JP4608284B2 - Power factor correction equipment - Google Patents

Description

  The present invention relates to a power factor correction apparatus using a boost chopper circuit.

  As this type of power factor correction apparatus, one shown in FIG. 9 is known. As shown in the figure, the power factor correction apparatus has a step-up chopper circuit formed by connecting an inductor L1, a switching element Q1, and a diode D1 in a T-shape, and is obtained by rectifying AC of a commercial power supply by the rectifier circuit 1. The pulsating flow is boosted and chopped by a boosting chopper circuit, and the output is smoothed by a capacitor C1 and supplied to a load. The switching element Q1 of the step-up chopper circuit is controlled by the control unit 2 (see, for example, Patent Document 1).

  The control unit 2 uses the detected value ea of the input voltage of the boost chopper circuit obtained by the voltage dividing resistors R1 and R2, the detected value ec of the input current of the boost chopper circuit obtained by the current detecting resistor Ro, and the voltage dividing resistors R3 and R4. The switching element Q1 is controlled by the control signal G1 based on the detected output value eb of the output voltage of the capacitor C1.

  The control unit 2 amplifies the difference between the reference value Vref and the output voltage detection value eb by the error amplifier 201, multiplies the input voltage detection value ea and the error amplification output Vc by the multiplier 202, and multiplies the multiplier 202 by the amplifier 203. The difference between the output signal Vm and the input current detection value ec is amplified, and the amplified output is compared with the output of the sawtooth wave generator 205 by the comparator 204 to obtain a pulse width modulated control signal G1. Yes.

  The voltage / current waveform of each part of the power factor correction circuit is as shown in FIG. That is, the voltage e1 of the commercial power supply is a sine wave AC, and the input voltage | e1 | of the boost chopper circuit is a pulsating waveform obtained by full-wave rectifying the sine wave.

  The input current io of the step-up chopper circuit is a ripple superimposed on a pulsating waveform obtained by full-wave rectification of a sine wave. Although the ripple is superimposed, the input current io is in phase with the input voltage | e1 |, so that the power factor is improved.

  The ripple is a high-frequency component corresponding to the switching frequency of the switching element Q1, and becomes a noise for other devices connected to the commercial power supply. Therefore, the line filter 3 is provided on the commercial power supply side in order to reduce it to an allowable range. .

A microscopic view of the input current io including ripples is as shown in FIG. In the figure, ΔI is the ripple amplitude. This ripple is caused by the rising current i _Q1 flowing through the switching element Q1 when the switching element Q1 is turned on and the falling current i _D1 flowing through the diode D1 when the switching element Q1 is turned off, as the switching element Q1 is turned on / off by the pulse width modulation signal G1.
JP 2000-341957 A (page 2-3, FIG. 4)

  In the power factor correction circuit, it is required to reduce the ripple or noise caused by the ripple as much as possible. Increasing the inductance of the inductor L1 is effective for reducing the ripple, and the line filter 3 may be strengthened for reducing the noise. If the switching frequency of the switching element Q1 is increased to increase the ripple frequency, the effect of the line filter 3 is improved, but on the other hand, the switching loss of the switching element Q1 increases.

  Also, since current ripple affects the life of capacitor elements that smooth the output, a plurality of capacitor elements are connected in parallel so that the current ripple per unit falls within an allowable range. Since current increases, the difficulty of countermeasures increases.

  Therefore, an object of the present invention is to realize a power factor correction apparatus with a small current ripple.

The invention according to claim 1 for solving the above-described problems includes a rectifier circuit that rectifies an alternating current of a commercial power supply, a plurality of boost chopper circuits that are connected in parallel to each other and boost chopping the output of the rectifier circuit, and Capacitors that smooth the outputs of the plurality of boost chopper circuits and supply them to the load, and the plurality of boost chopper circuits in different phases based on the input voltage and input current of the plurality of boost chopper circuits and the output voltage of the capacitors. A control unit that controls the operation so that an error amplifier amplifies a difference between the detected value of the output voltage and a reference value, and a multiplier multiplies the detected value of the input voltage by the error amplification output; The amplifier amplifies the difference between the output of the multiplier and the detected value of the input current, and amplifies the amplified output by a plurality of comparators, one of the plurality of sawtooth wave generators. The outputs of the plurality of sawtooth wave generators having a phase difference between the plurality of outputs by a delay circuit that resets the outputs of the other sawtooth wave generators at a predetermined phase of the generator output, respectively. And a control unit that obtains a plurality of pulse-width-modulated control signals by comparison, respectively .

  The invention according to claim 2 for solving the above problem is characterized in that the input current of the plurality of boost chopper circuits is an input current for each boost chopper circuit. It is a rate improvement device.

The invention according to claim 3 for solving the above-mentioned problem is the power factor correction apparatus according to claim 1, wherein the number of the plurality of step-up chopper circuits is two. .
The invention according to claim 4 for solving the above-described problem is characterized in that the control unit controls the two boost chopper circuits so as to operate with a phase difference of ½ period. It is a power factor improvement apparatus as described in above.

According to the first aspect of the present invention, a power factor correction apparatus includes: a rectifier circuit that rectifies an alternating current of a commercial power supply; a plurality of boost chopper circuits that are connected in parallel to each other and perform boost chopping on the output of the rectifier circuit; A capacitor that smoothes the outputs of the plurality of boost chopper circuits and supplies them to the load, and the plurality of boost chopper circuits in different phases based on the input voltage and input current of the plurality of boost chopper circuits and the output voltage of the capacitor. A control unit that controls the operation so that an error amplifier amplifies a difference between the detected value of the output voltage and a reference value, and a multiplier multiplies the detected value of the input voltage by the error amplification output; The amplifier amplifies the difference between the output of the multiplier and the detected value of the input current, and the amplified output is generated by a plurality of comparators to generate a sawtooth wave from one of the plurality of sawtooth generators. Each of the outputs of a plurality of sawtooth wave generators having a phase difference between them by a delay circuit that resets the output of another sawtooth wave generator at a predetermined phase of the output of the generator. Thus, a control unit that obtains each of the plurality of pulse width modulated control signals is provided, so that a power factor improvement device with a small current ripple can be realized.

  Moreover, suppression by a line filter is facilitated by an increase in the ripple frequency. Further, the ripple condition for the capacitor is relaxed, and it becomes easy to cope with the increase in power or the extension of life. Further, paralleling the boost chopper circuit is also effective in increasing the power and the reliability due to the dispersion of the heat generated by the circuit elements.

  According to the second aspect of the present invention, since the input current of the plurality of boost chopper circuits is the input current for each boost chopper circuit, the power factor can be improved for each boost chopper circuit.

According to the invention of claim 3, since the number of the plurality of step-up chopper circuits is 2, the current ripple can be reduced with the minimum number of parallel circuits.
According to the invention of claim 4, since the control unit controls the two boost chopper circuits to operate with a phase difference of ½ cycle, the phase difference between the current ripples in the two boost chopper circuits is 1. / 2 cycles to minimize the combined current ripple.

  The best mode for carrying out the invention will be described below in detail with reference to the drawings. The present invention is not limited to the best mode for carrying out the invention. FIG. 1 shows an electrical configuration of an example of the power factor correction apparatus. This apparatus is an example of the best mode for carrying out the invention. An example of the best mode for carrying out the invention relating to the power factor correction apparatus is shown by the configuration of the apparatus.

  As shown in the figure, this apparatus has two boost chopper circuits 101 and 102 connected in parallel. The step-up chopper circuit 101 is formed by connecting an inductor L1, a switching element Q1, and a diode D1 in a T shape. The step-up chopper circuit 102 has a T-type connection of an inductor L2, a switching element Q2, and a diode D2.

  In this apparatus, the pulsating current obtained by rectifying the AC of the commercial power source with the rectifier circuit 10 is boosted and chopped by the boost chopper circuits 101 and 102 under the control of the control unit 20, and the output thereof is output by the capacitor C1. Smoothly supplied to the load. AC of the commercial power is supplied through the line filter 30.

  The rectifier circuit 10 is an example of a rectifier circuit in the present invention. The step-up chopper circuits 101 and 102 are examples of the step-up chopper circuit in the present invention. The capacitor C1 is an example of a capacitor in the present invention. The control unit 20 is an example of a control unit in the present invention.

  The control unit 20 detects the input voltage detection value ea of the boost chopper circuits 101 and 102 obtained by the voltage dividing resistors R1 and R2, the detection value ec of the input current of the boost chopper circuits 101 and 102 obtained by the current detection resistor Ro, The switching elements Q1 and Q2 are respectively controlled by control signals G1 and G2 based on the detected value eb of the output voltage of the capacitor C1 obtained by the resistors R3 and R4.

  As shown in FIG. 2, the control unit 20 amplifies the difference between the reference value Vref and the output voltage detection value eb by the error amplifier 201, and multiplies the input voltage detection value ea and the error amplification output Vc by the multiplier 202. The amplifier 203 amplifies the difference between the output signal Vm of the multiplier 202 and the input current detection value ec, and the amplified outputs are compared with the outputs of the sawtooth wave generators 215 and 225 by the comparators 214 and 224, respectively. Thus, control signals G1 and G2 subjected to pulse width modulation are obtained. A delay circuit 230 is provided between the sawtooth wave generators 215 and 225 so as to cause a phase difference between the outputs of the sawtooth wave generators 215 and 225.

  For example, as shown in FIG. 3, the delay circuit 230 compares the sawtooth wave of the sawtooth wave generator 215 with the divided voltage value Vs of the reference voltage Vr by the voltage dividing resistors R5 and R6 by the comparator 232, and outputs the comparison output. The signal is differentiated by a differentiation circuit composed of a capacitor C2 and a resistor R7, and the transistor Q3 connected to the output terminal of the sawtooth wave generator 225 is driven by this differential output signal.

  Due to the action of the delay circuit 230, as shown in FIG. 4, at every timing S when the output voltage (sawtooth wave 1) of the sawtooth wave generator 215 exceeds the voltage Vs, the output voltage of the sawtooth wave generator 225 ( The sawtooth wave 2) is reset. As a result, the period of the sawtooth wave 2 is made the same as that of the sawtooth wave 1 and the phase is delayed with respect to the sawtooth wave 1. The delay amount corresponds to the voltage Vs. The voltage Vs is set so that the delay amount is ½ period. Since the sawtooth waves 1 and 2 have a phase difference of 1/2 cycle, the control signals G1 and G2 of the control unit 20 are pulse width modulation signals having a phase difference of 1/2 cycle as shown in FIG. It becomes.

In the step-up chopper circuits 101 and 102 controlled by the control signals G1 and G2, respectively, their input currents i _L1 and i _L2 have a half-phase phase ripple as shown in FIG. It will be a thing.

  These ripples are caused by rising currents flowing through the switching elements Q1, Q2 when the switching elements Q1, Q2 are turned on and off by the control signals G1, G2, and falling currents flowing through the diodes D1, D2 when the switching elements are off.

The sum io of the input currents i _L1 and i _L2 becomes the input current of the boost chopper circuits 101 and 102 as a whole. As shown in the figure, the total input current io has a smaller amplitude in ripple and doubles the frequency than the individual input currents i _L1 and i _L2 . This is because when the ripple of the input currents i _L1 and i _L2 has a phase difference of ½ period, when one of the ripples is larger than ½ of the ripple amplitude, the other is always more than ½ of the ripple amplitude. This is because it becomes smaller.

  The voltage / current waveform of each part of the power factor correction circuit is the same as that shown in FIG. That is, the voltage e1 of the commercial power supply is a sine wave AC, and the input voltage | e1 | of the boost chopper circuit is a pulsating waveform obtained by full-wave rectifying the sine wave. The input current io of the step-up chopper circuit is a ripple superimposed on a pulsating waveform obtained by full-wave rectification of a sine wave. Although the ripple is superimposed, the input current io is in phase with the input voltage | e1 |, so that the power factor is improved.

  This apparatus is a power factor correction apparatus in which the ripple is reduced to about ½ compared to the conventional example of FIG. Therefore, noise can be sufficiently reduced without increasing the inductances of the inductors L1 and L2 of the boost chopper circuits 101 and 102 so much. Further, since the amplitude of the ripple is reduced and the frequency is doubled, sufficient noise reduction is possible without making the line filter 30 so strong. Since the switching frequency is not changed, the switching loss of the switching elements Q1 and Q2 does not increase even if the ripple frequency is doubled.

  Further, since the phase difference between the control signals G1 and G2 is ½ cycle, the capacitor C1 is charged twice per cycle as shown in FIG. For this reason, the charging current per time is half that of the conventional example of FIG. Therefore, the ripple condition for the capacitor C1 is relaxed, and it becomes easy to cope with a high power or a long life. Further, the paralleling of the step-up chopper circuits 101 and 102 is effective in increasing the power and the reliability due to the dispersion of the heat generated by the circuit elements.

  The number of boost chopper circuits in parallel is not limited to two and may be more than that. When the parallel number of boost chopper circuits is generally n (an integer of 2 or more), the phase difference of the operation between the plurality of boost chopper circuits is set to 1 / n period. As a result, the frequency of the ripple is increased to n times that when there is one step-up chopper circuit.

  Note that the phase difference of the operation between the plurality of boost chopper circuits is not limited to the 1 / n cycle, and may be an appropriate phase difference. Therefore, even when n = 2, the phase difference is not limited to ½ period, but may be other phase differences. However, a half-cycle phase difference when n = 2 is preferable in terms of minimizing ripple. Further, by setting n = 2, it is possible to reduce the ripple with the minimum number of parallel.

  FIG. 7 shows an electrical configuration of another example of the power factor correction apparatus. This apparatus is an example of the best mode for carrying out the invention. An example of the best mode for carrying out the invention relating to the power factor correction apparatus is shown by the configuration of the apparatus.

In FIG. 7, the same parts as those shown in FIG. In this example, two boost chopper circuits 101 ′ and 102 ′ have current detection circuits 41 and 42, respectively, and current detection values e _c1 and e _c2 by the current detection circuits 41 and 42 are input to the control unit 20 ′. It has become. The control unit 20 ′ also receives an input voltage detection value ea by the voltage dividing resistors R1 and R2 and an output voltage detection value eb by the voltage dividing resistors R3 and R4.

The configuration of the control unit 20 ′ is shown in FIG. In FIG. 8, parts similar to those shown in FIG. In the control unit 20 ′, the difference between the output signal Vm of the multiplier 202 and the detected current value e _c1 is amplified by the amplifier 213, and the output signal is compared with the output signal of the sawtooth wave generator 215 by the comparator 214. A control signal G1 is formed. Further, the difference between the output signal Vm of the multiplier 202 and the detected current value _ec2 is amplified by the amplifier 223, and the output signal is compared with the output signal of the sawtooth generator 225 by the comparator 224, so that the control signal G2 is obtained. It is formed.

  Thus, the boost chopper circuits 101 'and 102' are individually controlled based on the input current in each circuit. Therefore, this apparatus can perform a balanced operation between both circuits without being affected by variations in circuit element characteristics between the boost chopper circuits 101 ′ and 102 ′. In this example as well, it goes without saying that the number of boost chopper circuits is not limited to two and may be more.

It is a figure which shows the electric constitution of the power factor improvement apparatus of an example of the best form for implementing this invention. It is a figure which shows the electric constitution of a control part. It is a figure which shows the electrical structure of a delay circuit. It is a figure which shows the output signal of a sawtooth wave generator. It is a figure which shows the relationship between a sawtooth wave and a control signal. It is a figure which shows the relationship between a control signal and the ripple of an electric current. Electric configuration of power factor correction apparatus of another example of the best mode for carrying out the present invention It is a figure which shows the electric constitution of a control part. It is a figure which shows the electrical structure of the prior art example of a power factor improvement apparatus. It is a figure which shows the voltage waveform and current waveform of a power factor improvement apparatus. It is a figure which shows the relationship between a control signal and the ripple of an electric current.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Rectifier circuit 20 Control part 30 Line filter 101,102 Boost chopper circuit L1, L2 Inductor Q1, Q2 Switching element D1, D2 Diode C1 Capacitor R1, R2 Voltage dividing resistor R3, R4 Voltage dividing resistor R0 Current detection resistor 201 Error amplifier 202 Multiplier 203 Amplifier 214, 224 Comparator 215, 225 Sawtooth wave generator 240 Delay circuit

Claims (4)

A rectifier circuit for rectifying the AC of the commercial power supply;
A plurality of step-up chopper circuits connected in parallel to each other and step-up chopping the output of the rectifier circuit;
A capacitor for smoothing the outputs of the plurality of boost chopper circuits and supplying the load to a load;
A control unit that controls the plurality of boost chopper circuits to operate in different phases based on an input voltage and an input current of the plurality of boost chopper circuits and an output voltage of the capacitor , the error amplifier using the output voltage; The difference between the detected value and the reference value is amplified by a multiplier, the detected value of the input voltage is multiplied by the output of the error amplification by a multiplier, and the difference between the output of the multiplier and the detected value of the input current is multiplied by an amplifier. The output of the other sawtooth wave generator is output at a predetermined phase of the output of one sawtooth wave generator of the plurality of sawtooth wave generators by a plurality of comparators. A control unit for obtaining a plurality of pulse-width-modulated control signals respectively by comparing with outputs of a plurality of sawtooth wave generators having a phase difference between the plurality of outputs by a delay circuit for resetting ,
A power factor correction apparatus comprising: The input current of the plurality of boost chopper circuits is an input current for each boost chopper circuit,
The power factor correction apparatus according to claim 1. The number of the plurality of boost chopper circuits is two.
The power factor correction apparatus according to claim 1 or 2, characterized by the above. The control unit controls the two boost chopper circuits to operate with a phase difference of ½ period;
The power factor correction apparatus according to claim 3.

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