TW201626708A - DC-to-AC dual-buck conversion system and method of operating the same - Google Patents

Abstract

A DC-to-AC dual-buck conversion system mainly includes an input capacitor assembly, a first conversion circuit, a second conversion circuit, a freewheeling diode, and a control circuit. The input capacitor assembly has a first capacitor and a second capacitor, which are connected to a neutral point and receive a DC input voltage. The first conversion circuit and the second conversion circuit are connected in parallel to the capacitor assembly. The freewheeling diode is connected to the first conversion circuit and the second conversion circuit. The control circuit produces a plurality of control signals to control the first conversion circuit and the second conversion circuit so as to reduce leakage current caused by parasitic capacitance voltage.

Description

Double-drop DC-to-AC conversion system and operation method thereof 【0001】

The invention relates to a double-drop DC-to-AC conversion system and an operation method thereof, in particular to a dual-drop DC-to-AC conversion system applied to a solar photovoltaic power conversion system and an operation method thereof.

【0002】

Please refer to the first diagram for a circuit diagram of a prior art dual-buck inverter. The dual buck inverter receives the DC input voltage Vdc and converts the DC input voltage Vdc to an AC output voltage Vac. The dual buck inverter includes two sets of step-down circuits, which are a first buck circuit BC1 and a second buck circuit BC2, respectively. The first step-down circuit BC1 mainly includes a first bridge arm Lg1a and a second bridge arm Lg2a, and the first bridge arm Lg1a includes a first switch S1a and one of the first switch S1a connected in series. a diode D1a; the second bridge arm Lg2a includes a second switch S2a and a second diode D2a connected in series with the second switch S2a. The second step-down circuit BC2 mainly includes a third bridge arm Lg3a and a fourth bridge arm Lg4a, and the third bridge arm Lg3a includes a third switch S3a and one third of the third switch S3a connected in series. The fourth bridge arm Lg4a includes a fourth switch S4a and a fourth diode D4a connected in series with the fourth switch S4a. In addition, the first step-down circuit BC1 and the second step-down circuit BC2 are connected in parallel with an input capacitor C1a.

[0003]

Referring to the second figure, the waveform diagram of the driving signal of the prior art dual buck inverter is shown. And generating, by a driving signal generating circuit (not shown), a plurality of control signals corresponding to the first switch S1a, the second switch S2a, the third switch S3a, and the fourth switch S4a, respectively, being a first control signal Sca1, a second control signal Sca2, a third control signal Sca3, and a fourth control signal Sca4.

[0004]

The first control signal Sca1 and the second control signal Sca2 are a pair of complementary low frequency signals. When the AC output voltage Vac is positive half cycle (time t0~t1 interval), the first control signal Sca1 is high level to turn on the first switch S1a, and the second control signal Sca2 is low level to cut off the second Switch S2a. The third control signal Sca3 is at a low level to turn off the third switch S3a, and the fourth control signal Sca4 is high frequency to switch the fourth switch S4a. When the AC output voltage Vac is negative half cycle (time t1~t2 interval), the first control signal Sca1 is low level to cut off the first switch S1a, and the second control signal Sca2 is high level to conduct the second Switch S2a. The third control signal Sca3 switches the third switch S3a at a high frequency, and the fourth control signal Sca4 is at a low level to turn off the fourth switch S4a.

[0005]

However, in this dual buck inverter architecture, since the AC output voltage Vac changes greatly, the voltage on the parasitic capacitances Cp1 and Cp2 changes greatly, and the rapidly changing leakage currents Icp1, Icp2 are also generated. That is, the larger the parasitic capacitance voltage changes, the more the leakage current increases. Moreover, the conventional dual buck inverter architecture is prone to short-circuited short-circuit faults at zero crossing points.

[0006]

Therefore, how to design a dual-drop DC-to-AC converter system and its operation method, through the dual-down inverter (dual-buck inverter) architecture, realize the energy storage and release operation of the output inductor. A freewheeling diode is also provided to provide a freewheeling path for positive and negative half cycle operation. Furthermore, by connecting the filter circuit to the neutral point on the input DC side, the influence of the leakage current caused by the parasitic capacitance voltage is greatly reduced, and the short-circuiting of the short-crossing point at the zero crossing point is solved. A major issue that the creators of this case want to overcome and solve.

【0007】

It is an object of the present invention to provide a dual drop DC to AC conversion system that overcomes the problems of the prior art. Therefore, the dual-drop DC-to-AC conversion system of the present invention converts the DC input voltage into an AC output voltage. The dual-drop DC-to-AC conversion system includes an input capacitor group, a first conversion circuit, a second conversion circuit, a freewheeling diode, a first filter circuit, a second filter circuit, and a control circuit. . The input capacitor group includes a first capacitor and a second capacitor. The first capacitor is coupled to the second capacitor and connected to a neutral point, and receives the DC input voltage. The first conversion circuit is connected in parallel with the input capacitance group. The second conversion circuit is connected in parallel with the input capacitor group. The freewheeling diode system connects the first conversion circuit and the second conversion circuit. The first filter circuit is connected to the first conversion circuit and the second conversion circuit, and an output side of the first filter circuit is connected to the neutral point. The second filter circuit is connected to the first conversion circuit and the second conversion circuit, and an output side of the second filter circuit is connected to the neutral point. The control circuit generates a plurality of control signals for respectively controlling the first conversion circuit and the second conversion circuit to reduce leakage current caused by a parasitic capacitance effect of the DC input voltage.

[0008]

Another object of the present invention is to provide a method of operating a dual drop DC to AC conversion system to overcome the problems of the prior art. Therefore, the dual-drop DC-to-AC conversion system of the present invention converts the DC input voltage into an AC output voltage. The method includes the following steps: (a) providing an input capacitor group, receiving the DC input voltage, the input capacitor group comprising a first capacitor and a second capacitor, the first capacitor and the second capacitor Connecting a neutral point; (b) providing a first conversion circuit and a second conversion circuit, respectively connecting the input capacitance group; (c) providing a freewheeling diode, connecting the first conversion circuit and the a second conversion circuit; (d) providing a first filter circuit connecting the first conversion circuit and the second conversion circuit, and an output side of the first filter circuit is connected to the neutral point; (e) providing a a second filter circuit connecting the first conversion circuit and the second conversion circuit, and an output side of the second filter circuit is connected to the neutral point; and (f) providing a control circuit for generating a plurality of control signals The first conversion circuit and the second conversion circuit are respectively controlled to reduce leakage current caused by a parasitic capacitance effect of the DC input voltage.

【0009】

In order to further understand the technology, the means and the effect of the present invention in order to achieve the intended purpose, refer to the following detailed description of the invention and the accompanying drawings. The detailed description is to be understood as illustrative and not restrictive.

[0050]

[prior art]

[0051]

Vdc‧‧‧DC input voltage

[0052]

Vac‧‧‧AC output voltage

[0053]

BC1‧‧‧First Step-Down Circuit

[0054]

BC2‧‧‧second buck circuit

[0055]

Lg1a‧‧‧ first bridge arm

[0056]

Lg2a‧‧‧ second bridge arm

[0057]

Lg3a‧‧‧ third bridge arm

[0058]

Lg4a‧‧‧ fourth bridge arm

[0059]

S1a‧‧‧ first switch

[0060]

S2a‧‧‧second switch

[0061]

S3a‧‧‧ third switch

[0062]

S4a‧‧‧fourth switch

[0063]

D1a‧‧‧First Diode

[0064]

D2a‧‧‧Secondary

[0065]

D3a‧‧‧ third diode

[0066]

D4a‧‧‧ fourth diode

[0067]

C1a‧‧‧Input Capacitor

[0068]

Sca1‧‧‧ first control signal

[0069]

Sca2‧‧‧second control signal

[0070]

Sca3‧‧‧ third control signal

[0071]

Sca4‧‧‧ fourth control signal

[0072]

Cp1, Cp2‧‧‧ parasitic capacitance

[0073]

Icp1, Icp2‧‧‧ leakage current

[0074]

T0, t1, t2‧‧‧ time

[0075]

﹝this invention﹞

[0076]

Vdc‧‧‧DC input voltage

[0077]

Vac‧‧‧AC output voltage

[0078]

10‧‧‧Input Capacitor Group

[0079]

11‧‧‧First conversion circuit

[0080]

12‧‧‧Second conversion circuit

[0081]

13‧‧‧Continuous current diode

[0082]

21‧‧‧First filter circuit

[0083]

22‧‧‧Second filter circuit

[0084]

30‧‧‧Control circuit

[0085]

101‧‧‧first capacitor

[0086]

102‧‧‧second capacitor

[0087]

301‧‧‧ first comparison unit

[0088]

302‧‧‧Second comparison unit

[0089]

303‧‧‧Signal absolute unit

[0090]

304‧‧‧Inverting unit

[0091]

Po‧‧‧Neutral point

[0092]

S1‧‧‧first power switch

[0093]

S2‧‧‧second power switch

[0094]

Sx1‧‧‧First Auxiliary Power Switch

[0095]

Sx2‧‧‧Second auxiliary power switch

[0096]

Sx3‧‧‧ third auxiliary power switch

[0097]

Sx4‧‧‧fourth auxiliary power switch

[0098]

D1‧‧‧First Diode

[0099]

D2‧‧‧ second diode

【0100】

D3‧‧‧ third diode

【0101】

D4‧‧‧ fourth diode

【0102】

L1‧‧‧first output inductor

【0103】

L2‧‧‧second output inductor

[0104]

L3‧‧‧ third output inductor

【0105】

L4‧‧‧fourth output inductor

【0106】

C1‧‧‧First output capacitor

【0107】

C2‧‧‧second output capacitor

【0108】

Sc‧‧‧ output control signal

【0109】

Scx1‧‧‧First Auxiliary Output Control Signal

[0110]

Scx2‧‧‧Second auxiliary output control signal

[0111]

Sac‧‧‧AC voltage signal

[0112]

S|ac|‧‧‧ positive voltage signal

[0113]

Stri‧‧‧ triangular carrier signal

【0114】

Lps‧‧‧ half-week energy storage circuit

[0115]

Lpr‧‧‧ half-week release circuit

[0116]

Lns‧‧‧negative half-cycle energy storage circuit

【0117】

Lnr‧‧‧negative half-cycle release energy loop

【0118】

T0, t1, t2‧‧‧ time

【0119】

S10~S60‧‧‧Steps

[0120]

Cp1, Cp2‧‧‧ parasitic capacitance

【0121】

Icp1, Icp2‧‧‧ leakage current

[0010]

1 is a circuit diagram of a prior art dual-buck inverter;

[0011]

2 is a waveform diagram of a driving signal of a prior art dual buck inverter;

[0012]

3 is a circuit diagram of a preferred embodiment of the dual-drop DC-to-AC conversion system of the present invention;

[0013]

4 is a circuit diagram of a control circuit of the dual-drop DC-to-AC conversion system of the present invention;

[0014]

5 is a waveform diagram of a switch control signal of the dual-drop DC-to-AC conversion system of the present invention;

[0015]

6 is a circuit diagram of a preferred embodiment of the dual-drop DC-to-AC conversion system of the present invention in a positive half-cycle energy storage operation;

[0016]

7 is a circuit diagram of a preferred embodiment of the dual-drop DC-to-AC conversion system of the present invention in a positive half-cycle release operation;

[0017]

8 is a circuit diagram of a preferred embodiment of the dual-drop DC-to-AC conversion system of the present invention in a negative half-cycle energy storage operation;

[0018]

9 is a circuit diagram of a preferred embodiment of the dual-drop DC-to-AC conversion system of the present invention in a negative half-cycle release operation; and

[0019]

FIG. 10 is a flow chart of the operation method of the dual-drop DC-to-AC conversion system of the present invention.

[0020]

The technical content and detailed description of the present invention are as follows:

[0021]

Please refer to FIG. 3, which is a circuit diagram of a preferred embodiment of the dual-drop DC-to-AC conversion system of the present invention. The DC-to-AC conversion system can be a solar photovoltaic power conversion system, and the dual-drop DC-to-AC conversion system converts the DC input voltage Vdc into an AC output voltage Vac. The dual-drop DC-to-AC conversion system includes an input capacitor group 10, a first conversion circuit 11, a second conversion circuit 12, a freewheeling diode 13, a first filter circuit 21, and a second filter. Circuit 22 and a control circuit 30. The input capacitor group 10 includes a first capacitor 101 and a second capacitor 102. The first capacitor 101 and the second capacitor 102 receive the DC input voltage Vdc. The first capacitor 101 and the second capacitor 102 are connected to a neutral point Po to maintain the voltage across the first capacitor 101 and the second capacitor 102 equal to half of the DC input voltage Vdc.

[0022]

The first conversion circuit 11 is connected in parallel to the input capacitor group 10. The second conversion circuit 12 is connected in parallel to the input capacitor group 10. The freewheeling diode 13 is connected to the first conversion circuit 11 and the second conversion circuit 12. The first filter circuit 21 is connected to the first conversion circuit 11 and the second conversion circuit 12, and an output side of the first filter circuit 21 is connected to the neutral point Po. The second filter circuit 22 is connected to the first conversion circuit 11 and the second conversion circuit 12, and the output side of the second filter circuit 22 is connected to the neutral point Po. The control circuit 30 generates a plurality of control signals for controlling the first conversion circuit 11 and the second conversion circuit 12 to reduce leakage current caused by a parasitic capacitance effect of the DC input voltage Vdc. The operation instructions of the dual-drop DC-to-AC conversion system will be described in detail later.

[0023]

The first conversion circuit 11 includes a first power switch S1, a first auxiliary power switch Sx1, a second auxiliary power switch Sx2, a first diode D1, and a second diode D2. The first power switch S1 includes a first end and a second end. The first end of the first power switch S1 is connected to the first capacitor 101. The first auxiliary power switch Sx1 includes a first end and a second end; the first end of the first auxiliary power switch Sx1 is connected to the second end of the first power switch S1. The second auxiliary power switch Sx2 includes a first end and a second end; the first end of the second auxiliary power switch Sx2 is connected to the second end of the first power switch S1. The first diode D1 includes an anode and a cathode; the cathode of the first diode D1 is connected to the second end of the first auxiliary power switch Sx1. The second diode D2 includes an anode and a cathode; the cathode of the second diode D2 is connected to the second end of the second auxiliary power switch Sx2. The anode of the first diode D1 and the anode of the second diode D2 are connected to the second capacitor 102.

[0024]

The second conversion circuit 12 includes a second power switch S2, a third auxiliary power switch Sx3, a fourth auxiliary power switch Sx4, a third diode D3, and a fourth diode D4. The second power switch S2 includes a first end and a second end; the first end of the second power switch S2 is coupled to the second capacitor 102. The third auxiliary power switch Sx3 includes a first end and a second end; the first end of the third auxiliary power switch Sx3 is connected to the second end of the second power switch S2. The fourth auxiliary power switch Sx4 includes a first end and a second end; the first end of the fourth auxiliary power switch Sx4 is connected to the second end of the second power switch S2. The third diode D3 includes an anode and a cathode; the anode of the third diode D3 is connected to the second end of the third auxiliary power switch Sx3. The fourth diode D4 includes an anode and a cathode; the anode of the fourth diode D4 is connected to the second end of the fourth auxiliary power switch Sx4. The cathode of the third diode D3 and the cathode of the fourth diode D4 are connected to the first capacitor 101.

[0025]

The first filter circuit 21 includes a first output inductor L1, a second output inductor L2, and a first output capacitor C1. One end of the first output inductor L1 is connected to one end of the second output inductor L2, and is connected to one end of the first output capacitor C1. The other end of the first output inductor L1 is connected to the second end of the first auxiliary power switch Sx1. The other end of the second output inductor L2 is connected to the second end of the fourth auxiliary power switch Sx4, and the other end of the first output capacitor C1 is connected to the neutral point Po.

[0026]

The second filter circuit 22 includes a third output inductor L3, a fourth output inductor L4, and a second output capacitor C2. One end of the third output inductor L3 is connected to one end of the fourth output inductor L4, and is connected to one end of the second output capacitor C2. The other end of the third output inductor L3 is connected to the second end of the second auxiliary power switch Sx2. The other end of the fourth output inductor L4 is connected to the second end of the third auxiliary power switch Sx3, and the other end of the second output capacitor C2 is connected to the neutral point Po.

[0027]

Please refer to FIG. 4 , which is a circuit diagram of a control circuit of the dual-drop DC-to-AC conversion system of the present invention. The control circuit 30 includes a signal absolute value unit 303, a first comparison unit 301, a second comparison unit 302, and an inversion unit 304. The signal absolute value unit 303 receives an AC voltage signal Sac to convert the AC voltage signal Sac into a positive voltage signal S|ac|.

[0028]

The first comparison unit 301 has an inverting input, a non-inverting input, and a first output. The non-inverting input receives the positive voltage signal S|ac|, and the inverting input receives a triangular carrier signal Stri; the first output outputs an output control signal Sc. The second comparison unit 302 has an inverting input, a non-inverting input, and a second output. The non-inverting input terminal receives the AC voltage signal Sac, and the inverting input terminal is grounded; the second output terminal outputs a first auxiliary output control signal Scx1. The inverting unit 304 receives the first auxiliary output control signal Scx1 to invert the first auxiliary output control signal Scx1 into a second auxiliary output control signal Scx2.

[0029]

The triangular carrier signal Stri is a high frequency carrier signal. It is worth mentioning that the switching frequency of the pulse width modulation signal is equal to the frequency of the triangular carrier signal Stri. Furthermore, the switching frequency of the first auxiliary output control signal Scx1 and the second auxiliary output control signal Scx2 is equal to the low frequency mains frequency of the alternating voltage signal Sac.

[0030]

Referring to FIG. 5, it is a waveform diagram of a switch control signal of the dual-drop DC-to-AC conversion system of the present invention. When the AC output voltage Vac is positive half cycle (time t0~t1 interval), the output control signal Sc is a high frequency switching signal, the first auxiliary output control signal Scx1 is a low frequency high level signal, and the second The auxiliary output control signal Scx2 is a low frequency low level signal. When the AC output voltage Vac is negative half cycle (time t1~t2 interval), the output control signal Sc is a high frequency switching signal, the first auxiliary output control signal Scx1 is a low frequency low level signal, and the second The auxiliary output control signal Scx2 is a low frequency high level signal. The output control signal Sc is a pulse width modulation signal (PWM signal). In addition, the first auxiliary output control signal Scx1 and the second auxiliary output control signal Scx2 are low frequency signals that are complementary to each other. That is, when the first auxiliary output control signal Scx1 is at a high level, the second auxiliary output control signal Scx2 is at a low level; conversely, when the first auxiliary output control signal Scx1 is at a low level, the first The second auxiliary output control signal Scx2 is at a high level.

[0031]

Please refer to FIG. 6 , which is a circuit diagram of a preferred embodiment of the dual-drop DC-to-AC conversion system of the present invention in a positive half-cycle energy storage operation. When the AC output voltage is a positive half cycle operation, the output control signal Sc is high frequency switched to turn on the first power switch S1 and the second power switch S2, and the first auxiliary output control signal Scx1 is turned on by the low frequency high level. When the auxiliary power switch Sx1 and the third auxiliary power switch Sx3, and the second auxiliary output control signal Scx2 low frequency low level turns off the second auxiliary power switch Sx2 and the fourth auxiliary power switch Sx4, the first output inductor L1 And the fourth output inductor L4 is an energy storage operation. At this time, the dual-drop DC-to-AC conversion system provides a positive half-cycle energy storage circuit Lps, which is sequentially the DC input voltage Vdc, and the first power switch S1. The first auxiliary power switch Sx1, the first output inductor L1, the AC output voltage Vac, the fourth output inductor L4, the third auxiliary power switch Sx3, and the second power switch S2 are returned to the DC input voltage. Vdc.

[0032]

Please refer to FIG. 7 which is a circuit diagram of a preferred embodiment of the dual-drop DC-to-AC conversion system of the present invention in a positive half-cycle release operation. When the AC output voltage is a positive half cycle operation, the output control signal Sc is high frequency switched off the first power switch S1 and the second power switch S2, and the first auxiliary output control signal Scx1 is turned on at the low frequency high level. When the auxiliary power switch Sx1 and the third auxiliary power switch Sx3, and the second auxiliary output control signal Scx2 low frequency low level turns off the second auxiliary power switch Sx2 and the fourth auxiliary power switch Sx4, the first output inductor L1 And the fourth output inductor L4 is a release operation. At this time, the double-drop DC-to-AC conversion system provides a positive half-cycle release circuit Lpr, which is the first output inductor L1, the AC output voltage Vac, The fourth output inductor L4, the third auxiliary power switch Sx3, the freewheeling diode 13 and the first auxiliary power switch Sx1 are configured to return to the first output inductor L1.

[0033]

Please refer to FIG. 8 , which is a circuit diagram of a preferred embodiment of the dual-drop DC-to-AC conversion system of the present invention for negative half-cycle energy storage operation. When the AC output voltage is negative half-cycle operation, the output control signal Sc is high-frequency switched to turn on the first power switch S1 and the second power switch S2, and the first auxiliary output control signal Scx1 is low-frequency low-level to cut off the first When the auxiliary power switch Sx1 and the third auxiliary power switch Sx3, and the second auxiliary output control signal Scx2 low frequency high level turns on the second auxiliary power switch Sx2 and the fourth auxiliary power switch Sx4, the second output inductor L2 And the third output inductor L3 is an energy storage operation. At this time, the dual-drop DC-to-AC conversion system provides a negative half-cycle energy storage circuit Lns, which is sequentially the DC input voltage Vdc, and the first power switch S1. The second auxiliary power switch Sx2, the third output inductor L3, the AC output voltage Vac, the second output inductor L2, the fourth auxiliary power switch Sx4, and the second power switch S2 are returned to the DC input voltage. Vdc.

[0034]

Please refer to FIG. 9 which is a circuit diagram of a preferred embodiment of the dual-drop DC-to-AC conversion system of the present invention in a negative half-cycle release operation. When the AC output voltage is negative half-cycle operation, the output control signal Sc is high-frequency switched off the first power switch S1 and the second power switch S2, and the first auxiliary output control signal Scx1 is low-frequency low-level to cut off the first When the auxiliary power switch Sx1 and the third auxiliary power switch Sx3, and the second auxiliary output control signal Scx2 low frequency high level turns on the second auxiliary power switch Sx2 and the fourth auxiliary power switch Sx4, the second output inductor L2 And the third output inductor L3 is a release operation. At this time, the double-drop DC-to-AC conversion system provides a negative half-cycle release circuit Lnr, which is the third output inductor L3, the AC output voltage Vac, The first output inductor L1, the fourth auxiliary power switch Sx4, the freewheeling diode 13, and the second auxiliary power switch Sx2 are returned to the third output inductor L3.

[0035]

Please refer to FIG. 10, which is a flow chart of the operation method of the dual-drop DC-to-AC conversion system of the present invention. The dual-drop DC-to-AC conversion system converts the DC input voltage into an AC output voltage. The operation method includes the following steps: First, an input capacitor group is provided to receive the DC input voltage, the input capacitor group includes a first capacitor and a second capacitor, and the first capacitor is connected to the second capacitor A neutral point (S10).

[0036]

Then, a first conversion circuit and a second conversion circuit are provided, and the first conversion circuit and the second conversion circuit are respectively connected in parallel with the input capacitance group (S20). The first conversion circuit includes a first power switch, a first auxiliary power switch, a second auxiliary power switch, a first diode, and a second diode. The first power-on relationship includes a first end and a second end; the first end of the first power switch is coupled to the first capacitor. The first auxiliary power-on relationship includes a first end and a second end; the first end of the first auxiliary power switch is coupled to the second end of the first power switch. The second auxiliary power-on relationship includes a first end and a second end; the first end of the second auxiliary power switch is coupled to the second end of the first power switch. The first two-pole system includes an anode and a cathode; the cathode of the first diode is connected to the second end of the first auxiliary power switch. The second diode system includes an anode and a cathode; the cathode of the second diode is connected to the second end of the second auxiliary power switch; the anode of the first diode and the second The anode of the pole body is connected to the second capacitor.

[0037]

The second conversion circuit includes a second power switch, a third auxiliary power switch, a fourth auxiliary power switch, a third diode, and a fourth diode. The second power-on relationship includes a first end and a second end; the first end of the second power switch is coupled to the second capacitor. The third auxiliary power-on relationship includes a first end and a second end; the first end of the third auxiliary power switch is coupled to the second end of the second power switch. The fourth auxiliary power-on relationship includes a first end and a second end; the first end of the fourth auxiliary power switch is coupled to the second end of the second power switch. The third diode system includes an anode and a cathode; the anode of the third diode is connected to the second end of the third auxiliary power switch. The fourth diode system includes an anode and a cathode; the anode of the fourth diode is connected to the second end of the fourth auxiliary power switch; the cathode of the third diode and the fourth The cathode of the pole body is connected to the first capacitor.

[0038]

Then, a freewheeling diode is provided to connect the first conversion circuit and the second conversion circuit (S30). Then, a first filter circuit is provided to connect the first conversion circuit and the second conversion circuit, and an output side of the first filter circuit is connected to the neutral point (S40). The first filter circuit includes a first output inductor, a second output inductor, and a first output capacitor. One end of the first output inductor is connected to one end of the second output inductor, and is connected to one end of the first output capacitor. The other end of the first output inductor is connected to the second end of the first auxiliary power switch. The other end of the second output inductor is connected to the second end of the fourth auxiliary power switch, and the other end of the first output capacitor is connected to the neutral point.

[0039]

Then, a second filter circuit is provided to connect the first conversion circuit and the second conversion circuit, and an output side of the second filter circuit is connected to the neutral point (S50). The second filter circuit includes a third output inductor, a fourth output inductor, and a second output capacitor. One end of the third output inductor is connected to one end of the fourth output inductor, and is connected to one end of the second output capacitor. The other end of the third output inductor is connected to the second end of the second auxiliary power switch. The other end of the fourth output inductor is connected to the second end of the third auxiliary power switch, and the other end of the second output capacitor is connected to the neutral point.

[0040]

Finally, a control circuit is provided to generate a plurality of control signals for respectively controlling the first conversion circuit and the second conversion circuit to reduce leakage current caused by a parasitic capacitance effect of the DC input voltage (S60). The control circuit includes a signal absolute value unit, a first comparison unit, a second comparison unit, and an inverting unit. The signal absolute value unit receives an alternating voltage signal to convert the alternating voltage signal into a positive voltage signal. The first comparison unit has an inverting input, a non-inverting input, and a first output. The non-inverting input receives the positive voltage signal, and the inverting input receives a triangular carrier signal; the first output outputs an output control signal. The second comparison unit has an inverting input terminal, a non-inverting input terminal and a second output terminal; the non-inverting input terminal receives the AC voltage signal, and the inverting input terminal is grounded; the second output The end system outputs a first auxiliary output control signal. The inverting unit receives the first auxiliary output control signal to invert the first auxiliary output control signal to be a second auxiliary output control signal.

[0041]

The triangular carrier signal is a high frequency carrier signal. It is worth mentioning that the switching frequency of the pulse width modulation signal is equal to the frequency of the triangular carrier signal. Furthermore, the switching frequency of the first auxiliary output control signal and the second auxiliary output control signal is equal to the low frequency mains frequency of the alternating voltage signal.

[0042]

When the AC output voltage is positive half cycle, the output control signal is a high frequency switching signal, the first auxiliary output control signal is a low frequency high level signal, and the second auxiliary output control signal is a low frequency low level signal. When the AC output voltage is negative half cycle, the output control signal is a high frequency switching signal, the first auxiliary output control signal is a low frequency low level signal, and the second auxiliary output control signal is a low frequency high level signal. The output control signal is a PWM signal. In addition, the first auxiliary output control signal and the second auxiliary output control signal are low frequency signals that are complementary to each other. That is, when the first auxiliary output control signal is at a high level, the second auxiliary output control signal is at a low level; conversely, when the first auxiliary output control signal is at a low level, the second auxiliary output is The control signal is at a high level.

[0043]

When the AC output voltage is a positive half cycle operation, the output control signal is high frequency switched to turn on the first power switch and the second power switch, and the first auxiliary output control signal low frequency high level turns on the first auxiliary power switch and The third auxiliary power switch, and the second auxiliary output control signal low frequency low level turns off the second auxiliary power switch and the fourth auxiliary power switch, the first output inductor and the fourth output inductor are energy storage operations At this time, the dual-drop DC-to-AC conversion system provides a positive half-cycle energy storage circuit for the DC input voltage, the first power switch, the first auxiliary power switch, and the first output inductor, The AC output voltage, the fourth output inductor, the third auxiliary power switch, and the second power switch are returned to the DC input voltage.

[0044]

When the AC output voltage is a positive half cycle operation, the output control signal is high frequency switched off the first power switch and the second power switch, and the first auxiliary output control signal low frequency high level turns on the first auxiliary power switch and The third auxiliary power switch, and the second auxiliary output control signal low frequency low level turns off the second auxiliary power switch and the fourth auxiliary power switch, the first output inductor and the fourth output inductor are release operations At this time, the dual-drop DC-to-AC conversion system provides a positive half-cycle release circuit sequentially for the first output inductor, the AC output voltage, the fourth output inductor, and the third auxiliary power switch. The freewheeling diode is formed by the first auxiliary power switch, and returns to the first output inductor.

[0045]

When the AC output voltage is a negative half cycle operation, the output control signal is high frequency switched to turn on the first power switch and the second power switch, and the first auxiliary output control signal low frequency low level turns off the first auxiliary power switch and The second auxiliary power switch, and the second auxiliary output control signal low frequency high level turns on the second auxiliary power switch and the fourth auxiliary power switch, the second output inductor and the third output inductor are energy storage operations At this time, the dual-drop DC-to-AC conversion system provides a negative half-cycle energy storage circuit for the DC input voltage, the first power switch, the second auxiliary power switch, and the third output inductor. The AC output voltage, the second output inductor, the fourth auxiliary power switch, and the second power switch are returned to the DC input voltage.

[0046]

When the AC output voltage is a negative half cycle operation, the output control signal is high frequency switched off the first power switch and the second power switch, and the first auxiliary output control signal low frequency low level is turned off by the first auxiliary power switch The second auxiliary power switch, and the second auxiliary output control signal low frequency high level turns on the second auxiliary power switch and the fourth auxiliary power switch, the second output inductor and the third output inductor are release operations At this time, the dual-drop DC-to-AC conversion system provides a negative half-cycle release circuit sequentially for the third output inductor, the AC output voltage, the first output inductor, the fourth auxiliary power switch, and the The freewheeling diode, the second auxiliary power switch, returns to the third output inductor.

[0047]

In summary, the present invention has the following features and advantages:

[0048]

The first output inductor is implemented by the dual-down converter architecture formed by the first conversion circuit 11, the second conversion circuit 12, the first filter circuit 21, and the second filter circuit 22. L1, the second output inductor L2, the third output inductor L3, and the fourth output inductor L4 are stored and discharged. The freewheeling diode 13 is further provided to provide a freewheeling path for positive and negative half-cycle operation to achieve the first output inductor L1, the second output inductor L2, the third output inductor L3, and the fourth output inductor. The release current path of L4. Furthermore, the first filter circuit 21 and the second filter circuit 22 are connected to the neutral point Po of the input DC side, thereby greatly reducing the influence of the leakage current caused by the parasitic capacitance voltage, and solving the zero crossing point occurs. Short-circuit through short action.

[0049]

However, the above description is only for the detailed description and the drawings of the preferred embodiments of the present invention, and the present invention is not limited thereto, and is not intended to limit the present invention. The scope of the patent application is intended to be included in the scope of the present invention, and any one skilled in the art can readily appreciate it in the field of the present invention. Variations or modifications may be covered by the patents in this case below.

Vdc‧‧‧DC input voltage

Vac‧‧‧AC output voltage

10‧‧‧Input Capacitor Group

11‧‧‧First conversion circuit

12‧‧‧Second conversion circuit

13‧‧‧Continuous current diode

21‧‧‧First filter circuit

22‧‧‧Second filter circuit

30‧‧‧Control circuit

101‧‧‧first capacitor

102‧‧‧second capacitor

Po‧‧‧Neutral point

S1‧‧‧first power switch

S2‧‧‧second power switch

Sx1‧‧‧First Auxiliary Power Switch

Sx2‧‧‧Second auxiliary power switch

Sx3‧‧‧ third auxiliary power switch

Sx4‧‧‧fourth auxiliary power switch

D1‧‧‧First Diode

D2‧‧‧ second diode

D3‧‧‧ third diode

D4‧‧‧ fourth diode

L1‧‧‧first output inductor

L2‧‧‧second output inductor

L3‧‧‧ third output inductor

L4‧‧‧fourth output inductor

C1‧‧‧First output capacitor

C2‧‧‧second output capacitor

Sc‧‧‧ output control signal

Scx1‧‧‧First Auxiliary Output Control Signal

Scx2‧‧‧Second auxiliary output control signal

Cp1, Cp2‧‧‧ parasitic capacitance

Icp1, Icp2‧‧‧ leakage current

Claims (20)

[Item 1] A dual-drop DC-to-AC conversion system converts a DC input voltage into an AC output voltage; the dual-drop DC-to-AC conversion system includes:
An input capacitor group includes a first capacitor and a second capacitor, the first capacitor and the second capacitor are connected to a neutral point, and receive the DC input voltage;
a first conversion circuit is connected in parallel with the input capacitor group;
a second conversion circuit is connected in parallel with the input capacitor group;
a freewheeling diode connected to the first conversion circuit and the second conversion circuit;
a first filter circuit is connected to the first conversion circuit and the second conversion circuit, and an output side of the first filter circuit is connected to the neutral point;
a second filter circuit is connected to the first conversion circuit and the second conversion circuit, and an output side of the second filter circuit is connected to the neutral point; and a control circuit is configured to generate a plurality of control signals and respectively control The first conversion circuit and the second conversion circuit reduce leakage current caused by a parasitic capacitance effect of the DC input voltage. [Item 2] The dual-drop DC-to-AC conversion system of claim 1, wherein the first conversion circuit comprises:
a first power switch includes a first end and a second end; the first end of the first power switch is connected to the first capacitor;
a first auxiliary power switch includes a first end and a second end; the first end of the first auxiliary power switch is connected to the second end of the first power switch;
a second auxiliary power switch includes a first end and a second end; the first end of the second auxiliary power switch is connected to the second end of the first power switch;
a first diode comprising an anode and a cathode; the cathode of the first diode is connected to the second end of the first auxiliary power switch; and a second diode comprising an anode And the cathode of the second diode is connected to the second end of the second auxiliary power switch; the anode of the first diode is connected to the anode of the second diode Two capacitors. [Item 3] The dual-drop DC-to-AC conversion system of claim 2, wherein the second conversion circuit comprises:
a second power switch includes a first end and a second end; the first end of the second power switch is coupled to the second capacitor;
a third auxiliary power switch includes a first end and a second end; the first end of the third auxiliary power switch is connected to the second end of the second power switch;
a fourth auxiliary power switch includes a first end and a second end; the first end of the fourth auxiliary power switch is connected to the second end of the second power switch;
a third diode comprising an anode and a cathode; the anode of the third diode is connected to the second end of the third auxiliary power switch; and a fourth diode comprising an anode And a cathode; the anode of the fourth diode is connected to the second end of the fourth auxiliary power switch; the cathode of the third diode is connected to the cathode of the fourth diode A capacitor. [Item 4] The dual-drop DC-to-AC conversion system of claim 3, wherein the first filter circuit comprises a first output inductor, a second output inductor, and a first output capacitor; the first output inductor One end is connected to one end of the second output inductor, and is connected to one end of the first output capacitor; the other end of the first output inductor is connected to the second end of the first auxiliary power switch, the second output inductor The other end is connected to the second end of the fourth auxiliary power switch, and the other end of the first output capacitor is connected to the neutral point; the second filter circuit includes a third output inductor and a fourth output. An inductor and a second output capacitor; one end of the third output inductor is connected to one end of the fourth output inductor, and is connected to one end of the second output capacitor; the other end of the third output inductor is connected to the second auxiliary The second end of the power switch is connected to the second end of the third auxiliary power switch, and the other end of the second output capacitor is connected to the neutral point. [Item 5] The dual-drop DC-to-AC conversion system of claim 4, wherein the control circuit comprises:
a signal absolute value unit receives an alternating voltage signal to convert the alternating voltage signal into a positive voltage signal;
a first comparison unit having an inverting input, a non-inverting input, and a first output; the non-inverting input receiving the positive voltage signal, the inverting input receiving a triangular carrier a signal; the first output terminal outputs an output control signal; wherein the triangular carrier signal is a high frequency carrier signal;
a second comparison unit having an inverting input terminal, a non-inverting input terminal, and a second output terminal; the non-inverting input terminal receiving the AC voltage signal, the inverting input terminal being grounded; the second The output terminal outputs a first auxiliary output control signal; and an inverting unit receives the first auxiliary output control signal to invert the first auxiliary output control signal to be a second auxiliary output control signal. [Item 6] The dual-drop DC-to-AC conversion system according to claim 5, wherein when the AC output voltage is positive half cycle, the output control signal is a high frequency switching signal, and the first auxiliary output control signal is a low frequency high level signal and the second auxiliary output control signal are a low frequency low level signal; wherein when the AC output voltage is negative half cycle, the output control signal is a high frequency switching signal, the first auxiliary output The control signal is a low frequency low level signal and the second auxiliary output control signal is a low frequency high level signal. [Item 7] The dual-drop DC-to-AC conversion system according to claim 6, wherein the output control signal is high-frequency switched to turn on the first power switch and the second power switch when the AC output voltage is a positive half cycle operation. The first auxiliary output control signal low frequency high level turns on the first auxiliary power switch and the third auxiliary power switch, and the second auxiliary output control signal low frequency low level turns off the second auxiliary power switch and the fourth In the auxiliary power switch, the first output inductor and the fourth output inductor are energy storage operations. At this time, the dual-drop DC-to-AC conversion system provides a positive half-cycle energy storage circuit sequentially for the DC input voltage. The first power switch, the first auxiliary power switch, the first output inductor, the AC output voltage, the fourth output inductor, the third auxiliary power switch, and the second power switch are formed. [Item 8] The dual-drop DC-to-AC conversion system according to claim 6, wherein when the AC output voltage is a positive half cycle operation, the output control signal is switched to cut off the first power switch and the second power switch. The first auxiliary output control signal low frequency high level turns on the first auxiliary power switch and the third auxiliary power switch, and the second auxiliary output control signal low frequency low level turns off the second auxiliary power switch and the fourth When the auxiliary power switch is used, the first output inductor and the fourth output inductor are discharged. In this case, the dual-drop DC-to-AC conversion system provides a positive half-cycle release circuit in sequence as the first output inductor. The AC output voltage, the fourth output inductor, the third auxiliary power switch, the freewheeling diode, and the first auxiliary power switch are formed. [Item 9] The dual-drop DC-to-AC conversion system according to claim 6, wherein the output control signal is high-frequency switched to turn on the first power switch and the second power switch when the AC output voltage is a negative half cycle operation. The first auxiliary output control signal low frequency low level turns off the first auxiliary power switch and the third auxiliary power switch, and the second auxiliary output control signal low frequency high level turns on the second auxiliary power switch and the fourth When the auxiliary power switch is used, the second output inductor and the third output inductor are energy storage operations. At this time, the dual-drop DC-to-AC conversion system provides a negative half-cycle energy storage circuit sequentially for the DC input voltage. The first power switch, the second auxiliary power switch, the third output inductor, the AC output voltage, the second output inductor, the fourth auxiliary power switch, and the second power switch are formed. [Item 10] The dual-drop DC-to-AC conversion system according to claim 6, wherein when the AC output voltage is a negative half cycle operation, the output control signal is switched to cut off the first power switch and the second power switch. The first auxiliary output control signal low frequency low level turns off the first auxiliary power switch and the third auxiliary power switch, and the second auxiliary output control signal low frequency high level turns on the second auxiliary power switch and the fourth When the auxiliary power switch is used, the second output inductor and the third output inductor are discharged. In this case, the dual-drop DC-to-AC conversion system provides a negative half-cycle release circuit sequentially for the third output inductor. The AC output voltage, the first output inductor, the fourth auxiliary power switch, the freewheeling diode, and the second auxiliary power switch are formed. [Item 11] The operating method of a dual-drop DC-to-AC conversion system is to convert a DC input voltage into an AC output voltage, and the operation method comprises the following steps:
(a) providing an input capacitor set, receiving the DC input voltage, the input capacitor set includes a first capacitor and a second capacitor, the first capacitor and the second capacitor are connected to a neutral point;
(b) providing a first conversion circuit and a second conversion circuit, respectively connecting the input capacitance group in parallel;
(c) providing a freewheeling diode connected to the first conversion circuit and the second conversion circuit;
(d) providing a first filter circuit connecting the first conversion circuit and the second conversion circuit, and an output side of the first filter circuit is connected to the neutral point;
(e) providing a second filter circuit connecting the first conversion circuit and the second conversion circuit, and an output side of the second filter circuit is connected to the neutral point;
(f) providing a control circuit for generating a plurality of control signals for respectively controlling the first conversion circuit and the second conversion circuit to reduce leakage current caused by a parasitic capacitance effect of the DC input voltage. [Item 12] The method for operating a dual-drop DC-to-AC conversion system according to claim 11, wherein the first conversion circuit comprises:
a first power switch includes a first end and a second end; the first end of the first power switch is connected to the first capacitor;
a first auxiliary power switch includes a first end and a second end; the first end of the first auxiliary power switch is connected to the second end of the first power switch;
a second auxiliary power switch includes a first end and a second end; the first end of the second auxiliary power switch is connected to the second end of the first power switch;
a first diode comprising an anode and a cathode; the cathode of the first diode is connected to the second end of the first auxiliary power switch; and a second diode comprising an anode And the cathode of the second diode is connected to the second end of the second auxiliary power switch; the anode of the first diode is connected to the anode of the second diode Two capacitors. [Item 13] The operating method of the dual-drop DC-to-AC conversion system according to claim 12, wherein the second conversion circuit comprises:
a second power switch includes a first end and a second end; the first end of the second power switch is coupled to the second capacitor;
a third auxiliary power switch includes a first end and a second end; the first end of the third auxiliary power switch is connected to the second end of the second power switch;
a fourth auxiliary power switch includes a first end and a second end; the first end of the fourth auxiliary power switch is connected to the second end of the second power switch;
a third diode comprising an anode and a cathode; the anode of the third diode is connected to the second end of the third auxiliary power switch; and a fourth diode comprising an anode And a cathode; the anode of the fourth diode is connected to the second end of the fourth auxiliary power switch; the cathode of the third diode is connected to the cathode of the fourth diode A capacitor. [Item 14] The method of operating the dual-drop DC-to-AC conversion system of claim 13, wherein the first filter circuit comprises a first output inductor, a second output inductor, and a first output capacitor; One end of the output inductor is connected to one end of the second output inductor, and is connected to one end of the first output capacitor; the other end of the first output inductor is connected to the second end of the first auxiliary power switch, the second The other end of the output inductor is connected to the second end of the fourth auxiliary power switch, and the other end of the first output capacitor is connected to the neutral point; the second filter circuit includes a third output inductor, a first a fourth output inductor and a second output capacitor; one end of the third output inductor is connected to one end of the fourth output inductor, and is connected to one end of the second output capacitor; the other end of the third output inductor is connected to the first The second end of the auxiliary power switch, the other end of the fourth output inductor is connected to the second end of the third auxiliary power switch, and the other end of the second output capacitor is connected Neutral point. [Item 15] The method for operating a dual-drop DC-to-AC conversion system according to claim 14, wherein the control circuit comprises:
a signal absolute value unit receives an alternating voltage signal to convert the alternating voltage signal into a positive voltage signal;
a first comparison unit having an inverting input, a non-inverting input, and a first output; the non-inverting input receiving the positive voltage signal, the inverting input receiving a triangular carrier a signal; the first output terminal outputs an output control signal; wherein the triangular carrier signal is a high frequency carrier signal;
a second comparison unit having an inverting input terminal, a non-inverting input terminal, and a second output terminal; the non-inverting input terminal receiving the AC voltage signal, the inverting input terminal being grounded; the second The output terminal outputs a first auxiliary output control signal; and an inverting unit receives the first auxiliary output control signal to invert the first auxiliary output control signal to be a second auxiliary output control signal. [Item 16] The operating method of the dual-drop DC-to-AC conversion system according to claim 15 , wherein when the AC output voltage is positive half cycle, the output control signal is a high frequency switching signal, and the first auxiliary output control The signal is a low frequency high level signal and the second auxiliary output control signal is a low frequency low level signal; wherein when the AC output voltage is negative half cycle, the output control signal is a high frequency switching signal, the first The auxiliary output control signal is a low frequency low level signal and the second auxiliary output control signal is a low frequency high level signal. [Item 17] The operating method of the dual-drop DC-to-AC conversion system according to claim 16, wherein the output control signal is high-frequency switched to turn on the first power switch and the second when the AC output voltage is a positive half cycle operation. a power switch, the first auxiliary output control signal low frequency high level turns on the first auxiliary power switch and the third auxiliary power switch, and the second auxiliary output control signal low frequency low level turns off the second auxiliary power switch In the fourth auxiliary power switch, the first output inductor and the fourth output inductor are energy storage operations. At this time, the dual-drop DC-to-AC conversion system provides a positive half-cycle energy storage circuit sequentially as the DC input. The voltage, the first power switch, the first auxiliary power switch, the first output inductor, the AC output voltage, the fourth output inductor, the third auxiliary power switch, and the second power switch are formed. [Item 18] The operating method of the dual-drop DC-to-AC conversion system according to claim 16 , wherein when the AC output voltage is a positive half cycle operation, the output control signal is switched to cut off the first power switch and the second a power switch, the first auxiliary output control signal low frequency high level turns on the first auxiliary power switch and the third auxiliary power switch, and the second auxiliary output control signal low frequency low level turns off the second auxiliary power switch In the fourth auxiliary power switch, the first output inductor and the fourth output inductor are in a release operation. At this time, the dual-drop DC-to-AC conversion system provides a positive half-cycle release circuit in order to be the first The output inductor, the AC output voltage, the fourth output inductor, the third auxiliary power switch, the freewheeling diode, and the first auxiliary power switch are formed. [Item 19] The operating method of the dual-drop DC-to-AC conversion system according to claim 16, wherein the output control signal is high-frequency switched to turn on the first power switch and the second when the AC output voltage is a negative half cycle operation a power switch, the first auxiliary output control signal low frequency low level turns off the first auxiliary power switch and the third auxiliary power switch, and the second auxiliary output control signal low frequency high level turns on the second auxiliary power switch and the In the fourth auxiliary power switch, the second output inductor and the third output inductor are energy storage operations. At this time, the dual-drop DC-to-AC conversion system provides a negative half-cycle energy storage circuit for the DC input. The voltage, the first power switch, the second auxiliary power switch, the third output inductor, the AC output voltage, the second output inductor, the fourth auxiliary power switch, and the second power switch are formed. [Item 20] The operating method of the dual-drop DC-to-AC conversion system according to claim 16, wherein the output control signal is switched to cut off the first power switch and the second when the AC output voltage is negative half-cycle operation. a power switch, the first auxiliary output control signal low frequency low level turns off the first auxiliary power switch and the third auxiliary power switch, and the second auxiliary output control signal low frequency high level turns on the second auxiliary power switch and the In the fourth auxiliary power switch, the second output inductor and the third output inductor are in a release operation. At this time, the double-drop DC-to-AC conversion system provides a negative half-cycle release circuit in sequence. The output inductor, the AC output voltage, the first output inductor, the fourth auxiliary power switch, the freewheeling diode, and the second auxiliary power switch are formed.