JP4931558B2 - Switching power supply - Google Patents

Description

  The present invention relates to an improvement in a high power factor type switching power supply (hereinafter referred to as “PFC”) using an AC power supply as an input.

  As a conventional PFC, there is a circuit system as shown in FIG.

  Fig. 8 shows an arm in which two switch elements are connected in series. When the input voltage is positive, the low-sand switch element Q2 performs the switching operation. When the input voltage is negative, the high-side switch element Q1 switches. Perform the action.

  A number of circuit systems called multi-level inverters have been reported for inverters that receive a DC power supply and output an AC voltage. (See Patent Documents 1 and 2 for multi-level inverters).

  A PFC converter that receives an AC power supply and outputs a DC voltage generally operates in the opposite direction to the inverter, and therefore has the same main circuit configuration and the opposite direction of power flow. Therefore, the main circuit configuration of the multilevel inverter can be used as it is as the main circuit configuration of the multilevel converter.

Non-Patent Document 1 discloses a method for controlling a multilevel converter. This uses a DSP to switch the hysteresis control method depending on the magnitude of the input voltage.
JP 2000-341964 A Japanese Patent Laid-Open No. 2003-319662 B.-R.Lin and D.-J. Chen, “SLIDING MODE CONTROL OF NEUTRAL POINT CLAMPED PWMRECTIFIER”, INTELEC 2001

  In the circuit system of the conventional converter of FIG. 8, in order to reduce the high-frequency blocking filter, it is necessary to increase the switching frequency or increase the size of the boost choke in order to reduce the high frequency component of the input current. When the switching frequency is increased, there is a problem that efficiency is lowered due to switching loss, and an increase in the size of the boosting choke has a problem that the apparatus is increased in size and cost.

Further, since the converter is multilevel, there is a problem that even if the main circuit configuration of the multilevel converter is adopted, the inverter control method cannot be applied as it is to the converter control method. The inverter control system has only one AC output voltage or AC output current control loop, whereas the converter control system requires two DC output voltage control loops and AC input current control loops. It is because it becomes. Also, in the inverter, when the output is increased, the pulse width is widened by PWM modulation, whereas in the converter, the input voltage is AC, so the pulse width is widened near the zero cross of the AC input voltage, and the pulse width is narrowed near the maximum peak. It becomes the reverse control. Moreover, in order to make the AC input current waveform a sine wave waveform with a low distortion rate (THD), a control loop must be constructed so that the error amplifier output for controlling the current is continuous near the zero cross. In addition, if the two smoothing capacitor voltages connected in series are not equal and an imbalance occurs, there is a problem that an excessive voltage is applied to the switch element and the smoothing capacitor. There is also a problem that the capacitor voltage must be balanced and controlled to the same magnitude.
In addition, the control method using the DSP as in Non-Patent Document 1 is complicated and increases the cost, and the carrier frequency is not constant due to hysteresis control, and it is difficult to design a high-frequency block filter.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a switching power supply device that achieves miniaturization and cost reduction.

  In order to solve the above-described problems, a switching power supply according to the present invention is a multilevel converter, which amplifies and integrates an error between a detection signal of a DC output voltage and a reference signal Vref by an error amplifier of a voltage loop, and AC by a multiplier. By multiplying the detection signal of the power supply, a reference signal Iref of AC input current is created, and the difference between two voltage detection signals of two capacitors connected in series to the Iref is superimposed by an addition operation circuit, and the addition operation circuit Amplifies and integrates the error between the output signal and the AC input current detection signal using an error amplifier in the current loop, outputs a sinusoidal signal, and performs PWM modulation with a triangular wave carrier with four different offset levels. By doing this, a total of six switch elements are controlled so that the current waveform of the AC power supply through the high-frequency blocking filter becomes a sine wave with a low distortion rate (THD). And wherein the Rukoto.

  According to the present invention, as shown in FIG. 5, the high frequency component of the alternating current on the output side of the high-frequency blocking filter can be reduced, and the high-frequency blocking filter can be reduced in size and cost.

  Further, the loss of the entire device can be reduced by halving the voltage change applied to the boost choke and the voltage applied to the switch element. When the voltage change applied to the boost choke is halved, the core ΔB is halved. Since the core loss of the choke is proportional to the square to 2.5 of ΔB, the fact that the voltage change applied to the boost choke can be halved means that the core loss can be reduced to a quarter or less. As the switch element, an element having a withstand voltage half that of the prior art can be used, but two conventional switch elements are required in series at one place. A semiconductor element such as a MOSFET can reduce the loss even if two switch elements are connected in series because the Qg-Ron trade-off is improved more than twice in the case of an element having a withstand voltage of half.

  In addition, since the two series capacitor voltages can be balanced and controlled to be equal in magnitude, a smoothing capacitor having a half withstand voltage can be used.

  In addition, since the carrier frequency can be made constant, the design of a high-frequency blocking filter and an EMI filter becomes easy.

  FIG. 1 shows a circuit diagram for carrying out the present invention.

The converter receives an AC power supply 1 and outputs a DC voltage to an electrical load 8.
Two smoothing capacitors 7, an electrical load 8, a multi-level arm of four switch elements, and an arm of two switch elements are connected in parallel between the positive and negative electrodes of the DC voltage output.

  The AC power supply 1 is connected to a current detection element 3 and a boosting choke 4 at one end via a high-frequency blocking filter 2. The step-up choke 4 is connected between the multi-level arms. The other end of the high-pass blocking filter 2 is connected between the arms of the two switch elements.

  The error between the detection signal of the DC output voltage and the reference signal Vref 18 is amplified and integrated by the error amplifier 9 of the voltage loop, and the multiplication signal 10 is multiplied by the detection signal of the AC power source 1 to obtain the reference signal Iref of the AC input current. The difference voltage between the two voltage signals of the smoothing capacitor 7 is made to the Iref by the differential amplifier 17 and superimposed on the Iref by the addition operation circuit 11, and the output signal of the addition operation circuit 11 and the detection signal of the AC input current Is amplified and integrated by the error amplifier 9 in the current loop, and a sinusoidal signal is output. PWM modulation is performed with the four triangular wave oscillators 14, 15, 20, and 21 having different offset levels to generate PWM 1, 2, 3, 4 signals. Q4 outputs a PWM2 signal when Vac is positive and a PWM4 signal when Vac is negative. Q2 outputs PWM1 when Vac is positive and PWM3 when Vac is negative. Since Q1 uses the inverted waveform of Q2, and Q3 uses the inverted waveform of Q4, Q1 and Q2, and Q3 and Q4 are turned on and off alternately. Q6 turns on when Vac is positive, and Q5 turns on when Vac is negative. Further, the waveform shape of the triangular wave oscillator operates without a problem even with a sawtooth wave.

  FIG. 6 shows a circuit diagram when the interleaving method is applied to the control method of the present invention in the multilevel converter. FIG. 7 shows the waveform of each part.

  Triangular wave oscillators SAW5, 6, 7, and 8 are 180 ° out of phase with the waveforms of SAW1, 2, 3, and 4, respectively. In the hysteresis control, it is difficult to apply the interleave method because the frequency changes, but in the control method of the present invention, the interleave method can be easily applied by shifting the phase of the carrier wave.

  By applying the interleaving method using a plurality of arms, it is possible to further reduce the size and cost of the high-frequency blocking filter and reduce the currents of the boost choke and the switch element.

It is a circuit diagram which shows the switching power supply device which concerns on embodiment of this invention. It is a figure which shows the waveform of each part by the switching power supply device which concerns on embodiment of this invention. It is a figure which shows the analysis result of the current path by the magnitude | size of AC power supply 1, and the state of the pressure | voltage rise choke 7. FIG. It is a figure which shows the current waveform of each switching element of Q1-6, and each gate signal. FIG. 9 is a diagram showing a comparison of ripple currents of the boost choke of FIG. 1, FIG. 6, and FIG. 8. The upper diagram shows the ripple current Iripple of the boost choke of the conventional circuit system of FIG. 8, and the middle diagram is FIG. Fig. 6 shows the ripple current Iripple of the multi-level boost choke, and the lower diagram shows the ripple current Iripple (lower) of the combination of the multi-level method and interleave method shown in Fig. 6, and the ripple current of each boost choke. It is a figure (upper stage) which shows Iin1 and Iin2. It is a circuit diagram at the time of applying the switching power supply device which concerns on another embodiment of this invention to an interleave system. It is a figure which shows the waveform of each part by the control method of FIG. It is a figure which shows the circuit system of the conventional converter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 AC power supply 2 High frequency block filter 3 Current detection element 4 Boost choke 5 Switch element 6 Rectifier diode 7 Smoothing capacitor 8 Electrical load 9 Error amplifier 10 Multiplication circuit 11 Addition operation circuit 12 Comparator 13 NOT logic circuit 14 Triangular wave oscillator SAW1
15 Triangular wave oscillator SAW2
16 AND logic circuit 17 Differential amplifier 18 Reference voltage Vref
19 OR logic circuit 20 Triangular wave oscillator SAW3
21 Triangular wave oscillator SAW4
22 Triangular wave oscillator SAW5 (waveform with 180 ° phase shift from SAW1)
23 Triangular wave oscillator SAW6 (waveform with 180 ° phase shift from SAW2)
24 Triangular wave oscillator SAW7 (waveform with 180 ° phase shift from SAW3)
25 Triangular wave oscillator SAW8 (waveform with 180 ° phase shift from SAW4)
26 sawtooth oscillator

Claims (1)

A converter that receives an AC power supply and outputs a DC voltage. Two capacitors connected in series and four switch elements connected in series between the positive and negative electrodes of the DC voltage output are connected in parallel. A rectifier diode is connected from between the capacitors connected in series to the negative terminal of the switch element on the most positive side of the four switch elements connected in series, and the first switch element connected in series is connected to the first switch element. A multi-level arm is constructed by connecting a rectifier diode between the two positively connected capacitors from the positive terminal of the negative-side switch element, and the two are connected in series between the positive and negative electrodes of the DC voltage output. The multi-level arm is formed by connecting the arm of the switch element connected in parallel and connecting the current detection element and the boosting choke in series to the AC power source via the high-frequency blocking filter. In the switching power supply apparatus having a multi-level converter which is connected between the between the arms of the two serially connected switching elements,
The difference between the detection signal of the DC output voltage and the reference signal Vref is amplified and integrated by the error amplifier of the voltage loop, and the reference signal Iref of the AC input current is created by multiplying the detection signal of the AC power source by the multiplier. The difference between the two voltage detection signals of the two capacitors connected in series is superimposed on Iref by an addition operation circuit, and the error between the output signal of the addition operation circuit and the detection signal of the AC input current is superimposed on the current loop. Amplifies and integrates by error amplifier, outputs sinusoidal signal, performs PWM modulation with carrier wave carrier with four different offset levels, and the current waveform of AC power supply through the high-frequency blocking filter is distortion rate (THD A switching power supply characterized by controlling a total of six switch elements so as to have a low sine wave shape.

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