JP5471291B2 - DC power supply - Google Patents

Description

  The present invention relates to a DC power supply device that converts an AC voltage from an AC power source into a DC voltage and supplies power to a load.

  Conventionally, as a DC power supply device that can obtain a high power factor with a simple configuration, a rectifier circuit that rectifies an AC voltage from an AC power supply, a reactor connected to the input side of the rectifier circuit, and a switching element are provided. By using a switching element, the AC power supply is short-circuited / opened through the reactor several times in the half cycle of the power supply, thereby increasing the current-carrying width in the input current and boosting the AC voltage from the AC power supply. A DC power supply device that supplies a voltage to a load is known (see, for example, Patent Document 1).

  FIG. 10 shows a conventional DC power supply device described in Patent Document 1. In FIG.

  A conventional DC power supply device shown in FIG. 10 includes a main circuit including a bidirectional switching means including a reactor 3, a rectifier circuit 20, a smoothing capacitor 5, a diode bridge 21, and a transistor 22, a zero cross detector 23, A switching control unit 7, and by turning on and off the transistor 22 a plurality of times in the power source half cycle of the AC power supply 1, by discharging the energy accumulated in the reactor 3 during the on period to the load side during the off period The AC voltage supplied from the AC power source 1 is boosted and converted to a DC voltage, and power is supplied to the inverter 24 that drives the motor 25 that is a load.

  FIG. 11A is a diagram illustrating an example of an input current waveform of a conventional DC power supply device.

  The switching control unit 7 in the conventional DC power supply device uses the zero cross point of the AC power source 1 obtained by the zero cross detection unit 23 as a reference for a predetermined number of times according to the load size during the power source half cycle of the AC power source 1. The transistor 22 is turned on / off at the timing of time.

  Further, a voltage detection unit 10 for supplying a DC voltage to the load is provided, and by adjusting the ON period of the transistor 22, the output voltage of the DC power supply device is adjusted according to the load, as shown in FIG. A high power factor is realized by obtaining an input current waveform having a wide energization width.

JP 2009-1000049 A

However, in the conventional DC power supply device described above, during the period when the switching element (transistor) is off (and the current flows to the load side of the DC power supply device via the diode in the rectifier circuit), the reactor The potential of the AC power supply line on the side that is not connected to is the potential of the DC output terminal of the DC power supply device that is connected to the diode that is turned on when current flows (the potential on the positive or negative side of the smoothing capacitor) ), While the switching elements are on, all the diodes constituting the rectifier circuit are in the off state (reverse bias state), so the AC power supply line on the side not connected to the reactor The potential is in a floating state with respect to the negative potential of the output of the DC power supply device, and as a result, when the diode constituting the rectifier circuit is reverse-biased Capacitance, changes to the potential determined by the balance of the stray capacitance of the other peripheral portion.

  That is, the diodes constituting the bridge rectifier circuit are D1, D2, D3, D4 (D1 and D2, D3 and D4 are connected in series, D1 and D3 are the positive terminals of the smoothing capacitor, and D2 and D4 are smooth. When the switching means is turned on, when the AC voltage from the AC power source is a positive half cycle, the diode D1 and the diode D4 are connected to each other on the negative terminal of the capacitor. From the on state to the off state, the voltage corresponding to the output voltage of the DC power supply device is shared by the reverse bias voltage of the diode D1 and the diode D4 to reach an equilibrium state. Further, when the AC voltage from the AC power source has a negative half cycle, the diode D2 and the diode D3 are switched from the ON state to the OFF state, and a voltage corresponding to the output voltage of the DC power source device is reverse-biased between the diode D2 and the diode D3. It will be shared by the voltage to reach an equilibrium state. Here, when the diodes constituting the bridge rectifier circuit are the same and balanced, the sharing ratio of the reverse bias voltage is approximately 1: 1, and the potential of the AC power supply line on the side not connected to the reactor is It changes to about a half of the output voltage of the DC power supply device.

  As a result, in the conventional DC power supply device, every time the switching element is turned on / off, the potential difference between the AC power supply line on the side not connected to the reactor and each part on the output side of the DC power supply is within the switching time. Will change.

In general, since the potential of the AC power supply line is stable in terms of AC with respect to the ground, the potential difference between the output of the AC power supply line and the DC power supply device changes each time the switching element is turned on / off. As a result, the potential of each part on the output side of the DC power supply device with respect to the ground changes, which causes common mode noise. (For example, see FIGS. 11B and 11C for the waveform of the potential difference. However, the potential of the AC power supply line not connected to the reactor = the cathode potential of the diode D4.)
The above common mode noise is not a problem when the number of times of switching is relatively small, but increasing the common mode noise is a problem when it is desired to increase the number of times of switching for the purpose of improving the power factor and boosting performance. Become.

  The present invention solves the above-described conventional problems, and provides a high power factor and low noise DC power supply device that can suppress an increase in common mode noise even when the number of switching operations is increased with a simple configuration. The purpose is to do.

  In order to solve the above-described conventional problems, a DC power supply device of the present invention is connected between a bridge rectifier circuit that rectifies an AC voltage from an AC power supply, and an AC power supply and one end of an AC input end of the bridge rectifier circuit. Connected to the AC input side of the bridge rectifier circuit and switching means for short-circuiting / opening the AC power supply via the reactor, and of the diodes (D1, D2, D3, D4) constituting the bridge rectifier circuit Of these, the diode D3 whose anode is connected to the AC input end on the side not connected to the reactor has a longer reverse recovery time than the diode D2 whose cathode is connected to the AC input end on the side connected to the reactor. The diode D4, which is composed of a diode and has a cathode connected to the AC input terminal not connected to the reactor, is connected to the reactor. In which the anode to the AC input ends of the side being continued is constituted by a large diode reverse recovery time than the connected diodes D1.

As a result, the switching means is in the OFF state, and the load side via two diodes D1 and D4 (D2 and D3 when the AC voltage of the AC power supply is a negative half cycle) having a difference in reverse recovery characteristics. When the switching means is turned on from the state where the current is flowing into the diode, the diode D1 (or D2) having the better reverse recovery characteristic is turned off before the diode D4 (or D3). The output voltage of the DC power supply device is shared only by the diode D1 (or D2), and only the reverse bias voltage of the diode D1 (or D2) increases, and eventually reaches a voltage substantially equal to the output voltage.

  Since the reverse-biased diode D1 (or D2) is equivalently the same as the charged capacitor, the diode D4 (or D3) having a poor reverse recovery characteristic can be used while minority carriers still remain. The reverse bias state is lost.

  Therefore, even after the reverse bias voltage of the diode D1 (or D2) reaches a voltage substantially equal to the output voltage, the voltage across the diode D4 (or D3) does not increase, and the current is not changed before the switching means is turned on. The voltage across the diode D4 (or D3) having the reverse reverse recovery characteristic that has been flowing can be maintained at a substantially on-state voltage.

  As a result, the DC power supply device according to the present invention has the voltage across the diode connected between the AC power supply line on the side not connected to the reactor and the output of the DC power supply device before and after the opening / closing operation of the switching means. The fluctuation can be suppressed to almost zero.

  When the switching means is short-circuited / opened, fluctuations in the potential difference between the output of the AC power supply and the DC power supply device do not occur, so that common mode noise accompanying an increase in the number of switching operations can be suppressed.

The figure which shows the structure of the direct-current power supply device in Embodiment 1 of this invention. The figure which shows the structure of the switching means in Embodiment 1 of this invention (a) The figure which shows an example of a switching means (b) The figure which shows another example The figure which shows an example of a structure of the voltage phase detection part in Embodiment 1 of this invention (a) The figure which shows the structure of a voltage phase detection part (b) The figure which shows the output signal of a voltage phase detection part FIG. 4A is a diagram illustrating an example of a waveform of each part in the first embodiment of the present invention. FIG. 5B is a diagram illustrating an input current. FIG. 5B is a diagram illustrating a cathode potential of the diode D2. The figure which shows the input electric current path | route when the switching means 4 of Embodiment 1 of this invention is ON in the voltage of the alternating current power supply 1 between positive half cycles The figure which shows the input electric current path | route at the time of the switching means 4 of Embodiment 1 of this invention OFF in the voltage of AC power supply 1 between positive half cycles The figure which shows an example of the reverse bias voltage waveform of the diode D1 at the time of the switching means 4 of Embodiment 1 of this invention turning on (when the voltage of AC power supply 1 is a positive half cycle) The figure which shows the structure of the DC power supply device in Embodiment 2 of this invention. The figure which shows an example of the waveform of each part in Embodiment 2 of this invention (a) The figure which shows input current (b) The figure which shows the cathode potential of the diode D4 The figure which shows the structure of the conventional DC power supply device The figure which shows an example of the waveform of each part in the conventional direct-current power supply device (a) The figure which shows input current The figure which shows the cathode potential of the diode D2 (c) The figure which shows the cathode potential of the diode D4

According to a first aspect of the present invention, a bridge rectifier circuit that rectifies an AC voltage from an AC power source, a reactor connected between the AC power source and one end of an AC input end of the bridge rectifier circuit, and an AC input side of the bridge rectifier circuit Switching means for connecting and short-circuiting / opening the AC power supply through the reactor, a smoothing capacitor connected to the DC output terminal of the bridge rectifier circuit, and driving the switching means at least twice during the power supply half cycle of the AC power supply In a DC power supply device that includes a switching control unit and converts an AC voltage of an AC power supply into a DC voltage and supplies the load to a load, the diode (D1, D2, D3, D4) that constitutes the bridge rectifier circuit is connected to the reactor. The diode D3 whose anode is connected to the AC input end on the side not connected to the cathode is connected to the AC input end on the side connected to the reactor. The diode D4 is configured with a diode having a large reverse recovery time compared to the diode D2 to which is connected and the cathode is connected to the AC input terminal on the side not connected to the reactor. It is composed of a diode having a longer reverse recovery time than the diode D1 having an anode connected to the AC input end.

  As a result, when the switching means is turned on, the diode D1 (or D2) is turned off before the diode D4 (or D3), and the minority carriers in the diode D4 (or D3) still remain. Since the bias state is lost, the voltage across the diode D4 (or D3) through which the current has flowed before the switching means is turned on can be kept almost the on-state voltage. Since variation in potential difference between the power supply line and the output of the DC power supply device can be suppressed, the occurrence of common mode noise can be suppressed.

  In particular, according to the second invention, in the first invention, the diode D3 has a reverse recovery time of the diode D2 and a decay time in a damping oscillation generated at a midpoint potential of the diode D1 and the diode D2 immediately after the switching means is turned on. The diode D4 is composed of a diode having a reverse recovery time longer than the sum, and the diode D4 has a reverse recovery time of the diode D1 and a decay time in the damped oscillation generated at the midpoint potential of the diode D1 and the diode D2 immediately after the switching means is turned on. It is constituted by a diode having a reverse recovery time longer than the sum of.

  As a result, the voltage across the diode D4 (or D3) through which the current has flowed before the switching means is turned on until the damped oscillation generated at the midpoint potential of the diode D1 and the diode D2 is settled immediately after the switching means is turned on. Since the minority carrier of the diode D4 (or D3) decreases and the diode D4 (or D3) cannot maintain the on-state voltage, the above-described damped oscillation amplitude causes the reactor to maintain the state voltage. The voltage fluctuation that occurs slightly between the AC power supply on the unconnected side and the output of the DC power supply device can also be suppressed, and the voltage between the AC power supply and the output of the DC power supply device before and after the switching operation by the switching means. Since it does not cause fluctuations, further suppress common mode noise. It can be.

  In particular, in the first or second invention, the third invention is such that the diode D3 and the diode D4 are constituted by general rectifying diodes, which are generally inexpensive and have a reverse recovery time of about several tens of μs. By using a large general rectifying diode with a low forward voltage, a sufficient difference in reverse recovery time between the diodes D3 and D4 and the diodes D1 and D2 is ensured, and the same as in the first and second inventions. It is possible to obtain an effect and to configure an inexpensive and highly efficient DC power supply device.

In a fourth aspect of the invention, particularly in the first to third aspects of the invention, the switching control unit drives the switching means at a carrier frequency of 15 kHz or more, and the reverse recovery time of the diodes D1 and D2 is 100 ns or less. The reverse recovery time of D3 and D4 is 1 μs or more. As a result, the reverse recovery time difference between the diodes D1 and D2 and the diodes D3 and D4 is sufficiently provided while suppressing the loss due to the reverse recovery current flowing through the diodes D1 to D4 to a level that can be thermally designed. Or, in addition to obtaining the same effect as the second invention, the frequency is increased to a frequency region where the noise is not so much of concern for humans, so that the number of times of switching is increased, so that the noise from the reactor is not minded. Since the input current can be controlled to a waveform closer to a sine wave by fine switching operation, a higher power factor can be obtained.

  In addition, since the step-up operation is distributed by a large number of switching at a high carrier frequency of 15 kHz or higher, the short-circuit period in one switching is shortened, and even if the duty ratio is increased, the input current ripple increases. Since there is little fear of lowering the rate, it is possible to increase the total short-circuit period for performing the boosting operation, so that higher boosting performance can be obtained.

  In the fifth invention, in particular, in the first to fourth inventions, it is possible to obtain a larger inductance value in the same volume by using a reactor having a core of a silicon steel plate (electromagnetic steel plate) exhibiting a high magnetic permeability. Thus, the conduction of high frequency noise to the AC power supply can be further suppressed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a diagram showing a configuration of a DC power supply device according to the first embodiment of the present invention.

  As shown in FIG. 1, a DC power supply device according to the present invention is connected between a bridge rectifier circuit 2 that rectifies an AC voltage from an AC power supply 1, and one end of an AC input end of the AC power supply 1 and the bridge rectifier circuit 2. Connected to the AC input side of the bridge rectifier circuit 2, the bidirectional switching means 4 for short-circuiting / opening the AC power supply 1 through the reactor 3, and the DC output terminal of the bridge rectifier circuit 2 And a connected smoothing capacitor 5.

  Furthermore, a voltage phase detector 6 that detects the AC voltage phase of the AC power supply 1 and a switching controller 7 that drives the switching means 4 are provided. The switching controller 7 is synchronized with the AC voltage phase obtained by the voltage phase detector 6. At this timing, the switching means is driven at least twice during the power source half cycle of the AC power source 1 to boost the AC voltage of the AC power source 1 to convert it into a DC voltage and supply it to the load 8.

  Furthermore, in the DC power supply device according to the first embodiment of the present invention, the anode is connected to the AC input end of the diode (D1, D2, D3, D4) constituting the bridge rectifier circuit 2 that is not connected to the reactor. The diode D3 is configured with a diode having a longer reverse recovery time than the diode D2 whose cathode is connected to the AC input end on the side connected to the reactor, and is connected to the AC input end on the side not connected to the reactor. The diode D4 to which the cathode is connected is composed of a diode having a longer reverse recovery time than the diode D1 to which the anode is connected to the AC input terminal connected to the reactor.

  Details of each part will be described below.

  FIG. 2 is a diagram illustrating a configuration example of the switching unit 4.

The switching means 4 only needs to be bidirectional. For example, as shown in FIG. 2A, the switching means 4 is constituted by a general rectifying diode bridge 4a and an IGBT 4b (or MOSFET). can do. Further, as shown in FIG. 2 (b), by configuring with two stone MOSFETs 4c and 4d, the on-state loss when the current flowing through the switching means 4 is small is reduced, so that the efficiency at light load is reduced. It can also be increased.

  Next, a configuration example of the voltage phase detector 6 is shown in FIG. The voltage phase detector 6 can be constituted by a voltage detection transformer (PT), but as shown in FIG. 3A, it is constituted by a photocoupler 6d, resistors (6b, 6c, 6e), and a diode 6a. By detecting the zero cross point of the AC power source 1 and estimating the voltage phase of the AC power source 1 based on the detected time from the detected zero cross point, the circuit can be made inexpensive. FIG. 3B shows an output signal of the voltage phase detector 6.

  FIG. 4 is a diagram showing a waveform example of each part in the first embodiment of the present invention.

  The switching control unit 7 estimates the timing (voltage phase) at which the switching means 4 is turned on based on the time of the zero cross point of the AC voltage detected by the voltage phase detection unit 6 and the elapsed time from the zero cross point, and the obtained voltage Based on the phase, the switching means 4 is switched multiple times for each half cycle of the AC power supply 1.

  Specifically, the switching control unit 7 feeds back the voltage of the smoothing capacitor 5 every half cycle of the AC power supply 1, and a plurality (5) of AC voltage phases with which the short-circuit is started in advance are determined. By adjusting the short-circuit period of the short-circuit pulse, the input current as shown in FIG. 4A is obtained while controlling the DC voltage supplied to the load 8 to a desired voltage required according to the load. The energization width of the input current can be expanded and a high power factor can be obtained.

  FIG. 5 is a diagram showing an input current path when the switching means 4 of the DC power supply device according to Embodiment 1 of the present invention is on during the period in which the AC voltage of the AC power supply 1 is positive.

  As shown in FIG. 5, when the switching means 4 is on, the input current from the AC power source 1 flows only through the reactor 3 and the switching means 4 and returns to the AC power source 1, so that all the diodes D1 to D4 are It will be in an off state.

  FIG. 6 is a diagram showing an input current path when the switching means 4 of the DC power supply device according to Embodiment 1 of the present invention is OFF during the period in which the AC voltage of the AC power supply 1 is positive.

  As shown in FIG. 6, when the switching means 4 is off, the diode D1 and the diode D4 are turned on, and the diode D2 and the diode D3 are turned off.

  As can be seen from FIGS. 5 and 6, in general, when the switching means 4 is turned on, both the diode D1 and the diode D4 shift from the on state to the off state, so that the conventional DC power supply device (FIG. 10). 11 (b) and 11 (c), both the diode D1 and the diode D4 are in a state where a reverse bias voltage is applied, and the diode D1 viewed from the negative output terminal of the DC power supply device. The cathode potential, that is, the potential of the AC power supply 1 (on the side not connected to the reactor 3) fluctuates greatly each time the switching means 4 is opened and closed.

  However, since the diode D4 in the DC power supply device according to the first embodiment of the present invention is configured with a diode having a sufficiently large reverse recovery time compared to the diode D1, the diode D4 is turned on when the switching means 4 is turned on. Before the excess carriers stored therein are completely eliminated, the diode D1 is turned off first, and a reverse bias voltage is applied only to the diode D1. Thereafter, the reverse bias voltage of the diode D1 converges to a voltage substantially equal to the output voltage of the DC power supply device, accompanied by a damped oscillation due to the capacitance of the diode D1 itself, the pattern and other stray inductances, and resistance components.

  FIG. 7 is a diagram showing an example of the reverse bias voltage waveform of the diode D1 when the switching means 4 is turned on. In the diode D4 in the DC power supply device according to the first embodiment, the reverse recovery time of the diode D1 and the damped oscillation at the midpoint potential of the diodes D1 and D2, that is, the attenuation of the damped oscillation at the reverse bias voltage of the D1 are substantially reduced. The reverse recovery time is larger than the sum of the attenuation time until completion (the time until the amplitude of the reverse bias voltage attenuation oscillation applied to the diode D1 becomes about 1/10 of the overshoot amount with respect to the convergence voltage). It is composed of a diode.

  As a result, when the switching means 4 is turned on, the diode D4 is kept in a substantially conductive potential difference before the switching means 4 is turned on. As a result, in the DC power supply device of the present invention, the cathode potential of the diode D2 (the anode potential of D1) viewed from the negative side of the output of the DC power supply device is the same as that of the switching means 4 as shown in FIG. The cathode potential of the diode D4 as viewed from the negative side of the output of the DC power supply device is shown in FIG. 4 (c) while it fluctuates with an amplitude substantially equal to the output voltage (DC voltage) of the DC power supply device each time it is opened and closed. As shown, there is almost no fluctuation before and after the switching means 4 is opened and closed.

  When the reverse recovery time of D4 is shorter than the time until the damped oscillation in the reverse bias voltage of the diode D1 converges, the absolute value of the AC voltage of the AC power supply 1 is the same as in the conventional DC power supply device. The voltage corresponding to the difference between the value and the DC voltage of the smoothing capacitor 5 is shared by the reverse bias voltage of the diode D1 and the diode D4, but the reverse recovery time of the diode D4 is sufficiently longer than the reverse recovery time of the diode D1. If it is longer, the share ratio of the reverse bias voltage at the time of convergence of the damped oscillation is larger in the diode D1 than in the diode D4.

  Therefore, the reverse recovery time of the diode D4 is longer than the reverse recovery time of the diode D1, and the reverse recovery time of the diode D4 is such that the amplitude of the damped oscillation of the reverse bias voltage applied to the diode D1 immediately after the switching means 4 is turned on with respect to the convergence voltage. Even when it is about the time until the amount of overshoot becomes ½ or less, the reverse bias voltage of the diode D4 when the switching means 4 is turned on, that is, the voltage fluctuation between the AC power supply 1 and the DC power supply device is reduced. Therefore, it is possible to reduce the amount of common mode noise generated compared to a conventional DC power supply device.

  Further, in the DC power supply device according to the first embodiment, since the relationship between the diode D2 and the diode D3 is the same as the relationship between the diode D1 and the diode D4, the above content is the negative half cycle of the AC power supply 1. The same holds true for.

  As described above, the DC power supply device of the present invention can suppress the steep fluctuation of the potential difference between the AC power supply 1 and the output of the DC power supply device, which is seen in the conventional DC power supply device when the switching means 4 is opened and closed. Therefore, between the outputs of the AC power supply 1 and the DC power supply apparatus, a relatively high frequency synchronized with the switching operation as shown in FIG. Does not cause voltage fluctuations with components.

  Therefore, the DC power supply device of the present invention can greatly suppress the occurrence of common mode noise as compared with the conventional DC power supply device even if the number of times of switching is increased, and has a high power factor and low noise. Can be realized.

(Embodiment 2)
FIG. 8 is a diagram showing a configuration of a DC power supply device according to the second embodiment of the present invention.

As shown in FIG. 8, the DC power supply device according to the present invention includes a current detection unit 11 that detects an input current flowing through the reactor 3 in addition to the configuration of the first embodiment.

  The diode D1 and the diode D2 on the side connected to the reactor 3 are a high speed diode (fast recovery diode) with a reverse recovery time trr of about 30 to 100 ns, and the diode D3 and the diode D4 on the side not connected to the reactor 3 are reverse It is composed of a general rectifying diode having a recovery time of about 10 to 20 μs.

  FIG. 9 is a diagram illustrating a waveform example of each part in the second embodiment.

  In the switching control unit 7 of the DC power supply device according to the present embodiment, the switching control unit 7 calculates the input current from the AC power source 1 detected by the current detection unit 11 by PWM control using a carrier frequency of 15 kHz or more. By performing feedback control so as to be equal to the obtained sinusoidal command current value, the input current has a waveform as shown in FIG.

  The command current value is determined by the switching control unit 7 according to the amplitude of the sine wave, and the supply voltage (DC voltage) to the load 8 detected by the voltage detection unit 10 is preset according to the load 8. Adjusted by voltage feedback to equal the voltage.

  Also in the DC power supply apparatus according to the second embodiment, the diodes D3 and D4 that are not connected to the reactor 3 are sufficiently reverse-recovery time as compared with the diodes D1 and D2 that are connected to the reactor 3, as in the first embodiment. In addition, immediately after the switching means 4 is turned on, the diode is attenuated in the damped oscillation phenomenon seen at the midpoint potential of the diodes D1 and D2, which is caused by the capacitance of the diode and the inductance and resistance components such as the pattern. Since the reverse recovery time is larger than the sum of the time and the reverse recovery time of the diodes D1 and D2, as in the first embodiment, the cathode potential of the diode D4, that is, The voltage between the AC power supply 1 (on the unconnected side) and the DC power supply is open. A voltage waveform as shown in FIG. 9 (b), in which a steep fluctuation at the time is suppressed, and goes back and forth between a DC voltage equal to the output voltage of the DC power supply device and 0 volt almost every half cycle of the AC power supply 1. It becomes.

  In the DC power supply device according to the second embodiment, the number of switching operations is one to two orders of magnitude higher than that in the first embodiment, so that the noise suppression effect becomes more prominent.

  In a general printed circuit board mounting environment, if the reverse recovery time of the diode D3 and the diode D4 is about one digit larger than the reverse recovery time of the diode D1 and the diode D2, the above effect can be obtained. Therefore, when a high-speed diode of 30 ns to 100 ns is used for the diodes D1 and D2 in consideration of the loss due to the reverse recovery current of the rectifier circuit from the carrier frequency in PWM control, the reverse recovery time is 1 μs for the diodes D3 and D4. The above diode may be used.

  In addition, since the diode in the off state can be equivalently represented by a capacitor, if a sufficient reverse recovery time difference between the diodes D1 and D2 and the diodes D3 and D4 cannot be secured, the diode D3 and the diode D4 are small in parallel. The same effect can be obtained even if a capacitor having a capacitance is connected.

As described above, the direct-current power supply device according to the second embodiment suppresses the occurrence of common mode noise and increases the frequency to a frequency region where noise is not a concern for humans, thereby increasing the number of switching operations. Since the input current can be controlled to a waveform closer to a sine wave by a fine switching operation without worrying about noise, a higher power factor than that of the DC power supply according to the first embodiment can be obtained with low noise. be able to.

  Further, in the DC power supply device according to the second embodiment, the short-circuit period per switching is represented by the product of the carrier period and the duty ratio, so that even if the duty ratio is increased, one short-circuiting is performed. The period is limited in principle to a value not longer than the carrier period. The amount of increase in the input current during one short-circuit period is determined by the product of the current change rate calculated by the ratio of the instantaneous voltage of the AC power supply 1 and the inductance value of the reactor 3 and the short-circuit period. In the DC power supply of the second embodiment controlled at the carrier frequency, the increase in current ripple is limited even when the duty ratio is increased in order to ensure a high boosting rate.

  Therefore, even if the duty ratio is increased, the current component of the carrier frequency in the input current increases, and there is less concern about a decrease in the power factor due to a decrease in the content of the fundamental component. When the influence of the above is taken into consideration, the total short-circuit period during which the boosting operation is performed can be increased as compared with the DC power supply device of the first embodiment, so that higher boosting performance can be obtained.

  By using inexpensive general rectifying diodes for the diodes D3 and D4, not only can a sufficient difference in reverse recovery time between the diodes D1 and D2 and the diodes D3 and D4 be secured, but at the same time, a high-speed diode can be realized. Since a circuit loss in the bridge rectifier circuit 2 can be reduced by using a lower forward voltage, a cheaper and more efficient DC power supply device can be obtained.

  Further, when the reactor 3 using the core of the silicon steel plate is used, since an inductance of 5 to 10 times or more is generally obtained in the same volume as that of the dust core, the ripple current of the input current is reduced. As a result, not only the occurrence of common mode noise can be suppressed, but also the generation of normal mode noise can be reduced and the conduction of the generated noise to the power supply line can be further suppressed.

  As described above, the DC power supply device according to the present invention realizes a high power factor and low noise DC power supply device with a simple configuration, such as an air conditioner, a heat pump water heater, a refrigerator, a washing machine, etc. Applicable to electrical appliances powered by an AC power supply.

DESCRIPTION OF SYMBOLS 1 AC power supply 2 Bridge rectifier circuit 3 Reactor 4 Switching means 5 Smoothing capacitor 7 Switching control part 8 Load 10 Voltage detection part 11 Current detection part D1 Diode D2 Diode D3 Diode D4 Diode

Claims (5)

A bridge rectifier circuit that rectifies the AC voltage from the AC power source, a reactor connected between the AC power source and one end of the AC input end of the bridge rectifier circuit, and a reactor connected to the AC input side of the bridge rectifier circuit. Switching means for short-circuiting / opening the AC power supply, a smoothing capacitor connected to the DC output terminal of the bridge rectifier circuit, and a switching control unit for driving the switching means at least twice during the power supply half cycle of the AC power supply. In the DC power supply device that converts the AC voltage of the AC power supply into a DC voltage and supplies it to the load,
Among the diodes (D1, D2, D3, D4) constituting the bridge rectifier circuit, the diode D3 whose anode is connected to the AC input terminal on the side not connected to the reactor is the AC input on the side connected to the reactor The diode D4, which is composed of a diode having a longer reverse recovery time than the diode D2 having the cathode connected to the end and the cathode is connected to the AC input end on the side not connected to the reactor, is connected to the reactor. A DC power supply device comprising a diode having a longer reverse recovery time than a diode D1 having an anode connected to an AC input terminal on the side where the current is input. The reverse recovery time of the diode D3 is longer than the sum of the reverse recovery time of the diode D2 and the attenuation time in the damped oscillation that occurs at the midpoint potential of the diode D1 and the diode D2 immediately after the switching means is turned on, and ,
The reverse recovery time of the diode D4 is longer than the sum of the reverse recovery time of the diode D1 and the attenuation time in the damped oscillation generated at the midpoint potential of the diode D1 and the diode D2 immediately after the switching means is turned on. 2. The DC power supply device according to claim 1, wherein 3. The DC power supply device according to claim 1, wherein the diode D3 and the diode D4 are configured by general rectifying diodes. The switching control unit drives the switching means at a carrier frequency of 15 kHz or more, the reverse recovery time of the diode D1 and the diode D2 is 100 ns or less, and the reverse recovery time of the diode D3 and the diode D4 is 1 μs or more. The DC power supply device according to any one of claims 1 to 3, wherein The direct-current power supply device according to any one of claims 1 to 4, wherein the core of the reactor is formed of a silicon steel plate.