JP2015070724A - Power conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power conversion device that allows meeting a high step-up capability and a harmonic standard while achieving high efficiency over the entire operating region of a load.SOLUTION: A power conversion device includes: a rectifier circuit 3; a short-circuit section 30 short-circuiting an AC power supply 1 via a reactor 2 connected between the AC power supply 1 and the rectifier circuit 3; and a control section 20 generating a switching pulse that controls the short-circuit section 30 so that a current detection value detected in a period shorter than the half cycle of the AC power supply 1 falls within the range from the upper-limit threshold to the lower-limit threshold and outputting the switching pulse as a driving signal Sa1.

Description

  The present invention relates to a power conversion device.

  As a power factor correction circuit that improves power source power factor and reduces harmonic components contained in input current, for example, in the prior art disclosed in Patent Document 1 below, detection is performed by a controller that controls a switch for rectifier circuit switching and a short-circuit element. The full-wave / double-voltage rectification mode is selected according to the load power consumption or the input current and DC output voltage that can simulate this, and the short-circuit start time and short-circuit time of the short-circuit element are controlled in an open loop. This realizes a power factor improvement function and a boost function.

  The operation of the power factor correction circuit configured in this manner is as follows. First, when the input current is small, the full-wave rectification mode is selected by controlling the switch for switching the rectifier circuit to OFF, and the short-circuit operation of the short-circuit element is performed. Control is performed so that power factor improvement is not performed, and the DC output voltage of the power factor correction circuit is controlled to be small. Next, when the full-wave rectification mode is selected and the input current is a little large, the short-circuit start timing and short-circuit time of the short-circuit element are variably controlled to perform intermittent control, improving the power factor and slightly reducing the DC output voltage. Greatly control. Furthermore, when the input current is large and the step-up ratio of the power factor correction circuit exceeds a predetermined value, the voltage rectification mode is selected by turning on the switch for switching the rectifier circuit, and the short-circuit operation of the short-circuit element is performed. In other words, control is performed so as not to improve the power factor, and the DC output voltage of the power factor improving circuit is largely controlled. In addition, in the state where the voltage doubler rectification mode is selected, when the input current is larger and a larger DC output voltage is required, the short circuit start timing and the short circuit time of the short circuit element are variably controlled to improve the power factor. The DC output voltage is further controlled.

  As described above, in the prior art disclosed in Patent Document 1, the rectifier circuit is controlled to the full-wave rectification mode or the double voltage rectification mode by turning on / off the rectifier circuit switching switch, and the DC output voltage of the power factor correction circuit is increased. Divided into two stages, and the area divided into two stages is further divided into two stages, with no power factor improvement and with power factor improvement, by the short-circuit variable control in the open loop of the short-circuiting element, so that a total of four stages of DC output By configuring the voltage region, and thereby expanding the output range of the DC output voltage, the power factor on the high load side can be improved.

  Further, as another conventional technique for reducing harmonic components included in the input current while improving the power factor of the power supply, for example, the conventional technique shown in Patent Document 2 below is a DC output voltage set according to a load. A DC voltage control unit that outputs a DC voltage control signal according to the deviation value between the reference value and the voltage across the terminals of the smoothing capacitor is provided, and the control signal from the DC voltage control unit and a sine wave synchronization synchronized with the AC power supply A current reference arithmetic unit that outputs a current reference signal from the product with the signal is provided. By comparing this current reference signal with the AC side current of the rectifying element, the switch element is turned on / off at a high frequency, and the DC output voltage is controlled to a desired value while controlling the AC input current in a sine wave form. Yes, the power source power factor can be set to approximately 1, and the generation of harmonics can be suppressed.

JP-A-11-206130 Japanese Patent No. 2140103

  However, according to the conventional techniques of Patent Documents 1 and 2, the control pattern of the short-circuit element is limited. That is, in these conventional techniques, for example, the control pattern of the short-circuit element is limited to either a high-frequency switching mode (Patent Document 2) that feeds back current in the entire load region or a partial switching mode of current open-loop control (Patent Document 1). Is done. Therefore, these prior arts do not operate the short-circuit element in order to avoid excessive boosting of the DC output voltage in the low load region, and power factor improvement is not performed. For this reason, the waveform distortion of the input current is large in the low load region, and the current containing a large amount of harmonic components flows through the reactor, increasing the reactor iron loss, thereby reducing the AC / DC conversion efficiency of the power factor correction circuit. .

  Further, the short-circuit control of the short-circuit element when performing the power factor improvement in the prior art of Patent Document 1 described above is a part in which the short-circuit start timing and the short-circuit time are controlled by an open loop, and the short-circuit operation is performed only for a certain interval with respect to the power cycle. Although it is a switching system, the power factor can be improved and the DC output voltage can be boosted, but the effect is small on the high load side where the amount of harmonic generation increases. Therefore, in order to obtain a sufficient power factor improvement effect in the conventional technology, that is, a harmonic suppression capability, with a future harmonic regulation strengthening, a reactor having a large inductance value is required. Problems such as circuit enlargement and cost increase arise. In addition, when boosting the DC output voltage while suppressing the amount of harmonics generated to a certain level, there is a limit to the boosting capability, so operation on the high load side becomes unstable or stable operation on the high load side. If you think about it, the selection range of the load becomes narrow.

  The present invention has been made in view of the above, and an object of the present invention is to obtain a power conversion device that can satisfy high boosting performance and harmonic standards while achieving high efficiency over the entire operation region of the load. To do.

  In order to solve the above-described problems and achieve the object, the present invention includes a rectifier circuit that converts AC power from an AC power source into DC power, and a reactor connected between the AC power source and the rectifier circuit. And the short-circuit portion that short-circuits the AC power supply, and the short-circuit portion is controlled so that the power supply current is within the range from the upper-limit threshold value to the lower-limit threshold value that is smaller than the upper-limit threshold value within a period shorter than a half cycle of the AC power supply And a control unit that generates a switching pulse to be output and outputs it as a drive signal.

  According to the present invention, since the peak of the current from the AC power supply is suppressed, the effect of being able to satisfy the high boosting performance and the harmonic standard while improving the efficiency over the entire operation region of the load. Play.

FIG. 1 is a diagram illustrating a configuration example of a power conversion device according to Embodiment 1 of the present invention. FIG. 2 is a first diagram for explaining the operation of the power conversion device according to the first embodiment of the present invention. FIG. 3 is a second diagram for explaining the operation of the power conversion device according to the first embodiment of the present invention. FIG. 4 is a third diagram for explaining the operation of the power conversion apparatus according to Embodiment 1 of the present invention. FIG. 5 is a fourth diagram illustrating the operation of the power conversion device according to the first embodiment of the present invention. FIG. 6 is a diagram illustrating a first configuration example of the pulse conversion unit according to the second embodiment of the present invention. FIG. 7 is a diagram for explaining the operation of the power conversion device according to the second embodiment of the present invention. FIG. 8 is a configuration diagram of an upper threshold voltage generation circuit for pulse control. FIG. 9 is a diagram illustrating a second configuration example of the pulse conversion unit according to the second embodiment of the present invention.

  Hereinafter, an embodiment of a power converter according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a diagram showing a configuration example of a power conversion device 100 according to Embodiment 1 of the present invention. FIG. 2 is a first diagram for explaining the operation of power conversion apparatus 100 according to Embodiment 1 of the present invention. FIG. 3 is a second diagram for explaining the operation of power conversion apparatus 100 according to Embodiment 1 of the present invention. FIG. 4 is a third diagram for explaining the operation of power conversion apparatus 100 according to Embodiment 1 of the present invention. FIG. 5 is a fourth diagram for explaining the operation of power conversion device 100 according to the first embodiment of the present invention.

  A power conversion device 100 shown in FIG. 1 generates a DC voltage based on an AC voltage supplied from an AC power source 1 and supplies the DC voltage to a DC load 10 (see FIG. 2). A detection unit 9, a rectifier circuit 3, a smoothing capacitor 4, a DC voltage detection unit 5, a power supply voltage detection unit 6, a control unit 20, and a short circuit unit 30 are provided.

  The reactor 2 is inserted between one input end of the rectifier circuit 3 and the AC power source 1. The rectifier circuit 3 is connected to the AC power source 1 through the reactor 2 and converts the AC voltage of the AC power source 1 into a DC voltage. The rectifier circuit 3 in the illustrated example is configured by a diode bridge in which four diodes are combined. However, the rectifier circuit 3 is not limited thereto, and may be configured by combining, for example, unidirectional conducting elements such as diode-connected MOSFETs. .

  A smoothing capacitor 4 is connected between the output terminals of the rectifier circuit 3, and the smoothing capacitor 4 smoothes the voltage of the full-wave rectified waveform output from the rectifier circuit 3. A DC load 10 is connected in parallel to both ends of the smoothing capacitor 4.

  The current detection means 9 includes a current detection element 8 and a current detection unit 7. The current detection element 8 is connected between the reactor 2 and the rectifier circuit 3 and detects the current value at the connection position. The current detection element 8 is, for example, a current transformer or a shunt resistor. The current detection unit 7 is realized by an amplifier or the like (including an amplification or level shift circuit), and a current within a range (within a low voltage) within which the control unit 20 can handle a voltage proportional to the current detected by the current detection element 8. It converts into detection voltage (Vis) and outputs this as a current detection value. The DC voltage detection unit 5 is realized by an amplifier or the like, detects the voltage across the smoothing capacitor 4, converts the detected voltage into a value within a range (low voltage) that can be handled by the control unit 20, and converts this voltage into a voltage Output as detection value.

  The short-circuit unit 30 includes a diode bridge 31 connected in parallel to the AC power supply 1 via the reactor 2 and a short-circuit element 32 connected to both output terminals of the diode bridge 31 and operates as a bidirectional switch. When the short-circuit element 32 is, for example, a MOSFET, the gate of the short-circuit element 32 is connected to the pulse conversion unit 22, and the short-circuit element 32 is turned on / off by a gate drive signal (drive signal Sa1) from the pulse conversion unit 22. When the short-circuit element 32 is turned on, the AC power supply 1 is short-circuited via the reactor 2 and the diode bridge 31.

  The control unit 20 includes a drive signal generation unit 21 and a pulse conversion unit 22, and the control unit 20 includes a microcomputer, a CPU, and the like.

  The drive signal generation unit 21 generates a drive signal Sa for controlling the short circuit element 32 of the short circuit unit 30 based on the voltage detection values (Vdc, Vs) detected by the voltage detection units (5, 6). In addition to the drive signal Sa, the drive signal generator 21 generates an upper limit threshold voltage Vref and a port output Sb. These signals will be described later.

  The pulse converter 22 is set with an upper threshold that regulates the upper limit of the power supply current Is (short circuit current) that flows when the short-circuit unit 30 is turned on, and a lower threshold that is set to a value smaller than the upper threshold. The pulse converter 22 has a high level period of the drive signal Sa (partial switching pulse) from the drive signal generator 21 (period from when the drive signal Sa is turned on to when it is turned off: on in FIG. 3B) The drive signal Sa is divided into a plurality of pulses so that the current detection value (Is) of the AC power supply 1 detected within the period t) falls within the range (current control range w) from the upper limit threshold to the lower limit threshold. The plurality of pulses thus output are output as the drive signal Sa1 of the short-circuit unit 30. In the pulse converter 22, the operation of generating the drive signal Sa1 is performed in each of the positive polarity and the negative polarity of the AC power supply 1. Details of the pulse converter 22 will be described later.

  Next, the operation of the power conversion apparatus 100 of the present embodiment will be described. First, the operation when the pulse converter 22 is not performing pulse conversion will be described. In the current open loop control, turning on / off the short-circuit portion 30 one time or more in a half cycle of the power supply is referred to as a partial switching pulse mode.

  2A shows a simple circuit including the reactor 2, the short-circuit unit 30, the rectifier circuit 3, and the smoothing capacitor 4 constituting the power conversion device 100, and shows a current path when the short-circuit unit 30 is turned on / off. Has been. FIG. 2B shows various waveforms when the short-circuit element 32 is switched once in the half cycle of the positive side of the AC power supply 1 in the partial switching pulse mode.

  When the short-circuit unit 30 shown in FIG. 2A is turned on, a closed circuit including the AC power source 1, the reactor 2, and the short-circuit unit 30 is formed, and the AC power source 1 is short-circuited via the reactor 2. Therefore, the power source current Is flows through this closed circuit, and magnetic energy (1/2 · LI2) is accumulated in the reactor 2. The stored energy is discharged to the DC load 10 side at the same time as the short-circuit unit 30 is turned off, rectified by the rectifier circuit 3 and transferred to the smoothing capacitor 4. By this series of operations, the power supply current Is as shown in FIG. 2B flows, the energization angle of the power supply current Is can be widened compared with the passive mode without power factor improvement, and the power factor can be improved.

  In the partial switching pulse mode, the energy accumulated in the reactor 2 can be controlled by controlling the short circuit start time and the short circuit duration time of the short circuit unit 30, and the DC output voltage Vdc can be boosted steplessly. FIG. 2B shows a drive signal Sa1 (single pulse) when the short-circuit unit 30 is switched once during the power supply half cycle as an example of the operation in the partial switching pulse mode. The number of times of switching the short-circuit portion 30 may be two or more times.

  Next, the waveform of the power supply current Is when the pulse conversion unit 22 is not operated and the waveform of the power supply current Is when the pulse conversion unit 22 is operated will be described.

  In FIG. 3A, when the pulse conversion unit 22 is not operated, that is, the single pulse (drive signal Sa) from the drive signal generation unit 21 is not converted into a plurality of pulses, the drive signal Sa1 is sent to the short circuit unit 30. Various waveforms when output are shown.

  When the pulse conversion unit 22 is not operating, the drive signal Sa1 is turned on at the timing when the drive signal Sa generated by the drive signal generation unit 21 is turned on, and during the period when the drive signal Sa is turned on (on time). The drive signal Sa1 is also turned on for a period equal to this on time. Accordingly, the short-circuit time of the short-circuit element 32 becomes longer in proportion to the on-time of the drive signal Sa when the power supply voltage Vs is boosted, and the power supply current Is increases as in the illustrated example. The drive signal Sa is turned off when the power supply current Is reaches a predetermined value, and the drive signal Sa1 is turned off at the timing when the drive signal Sa is turned off. When the short-circuiting time of the short-circuit element 32 is increased in this way, more energy can be stored in the reactor 2, but the peak of the power supply current Is increases, so that the power factor is deteriorated and the harmonic component is increased. Problems such as an increase in circuit loss occur.

  In FIG. 3B, when the pulse converter 22 is operated, that is, a single pulse (drive signal Sa) from the drive signal generator 21 is converted into a plurality of pulses and output to the short circuit 30 as the drive signal Sa1. Various waveforms are shown.

  When the pulse converter 22 is operating, the drive signal Sa1 is turned on at the timing when the drive signal Sa generated by the drive signal generator 21 is turned on, and the power supply current Is increases. Although the current detection value detected by the current detection unit 7 increases as the power supply current Is increases, the pulse conversion unit 22 drives when the current detection value exceeds the upper limit threshold while the drive signal Sa is on. The signal Sa1 is turned off. As a result, the power supply current Is decreases and the current detection value detected by the current detection unit 7 decreases. Thereafter, when the current detection value falls below the lower limit threshold during the period in which the drive signal Sa is on, the pulse converter 22 turns on the drive signal Sa1 again. As a result, the power supply current Is increases again, and the current detection value detected by the current detection unit 7 increases.

  As described above, as a result of the driving signal Sa1 being repeatedly turned on / off within the on period t, the peak value of the power supply current Is within the on period t is controlled within the current control range w. Therefore, even when the DC output voltage Vdc is boosted to a relatively high value, the peak value of the power supply current Is in the on period t shown in FIG. 3B is the power supply current Is shown in FIG. Than the peak value (the peak value when the drive signal Sa1 is turned off).

  Note that by adjusting the upper and lower thresholds as shown in FIG. 4, the number of switching times of the drive signal Sa1 within the above-described on-period t is controlled, and the waveform of the power supply current Is can be changed. The current control range w1 shown in FIG. 4 (a) is set to be wider than the current control range w2 shown in FIG. 4 (b). Thus, by adjusting the upper limit threshold and the lower limit threshold, it is possible to control to satisfy the performance according to the reactor 2, the DC load 10, and a standard (for example, a harmonic standard).

  In the present embodiment, the configuration example in which the ON period t of the drive signal Sa is set as the pulse conversion permission period in the pulse converter 22 has been described. However, the pulse conversion permission period is not necessarily the ON period of the drive signal Sa. There is no need to be the same as the time, and a time shorter than the ON time of the drive signal Sa as shown in FIG. 5A may be set as the pulse conversion permission period t1.

  According to the configuration example of FIG. 5A, the drive signal Sa1 is turned on at the timing when the drive signal Sa generated by the drive signal generation unit 21 is turned on, which increases the power supply current Is. Even when the current detection value (Is) exceeds the upper limit threshold before reaching the permission period t1, the pulse conversion unit 22 does not perform pulse conversion, and the pulse indicating the start of the pulse conversion permission period t1 is turned on. Then, the drive signal Sa1 is turned off and the power supply current Is decreases. Thereafter, when the current detection value falls below the lower limit threshold within the pulse conversion permission period t1, the drive signal Sa1 is turned on in the pulse converter 22 and the power supply current Is increases. After that, when the detected current value exceeds the upper limit threshold within the pulse conversion permission period t1, the drive signal Sa1 is turned off in the pulse converter 22, and the power supply current Is decreases again.

  Thus, even when the time shorter than the ON time of the drive signal Sa is set as the pulse conversion permission period t1, the peak value of the power supply current Is in the pulse conversion permission period t1 is controlled within the current control range w. As a result, the number of switching times of the drive signal Sa1 is reduced as compared with the case where a pulse conversion permission period equal to the ON period t of the drive signal Sa is set, and it is possible to take measures against temperature rise and reduce noise by suppressing element loss. is there.

  In the present embodiment, an example has been described in which the upper threshold and the lower threshold set in the pulse converter 22 are configured to be constant values during the power supply half cycle. However, the upper threshold and the lower threshold are not necessarily constant values. However, as shown in FIG. 5B, for example, the upper threshold and the lower threshold may be changed according to the elapsed time from the zero cross of the power supply voltage Vs.

  According to the configuration example of FIG. 5B, the drive signal Sa1 is turned on at the timing when the drive signal Sa is turned on, which increases the power supply current Is. Then, the pulse conversion unit 22 performs pulse conversion according to the upper limit threshold 1 and the lower limit threshold 1 which is a threshold lower than the upper limit threshold 1 until a predetermined period T1 from the zero cross point elapses. In the predetermined period T1, the peak value of the power supply current Is is controlled within the current control range w1. Further, from the time when the predetermined time T1 elapses until the predetermined period T2 elapses, for example, pulse conversion is performed according to the upper threshold 2 which is a threshold higher than the upper threshold 1 and the lower threshold 2 which is a threshold lower than the upper threshold 2. As a result, the peak value of the power supply current Is is controlled within the current control range w2 in the predetermined period T2. Further, in the period T3 from when the predetermined time T2 has elapsed until the drive signal Sa is turned off, for example, pulse conversion is performed according to the upper limit threshold 1 and the lower limit threshold 1, and as a result, in the predetermined period T3, the power supply current The peak value of Is is controlled within the current control range w1.

  By comprising in this way, when many harmonic components of a specific order generate | occur | produce with respect to a harmonic regulation value, the magnitude | size can be reduced.

  As described above, the power conversion device 100 according to the present embodiment includes a rectifier circuit 3 that converts AC power from the AC power source 1 into DC power, and a reactor connected between the AC power source 1 and the rectifier circuit 3. 2 and the current detection value (Is) detected within a period shorter than the half cycle of the AC power supply 1 (for example, the ON period t or the pulse conversion permission period t1) is the upper limit. And a control unit 20 that generates a switching pulse for controlling the short circuit unit 30 so as to be within a range (current control range w) from the threshold value to a lower threshold value that is smaller than the upper threshold value, and outputs the switching pulse as a drive signal Sa1. With this configuration, the DC output voltage Vdc can be boosted while suppressing the peak of the power supply current Is as compared with the conventional simple switching converter. Moreover, since the peak of the power supply current Is can be suppressed, distortion of the power supply current Is due to a short circuit current can be suppressed, and harmonic components can be suppressed. In addition, since the peak of the power supply current Is can be suppressed, the passing period of the power supply current Is can be extended, and the power factor can be improved. Moreover, since the peak of the power supply current Is can be suppressed, an increase in the capacity of components such as a filter circuit of the AC power supply 1 can be suppressed, and an increase in cost can be suppressed. In addition, according to the power conversion device 100 of the present embodiment, even when switching is performed a plurality of times in the half cycle of the power supply, it is not necessary to design the setting time of each switching pulse, and the current upper and lower limits for the positive and negative electrodes Since threshold design is possible, control design is relatively easy.

Embodiment 2. FIG.
FIG. 6 is a diagram showing a first configuration example of the pulse conversion unit 22A according to Embodiment 2 of the present invention. FIG. 7 is a diagram for explaining the operation of the power conversion apparatus 100 according to Embodiment 2 of the present invention. The difference from the first embodiment is that the pulse conversion unit 22A is composed of a hysteresis comparator (positive-side hysteresis comparator HCH, negative-side hysteresis comparator HCL) and a logic IC. The same parts as those in the first embodiment are denoted by the same reference numerals and the description thereof is omitted, and only different parts will be described here.

  The output (current detection voltage Vis) of the current detection unit 7 and the positive-side upper limit threshold voltage VrefH for pulse control output from the drive signal generation unit 21 are input to the positive-side hysteresis comparator HCH. The negative detection hysteresis comparator HCL receives the current detection voltage Vis and the negative control upper limit threshold voltage VrefL for pulse control from the drive signal generator 21. The current detection unit 7 has a level shift circuit and an amplifier at the output stage of the current detection element 8, and 1 / 2Vd is equivalent to 0A (reference) with respect to the low-voltage system power supply Vd, and the AC value is only on the positive side. Output. This enables detection regardless of the current polarity.

  The operation of the pulse converter 22A in the present embodiment will be described with reference to FIG. In the positive-side hysteresis comparator HCH, the relationship between the positive-side upper limit threshold VTHH (H) calculated by the expression (1), the positive-side lower limit threshold VTHH (L) calculated by the expression (2), and the positive-side upper limit threshold voltage VrefH. Determines the hysteresis Δ, the output of the positive side hysteresis comparator HCH is inverted by the NOT logic IC3, and the AND logic IC2 ′ takes the AND logic of the output of the NOT logic IC3 and the drive signal Sa to output the positive side drive signal SaH. Is done.

  In the negative-side hysteresis comparator HCL, the relationship between the negative-side upper limit threshold VTHL (H) calculated by the equation (1) and the negative-side lower limit threshold VTHL (L) calculated by the equation (2) and the negative-side upper threshold voltage VrefL. Therefore, the AND logic IC2 takes the AND logic of the output of the negative-side hysteresis comparator HCL and the drive signal Sa and outputs the negative-side drive signal SaL. The AND logic IC4 takes the AND logic of the positive drive signal SaH and the negative drive signal SaL, and outputs the AND logic result as the drive signal Sa1. In the equations (1) and (2), the upper limit threshold voltage Vref represents the positive-side upper limit threshold voltage VrefH or the negative-side upper limit threshold voltage VrefL, and VOL represents the output saturation voltage of the operational amplifier.

  By using the pulse converter 22A provided with a plurality of hysteresis comparators as described above, it becomes possible to generate a pulse regardless of the current polarity, and the waveform of the power supply current Is can be controlled as shown in FIG. . Therefore, the DC output voltage Vdc can be boosted while suppressing the peak value of the power supply current Is (short circuit current). In the case of the hysteresis comparator shown in FIG. 6, the width of the hysteresis Δ can be changed by changing the resistance values of the resistors R1, R2, and R3. For example, by connecting a series circuit of a switch and a resistor in parallel with the resistor R2 (R2 '), the combined resistance value can be switched by opening and closing the switch.

  FIG. 8 is a configuration diagram of an upper threshold voltage generation circuit for pulse control. The upper threshold voltage Vref can be changed by using the circuit shown in FIG. 8A or 8B.

  The circuit in FIG. 8A generates the upper limit threshold voltage Vref by converting the port output Sb (PWM signal) of the drive signal generation unit 21 into a DC value by a low-pass filter. In this case, the value of the upper limit threshold voltage Vref can be changed seamlessly by controlling the DUTY of the PWM signal. In the circuit of FIG. 8B, the value of the upper limit threshold voltage Vref is changed stepwise by driving the switch (TR) with the port output Sb of the drive signal generator 21 by the voltage dividing ratio of the resistors Rb and Rc. Can do. In addition to the circuits shown in FIGS. 8A and 8B, the upper threshold voltage Vref may be controlled using a control IC or the like.

  FIG. 9 is a diagram illustrating a second configuration example of the pulse conversion unit 22B according to Embodiment 2 of the present invention. The difference from the pulse conversion unit 22A of FIG. 7 is that the output of the current detection unit 7 is input to the + side of the logic IC 1 ′ constituting the positive-side hysteresis comparator HCH, and the positive-side upper limit threshold voltage is set to the − side of the logic IC 1 ′. The point at which VrefH is input, the output of the current detection unit 7 is input to the + side of the logic IC1 constituting the negative-side hysteresis comparator HCL, and the negative-side upper limit threshold voltage VrefL is input to the − side of the logic IC1. Is a point. In this pulse converter 22B, each hysteresis comparator (HCH, HCL) operates with Vref as a center value. It goes without saying that the same effect can be obtained even if the hysteresis comparators are connected in series.

  Note that the drive signal Sa used in the pulse conversion units 22A and 22B of the second embodiment is not limited to a single pulse, and may be a plurality of pulses. Further, the upper and lower thresholds set in the pulse converters 22A and 22B of the second embodiment are not necessarily constant values in the half cycle of the power source, and the power source as described with reference to FIG. You may comprise so that it may change according to the elapsed time from the zero crossing of the voltage Vs. In the second embodiment, the output of the current detection unit 7 outputs a positive / negative value with 1/2 Vd equivalent to 0 A with respect to the low-voltage system power supply Vd. There is no problem. In that case, one hysteresis comparator of the pulse conversion circuits 22A and 22B can be implemented. In the second embodiment, an example in which the hysteresis comparator is configured by H / W has been described. Needless to say, the same effect can be obtained even when the hysteresis comparator is implemented by S / W. In addition, according to the power conversion device 100 of the second embodiment, it is possible to control with a suitable number of switching times and pulse timing regardless of the load condition, so that the design burden can be reduced.

Embodiment 3 FIG.
In the second embodiment, the comparator is configured by H / W, but by taking the pulse pattern into the microcomputer, the current can be controlled without having a current sensor and a pulse conversion unit. The current pattern capture will be described below.

  In the configuration of the second embodiment, the drive signal Sa1 is detected at the input port of the microcomputer. The timer measures the pulse on / off time and stores it. The stored pulse pattern is tabulated in association with operation conditions (environmental conditions such as temperature and load conditions), operation mode, power, or power supply current information to form feedforward control. According to the power conversion device 100 of the third embodiment, since the current sensor and the pulse conversion units 22A and 22B are not provided, it can be realized at low cost.

  Note that the control unit 20 suppresses fluctuations in the DC output voltage due to fluctuations in the power supply and variations by performing feedback control only on the pulse width of the first pulse in the half cycle of the power supply based on the detection information of the DC output voltage Vdc. And a stable DC output voltage Vdc can be obtained. Further, the target for feedforward control is not limited to the first pulse.

  According to power conversion device 100 of the present embodiment, control can be performed with a suitable number of switching times and pulse timing regardless of load conditions, so that the design load can be reduced.

  In addition, the control part 20 of Embodiment 1-3 is a period (ON period t or pulse conversion permission period t1) shorter than the half cycle of AC power supply based on driving | running conditions, or the range from an upper limit threshold value to a lower limit threshold value ( The current control range w) may be configured to change at least one of them. For example, when the motor is used as the DC load 10, the operating condition is a condition such as the rotational speed of the motor or a load torque. In this way, when equipped with means for changing at least one of the period shorter than the half cycle of the AC power supply or the current control range w depending on the operating conditions, it is possible to improve the power factor by expanding the conduction width at low load, On the high load side, correction according to the power is applied when the input power is large due to the domestic harmonic standards, so even if the harmonic component increases slightly, the number of switching is reduced and measures such as high efficiency and low noise are taken. Is possible.

  Moreover, although the power converter device 100 of Embodiment 1-3 is comprised so that drive signal Sa1 may be produced | generated using the electric current detection value detected by the electric current detection part 7, the electric current detection part 7 is not used. Alternatively, the control unit 20 may detect the power supply current and generate the drive signal Sa1.

  Note that the embodiment of the present invention shows an example of the contents of the present invention, and can be combined with another known technique, and a part thereof is not deviated from the gist of the present invention. Of course, it is possible to change the configuration such as omission.

  As described above, the present invention can be applied to a power conversion device, and is particularly useful as an invention that can satisfy high boosting performance and harmonic standards while achieving high efficiency over the entire operation region of the load. is there.

  1 AC power supply, 2 reactor, 3 rectifier circuit, 4 smoothing capacitor, 5 DC voltage detection unit, 6 power supply voltage detection unit, 7 current detection unit, 8 current detection element, 9 current detection means, 10 DC load, 20 control unit, 21 drive signal generation part, 22, 22A, 22B pulse conversion part, 30 short circuit part, 31 diode bridge, 32 short circuit element, 100 power converter.

Claims (15)

A rectifier circuit that converts AC power from an AC power source into DC power;
A short-circuit unit that short-circuits the AC power source via a reactor connected between the AC power source and the rectifier circuit;
A switching pulse for controlling the short-circuit unit is generated and output as a drive signal so that the power supply current falls within the range from the upper limit threshold to the lower limit threshold smaller than the upper limit threshold within a period shorter than a half cycle of the AC power supply. A control unit;
A power conversion device comprising:   The power converter according to claim 1, wherein the control unit detects the power supply current or associates it with a switching pulse.   The control unit generates a switching pulse for controlling the short-circuit unit based on a power supply voltage, and a power supply current is within a range from the upper limit threshold to the lower limit threshold within a high level period of the switching pulse. The power converter according to claim 1 or 2, wherein the switching pulse is divided into a plurality of pulses, and the plurality of divided pulses are output as the drive signal. A power supply voltage detector that detects the zero cross point of the power supply voltage
The said control part changes the said upper limit threshold value and the said lower limit threshold value according to the elapsed time from the zero crossing point detected by the said power supply voltage detection part, The any one of Claim 1 to 3 characterized by the above-mentioned. Power converter.   5. The power conversion device according to claim 1, further comprising a current detection unit configured to detect the power supply current. 6.   The power conversion device according to claim 5, wherein the current detection unit includes a current transformer.   6. The power conversion apparatus according to claim 5, wherein the current detection unit includes an amplification or level shift circuit.   The said control part produces | generates the said drive signal based on the power supply current detected by the said current detection means, and the power supply voltage detected by the said power supply voltage detection part, The any one of Claim 5 to 7 characterized by the above-mentioned. The power conversion device according to item 1.   9. The power conversion according to claim 1, wherein the control unit includes a hysteresis comparator that controls the power supply current to fall within a range from the upper limit threshold to the lower limit threshold. apparatus.   The power converter according to claim 9, wherein the hysteresis comparator is configured to be capable of setting the upper threshold, the lower threshold, and an upper threshold voltage for pulse control.   The power converter according to claim 9, wherein the hysteresis comparator is configured to be able to change any one of the upper threshold, the lower threshold, and an upper threshold voltage for pulse control.   12. The control unit according to claim 1, wherein the control unit divides the switching pulse into a plurality of pulses within the high level period or a pulse conversion permission period shorter than the high level period. The power converter according to item.   The power converter according to any one of claims 1 to 12, wherein the control unit detects a DC output voltage of the rectifier circuit.   The power converter according to claim 13, wherein the control unit feedback-controls the DC output voltage based on the detected value of the DC output voltage.   The control unit changes at least one of a period shorter than a half cycle of the AC power supply or a range from the upper limit threshold to the lower limit threshold based on operating conditions. The power converter device according to any one of the above.

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