JP2013169118A - Conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-size and inexpensive conversion device capable of converting an AC voltage into a DC voltage at a high power-factor.SOLUTION: A rectifier circuit 11 rectifies an AC voltage to be converted that is outputted from an AC power supply 2 into a DC voltage. The DC voltage rectified by the rectifier circuit 11 is applied between input terminals S1 and S2 of an inverter via a coil L1. The inverter 12 converts the DC voltage applied between the input terminals S1 and S2 into an AC voltage. A transformer 13 transforms the AC voltage converted by the inverter 12, and a rectifier circuit 14 rectifies the AC voltage transformed by the inverter 12. A control section 16 controls an operation of the inverter 12, and operations controlled by the control section 16 include a short-circuit operation short-circuiting between the input terminals S1 and S2.

Description

  The present invention relates to a converter for converting an alternating voltage into a direct voltage.

  In recent years, a plug-in that is equipped with a conversion device that converts an AC voltage output from an AC power supply (commercial power supply) drawn into a home into a DC voltage, and charges the battery by applying the DC voltage converted by the conversion device to the battery. Hybrid vehicles or electric vehicles are popular.

  In general, a conversion device that converts an AC voltage output from an AC power source drawn into a household into a DC voltage converts the AC voltage into a DC voltage with a high power factor of 80% or more in order to increase the power transmission efficiency from the power plant to each household. It needs to be converted to voltage. Currently, a converter that converts an AC voltage into a DC voltage with a high power factor has been realized (see Patent Document 1).

  FIG. 6 is a circuit diagram showing a main configuration of a conventional converter. The conversion device 7 includes rectifier circuits 71 and 75, a power factor correction circuit 72, an inverter 73, a transformer 74, a smoothing circuit 76, and a control unit 77.

  The AC voltage to be converted output from the AC power supply 8 is rectified to a DC voltage by the rectifier circuit 71, and the rectified DC voltage is output to the inverter 73 via the power factor correction circuit 72. The inverter 73 has a bridge circuit composed of a plurality of switches (not shown), and the control unit 77 turns on / off the plurality of switches separately, thereby converting the DC voltage applied through the power factor correction circuit 72 into a high frequency. The voltage is converted into an AC voltage, and the converted AC voltage is applied between both terminals of one coil of the transformer 74.

  The transformer 74 transforms an alternating voltage applied between both terminals of one coil, and outputs the transformed alternating voltage to the rectifier circuit 75 from both terminals of the other coil. The rectifier circuit 75 rectifies the AC voltage transformed by the transformer 74 into a DC voltage, and outputs the rectified DC voltage to the smoothing circuit 76. The smoothing circuit 76 smoothes the DC voltage output from the rectifier circuit 75 and charges the battery 9 with the smoothed DC voltage.

  The power factor correction circuit 72 includes a coil L7, an FET (Field Effect Transistor) 7a, a diode 7b, and a capacitor C7. As for the coil L7, one terminal is connected to the rectifier circuit 71, and the other terminal is connected to the drain of the FET 7a and the anode of the diode 7b. The cathode of the diode 7 b is connected to one terminal of the capacitor C 7 and the inverter 73. The source of the FET 7 a is connected to the other terminal of the capacitor C 7, the rectifier circuit 71 and the inverter 73. The diode 7 b prevents current from flowing in the direction from the inverter 73 to the rectifier circuit 71.

  The gate of the FET 7a is connected to the control unit 77, and the control unit 77 turns on / off the FET 7a by adjusting the voltage applied to the gate of the FET 7a. In the FET 7a, when the voltage applied to the gate is equal to or higher than the predetermined voltage, a current flows between the drain and the gate to turn on the FET 7a. When the voltage applied to the gate is lower than the predetermined voltage, the drain and the gate No current flows between them, and the FET 7a is turned off.

  In the state where the FET 7a is OFF, a current flows through the converter 7 when the pulsating DC voltage output from the rectifier circuit 71 exceeds the voltage between both terminals of the capacitor C7. In this state, in the AC voltage to be converted output from the AC power supply 8, the power factor is low because there are few portions in phase with the AC current flowing back to the AC power supply 8.

  Therefore, the control unit 77 turns on the FET 7a to flow a current through the coil L7 for a certain time, and then turns off the FET 7a to boost the voltage between both terminals of the coil L7. The coil L7 acts to eliminate a change in current. For this reason, when the FET 7a is turned off and the current flowing through the coil L7 is reduced, the coil L7 increases the voltage between both terminals of the coil L7 so as to keep the same amount of current flowing. The absolute value of the voltage raised by the coil L7 increases as the ON period during which the FET 7a is ON is longer.

  The control unit 77 can adjust the absolute value of the voltage output from the terminal on the inverter 73 side of the coil L7 by adjusting the ON period of the FET 7a, and appropriately adjust the voltage from the voltage between both terminals of the capacitor C7. You can surpass it.

  The control unit 77 adjusts the ON period of the FET 7a to increase the voltage of the other terminal of the coil L7, thereby returning a large amount of current that matches the phase of the AC voltage to be converted to the AC power supply 8. . Thereby, the converter 7 can convert an alternating voltage into a direct voltage with a high power factor.

Japanese Patent No. 3194550

  However, the conventional conversion device 7 has a problem in that many components such as the FET 7a and the capacitor C7 must be provided in order to increase the power factor, and the size is large and the manufacturing cost increases.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a small and inexpensive converter that can convert an AC voltage into a DC voltage with a high power factor.

  A converter according to the present invention has an input terminal pair to which a DC voltage obtained by rectifying an AC voltage to be converted is applied, an inverter that converts the DC voltage applied between the input terminal pair to an AC voltage, In the converter, comprising: a transformer that transforms the AC voltage converted by the inverter; a rectifier that rectifies the AC voltage transformed by the transformer into a DC voltage; and a control unit that controls the operation of the inverter. A coil connected to one terminal of the pair is provided, and the operation controlled by the control unit includes a short-circuit operation for short-circuiting the input terminal pair.

  In the present invention, a DC voltage obtained by rectifying the AC voltage to be converted is applied between the input terminal pair of the inverter via the coil. The inverter converts a DC voltage applied between the input terminal pair into an AC voltage. The transformer transforms the alternating voltage converted by the inverter, and the rectifier circuit rectifies the alternating voltage transformed by the transformer. The control unit controls the operation of the inverter, and the operation controlled by the control unit includes a short-circuit operation for short-circuiting between the input terminal pairs.

  Since a coil is connected to one of the input terminal pairs, when the input terminal pair is short-circuited, both terminals of the AC power supply that outputs the AC voltage to be converted are not short-circuited, and current flows back to the AC power supply. To do.

  The control unit includes a short-circuit operation as appropriate in the operation for causing the inverter to convert the DC voltage to the AC voltage, so that a large amount of current having the same phase as the AC voltage rectified to the DC voltage is supplied to the AC power source. Reflux and high power factor. Furthermore, since only a coil is added to realize conversion with a high power factor, the apparatus is small and inexpensive.

  In the converter according to the present invention, the control unit is configured to adjust a period during which the inverter performs the short-circuit operation according to an absolute value of the AC voltage to be converted. .

  In the present invention, the control unit adjusts the period during which the inverter performs the short-circuit operation according to the absolute value of the AC voltage to be converted, so that the power factor can be further increased.

  The converter according to the present invention further includes a capacitor connected between the inverter and the transformer, and the control unit converts the frequency of the AC voltage converted by the inverter according to the absolute value of the AC voltage to be converted. It is comprised so that it may adjust.

  In the present invention, since the capacitor is connected between the inverter and the transformer that transforms the AC voltage converted by the inverter, the series resonance circuit is formed by one coil and the capacitor of the transformer connected to the inverter. Composed. The impedance of the series resonance circuit changes depending on the frequency of the AC voltage output from the inverter to one coil of the transformer.

  Therefore, when the operation performed by the inverter shifts from the short-circuit operation to another operation and the current flows back to the AC power source via the series resonance circuit, the control unit adjusts the frequency of the AC voltage output by the inverter. It is possible to adjust the absolute value of the current flowing back to the AC power supply. As a result, the current flowing back to the AC power supply in phase with the AC voltage to be converted is increased, and the power factor can be further increased.

  In the converter according to the present invention, the inverter includes a bridge circuit including a plurality of switches, and a capacitor connected between an output terminal pair of the bridge circuit.

  In the present invention, a capacitor is connected between the pair of output terminals of the bridge circuit composed of a plurality of switches, and the capacitor removes noise generated by turning on / off the plurality of switches. AC voltage with less noise is output.

  According to the present invention, since the operation of the inverter that converts the DC voltage applied between the input terminal pair via the coil into the AC voltage includes a short-circuit operation that short-circuits between the input terminal pair, the AC voltage is increased with a high power factor. It is possible to realize a small and inexpensive conversion device capable of converting the above.

It is a circuit diagram which shows the principal part structure of the converter which concerns on this invention. It is a timing chart for demonstrating operation | movement of a converter. It is a timing chart for demonstrating operation | movement of a converter. It is explanatory drawing for demonstrating the adjustment method of the absolute value of alternating current by adjustment of the period when an inverter performs short circuit operation. It is explanatory drawing for demonstrating the adjustment method of the absolute value of alternating current by the impedance adjustment of a series resonance circuit. It is a circuit diagram which shows the principal part structure of the conventional converter.

Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof.
FIG. 1 is a circuit diagram showing a main configuration of a conversion apparatus according to the present invention. The converter 1 is connected to both terminals of an AC power source 2 that outputs an AC voltage to be converted, for example, having a frequency of 50 Hz or 60 Hz, and both terminals of the battery 3. The output AC voltage to be converted is converted into a DC voltage, and the converted DC voltage is applied between both terminals of the battery 3. Thereby, the battery 3 is charged.

  The conversion device 1 includes rectifier circuits 11 and 14, an inverter 12, a transformer 13, a smoothing circuit 15, a control unit 16, a coil L1, and a capacitor C1. The inverter 12 has input terminals S1, S2 and output terminals U1, U2, and the transformer 13 is composed of coils 13a, 13b.

  The rectifier circuit 11 includes diodes D1, D2, D3, and D4. The anode of the diode D1 and the cathode of the diode D2 are connected to one terminal of the AC power supply 2, the anode of the diode D3, and the cathode of the diode D4 are connected to each other. The other terminal of the AC power source 2 is connected. The cathodes of the diodes D1 and D3 are connected to the input terminal S1 of the inverter 12 via the coil L1, and the anodes of the diodes D2 and D4 are connected to the input terminal S2 of the inverter 12.

  Thus, the rectifier circuit 11 to which the diodes D1, D2, D3, and D4 are connected rectifies the AC voltage to be converted output from the AC power supply 2 into a DC voltage, and the rectified DC voltage is passed through the coil L1. The voltage is applied between the input terminals S1 and S2 of the inverter 12. The input terminals S1 and S2 constitute an input terminal pair of the inverter 12.

  The inverter 12 further includes FETs 21, 22, 23, and a capacitor C2 in addition to the input terminals S1 and S2 and the output terminals U1 and U2. The drains of the FETs 21 and 23 are connected to the input terminal S1, and the sources of the FETs 22 and 24 are connected to the input terminal S2.

  The source of the FET 21 and the drain of the FET 22 are connected to the output terminal U1, and the source of the FET 23 and the drain of the FET 24 are connected to the output terminal U2. The gates of the FETs 21, 22, 23, and 24 are connected to the control unit 16 separately. The FETs 21, 22, 23, and 24 constitute a bridge circuit. Inside the inverter 12, a capacitor C2 is connected between the output terminals U1 and U2. Outside the inverter 12, a series resonance circuit constituted by the coil 13a of the transformer 13 and the capacitor C1 is connected between the output terminals U1 and U2.

  Each of the FETs 21, 22, 23, and 24 is an N-channel MOSFET (Metal Oxide Semiconductor Field Effect Transistor), functions as a semiconductor switch, and is turned on / off by the control unit 16. Each of the FETs 21, 22, 23, and 24 is turned on when a current exceeding the predetermined voltage is applied to the gate by the control unit 16, and the control unit 16 gates the voltage less than the predetermined voltage. When applied to, no current flows between the drain and gate and the transistor is turned off.

  The control unit 16 controls the operation of the inverter 12 by turning on / off the FETs 21, 22, 23, and 24 individually. The control unit 16 implements a first operation realized by turning on the FETs 21 and 24 and turning off the FETs 22 and 23, and turning off the FETs 21 and 24 and turning on the FETs 22 and 23, respectively. The inverter 12 is caused to alternately perform the second operation.

  When the control unit 16 causes the inverter 12 to perform the first operation, current flows from the output terminal U1 to U2 in the series resonance circuit including the coil 13a and the capacitor C1. Similarly, when the control unit 16 causes the inverter 12 to perform the second operation, a current flows from the output terminal U2 to U1 in the series resonance circuit including the coil 13a and the capacitor C1.

  For this reason, when the control unit 16 causes the inverter 12 to alternately perform the first and second operations, an AC voltage is output from the output terminals U1 and U2 of the inverter 12, and between both terminals of the coil 13a of the transformer 13. An alternating voltage is applied. The frequency of the AC voltage output from the inverter 12 is determined by the interval at which the inverter 12 alternately performs the first and second operations, and is adjusted to, for example, 100 kHz. The shorter the interval at which the inverter 12 alternately performs the first and second operations, the higher the frequency of the AC voltage output from the inverter 12.

  The control unit 16 further causes the inverter 12 to appropriately perform a short-circuit operation for short-circuiting between the input terminals S1 and S2 by turning on all of the FETs 21, 22, 23, and 24 during the first and second operations. When the inverter 12 performs a short-circuit operation, current flows back to the AC power supply 2. At this time, since the coil L1 is connected to the input terminal S1 of the inverter 12, both terminals of the AC power supply 2 are not short-circuited. Since the coil L1 only needs to prevent a short circuit between both terminals of the AC power supply 2, a large inductance is not required unlike a boosting coil, and the size of the coil L1 is small.

  The control unit 16 is connected to a connection node between the anode of the diode D1 and the cathode of the diode D2, and a connection node between the anode of the diode D3 and the cathode of the diode D4, and the AC power supply 2 outputs to the rectifier circuit 11. The AC voltage to be converted is monitored.

  The control unit 16 adjusts the period during which the inverter 12 performs a short-circuit operation according to the absolute value of the AC voltage to be converted output from the AC power supply 2. The longer the period during which the inverter 12 is performing the short-circuit operation, the greater the absolute value of the current flowing back to the AC power supply 2.

While the control unit 16 causes the inverter 12 to perform a short-circuit operation, energy is stored in the coil L1.
When the operation performed by the inverter 12 shifts from the short-circuit operation to the first or second operation, the coil L1 recirculates the current to the AC power source 2 via the series resonance circuit including the coil 13a and the capacitor C1, and stores the accumulated energy. Release.

  The impedance of the series resonance circuit is zero when the frequency of the AC voltage output from the inverter 12 matches the resonance frequency of the series resonance circuit, and increases as the frequency of the AC voltage output from the inverter 12 increases from the resonance frequency. Become. The resonance frequency of the series resonance circuit is a value calculated by 1 / (2π × √ (Lr × Cr)) when the inductance of the coil 13a is Lr and the capacitance of the capacitor C1 is Cr. It is.

  The control unit 16 changes the frequency of the AC voltage output from the output terminals U1 and U2 by adjusting the interval at which the inverter 12 alternately performs the first and second operations, and the series of the coil 13a and the capacitor C1. Adjust the impedance of the resonant circuit. When the operation performed by the inverter 12 is shifted from the short-circuit operation to another operation and the current flows back to the AC power supply 2 through the series resonance circuit, the control unit 16 adjusts the impedance of the series resonance circuit to thereby change the AC power supply. The absolute value of the current flowing back to 2 can be adjusted.

  The control unit 16 adjusts the frequency of the AC voltage output from the output terminals U1 and U2 of the inverter 12 in accordance with the AC voltage output from the AC power supply 2, and sets the impedance of the series resonance circuit including the coil 13a and the capacitor C1. adjust.

  The capacitor C2 removes noise generated when the control unit 16 turns on / off the FETs 21, 22, 23, and 24 separately. As a result, the inverter 12 outputs an AC voltage with less noise from the output terminals U1 and U2. When the operation performed by the inverter 12 shifts from the short-circuit operation to the first or second operation, the energy accumulated in the coil L1 is released, and a large current flows through the inverter 12, and the FETs 21, 22, 23, 24, etc. There is a risk of the element being destroyed. However, since the current flowing in the inverter 12 is averaged by the capacitor C2, destruction of the element is prevented.

  The transformer 13 is configured by winding coils 13a and 13b around an annular iron core (not shown). The transformer 13 transforms the AC voltage output from the output terminals U1 and U2 of the inverter 12 and applied between both terminals of the coil 13a of the transformer 13, and the transformed AC voltage is rectified from both terminals of the coil 13b. 14 for output.

  The amplitude of the AC voltage output from both terminals of the coil 13b is determined by the product of the value obtained by dividing the number of turns of the coil 13b by the number of turns of the coil 13a and the amplitude of the AC voltage applied between both terminals of the coil 13a.

  The rectifier circuit 14 includes diodes D5, D6, D7, and D8. The anode of the diode D5 and the cathode of the diode D6 are connected to one terminal of the coil 13b, and the anode of the diode D7 and the cathode of the diode D8 are the coils. It is connected to the other terminal of 13b. The cathodes of the diodes D5 and D7 are connected to one terminal of the coil L2 included in the smoothing circuit 15, and the anodes of the diodes D6 and D8 are connected to one terminal of the capacitor C3 included in the smoothing circuit 15.

  In this way, the rectifier circuit 14 to which the diodes D5, D6, D7, and D8 are connected rectifies the AC voltage output from both terminals of the coil 13b of the transformer 13 into a DC voltage, and the rectified DC voltage is smoothed by the circuit 15. Output to.

  The other terminal of the coil L2 of the smoothing circuit 15 is connected to the other terminal of the capacitor C1 and the positive terminal of the battery 3, and one terminal of the capacitor C1 of the smoothing circuit 15 is connected to the anode of each of the diodes D6 and D8. In addition, it is connected to the negative terminal of the battery 3.

  The smoothing circuit 15 smoothes the DC voltage rectified by the rectifier circuit 14 using the coil L2 and the capacitor C3, and applies the smoothed DC voltage to the battery 3. Thereby, the battery 3 is charged.

  When the pulsating DC voltage rectified by the rectifier circuit 14 exceeds the voltage between both terminals of the capacitor C3, current flows in the smoothing circuit 15, and current flows in the rectifier circuit 11, the inverter 12, the transformer 13, and the rectifier circuit 14. Flowing. Therefore, while the inverter 12 is performing the first or second operation, when the pulsating DC voltage rectified by the rectifier circuit 14 exceeds the voltage between both terminals of the capacitor C3, the current flows back to the AC power source 2. In other cases, the current does not return to the AC power source 2. Since the power factor decreases in such a state, the control unit 16 causes the inverter 12 to appropriately perform a short-circuit operation while alternately performing the first and second operations, thereby supplying current to the AC power supply 2. Reflux to increase power factor.

  2 and 3 are timing charts for explaining the operation of the conversion apparatus 1. The control unit 16 turns on / off the FETs 21, 22, 23, and 24 of the inverter 12 while the AC power supply 2 applies the AC voltage Va to be converted illustrated in FIG. 2 to the conversion device 1. Here, the AC voltage Va is a voltage of the terminal on the diode D1 side with respect to the terminal on the diode D4 side in the AC power supply 2.

  As shown in FIG. 2, the control unit 16 causes the inverter 12 to perform a first operation in which the FETs 21 and 24 are on and the FETs 22 and 23 are off, and a short-circuit operation in which all the FETs 21, 22, 23, and 24 are on. The second operation is performed in which the FETs 21 and 24 are off and the FETs 22 and 23 are on. The control unit 16 causes the inverter 12 to repeatedly perform operations in the order of the first operation, the short-circuit operation, the second operation, and the short-circuit operation. The repetition cycle in which the control unit 16 causes the inverter 12 to perform the first operation, the short-circuit operation, the second operation, and the short-circuit operation in this order is sufficiently shorter than the cycle of the AC voltage Va.

  FIG. 2 further shows the waveform of the alternating current Ia flowing back to the alternating current power source 2 and the waveform of the alternating voltage Vb applied to the coil 13 a of the transformer 13. As for the AC current Ia, the current flowing from the cathode of the diode D2 to the anode of the diode D3 via the AC power supply 2 is positive. The AC voltage Vb is a voltage at the output terminal U1 in the coil 13a with reference to the voltage at the terminal on the capacitor C1 side.

  As shown in FIG. 2, while the control unit 16 causes the inverter 12 to perform a short-circuit operation, no voltage is applied between both terminals of the coil 13a of the transformer 13, and the AC voltage Vb is zero. Further, while the control unit 16 causes the inverter 12 to perform a short-circuit operation, when the AC voltage Va of the AC power supply 2 is positive, a positive current flows through the AC power supply 2 (Ia> 0), and the AC power supply 2 When the AC voltage Va is negative, a negative current flows through the AC power supply 2 (Ia <0).

  Further, when the operation performed by the inverter 12 shifts from the short-circuit operation to the first or second operation, unless the pulsating DC voltage output from the rectifier circuit 14 to the smoothing circuit 15 exceeds the voltage between both terminals of the capacitor C3, Since it does not return to the AC power source 2, the absolute value of the AC current Ia that returns to the AC power source 2 gradually decreases to zero.

  Therefore, when the control unit 16 appropriately performs the short-circuit operation between the first and second operations, the alternating current Ia that matches the phase of the alternating voltage Va is returned to the alternating current power source 2 and the power factor is increased.

  Further, when the control unit 16 causes the inverter 12 to perform the first operation, a positive voltage is applied to the coil 13a of the transformer 13 (Vb> 0), and the control unit 16 causes the inverter 12 to perform the second operation. In this case, a negative voltage is applied to the coil 13a of the transformer 13 (Vb <0).

  Therefore, when the operation that the control unit 16 causes the inverter 12 to perform is changed from the first operation to the second operation or from the second operation to the first operation through the short-circuit operation, the sign of the voltage applied to the coil 13a is positive or negative. Therefore, an alternating voltage Vb as shown in FIG. 2 is output from the output terminals U1 and U2 of the inverter 12. The frequency of the AC voltage Vb is the reciprocal of the repetition period that the control unit 16 causes the inverter 12 to perform in the order of the first operation, the short-circuit operation, the second operation, and the short-circuit operation.

  FIG. 3 shows the AC voltage Vc output from both terminals of the coil 13b when the AC voltage Vb shown in FIG. 2 is applied between both terminals of the coil 13a of the transformer 13. The AC voltage Vc is a voltage at the terminal on the diode D5 side of the coil 13b with reference to the voltage at the terminal on the diode D8 side of the coil 13b.

  As shown in FIG. 3, the waveform of the AC voltage Vc output from both terminals of the coil 13b is similar to the waveform of the AC voltage Vb applied between both terminals of the coil 13a, and the amplitude of the AC voltage Vc is AC. It is larger than the amplitude of the voltage Vb.

  The AC voltage Vc is rectified by the rectifier circuit 14 and a pulsating DC voltage Vd as shown in FIG. 3 is output from the rectifier circuit 14 to the smoothing circuit 15. Here, the DC voltage Vd is a voltage of the cathode of the diode D7 with reference to the voltage of the anode of the diode D8.

  The pulsating DC voltage Vd is smoothed by the smoothing circuit 15, and a constant DC voltage Ve as shown in FIG. 3 is output from the smoothing circuit 15 and applied to the battery 3. Thereby, the battery 3 is charged. The DC voltage Ve is a voltage of the terminal on the coil L2 side with respect to the voltage of the terminal on the diode D8 side in the capacitor C3.

  FIG. 4 is an explanatory diagram for explaining a method of adjusting the absolute value of the alternating current Ia by adjusting the period during which the inverter 12 performs the short-circuit operation. FIG. 4 shows a timing chart of the on / off states of the FETs 21 and 24 and the on / off state of the FETs 22 and 23.

  As described above, the absolute value of the current flowing back to the AC power supply 2 increases as the period during which the control unit 16 causes the inverter 12 to perform a short-circuit operation is longer. The control unit 16 adjusts the period during which the inverter 12 is performing a short-circuit operation according to the absolute value of the AC voltage Va of the AC power supply 2.

  As shown in FIG. 4, the control unit 16 adjusts the time T1 when the FETs 21 and 24 each shift from the on-state to the off-state, and the time T2 when each of the FETs 22 and 23 transitions from the on-state to the off-state. The period during which the inverter 12 performs the short-circuit operation is adjusted.

  The time point T1 is from the nearest time point Ta before the time point T1 among the time points when the FETs 22 and 23 shift from the off state to the on state, and after the time point T1 when the FETs 21 and 24 shift from the off state to the on state. Is adjusted in the range up to the nearest time point Tb. The control unit 16 brings the time point T1 closer to the time point Ta when shortening the time during which the inverter 12 performs the short-circuit operation, and brings the time point T1 closer to the time point Tb when increasing the time during which the inverter 12 performs the short-circuit operation.

  Similarly, the time point T2 is the time point when the FETs 22 and 23 shift from the OFF state to the ON state from the closest time point Tc before the time point T2 among the time points when the FETs 21 and 24 shift from the OFF state to the ON state. Adjustment is made in a range up to the nearest time Td after time T2. The control unit 16 brings the time point T2 closer to the time point Tc when the time for the inverter 12 to perform the short-circuit operation is shortened, and brings the time point T2 closer to the time point Td when the time for the inverter 12 to perform the short-circuit operation is lengthened.

  The control unit 16 adjusts the time during which the inverter 12 performs the short-circuit operation according to the absolute value of the AC voltage Va output from the AC power source 2 shown in FIG. Thereby, the control part 16 can adjust the alternating current Ia to an alternating current with more parts in phase with the alternating voltage Va, and the converter 1 is applied by the alternating current power source 2 with a higher power factor. AC voltage can be converted.

  For example, the control unit 16 lengthens the time for which the inverter 12 performs the short-circuit operation when the absolute value of the AC voltage Va is small, and shortens the time for the inverter 12 to perform the short-circuit operation when the absolute value of the AC voltage Va is large. .

  This is because, depending on the magnitude of the absolute value of the AC voltage Va, the absolute value of the current flowing back to the AC power supply 2 when the inverter 12 performs a short-circuit operation for a unit time becomes large, and furthermore, the absolute value of the AC voltage Va. This is because when the value is large, the DC voltage output from the rectifier circuit 14 exceeds the voltage between both terminals of the capacitor C3, and the current flows back to the AC power source 2.

  Therefore, when the absolute value of the alternating voltage Va is small, the absolute value of the alternating current Ia that flows back to the alternating current power source 2 per unit time is small. When the value is large, the absolute value of the alternating current Ia that flows back to the alternating-current power supply 2 per unit time is large, so the time for which the inverter 12 performs the short-circuit operation is shortened.

  In the waveform of the alternating current Ia shown in FIG. 2, when the absolute value of the alternating voltage Va is large and the direct current voltage output from the rectifier circuit 14 exceeds the voltage between both terminals of the capacitor C3, it is returned to the alternating current power source 2. The current to be used is not shown for simplicity of explanation. Furthermore, in the timing chart of the on / off states of the FETs 21 and 24 and the on / off state of the FETs 22 and 23 shown in FIG. 2, the time during which the inverter 12 performs the short-circuit operation is uniform.

  FIG. 5 is an explanatory diagram for explaining a method of adjusting the absolute value of the alternating current Ia by adjusting the impedance of the series resonance circuit. FIG. 5A shows the impedance of the series resonant circuit with respect to the frequency of the AC voltage Vb applied to the series resonant circuit composed of the coil 13a and the capacitor C1. As shown in FIG. 5A, when the frequency of the AC voltage Vb output from the output terminals U1 and U2 by the inverter 12 matches the resonance frequency of the series resonance circuit, the impedance of the series resonance circuit is zero, and the AC voltage Vb The farther the frequency is from the resonance frequency, the larger the impedance of the series resonance circuit.

  FIG. 5B shows the waveform of the alternating current Ia at each frequency of the alternating voltage Vb. As described above, while the control unit 16 causes the inverter 12 to perform a short-circuit operation, the absolute value of the alternating current Ia gradually increases with time. Further, when the operation that the control unit 16 causes the inverter 12 to perform shifts from the short-circuit operation to the first or second operation and the DC voltage output from the rectifier circuit 14 is lower than the voltage between both terminals of the capacitor C3, the AC current Ia The absolute value gradually decreases to zero.

  As shown in FIG. 5B, the absolute value of the alternating current Ia that decreases while the control unit 16 causes the inverter 12 to perform the first or second operation is the impedance of the series resonance circuit including the coil 13a and the capacitor C1. The smaller the bigger.

  Therefore, the control unit 16 can adjust the impedance of the series resonance circuit by adjusting the frequency of the AC voltage Vb, and can further adjust the magnitude of the AC current Ia. Thereby, the control part 16 can adjust the alternating current Ia to the alternating current with more parts in which the phase of the alternating voltage Va coincides, and the converter 1 is applied by the alternating current power source 2 with a higher power factor. It is possible to convert the AC voltage to be converted.

  The control unit 16 increases (or decreases) the frequency of the AC voltage Vb by shortening (or increasing) the repetition period of the first operation, the short-circuit operation, the second operation, and the short-circuit operation that is repeatedly performed by the inverter 12. To do.

  For example, when the absolute value of the AC voltage Va is small, the control unit 16 reduces the impedance of the series resonance circuit by bringing the frequency of the AC voltage Vb close to the resonance frequency of the series resonance circuit, and when the absolute value of the AC voltage Va is large. In addition, the impedance of the series resonant circuit is increased by separating the frequency of the AC voltage Vb from the resonant frequency of the series resonant circuit.

  As described above, this is because when the absolute value of the AC voltage Va is small, the absolute value of the current flowing back to the AC power source 2 per unit time is small, and when the AC voltage Va is large, the AC value per unit time is AC. This is because the absolute value of the current flowing back to the power supply 2 is large.

  In the timing chart of the on / off states of the FETs 21 and 24 and the on / off state of the FETs 22 and 23 shown in FIG. 2, the first operation, the short-circuit operation, the second operation, and the short-circuit operation repeatedly performed by the inverter 12 are used. The period is constant, and the frequency is constant in the waveform of the AC voltage Vb shown in FIG.

  As described above, the conversion device 1 can convert the AC voltage Va to be converted applied by the AC power source 2 into the DC voltage Ve with a high power factor. Furthermore, since only the coil L1 is added to the configuration of the conversion device 1 to realize conversion with a high power factor, the device is small and inexpensive.

  In the present embodiment, the control unit 16 does not need to turn on all of the FETs 21, 22, 23, and 24 when causing the inverter 12 to perform a short-circuit operation. The control unit 16 may cause the inverter 12 to perform a short-circuit operation by turning on (or off) the FETs 21 and 22 and turning off (or on) the FETs 23 and 24.

  Furthermore, when all of the FETs 21, 22, 23, and 24 are on, the absolute value of the current that flows back to the AC power supply 2 is on (or off) for each of the FETs 21 and 22 and off (or for each of the FETs 23 and 24) ON) is larger than the absolute value of the current flowing back to the AC power source 2. Therefore, the control unit 16 performs a short-circuit operation realized by turning on all of the FETs 21, 22, 23, and 24, and turns on (or off) each of the FETs 21, 22 and turns off (or on) each of the FETs 23 and 24. The absolute value of the current flowing back to the AC power supply 2 may be adjusted in combination with the short-circuit operation realized by the above.

  Further, in the present embodiment, the control unit 16 does not need to adjust the period for causing the inverter 12 to perform the short-circuit operation according to the magnitude of the AC voltage Va output from the AC power supply 2. It may be constant.

  Further, the control unit 16 does not need to adjust the frequency of the AC voltage Vb converted by the inverter 12 according to the magnitude of the AC voltage Va output from the AC power supply 2. For example, the frequency of the AC voltage Vb is made constant. May be.

  Furthermore, the converter 1 does not necessarily need to include the capacitor C2. Even in this case, the converter 1 can convert the AC voltage Va output from the AC power source 2 into the DC voltage Ve with a high power factor.

  Further, the controller 16 does not have to repeatedly cause the inverter 12 to perform the short-circuit operation between the first and second operations. The short-circuit operation is appropriately omitted, and the first operation (or the second operation) is performed after the first operation (or the second operation). Two operations (or the first operation) may be performed by the inverter 12.

  Each of the FETs 21, 22, 23, and 24 included in the inverter 12 only needs to function as a semiconductor switch. Therefore, the FET 12 is not limited to an N-channel MOSFET, and may be a P-channel MOSFET, and may be a JFET (Junction Field Effect Transistor). ). Furthermore, the inverter 12 may use bipolar transistors instead of the FETs 21, 22, 23, and 24, respectively.

  The disclosed embodiments are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 1 Converter 11, 14 Rectifier circuit 12 Inverter 13 Transformer 16 Control part 21, 22, 23, 24 FET
C1, C2 Capacitor L1 Coil S1, S2 Input terminal Va, Vb AC voltage Ve DC voltage

Claims (4)

An inverter having an input terminal pair to which a DC voltage obtained by rectifying an AC voltage to be converted is applied, and converting the DC voltage applied between the input terminal pair into an AC voltage; and transforming the AC voltage converted by the inverter In a converter comprising: a transformer that performs, a rectifier circuit that rectifies an AC voltage transformed by the transformer into a DC voltage, and a control unit that controls the operation of the inverter.
A coil connected to one terminal of the input terminal pair;
The operation controlled by the control unit includes a short-circuit operation for short-circuiting the pair of input terminals. 2. The conversion device according to claim 1, wherein the control unit is configured to adjust a period during which the inverter performs the short-circuit operation according to an absolute value of the AC voltage to be converted. . A capacitor connected between the inverter and the transformer;
The said control part is comprised so that the frequency of the alternating voltage converted by the said inverter may be adjusted according to the absolute value of the alternating voltage of the said conversion object. The Claim 1 or Claim 2 characterized by the above-mentioned. Conversion device. The inverter includes a bridge circuit composed of a plurality of switches,
The converter according to any one of claims 1 to 3, further comprising a capacitor connected between the output terminal pair of the bridge circuit.

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