JP4961258B2 - Power converter - Google Patents

Description

  The present invention relates to a power conversion device that converts alternating current of a power source into direct current or alternating current of a variable voltage, and more particularly to a technique for reducing a loss of a semiconductor switching element constituting a power conversion circuit.

  2. Description of the Related Art In a power conversion device that converts an alternating current power supply voltage into direct current, an insulation type AC-DC converter that insulates an alternating current power supply and a load via a transformer or the like is known. As an example of such an insulated AC-DC converter, a one-stage converter having a power factor improving function described in FIG. According to this, a series circuit of two diodes, a series circuit of two bidirectional switches (a parallel circuit of a self-extinguishing semiconductor switch and a diode), and a capacitor are connected in parallel to each other, and two diodes are connected in series. An AC power supply is connected to the connection point and the series connection point of two bidirectional switches via an inductor, and a series circuit of a transformer, inductor and capacitor is connected in parallel to one bidirectional switch to form a main switching circuit. ing. A center tap diode rectifier circuit is provided on the secondary side of the transformer of the main switching circuit so as to be converted into a direct current and output.

  The control circuit that controls the main switching circuit of Patent Document 1 varies the frequency of the triangular wave so as to reduce the deviation between the command value and the detected value of the DC output voltage, and this triangular wave and a constant reference signal (for example, a triangular wave) Compared with 1/2 of the high value, the DC output voltage is controlled by controlling the switching frequency of the on / off signals of the two bidirectional switches. According to this, since a triangular wave-shaped input current flows according to the instantaneous value of the AC power supply voltage, an effect of improving the power factor can be obtained.

  FIG. 3 of Patent Document 1 shows a reference signal to be compared with a triangular wave so as to reduce a deviation between a command value and a detection value of a terminal voltage of a capacitor connected in parallel to a series circuit of two bidirectional switches. A control circuit is described that is variable to vary the on / off ratio of the two bidirectional switches.

  Further, in the main switching circuit described in FIG. 9 and FIG. 13 of Patent Document 1, first to third bidirectional switches are connected in series, and a series circuit of two diodes and a capacitor are connected in parallel to this series circuit. And an AC power source is connected via an inductor between the series connection point of the second and third bidirectional switches and the series connection point of the two diodes, and the second and third bidirectional switches are connected in series. A main switching circuit is configured by connecting a series circuit of a transformer, an inductor, and a capacitor in parallel with the circuit. A center tap diode rectifier circuit is provided on the secondary side of the transformer of the main switching circuit so as to be converted into a direct current and output. These bidirectional switching control circuits are divided into two groups, a first bidirectional switch and second and third bidirectional switches, and in accordance with the polarity of the AC voltage, as in the control circuit described above. It is configured to perform switching control alternately.

JP 2003-23775 A

  However, according to the control circuit of FIG. 1 of Patent Document 1, the on / off ratio of the two bidirectional switches is a constant ratio of 0.5: 0.5 regardless of the switching frequency. On the other hand, according to the control circuit of FIG. 3, the on / off ratios of the two bidirectional switches change. In any case, the input current of the converter of Patent Document 1 is an intermittent pulse waveform in the form of a triangular waveform in which a current substantially proportional to the instantaneous voltage of the power supply flows during the ON period of the bidirectional switch and decreases to zero during the OFF period. Current. If the zero period of the triangular pulse current is as short as possible, the current waveform obtained through the low-pass filter is a clean sine wave. However, since the switching frequency is changed in order to control the output DC voltage, there is a problem that a zero period of the triangular pulse current is generated and the input current waveform is distorted. Also, when the power is small, the power factor can be improved even in such a current intermittent mode, but the peak value of the triangular pulse current increases as the power increases. Therefore, a large core that does not saturate the inductor is required, and a large peak current is cut off. Therefore, there is a problem that switching loss of the switch circuit increases.

  These problems are not limited to insulating AC-DC converters, but are common to power converters that convert AC to a variable voltage while performing AC power factor improvement control of the power supply.

  The problem to be solved by the present invention is to provide a power converter capable of controlling the output power while improving the power factor in the continuous mode and reducing the switching loss related to power conversion. .

  In order to solve the above-described problem, a first aspect of the power conversion device of the present invention includes two switch circuits formed by connecting a semiconductor switching element and a diode in antiparallel, wherein the diodes are connected in series with opposite polarities. A first inductor inserted in series in a circuit that connects the first switch arm to the AC power supply in parallel, and a second switch arm in parallel with the first switch arm. An output having a first capacitor inserted in series with a circuit to be connected, and a series circuit of a second capacitor and a second inductor connected in parallel to one of the first switch arm and the second switch arm And a main switching circuit.

  With such a main switching circuit, by configuring the control circuit that controls on / off of each semiconductor switching element as follows, while controlling the output power while improving the power factor in the continuous mode, Switching loss related to power conversion can be reduced.

  That is, the control circuit for controlling on / off of each semiconductor switching element is based on the error between the output command value and the output detection value of the output circuit and the voltage polarity of the AC power supply, and the semiconductor switching elements (Q1) of the first and second switch arms. , Q2, Q3, Q4), the semiconductor switching elements (for example, Q1, Q3) responsible for input current and output control are alternately turned on and off, and the other semiconductor switching elements (Q2, Q4) are turned on. it can. Specifically, an error between the output command value of the output circuit and the output detection value is obtained, and the input current command value is generated by multiplying this error by the absolute value of the voltage detection value of the AC power supply. An error from the absolute value of the input current detection value from the input signal is obtained, and this error is compared with the PWM carrier wave to generate a PWM signal. Based on the PWM signal and the voltage polarity of the AC power supply, the first and second Of the semiconductor switching elements of the switch arm, the semiconductor switching elements responsible for input current and output control can be alternately turned on and off, and the other semiconductor switching element can be turned on.

  As described above, the semiconductor switching elements (for example, Q1 and Q3) of the first and second switch arms are alternately operated, and the other semiconductor switching elements (Q2 and Q4) are turned on, thereby reducing the input current to zero. The voltage or current output from the output circuit can be variably controlled while the power factor is improved in the continuous current mode without the above period. In addition, since it is not necessary to provide a large core inductor, the inductor can be miniaturized and the switching loss associated with power conversion can be reduced.

  In the first aspect, the output circuit includes a series circuit of a second capacitor and a second inductor including at least a primary winding of the transformer, and a rectifier circuit connected to the secondary winding of the transformer. The direct current rectified by the rectifier circuit can be output. In this case, the transformer includes two secondary windings, the rectification circuit includes two rectification circuits that rectify the voltages of the two secondary windings, respectively, and a third voltage that smoothes the output voltages of the two rectification circuits. A capacitor is provided, and the terminal voltage of the third capacitor can be a DC output.

  In the first aspect, an induction heating coil as a load can be used as the second inductor of the output circuit, and according to this, an AC output of a variable current can be obtained. The control circuit in this case detects an output current flowing in the induction heating coil instead of the output voltage of the output circuit of the control circuit, and an error between the detected output current and the output current command value is a first amplifying means. In this case, amplification may be performed.

  According to a second aspect of the power conversion device of the present invention, a rectification arm formed by connecting a first diode and a second diode in series in forward polarity, and a semiconductor switching element and a diode connected in antiparallel. And the second switch circuit includes a first switch arm in which the diodes are connected in series with opposite polarities, and a third switch circuit in which the semiconductor switching element and the diode are connected in antiparallel. A second switch arm having a capacitor connected in series; and an output circuit having a series circuit of a second capacitor and a second inductor; wherein the rectifying arm and the first switch arm are connected in parallel; The first inductor is connected between the connection point of the first diode and the second diode of the rectifying arm and the connection point of the first and second switch circuits of the first switch arm. An AC power supply is connected via a power supply, a series circuit of a second capacitor and a second inductor is connected in parallel to the rectifying arm and the first switch arm, and the second switch arm is connected to the rectifying arm and the A main switching circuit is configured in parallel with the rectifying arm or in parallel with the second inductor of the output circuit. Further, a control circuit for controlling on / off of each of the semiconductor switching elements is provided, and the control circuit performs semiconductor switching of the first and second switch circuits based on an output voltage error between an output command value of the output circuit and an output detection value. An output control system for turning on and off the element; an input current error between the input current command value generated by multiplying the output voltage error by a voltage detection value of the AC power supply and an input current detection value from the AC power supply; and the output voltage A power factor correction control system that turns on and off the semiconductor switching elements of the first and second switch circuits based on the error having the larger error, and at least one of the semiconductor switching elements of the first and second switch circuits is off. In this period, the semiconductor switching element of the third switch circuit is turned on. The output circuit can be configured in the same manner as in the first embodiment.

  According to the second aspect, the on / off control of the semiconductor switching elements of the first and second switch circuits is performed based on the larger error of the input current error and the output voltage error, so that the output is higher than that of the power factor correction control system. By controlling the (voltage or current) control system with priority, the output (voltage or current) is stabilized, and as a result, distortion of the input current waveform is also suppressed. Further, as in the first embodiment, the output power can be controlled while improving the power factor in the continuous mode in the input current, and the switching loss related to the power conversion can be reduced.

  According to the present invention, it is possible to control the output power while improving the power factor of the input current in the continuous mode, and to reduce the switching loss related to the power conversion.

  Hereinafter, embodiments of the power conversion device of the present invention will be described.

  In FIG. 1, the circuit block diagram of Example 1 formed by applying the 1st aspect which concerns on the power converter device of this invention is shown. As shown in FIG. 1, the switching circuit 10 includes a bidirectional switch circuit composed of two semiconductor switching elements Q1 and Q2 in which diodes D1 and D2 are connected in antiparallel, and diodes D1 and D2 with opposite polarities. A bidirectional switch circuit composed of two semiconductor switching elements Q3 and Q4 in which the first bidirectional switch arm connected in series and the diodes D3 and D4 are connected in antiparallel, and the diodes D3 and D4 are reversed. And a bidirectional second switch arm connected in series with the polarity.

  The first switch arm is connected in parallel to the AC power supply AC via the inductor L1. The second switch arm is connected in parallel to the first switch arm via the capacitor C1. In addition, a series circuit of an inductor L2, a primary winding of the transformer T1, and a capacitor C2 is connected in parallel to the first switch arm. This series circuit may be connected in parallel to the second switch arm. The inductor L2 can also use the leakage inductance of the transformer T1.

  Two secondary windings N2 and N3 are provided in the transformer T1. In each of the secondary windings N2 and N3, the voltage rectified by the diodes D5 and D6 is smoothed by the capacitor C3, and a DC voltage is output to the load RL. The output circuit of this embodiment includes a rectifier circuit including a series circuit of an inductor L2, a primary winding of a transformer T1, and a capacitor C2, secondary windings N2 and N3 of the transformer T1, diodes D5 and D6, and a capacitor C3. It is configured to include.

  The switching circuit 10 including the first and second switch arms is driven by a drive circuit 75. The drive circuit 75 amplifies the drive signals Q1 to Q4-Duty output from the control circuit and controls on / off of the semiconductor switching elements Q1 to Q4.

  The control circuit of this embodiment includes an input voltage detection circuit 71, a current sensor 73, an input current detection circuit 74, a positive / negative discrimination circuit 76, an output voltage detection circuit 72, a PWM signal generation circuit 94, and a drive signal generation circuit 97. Has been.

  The input voltage detection circuit 71 detects the AC voltage of the AC power supply AC and inputs it to the absolute value circuit 91. The absolute value circuit 91 calculates an absolute value of the AC voltage detection value and inputs it to the multiplier 78. The current sensor 73 detects an input current flowing through the AC power supply AC and inputs the detected current to the input current detection circuit 74. The input current detection circuit 74 inputs the input current to the absolute value circuit 92. The absolute value circuit 92 obtains the absolute value of the input current detection value and inputs it to the amplifier 79. The positive / negative discrimination circuit 76 outputs a signal “H” when the output of the input voltage detection circuit 71 is positive, and outputs an “L” signal when it is negative.

  The output voltage detection circuit 72 detects the terminal voltage of the capacitor C3 of the output circuit, and inputs the output voltage detection value to the comparison amplifier 77. The comparison amplifier 77 compares the output voltage command value with the output voltage detection value to obtain an error, amplifies the error, and inputs the error to the multiplier 78. The multiplier 78 multiplies the error between the output voltage command value and the output voltage detection value by the absolute value of the AC voltage detection value, and inputs it to the comparison amplifier 79 as an input current command value. The comparison amplifier 79 compares the input current command value input and the absolute value of the input current detection value to obtain an error, amplifies the error, and inputs the error to the PWM signal generation circuit 94.

  The PWM signal generation circuit 94 compares the error between the input current command value output from the comparison amplifier 79 and the input current detection value with the PWM carrier wave, generates a PWM signal, and inputs the PWM signal to the drive signal generation circuit 97. The drive signal generation circuit 97 includes a plurality of logic gates, and generates drive signals Q1 to Q4-Duty of the switching elements Q1 to Q4 based on the PWM signal input from the PWM signal generation circuit 94. That is, the switching elements Q <b> 1 to 1 of the first and second switch arms are matched to the half cycle of positive “H” and negative “L” of the AC power supply AC output from the positive / negative discrimination circuit 76. Drive which turns on / off switching elements (Q1, Q3) or (Q2, Q4) responsible for input current and output control among Q4 and turns on the other switching elements (Q2, Q4) or (Q1, Q3) Generate a signal.

  The operation of the first embodiment configured as described above will be described next. FIG. 2 shows the voltage V (AC) and input current I (AC) of the AC power supply AC and the drive signal of each switching element of the switching circuit 10. When the voltage polarity of AC power supply AC is positive, drive signal generation circuit 97 turns on switching elements Q2 and Q4 and turns on and off switching elements Q1 and Q3 alternately. Conversely, when the polarity is negative, the switching elements Q1 and Q3 are turned on, and the switching elements Q2 and Q4 are alternately turned on and off.

  FIG. 3 shows the drive signal of each switching element, the element current, the current of the inductor L1, and the current waveform I (D5) of the secondary side rectifier diode D5 when the voltage polarity of the AC power supply AC is positive. When switching element Q1 is turned on, current I (Q1) flows through the path of AC-L1-Q1-Q2, and energy I (L1) is accumulated in inductor L1. On the other hand, on the DC-DC converter side, current I (Q2) flows through the path C2-N1-L2-Q1-Q2 by the accumulated charge of the capacitor C2, and energy is accumulated in the transformer T1. Here, the switching element Q2 has a synchronous rectification operation, and the conduction loss can be reduced by using a MOSFET having a super junction structure with a low on-resistance even with a high breakdown voltage.

  Next, when Q1 is turned off, the circulating current flows through the path L1-Q4-D3-C1-AC and the path L2-Q4-D3-C1-C2-N1 by the energy stored in the inductors L1 and L2. When Q3 is turned on during this period, current I (Q3) flows through the path L1-Q4-Q3-C1-AC and the path L2-Q4-Q3-C1-C2-N1. Since Q3 is turned on when D3 is in a conductive state, that is, when the element voltage is zero volts, a zero-volt switching (hereinafter referred to as ZVS) operation is performed and no turn-on loss occurs.

  On the other hand, on the secondary side, current flows through the path N2-D5-C3 by the energy stored in the transformer T1, and power is supplied to the output side by the flyback operation. As described above, when the AC voltage polarity is positive, power is transferred between N1 and N2. When the stored energy of L2 becomes zero, the current continues to flow through the path of AC-L1-L2-N1-C2 by the stored energy of L1. On the other hand, on the DC-DC converter side, current I (Q3) flows through the path C1-Q3-Q4-L2-N1-C2 due to the accumulated charge in the capacitor C1. Next, when Q3 is turned off, a current flows through the path of L2-N1-C2-Q2-D1 by the stored energy of L2, and ZVS operation can be realized by turning on Q1 during this time.

  When the stored energy of L2 becomes zero, the mode returns to the above-described mode in which energy is stored in L1 and T1, and thereafter this operation is repeated while the AC voltage polarity is positive. When the voltage polarity of AC is negative, the roles of switching elements Q1 and Q3 and Q2 and Q4 are changed, and power is transferred between N1 and N3 of transformer T1. As described above, in the continuous current mode in which the current of L1 continuously flows, the switching elements Q1 to Q4 can be driven by the ZVS operation by using the energy stored in the inductor L2.

  As described above, in this embodiment, based on the output voltage command value obtained by the comparison amplifier 77, the output voltage error between the detected output voltage values, and the voltage polarity of the AC power source output from the positive / negative discrimination circuit 76, Of the semiconductor switching elements (Q1, Q2, Q3, Q4) of the first and second switch arms, the semiconductor switching elements (for example, Q1, Q3) responsible for input current and output control are alternately turned on and off, and the other semiconductor switching element Since (Q2, Q4) is turned on, the output voltage, which is the terminal voltage of the capacitor C3, can be variably controlled while improving the power factor in the current continuous mode without the period in which the input current becomes zero. it can. In addition, since it is not necessary to provide a large core inductor, the inductor can be miniaturized and the switching loss associated with power conversion can be reduced.

  In this embodiment, even if the series circuit of the inductor L2, the primary winding N1, and the capacitor C2 is connected in parallel to the second bidirectional switch arm, the current of L1 flows continuously in the same manner as described above. The ZVS operation of the switching element is possible.

  Although not shown in FIG. 1, by applying a snubber capacitor to each switching element Q1 to Q4, the snubber capacitor is charged or discharged by a cut-off current at the time of turn-off of each switching element. The turn-off loss can be reduced by suppressing the change of the applied voltage. The same effect can be obtained even if the snubber capacitor is connected between the first and second switch arms.

  In FIG. 1, a MOSFET is used as the switching element, but an IGBT or a transistor can be used instead.

  Further, the first or second switch arm may be constituted by a power semiconductor switching element with a reverse withstand voltage function connected in antiparallel.

  Furthermore, the diodes D5 and D6 may be replaced with a synchronous rectifier circuit using a MOSFET.

  In this embodiment, the second switch arm is connected in parallel to the first switch arm via the capacitor C1, but the capacitor C1 side is connected to the connection point between the transformer T1 and the capacitor C2. You may make it do. That is, the second switch arm may be connected in parallel to the series circuit of the inductor L2 and the transformer T1 via the capacitor C1.

  In FIG. 4, the circuit block diagram of Example 2 formed by applying the 1st aspect which concerns on the power converter device of this invention is shown. As shown in FIG. 4, the present embodiment is different from the first embodiment in that AC power is converted into AC power. The same parts as those in FIG.

  The present embodiment is an example of a power converter that applies high-frequency alternating current to the induction heating coil Lr and electromagnetically heats a metallic object to be heated. Although not shown, the object to be heated is magnetically coupled to the induction heating coil Lr.

  As shown in the figure, the output circuit of this embodiment is composed of a series circuit of a second capacitor C2 and an induction heating coil Lr. Then, the output current flowing through the induction heating coil Lr is detected by the current sensor 80 and the output current detection circuit 81, and an error from the output current command is obtained and amplified by the comparison amplifier 77, and the switching element is reduced so as to reduce this error. Q1 to Q4 are subjected to switching control.

  Therefore, according to the present embodiment, the same effect as in the first embodiment can be obtained, and the output current supplied from the induction heating coil Lr can be controlled to the command value.

  In FIG. 5, the circuit block diagram of Example 3 formed by applying the 2nd aspect which concerns on the power converter device of this invention is shown. As shown in FIG. 5, the rectifying arm is formed by connecting a diode D11 and a diode D12 in series with a forward polarity. The first switch arm is composed of first and second switch circuits formed by connecting semiconductor switching elements Q1 and Q2 and diodes D1 and D2 in antiparallel, and the diodes D1 and D2 are connected in series with opposite polarities. Is formed. The second switch arm is formed by connecting a capacitor C1 in series to a third switch circuit formed by connecting a semiconductor switching element Q3 and a diode D3 in antiparallel.

  The rectifying arm and the first and second switch arms are connected in parallel to each other. A switching circuit 10 is formed by the first and second switch arms. An AC power supply AC is connected via an inductor L1 between a connection point between the diode D11 and the diode D12 of the rectifying arm and a connection point of the switching elements Q1 and Q2 of the first switch arm.

  In addition, a series circuit of an inductor L2, a primary winding of the transformer T1, and a capacitor C2 is connected in parallel to the first switch arm. The inductor L2 can also use the leakage inductance of the transformer T1. The transformer T1 is provided with a secondary winding N2. In the secondary winding N2, the voltage rectified by the diode D5 is smoothed by the capacitor C3, and a DC voltage is output to the load RL. The diode D5 may be replaced with a synchronous rectifier circuit using a MOSFET.

  A control circuit that controls on / off of each switching element Q1 to Q3 of the switching circuit 10 includes an output voltage detection circuit 72 that detects a terminal voltage of the capacitor C3, an output voltage detection value detected by the output voltage detection circuit 72, and an output voltage command. A comparison amplifier 77 that obtains and amplifies the output voltage error from the value and a first PWM signal generation circuit 96 that generates the PWM signal by comparing the output voltage error and the PWM carrier wave are provided.

  Further, an input voltage detection circuit 71 that detects an input voltage of the AC power supply AC, a current sensor 73 that detects an input current, and an input current detection circuit 74 are provided. The input voltage detection circuit 71 detects the AC voltage of the AC power supply AC and inputs it to the absolute value circuit 91. The absolute value circuit 91 calculates an absolute value of the AC voltage detection value and inputs it to the multiplier 78. The current sensor 73 detects an input current flowing through the AC power supply AC and inputs the detected current to the input current detection circuit 74. The input current detection circuit 74 inputs the input current to the absolute value circuit 92. The absolute value circuit 92 obtains the absolute value of the input current detection value and inputs it to the amplifier 79. The positive / negative discrimination circuit 76 outputs a signal “H” when the output of the input voltage detection circuit 71 is positive, and outputs an “L” signal when it is negative.

  The control system that generates drive signals for the switching elements Q1 to Q3 of this embodiment includes an output voltage control system 95 and a power factor correction control system 90. The output voltage control system 95 includes a first PWM signal generation circuit that compares the output voltage error obtained by the comparison amplifier 77 with a PWM carrier wave to generate a PWM signal. On the other hand, the power factor correction control system 90 includes a multiplier 78 that multiplies the output voltage error output from the comparison amplifier 77 by the absolute value of the AC voltage detection value output from the absolute value circuit 91. The output of the multiplier 78 is input to the comparison amplifier 79 as an input current command value. The comparison amplifier 79 compares the input current command value input and the absolute value of the input current detection value output from the absolute value circuit 92 to obtain and amplify the input current error. The input current error output from the comparison amplifier 79 is input to the maximum value circuit 93. The maximum value circuit 93 compares the input current error output from the comparison amplifier 79 with the output voltage error output from the comparison amplifier 77, and inputs the larger one to the second PWM signal generation circuit 94. ing. The PWM signal generation circuit 94 compares the output voltage error or input current error output from the maximum value circuit 93 with the PWM carrier wave, and generates a PWM signal.

  The PWM signals generated by the PWM signal generation circuit 94 and the PWM signal generation circuit 96 are input to the drive signal generation circuit 97, respectively. The drive signal generation circuit 97 includes a plurality of logic gates, and generates drive signals Q1 to Q3-Duty of the switching elements Q1 to Q3 based on the PWM signals input from the PWM signal generation circuits 94 and 96. That is, the switching elements Q1 and Q2 of the first switch arm are turned on / off in accordance with the half cycle in which the voltage polarity of the AC power supply AC output from the positive / negative discrimination circuit 76 is positive “H” and negative “L”. When at least one of the switching elements Q1 and Q2 is off, a drive signal for turning on the switching element Q3 of the second switch arm is generated.

  Next, the operation of the third embodiment configured as described above will be described. In the first embodiment, the power factor improvement control and the output voltage control switching elements cannot be controlled separately. Therefore, if priority is given to the power factor correction control, the fluctuation of the output voltage becomes large, and if priority is given to the output voltage control, the input current waveform is distorted and a sinusoidal waveform cannot be obtained. That is, FIG. 6 shows operation waveforms when the control circuit of the first embodiment is applied to the present embodiment. In the figure, the voltage of the AC power supply AC is V (AC), the input current is I (AC), the output voltage is V (C3), the voltage of the amplifier 77 is V (77), and the voltage of the amplifier 79 is V (79). Represented by In the figure, the increase / decrease relationship of the error amount V (79) of the input current waveform does not match the error amount V (77) of the output voltage during the period indicated by the arrow. That is, since power factor improvement control and output voltage control cannot be compatible, the input current I (AC) is also distorted and the output voltage V (C3) fluctuates as a result.

  Therefore, in this embodiment, when the voltage polarity of the AC power supply AC is positive, the switching element Q1 is controlled as a main element for input current waveform control, that is, power factor correction control, and the switching element Q2 is controlled as a main element for output voltage control. I am doing so. For this reason, the functions of the input current waveform control and the output voltage control can be made compatible. When the voltage polarity of the AC power supply AC is negative, the performance can be similarly satisfied by changing the roles of the switching elements Q1 and Q2.

  Specifically, in this embodiment, a maximum value circuit 93 that outputs the maximum values of the comparison amplifier 77 and the comparison amplifier 79 is provided as a power factor improvement control system 90 in the previous stage of the PWM signal generation circuit 94, and The difference from the first embodiment is that a PWM signal generation circuit 96 that generates a PWM signal based on the output of the comparison amplifier 77 is provided as the output voltage control system 95.

  The PWM signal generation circuits 94 and 96 each output a PWM signal in synchronization with the synchronization signal. The drive signal generation circuit 97 generates drive signals Q1 to Q3 based on the outputs of the PWM signal generation circuits 94 and 96 and the positive / negative discrimination circuit 76. In the present embodiment, the output voltage control system 95 is prioritized over the power factor improvement control system 90 to control the switching elements Q1 and Q2, and a system for performing power factor improvement control outside thereof is constructed.

  FIG. 7 is an operation waveform of this embodiment shown in comparison with FIG. 6. The voltage of the AC power supply AC is V (AC), the input current is I (AC), the output voltage is V (C3), and the amplifier 77. Is represented by V (77), and the voltage of the amplifier 79 is represented by V (79). In the figure, since the switching elements Q1 and Q2 are controlled with priority given to the output voltage error V (77), the output voltage V (C3) is stabilized, and as a result, distortion of the input current I (AC) is also suppressed. Waveform is obtained.

  FIG. 8 shows the drive signal of each switching element, the element current, the currents of the inductors L1 and L2, and the current waveform of the secondary rectifier diode D5 when the voltage polarity of the AC power supply AC is positive. When the switching elements Q1 and Q2 are in the ON state, the transformer T2 passes through the path C2-N1-L2-Q1-Q2 by the current stored in the inductor L1 through the path AC-L1-D11-Q1 and the accumulated charge in the capacitor C2. A current that accumulates energy flows through.

  In the present embodiment, as described above, the switching element Q1 is controlled as the main element for controlling the input current waveform, and the switching element Q2 is controlled as the main element for controlling the output voltage. Therefore, power factor improvement control and output voltage control are established under the condition that the timing when Q1 is turned off is later than the timing when Q2 is turned off. That is, the output voltage is controlled when both Q1 and Q2 are on, and the input current waveform is controlled when Q1 is on and Q2 is off. When Q2 is turned off, a circulating current flows through the path L2-D3-C1-C2-N1 by the energy stored in the inductor L2. If Q3 is turned on during this time, the circulating current flows through the path of L2-Q3-C1-C2-N1, so that Q3 is in a synchronous rectification operation. If a MOSFET with a super junction structure having a high on-resistance and a low on-resistance is used, the conduction loss is reduced. Get smaller. Since Q3 is turned on when D3 is in a conductive state, that is, when the element voltage is zero volts, it becomes a ZVS operation and no turn-on loss occurs.

  On the other hand, on the secondary side, current flows through the path N2-D5-C3 by the energy stored in the transformer T1, and power is supplied to the output side by the flyback operation. If the stored energy of L2 becomes zero before Q1 is turned off, a current flows through the path C1-Q3-L2-N1-C2 due to the stored charge of the capacitor C1. Next, when Q1 is turned off, the current of L1 continues to flow due to the energy stored in the inductor L1, but the current path is blocked by the inductor L2, so that the current flows through the path of L1-D11-Q3-C1-D2-AC. Flowing. When the current of the inductor L2 reaches the current of the inductor L1, the current continues to flow through the path of AC-L1-D11-L2-N1-C2-D2 by the stored energy of L1.

  On the other hand, on the DC-DC converter side, current flows through a path of C1-Q3-L2-N1-C2 due to the accumulated charge of the capacitor C1. Next, when Q3 is turned off, a current flows through the path of L2-N1-C2-D2-D1 by the stored energy of L2, and ZVS operation can be realized by turning on Q1 and Q2 during this time.

  As shown in FIG. 9, Q2 can be synchronously rectified by turning on Q2 in synchronization with the off timing of Q1. When the stored energy of L2 becomes zero, the mode returns to the above-described mode in which energy is stored in L1 and T1, and thereafter this operation is repeated while the AC voltage polarity is positive. When the AC voltage polarity is negative, switching elements Q1 and Q2 alternate roles. As described above, in the continuous current mode in which the current of L1 continuously flows, the switching elements Q1 to Q3 can be driven by the ZVS operation by using the energy stored in the inductor L2.

  As described above, according to the present embodiment, as in the first embodiment, it is possible to control the output power while improving the power factor of the input current in the continuous mode, and to reduce the switching loss related to the power conversion. it can.

  In particular, according to the present embodiment, on / off control of the semiconductor switching element Q1 (or Q2) is performed on the basis of the larger one of the input current error and the output voltage error, thereby controlling the output voltage more than the power factor improvement control system. By controlling the system with priority, the output voltage is stabilized, and as a result, distortion of the input current waveform can also be suppressed.

  In FIG. 10, the circuit block diagram of Example 4 formed by applying the 2nd aspect which concerns on the power converter device of this invention is shown. The same parts as those in FIG. 5 are denoted by the same reference numerals, and description thereof is omitted. In FIG. 10, the difference from the third embodiment is that a series circuit of a switching element Q3 and a capacitor C1 is connected in parallel to a series circuit of an inductor L2 and a primary winding N1. The operation is almost the same as in the third embodiment, except that the circulating current of the inductor L1 flows through the capacitor C2 and that the capacitor C2 does not enter the path through which the current of the inductor L2 flows through Q3 or D3.

  The configuration of this embodiment can also be applied to the first embodiment.

  In FIG. 11, the circuit block diagram of Example 5 formed by applying the 2nd aspect which concerns on the power converter device of this invention is shown. As shown in FIG. 11, the present embodiment is different from the third embodiment in that AC power is converted into AC power. The same parts as those in FIG.

  The present embodiment is an example of a power converter that applies high-frequency alternating current to the induction heating coil Lr and electromagnetically heats a metallic object to be heated. Although not shown, the object to be heated is magnetically coupled to the induction heating coil Lr.

  As shown in the figure, the output circuit of this embodiment is composed of a series circuit of a second capacitor C2 and an induction heating coil Lr. Then, the output current flowing through the induction heating coil Lr is detected by the current sensor 80 and the output current detection circuit 81, and an error from the output current command is obtained and amplified by the comparison amplifier 77, and the switching element is reduced so as to reduce this error. Switching control is performed on Q1 to Q3.

  Therefore, according to the present embodiment, the same effect as in the third embodiment can be obtained, and the output current supplied from the induction heating coil Lr can be controlled to the command value. The same parts as those in FIG. 5 are denoted by the same reference numerals, and description thereof is omitted. The operation is the same as the operation on the primary side in the third embodiment, and a description thereof is omitted.

  The present invention relates to an insulated AC-DC that receives an AC power source for home appliances, consumer electronics, and business use, an induction heating cooker used for general home use and business use, hot water generation, low-temperature / high-temperature steam generation device, metal It can be used as a power source for a wide variety of heat sources, such as melting of toner and thermal transfer roller drums for fixing toner in copying machines.

It is a circuit block diagram of the power converter device which applies the 1st aspect of Example 1 of this invention. 2 is an operation waveform according to the first embodiment. FIG. 3 is an explanatory diagram of an operation mode according to the first embodiment. It is a circuit block diagram of the power converter device which applies the 1st aspect of Example 2 of this invention. It is a circuit block diagram of the power converter device which applies the 2nd aspect of Example 3 of this invention. FIG. 10 is a diagram for explaining a control operation according to a fourth embodiment. FIG. 10 is a diagram for explaining a control operation according to a fourth embodiment. FIG. 10 is an explanatory diagram of an operation mode according to the fourth embodiment. FIG. 10 is an explanatory diagram of an operation mode according to the fourth embodiment. It is a circuit block diagram of the power converter device which applies the 2nd aspect of Example 4 of this invention. It is a circuit block diagram of the power converter device which applies the 2nd aspect of Example 5 of this invention.

Explanation of symbols

  AC ... AC power supply, L1, L2 ... Inductor, Q1-Q4 ... Switching element, D1-D6, D11, D12 ... Diode, C1-C3 ... Capacitor, T1 ... Transformer, N1-N3 ... Winding, 10 ... Switching circuit, Lr ... induction heating coil, 71 ... input voltage detection circuit, 72 ... output voltage detection circuit, 73, 80 ... current sensor, 74 ... input current detection circuit, 75 ... drive circuit, 76 ... positive / negative discrimination circuit, 77, 79 ... comparison Amplifier, 78 ... Multiplier, 81 ... Output current detection circuit, 90 ... Power factor correction control system, 91, 92 ... Absolute value circuit, 93 ... Maximum value circuit, 94, 96 ... PWM signal generation circuit, 95 ... Output voltage control 97, drive signal generation circuit

Claims (7)

Two switch circuits formed by connecting semiconductor switching elements and diodes in antiparallel include first and second switch arms in which the diodes are connected in series with opposite polarities, and the first switch arms are connected to an AC power source. A first inductor inserted in series in a circuit connected in parallel to the first switch, a first capacitor inserted in series in a circuit connected in parallel with the second switch arm to the first switch arm, and a first switch arm And an output circuit having a series circuit of a second capacitor and a second inductor connected in parallel to either one of the second switch arm and a control circuit for controlling on / off of each of the semiconductor switching elements,
The control circuit is responsible for input current and output control among the semiconductor switching elements of the first and second switch arms based on the error between the output command value and output detection value of the output circuit and the voltage polarity of the AC power supply. A power conversion device, wherein semiconductor switching elements are alternately turned on and off, and the other semiconductor switching element is turned on . The power conversion device according to claim 1 ,
The control circuit obtains an error between the output command value of the output circuit and the output detection value, and multiplies the error by the absolute value of the voltage detection value of the AC power supply to generate an input current command value. And the absolute value of the input current detection value from the AC power supply, and the error is compared with a PWM carrier wave to generate a PWM signal. Based on the PWM signal and the voltage polarity of the AC power supply A power conversion device characterized in that, among the semiconductor switching elements of the first and second switch arms, a semiconductor switching element responsible for input current and output control is alternately turned on and off, and the other semiconductor switching element is turned on. The power conversion device according to claim 1,
The output circuit includes a series circuit of a second capacitor and a second inductor including at least a primary winding of a transformer, and a rectifier circuit connected to the secondary winding of the transformer, and is rectified by the rectifier circuit. A power converter characterized by having a direct current as an output. The power conversion device according to claim 3 ,
The transformer comprises two secondary windings,
The rectifier circuit includes two rectifier circuits that rectify the voltages of the two secondary windings, respectively, and a third capacitor that smoothes the output voltage of the two rectifier circuits, and the terminal voltage of the third capacitor Is a DC output. The power conversion device according to claim 3 ,
The control circuit includes an input voltage detection circuit that detects an input voltage of the AC power supply, an input current detection circuit that detects an input current, an output voltage detection circuit that detects an output voltage of the output circuit, and the output voltage detection A first comparison means for obtaining an error between the output voltage detection value detected by the circuit and the output voltage command value; an output of the first comparison means; and an absolute value of the input voltage detection value detected by the input voltage detection circuit Input current command means for generating an input current command value based on the input current, second comparison means for obtaining an error between the absolute value of the input current detection value detected by the input current detection circuit and the input current command value, A PWM signal generation circuit for generating a PWM signal by comparing the output of the comparison means and the PWM carrier wave, and the PWM signal output from the PWM signal generation circuit and the input voltage detection circuit A drive signal generation circuit that generates a drive signal for each of the semiconductor switching elements according to the voltage polarity of the AC power supply, the drive signal generation circuit corresponding to the voltage polarity of the semiconductor switching elements of the switch arms. A power conversion device, wherein a semiconductor switching element responsible for input current and output control is turned on / off by the PWM signal, and a drive signal for turning on the other semiconductor switching element is generated. The power conversion device according to claim 1,
The output circuit is a series circuit of a second capacitor and a second inductor including at least an induction heating coil, and outputs an alternating current flowing through the induction heating coil. The power converter according to claim 6,
The control circuit includes an input voltage detection circuit that detects an input voltage of the AC power supply, an input current detection circuit that detects an input current, an output current detection circuit that detects an output current of the output circuit, and the output current detection A first comparing means for obtaining an error between the output current detected value detected by the circuit and the output current command value; an output of the first comparing means; and an absolute value of the input voltage detected value detected by the input voltage detecting circuit Input current command means for generating an input current command value based on the input current, second comparison means for obtaining an error between the absolute value of the input current detection value detected by the input current detection circuit and the input current command value; A PWM signal generation circuit for generating a PWM signal by comparing the output of the second comparison means and the PWM carrier wave, and a PWM signal output from the PWM signal generation circuit and detected by the input voltage detection circuit A drive signal generation circuit for generating a drive signal for each semiconductor switching element of the first and second switch arms based on the voltage polarity of the AC power supply, and the drive signal generation circuit includes a semiconductor for each of the switch arms. A power conversion device generating a drive signal for turning on / off a semiconductor switching element responsible for input current and output control according to the voltage polarity among the switching elements with the PWM signal and turning on the other semiconductor switching element.

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