supply device 10 is that the two snubber circuits 36 connected to both ends of the switching elements 18a and 18b are removed, and the snubber circuits 36 connected to both ends of the switching elements 18a and 18b are removed, and the snubber circuits 36 are connected between the midpoint of the first arm 18 and the bypass capacitor circuit 24. The point is that one first snubber circuit 40 is connected to. The first snubber circuit 40 includes a capacitor 40a and a resistor 40b, and the capacitance of the capacitor 40a is set to a value sufficiently smaller than the capacitance of the bypass capacitors 24a and 24b. The configuration of other parts is the same as that of the switching power supply device 10.

In the case of the switching power supply 38, when surge voltage (or ringing voltage) energy is generated across the switching element 18a, it passes through the switching element 18a, the resistor 40b, the capacitor 40b, and the bypass capacitor 24a in this order and returns to the switching element 18a. A current that releases surge energy (hereinafter referred to as a snubber current) flows in the path or the path in the opposite direction. Then, as the snubber current flows through the capacitor 40b and the resistor 40b, the peak value of the surge voltage of the switching element 18a is suppressed, and the ringing is quickly attenuated. Note that the capacitance of the bypass capacitor 24a is sufficiently larger than that of the capacitor 40b, so the voltage at the midpoint of the bypass capacitor circuit 24 is maintained at DC Vi/2, and the magnitude of the snubber current is determined by the capacitance of the bypass capacitor 24a. It is almost determined by the capacitance of the capacitor 40b.

Furthermore, when surge voltage (or ringing voltage) energy is generated across the switching element 18b, a path from the switching element 18b that passes through the resistor 40b, the capacitor 40b, and the bypass capacitor 24b in order and returns to the switching element 18a, or A snubber current that releases surge energy flows in the opposite direction. Then, as the snubber current flows through the capacitor 40b and the resistor 40b, the peak value of the surge voltage of the switching element 18b is suppressed, and the ringing is quickly attenuated. Note that the capacitance of the bypass capacitor 24b is sufficiently larger than that of the capacitor 40b, so the voltage at the midpoint of the bypass capacitor circuit 24 is maintained at DC Vi/2, and the magnitude of the snubber current is determined by the capacitance of the bypass capacitor 24b. It is almost determined by the capacitance of the capacitor 40b.

As described above, according to the switching power supply device 38, the energy of the surge voltage of the two switching elements 18a and 18b is well absorbed by the first snubber circuit 40, and the same surge voltage reduction effect as the conventional switching power supply device 10 can be achieved. Obtainable. Moreover, while the conventional switching power supply 10 requires four snubber-dedicated elements (two capacitor elements and two resistance elements), the switching power supply 38 of this embodiment requires two snubber-dedicated elements ( Since it is only necessary to provide the capacitor 40a and the resistor 40b, the number of snubber-dedicated elements can be halved compared to the conventional one. In addition, in the case of the switching power supply device 38, since the bias capacitors 24a and 24b whose voltage at both ends is maintained at Vi/2 are present in the snubber current path, the voltage applied to both ends of the capacitor 40a is approximately 1/2 that of the conventional one. The capacitor 40a has the advantage that a small and inexpensive capacitor element with low withstand voltage can be used.

The switching power supply device 38k shown in FIG. 1(b) is changed to a current resonance half-bridge type converter by providing a current resonance capacitor 42 in series with the input winding 20a of the switching power supply device 38. be. Here, the bias capacitor 22 and the current resonance capacitor 42 are used together, and by reducing the capacitance of the bias capacitor 22, the bias capacitor 22 also functions as the current resonance capacitor 42. Note that in FIG. 1(b), the resonant inductor 44 is shown at a position in series with the input winding 20a, but if it can be replaced with a leakage inductor inside the transformer 20, the resonant inductor 44 can be deleted. . The same effects as those of the switching power supply device 38 can also be obtained in the switching power supply device 38k.

Next, a second embodiment of the switching power supply device of the present invention will be described based on FIGS. 2(a) and 2(b). Here, the same configuration as the conventional switching power supply device 30 is given the same reference numeral and the explanation thereof will be omitted.

The switching power supply 46 of this embodiment is a non-resonant half-bridge type converter, as shown in FIG. 2(a). What is different from the conventional switching power supply device 30 is that the two snubber circuits 36 connected to both ends of the switching elements 18a and 18b are removed, and the snubber circuits 36 connected to both ends of the switching elements 18a and 18b are removed, and The point is that one first snubber circuit 40 is connected to. The first snubber circuit 40 includes a capacitor 40a and a resistor 40b, and the capacitance of the capacitor 40a is set to a value sufficiently smaller than the capacitance of the bypass capacitors 24a and 24b. The configuration of other parts is similar to the switching power supply device 30.

The operation of the first snubber circuit 40 of the switching power supply 46 is similar to the operation of the first snubber circuit 40 of the switching power supply 38 described above, and it is possible to obtain the same surge voltage reduction effect as the conventional switching power supply 30. I can do it. Further, the number of dedicated snubber elements can be halved compared to the conventional one, and a small and inexpensive capacitor element with a lower withstand voltage than the conventional one can be used as the capacitor 40a.

The switching power supply device 46k shown in FIG. 2(b) is changed to a current resonance half-bridge type converter by providing a current resonance capacitor 42 in series with the input winding 20a of the switching power supply device 46. be. Note that in FIG. 2(b), the resonant inductor 44 is shown in a position in series with the input winding 20a, but if it can be replaced with a leakage inductor inside the transformer 20, the resonant inductor 44 can be deleted. . The same effects as those of the switching power supply device 46 can also be obtained in the switching power supply device 46k.

Next, a third embodiment of the switching power supply device of the present invention will be described based on FIGS. 3(a) and 3(b). Here, the same configuration as the conventional switching power supply device 32 is given the same reference numeral and the explanation thereof will be omitted.

The switching power supply 48 of this embodiment is a non-resonant full-bridge converter, as shown in FIG. 3(a). The difference from the conventional switching power supply device 32 is that the two snubber circuits 36 connected to both ends of the switching elements 18a and 18b are removed, and the snubber circuits 36 connected to both ends of the switching elements 18a and 18b are removed, and the snubber circuits 36 are connected between the midpoint of the first arm 18 and the bypass capacitor circuit 24. and one second snubber circuit 50 is connected between the midpoint of the second arm 34 and the midpoint of the bypass capacitor circuit 24. . The first snubber circuit 40 includes a capacitor 40a and a resistor 40b, and the capacitance of the capacitor 40a is set to a value sufficiently smaller than the capacitance of the bypass capacitors 24a and 24b. Similarly, the second snubber circuit 50 includes a capacitor 50a and a resistor 50b, and the capacitance of the capacitor 50a is set to a value sufficiently smaller than the capacitance of the bypass capacitors 24a and 24b.

The operation of the first snubber circuit 40 of the switching power supply 48 is similar to the operation of the first snubber circuit 40 of the switching power supply 38 described above, and the same surge voltage reduction effect as the conventional switching power supply 32 can be obtained. . Further, the operation of the second snubber circuit 50 is also similar, and the same surge voltage reduction effect as the conventional switching power supply device 32 can be obtained. Furthermore, the number of snubber-dedicated elements can be halved compared to the conventional one, and the capacitors 40a and 50a can be small and inexpensive capacitor elements with lower withstand voltage than the conventional ones.

The switching power supply 48k shown in FIG. 3(b) is changed to a current resonance full-bridge type converter by providing a current resonance capacitor 42 in series with the input winding 20a of the switching power supply 48. be. Note that in FIG. 3(b), the resonant inductor 44 is shown at a position in series with the input winding 20a, but if it can be replaced with a leakage inductor inside the transformer 20, the resonant inductor 44 can be deleted. . The same effects as those of the switching power supply device 48 can also be obtained in the switching power supply device 48k.

Note that the switching power supply device of the present invention is not limited to the above embodiment. For example, the first snubber circuit 40 described above includes a resistor 40b, which is a discrete component, but if the resistor 40b can be replaced with a resistance component of a wiring pattern in the path through which the snubber current flows, a resistance component of the capacitor 40a, etc. Can be omitted. The same applies to the resistor 50b of the second snubber circuit 50.

Although omitted in the above description of the switching power supply devices 38, 38k, 46, and 46k, the bypass capacitors 24a and 24b of the bypass capacitor circuit 24 included in these devices are each provided by connecting two capacitor elements in parallel. Specifically, as shown in FIG. 4(a), the bypass capacitor 24a is a large-capacity aluminum electrolytic capacitor 24a(1) and a small-capacity ceramic capacitor 24a(2) connected in parallel. The capacitor 24b can be a large-capacity aluminum electrolytic capacitor 24b(1) and a small-capacity ceramic capacitor 24b(2) connected in parallel. In general, aluminum electrolytic capacitors are characterized by their ability to provide large capacitance at low cost, and ceramic capacitors are characterized by their ability to have extremely low impedance in high frequency bands exceeding several hundred kHz. Therefore, by connecting two types of capacitor elements in parallel, it becomes possible to more reliably bypass the switching current containing many harmonic components. In this case, the capacitance of the ceramic capacitors 24a(1) and 24b(2) is made sufficiently larger than that of the capacitor 40a.

Further, as shown in FIG. 4(b), the midpoint of the aluminum electrolytic capacitors 24a(1), 24b(1) and the midpoint of the ceramic capacitors 24a(1), 24b(2) are separated, and the ceramic capacitor 24a( 1) and 24b(2), one end of the snubber circuit 40 may be connected to the midpoint. In this configuration as well, the same operation as in the configuration shown in FIG. It becomes possible to arrange the ceramic capacitors 24a(1) and 24b(2), which are placed at separate locations and are strong against heat, close to the switching elements 18a and 18b. The snubber current is a high frequency current exceeding several hundred kHz, and most of it passes through the ceramic capacitors 24a(1) and 24b(2), so the ceramic capacitors 24a(1) and 24b(2) are connected to the switching element 18a. , 18b, there is no particular problem even if the aluminum electrolytic capacitors 24a(1), 24b(1) are located a little apart.

The switching power supply device of the present invention is not limited to a DC input power supply device, but can also be applied to an AC input power supply device. In the case of an AC input power supply device, a rectifier circuit for rectifying the AC voltage output from the input power source may be provided, and the output end of the rectifier circuit may be connected to the input line 14 and the ground line 16. Thereby, the DC voltage output from the rectifier circuit can be regarded as the input voltage Vi.

10, 30, 32, 38, 38k, 46, 46k, 48, 48k, 52(1), 52(2) Switching power supply device 14 Input line 16 Ground line 18 First arm 18a, 18b, 34a, 34b Switching element 20 Transformer 20a Input winding 20b Output winding 22 Bias capacitor 24 Bypass capacitor circuit 24a, 24b Bypass capacitor 24a(1), 24b(1) Aluminum electrolytic capacitor (bypass capacitor)
24b(1), 24b(2) Ceramic capacitor (bypass capacitor)
26 Rectifying and smoothing circuit 34 Second arm 40 First snubber circuit 42 Current resonance capacitor 50 Second snubber circuit

Claims (7)

an input line and a ground line to which input voltage is supplied from the input power supply;
a first arm consisting of a series circuit of two switching elements connected between the input line and the ground line;
a transformer having an input winding and an output winding, one end of the input winding being connected to the midpoint of the first arm;
a bias capacitor connected between the other end of the input winding and the input line, or between the other end of the input winding and the ground line;
a circuit for suppressing the switching current flowing through the switching element from flowing out to the input power source side, the bypass comprising a series circuit of two bypass capacitors connected between the input line and the ground line; capacitor circuit,
a rectifying and smoothing circuit that rectifies and smoothes the voltage generated in the output winding to generate an output voltage;
a first snubber circuit connected between the midpoint of the bypass capacitor circuit and the midpoint of the first arm to reduce surge voltage generated across each switching element of the first arm;
A half-bridge switching power supply device, wherein the bypass capacitor is an aluminum electrolytic capacitor and a ceramic capacitor having a smaller capacity than the aluminum electrolytic capacitor connected in parallel . 2. The switching power supply device according to claim 1, wherein in each of the bypass capacitors of the bypass capacitor circuit, a midpoint of the aluminum electrolytic capacitor and a midpoint of the ceramic capacitor are separated . 3. The switching power supply device according to claim 1 , wherein the bias capacitor is also used as a current resonance capacitor. an input line and a ground line to which input voltage is supplied from the input power supply;
a first arm consisting of a series circuit of two switching elements connected between the input line and the ground line;
a transformer having an input winding and an output winding, one end of the input winding being connected to the midpoint of the first arm;
A circuit for suppressing the switching current flowing through the switching element from flowing out to the input power supply side, the circuit comprising a series circuit of two bypass capacitors connected between the input line and the ground line; a bypass capacitor circuit with the other end of the input winding connected to the midpoint;
a rectifying and smoothing circuit that rectifies and smoothes the voltage generated in the output winding to generate an output voltage;
a first snubber circuit connected between the midpoint of the bypass capacitor circuit and the midpoint of the first arm to reduce surge voltage generated across each switching element of the first arm;
A half-bridge switching power supply device, wherein the bypass capacitor is an aluminum electrolytic capacitor and a ceramic capacitor having a smaller capacity than the aluminum electrolytic capacitor connected in parallel . an input line and a ground line to which input voltage is supplied from the input power supply;
a first arm consisting of a series circuit of two switching elements connected between the input line and the ground line;
a second arm consisting of a series circuit of two switching elements connected between the input line and the ground line;
a transformer having an input winding and an output winding, the input winding being connected between a midpoint of the first arm and a midpoint of the second arm;
a circuit for suppressing the switching current flowing through the switching element from flowing out to the input power source side, the bypass comprising a series circuit of two bypass capacitors connected between the input line and the ground line; capacitor circuit,
a rectifying and smoothing circuit that rectifies and smoothes the voltage generated in the output winding to generate an output voltage;
a first snubber circuit connected between the midpoint of the bypass capacitor circuit and the midpoint of the first arm to reduce surge voltage generated across each switching element of the first arm;
a second snubber circuit connected between a midpoint of the bypass capacitor circuit and a midpoint of the second arm to reduce surge voltage generated across each switching element of the second arm; Full-bridge switching power supply. 6. The switching power supply device according to claim 5 , wherein the bypass capacitor is an aluminum electrolytic capacitor and a ceramic capacitor having a smaller capacity than the aluminum electrolytic capacitor connected in parallel. 7. The switching power supply device according to claim 4, further comprising a current resonance capacitor provided in series with the input winding .

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