High power factor soft switching Vienna rectifier circuit and control method

Abstract

The present invention relates to a high power factor soft switch Vienna rectifier circuit, comprising a first rectifier diode D1, a second rectifier diode D2, a first DC link capacitor C01, a second DC link capacitor C01, a first main switch S1 and a second main switch S2, the rectifier circuit also comprises two active buffer circuits respectively arranged in the loop where the first rectifier diode D1 and the second rectifier diode D2 are located, each active buffer circuit is composed of a blocking diode, a buffer inductor, an auxiliary switch, a transformer and a resistor-capacitor diode clamping circuit. Compared with the prior art, the present invention has the advantages of reducing reverse recovery loss, avoiding ringing problems, realizing zero voltage switching of Vienna switches and zero current switching of auxiliary circuit switches, etc.

Description

Technical Field

[0001] The invention relates to the technical field of circuit topology, and in particular to a high power factor soft switch Vienna rectifier circuit and a control method. Background Art

[0002] In the prior art, circuit topologies employ active and passive snubber circuits to produce soft switching conditions for semiconductor devices and rectifier diodes. These snubber circuits are used to limit the rate of change of diode current and create soft switching conditions for the semiconductor components of the circuit.

[0003] The converter circuit using active snubber circuit proposed in the existing literature Halder, "An Improved Soft Switched Boost Power Converter Suitable for Power Factor Correction", Power Electronics (IICPE) 2018 8th IEEE India International Conference on, pp. 1-6, 2018, has the function of reducing current and voltage stress in addition to the soft switching of switch conduction and rectifier circuit shutdown. However, the auxiliary switch of the active snubber circuit has a higher current stress and works under hard switching conditions. The literature MM Jovanovic, "A technique for reducing rectifier reverse-recovery-related losses in high-voltage, high-power boost converters," in Proc. IEEE In the boost topology described in APEC'97, Mar.1997, pp.1000–1007, both the main switch and the auxiliary switch operate under soft switching conditions. However, the voltage stress of the main switch is higher than that in the above-mentioned converter circuit using an active snubber circuit, which needs to be controlled by properly selecting the snubber inductance value and the switching frequency, and the gate drive circuit requirements are complex and expensive. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a high power factor soft switching Vienna rectifier circuit and control method.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A high power factor soft switch Vienna rectifier circuit includes a first rectifier diode D1, a second rectifier diode D2, a first DC link capacitor C01, a second DC link capacitor C01, a first main switch S1 and a second main switch S2. The rectifier circuit also includes two active buffer circuits respectively arranged in the loop where the first rectifier diode D1 and the second rectifier diode D2 are located. Each active buffer circuit is composed of a blocking diode, a buffer inductor, an auxiliary switch, a transformer and a resistor-capacitor diode clamping circuit.

[0007] The active snubber circuit in the loop where the first rectifier diode D1 is located specifically includes a first blocking diode Ds1, a first snubber inductor Ls1, a transformer, a first auxiliary switch Ss1 and a first resistor-capacitor diode clamping circuit. The positive electrode of the first blocking diode Ds1 is connected between the input end and the first main switch S1, the negative electrode of the first blocking diode Ds1 is grounded after passing through the first snubber inductor Ls1, the primary winding of the transformer and the first auxiliary switch Ss1, and the first resistor-capacitor diode clamping circuit is connected to the secondary winding of the transformer.

[0008] The first RC diode clamping circuit is composed of a first clamping resistor R1, a first clamping capacitor C1, a second diode Ds2 and a third diode Ds3. The first clamping resistor R1 and the first clamping capacitor C1 are connected in parallel. The positive electrode of the third diode Ds3 is connected to the secondary winding of the transformer, and the negative electrode is respectively connected to the first clamping resistor R1 and the first clamping capacitor C1, and is connected to the negative electrode of the first rectifier diode D1 through the second diode Ds2.

[0009] The first main switch S1 and the second main switch S2 are MOSFET tubes.

[0010] The first auxiliary switch Ss1 is a MOSFET tube.

[0011] The turns ratio n of the transformer is less than 1.

[0012] The turns ratio n of the transformer is less than 0.5, so as to ensure that the output capacitor of the first main switch S1 is fully discharged.

[0013] A control method for a high power factor soft-switching Vienna rectifier circuit, during the positive half cycle of the line voltage, the first main switch S1 and the first auxiliary switch Ss1 have overlapping gate signals during the on-time, the first auxiliary switch Ss1 is turned off before the first main switch S1 is turned off, when the first main switch S1 and the first auxiliary switch Ss1 are turned off, the input current Ii flows into the load RL through the first rectifier diode D1, when the first auxiliary switch Ss1 is turned on, the input current Ii starts to flow through the first blocking diode Ds1, the first snubber inductor Ls1, the primary winding of the transformer, the first auxiliary switch Ss1 and returns to the power supply, the current flowing through the first snubber inductor has a slope If the linear increase is:

[0014]

[0015] Among them, V 01 is the voltage of the transformer secondary winding, n is the turns ratio of the transformer, L s1 is the first buffer inductance value.

[0016] During the positive half cycle of the line voltage, the current i of the first snubber inductor is Ls1 The first rectifier diode current i D1 The sum is always equal to the input current Ii, the increase rate of the current in the first buffer inductor is equal to the decrease rate of the current in the first rectifier diode, then the current turn-off change rate of the first rectifier diode D1 is:

[0017]

[0018] The turn-off change rate of the first rectifier diode current is controlled by adjusting the transformer turns ratio n and the value of the first snubber inductor Ls1.

[0019] During the positive half cycle of the line voltage, when the current in the first rectifier diode reaches zero, the current in the first buffer inductor reaches the input current value. Due to the residual charge, the current of the first rectifier diode continues to flow in the reverse direction. When the residual charge is completely removed, the first rectifier diode recovers the ability to block the voltage. After the output capacitor of the first main switch S1 is discharged, the anti-parallel diode of the main switch S1 starts to conduct. The first main switch S1 can be turned on at zero voltage. The current in the first auxiliary switch Ss1 also decreases linearly. The current in the first main switch S1 increases linearly from the negative current peak. The first main switch S1 is turned on at the same time as the anti-parallel diode of the first main switch S1 is turned on, realizing zero voltage switching ZVS switching of the first main switch S1. The current of the first buffer inductor continues to decrease linearly at the same rate as the current in the first main switch S1 continues to increase. When the current of the first buffer inductor is zero, the current of the first main switch S1 reaches the input current Ii, that is, the input current completely flows through the first main switch S1.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] In the present invention, the buffer inductor of the auxiliary switch controls the current I D The reverse recovery loss of the rectifier diode is reduced by reducing the rate of change of the voltage. In addition, the energy stored in the snubber inductor is used to discharge the output capacitor to zero before the main switch is turned on, thereby generating zero capacitance conduction switching loss. When the main switch is turned off, the auxiliary switch and capacitor of the active snubber circuit provide a discharge path for the remaining energy stored in the snubber inductor. This circuit topology effectively solves the ringing problem caused by the interaction between the rectifier diode junction capacitance and the snubber inductor, and realizes the zero voltage switching (ZVS) of the Vienna switch and the zero current switching (ZCS) of the auxiliary circuit switch. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a circuit structure diagram of a high power factor soft switching Vienna rectifier circuit.

[0023] Figure 2 This is a simplified circuit diagram of a high power factor soft switching Vienna rectifier circuit.

[0024] Figure 3 It is a topological circuit diagram of each stage during the positive half cycle of the online voltage of the present invention, wherein Figure (3a) is the first stage, Figure (3b) is the second stage, Figure (3c) is the third stage, Figure (3d) is the fourth stage, Figure (3e) is the fifth stage, Figure (3f) is the sixth stage, Figure (3g) is the seventh stage, Figure (3h) is the eighth stage, Figure (3i) is the ninth stage, Figure (3j) is the tenth stage, and Figure (3k) is the eleventh stage.

[0025] Figure 4 It is a key theoretical waveform diagram of the present invention in the positive half-line cycle. DETAILED DESCRIPTION

[0026] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] Example

[0028] like Figure 1 As shown, Figure 1 The circuit diagram of the soft-switching Vienna rectifier circuit with an active snubber circuit is shown in Figure 1. The characteristics of the circuit are the soft switching of the semiconductor device and the controllable current I of the rectifier diode. D Therefore, the switching losses, which are beneficial to the converter efficiency, are greatly reduced.

[0029] The circuit is powered by an AC power supply voltage V i(t), line inductance L, main switches S1 and S2, rectifier diodes D1 and D2, DC link capacitors C01 and C02 and two active snubber circuits, each of which is composed of a blocking diode Ds, a snubber inductor Ls, an auxiliary switch Ss1, a transformer and a RC diode clamping circuit. In order to simplify the circuit operation, the output DC link capacitor and the clamping circuit capacitor are replaced by DC voltage sources V01, V02 and Vc1, Vc2 respectively, assuming that their capacitance values ​​are large enough, so the voltage fluctuation between them can be ignored. In addition, the line inductor is replaced by the input current Ii of the constant current source, because it is large enough and the current flowing through it does not change significantly during the switching interval. In addition, the transformer model is modeled by the ideal transformer of magnetizing inductance LM1 and LM2 and n=N1 / N2. The leakage inductance of each transformer is lumped together with the corresponding snubber inductance and is not shown separately. The on-resistance of the semiconductor element is assumed to be zero, while the output capacitance and reverse recovery charge of the rectifier diode are not ignored in the analysis. The simplified circuit diagram of the soft-switching Vienna rectifier circuit proposed by the present invention is as follows Figure 2 shown.

[0030] like Figure 4 As shown, the main switch S1 and the auxiliary switch Ss1 have overlapping gate signals during the on-time, and SS1 is turned off before S1 is turned off. When the main switch S1 and the auxiliary switch Ss1 are turned off, the input current Ii flows into the load RL through the rectifier diode D1. When the auxiliary switch Ss1 is turned on, the input current Ii begins to flow through the blocking diode Ds1, the snubber inductor Ls1, the transformer primary winding, the auxiliary switch Ss1 and returns to the power supply. Due to the working principle of the transformer, current is also generated in the secondary winding of the transformer. The voltage through the secondary winding is V01, which causes the voltage of the primary winding to be equal to n*V01, where n is the turns ratio of the transformer, then:

[0031]

[0032] Among them, N1 is the number of turns on the primary side of the transformer, and N2 is the number of turns on the secondary side of the transformer.

[0033] The current flowing through the snubber inductor has a slope The linear increase leads to:

[0034]

[0035] Since the current i Ls1 and the rectifier diode current i D1 The sum is always equal to the input current Ii, and the rate at which the buffer inductor current increases is equal to the rate at which the current in the rectifier diode D1 decreases. Therefore, the turn-off current rate of the rectifier diode D1 is as follows:

[0036]

[0037] Formula (3) shows that by selecting the value of the turns ratio n and the snubber inductor Ls1, the turn-off change rate of the rectifier diode current can be controlled. When the current in the rectifier diode reaches zero, the current in the snubber inductor reaches the source current value Ii. Due to the residual charge, the rectifier diode current continues to flow in the reverse direction. By selecting the snubber inductor Ls1 and the turns ratio n, the negative flow of the current can be effectively controlled. When the residual charge is completely removed, the rectifier diode restores the ability to block the voltage. After the residual charge is removed, the junction capacitance CD1 of the rectifier diode and the output capacitance of the main switch S1 form a series resonant circuit with the snubber inductor Ls1, generating parasitic ringing and possibly causing the voltage stress of the rectifier diode to increase. This ringing effect is usually suppressed by an RC snubber applied to the rectifier diode. For the zero voltage switch ZVS turn-on of S1, the output capacitance of the main switch S1 must be discharged, thus limiting the maximum value of the transformer turns ratio:

[0038]

[0039] If n<0.5, the output capacitor of the main switch S1 can always be fully discharged regardless of the line and load conditions. After the output capacitor of the main switch S1 is discharged, the anti-parallel diode of the main switch S1 begins to conduct, so the main switch S1 can be turned on at zero voltage. Since the voltage on the snubber inductor Ls1 is –nV01, its current decreases at a rate given by equation (5):

[0040]

[0041] Therefore, the current in the auxiliary switch Ss1 also decreases linearly, while the current in the switch S1 increases linearly from the negative current peak. To use the zero voltage switch ZVS switch main switch S1, the main switch S1 must be turned on while its anti-parallel diode is conducting. The snubber inductor current continues to decrease linearly at the same rate as the current in the main switch S1 continues to increase. When the snubber inductor current is zero, the current of the main switch S1 reaches Ii, that is, the source current completely flows through the main switch S1. At this time, the auxiliary switch ss1 carries the magnetizing current i of the transformer M1 If the magnetizing inductance LM1 of the transformer is increased, this current can be significantly reduced. Therefore, the auxiliary switch Ss1 can be turned off at a current close to zero. After the auxiliary switch Ss1 is turned off, the magnetizing current i M1The output capacitor of the auxiliary switch Ss1 is charged, increasing its voltage. When its voltage reaches V01+Vc1, where Vc1 is the voltage across the clamp capacitor C1, the magnetizing current is commutated through the diode Ds3 to the voltage source Vc1, which simulates the clamping circuit. Due to the reverse voltage polarity of the voltage source Vc1, the magnetizing current is reset by the voltage source Vc1, and its rate is given by formula (6):

[0042]

[0043] Until the magnetizing current i M1 =0, the transformer will reset, and the input current Ii will flow into the main switch S1 until its gate voltage is removed. Then, the voltage of the main switch S1 begins to increase because the constant source current charges the output capacitor of the main switch S1 until it reaches V01. The rectifier diode D1 immediately starts the input current Ii, causing the voltage through the main switch S1 to reach V01. Unless the auxiliary switch Ss1 is turned on, the input current Ii flows through the rectifier diode D1. It is worth noting that the junction capacitance of the blocking diode Ds1 and the absorption inductor Ls1 resonate after the current flowing through Ls1 drops to zero. This resonance causes a small amount of current to flow in the reverse direction through the auxiliary switch Ss1 and through its anti-parallel diode. Therefore, the auxiliary switch Ss1 cannot be turned off immediately after the current drops to zero. In other words, unless the current through its anti-parallel diode drops to zero, the increase in its voltage will be delayed for a short time. The impact of this delay is usually ignored because it does not cause the performance of the circuit to deteriorate.

[0044] In summary, the soft-switching Vienna rectifier circuit of the present invention generates ZVS conduction of the main switch S1, ZCS turn-off of the auxiliary switch Ss1, and controlled turn-off diD1 / dt rate of the rectifier diode current, thereby reducing the overall switching loss of the rectifier circuit and improving the conversion efficiency. Figure 1 The main switch S1 in the circuit is recommended to be implemented with MOSFET. Due to the ZCS shutdown of the auxiliary switch Ss1, Figure 1 The circuit in is best implemented with an IGBT auxiliary switch. The reason for this is that the switching losses of the IGBT are mainly determined by the turn-off losses due to the current tailing effect. The turn-on switching losses of the IGBT are much smaller than those of the MOSFET due to its output capacitance value.

Claims

1. A high power factor soft switch Vienna rectifier circuit, comprising a first rectifier diode D1, a second rectifier diode D2, a first DC link capacitor C01, a second DC link capacitor C01, a first main switch S1 and a second main switch S2, characterized in that: The rectifier circuit also includes two active buffer circuits respectively arranged in the loops where the first rectifier diode D1 and the second rectifier diode D2 are located, each active buffer circuit is composed of a blocking diode, a buffer inductor, an auxiliary switch, a transformer and a resistor-capacitor diode clamping circuit; The active snubber circuit in the loop where the first rectifier diode D1 is located specifically includes a first blocking diode Ds1, a first snubber inductor Ls1, a transformer, a first auxiliary switch Ss1 and a first resistor-capacitor diode clamping circuit, wherein the anode of the first blocking diode Ds1 is connected between the input terminal and the first main switch S1, the cathode of the first blocking diode Ds1 is grounded after passing through the first snubber inductor Ls1, the primary winding of the transformer and the first auxiliary switch Ss1, and the first resistor-capacitor diode clamping circuit is connected to the secondary winding of the transformer; The first RC diode clamp circuit is composed of a first clamp resistor R1, a first clamp capacitor C1, a second diode Ds2 and a third diode Ds3. The first clamp resistor R1 and the first clamp capacitor C1 are connected in parallel. The positive electrode of the third diode Ds3 is connected to the secondary winding of the transformer, and the negative electrode is connected to the first clamp resistor R1 and the first clamp capacitor C1 respectively, and is connected to the negative electrode of the first rectifier diode D1 through the second diode Ds2. The first main switch S1 and the second main switch S2 are MOSFET tubes.

2. A high power factor soft switch Vienna rectifier circuit according to claim 1, characterized in that: The first auxiliary switch Ss1 is a MOSFET tube.

3. The high power factor soft switch Vienna rectifier circuit according to claim 1, characterized in that: The turns ratio of the transformer n Less than 1.

4. A high power factor soft switch Vienna rectifier circuit according to claim 3, characterized in that: The turns ratio of the transformer n< 0.5, to ensure that the output capacitor of the first main switch S1 is fully discharged.

5. A control method for a high power factor soft-switching Vienna rectifier circuit according to any one of claims 1 to 4, characterized in that: During the positive half cycle of the line voltage, the first main switch S1 and the first auxiliary switch Ss1 have overlapping gate signals during the on-time. The first auxiliary switch Ss1 is turned off before the first main switch S1 is turned off. When the first main switch S1 and the first auxiliary switch Ss1 are turned off, the input current Ii flows into the load RL through the first rectifier diode D1. When the first auxiliary switch Ss1 is turned on, the input current Ii begins to flow through the first blocking diode Ds1, the first snubber inductor Ls1, the primary winding of the transformer, the first auxiliary switch Ss1 and returns to the power supply. The current flowing through the first snubber inductor has a slope of If the linear increase is: in, is the voltage of the transformer secondary winding, n is the turns ratio of the transformer, is the first buffer inductance value.

6. The control method of a high power factor soft switch Vienna rectifier circuit according to claim 5, characterized in that: During the positive half cycle of the line voltage, the current i of the first snubber inductor is Ls1 The first rectifier diode current i D1 The sum is always equal to the input current Ii, the increase rate of the current in the first buffer inductor is equal to the decrease rate of the current in the first rectifier diode, then the current turn-off change rate of the first rectifier diode D1 is: The turn-off change rate of the first rectifier diode current is controlled by adjusting the transformer turns ratio n and the value of the first snubber inductor Ls1.

7. The control method of a high power factor soft switch Vienna rectifier circuit according to claim 6, characterized in that: During the positive half cycle of the line voltage, when the current in the first rectifier diode reaches zero, the current in the first buffer inductor reaches the input current value. Due to the residual charge, the current of the first rectifier diode continues to flow in the reverse direction. When the residual charge is completely removed, the first rectifier diode recovers the ability to block the voltage. After the output capacitor of the first main switch S1 is discharged, the anti-parallel diode of the first main switch S1 starts to conduct. The first main switch S1 can be turned on at zero voltage. The current in the first auxiliary switch Ss1 also decreases linearly. The current in the first main switch S1 increases linearly from the negative current peak. The first main switch S1 is turned on at the same time as the anti-parallel diode of the first main switch S1 is turned on, realizing zero voltage switching ZVS switching of the first main switch S1. The current of the first buffer inductor continues to decrease linearly at the same rate as the current in the first main switch S1 continues to increase. When the current of the first buffer inductor is zero, the current of the first main switch S1 reaches the input current Ii, that is, the input current completely flows through the first main switch S1.

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