rectifier circuit

Abstract

To provide a rectifying circuit that can be used with a simpler configuration and in which a variable reactor function and a rectifying function are integrated.SOLUTION: One end of LC resonance circuits 12a and 12b is connected to each of input terminals 11a and 11b to which AC power is input, respectively. A series circuit of switches S1 and S2 is connected between the other end of the LC resonance circuits 12a and 12b. Diodes D1 and D2 are connected in parallel to the switches S1 and S2, respectively, so as to have a common cathode. Capacitors C1 and C2 are connected in parallel to the diodes D1 and D2, respectively. A filter circuit 15 includes a series circuit of inductors 13a and 13b connected in parallel to a series circuit of the switches S1 and S2, and an output capacitor 15 connected between DC output terminals. A gate control circuit 5 variably controls reactance by switching the switches S1 and S2 at 180-degree phase difference.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a circuit for rectifying alternating current power into direct current power.

Background Art

[0002] In a non-contact power supply (WPT: Wireless Power Transfer) system used in an electric field coupling type, a magnetic field coupling type, etc., in order to improve the power transmission efficiency or suppress the power reflection, a matching circuit that cancels the reactance component on the power transmission path or performs impedance matching, or a resonance circuit that resonates with the LC value of the coupler and the alternating current power supply frequency is provided.

[0003] The resonance frequency of the coupler and the reactance component on the power transmission path may vary due to dimensional changes over time of the coupler or the movement of the power receiving side. If the matching circuit and the resonance circuit are composed of LC elements with fixed constants, there is concern that they cannot cope with the generated reactance component, power reflection will occur, and the power transmission performance will deteriorate.

[0004] To address such problems, there is a method of inserting a variable reactor circuit and automatically adjusting the reactor value to cancel the influence. The variable reactor circuit has a mechanical or electronic configuration composed of a switching element and an LC component. However, in that case, there is concern about an increase in the circuit size. In particular, the power receiving side circuit is often restricted in size and weight due to the assumption of being mounted on a moving body, an aircraft, etc., and miniaturization is required. Therefore, in order to achieve both power transmission performance and miniaturization of the power receiving side circuit, a circuit integrating a variable reactor circuit and a rectifier circuit has been proposed.

[0005] Non-patent document 1 discloses a rectifier circuit comprising an LC resonant circuit that adds a +jX or -jX component, two rectifier sections composed of two switches and a capacitor, and DC-DC converters connected to each of these rectifier sections. In this configuration, the input resistance of the converters, and thus the rectifier sections, is controlled by controlling the voltage conversion ratio of each DC-DC converter. This controls the impedance Zr by controlling the contributions of +jX and -jX, thereby canceling the reactance on the power transmission path. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] IEEE JOURNAL OF EMERGING AND SELECTED TOPICS IN POWER ELECTRONICS, VOL.8,NO.3,SEPTEMBER 2020 [Overview of the project] [Problems that the invention aims to solve]

[0007] The above configuration requires two sets of LC series circuits, rectifiers, and converters, which raises concerns about increased circuit size. The present invention has been made in view of the above circumstances, and its purpose is to provide a rectifier circuit that integrates a variable reactor function and a rectifier function and can be used with a simpler configuration. [Means for solving the problem]

[0008] According to the rectifier circuit of claim 1, one end of each of the two LC resonant circuits (12a, 12b) is connected to each of the two input terminals (11a, 11b) to which AC power is input. Between the other ends of the two LC resonant circuits, a series circuit of first and second switching elements (S1, S2) connected in opposite directions is connected. First and second diodes (D1, D2) are connected in parallel to each of the first and second switching elements, and their cathodes or anodes are common. First and second capacitors (C1, C2) are connected in parallel to the first and second diodes, respectively. The filter circuit (15) has a series circuit of two inductors (13a, 13b) connected in parallel to the series circuit of the first and second switching elements, and an output capacitor (14) connected between the DC output terminals. The control unit (5) performs variable reactance control by switching the first and second switching elements with a phase difference of 180 degrees from each other.

[0009] If the reactance variably controlled by the control unit is -jXrec, the magnitude of its absolute value can be adjusted by the capacitance C of the first and second capacitors. The capacitance C of the first and second capacitors is set such that ΔX ≤ (maximum value of |jXrec|), where ΔX is the required variable control value for the reactance. The sum of the reactances jX of the two LC resonant circuits shifts the reactance jXr as seen from the input terminal to the positive side, making the variable range of the reactance jXr bipolar. The control unit turns on the first and second switching elements after the corresponding diode is turned on, and turns off the switching elements after a predetermined time has elapsed after the diode is turned off, thereby performing variable control of the reactance based on the off-duty cycle.

[0010] With this configuration, only one DC-DC converter needs to be connected to the output capacitor, and the reactance jXr can be variably controlled in both polarity by the rectifier circuit. Therefore, the circuit size can be reduced compared to conventional configurations.

[0011] According to the rectifier circuit described in claim 2, the series circuit of the LC resonant circuit (12) and the switching element (S1) is connected between the input terminals (11a, 11b) to which AC power is input. The diode (D1) is connected in parallel with the switching element, with its cathode facing the LC resonant circuit side, and the capacitor (C1) is connected in parallel with the diode. The filter circuit (52) having an inductor (13) and an output capacitor (14) is connected in parallel with the switching element. The control unit (5) performs variable control of the reactance by switching the switching element. The capacitance C of the capacitor connected in parallel with the diode is set such that ΔX≦(maximum value of |jXrec|) is satisfied when the variable control value required for the reactance is ΔX and the reactance variably controlled by the control unit is -jXrec. The reactance jX of the LC resonant circuit shifts the reactance jXr as seen from the input terminal to the positive side, making the variable range of the reactance jXr bipolar.

[0012] The control unit turns on the switching element after the diode is turned on, and turns off the switching element after a predetermined time has elapsed after the diode is turned off, thereby performing variable control of the reactance based on the off-duty cycle. Even with this configuration, the reactance jXr can be variably controlled in both polarities by the rectifier circuit. Therefore, the circuit size can be reduced compared to the conventional configuration. [Brief explanation of the drawing]

[0013] [Figure 1] This is a diagram showing the configuration of a power supply system, representing the first embodiment. [Figure 2] Diagram showing the configuration of a variable reactor rectifier circuit. [Figure 3] A diagram showing the change in reactance value with respect to the switch's off-duty cycle. [Figure 4] Diagram showing the configuration of the phase difference detection circuit. [Figure 5] This diagram shows the change in the output voltage of a phase difference detection circuit in response to the voltage-current phase difference. [Figure 6] Diagram showing the configuration of the gate control circuit. [Figure 7] Timing chart showing the operation of the phase adjustment circuit [Figure 8] Timing chart showing the operation of the variable reactor rectifier circuit with respect to switch S1. [Figure 9] Timing chart showing the operation of the variable reactor rectifier circuit with respect to switches S1 and S2. [Figure 10] This is a second embodiment, and the diagram shows the configuration of the variable reactor rectifier circuit. [Figure 11] Timing chart showing the operation of the variable reactor rectifier circuit with respect to switch S1. [Modes for carrying out the invention]

[0014] (First Embodiment) As shown in Figure 1, the power supply system of this embodiment includes a phase difference detection circuit 2 connected to a high-frequency power supply 1, a matching circuit / coupler etc. 3, a variable reactor rectifier circuit 4, and a gate control circuit 5, which supply the converted DC power to a load 6. The phase difference detection circuit 2 detects the phase difference between voltage and current of the AC power input from the high-frequency power supply 1 and outputs a DC voltage Vb corresponding to that phase difference to the gate control circuit 5. The matching circuit / coupler etc. 3 performs impedance matching and coupling to the input of the next stage variable reactor rectifier circuit 4. The variable reactor rectifier circuit 4 is controlled by the gate control circuit 5 and converts AC power to DC power while operating to compensate for fluctuations in the reactance component caused by aging deterioration etc. in the matching circuit / coupler etc. 3.

[0015] As shown in FIG. 2, in the variable reactor rectifier circuit 4, one end of LC resonance circuits 12a and 12b, which are series circuits of an inductor and a capacitor, is connected to each of the input terminals 11a and 11b. A series circuit of switches S1 and S2 is connected between the other ends of the LC resonance circuits 12a and 12b. Switches S1 and S2, which are the first and second switching elements, are both N-channel MOSFETs. The drains of each FET are commonly connected, and the sources thereof are connected to the other ends of the LC resonance circuits 12a and 12b, respectively.

[0016] First and second diodes D1 and D2 are connected in parallel to switches S1 and S2, respectively, and their cathode sides are common. First and second capacitors C1 and C2 are connected in parallel to diodes D1 and D2, respectively. A series circuit of inductors 13a and 13b is connected in parallel to the series circuit of switches S1 and S2. An output capacitor 14 is connected between the commonly connected drains of switches S1 and S2 and the common connection point of inductors 13a and 13b. The output capacitor 14 and the inductors 13a and 13b constitute a filter circuit 15. Both ends of the output capacitor 14 serve as output terminals for DC power.

[0017] As shown in the figure, let the input reactance as seen from the input terminals 11a and 11b be jXr, and let the reactance of each of the LC resonance circuits 12a and 12b be jX / 2. Although the details of the operation will be described later, if the magnitude of the reactance controlled by the variable reactor rectifier circuit 4 is -jXrec, then jXr = jX - jXrec.

[0018] As shown in Figure 3, this shifts the input reactance jXr to the positive side by the sum of the reactances jX of the LC resonant circuits 12a and 12b. As a result, the input reactance jXr controlled by the variable reactor rectifier circuit 4 spans both positive and negative poles. The maximum value of |jXrec| is determined by the capacitances C of the first and second capacitors C1 and C2. That is, the relationship is -jXrec∝-j / (ωC). Therefore, capacitance C is set to satisfy the maximum value of |jXrec| required in the system.

[0019] As shown in Figure 4, in the phase difference detection circuit 2, a series circuit of capacitors 17a and 17b is connected between the AC input terminals 16a and 16b. A circuit consisting of a transformer 18, a capacitor 19, and diodes 20a and 20b is connected in parallel to capacitor 17a. The primary winding of transformer 18 is connected to AC input terminal 16a, and capacitor 19 is connected in parallel to the secondary winding.

[0020] The cathode of diode 20a and the anode of diode 20b are connected to the common connection point of capacitors 17a and 17b. The anode of diode 20a and the cathode of diode 20b are connected to one end and the other end of capacitor 19, respectively. A voltage Vb is output from the common connection point of capacitors 17a and 17b via resistor 21. A parallel circuit of capacitor 22 and resistor 23 is connected between the output terminal of voltage Vb and ground.

[0021] If Vvd is the voltage at the common connection point of capacitors 17a and 17b2, and Vid is the terminal voltage of capacitor 19, then the output voltage Vb of the phase difference detection circuit 2 will be a value corresponding to the phase difference between voltage Vvd and voltage Vid, as shown in Figure 5, i.e., the current-voltage phase difference. Depending on whether the phase difference is lagging or leading, the voltage Vb will change from a negative value to a positive value.

[0022] As shown in Figure 6, the gate control circuit 5, which corresponds to the control unit, includes an error amplifier 24, a phase adjustment circuit 25, a 180° delay circuit 26, and gate drivers 27(1) and 27(2). The error amplifier 24 consists of an operational amplifier 31, resistors 32 and 33, and a capacitor 34. The output voltage Vb of the phase difference detection circuit 2 is input to the inverting input terminal of the operational amplifier 31 via the resistor 32, and the reference voltage is input to the non-inverting input terminal via the resistor 33. The capacitor 4 is connected between the inverting input terminal and the output terminal of the operational amplifier 31. The error amplifier 24 outputs an error voltage corresponding to the difference between the voltage Vb and the reference voltage.

[0023] In the phase adjustment circuit 25, the square wave signal generated by the square wave generator 35 consists of a resistor Rtr and a capacitor Ctr, and is input to the triangular wave generation unit 36, which corresponds to the triangular wave output circuit. The common connection point of the resistor Rtr and the capacitor Ctr is connected to the clock terminal CLK of the D flip-flop 39 via a coupling capacitor 37 and a buffer 38. The output terminal of the operational amplifier 31, which constitutes the error amplifier 24, is connected to ground via a series circuit of resistors 40 and 41. The common connection point of resistors 40 and 41 is connected to the input terminal of the buffer 38. Resistors 40 and 41 correspond to the offset application unit.

[0024] The input terminal D of the D flip-flop 39 is pulled up to the power supply. The output terminal Q is directly connected to the input terminal of gate driver 27(1) and also connected to the input terminal of gate driver 27(2) via a 180° delay circuit 26. The output terminal Q bar is connected to ground via a series circuit of resistor 42 and capacitor 43. The output terminal Q bar is also connected to the common connection point of resistor 42 and capacitor 43 via a series circuit of resistor 44 and diode 45. When the level of the output terminal Q bar goes low, capacitor 43 discharges and the D flip-flop 39 is cleared.

[0025] As shown in Figure 7, in the phase adjustment circuit 25, the error voltage output by the error amplifier 24 is applied as an offset to the triangular wave generated by the triangular wave generator 36 based on the input pulse signal 1. This changes the timing at which the amplitude of the triangular wave exceeds the threshold Vth of the buffer 38. In accordance with this change, the phase output from the output terminal Q of the D flip-flop 39 changes.

[0026] Next, the operation of this embodiment will be explained. Since switches S1 and S2 have the same switching pattern but with a phase difference of 180°, the operation of switch S1 will be explained. Note that the numbers in parentheses next to the sections correspond to the circled numbers in the figure. In section (1) shown in Figure 8, the diode D1 is turned on by the AC input and the forward current Id1 begins to flow. In the following section (2), after the drain-source voltage Vds of switch S1 becomes approximately zero, the gate signal Vgs1 of switch S1 is set to a high level to turn on switch S1. At this time, the turn-on of switch S1 is zero-voltage switching; ZVS.

[0027] In section (3), diode D1 is turned off, but switch S1 is on, so current Is1 continues to flow through switch S1. After a predetermined time has elapsed, the gate signal Vgs1 of switch S1 is set to a low level to turn off switch S1. At this time, the capacitor C1 connected in parallel with switch S1 also causes the turn-off to be ZVS. In the following section (4), the drain-source voltage Vds rises as switch S1 is turned off.

[0028] Figure 9 shows the operating timing chart for switches S1 and S2. Specifically, the reactance -jXrec controlled by the variable reactor rectifier circuit 4 becomes a negative value due to capacitors C1 and C2. Its magnitude is determined by the off-duty cycle of switches S1 and S2, that is, the length of the off-period shown in Figure 9. In this embodiment, the off-period of switches S1 and S2 is controlled by gate signals Vgs1 and Vgs2, and the value of reactance -jXrec is varied as shown in Figure 3, thereby variably controlling the input reactance jXr.

[0029] As described above, in this embodiment, in the variable reactor rectifier circuit 4, one end of the LC resonant circuits 12a and 12b is connected to the input terminals 11a and 11b, respectively, to which AC power is input. A series circuit of switches S1 and S2 is connected between the other ends of the LC resonant circuits 12a and 12b. Diodes D1 and D2 are connected in parallel to switches S1 and S2, respectively, and their cathodes are common. Capacitors C1 and C2 are connected in parallel to diodes D1 and D2, respectively. The filter circuit 15 has a series circuit of inductors 13a and 13b connected in parallel to the series circuit of switches S1 and S2, and an output capacitor 15 connected between the DC output terminals. The gate control circuit 5 controls the reactance by switching switches S1 and S2 with a phase difference of 180 degrees from each other.

[0030] More specifically, among switches S1 and S2, the switch is turned on after the corresponding diode is turned on, and after a predetermined time has elapsed after the diode has turned off, thereby performing variable control of the reactance based on the off-duty cycle. With this configuration, only one DC-DC converter needs to be connected to the output capacitor 14, and the reactance jXr can be variably controlled in both polarity by the variable reactance rectifier circuit 4. Therefore, the circuit size can be reduced compared to conventional configurations.

[0031] (Second Embodiment) In the following description, parts identical to those in the first embodiment are denoted by the same reference numerals and their descriptions are omitted, while the differences are described. As shown in Figure 10, the variable reactor rectifier circuit 51 of the second embodiment is configured as if one side of the variable reactor rectifier circuit 4 has been cut out, for use in a single-ended system. A series circuit of the LC resonant circuit 12 and switch S1 is connected between the AC input terminals 11a and 11b. The diode D1 and capacitor C1 connected in parallel with this switch S1 correspond to the switch S2, diode D2, and capacitor C2 of the first embodiment, and are oriented in the same direction. The filter circuit 52, which replaces the filter circuit 15, is composed of a series circuit of the inductor 13 and output capacitor 14.

[0032] As shown in Figure 11, the variable reactor rectifier circuit 51 is controlled by the gate control circuit 5 of the first embodiment by a signal pattern that controls one of the switches. In the second embodiment, the reactance of the LC resonant circuit 12 is set to jX, so that the input reactance jXr is jXr = jX - jXrec. Then, the switching of switch S1 is controlled in the same way as in the first embodiment, and the reactance is variably controlled by the off-duty cycle. If the capacitance of capacitor C1 is set to the same value as in the first embodiment, the variable range of the reactance becomes narrower, but the circuit size becomes smaller.

[0033] (Other embodiments) The first and second diodes may be the built-in diodes of the MOSFET. The first and second capacitors may consist only of the parasitic capacitance between the drain and source of the MOSFET, or they may consist of that parasitic capacitance plus a capacitor connected in parallel with the MOSFET. In the first embodiment, switches S1 and S2 may be connected in a direction that shares a common source for the N-channel MOSFET. The switching element is not limited to N-channel MOSFETs. The capacitances C of the first and second capacitors may be set such that ΔX < (the maximum value of |jXrec|).

[0034] This disclosure is described in accordance with the embodiments, but it is understood that this disclosure is not limited to such embodiments or structures. This disclosure also includes various modifications and variations within the equivalence. In addition, various combinations and forms, as well as other combinations and forms that include only one, more, or fewer of those elements, fall within the scope and concept of this disclosure. [Explanation of symbols]

[0035] In the diagram, 1 is a high-frequency power supply, 2 is a phase difference detection circuit, 4 is a variable reactor rectifier circuit, 5 is a gate control circuit, 6 is a load, 11a and 11b are input terminals, 12a and 12b are LC resonant circuits, 13a and 13b are inductors, 14 is an output capacitor, 15 is a filter circuit, S1 and S2 are switches, C1 and C2 are capacitors, and D1 and D2 are diodes.

Claims

1. Two LC resonant circuits (12a, 12b) are connected to each of the two input terminals (11a, 11b) to which AC power is input, Between the other ends of these two LC resonant circuits, a series circuit of first and second switching elements (S1, S2) is connected in opposite directions. First and second diodes (D1, D2) are connected in parallel to each of the first and second switching elements, such that their cathodes or anodes are common. These first and second diodes are connected in parallel to each other by first and second capacitors (C1, C2), A filter circuit (15) having a series circuit of two inductors (13a, 13b) connected in parallel to the series circuit of the first and second switching elements, and an output capacitor (14) connected between the DC output terminals, The system includes a control unit (5) that performs variable control of reactance by switching the first and second switching elements with a phase difference of 180 degrees relative to each other, If the variable control value required for the reactance is ΔX, and the reactance variably controlled by the control unit is -jXrec, then the capacitances C of the first and second capacitors are set such that ΔX ≤ (the maximum value of |jXrec|). The sum of the reactances jX of the two LC resonant circuits is used to shift the reactance jXr as seen from the input terminal to the positive side, thereby making the variable range of the reactance jXr bipolar. The control unit turns on the first and second switching elements after the corresponding diode is turned on. A rectifier circuit that, after the diode is turned off, turns off the switching element after a predetermined time has elapsed, and performs variable control of the reactance by the off-duty cycle of the switching element.

2. A series circuit of an LC resonant circuit (12) and a switching element (S1) is connected between input terminals to which AC power is input, A diode (D1) is connected in parallel with the switching element, with its cathode facing the LC resonant circuit side, A capacitor (C1) is connected in parallel to this diode, A filter circuit (52) having an inductor (13) and an output capacitor (14) connected in parallel to the switching element, The system includes a control unit (5) that performs variable control of the reactance by switching the switching element, If the variable control value required for the reactance is ΔX, and the reactance variably controlled by the control unit is -jXrec, then the capacitance C of the capacitor connected in parallel with the diode is set to satisfy ΔX ≤ (the maximum value of |jXrec|). The reactance jX of the LC resonant circuit shifts the reactance jXr as seen from the input terminal to the positive side, thereby making the variable range of the reactance jXr bipolar. The control unit turns on the switching element after the diode is turned on. A rectifier circuit that, after the diode is turned off, turns off the switching element after a predetermined time has elapsed, and performs variable control of the reactance by the off-duty cycle of the switching element.

3. The control unit includes a phase difference detection unit that detects the phase difference between the voltage and current of the AC power, A rectifier circuit according to claim 1 or 2, wherein the off-duty ratio of the switching element is changed based on the phase difference.

4. The phase difference detection unit outputs a voltage Vb corresponding to the phase difference. The control unit includes an error amplifier (24) that outputs an error voltage between the voltage Vb and the reference voltage, A triangular wave output circuit (36) that outputs a triangular wave signal, The aforementioned triangular wave signal is offset by the error voltage (40, 41), The system includes a flip-flop (39) that is triggered by the aforementioned offset triangular wave signal and cleared a certain time after the trigger, The rectifier circuit according to claim 3, which drives the switching element based on the output signal of the flip-flop.

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