Switching Power Supply Unit

Abstract

A switching power supply device (101) comprises an inverter circuit (10) and a noise reduction circuit. The noise reduction circuit comprises: a first half bridge capacitor circuit (21) connected between DC input lines (DCin); a second half bridge capacitor circuit (22) connected between AC output lines (ACout); a first common mode choke coil (31) connected between the first half bridge capacitor circuit (21) and the second half bridge capacitor circuit (22); and an electric path (1) for electrically connecting between a midpoint of the first half bridge capacitor circuit (21) and a midpoint of the second half bridge capacitor circuit (22).

Description

[Technical field]

[0001] The present invention relates to a switching power supply device including an inverter circuit and a noise reduction circuit. [Background technology]

[0002] An inverter circuit is a circuit that converts DC input power from a DC input line into AC power using a switching circuit and outputs the AC power to an AC output line, and the potential of the DC input line is essentially floating with respect to the ground potential. Therefore, electromagnetic noise caused by switching operation is superimposed on the DC potential portion. This generates common mode noise, which causes EMI (electromagnetic interference). Therefore, a switching power supply device equipped with an inverter circuit generally has a noise reduction circuit to suppress EMI. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-208596 A Summary of the Invention [Problem to be solved by the invention]

[0004] For example, Patent Document 1 discloses a power transmission device equipped with an EMI countermeasure circuit together with an inverter circuit. The first Y capacitor of the EMI countermeasure circuit of this power transmission device is not connected to ground, but to the power line between the AC line and the inverter circuit. The wiring connected to the power line is not connected to ground, and the impedance increases as the wiring becomes longer. If a detection signal line for voltage or current is located close to a wiring with high impedance, the signal line receives noise from the wiring with high impedance, and the voltage or current cannot be detected accurately. Therefore, measures such as changing the design of the inverter circuit are required, which causes an extension of the design period.

[0005] However, noise countermeasures for switching power supplies are generally implemented after the design of the inverter circuit is completed. When the EMI countermeasure circuit is adjusted to counter noise, the adjustment may affect the operation of the feedback control circuit of the inverter circuit, causing the inverter circuit to malfunction or requiring the inverter circuit to be redesigned to suppress the malfunction. This may result in new problems such as longer design time. In addition, measures such as adding a large EMI countermeasure circuit may be required, which may lead to problems such as an increase in the size of the switching power supply.

[0006] In addition, to reduce EMI, it is necessary to increase the capacitance of the Y capacitor, but increasing the capacitance of the Y capacitor can adversely affect the feedback control of the inverter, causing problems such as malfunction of the power conversion operation. Also, increasing the capacitance of the Y capacitor connected to ground increases leakage current, raising the risk of electric shock.

[0007] As described above, in switching power supply devices equipped with inverter circuits, there is a demand to simultaneously achieve EMI suppression, power integrity (ensuring power supply quality), and shortening the design period for the switching power supply device.

[0008] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to suppress the effect of common mode noise on feedback control in a switching power supply device including an inverter circuit and a feedback control circuit. [Means for solving the problem]

[0009] As an example of a switching power supply device according to the present disclosure, An inverter circuit and a noise reduction circuit are provided, The inverter circuit includes: A DC input line; an AC output line; An inductor; a switching circuit for causing a switching current to flow through the inductor; an input capacitor connected in parallel between the DC input lines; an output capacitor connected in parallel between the AC output lines; a DC input voltage detection circuit for detecting a voltage between the DC input lines; an AC output voltage detection circuit for detecting a voltage between the AC output lines; an AC output current detection circuit for detecting a current in the AC output line; a feedback control circuit for controlling the switching circuit so that an AC output voltage or an AC output current of the AC output line becomes a predetermined value based on the DC input voltage, the feedback control circuit having a reference potential connected to a reference potential line of the DC input line; Equipped with The noise reduction circuit includes: a first half-bridge capacitor circuit connected between the DC input lines; a second half-bridge capacitor circuit connected between the AC output lines; a first common mode choke coil connected between the first half-bridge capacitor circuit and the second half-bridge capacitor circuit; An electrical path is provided that electrically connects the midpoint of the first half-bridge capacitor circuit and the midpoint of the second half-bridge capacitor circuit to form a noise balancing circuit that balances common-mode noise of a potential different from ground.

[0010] With this configuration, the noise balancing circuit is characterized by suppressing the influence of common mode noise on the feedback control circuit. Effect of the Invention

[0011] According to the present invention, in a switching power supply device including an inverter circuit and a feedback control circuit, the influence of common mode noise on feedback control can be suppressed. [Brief description of the drawings]

[0012] [Figure 1]FIG. 1 is a circuit diagram of a switching power supply device 101 according to the first embodiment. [Diagram 2] FIG. 2 is a circuit diagram of switching power supply devices 102A and 102B according to the second embodiment. [Diagram 3] FIG. 3 is a circuit diagram of still other switching power supply devices 102C, 102D, and 102E according to the second embodiment. [Figure 4] FIG. 4 is a circuit diagram of a switching power supply device 103 according to the third embodiment. [Diagram 5] FIG. 5 is a circuit diagram of a switching power supply device 104 according to the fourth embodiment. [Figure 6] FIG. 6 is a circuit diagram of a switching power supply device 105 according to the fifth embodiment. [Figure 7] FIG. 7 is a circuit diagram of a switching power supply device 106 according to the sixth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, several specific examples will be given with reference to the drawings to show several embodiments for carrying out the present invention. In each drawing, the same reference numerals are given to the same parts. In consideration of the ease of explanation or understanding of the main points, the embodiments are shown divided into several embodiments for convenience of explanation, but partial replacement or combination of the configurations shown in different embodiments is possible. In the second and subsequent embodiments, the description of matters common to the first embodiment will be omitted, and only the differences will be described. In particular, similar actions and effects due to similar configurations will not be mentioned in each embodiment.

[0014] First Embodiment 1 is a circuit diagram of a switching power supply device 101 according to a first embodiment. This switching power supply device 101 is connected between a DC power supply Vin and a load circuit RL. A commercial power system may be connected in parallel to the load circuit RL. This switching power supply device 101 also includes an inverter circuit 10 and a noise reduction circuit.

[0015] The inverter circuit 10 includes a DC input line DCin, an AC output line ACout, inductors L1 and L2, a switching circuit 12 that passes a switching current through the inductors L1 and L2, an input capacitor Ci connected in parallel between the DC input lines DCin, an output capacitor Co connected in parallel between the AC output lines ACout, a DC input voltage detection circuit 13 that detects the voltage across the DC input lines DCin, an AC output voltage detection circuit 15 that detects the voltage across the AC output lines ACout, an AC output current detection circuit 16 that detects the current of the AC output line ACout, and a feedback control circuit 14. The feedback control circuit 14 is configured of an analog circuit or a digital circuit such as an MCU (Micro Controller Unit) or a DSP (Digital Signal processor).

[0016] The feedback control circuit 14 has its reference potential connected to the reference potential line of the DC input line DCin, and controls the switching circuit 12 so that the AC output voltage or AC output current of the AC output line ACout becomes a predetermined value based on the DC input voltage.

[0017] The noise reduction circuit includes a first half-bridge capacitor circuit 21 connected between the DC input lines DCin, a second half-bridge capacitor circuit 22 connected between the AC output lines ACout, a first common mode choke coil 31 connected between the first half-bridge capacitor circuit 21 and the second half-bridge capacitor circuit 22, and an electrical path 1 electrically connecting a midpoint of the first half-bridge capacitor circuit 21 and a midpoint of the second half-bridge capacitor circuit 22. The first common mode choke coil 31 is composed of coils L11 and L12 magnetically coupled to each other. The first half-bridge capacitor circuit 21, the second half-bridge capacitor circuit 22, and the electrical path 1 constitute a noise balancing circuit that balances common mode noises of a potential different from that of the ground. In other words, the noise reduction circuit includes the noise balancing circuit and the first common mode choke coil 31.

[0018] The noise balancing circuit suppresses the influence of common mode noise on the feedback control circuit 14. The midpoint of the first half-bridge capacitor circuit 21 is at the midpoint of the DC input line DCin, and the midpoint of the second half-bridge capacitor circuit 22 is at the midpoint of the AC output line ACout. Both midpoints are commonly connected through the electrical path 1, so that the current of the common mode noise components generated in the switching circuit 12 flows between the input DC line and the output AC line through the electrical path 1. The common mode noise has a relatively high frequency and is not in phase. Therefore, these common mode noises flow through the electrical path 1 and cancel each other out. This balances the common mode noises at a potential different from that of the ground.

[0019] It is preferable that the electric path 1 is made of a metal plate. This reduces the voltage drop in the electric path 1, and reduces the potential difference between the midpoint of the first half-bridge capacitor circuit 21 and the midpoint of the second half-bridge capacitor circuit 22. This makes it possible to more effectively balance the common-mode noise.

[0020] In addition, the first common mode choke coil 31 is connected between the first half-bridge capacitor circuit 21 and the second half-bridge capacitor circuit 22. The first common mode choke coil 31 reduces the current of the common mode noise component generated in the switching circuit 12, and suppresses the influence of the common mode noise on the feedback control circuit 14.

[0021] To counter EMI, it is necessary to optimize the capacitances of the capacitors C11, C12, C21, and C22. Conventionally, adjusting (changing) the capacitance of the capacitors would affect the feedback control circuit 14. In this case, the feedback control circuit 14 would need to be redesigned, which would extend the design period. According to this embodiment, the current of the common mode noise component generated in the switching circuit 12 flows between the input DC line and the output AC line through the electrical path 1 in a reduced amount, so that the effect on the feedback control circuit 14 is small.

[0022] In this way, a small, low-cost switching power supply device can be obtained that can shorten the design period and ensure safety. That is, in a configuration including an inverter circuit and a feedback control circuit, switching power supply device 101 can suppress the influence of common-mode noise on feedback control while also achieving the following effects. Switching power supply device 101 can shorten the design period when adjusting (optimizing) the capacitance of the capacitor that constitutes the EMI countermeasure circuit, and can achieve power conversion operation without increasing leakage current to ensure safety. Furthermore, switching power supply device 101 can achieve a small, low-cost configuration.

[0023] Second Embodiment In the second embodiment, a switching power supply device in which an impedance element is connected to an electric path 1 will be illustrated.

[0024] 2 is a circuit diagram of switching power supply devices 102A and 102B according to the second embodiment. These switching power supply devices 102A and 102B include an inverter circuit 10, a first half-bridge capacitor circuit 21, a second half-bridge capacitor circuit 22, and a first common mode choke coil 31. Also, they include an electrical path 1 that electrically connects the midpoint of the first half-bridge capacitor circuit 21 and the midpoint of the second half-bridge capacitor circuit 22.

[0025] An impedance element Z1 is connected in series to the electric path 1 of the switching power supply device 102A. This impedance element Z1 has at least an inductance component or a resistance component.

[0026] An impedance element Z2 is connected between the electrical path 1 of the switching power supply device 102B and the ground. This impedance element Z2 has at least a capacitance component, an inductance component, or a resistance component. This "ground" is an earth or a frame ground.

[0027] By connecting the impedance element Z1 in series to the electrical path 1 as in the switching power supply device 102A, even if the effect of suppressing common mode noise by the first common mode choke coil 31 is insufficient, the impedance element Z1 compensates for the suppression of common mode noise. In other words, the impedance element Z1 attenuates the oscillation of the high-frequency common mode current flowing through the electrical path 1, thereby suppressing the common mode noise.

[0028] In the switching power supply device 102B, an impedance element Z2 is connected between the electrical path 1 and the ground. This impedance element Z2 has at least a capacitance component, an inductance component, or a resistance component.

[0029] In this way, by connecting the impedance element Z2 between the electrical path 1 and ground, even if the effect of suppressing common mode noise by the first common mode choke coil 31 is insufficient, the impedance element Z2 compensates for the suppression of common mode noise. In other words, the common mode current that flows to balance the first half-bridge capacitor circuit 21 and the second half-bridge capacitor circuit 22 through the electrical path 1 flows to the ground through the impedance element Z2. This current (leakage current) is smaller than the current that leaks from the line bypass capacitor circuit to the ground when a line bypass capacitor circuit is provided. Therefore, it is possible to suppress common mode noise while reducing the leakage current.

[0030] 3 is a circuit diagram of still other switching power supply devices 102C, 102D, and 102E according to the second embodiment. In these switching power supply devices 102C, 102D, and 102E, an impedance element Z2 is connected between the electrical path 1 and ground.

[0031] In the switching power supply device 102C, the impedance element Z1 is connected in series between the connection point of the impedance element Z2 to the electrical path 1 and the midpoint of the second half-bridge capacitor circuit 22. In the switching power supply device 102D, the impedance element Z3 is connected in series between the connection point of the impedance element Z2 to the electrical path 1 and the midpoint of the first half-bridge capacitor circuit 21. In the switching power supply device 102E, the impedance element Z1 is connected in series between the connection point of the impedance element Z2 to the electrical path 1 and the midpoint of the second half-bridge capacitor circuit 22, and the impedance element Z3 is connected in series between the connection point of the impedance element Z2 to the electrical path 1 and the midpoint of the first half-bridge capacitor circuit 21.

[0032] 3, if the impedance elements Z1 and Z3 are resistors or inductors and the impedance element Z2 is a capacitor, a low-pass filter is formed by these impedance elements. Also, if the impedance elements Z1 and Z3 are capacitors and the impedance element Z2 is a resistor or an inductor, a high-pass filter is formed by these impedance elements.

[0033] In this way, by connecting a frequency filter to the electrical path 1, it is possible to appropriately determine the responsiveness of the feedback to the common mode voltage of the DC input line DCin with respect to the fluctuation of the common mode voltage output to the AC output line ACout.

[0034] Third embodiment In the third embodiment, a switching power supply device 103 including a second common mode choke coil 32 will be illustrated.

[0035] Fig. 4 is a circuit diagram of a switching power supply device 103 according to a third embodiment. This switching power supply device 103 is connected between a DC power supply Vin and a load circuit RL. This switching power supply device 103 also includes an inverter circuit 10 and a noise reduction circuit. In Fig. 4, the circuits other than the inverter circuit 10 constitute the noise reduction circuit.

[0036] A switching power supply device 103 according to the third embodiment includes a second common mode choke coil 32 connected to the load side of the second half-bridge capacitor circuit 22. The other configuration is similar to that of the switching power supply device 101 shown in FIG.

[0037] The second common mode choke coil 32 is composed of coils L21 and L22 that are magnetically coupled to each other. The second common mode choke coil 32 suppresses common mode noise superimposed on the AC output line ACout of the inverter circuit 10.

[0038] Fourth embodiment In the fourth embodiment, a switching power supply device in which a filter capacitor is connected to an AC output line will be illustrated.

[0039] Fig. 5 is a circuit diagram of a switching power supply device 104 according to a fourth embodiment. This switching power supply device 104 is connected between a DC power supply Vin and a load circuit RL. This switching power supply device 104 also includes an inverter circuit 10 and a noise reduction circuit. In Fig. 5, the circuits other than the inverter circuit 10 constitute the noise reduction circuit.

[0040] The switching power supply device 104 according to the fourth embodiment includes two capacitors C31 and C32 connected in series, and this circuit is connected between the AC output lines ACout, with the midpoint connected to ground. The rest of the configuration is the same as that of the switching power supply device 103 shown in FIG.

[0041] The circuit including the capacitors C31 and C32 suppresses common mode noise superimposed on the AC output line ACout of the inverter circuit 10.

[0042] Fifth embodiment In the fifth embodiment, a switching power supply device including a capacitor C4 connected between the reference potential of the feedback control circuit 14 and the electrical path 1 will be illustrated.

[0043] Fig. 6 is a circuit diagram of a switching power supply device 105 according to a fifth embodiment. This switching power supply device 105 is connected between a DC power supply Vin and a load circuit RL. This switching power supply device 105 also includes an inverter circuit 10 and a noise reduction circuit. In Fig. 6, the circuits other than the inverter circuit 10 constitute the noise reduction circuit.

[0044] A switching power supply device 105 according to the fifth embodiment includes a capacitor C4 connected between the reference potential of the feedback control circuit 14 and the electrical path 1. The other configuration is similar to that of the switching power supply device 104 shown in FIG.

[0045] By connecting the capacitor C4 between the reference potential of the feedback control circuit 14 and the electrical path 1, the potential of the electrical path 1 is stabilized, and the influence of the electrical path on the voltage and current detection signal lines can be reduced while suppressing common mode noise.

[0046] Sixth Embodiment In the sixth embodiment, a switching power supply device including a capacitor C5 connected between the reference potential of the feedback control circuit 14 and the ground will be illustrated.

[0047] Fig. 7 is a circuit diagram of a switching power supply device 106 according to a sixth embodiment. This switching power supply device 106 is connected between a DC power supply Vin and a load circuit RL. This switching power supply device 106 also includes an inverter circuit 10 and a noise reduction circuit. In Fig. 7, the circuits other than the inverter circuit 10 constitute the noise reduction circuit.

[0048] A switching power supply device 106 according to the sixth embodiment includes a capacitor C5 connected between the reference potential of the feedback control circuit 14 and ground. The other configuration is similar to that of the switching power supply device 104 shown in FIG.

[0049] By connecting the capacitor C5 between the reference potential of the feedback control circuit 14 and ground, the potential of the electrical path 1 is stabilized, and the influence of the electrical path 1 on the detection signal lines of voltage and current can be reduced while suppressing common mode noise.

[0050] Finally, the present invention is not limited to the above-described embodiment. Appropriate modifications and changes are possible by those skilled in the art. The scope of the present invention is indicated by the claims, not the above-described embodiment. Furthermore, the scope of the present invention includes modifications and changes from the embodiments within the scope of the claims and the equivalent scope. [Explanation of symbols]

[0051] ACout: AC output line C11, C12, C21, C22, C31, C32, C4, C5... Capacitors Ci: Input capacitor Co…Output capacitor DCin: DC input line L1, L2: Inductors L11, L12...Coil L21, L22...Coil RL…Load circuit Vin…DC power supply Z1, Z2, Z3...Impedance elements 1. Electrical path 10...Inverter circuit 12...Switching circuit 13...DC input voltage detection circuit 14...Feedback control circuit 15...AC output voltage detection circuit 16...AC output current detection circuit 21...First half-bridge capacitor circuit 22...Second half-bridge capacitor circuit 31…First common mode choke coil 32…Second common mode choke coil 101, 102A, 102B, 102C, 102D, 102E, 103, 104, 105, 106...Switching power supply

Claims

1. An inverter circuit and a noise reduction circuit are provided, The inverter circuit includes: A DC input line; an AC output line; An inductor; a switching circuit for causing a switching current to flow through the inductor; an input capacitor connected in parallel between the DC input lines; an output capacitor connected in parallel between the AC output lines; a DC input voltage detection circuit for detecting a voltage between the DC input lines; an AC output voltage detection circuit for detecting a voltage between the AC output lines; an AC output current detection circuit for detecting a current in the AC output line; a feedback control circuit having a reference potential connected to a reference potential line of the DC input line, and controlling the switching circuit based on a voltage of the DC input line so that an AC output voltage or an AC output current of the AC output line becomes a predetermined value; Equipped with The noise reduction circuit includes: a first half-bridge capacitor circuit connected between the DC input lines; a second half-bridge capacitor circuit connected between the AC output lines; a first common mode choke coil connected between the first half-bridge capacitor circuit and the second half-bridge capacitor circuit; an electrical path that constitutes a noise balancing circuit electrically connecting a midpoint of the first half-bridge capacitor circuit and a midpoint of the second half-bridge capacitor circuit; the DC input voltage detection circuit is connected between the first half-bridge capacitor circuit and the switching circuit; the AC output voltage detection circuit is connected between the output capacitor and the second half-bridge capacitor circuit; Switching power supply.

2. An inverter circuit and a noise reduction circuit are provided, The inverter circuit includes: A DC input line; an AC output line; An inductor; a switching circuit for causing a switching current to flow through the inductor; an input capacitor connected in parallel between the DC input lines; an output capacitor connected in parallel between the AC output lines; a DC input voltage detection circuit for detecting a voltage between the DC input lines; an AC output voltage detection circuit for detecting a voltage between the AC output lines; an AC output current detection circuit for detecting a current in the AC output line; a feedback control circuit having a reference potential connected to a reference potential line of the DC input line, and controlling the switching circuit based on a voltage of the DC input line so that an AC output voltage or an AC output current of the AC output line becomes a predetermined value; Equipped with The noise reduction circuit includes: a first half-bridge capacitor circuit connected between the DC input lines; a second half-bridge capacitor circuit connected between the AC output lines; a first common mode choke coil connected between the first half-bridge capacitor circuit and the second half-bridge capacitor circuit; an electrical path electrically connecting a midpoint of the first half-bridge capacitor circuit and a midpoint of the second half-bridge capacitor circuit and constituting a noise balancing circuit that balances common mode noise of a potential different from ground; the DC input voltage detection circuit is connected between the first half-bridge capacitor circuit and the switching circuit; the AC output voltage detection circuit is connected between the output capacitor and the second half-bridge capacitor circuit; Switching power supply.

3. An inverter circuit and a noise reduction circuit are provided, The inverter circuit includes: A DC input line; an AC output line; An inductor; a switching circuit for causing a switching current to flow through the inductor; an input capacitor connected in parallel between the DC input lines; an output capacitor connected in parallel between the AC output lines; a DC input voltage detection circuit for detecting a voltage between the DC input lines; an AC output voltage detection circuit for detecting a voltage between the AC output lines; an AC output current detection circuit for detecting a current in the AC output line; a feedback control circuit having a reference potential connected to a reference potential line of the DC input line, and controlling the switching circuit based on a voltage of the DC input line so that an AC output voltage or an AC output current of the AC output line becomes a predetermined value; Equipped with The noise reduction circuit includes: a first half-bridge capacitor circuit connected between the DC input lines; a second half-bridge capacitor circuit connected between the AC output lines; a first common mode choke coil connected between the first half-bridge capacitor circuit and the second half-bridge capacitor circuit; an electrical path that electrically connects a midpoint of the first half-bridge capacitor circuit and a midpoint of the second half-bridge capacitor circuit to configure a noise balancing circuit that balances common mode noise of a potential different from that of ground; The noise balancing circuit suppresses the effect of the common mode noise on the feedback control circuit; the DC input voltage detection circuit is connected between the first half-bridge capacitor circuit and the switching circuit; the AC output voltage detection circuit is connected between the output capacitor and the second half-bridge capacitor circuit; Characterized in that Switching power supply.

4. An impedance element having an inductance component or a resistance component is connected in series to the electrical path.

4. The switching power supply device according to claim 1.

5. an impedance element connected between the electrical path and a ground and having a capacitance component, an inductance component, or a resistance component; 5. The switching power supply device according to claim 1.

6. a second common mode choke coil connected to a load side of the second half-bridge capacitor circuit; 6. The switching power supply device according to claim 1.

7. The AC output line is connected to the two capacitors connected in series, and the midpoint of the capacitor is connected to ground.

7. The switching power supply device according to claim 1.

8. a capacitor connected between a reference potential of the feedback control circuit and the electrical path; 8. The switching power supply device according to claim 1.

9. a capacitor connected between a reference potential of the feedback control circuit and ground; 9. The switching power supply device according to claim 1.

10. Each of the DC input voltage detection circuit and the AC output voltage detection circuit is configured by a series circuit of a plurality of resistor elements connected in series, and detects a midpoint voltage of each series circuit.

10. The switching power supply device according to claim 1.

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