JP7342760B2 - Switching power supply equipment and switching power supply system - Google Patents

Description

The present invention relates to a switching power supply device and a switching power supply system.

Patent Document 1 describes a circuit configuration including a resonant circuit, a transformer, and a rectifying and smoothing circuit (see FIG. 1 of Patent Document 1, etc.).
It is conceivable to configure a switching power supply device using such a circuit configuration. A switching power supply device includes, for example, an inverter, a resonant circuit, a transformer, and a rectifying and smoothing circuit.

Japanese Patent Application Publication No. 8-266057

However, in conventional switching power supply devices, the turn ratio between the primary coil and the secondary coil of the transformer is large, and the volume of the transformer may be large.

The present invention has been made in consideration of such circumstances, and provides a switching power supply device that can reduce the turns ratio between the primary coil and the secondary coil of a transformer, and a switching power supply equipped with such a switching power supply device. The challenge is to provide a system.

One aspect includes an inverter, a resonant circuit, a transformer, and a rectifying and smoothing circuit, and further includes at least one of between the resonant circuit and the transformer, or between the transformer and the rectifying and smoothing circuit. A switching power supply device comprising a filter, the filter including a coil and a capacitor, the filter being a low-pass filter, and the cut-off frequency of the low-pass filter being set to a higher value than the resonant frequency of the resonant circuit. It is.
One aspect includes an inverter, a resonant circuit, a transformer, and a rectifying and smoothing circuit, and further includes at least one of between the resonant circuit and the transformer, or between the transformer and the rectifying and smoothing circuit. A switching power supply device comprising a filter, the filter including a coil and a capacitor, the filter being a high-pass filter, and a cutoff frequency of the high-pass filter being set to a value lower than the resonant frequency of the resonant circuit. It is.
One aspect includes an inverter, a resonant circuit, a transformer, and a rectifying and smoothing circuit, and further includes at least one of between the resonant circuit and the transformer, or between the transformer and the rectifying and smoothing circuit. A filter is provided, the filter includes a coil and a capacitor, the filter is a bandstop filter, and the cutoff frequency of the bandstop filter is set to a value lower or higher than the resonant frequency of the resonant circuit. It is a switching power supply device.
One aspect includes an inverter, a resonant circuit, a transformer, and a rectifying and smoothing circuit, and further includes at least one of between the resonant circuit and the transformer, or between the transformer and the rectifying and smoothing circuit. A filter is provided, the filter includes a coil and a capacitor, the filter is a bandpass filter, and the cutoff frequency of the bandpass filter is set to a value lower or higher than a resonant frequency of the resonant circuit. It is a switching power supply device.

One aspect of the present invention is a switching power supply system that includes a switching power supply, an input power supply, and a load.

According to the present invention, in the switching power supply device, it is possible to reduce the turns ratio between the primary coil and the secondary coil of the transformer.

FIG. 1 is a diagram showing a schematic configuration of a switching power supply device according to a first embodiment. FIG. 2 is a diagram showing a schematic configuration of a switching power supply device according to a second embodiment. FIG. 1 is a diagram showing a circuit configuration of a low-pass filter (LPF) according to an embodiment. FIG. 1 is a diagram showing a circuit configuration of a high pass filter (HPF) according to an embodiment. FIG. 1 is a diagram showing a circuit configuration of a bandstop filter (BSF) according to an embodiment. FIG. 1 is a diagram showing a circuit configuration of a bandpass filter (BPF) according to an embodiment. 1 is a diagram showing a circuit configuration of a switching power supply device and a switching power supply system according to an embodiment. FIG. 1 is a diagram showing a simplified circuit configuration of a switching power supply device according to an embodiment. FIG. 3 is a diagram showing a circuit configuration according to a comparative example.

Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a diagram showing a schematic configuration of a switching power supply device 1 according to the first embodiment.
The switching power supply device 1 includes an inverter 11 , a resonant circuit 12 , an LC filter 13 , a transformer 14 , and a rectifying and smoothing circuit 15 . In the switching power supply device 1, an inverter 11, a resonant circuit 12, an LC filter 13, a transformer 14, and a rectifying and smoothing circuit 15 are connected in series.
Here, in the switching power supply device 1 according to the present embodiment, in a DC (Direct Current)-DC converter including an inverter 11, a resonant circuit 12, a transformer 14, and a rectifying and smoothing circuit 15, there is a connection between the resonant circuit 12 and the transformer 14. It has a configuration including an LC filter 13.

An example of the operation performed in the DC-DC converter of such a switching power supply device 1 will be shown.
For example, the inverter 11 is supplied with a DC voltage output from an input power source (not shown) that is a DC power source.
The inverter 11 has a switch section, receives the DC voltage, converts the DC voltage into an AC voltage, and outputs the AC voltage.
The resonance circuit 12 receives the AC voltage output from the inverter 11 and outputs the AC voltage to the LC filter 13 . Resonant circuit 12 has a predetermined resonant frequency.
The LC filter 13 receives the AC voltage output from the resonant circuit 12, performs predetermined filtering on the AC voltage, and outputs the filtered AC voltage.
The transformer 14 inputs the AC voltage output from the LC filter 13, performs conversion to step down the AC voltage, and outputs the converted AC voltage.
The rectifying and smoothing circuit 15 receives the AC voltage output from the transformer 14, rectifies and smoothes the AC voltage, converts it into a DC voltage, and outputs the DC voltage.
The DC voltage output from the rectifying and smoothing circuit 15 is supplied to, for example, a predetermined load (not shown).
In this manner, the DC-DC converter of the switching power supply device 1 converts the input DC voltage into a different DC voltage and outputs the DC voltage.

Here, an alternating current voltage is applied between the inverter 11 and the primary coil side of the transformer 14 and between the secondary coil side of the transformer 14 and the rectifying and smoothing circuit 15. LC filter 13 can attenuate alternating current voltage. The attenuation rate varies depending on the frequency depending on the frequency characteristics of the LC filter 13. As described above, since the amount of attenuation by the LC filter 13 varies depending on the frequency of the AC voltage, the LC filter 13 can pass or attenuate the AC voltage of a specific frequency.
In the switching power supply device 1 according to the present embodiment, such an LC filter 13 is provided between the resonant circuit 12 after the inverter 11 and the primary coil side of the transformer 14, so that an AC voltage of a predetermined frequency can be generated. can be attenuated.
Further, since the LC filter 13 is composed of an inductor and a capacitor, ideally no loss occurs in the LC filter 13.

There are roughly four types of LC filters 13. Specifically, the LC filter 13 is, for example, a low pass filter (LPF), a high pass filter (HPF), a band stop filter (BSF), or a band pass filter ( Band Pass Filter (BPF) is used.

The LPF is a filter that outputs low frequency components without attenuating them, but has frequency characteristics that attenuates high frequency components.
The HPF is a filter that outputs high frequency components without attenuating them, but has frequency characteristics that attenuates low frequency components.
BSF is a filter that outputs frequency components other than a specific frequency without attenuating it, but has a frequency characteristic that attenuates the specific frequency component.
A BPF is a filter that outputs a specific frequency component without attenuating it, but has a frequency characteristic that attenuates frequency components other than the specific frequency.

In the switching power supply device 1 according to the present embodiment, by including the LC filter 13, it is possible to reduce the turns ratio between the primary coil and the secondary coil in the transformer 14, for example. That is, in the switching power supply device 1 according to the present embodiment, by including the LC filter 13, the turns ratio between the primary coil and the secondary coil in the transformer 14 can be reduced compared to, for example, a case where the LC filter 13 is not provided. can do.

(Second embodiment)
FIG. 2 is a diagram showing a schematic configuration of a switching power supply device 101 according to the second embodiment.
The switching power supply device 101 includes an inverter 111, a resonant circuit 112, a transformer 113, an LC filter 114, and a rectifying and smoothing circuit 115. In the switching power supply device 101, an inverter 111, a resonant circuit 112, a transformer 113, an LC filter 114, and a rectifying and smoothing circuit 115 are connected in series.
Here, in the switching power supply device 101 according to the present embodiment, in a DC-DC converter including an inverter 111, a resonant circuit 112, a transformer 113, and a rectifying and smoothing circuit 115, an LC filter 114 is provided between the transformer 113 and the rectifying and smoothing circuit 115. It has a configuration comprising:

In the switching power supply device 101 according to the present embodiment, compared to the switching power supply device 1 according to the first embodiment, the position where the LC filter 114 is provided in the DC-DC converter is different, but the general operation is the same. be.

For example, the inverter 111 is supplied with a DC voltage output from an input power source (not shown) that is a DC power source.
The inverter 111 has a switch section, inputs the DC voltage, converts the DC voltage into an AC voltage, and outputs the AC voltage.
Resonant circuit 112 receives the AC voltage output from inverter 111 and outputs the AC voltage to transformer 113 . Resonant circuit 112 has a predetermined resonant frequency.
The transformer 113 receives the AC voltage output from the resonant circuit 112, performs step-down conversion of the AC voltage, and outputs the converted AC voltage.
The LC filter 114 receives the AC voltage output from the transformer 113, performs predetermined filtering on the AC voltage, and outputs the filtered AC voltage.
The rectifying and smoothing circuit 115 receives the AC voltage output from the LC filter 114, rectifies and smoothes the AC voltage, converts it into a DC voltage, and outputs the DC voltage.
The DC voltage output from the rectifying and smoothing circuit 115 is supplied to, for example, a predetermined load (not shown).
In this way, the DC-DC converter of the switching power supply device 101 converts the input DC voltage into a different DC voltage and outputs the DC voltage.

In the switching power supply device 101 according to the present embodiment, by providing such an LC filter 114 between the secondary coil side of the transformer 113 and the rectifying and smoothing circuit 115, the alternating current voltage can be attenuated.

In the switching power supply device 101 according to the present embodiment, by including the LC filter 114, the turn ratio between the primary coil and the secondary coil in the transformer 113 can be reduced, for example. That is, in the switching power supply device 101 according to the present embodiment, by including the LC filter 114, the turns ratio between the primary coil and the secondary coil in the transformer 113 can be reduced compared to, for example, a case where the LC filter 114 is not provided. can do.

<Example of specific circuit of LC filter>
A specific example of a circuit for an LC filter will be shown.

Examples of specific circuits of the LC filter will be shown with reference to FIGS. 3 to 6. Any of these circuits may be used, for example, as the LC filter 13 of the switching power supply 1 according to the first embodiment, or as the LC filter 114 of the switching power supply 101 according to the second embodiment. It's okay to be hit.

FIG. 3 is a diagram showing a circuit configuration of a low pass filter (LPF) 210 according to one embodiment.
The LPF 210 includes a coil 211 and a capacitor 212. Note that the coil 211 may be any type having inductance, and the capacitor 212 may be any type having capacitance.
A coil 211 is provided on one of the two-wire transmission lines D1 and D2, and a capacitor 212 is connected between the two transmission lines D1 and D2 at a stage subsequent to the coil 211.
For example, in the example of FIG. 3, the resonant circuit 12 in the first embodiment or the transformer 113 in the second embodiment is arranged on the side of the coil 211 (the left side in the example of FIG. 3), and the side of the capacitor 212 (the left side in the example of FIG. In the example, the transformer 14 in the first embodiment or the rectifying and smoothing circuit 115 in the second embodiment is arranged on the right side).

Here, the LPF 210 can suppress harmonics. For example, if the cutoff frequency of the LPF 210 is set below the resonant frequency of the resonant circuit and the gain at the oscillation frequency is attenuated in the attenuation region, the amount of attenuation may become too large. If the cutoff frequency of the LPF 210 is set to be higher than the resonant frequency of the resonant circuit so that the oscillation frequency is included in the passband, the gain at the oscillation frequency can be attenuated. Therefore, for example, the cutoff frequency of the LPF 210 is set to a value higher than the resonant frequency of the resonant circuit (for example, the resonant circuit 12 in the first embodiment or the resonant circuit 112 in the second embodiment).

FIG. 4 is a diagram showing a circuit configuration of a high pass filter (HPF) 230 according to one embodiment.
The HPF 230 includes a coil 231 and a capacitor 232. Note that the coil 231 may be any type of inductance, and the capacitor 232 may be any type of capacitance.
A capacitor 232 is provided on one transmission line D11 of the two-wire transmission lines D11 and D12, and a coil 231 is connected between the two transmission lines D11 and D12 at a stage before the capacitor 232.
For example, in the example of FIG. 4, the resonant circuit 12 in the first embodiment or the transformer 113 in the second embodiment is arranged on the side of the coil 231 (the left side in the example of FIG. 4), and the side of the capacitor 232 (the left side in the example of FIG. 4). In the example, the transformer 14 in the first embodiment or the rectifying and smoothing circuit 115 in the second embodiment is arranged on the right side).

Here, the HPF 230 cannot suppress harmonics. For example, if the cutoff frequency of the HPF 230 is set to be higher than the resonant frequency of the resonant circuit and the gain at the oscillation frequency is attenuated in the attenuation region, the amount of attenuation may become too large. By setting the cutoff frequency of the HPF 230 below the resonant frequency of the resonant circuit so that the passband includes the oscillation frequency, the gain at the oscillation frequency can be attenuated. Therefore, for example, the cutoff frequency of the HPF 230 is set to a value lower than the resonant frequency of the resonant circuit (for example, the resonant circuit 12 in the first embodiment or the resonant circuit 112 in the second embodiment).

FIG. 5 is a diagram illustrating a circuit configuration of a bandstop filter (BSF) 250 according to one embodiment.
BSF 250 includes a coil 251 and a capacitor 252. Note that the coil 251 may be any type having inductance, and the capacitor 252 may be any type having capacitance.
A coil 251 and a capacitor 252 are connected in series between the two transmission lines D21 and D22.
For example, in the example of FIG. 5, the resonant circuit 12 in the first embodiment or the transformer 113 in the second embodiment is located on one side (the left side in the example of FIG. 5) with respect to the part where the coil 251 and the capacitor 252 are present. The transformer 14 in the first embodiment or the rectifying and smoothing circuit 115 in the second embodiment is arranged on the other side (right side in the example of FIG. 5).

Here, the BSF 250 cannot suppress harmonics. For example, the resonant frequency of the BSF 250 may be set to a lower value or higher than the resonant frequency of the resonant circuit (for example, the resonant circuit 12 in the first embodiment or the resonant circuit 112 in the second embodiment). May be set.

FIG. 6 is a diagram showing a circuit configuration of a bandpass filter (BPF) 270 according to one embodiment.
BPF 270 includes a coil 271 and a capacitor 272. Note that the coil 271 may be any type having inductance, and the capacitor 272 may be any type having capacitance.
A coil 271 and a capacitor 272 are connected in series to one of the two-wire transmission paths D31 and D32.
For example, in the example of FIG. 6, the resonant circuit 12 in the first embodiment or the transformer 113 in the second embodiment is located on one side (the left side in the example of FIG. 6) with respect to the part where the coil 271 and the capacitor 272 are present. The transformer 14 in the first embodiment or the rectifying and smoothing circuit 115 in the second embodiment is arranged on the other side (right side in the example of FIG. 6).

Here, the BPF 270 can suppress harmonics. For example, harmonics can be suppressed by setting the resonant frequency of the BPF 270 to a value lower than the resonant frequency of the resonant circuit. For example, the resonant frequency of the BPF 270 may be set to a lower value or higher than the resonant frequency of the resonant circuit (for example, the resonant circuit 12 in the first embodiment or the resonant circuit 112 in the second embodiment). May be set.

<Example of specific circuit of switching power supply>
A specific example of a circuit for a switching power supply device will be shown.

A specific example of a circuit of a switching power supply device will be shown with reference to FIGS. 7 to 8 according to the embodiment and FIG. 9 according to a comparative example.
The examples in FIGS. 7 to 8 and 9 show a case where an LC filter is provided between the resonant circuit and the transformer like the switching power supply device 1 according to the first embodiment.
Note that even in the case where an LC filter is provided between the transformer and the rectifying and smoothing circuit as in the switching power supply device 101 according to the second embodiment, the respective circuits may be similar to the examples shown in FIGS. 7 and 8, for example. A circuit may also be used.

FIG. 7 is a diagram showing a circuit configuration of a switching power supply device 301 and a switching power supply system 401 according to an embodiment.
The switching power supply device 301 includes a capacitor 412, an inverter 311, a resonant circuit 312, an LC filter 313, a transformer 314, and a rectifying and smoothing circuit 315.

Note that a switching power supply system 401 is configured by including the switching power supply device 301 of this embodiment, an input power supply 411 which is a DC power supply, and a load 571.

The inverter 311 includes a field effect transistor (FET) 431 and an FET 432. FET431 and FET432 are bipolar transistors, IGBTs (Insulated Gate Bipolar Transistors), GaN transistors (Gallium Nitride Transistors), or SiC transistors (Silicon Carbide Trastors). nsistor) may also be used.
Further, in this embodiment, the inverter 311, the resonant circuit 312, the transformer 314, and the rectifying and smoothing circuit 315, which are the main parts of the switching power supply device 301, are described in the basic configuration of a current resonant converter, but they are limited to this configuration. It's not a thing.
The resonant circuit 312 includes a coil 451 and a capacitor 452.
LC filter 313 includes a coil 471 and a capacitor 472. As described above, in this embodiment, a case is shown where an LPF is used as the LC filter 313, but other filters may be used, such as an HPF, BSF, or BPF, for example.
The transformer 314 includes a magnetic core 511, a primary coil 512, and a secondary coil 513.
The rectifying and smoothing circuit 315 includes a rectifying diode 531, a diode 532, and a smoothing capacitor 551.
For example, the rectifying diode may have a synchronous rectification configuration using a switch element such as an FET.

The connection relationship of circuit elements in switching power supply system 401 will be explained.
Of the two output terminals that the input power supply 411 has, the output terminal on the positive (+) side is connected to one transmission path D111, and the output terminal on the negative (-) side is connected to the other transmission path D112. It is connected.
Here, the transmission path D112 is connected to the reference potential section G1. In this embodiment, the reference potential portion G1 is a portion that becomes a reference potential (reference potential). In this embodiment, the reference potential is a potential corresponding to ground, and the reference potential portion G1 is a ground point. Note that a potential other than ground may be used as the reference potential.

A capacitor 412 is connected in parallel with the input power source 411 between the two transmission lines D111 and D112.
After the capacitor 412, an FET 431 and a FET 432 are connected in series between the two transmission lines D111 and D112. Specifically, the transmission line D111 and the drain (D) terminal of FET431 are connected, the transmission line D112 and the source (S) terminal of FET432 are connected, and the source terminal of FET431 and the drain terminal of FET432 are connected. are connected. Note that the gate (G) terminal of the FET 431 and the gate terminal of the FET 432 are each controlled by a predetermined control section (not shown). These FETs 431 and 432 are used as a switch section.

A point between the source terminal of FET 431 and the drain terminal of FET 432 is connected to one of the two terminals of coil 451.
The other terminal of the two terminals of the coil 451 and one terminal of the two terminals of the coil 471 are connected.
A capacitor 452 is connected between a point between the coils 451 and 471 and the transmission line D112.
A capacitor 472 is connected between the other terminal of the two terminals of the coil 471 and the transmission path D112.

At the subsequent stage of the capacitor 472, the primary coil 512 of the transformer 314 is connected between the other terminal of the two terminals of the coil 471 and the transmission path D112.
A diode 532 is connected between both ends of the secondary coil 513 of the transformer 314.
The anode terminal of the diode 531 is connected to a connection point between one end of the secondary coil 513 of the transformer 314 and the cathode terminal of the diode 532. A capacitor 551 is connected between the cathode terminal of diode 531 and the anode terminal of diode 532.
A load 571 is connected between the cathode terminal of the diode 531 and the anode terminal of the diode 532 after the capacitor 551 .
The anode terminal of the diode 532 is connected to the reference potential section G2. In this embodiment, the reference potential section G2 is similar to the reference potential section G1, and has the same potential as the reference potential section G1.
Thus, the switching power supply device 301 shown in FIG. 7 has a resonant converter including an LPF.

FIG. 8 is a diagram showing a simplified circuit configuration of a switching power supply device 301 according to an embodiment.
In the circuit configuration shown in FIG. 8, compared to the circuit configuration shown in FIG. Also, the subsequent circuit is replaced with a virtual load 631. The load 631 is a load on the secondary side converted into a load on the primary side.

Here, for convenience of explanation, the voltage generated by the AC power supply 611 is expressed as Vi, and the voltage applied to the load 631 is expressed as Vo. Further, the resistance of the load 571 is represented by R, and the resistance of the load 631 is represented by R'. Further, the inductance of the coil 451 is represented by Lr, and the capacitance of the capacitor 452 is represented by Cr. Further, the inductance of the coil 471 is expressed as Llpf, and the capacitance of the capacitor 472 is expressed as Clpf.
Also, the angular frequency is expressed as ω. ω is expressed as ω=2πf. Here, f is the frequency of the waveform input to the resonant circuit 312. In this case, f is considered to be the frequency of the waveform output from the inverter 311, that is, the switching frequency.
Further, it is assumed that the ratio between the number of turns of the primary coil 512 and the number of turns of the secondary coil 513 of the transformer 314 is N:1. At this time, it is expressed as R'=R/ ^N2 .
j represents an imaginary unit.

In this case, the transfer function (Vo/Vi) is expressed by equation (1).
Further, the gain Gvlpf at this time is expressed by equation (2).

[Number 1]
Vo/Vi=jR/(α+β)
α=ω ³・Lr・Llpf・Cr−ωLr−ωLlpf
β=-jR・γ
γ=ω ²・Lr・Cr+ω ²・Lr・Clpf+ω ²・Llpf・Clpf−ω ⁴・Lr・Llpf・Cr・Clpf−1
...(1)

[Number 2]
Gvlpf=20・log | Vo/Vi | ... (2)

Here, the circuit configuration according to the embodiment shown in FIGS. 7 to 8 will be compared with the circuit configuration according to the comparative example shown in FIG. 9.
FIG. 9 is a diagram showing a circuit configuration according to a comparative example.
In the circuit configuration shown in FIG. 9, compared to the circuit configuration shown in FIG. 8, the coil 471 and capacitor 472 that constitute the LPF are removed between the AC power source 611 and the load 631, and a resonant circuit is configured. A coil 451 and a capacitor 452 are provided.
Note that, for convenience of explanation, the same reference numerals as in the circuit configuration shown in FIG. 8 are given to the circuit configuration shown in FIG. 9 as well.

Here, for convenience of explanation, in the example of FIG. 9, the voltage generated by the AC power supply 611 is represented by Vri, and the voltage applied to the load 631 is represented by Vro.

In this case, the transfer function (Vro/Vri) is expressed by equation (3).
Further, the gain Gvr at this time is expressed by equation (4).

[Number 3]
Vro/Vri=jR/(δ+η)
δ=-ω・Lr
η=-jR(ω ²・Lr・Cr-1)
...(3)

[Number 4]
Gvr=20・log｜Vro/Vri｜...(4)

For example, when the difference between the gain Gvlpf in the circuit configuration shown in FIG. 8 and the gain Gvr in the circuit configuration shown in FIG. 9 becomes -6 dB at the switching frequency, the output voltage has been halved. In this case, in the switching power supply device 301 according to this embodiment, the number of turns N of the primary coil 512 of the transformer 314 can be halved compared to the circuit configuration shown in FIG.

<LC filter cutoff frequency>
Next, explanation will be given from the viewpoint of the cutoff frequency of the LC filter 313.
Considering the cutoff frequency of the LC filter 313, voltage attenuation may increase or decrease due to the influence of the resonant circuit of the resonant converter. Therefore, when the switching frequency is used, consider the difference between the voltage gain Gv when the LC filter 313 is not provided and the voltage gain Gvlc when the LC filter 313 is provided. Assuming that the number of primary turns is reduced to at least 1/2 the number of primary turns, the difference in voltage gain will be -6 dB or less. Assuming that the number of primary turns is reduced to 1/10 at most, the difference in voltage gain will be -20 dB or more.
In this case, the numerical limitation is expressed by equation (5).

[Number 5]
-6dB≧Gvlc-Gv≧-20dB...(5)

When determining Llpf (inductance) and Clpf (capacitance), which are parameters that determine the characteristics of the LC filter 313, first, for example, the voltage gain Gv in the case where the LC filter 313 is not provided is determined. Next, determine the amount of voltage attenuation required at the desired frequency (switching frequency). For example, when the output voltage is halved, by subtracting 6 dB from the voltage gain Gv, the desired voltage gain Gvlc when the LC filter 313 is provided becomes (Gv-6). With the desired voltage gain Gvlc determined, the parameters Llpf and Clpf of the LC filter 313 are determined from the desired frequency (switching frequency).
Note that although the case where an LPF is used as the LC filter 313 has been described here, the same applies to the case where another filter is used such as an HPF, BSF, or BPF.

<Configuration example>
As one configuration example, a switching power supply device includes an inverter, a resonant circuit, a transformer, and a rectifying and smoothing circuit.
Further, as an example, the switching power supply device includes a filter between the resonant circuit and the transformer (the example in FIG. 1).
Furthermore, as another example, the switching power supply device includes a filter between the transformer and the rectifying and smoothing circuit (the example in FIG. 2).
Note that, as another example, the switching power supply device may include a filter between the resonant circuit and the transformer, and may also include a filter (another filter) between the transformer and the rectifying and smoothing circuit.

As one configuration example, in a switching power supply device, the filter includes a coil and a capacitor (examples in FIGS. 3 to 6).
As one configuration example, in a switching power supply, the filter is a low-pass filter. Then, the cutoff frequency of the low-pass filter is set to a value higher than the resonant frequency of the resonant circuit (example in FIG. 3).
As one configuration example, in a switching power supply, the filter is a high-pass filter. Then, the cutoff frequency of the high-pass filter is set to a value lower than the resonant frequency of the resonant circuit (example in FIG. 4).
As one configuration example, in a switching power supply, the filter is a bandstop filter. Then, the cutoff frequency of the bandstop filter is set to a value lower or higher than the resonant frequency of the resonant circuit (example in FIG. 5).
As one configuration example, in a switching power supply, the filter is a bandpass filter. Then, the cutoff frequency of the bandpass filter is set to a value lower or higher than the resonant frequency of the resonant circuit (example in FIG. 6).
One configuration example is a switching power supply system including the above-described switching power supply, an input power supply, and a load.

Although the embodiments of the present invention have been described above in detail with reference to the drawings, the specific configuration is not limited to these embodiments, and may include design changes within the scope of the gist of the present invention.

1, 101, 301... Switching power supply device, 11, 111, 311... Inverter, 12, 112, 312... Resonance circuit, 13, 114, 313... LC filter, 14, 113, 314... Transformer, 15, 115, 315... Rectifier smoothing circuit, 210...Low pass filter, 211, 231, 251, 271, 451, 471...Coil, 212, 232, 252, 272, 412, 452, 472, 551...Capacitor, 230...High pass filter, 250...Band stop Filter, 270...Band pass filter, 401...Switching power supply system, 411...Input power supply, 431-432...FET, 511...Magnetic core, 512...Primary coil, 513...Secondary coil, 531-532...Diode, 571, 631... Load, 611...AC power supply, D1-D2, D11-D12, D21-D22, D31-D32, D111-D112...Transmission line, G1-G2...Reference potential section

Claims (5)

Inverter and
a resonant circuit;
transformer and
Equipped with a rectifier and smoothing circuit,
Further, a filter is provided between the resonant circuit and the transformer, or between the transformer and the rectifying and smoothing circuit ,
The filter includes a coil and a capacitor,
The filter is a low-pass filter,
The cutoff frequency of the low-pass filter is set to a higher value than the resonant frequency of the resonant circuit.
Switching power supply. Inverter and
a resonant circuit;
transformer and
Equipped with a rectifier and smoothing circuit,
Further, a filter is provided between the resonant circuit and the transformer, or between the transformer and the rectifying and smoothing circuit ,
The filter includes a coil and a capacitor,
The filter is a high pass filter,
The cutoff frequency of the high-pass filter is set to a value lower than the resonant frequency of the resonant circuit.
Switching power supply. Inverter and
a resonant circuit;
transformer and
Equipped with a rectifier and smoothing circuit,
Further, a filter is provided between the resonant circuit and the transformer, or between the transformer and the rectifying and smoothing circuit ,
The filter includes a coil and a capacitor,
The filter is a bandstop filter,
The cutoff frequency of the bandstop filter is set to a value lower or higher than the resonant frequency of the resonant circuit.
Switching power supply. Inverter and
a resonant circuit;
transformer and
Equipped with a rectifier and smoothing circuit,
Further, a filter is provided between the resonant circuit and the transformer, or between the transformer and the rectifying and smoothing circuit ,
The filter includes a coil and a capacitor,
The filter is a bandpass filter,
The cutoff frequency of the bandpass filter is set to a value lower or higher than the resonant frequency of the resonant circuit.
Switching power supply. A switching power supply device according to any one of claims 1 to 4 ,
input power and
comprising a load;
Switching power supply system.

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