JP2013192340A - Power conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power conversion device having improved versatility using a switching element for use in a circuit not restricted to a specific element, with the reduction of a current detection point to one point.SOLUTION: A first current value is detected in a period when the switching elements 105a and 105b are in on states or off states. A difference, which is a target current value, between the first current value and a second current value is converted into a first voltage value having a scale that can be compared with the peak value of a triangle wave, a carrier wave, so as to be compared with the triangle wave peak value. The power conversion device includes a PFC control unit 110 for driving switching elements 105a and 105b, on the basis of a pulse width modulation signal generated by the comparison between the first voltage value and the triangle wave peak value.

Description

  The present invention relates to a power conversion apparatus using a power factor correction (abbreviated as PFC) circuit.

  FIG. 8 is an electric circuit diagram showing a configuration of a conventional power converter 200, and this conventional technique is described in, for example, Patent Document 1. Power factor correction (abbreviated as PFC) circuit that suppresses harmonic currents caused by semiconductor control using semiconductor elements such as thyristors and triacs and improves power factor is an inductor, diode bridge, high-speed diode, switching A current value flowing through the circuit is detected, compared with a reference current, and a pulse width modulation (abbreviated as PWM) signal is input to each of the switching elements. By the switching operation by these switching elements, the voltage and current output to each output terminal are shaped into a target waveform.

  Of the PFC control circuit 211, a bridgeless circuit that improves power factor without using a diode bridge is particularly effective in reducing conduction loss and improving power factor. As an example, Patent Document 1 is cited. The power converter 200 shown in FIG. 8 includes first and second outputs to which a commercial AC power supply 201 is connected and to which an AC power supply voltage is applied, and first and second input terminals P11 and P12 and a load 208 are connected. Terminals P21, P22, inductor 202, first rectifier diode 203a, second rectifier diode 203b, first switching element 204a, second switching element 204b, first detection diode 205a, second detection Diode 205b, first current detection resistor 206a, second current detection resistor 206b, smoothing capacitor 207, input voltage detection circuit 209, output voltage detection circuit 210, and PFC control circuit 211.

  In such a power conversion device 200, current detection is performed at two locations of the first current detection resistor 206a and the second current detection resistor 206b every half cycle. Then, the first switching element 204a and the second switching element 204b are controlled by a pulse width modulation (abbreviation: PWM) signal from the PFC control circuit 211 to improve the power factor.

  However, since the bridgeless power conversion device 200 needs to detect current at the lower stage of each of the switching elements 204a and 204b, the cost is high and a complicated control method is required for current detection. Therefore, a low-cost and simple control method is required. Another conventional technique for solving such a problem of the conventional technique is described in Patent Document 2, for example.

  FIG. 9 is an electric circuit diagram showing another conventional power conversion device 200a. Note that the same reference numerals are given to the portions corresponding to the above-described conventional technology. In this conventional power conversion device 200a, the PFC control circuit 211, the first inductor 212a, the second inductor 212b, and the first switching element 213a and IGBT realized by an IGBT (Insulated Gate Bipolar Transistor) are realized. A second switching element 213b, a first high speed diode 205a, and a second high speed diode 205bb are provided.

  The PFC control circuit 211 is configured to obtain a similar waveform by inputting a signal synchronized with the AC power supply 201 to the multiplier. The difference between the similar waveform and the voltage generated in each of the first and second switching elements 213a and 213b and the shunt resistor 214 connected in series with the first and second diodes 205a and 205b connected in parallel. The sine wave is controlled so that becomes zero. At this time, in the shunt resistor 214, when the first and second switching elements 213a and 213b are in the OFF state and in the ON state with respect to the current output from the low level signal line and the high level signal line of the AC power supply 201. In this case, current detection is performed for each of two situations. Such a method is a means that can be used only for switching when an IGBT is used as each of the switching elements 213a and 213b.

JP 2011-152017 A JP 2003-158878 A

  As in the prior art described in Patent Document 1, in the bridgeless power converter, it is necessary to detect at least two current values in order to control the circuit operation. Therefore, there is a problem that the control circuit becomes complicated and the detection circuit cost increases.

  In addition, in another conventional technique described in Patent Document 2, a technique for performing control by detecting a current value at one place has been proposed, but a switching element of an FET (Field Effect Transistor) that is not an IGBT is used. When used, the current value cannot be detected by a diode, so that the switching element used in the circuit is limited to a specific element, and there is a problem that versatility is low.

  An object of the present invention is to solve the above-described problems, to reduce the number of current detection points to one, and to provide a power conversion device with improved versatility that does not limit a switching element used in a circuit to a specific element. .

The present invention includes an AC voltage input unit to which a commercial AC power supply is connected,
A rectifying unit that includes a switching element driven by a pulse width modulation signal, and that converts an AC voltage input to the AC voltage input unit into a DC voltage;
An output current detector for detecting a current value of an output current of the rectifier in an on state or an off state of the switching element;
A difference between a first current value that is a current value detected by the output current detection unit and a second current value that is a predetermined target current value can be compared with a peak value of a triangular wave that is a carrier wave. A pulse that is converted into a voltage value of 1 and compared with the peak value of the triangular wave, and generates a pulse width modulation signal for driving the switching element based on the comparison result between the first voltage value and the peak value of the triangular wave It is a power converter characterized by including a width modulation signal generation part.

  Further, the present invention is characterized in that the second current value is a current reference value converted on the basis of the output voltage of the rectifying unit and the input voltage of the AC voltage input unit. Hereinafter, the current reference value is referred to as a reference.

  Further, the present invention is characterized in that the output current detection unit detects the current when the switching element is in an OFF state.

  In the invention, it is preferable that the pulse width modulation signal generation unit outputs an off signal of the switching element at a timing when a peak value of the triangular wave exceeds the first voltage value.

According to the present invention, the output current detector is a current transformer.
The rectifying unit may be a bridgeless power factor correction circuit or an interleaved power factor correction circuit.

  According to the present invention, the first current value when the switching element is in the on state or the off state is detected, and an error value between the first current value and the second current value that is the target current value is a carrier wave. The pulse width modulation signal generated by comparing the first voltage value with the triangular wave peak value is converted into a first voltage value on a scale comparable to the triangular wave peak value and compared with the triangular wave peak value. Since the switching element is configured to be driven based on this, the number of current value detection means can be reduced as compared with the conventional power converter. The types of switching elements that can be used are not limited, and the current can be detected with a simple configuration without complicating the circuit configuration.

  As a result, the number of current detection points can be reduced to one, and the cost can be reduced. In terms of control, high power factor and efficiency can be realized without requiring complicated control. Furthermore, even if not only IGBT but also low-cost MOSFET is used as a switching element, appropriate control can be performed, and the power factor can be improved without being limited to a specific switching element.

  According to the present invention, the second current value is a reference value converted from the output voltage of the DC output terminal and the input voltage of the AC voltage input unit, so that the power factor can be improved efficiently. It becomes.

  Further, according to the present invention, the first current value detecting means detects a current at a timing when the switching element is turned off, and the PWM signal has a peak value of the triangular wave equal to the first voltage value. By outputting an off signal of the switching element at a timing exceeding, it is possible to further reduce the number of first current value detection means, that is, current detection units, as compared with the case of detecting the on signal of the switching element. Is possible.

  According to the present invention, since the first current value detecting means is realized by a current transformer, the current can be easily detected.

  According to the present invention, the rectifier circuit is a bridgeless power factor correction circuit or an interleaved power factor correction circuit, so that the effect of reducing the number of first current value detection means and the number of current detection units is great. Thus, the cost can be further reduced.

1 is an electric circuit diagram illustrating a configuration of a power conversion device 100 according to an embodiment of the present invention. Is a diagram showing the flow of current _{I A} in PFC control circuit B of the power conversion apparatus 100 shown in FIG. Is a diagram showing the flow of current _{I B} in the PFC control circuit B of the power conversion apparatus 100 shown in FIG. 6 is a waveform diagram showing a detected current of a PFC control circuit B. FIG. 2 is a block diagram showing a configuration of a PFC control unit 110. FIG. It is a figure for demonstrating control operation of a power converter device. It is a figure which shows the power factor improvement result by control of the power converter device. It is an electric circuit diagram which shows the structure of the power converter device 100a of other embodiment of this invention. It is an electric circuit diagram which shows the structure of the power converter device 200 of a prior art. It is an electric circuit diagram which shows the structure of the power converter device 200a of another prior art.

  FIG. 1 is an electric circuit diagram showing a configuration of a power conversion device 100 according to an embodiment of the present invention. The power conversion apparatus 100 of this embodiment includes AC power supply voltage input terminals P11 and P12 to which an AC power supply 101 is connected, DC voltage output terminals P21 and P22 that output a DC voltage, and DC voltage output terminals P21 and P22. Smoothing capacitor 107 connected, inductor 103 connected in series between AC power supply voltage input terminals P11 and P12 and DC voltage output terminals P21 and P22, and forward direction during the positive half cycle of AC power supply voltage A first switching means S1 that performs high-frequency switching by applying a voltage and generates a current in the inductor 103 when the first switching element 105a is in a conductive state, that is, an on state, and the first switching element 105a are not Electricity generated by the back electromotive force generated in the inductor 103 in the conductive state, that is, in the off state. During the negative half cycle of the AC power supply voltage Vac, the first high-speed diode 104a that forms a current path for charging the smoothing capacitor 107 by the forward voltage is applied to perform high-frequency switching, and the second switching Second switching means S2 for generating a current in the inductor 103 when the element 105b is on.

  The power converter 100 further forms a second high-speed path that charges the smoothing capacitor 107 with a current generated by a back electromotive force generated in the inductor 103 when the second switching element 105a is in an OFF state. A diode 104b; an output voltage detection means 109 for detecting an output output to the output terminals P21 and P22; an input voltage detection means 102 for detecting a voltage input to the input terminals P11 and P12; A current detection unit 106 that detects current using a current transformer between the high speed diodes 104a and 104b and the smoothing capacitor 107, an output voltage detected by the output voltage detection unit 109, and an input voltage detection unit 102 Using the input voltage and the current value detected by the current detection unit 106 as inputs, And a PFC control unit 110 that generates a PWM signal for driving the second switching elements 105a and 105b.

  The AC power supply 101, the AC power supply voltage input terminals P11 and P12, and the input voltage detection means 102 are included in the voltage input unit A. The DC voltage output terminals P21 and P22, the current detecting means 106, the smoothing capacitor 107, the inductor 103, the first switching means S1, the first high-speed diode 104a, and the second switching means S2. The PFC control circuit B is configured including the PFC control unit 110. Further, the voltage output unit C includes the output load 108 and the output voltage detection means 109.

Next, the operation of the power conversion apparatus 100 will be described.
First, the current path in the power converter 100 will be described with reference to FIGS. 2A and 2B. In the positive half cycle of the AC power supply 101, as indicated by reference symbol _{I A} of FIG. 2A, the first switching element 105a is the on state, the inductor 103 from the AC power supply 101, the switching elements 105a, through 105b, Return to AC power supply 101.

Subsequently, when the first switching element 105a is off period, as indicated by reference symbol _{I B} in FIG. 2B, the inductor 103 from the AC power supply 101, a first high speed diode 104a, a current detection unit 106, a second switching It returns to the AC power source 101 through the element 105b.

  Next, in the negative half cycle of the AC power supply 101, when the second switching element 105b is in the ON state, the second switching element 105b and the first switching are switched from the AC power supply 101 when the second switching element 105b is in the ON state. It returns to the AC power source 101 through the element 105a and the inductor 103.

  Subsequently, when the second switching element 105 b is in an OFF state, the AC power supply 101 returns to the AC power supply 101 through the second high-speed diode 104 b, the current detection unit 106, the first switching element 105 a, and the inductor 103.

  At this time, in the positive and negative half cycles, when the first and second switching elements 105a and 105b are in the on state, energy is stored in the inductor 103. In the off state, the energy accumulated in the inductor 103 is released to the output load 108, and the output DC voltage is boosted.

  Further, in order to pass through such a current path, in the present invention, the current detection unit 106 is the first current value when the first and second switching elements 105a and 105b are in the OFF state in each of the positive and negative half cycles. The current value of is detected.

  The PFC control unit 110 performs on / off control of the first and second switching elements 105a and 105b so that the detected first current value is similar to the target waveform. In the conventional control method, as shown in FIG. 3, the first switching element 105a detects the current I1 during the on-state period W1, and then detects the current I2 during the off-state period W2, thereby Appropriate control is performed to approach the waveform and improve the power factor. In the present invention, however, in the conventional control method, as shown in FIG. 2B, the current detection unit 106 can measure the current value of the off-state period W2, that is, the first current value. Although the current value actually flows as I1, the current value cannot be detected because the current does not flow through the current detection unit 106. Therefore, as indicated by the reference symbol I3 in FIG. 3, the timing of the on-state period W1 cannot be recognized.

  In the present invention, the PFC control unit 110 performs control only by the current value when the switching elements 105a and 105b are in the off state.

  FIG. 4 is a block diagram illustrating a configuration of the PFC control unit 110. The PFC controller 110 includes an output voltage error detector 116, a reference generator 115, a current error detector 117, an error limiter 118, and a PWM signal generator 119.

  The output voltage error detection unit 116 outputs a result obtained by integrating an error between a result obtained by multiplying the output result obtained by the output voltage detection unit 109 by a constant and a DC voltage obtained by multiplying the target output voltage by a constant for a certain period of time.

  Next, the reference generator 115 outputs a value obtained by multiplying the input voltage detected by the input voltage detector 102 by a constant and the result from the output voltage error detector 116 as a current reference value, that is, a reference. . This reference is the target waveform of the PFC control unit 110 of the present invention, that is, the second current value.

  The current error detection unit 117 outputs a result obtained by performing integration for a certain time with respect to an error obtained by comparing the second current value as the reference and the detection result from the current detection unit 106, and a carrier wave to be described later. It is converted into a voltage value that can be compared with the peak value of a certain triangular wave.

As a result, when the result from the current detection unit 106 is smaller than the reference, the switching elements 105a and 105b are turned on and brought closer to the reference.

When the result from the current detection unit 106 is larger than the reference, each switching element 105a, 105b is turned off, and the power factor is improved by performing control so as to approach the reference. Specifically, the PWM duty ratio is controlled according to the magnitude of the error value from the reference.

  Next, the error limiting unit 118 provides a limit value for the output result of the current error detection unit 117 so that the integration result does not become excessive, and a value that can be compared with the peak value of a triangular wave that is a carrier wave described later. That is, it is converted into a first voltage value and output to the PWM signal generation unit 119.

  The PWM signal generation unit 119 uses the result from the error limiting unit 118 as one input, and compares the output voltage and current with reference to a triangular wave that is a carrier wave that determines the switching frequency of each switching element 105a, 105b. The PWM signal is output to each of the switching elements 105a and 105b so as to obtain a waveform similar to the above.

Next, the operation of the PWM signal generation unit 119 will be described.
FIG. 5 is a diagram for explaining the control operation of the PWM signal generation unit 119. In the prior art, as shown in FIG. 5 (a), each switching element 105a, 105b recognizes the time to turn on and off in order to detect the current value of the on state and the off state. In this state, in order to bring the current value closer to the reference waveform, the peak value 120 of the limit result value of the error limiter 118 is set to the same value as the peak value (peak value) of the triangular wave 121, thereby The result of the error limiting unit 118 goes up and down, and the switching is performed by outputting the PWM signal 123 so that the switching elements 105a and 105b can be switched on for 0 to 100% of the switching period T127. The current value is brought closer to the reference quickly. However, in the present invention, the on-state current value is not detected, and control is lost.

  Next, the control method of the present invention is shown in FIG. In the present invention, by limiting the result output from the error limiting unit 118 to a value smaller than the maximum value of the triangular wave 121 in the PWM signal generating unit 119, the peak value 120 of the result of the error limiting unit 118 is smaller than the triangular wave 121. A portion 124 is created. By performing such a restriction, the PWM signal 123 is forcibly created with an off state time 125.

  By creating the time 125 in which the PWM signal 123 is off, it is possible to periodically detect the current value in the circuit, and it is possible to control the on / off of switching from only the detection result of the off-state current value. . That is, it is possible to compare the detection result of the off-state current value with the reference, control the switching elements 105a and 105b, and improve the power factor.

  FIG. 6 is a diagram illustrating a power factor improvement result in the control of the power conversion apparatus 100. From the figure, the power factor was 97.4% and the input / output power efficiency was 98.5%. In the current detection location in the present invention, control cannot be performed when the method shown in Patent Document 1 and Patent Document 2 is used, but according to the present invention, the voltage Vin and current Iin are detected easily and at low cost. It shows high power factor and efficiency and is controllable.

  In the present embodiment, the current detection unit 106 is provided on the off-current side, that is, the rear stage of the high-speed diodes 104a and 104b. However, the current detection unit 106 is provided on the on-current side, that is, the rear stage or front stage of each switching element 105a, 105b. It is also possible to provide it.

  However, when the current detection unit 106 is provided on the off-current side, only one current detection unit 106 is required. However, when the current detection unit 106 is provided on the on-current side, two current detection units 106 are required.

  In the above description, the result output from the error limiting unit 118 is limited to a value smaller than the maximum value of the triangular wave 121 in the PWM signal generation unit 119, so that the peak of the result of the error limiting unit 118 is higher than the triangular wave 121. A portion 124 in which the value 120 is reduced is created, and the timing at which the triangular wave 121 exceeds the peak value 120 of the result of the error limiting unit 118 is forcibly set as the time 125 in which the PWM signal 123 is off. By calculating this, it is possible to control the timing at which the triangular wave 121 exceeds the peak value 120 as a result of the error limiting unit to forcibly set the PWM signal ON state time.

  FIG. 7 is an electric circuit diagram showing a configuration of a power conversion device 100a according to another embodiment of the present invention. Note that the same reference numerals are given to portions corresponding to the above-described embodiment. In the power converter 100a of the present embodiment, a first series circuit including a first inductor 103a and a first switching element 105a is provided at an output terminal of a diode bridge 130 that rectifies an AC input voltage Vac of a commercial AC power supply. And a second series circuit composed of the second inductor 103b and the second switching element 105b is connected. A first diode 104a is connected between the connection point of the first switching element 105a and the first inductor 103a and the smoothing capacitor 107, and a connection point of the second switching element 105b and the second inductor 103b. And the smoothing capacitor 107 is connected with a second diode 104b. An output load 108 is connected in parallel across the smoothing capacitor 107.

  The interleaved PFC control unit 110a is a control system in which the power source is divided into a plurality of systems (two phases), each phase has a phase difference, and ripples cancel each other, and the current phase has a phase difference of 180 °. Ripple cancels out. The PFC control unit 110a turns on / off the switching elements 105a and 105b alternately with a phase difference of 180 ° (interleave method).

  The PFC control unit 110a detects the inductor current and generates a gate control voltage having a pulse width corresponding to the input current error. The current value of the switching element in which the current of each switching element 105a, 105b flows in the forward direction is detected as it is as the actual current value flowing in the switching element, and the current value of the switching element in which the current flows in the reverse direction is detected as the switching element. By configuring the inductor current detector so as to detect smaller than the actual current value flowing through the bridge, the bridgeless power conversion device 100a can be realized without complicating the configuration of the switching control unit. The effect similar to the power converter device 100 of embodiment can be achieved.

DESCRIPTION OF SYMBOLS 100,100a Power converter 101 AC power supply 102 Input voltage detection means 103 Inductor 104a 1st high speed diode 104b 2nd high speed diode 105a 1st switching element 105b 2nd switching element 106 Current detection means 107 Smoothing capacitor 109 Output voltage Detection means 110, 110a PFC control unit 115 Reference generation unit 116 Output voltage error detection unit 117 Current error detection unit 118 Error limit unit 119 PWM generation unit 121 Triangular wave 123 PWM signal A Voltage input unit B PFC control circuit C Voltage output unit

Claims (6)

An AC voltage input unit to which a commercial AC power supply is connected;
A rectifying unit that includes a switching element driven by a pulse width modulation signal, and that converts an AC voltage input to the AC voltage input unit into a DC voltage;
An output current detector for detecting a current value of an output current of the rectifier in an on state or an off state of the switching element;
A difference between a first current value that is a current value detected by the output current detection unit and a second current value that is a predetermined target current value can be compared with a peak value of a triangular wave that is a carrier wave. A pulse that is converted into a voltage value of 1 and compared with the peak value of the triangular wave, and generates a pulse width modulation signal for driving the switching element based on the comparison result between the first voltage value and the peak value of the triangular wave A power conversion device comprising: a width modulation signal generation unit.   2. The power conversion device according to claim 1, wherein the second current value is a reference value converted based on an output voltage of the rectifying unit and an input voltage of an AC voltage input unit.   The power conversion device according to claim 1, wherein the output current detection unit detects the current when the switching element is in an off state.   The pulse width modulation signal generation unit outputs an off signal of the switching element at a timing when a peak value of the triangular wave exceeds the first voltage value. The power converter described in one.   The power converter according to any one of claims 1 to 4, wherein the output current detection unit is a current transformer.   The power converter according to claim 1, wherein the rectifying unit is a bridgeless power factor correction circuit or an interleaved power factor correction circuit.

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