JP6416690B2 - DC power supply and air conditioner - Google Patents

Description

  The present invention relates to a DC power supply device that converts an AC voltage into a DC voltage, and an air conditioner using the DC power supply device.

  Trains, automobiles, air conditioners, and the like are equipped with a DC power supply device that converts an AC voltage into a DC voltage. And the direct-current voltage output from a direct-current power supply device is converted into the alternating voltage of a predetermined frequency with an inverter, and this alternating voltage is applied to loads, such as a motor. Such a DC power supply is required to improve power conversion efficiency and save energy.

  For example, in paragraph 0012 of Patent Document 1, “a rectifying unit that converts an AC voltage output from an AC power source into a DC voltage, a reactor connected between the AC power source and the rectifying unit, and the rectifying unit” Smoothing means for smoothing the DC voltage output from the power supply and connecting a load in parallel; power supply voltage detecting means for detecting the AC voltage; and DC voltage detecting means for detecting the DC voltage at both ends of the smoothing means; The AC voltage detected by the power supply voltage detection means (hereinafter referred to as “detected AC voltage”) and the DC voltage detected by the DC voltage detection means (hereinafter referred to as “detected DC voltage”) are received. Control means, and the rectifier means includes a MOSFET as a rectifier element, and the control means is configured to select the MOS based on the detected AC voltage and the detected DC voltage. When the ET is turned ON / OFF and when it is detected that a current has started to flow in the parasitic diode built in each MOSFET, the MOSFET is turned ON to detect that the current flowing through the parasitic diode has stopped. When the MOSFET is turned off, it is detected that a current has started to flow through the parasitic diode in the MOSFET, and the integrated value based on the detected AC voltage, the detected DC voltage, and the inductance of the reactor is The calculation is started, and when the integrated value becomes 0, it is determined that the current flowing through the parasitic diode is stopped. Is described.

JP 2012-143154 A

By the way, in addition to energy saving, the DC power supply apparatus is required to reduce harmonic current from the viewpoint of protection of electronic equipment and power distribution / reception facilities. For this purpose, the power source power factor needs to be improved. Generally, the power factor is improved by short-circuiting the primary power supply side and passing a short-circuit current through the circuit. However, if the number of short circuits is one, it is insufficient for improving the power factor in a region where the load is large.
Further, in order to improve the power source power factor, it is not necessary to simply pass a short-circuit current through the circuit, and it is necessary to adjust the flow timing and the like.

  Then, this invention makes it a subject to provide the DC power unit which can achieve high efficiency and suppression of a harmonic current, and the air conditioner using this DC power unit.

In order to solve the above-described problem, in the first invention, the cathode of the first diode and one end of the first switching element are connected to the positive electrode on the output side, and the anode of the first diode and the second diode Is connected to one end of the AC power supply, the other end of the first switching element and one end of the second switching element are connected to the other end of the AC power supply, and the anode of the second diode. And the other end of the second switching element connected to the negative electrode on the output side, a rectifier circuit that is bridge-connected, a reactor provided between an AC power supply and the rectifier circuit, and an output of the rectifier circuit A smoothing capacitor for smoothing a voltage applied from the rectifier circuit, and the first switching element and the second in synchronization with the polarity of the voltage of the AC power supply. A control unit that performs synchronous rectification control that switches the switching element bidirectionally and flows current to a load, and repeatedly performs circuit short-circuit control that short-circuits the reactor to the AC power supply during a half cycle of the AC power supply a plurality of times. The direct current power supply device is provided.

According to a second aspect of the present invention, an air conditioner comprising the DC power supply device according to claim 1 is provided.
Other means will be described in the embodiment for carrying out the invention.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the DC power unit which can achieve high efficiency and suppression of a harmonic current, and the air conditioner using this DC power unit.

It is a schematic block diagram which shows the DC power supply device in this embodiment. It is the figure which showed the electric current path | route which flows into a circuit, when full-wave rectification is performed in case an alternating current power supply voltage is a positive polarity. It is the figure which showed the electric current path | route which flows into a circuit, when full-wave rectification is performed in the case where alternating current power supply voltage is a negative polarity. FIG. 6 is a waveform diagram of a power supply voltage, a circuit current, and a MOSFET drive pulse during full-wave rectification. It is the figure which showed the electric current path | route which flows into a circuit when an AC power supply voltage is a positive polarity, when a circuit is short-circuited. It is the figure which showed the electric current path | route which flows into a circuit when an AC power supply voltage is a negative polarity, when a circuit is short-circuited. FIG. 6 is a waveform diagram of a power supply voltage, a circuit current, and a MOSFET drive pulse when a short-circuit current is passed. FIG. 5 is a waveform diagram of a power supply voltage, a circuit current, and a MOSFET drive pulse when high-speed switching is performed. It is the figure which showed the relationship of the duty of MOSFET at the time of performing high-speed switching. It is the figure which showed the duty relationship of MOSFET when performing high-speed switching and considering dead time. It is the figure which showed the relationship between the alternating current power supply voltage at the time of performing high-speed switching, and a circuit current. It is the figure which showed the duty of MOSFET when the amount of delay of the current phase by a reactor is considered when the alternating current power supply voltage is positive polarity. It is the figure which showed a mode that the flowing current was insufficient with respect to the target current, when an alternating current power supply voltage was positive polarity and the dead time was provided in one MOSFET. It is the figure showing a mode that the dead time was set to both MOSFET, when alternating current power supply voltage is positive polarity. It is the figure showing a mode that the dead time was set to both MOSFET, when alternating current power supply voltage is negative polarity. It is the figure explaining the outline | summary of the partial switching. It is a figure which shows the equivalent circuit of MOSFET. It is a front view of the indoor unit of the air conditioner in this embodiment, an outdoor unit, and a remote control. It is the schematic explaining the mode that the operation mode of a direct-current power supply device and the operation area | region of an air conditioner were switched according to the magnitude | size of load. It is a schematic block diagram which shows the direct-current power supply device in a modification.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.
FIG. 1 is a configuration diagram of a DC power supply device 1 according to the present embodiment.
As shown in FIG. 1, the DC power supply 1 is a converter that converts an AC power supply voltage Vs supplied from an AC power supply VS into a DC voltage Vd and outputs the DC voltage Vd to a load H (inverter, motor, etc.). is there. The DC power supply device 1 has an input side connected to an AC power source VS and an output side connected to a load H.
The DC power supply device 1 includes a reactor L1, a smoothing capacitor C1, a bridge rectifier circuit 10 including diodes D1, D2, MOSFETs (Q1, Q2), and shunt resistors R1, R2. The DC power supply device 1 further includes a gain control unit 12, an AC voltage detection unit 13, a zero cross determination unit 14, a load detection unit 15, a boost ratio control unit 16, a DC voltage detection unit 17, and a converter control unit 18. And.

  The diodes D1, D2 and the MOSFETs (Q1, Q2) are bridge-connected. The anode of the diode D1 is connected to the cathode of the diode D2, and the connection point P1 is connected to one end of the AC power supply VS via the wiring ha.

The source of the MOSFET (Q1) is connected to the drain of the MOSFET (Q2) via the shunt resistor R1. A connection point P2 between the source of the MOSFET (Q1) and the shunt resistor R1 is connected to one end of the AC power supply VS via the wiring hb.
The anode of the diode D2 is connected to a shunt resistor R2 connected to the source of the MOSFET (Q2).
The drain of the MOSFET (Q1) is connected to the cathode of the diode D1.

  The cathode of the diode D1 and the drain of the MOSFET (Q1) are connected to the positive electrode of the smoothing capacitor C1 and one end of the load H through the wiring hc. Further, the cathode of the diode D2 is connected to the negative electrode of the smoothing capacitor C1 and the other end of the load H via the wiring hd, and the source of the MOSFET (Q2) is connected to the other end of the smoothing capacitor C1 via the shunt resistor R2 and the wiring hd.

Reactor L1 is provided on wiring ha, that is, between AC power supply VS and bridge rectifier circuit 10. The reactor L1 stores electric power supplied from the AC power source VS as energy, and further boosts the energy by releasing this energy.
The smoothing capacitor C1 smoothes the voltage rectified through the diode D1 and the MOSFET (Q1) to obtain a DC voltage Vd. The smoothing capacitor C1 is connected to the output side of the bridge rectifier circuit 10, and the positive electrode side is connected to the wiring hc and the negative electrode side is connected to the wiring hd.

The MOSFETs (Q1, Q2) that are switching elements are on / off controlled by a command from the converter control unit 18 to be described later. By using MOSFETs (Q1, Q2) as switching elements, switching can be performed at a high speed, and by passing a current through a MOSFET with a small voltage drop, so-called synchronous rectification control can be performed, resulting in circuit loss. Can be reduced.
The MOSFET (Q1) has a parasitic diode D11 therein. Similarly, the MOSFET (Q2) has a parasitic diode D21 therein.

  By using a super junction MOSFET having a small on-resistance as the MOSFETs (Q1, Q2), it is possible to further reduce conduction loss. Here, a reverse recovery current is generated in the parasitic diode of the MOSFET during the active operation. In particular, the parasitic diode of the super junction MOSFET has a problem that the reverse recovery current is larger than that of a normal MOSFET parasitic diode and the switching loss is large. Therefore, switching loss can be reduced by using a MOSFET having a short reverse recovery time (trr) as the MOSFET (Q1, Q2).

  Since diodes D1 and D2 do not generate a reverse recovery current even during active operation, it is preferable to select diodes D1 and D2 having a low forward voltage. For example, it is possible to reduce the conduction loss of the circuit by using a general rectifier diode or a Schottky barrier diode with a withstand voltage.

  The shunt resistors R1 and R2 (current detection unit) detect a current (load) flowing through the wirings ha and hb. However, as shown in FIG. 19 to be described later, a transformer may be used as the current detection unit, or a Hall element may be used.

  The gain control unit 12 has a function of controlling a current control gain Kp determined from the circuit current effective value Is and the DC voltage compression ratio a. At this time, by controlling Kp × Is to a predetermined value, the DC voltage Vd can be boosted a times from the AC power supply voltage Vs.

  The AC voltage detector 13 detects an AC power supply voltage Vs applied from the AC power supply VS, and is connected to the wirings ha and hb. The AC voltage detection unit 13 outputs the detected value to the zero cross determination unit 14.

  The zero cross determination unit 14 has a function of determining whether the polarity of the AC power supply voltage Vs detected by the AC voltage detection unit 13 has been switched, that is, whether the zero cross point has been reached. The zero cross determination unit 14 is a polarity detection unit that detects the polarity of the AC power supply voltage Vs. For example, the zero-cross determination unit 14 outputs a signal “1” to the converter control unit 18 while the AC power supply voltage Vs is positive, and outputs “1” to the converter control unit 18 when the AC power supply voltage Vs is negative. A 0 'signal is output.

The load detection unit 15 is configured by, for example, a shunt resistor, and has a function of detecting a current flowing from the AC power supply VS and thus detecting a current value (load) supplied to the load H. If the load H is a motor, the load detection unit 15 may detect the rotational speed of the motor and estimate the current value (load) from this rotational speed. The load detection unit 15 outputs the detected value to the boost ratio control unit 16.
The step-up ratio control unit 16 selects the step-up ratio 1 / a of the DC voltage Vd from the detection value of the load detection unit 15 and outputs the selection result to the converter control unit 18. Then, the converter controller 18 performs switching control by outputting a drive pulse to the MOSFETs (Q1, Q2) so as to boost the DC voltage Vd to the target voltage.

  The DC voltage detector 17 detects the DC voltage Vd applied to the smoothing capacitor C1, and its positive side is connected to the wiring hc and its negative side is connected to the wiring hd. DC voltage detection unit 17 outputs the detected value to converter control unit 18. Note that the detection value of the DC voltage detection unit 17 is used to determine whether or not the voltage value applied to the load H has reached a predetermined target value.

  The converter control unit 18 is, for example, a microcomputer (not shown), reads a program stored in a ROM (Read Only Memory) and develops it in a RAM (Random Access Memory), and a CPU (Central Processing Unit) Various processes are executed. Based on information input from the current detection unit 11 or the shunt resistors R1 and R2, the gain control unit 12, the zero cross determination unit 14, the boost ratio control unit 16, and the DC voltage detection unit 17, the converter control unit 18 The on / off of Q1, Q2) is controlled. The processing executed by converter control unit 18 will be described later.

Three operation modes of the DC power supply device 1 are considered: full wave rectification mode, partial switching mode, and high speed switching mode. The partial switching mode and the high-speed switching mode are modes in which the converter performs an active operation, and the DC voltage Vd is boosted and the power factor is improved by passing a short-circuit current through the bridge rectifier circuit 10. Hereinafter, the operation of the DC power supply device 1 in each mode will be described.
For example, when a load such as an inverter or a motor is large, it is necessary to boost the DC voltage Vd. Further, as the load increases and the current flowing through the DC power supply device 1 increases, the harmonic current also increases. Therefore, in the case of a high load, it is necessary to boost the voltage in the partial switching mode or the high-speed switching mode to reduce the harmonic current, that is, improve the power factor of the power supply input.

≪Full wave rectification operation≫
In order to realize a high-efficiency operation which is the main object of the present invention, synchronous rectification control is performed by switching the MOSFETs (Q1, Q2) according to the polarity of the AC power supply voltage Vs.
FIG. 2 is a diagram showing a current path that flows through the circuit when full-wave rectification is performed when the AC power supply voltage Vs has a positive polarity.
In FIG. 2, a current flows in the direction indicated by the broken-line arrow during a period in which the AC power supply voltage Vs is a positive half cycle. That is, the current flows in the order of AC power supply VS → reactor L1 → diode D1 → smoothing capacitor C1 → shunt resistor R2 → MOSFET (Q2) → AC power supply VS. At this time, the MOSFET (Q1) is always off, and the MOSFET (Q2) is always on. If the MOSFET (Q2) is not in the on state, the current flows through the parasitic diode D21 (see FIG. 1) of the MOSFET (Q2). However, since the characteristics of the parasitic diode of the MOSFET are usually poor, a large conduction loss occurs. Therefore, the conduction loss can be reduced by turning on the MOSFET (Q2) and passing a current through the on-resistance portion of the MOSFET (Q2). This is the principle of so-called synchronous rectification control. Note that the on-operation start timing of the MOSFET (Q2) is from the zero cross timing at which the polarity of the AC power supply voltage Vs switches from negative to positive. The timing at which the MOSFET (Q2) is turned off is the timing at which the polarity of the AC power supply voltage Vs is switched from positive to negative.

FIG. 3 is a diagram showing a current path that flows through the circuit when full-wave rectification is performed when the AC power supply voltage has a negative polarity.
In FIG. 3, a current flows in the direction indicated by the broken-line arrow during the period of a half cycle in which the AC power supply voltage Vs is negative. That is, current flows in the order of AC power supply VS → shunt resistor R1 → MOSFET (Q1) → smoothing capacitor C1 → diode D2 → reactor L1 → AC power supply VS. At this time, the MOSFET (Q2) is always off, and the MOSFET (Q1) is always on. Note that the on-operation start timing of the MOSFET (Q2) is determined from the zero cross timing at which the polarity of the AC power supply voltage Vs is switched from positive to negative. The timing at which the MOSFET (Q2) is turned off is the timing at which the polarity of the AC power supply voltage Vs is switched from negative to positive.
By operating the DC power supply device 1 as described above, high-efficiency operation is possible.

4A to 4D are waveform diagrams of the AC power supply voltage Vs, the circuit current is, and the MOSFET drive pulse during full-wave rectification.
4A shows the waveform of the AC power supply voltage Vs, and FIG. 4B shows the waveform of the circuit current is. FIG. 4C shows the drive pulse waveform of the MOSFET (Q1), and FIG. 4D shows the drive pulse waveform of the MOSFET (Q2).
As shown in FIG. 4A, the AC power supply voltage Vs has a substantially sinusoidal waveform.
As shown in FIG. 4C, the drive pulse of the MOSFET (Q1) becomes L level when the polarity of the AC power supply voltage Vs is positive, and becomes H level when the polarity is negative.
As shown in FIG. 4C, the drive pulse of the MOSFET (Q2) is inverted from the drive pulse of the MOSFET (Q1). When the polarity of the AC power supply voltage Vs is positive, the drive pulse is high. L level.
As shown in FIG. 4B, the circuit current is flows when the AC power supply voltage Vs reaches a predetermined amplitude.
The above is the current flow when the circuit short-circuit operation is performed according to the polarity of the power supply voltage, and the switching operation of the MOSFETs (Q1, Q2). Next, a high speed switching operation will be described.

≪High-speed switching operation≫
Next, a high-speed switching operation for boosting the DC voltage Vd and improving the power factor will be described.
In this operation mode, the MOSFETs (Q1, Q2) are subjected to switching control at a certain switching frequency, and a short-circuit current is passed through the circuit, thereby boosting the DC voltage Vd and improving the power factor. First, the operation when the circuit is short-circuited will be described.

When full-wave rectification is performed in a cycle where the AC power supply voltage Vs is positive, the current flow is as shown in FIG. 2, and the operation of the MOSFETs (Q1, Q2) is as described above. At this time, as shown in FIG. 4B, the circuit current is is distorted with respect to the power supply voltage. This is because the current flows only when the DC voltage Vd becomes smaller than the AC power supply voltage Vs, and the characteristic of the reactor L1.
Therefore, by passing a short-circuit current through the circuit a plurality of times, the power factor is improved by bringing the circuit current closer to a sine wave, and the harmonic current is reduced.

FIG. 5 is a diagram showing a path of the short-circuit current isp that flows when the MOSFET (Q1) is turned on in a cycle in which the power supply voltage is positive.
The path of the short-circuit current isp is in the order of AC power supply VS → reactor L1 → diode D1 → MOSFET (Q1) → shunt resistor R1 → AC power supply VS. At this time, the energy represented by the following formula (1) is stored in the reactor L1. This energy is discharged to the smoothing capacitor C1, so that the DC voltage Vd is boosted.

When full-wave rectification is performed in a cycle in which the AC power supply voltage Vs is negative, the flow of current is as shown in FIG. 5, and the operation of the MOSFETs (Q1, Q2) is as described above.
FIG. 6 is a diagram showing a path when the MOSFET (Q2) is turned on and the short-circuit current isp flows.
The current path is in the order of AC power supply VS → MOSFET (Q2) → shunt resistor R2 → diode D2 → reactor L1. Also at this time, as described above, energy is stored in the reactor L1, and the DC voltage Vd is boosted by the energy.

FIGS. 7A to 7D are waveform diagrams of the AC power supply voltage Vs, the circuit current is, and the MOSFET drive pulse when a short-circuit current is passed.
FIG. 7A shows the waveform of the AC power supply voltage Vs, and FIG. 7B shows the waveform of the circuit current is. FIG. 7C shows a drive pulse waveform of the MOSFET (Q1), and FIG. 7D shows a drive pulse waveform of the MOSFET (Q2).
As shown in FIG. 7A, the AC power supply voltage Vs has a substantially sinusoidal waveform.
As shown in FIG. 7C, the drive pulse of the MOSFET (Q1) becomes L level when the polarity of the AC power supply voltage Vs is positive, and further becomes two H level pulses at a predetermined timing. It becomes H level when the polarity of the AC power supply voltage Vs is negative, and further becomes two L level pulses at a predetermined timing.
As shown in FIG. 7C, the drive pulse of the MOSFET (Q2) is inverted from the drive pulse of the MOSFET (Q1).
As shown in FIG. 7B, the circuit current is rises when the AC power supply voltage Vs is positive and the driving pulse of the MOSFET (Q1) becomes H level, and the AC power supply voltage Vs is negative and It rises when the drive pulse of the MOSFET (Q2) becomes H level. Thereby, a power factor is improved.

FIGS. 8A to 8D are waveform diagrams of AC power supply voltage Vs, circuit current is, and MOSFET drive pulses when high-speed switching is performed.
FIG. 8A shows the waveform of the AC power supply voltage Vs, and FIG. 8B shows the waveform of the circuit current is. FIG. 8C shows a drive pulse waveform of the MOSFET (Q1), and FIG. 8D shows a drive pulse waveform of the MOSFET (Q2).
As shown in FIG. 8A, the AC power supply voltage Vs has a substantially sinusoidal waveform.
As shown in FIG. 8C, when the polarity of the AC power supply voltage Vs is positive, the drive pulse of the MOSFET (Q1) has an off duty according to the magnitude. When the polarity of the AC power supply voltage Vs is negative, it becomes on-duty according to the magnitude.
As shown in FIG. 8C, the drive pulse of the MOSFET (Q2) is inverted from the drive pulse of the MOSFET (Q1), and when the polarity of the AC power supply voltage Vs is positive, the ON pulse corresponding to the magnitude thereof is turned on.・ It becomes duty. When the polarity of the AC power supply voltage Vs is negative, it becomes an off-duty according to the magnitude.
As shown in FIG. 8B, the circuit current is has a sinusoidal waveform in phase with the AC power supply voltage Vs. Thereby, the power factor is further improved as compared with the case of FIG.

In the high-speed switching operation, for example, when the power supply voltage has a positive polarity, the short-circuit current isp is caused to flow by turning on the MOSFET (Q1) and turning off the MOSFET (Q2) during the circuit short-circuit operation. Next, the MOSFET (Q1) is turned off and the MOSFET (Q2) is turned on. Thus, the reason why the MOSFETs (Q1, Q2) are switched on and off in accordance with the presence / absence of a short-circuit operation is that synchronous rectification is performed. In order to simply perform a high-speed switching operation, the MOSFET (Q2) is always in an off state, and the MOSFET (Q1) may be switched at a constant frequency. However, at this time, if the MOSFET (Q2) is also in the off state when the MOSFET (Q1) is off, the current flows through the parasitic diode D22 of the MOSFET (Q2). As described above, this parasitic diode has poor characteristics and a large voltage drop, resulting in a large conduction loss. Therefore, in the present invention, when the MOSFET (Q1) is off, the conduction loss is reduced by performing synchronous rectification by turning on the MOSFET (Q2).
The circuit current is (instantaneous value) flowing through the DC power supply device 1 can be expressed by the following equation (2).

Furthermore, when this equation (2) is rewritten, the following equation (3) is obtained.

Equation (4) shows the relationship between the circuit current is (instantaneous value) and the circuit current effective value Is.

When formula (3) is modified and formula (4) is substituted, formula (5) below is obtained.

When the reciprocal of the step-up ratio is the right side, the following equation (6) is obtained.

Furthermore, the duty d of the MOSFET can be expressed as in Expression (7).

  As described above, by controlling Kp × Is shown in the equation (6), the voltage can be boosted to a times the effective value of the AC power supply voltage Vs, and the duty d (conductivity) of the MOSFET at that time is expressed by the equation It can be given by (7).

FIG. 9 is a diagram showing the on-duty relationship of the drive pulses of the MOSFET (Q1) and the MOSFET (Q2) in the half cycle of the power supply voltage (positive polarity). The vertical axis in FIG. 9 indicates the on-duty, and the horizontal axis indicates the time corresponding to a half cycle of the positive polarity power supply voltage.
The on-duty of the drive pulse of the MOSFET (Q2) indicated by the broken line is proportional to the AC power supply voltage Vs. The on-duty of the driving pulse of the MOSFET (Q1) indicated by a two-dot chain line is obtained by subtracting the on-duty of the driving pulse of the MOSFET (Q2) from 1.0.
In FIG. 9, as shown by the equation (7), as the circuit current is increases, the duty d of the driving pulse of the MOSFET (Q1) that performs the switching operation in order to flow the short-circuit current decreases. The smaller the value is, the larger the driving pulse duty d of the MOSFET (Q1) is. The duty d of the drive pulse of the MOSFET (Q1) on the side where the synchronous rectification is performed has a reverse characteristic to the duty d of the drive pulse of the MOSFET (Q2).

FIG. 10 is a diagram in which the on-duty of the drive pulse of the MOSFET (Q2) in consideration of the dead time in the half cycle of the power supply voltage (positive polarity) is additionally written with a solid line. The vertical axis in FIG. 10 indicates the on-duty, and the horizontal axis indicates the time corresponding to the positive half cycle of the AC power supply voltage Vs.
As described above, when a predetermined dead time is given, the duty of the driving pulse of the MOSFET (Q2) is reduced by this dead time.

FIG. 11 is a diagram showing the relationship between the instantaneous value vs of the AC power supply voltage Vs and the circuit current is (instantaneous value). The solid line indicates the instantaneous value vs of the AC power supply voltage Vs, and the broken line indicates the instantaneous value of the circuit current is. The horizontal axis of FIG. 11 indicates the time for half a cycle of the positive polarity power supply voltage.
As shown in FIG. 11, the instantaneous value vs of the AC power supply voltage Vs and the circuit current is (instantaneous value) are both substantially sinusoidal due to the high-speed switching control, so that the power factor can be improved.
The duty d _Q1 of the MOSFET (Q1) is shown in the following equation (8).

The duty d _Q2 of the MOSFET (Q2) is shown in the following equation (9).

  Further, looking at the relationship between the power supply voltage and the current, the circuit current is is controlled in a sine wave shape, so that the power factor is good. This assumes a state in which the inductance of reactor L1 (see FIG. 1) is small and there is no phase delay of the current with respect to the power supply voltage. If the inductance of the reactor L1 is large and the current phase is delayed with respect to the voltage phase, the duty d may be set in consideration of the current phase.

FIG. 12 is a diagram showing the duty of MOSFET (Q1) when the current phase delay due to reactor L1 is taken into account when AC power supply voltage Vs is positive. The vertical axis in FIG. 12 indicates the duty of the MOSFET (Q1), and the horizontal axis indicates the time for a half cycle of the positive polarity power supply voltage.
The solid line indicates the duty of MOSFET (Q1) when the current phase delay due to reactor L1 is not taken into consideration. The broken line indicates the duty of MOSFET (Q1) when the delay of the current phase due to reactor L1 is taken into consideration. By controlling in this way, even if the inductance of the reactor L1 is large, the current can be controlled in a sine wave shape.

  In the control of the bridge rectifier circuit 10, it is necessary to provide a dead time at the timing when the MOSFET (Q1) is switched from on to off and the MOSFET (Q2) is switched from off to on. The same applies to the timing at which the MOSFET (Q1) is switched from OFF to ON and the MOSFET (Q2) is switched from ON to OFF. When the dead time is not provided, the DC output side of the bridge rectifier circuit 10 is vertically short-circuited, and in the worst case, the DC power supply device 1 may be destroyed.

FIGS. 13A to 13C show circuit currents and driving pulses of the MOSFETs (Q1, Q2) when dead time is provided for each of the MOSFETs (Q1, Q2) when the AC power supply voltage Vs is a positive cycle. FIG.
The solid line of the circuit current in FIG. 13A indicates the current that flows when the dead time is provided in the MOSFET (Q1). The broken line of the circuit current indicates the target value.
FIG. 13B shows the drive pulse waveform of the MOSFET (Q1). A broken line indicates a case where dead time is not considered, and a solid line indicates a case where dead time is considered. A period T indicates a PWM period, a time ton indicates an on time, and a time toff indicates an off time.
FIG. 13C shows a drive pulse waveform of the MOSFET (Q1). In FIGS. 13A to 13C, the horizontal axis indicates a common time. Time td indicates dead time.

At the timing t0 in FIG. 13B, the on-duty should be secured up to the portion indicated by the broken line in the drive pulse waveform of the MOSFET (Q1). However, the set on-duty cannot be secured by providing a dead time on the MOSFET (Q1) side. Therefore, as shown in FIG. 13A, the current cannot be passed to the target current indicated by the broken line.
For this reason, the DC voltage Vd cannot be boosted to the target value.

  For example, when the AC power supply voltage Vs is positive in order to ensure the target dead time, the sharing ratio of the MOSFET (Q1) when considering the sharing ratio of the dead time of the MOSFET (Q1) and the MOSFET (Q2) The smaller the value is, the closer it is to the target current. In other words, ideally, by sharing the dead time 100% on the MOSFET (Q2) side, the target current can be passed, that is, the voltage can be boosted to the target DC voltage Vd. If this content is illustrated, it will become a relationship like FIG.

FIGS. 14A and 14B are diagrams illustrating a state in which a dead time is set for the MOSFET (Q2) when the AC power supply voltage Vs is positive. FIG. 14A shows a drive pulse for the MOSFET (Q1), and FIG. 14B shows a drive pulse for the MOSFET (Q2).
Here, 100% of the dead time is shared on the MOSFET (Q2) side, and no dead time is shared on the MOSFET (Q1) side.
As shown in FIG. 14A, the ON time ton and the OFF time toff are set as the driving pulse for the MOSFET (Q1). Thereby, the circuit current is can be brought close to the target current.
As shown in FIG. 14B, a dead time of time td is provided for the drive pulse of the MOSFET (Q2) with respect to the drive pulse of the MOSFET (Q1). Thereby, the upper and lower short circuit of the DC output side of the bridge rectifier circuit 10 can be prevented.

  Similarly, when the AC power supply voltage Vs is negative, the DC voltage Vd can be boosted to the target value by providing a dead time on the MOSFET (Q1) side. When this content is illustrated, the relationship is as shown in FIG.

FIGS. 15A and 15B are diagrams illustrating a state in which a dead time is set in the MOSFET (Q1) when the AC power supply voltage Vs is negative. FIG. 15A shows a drive pulse for the MOSFET (Q1), and FIG. 15B shows a drive pulse for the MOSFET (Q2).
Here, 100% of the dead time is shared on the MOSFET (Q1) side, and no dead time is shared on the MOSFET (Q2) side.
As shown in FIG. 15A, a dead time of time td is provided for the drive pulse of the MOSFET (Q2) with respect to the drive pulse of the MOSFET (Q1). Thereby, the upper and lower short circuit of the DC output side of the bridge rectifier circuit 10 can be prevented.
As shown in FIG. 15B, the ON time ton and the OFF time toff are set as the driving pulse for the MOSFET (Q2). Thereby, the circuit current is can be brought close to the target current.

  In summary, in the DC power supply device 1 of the present invention, when the AC power supply voltage Vs is positive, the dead time of the MOSFET (Q1) side with respect to the sharing of the dead time of the drive pulse on the MOSFET (Q2) side is Ideally, the dead time is set on the MOSFET (Q2) side. When the AC power supply voltage Vs is negative, the MOSFET (Q2) side is reduced with respect to the sharing of the dead time of the drive pulse of the MOSFET (Q1), and ideally the dead time is set on the MOSFET (Q1) side. .

As described above, when the dead time is set in accordance with the polarity of the AC power supply voltage Vs, the relationship among the duty, on time, and off time of the MOSFETs (Q1, Q2) is expressed as follows.
The on time t _{on_Q1} of the MOSFET (Q1) is calculated by the following equation (10). Here, T is a period.

The off time _{toff_Q1} of the MOSFET (Q1) is calculated by the following equation (11).

The on time t _{on_Q2} of the MOSFET (Q2) is calculated by the following equation (12). Here, td is a dead time.

The off time _{toff_Q2} of the MOSFET (Q2) is calculated by the following equation (13).

The duty d _Q2 of the MOSFET (Q2) is calculated by the following equation (14).

  By setting the dead time as described above, it is possible to reduce the harmonic current by improving the power factor while boosting the DC voltage Vd to the target value. Furthermore, since the DC power supply device 1 of the present invention performs synchronous rectification, high-efficiency operation is possible.

≪Partial switching operation≫
As described above, the circuit current is can be shaped into a sine wave by performing a high-speed switching operation, and a high power factor can be ensured. However, the switching loss increases as the switching frequency increases.
Since the harmonic current increases as the circuit input increases, it becomes difficult to satisfy the regulation value of the higher-order harmonic current in particular. Therefore, it is necessary to ensure a high power factor as the input current increases. Conversely, when the input is small, the harmonic current is also small, so there is a case where it is not necessary to secure a power factor more than necessary. In other words, it can be said that the harmonic current may be reduced by securing an optimum power factor while considering the efficiency in accordance with the load condition.
Therefore, in order to improve the power factor while suppressing an increase in switching loss, a partial switching operation may be performed.

  The partial switching operation does not short-circuit the circuit at a predetermined frequency as in the high-speed switching operation, but boosts the DC voltage Vd by repeatedly short-circuiting the bridge rectifier circuit a plurality of times in the half cycle of the AC power supply voltage Vs. This is an operation mode that improves the power factor. Compared with the case of high-speed switching operation, the switching loss of the MOSFETs (Q1, Q2) is reduced, so that the switching loss can be reduced. Hereinafter, the partial switching operation will be described with reference to FIG.

FIGS. 16A to 16D are diagrams showing the relationship between the driving pulse of the MOSFET (Q1), the AC power supply voltage Vs, and the circuit current is in the cycle in which the AC power supply voltage Vs is positive.
16A shows the AC power supply voltage Vs, and FIG. 16B shows the circuit current is. FIG. 16C shows a drive pulse for the MOSFET (Q1), and FIG. 16D shows a drive pulse for the MOSFET (Q2).
As shown in FIG. 16A, the AC power supply voltage Vs is substantially sinusoidal.
An alternate long and short dash line in FIG. 16B indicates an ideal circuit current is in a substantially sine wave shape. At this time, the power factor is most improved.
Here, for example, when the point P1 on the ideal current is considered, the slope at this point is set to di (P1) / dt. Next, the slope of the current when the MOSFET (Q1) is turned on for the time ton1_Q1 from the state where the current is zero is set to di (ton1_Q1) / dt. Furthermore, after the power is turned on for the time ton1_Q1, the current gradient when the power is turned off for the time toff_Q1 is set to di (toff1_Q1) / dt. At this time, control is performed so that the average value of di (ton1_Q1) / dt and di (toff1_Q1) / dt is equal to the slope di (P1) / dt at the point P1.
Next, similarly to the point P1, the slope of the current at the point P2 is set to di (P2) / dt. Then, the slope of the current when the MOSFET (Q1) is turned on over time ton2_Q1 is set to di (ton2_Q1) / dt, and the slope of the current when turned off over time toff2_Q2 is set to di (toff2_Q2) / dt. . As in the case of the point P1, the average value of di (ton2_Q1) / dt and di (toff2_Q1) / dt is made equal to the slope di (P2) / dt at the point P2. This is repeated thereafter. At this time, it can be approximated to an ideal sine wave as the switching frequency of the MOSFET (Q1) is increased.

In FIG. 16D, first, the MOSFET (Q2) is turned on for a time ton1_Q2, and then turned off for a time toff1_Q2.
As shown in FIG. 16C, at the timing when the MOSFET (Q2) is turned off, the MOSFET (Q1) is turned on for a time ton1_Q1. Then, at the timing when the MOSFET (Q1) is turned off, the MOSFET (Q2) is turned on for a time ton2_Q2. Thereafter, the MOSFETs (Q1, Q2) are repeatedly turned on and off in the same manner. This is because, as described in the high-speed switching operation, the synchronous rectification is performed while performing the circuit short-circuit operation. Also in this partial switching operation, there is a risk of causing a vertical short-circuit at the timing of switching on and off of the MOSFETs (Q1, Q2), and therefore a dead time is provided as in the case of the high-speed switching operation. That is, when the AC power supply voltage Vs is positive, the ratio of the dead time on the MOSFET (Q1) side is made smaller than that of the MOSFET (Q2). Ideally, a dead time is secured on the MOSFET (Q2) side. When the AC power supply voltage Vs is negative, the ratio of the dead time on the MOSFET (Q2) side is made smaller than that of the MOSFET (Q1). Ideally, a dead time is secured on the MOSFET (Q1) side. By setting the dead time in this way, it is possible to improve the power factor and boost the DC voltage Vd while performing a highly efficient operation.

<Dead time variable>
In the description so far, the dead time has been considered as a certain fixed value. However, it may have a characteristic in the dead time and may be changed according to circumstances.
FIG. 16 is an equivalent circuit of a MOSFET gate circuit.
The gate voltage Vgs of the MOSFET has the relationship of the following formula (15).

However, E is a power supply voltage, Cgs is a gate-source capacitance, Cgd is a gate-drain capacitance, and Rg is a gate resistance. The input capacitance Ciss of the gate is represented by the sum of Cgd and Cgs.
Here, the input capacitance Ciss of the gate has a characteristic that the capacitance decreases as the drain-source voltage Vds increases. For this reason, it can be said that the larger the drain-source voltage Vds is, the faster it is turned on. In the DC power supply device 1 of the present invention, since the input power supply is the AC power supply VS, it is considered that the time until the power is actually turned on also changes with the AC power supply voltage Vs. That is, when the on-time ton_zero near the zero cross of the AC power supply voltage Vs is compared with the on-time ton_peak near the peak of the AC power supply voltage Vs, the on-time ton_zero is larger than the on-time ton_peak.

Therefore, in order to set the dead time more optimally, the dead time near the power supply voltage peak may be set smaller than the dead time near the power supply voltage zero cross. By setting in this way, the synchronous rectification period is increased, and the loss reduction effect can be further enhanced.
For example, the dead time td is set as in the following equation (16).

Where td0 is the maximum dead time, T is the switching period, ton is the on time, and toff is the off time.
Here, ton and toff change. When considering the duty, as shown in FIG. 9, the duty decreases near the peak, that is, 100% near the zero cross and 10% or less near the voltage peak, that is, the ton decreases. Therefore, as shown in Expression (16), the dead time td may be reduced by the ratio of the on time to the cycle. By changing the dead time td in consideration of the AC power supply voltage Vs and the characteristics of the MOSFET, the synchronous rectification period can be increased, and the conduction loss reduction effect can be further enhanced. Note that although the equation (16) has been described as the variable method of the dead time td, this is merely a representative equation, and the dead time may be varied by another equation or method.

<Operation of air conditioner and DC power supply>
FIG. 18 is a front view of an indoor unit, an outdoor unit, and a remote controller of an air conditioner according to this embodiment.
As shown in FIG. 18, the air conditioner A is a so-called room air conditioner, and includes an indoor unit 100, an outdoor unit 200, a remote controller Re, and a DC power supply 1 (not shown) (see FIG. 1). . The indoor unit 100 and the outdoor unit 200 are connected by a refrigerant pipe 300, and air-conditions the room in which the indoor unit 100 is installed by a known refrigerant cycle. The indoor unit 100 and the outdoor unit 200 transmit and receive information to and from each other via a communication cable (not shown). The DC power supply device 1 supplies DC power to the indoor unit 100 and the outdoor unit 200.

  The remote controller Re is operated by the user and transmits an infrared signal to the remote controller transmission / reception unit Q of the indoor unit 100. The contents of the infrared signal are commands such as an operation request, a change in set temperature, a timer, an operation mode change, and a stop request. The air conditioner A performs air conditioning operations such as a cooling mode, a heating mode, and a dehumidifying mode based on these infrared signal commands. Moreover, the indoor unit 100 transmits data such as room temperature information, humidity information, and electricity bill information from the remote control transmission / reception unit Q to the remote control Re.

  An operation flow of the DC power supply device 1 mounted on the air conditioner A will be described. The direct-current power supply 1 performs high-efficiency operation and reduction of harmonic current by boosting the power factor and boosting of the direct-current voltage Vd. As described above, the operation mode includes the three operation modes of full-wave rectification operation, high-speed switching operation, and partial switching operation.

For example, when an inverter or a motor of the air conditioner A is considered as the load H, the DC power source device 1 may be operated in the full-wave rectification mode if the load is small and an operation that emphasizes efficiency is necessary.
If the load increases and it is necessary to increase the voltage and secure the power factor, the DC power supply device 1 may be allowed to perform a high-speed switching operation. In addition, as in the rated operation of the air conditioner A, if the load is not so large but it is necessary to ensure the pressure increase or the power factor, the partial switching operation may be performed.

FIG. 19 is a schematic diagram illustrating how the operation mode of the DC power supply device 1 and the operation region of the air conditioner A are switched according to the size of the load.
“Rated operation” means “operation under the T1 condition of JISB8615-1 Table 1 (cooling capacity test condition)” described in JISC9612. Specifically, the temperature conditions are described in JISB8615-1 item 5 “cooling test” and item 6 “heating test”.
The high load operation is, for example, “operation under the overload operation condition described in JIS B 8615-1”, but may be an operation region in which the input is larger than the rated operation.
Intermediate operation refers to “operating capacity that is half of rated operation” and is described in JISC9612.
When the thresholds # 1 and # 2 are provided for the load and the air conditioner A is considered as a device, the DC power supply 1 performs full-wave rectification in the intermediate region where the load is small, and performs partial switching during rated operation. If necessary, perform high-speed switching.
In a low-temperature heating operation region where the load is higher than that of the rated operation, the DC power supply device 1 performs high-speed switching, and performs partial switching as necessary.
As described above, the DC power supply device 1 can reduce the harmonic current while performing high-efficiency operation by switching to the optimum operation mode according to the operation region of the air conditioner A.

When the load H is an inverter, a motor, or the like, the parameters that determine the magnitude of the load may include the current flowing through the inverter or the motor, the modulation rate of the inverter, and the rotation speed of the motor. Further, the magnitude of the load H may be determined by the circuit current is flowing through the DC power supply device 1.
For example, or if the load size is equal to or less than threshold value # 1, DC power supply device 1 performs full-wave rectification, and if threshold value # 1 is exceeded, performs partial switching. Or if the magnitude | size of load exceeds threshold value # 2, the DC power supply device 1 will perform high-speed switching, and if threshold value # 2 is below, it will perform partial switching.
As described above, the DC power supply device 1 can reduce the harmonic current while performing high-efficiency operation by switching to the optimum operation mode according to the size of the load.

  In the present embodiment, an example in which a super junction MOSFET is used as the MOSFET (Q1, Q2) has been described. By using a SiC (Silicon Carbide) -MOSFET as the MOSFETs (Q1, Q2), it is possible to realize further high-efficiency operation.

  Further, by providing the air conditioner A with the DC power supply device 1 of the present invention, the air conditioner A having high energy efficiency (that is, APF) and high reliability can be provided. Even if the DC power supply device 1 of the present invention is mounted on a device other than an air conditioner, it is possible to provide a highly efficient and highly reliable device.

(Modification)
The present invention is not limited to the embodiments described above, and includes various modifications. For example, the above-described embodiment has been described in detail for easy understanding of the present invention, and is not necessarily limited to the one having all the configurations described. A part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Moreover, it is also possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

  A part or all of the above-described configurations, functions, processing units, processing means, and the like may be realized by hardware such as an integrated circuit. Each of the above-described configurations, functions, and the like may be realized by software by a processor interpreting and executing a program that realizes each function. Information such as programs, tables, and files for realizing each function can be stored in a recording device such as a memory or a hard disk, or a recording medium such as a flash memory card or a DVD (Digital Versatile Disk).

In each embodiment, the control lines and information lines indicate what is considered necessary for the explanation, and not all the control lines and information lines on the product are necessarily shown. Actually, it may be considered that almost all the components are connected to each other.
For example, FIG. 20 is a schematic configuration diagram illustrating a DC power supply device 1A according to a modification. The current detection unit 11 (current detection unit) is a transformer, is provided in the wiring hb, and detects a current (load) flowing through the wirings ha and hb. The present invention may be configured in this way. A Hall element or the like may be used instead of the transformer.

1,1A DC power supply 10 Bridge rectifier circuit (rectifier circuit)
11 Current detection part R1, R2 Shunt resistance (Current detection part)
12 Gain Control Unit 13 AC Voltage Detection Unit 14 Zero Cross Determination Unit (Polarity Detection Unit)
DESCRIPTION OF SYMBOLS 15 Load detection part 16 Boost ratio control part 17 DC voltage detection part 18 Converter control part Vs AC power supply C1 Smoothing capacitor D1, D2 Diode ha, hb, hc, hd Wiring L1 Reactor Q1, Q2 MOSFET

Claims (12)

The cathode of the first diode and one end of the first switching element are connected to the positive electrode on the output side, the anode of the first diode and the cathode of the second diode are connected to one end side of the AC power supply, The other end of the first switching element and one end of the second switching element are connected to the other end of the AC power supply, and the anode of the second diode and the other end of the second switching element are on the output side. A rectifier circuit that is bridge-connected by being connected to the negative electrode of
A reactor provided between an AC power supply and the rectifier circuit;
A smoothing capacitor connected to the output side of the rectifier circuit and smoothing a voltage applied from the rectifier circuit;
Synchronous rectification control is performed in which the first switching element and the second switching element are bidirectionally switched in synchronism with the polarity of the voltage of the AC power supply to pass a current to the load, and during the half cycle of the AC power supply. A control unit that repeatedly performs a circuit short-circuit control for short-circuiting the reactor to the AC power source a plurality of times,
A DC power supply device comprising: The controller is
Full-wave rectification operation for performing the synchronous rectification control over the entire AC cycle;
A partial switching operation for performing the synchronous rectification control and partially implementing the circuit short-circuit control at a predetermined phase of the AC power supply;
Switching to any one of the high-speed switching operations in which the synchronous rectification control and the circuit short-circuit control are alternately performed over the entire AC cycle,
The DC power supply device according to claim 1, wherein: The control unit switches to any one of the full-wave rectification operation, the partial switching operation, and the high-speed switching operation according to the load on the output side of the rectifier circuit.
The DC power supply device according to claim 2, wherein The control unit switches to any one of the full-wave rectification operation, the partial switching operation, and the high-speed switching operation according to the operation region of the host device.
The DC power supply device according to claim 2, wherein When the voltage at one end of the AC power supply is positive, the dead time provided in the second switching element is relative to the dead time provided in the first switching element in the same switching cycle. When the voltage at one end of the AC power source is negative, the dead time provided in the second switching element is relatively set with respect to the dead time provided in the first switching element. Make it smaller,
The DC power supply device according to claim 2 , wherein The control unit changes the control dead time of the first and second switching elements according to the voltage of the AC power supply.
The DC power supply device according to claim 5 , wherein: The control unit changes a control dead time of the first and second switching elements according to a voltage phase of the AC power supply.
The DC power supply device according to claim 5 , wherein: The control unit changes the control dead time of the first and second switching elements so that the vicinity of the power supply voltage peak is smaller than the vicinity of the power supply voltage zero cross,
The DC power supply device according to claim 5 , wherein: When the voltage at one end of the AC power supply is positive, a dead time is provided for the control of the second switching element in the same switching cycle, and is not provided for the control of the first switching element. When the voltage on the one end side of the AC power supply is negative, a dead time is provided for the control on the first switching element side in the same switching cycle, and the control on the second switching element side Not provided,
The DC power supply device according to claim 2 , wherein The first and second diodes are SiC (Silicon Carbide) -Schottky barrier diodes or rectifier diodes,
The DC power supply device according to claim 1. The first and second switching elements are super junction MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) or SiC-MOSFETs.
The DC power supply device according to claim 1. A DC power supply device according to any one of claims 1 to 11 is provided.
An air conditioner characterized by that.

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