JP2009033814A - Dc power supply device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a DC power supply device simplifying a protection circuit for a converter circuit and reducing a mounting area, a cost and a loss. <P>SOLUTION: A series connection circuit connecting two inverse parallel connection circuits of switching elements 3a and 3b and diodes 4a and 4b in series and the series connection circuit connecting the diodes 4c and 4d in series are connected in parallel, and a reactor 2 is connected between each internal connection point of the series connection circuits and an AC power supply respectively. A switching element overcurrent detecting means 9 and a switching-element control means 8 controlling an input current waveform to be an approximately positive-negative symmetric input current waveform are fitted. Consequently, since the protection circuit can be simplified by making the current rating of the switching element 3a not detecting a flowing current by a current detector 5 larger than that of the switching element 3b detecting the flowing current by the current detector 5, the cost and the loss can be reduced. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a DC power supply apparatus that uses a circuit that converts AC power to DC power and supplies power to the apparatus, system, etc. with high power factor and low distortion.

  As a conventional DC power supply device that achieves low distortion with high power factor and suppressed harmonics, a bridge type power factor correction circuit has been devised in which resistors are respectively inserted in series with two switch elements (for example, patents) Reference 1).

  FIG. 6 shows a conventional DC power supply device described in Patent Document 1. In FIG. As shown in FIG. 6, the bridge includes four rectifying elements 22, 23, 24, 25 and one capacitor 28 connected to a single-phase AC power source via an inductor 21 to supply DC power to a load. A full-wave rectifier circuit and two switch elements 24 and 25 connected in parallel to two rectifier elements whose input terminals are connected to the capacitor 28 among the rectifier elements 22, 23, 24 and 25 are provided. Yes.

  The switch elements 24 and 25 are composed of MOSFETs, and the body diodes of the MOSFETs serve as rectifier elements.

  First and second resistors 26 and 27 shown in FIG. 6 are current detection resistors. A first resistor 26 and a second resistor 27 are inserted in series in the series circuit of the switch elements 24 and 25 and the rectifier elements 22 and 23, respectively, so that the voltage of the first resistor 6 is half-wave rectified. The outputs of the wave rectifier circuit 29, the second half wave rectifier circuit 30 that half-wave rectifies the voltage of the second resistor 27, and the outputs of the first half-wave rectifier circuit 29 and the second half-wave rectifier circuit 30 are added. An adder circuit 31 is provided.

  The power factor correction circuit controls the input current waveform so as to be similar to the input voltage and operates so as to keep the output voltage constant. At this time, waveforms of currents flowing through the resistors 26 and 27 are as shown in FIGS.

  In FIG. 6, if the direction from the top to the bottom is positive, the currents of the resistors 26 and 27 are switched on the positive side, but are continuous on the negative side. In the case where the current is on the positive side, whether the current flows or not is determined depending on whether the switch elements 24, 25 are turned on or off. , 25 to flow through. In the case of FIG. 6, since the switch elements 24 and 25 are MOSFETs, current flows through the body diode, and therefore, the switch elements 24 and 25 are continuous.

When this waveform is input to the half-wave rectifier circuits 29 and 30 and only the negative current continuation portion is taken out, the result is as shown in FIGS. Then, by adding the two waveforms shown in FIGS. 7C and 7D, a target input current waveform diagram 7E is obtained.
JP 2003-333855 A

  However, although the above-described conventional DC power supply device has relatively good characteristics, since the resistance is inserted in each of the two switching elements, the number of parts is increased on the circuit, and the cost and loss are increased.

  Furthermore, when the conventional technology is applied in a circuit configuration with switching elements above and below as shown in FIG. 6 and a protection circuit is configured using the upper and lower resistances, the connection point between the upper and lower switching elements is the potential at each switching operation. Since the upper protection circuit is significantly more complicated than the lower circuit, the number of components is increased, and the mounting area, cost, and loss are increased.

  The DC power supply device of the present invention solves the conventional problems, and an object thereof is to provide a DC power supply device that can reduce the mounting area, cost, and loss by simplifying the protection circuit.

  In order to solve the above-mentioned problem, the DC power supply device of the present invention includes any two switching arms including a switching arm having a reverse parallel connection circuit of switching elements and diodes or switching elements having a reverse conduction function. A plurality of series connection circuits including the same ones in a form including a switching element in a series connection circuit in which two diodes are connected in series, and including the same elements. A capacitor and a load are connected in parallel between the parallel connection points, and a reactor is connected between each internal connection point of each of the plurality of series connection circuits and the AC power supply, and flows to at least one switching element of the plurality of series connection circuits. Current detector that detects current and switching element overcurrent detection that judges whether or not it is overcurrent based on the detection value of current detector And the current rating of the switching element that does not detect the current flowing in the current detector among the plurality of series connection circuits is larger than the current rating of the switching element that detects the current flowing in the current detector. And switching element control means for controlling the switching element so as to obtain a substantially positive and negative symmetrical current waveform.

  As a result, the current rating of the switching element that does not detect the current flowing through the current detector is made larger than the current rating of the switching element that detects the current flowing through the current detector. Since the overcurrent detection works before the current rating of the switching element that does not detect the current flowing through the device is exceeded, the protection circuit can be simplified, and the mounting area, cost, and loss can be reduced.

  In the DC power supply device of the present invention, the current rating of the switching element that does not detect the current flowing by the current detector is made larger than the current rating of the switching element that detects the current flowing by the current detector, so that the overcurrent is reduced. Since overcurrent detection works before exceeding the current rating of the switching element that does not detect the current flowing by the current detector even if it flows, the protection circuit can be simplified, and the mounting area, cost, and loss can be reduced.

A first aspect of the present invention is a direct current power supply device that generates direct current from an alternating current power supply by a switching operation, and includes the same ones among a switching arm composed of an antiparallel connection circuit of a switching element and a diode or switching elements having a reverse conduction function. A plurality of series connection circuits including the same ones in a series connection circuit in which any two are connected in series and a series connection circuit in which two diodes are connected in series are included in parallel, A capacitor and a load are connected in parallel between parallel connection points of the series connection circuit, and a reactor is connected between each internal connection point of the plurality of series connection circuits and the AC power source, and at least one of the plurality of series connection circuits is connected. A current detector that detects the current flowing through the switching element and whether the overcurrent is detected by the detected value of the current detector Switching element overcurrent detection means to judge and current rating of the switching element that does not detect the current flowing in the current detector among the plurality of serial connection circuits Current rating of the switching element that detects the current flowing in the current detector A switching element control means for controlling the switching element so as to obtain a substantially positive and negative symmetrical current waveform.

  As a result, the current rating of the switching element that does not detect the current flowing through the current detector is made larger than the current rating of the switching element that detects the current flowing through the current detector. Since the overcurrent detection works before the current rating of the switching element that does not detect the current flowing through the device is exceeded, the protection circuit can be simplified, and the mounting area, cost, and loss can be reduced.

  The second invention is a current detector that detects a current flowing through at least one switching element among the plurality of series connection circuits of the first invention, and controls the input current. Thereby, overcurrent detection and input current control can be implemented with one current detector.

  In particular, the third invention uses a shunt resistor as a current detector for detecting a current flowing in at least one switching element among the plurality of series connection circuits of the first or second invention. As a result, the protection circuit can be simplified, and the mounting area, cost, and loss can be reduced.

  In the fourth invention, in particular, the switching element that detects the current flowing by the current detector according to any one of the first to third inventions is configured by a MOSFET, and its on-resistance is used. Thereby, since the current detector can be eliminated, the number of parts can be reduced, and the mounting area, cost and loss can be reduced.

  In particular, the fifth invention is provided with the temperature detection means in the vicinity of the MOSFET itself or the MOSFET of the fourth invention. As a result, the on-resistance of the MOSFET can be protected with higher accuracy by correcting the temperature characteristics.

  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 configuration diagram illustrating a DC power supply device according to a first embodiment of the present invention. In FIG. 1, a series connection circuit composed of an antiparallel connection circuit of switching elements 3 a, 3 b and diodes 4 a, 4 b from the output end of the AC power source 1 via the reactor 2, and the reactor 2 from the output end of the AC power source 1. It is input to a bridge circuit composed of a series connection circuit composed of diodes 4c and 4d that do not pass through.

  A smoothing capacitor 6 and a load 7 are connected to the output of the bridge rectifier circuit. Further, the switching element control means 8 outputs appropriate pulse signals of the switching elements 3a and 3b so that the input current waveform has a substantially positive / negative symmetrical current waveform.

  Next, the operation when an overcurrent flows will be described. FIG. 2 shows the current waveform of each part when overcurrent flows in FIG. 1. Here, the current detector 5 is connected in series to the antiparallel connection circuit of the switching element 3b and the diode 4b. explain.

In FIG. 2, if a current exceeding the overcurrent detection level starts flowing when the input current is negative (section (1)), the current rating of the switching element 3b is equal to the current rating of the switching element 3a and the overcurrent detection level. If there is no means for detecting an overcurrent in the path flowing through the switching element 3b, a current exceeding the current rating of the switching element 3b flows, which may result in spec over.

  However, in an overcurrent state in which the input current gradually increases, the negative current of the input current (section (1)) is set by making the current rating of the switching element 3b larger than the current rating of the switching element 3a and the overcurrent detection level. When the specification does not sometimes exceed and the input current shifts to the positive current (section (2)), the current detector 5 detects the overcurrent and makes an abnormality determination.

  On the other hand, when the current exceeding the overcurrent detection level starts flowing when the input current is positive, the overcurrent flows through the path of the switching element 3a. Therefore, the overcurrent is detected before shifting to the negative current of the input current. Make an abnormality judgment.

  By doing so, even if the current detector 5 is not inserted into both of the switching elements 3a and 3b, the current detector 5 is inserted in series with at least one switching element, and the current detector 5 is not inserted. If the current rating of the switching element 3a is larger than the current rating of the switching element 3b and the overcurrent detection level, only one set of protection circuits is required, and the mounting area can be reduced.

  In addition, it is considered that the overcurrent detection level should be set sufficiently lower than the current rating of the switching elements 3a and 3b. However, since the maximum output capability is lowered in this case, the overcurrent detection level is set here as the switching element 3b. It is desirable to set a value that does not exceed the current rating.

  Although the case where the current detector 5 is inserted in series with the switching element 3b has been described here, the current detector 5 is inserted into the switching element 3a, and the current rating of the switching element 3b is set to the current rating of the switching element 3a, and By making it larger than the overcurrent detection level, the same operation is performed.

  However, in the converter circuit having the upper and lower switching elements 3a and 3b as shown in FIG. 3, the potential at the connection point of the upper and lower switching elements changes every time the switching operation is performed, so that the normal protection circuit is complicated and difficult.

  However, the mounting area, cost, and loss can be reduced by increasing the current rating of the switching element 3a and simplifying the protection circuit.

  Further, the bridge portion of the converter circuit is not limited to FIG. 1, and as shown in FIG. 3, four sets of switching elements 3a, 3b, 3c, 3d and diodes 4a, 4b, 4e, 4f connected to the reactor 2 are provided. The converter circuit comprised by these antiparallel circuits may be sufficient.

  The operation when an overcurrent flows is the same as in FIG. 1. For example, when the current detector 5 is inserted in the switching element 3b, the current ratings of the switching elements 3a, 3c, and 3d. Is made larger than the current rating of the switching element 3b and the overcurrent detection level, and the same can be applied to a converter circuit using four switching elements as shown in FIG.

(Embodiment 2)
In the second embodiment, the input current is controlled by the current detector 5 of the first embodiment. The detection value of the current detector 5 is a half-wave rectified waveform, but the switching is performed so that the half-wave current waveform flowing in the other path not passing through the current detector 5 has the same tendency as the detection value of the current detector 5. Control the element. That is, based on the current waveform detected by the current detector 5, the input current waveform is controlled so as to be similar to the target input current waveform that is roughly symmetric.

  As described above, since the overcurrent detection and the input current control can be performed by the single current detector 5, the number of parts does not increase, so that the mounting area, cost, and loss can be reduced.

(Embodiment 3)
In the third embodiment, a shunt resistor is used as the current detector 5 of the first or second embodiment. FIG. 4 is a configuration diagram of a DC power supply device using the shunt resistor according to the third embodiment of the present invention.

  In FIG. 4, a shunt resistor is inserted in series with the switching element 3b, and the overcurrent detection is performed using a comparator. The current flowing through the switching element 3b by the shunt resistor is detected at the voltage level. The voltage between the shunt resistors and the reference voltage (Vref) are compared, and if the voltage between the shunt resistors is excessive, the output of the comparator becomes active Hi (or active Lo), and it is assumed that an overcurrent has occurred, and the protection circuit To work.

  By using a shunt resistor as the current detector 5, a circuit can be easily assembled with the addition of a comparator and several resistors and capacitors, so that the protection circuit can be simplified, and the mounting area, cost and loss are reduced. can do.

(Embodiment 4)
In the fourth embodiment, the switching element that detects the current with the current detector 5 of the first to third embodiments is configured by a MOSFET. FIG. 5 is a configuration diagram of a DC power supply device using the MOSFET according to the fourth embodiment of the present invention.

  In FIG. 5, the drain-source voltage when the MOSFET is turned on is detected, the drain-source voltage and the reference voltage (Vref) are compared, and if the drain-source voltage is excessive, the comparator The output becomes active Hi (or active Lo), and the protection circuit is operated assuming that an overcurrent has occurred.

  By doing so, the protection circuit can be configured without using the current detector 5, so that the mounting area, cost, and loss can be reduced.

  Further, as shown in FIG. 5, a MOSFET or a nearby temperature detecting means is provided to correct the temperature characteristics of the on-resistance of the MOSFET. By correcting variations in on-resistance due to temperature, variations in on-resistance are reduced, so variations in drain-source voltage are also reduced, and the reference voltage (Vref) can be designed with reduced variations.

  In other words, it is possible to protect with higher accuracy by correcting the temperature characteristic of the on-resistance.

  As described above, the direct current power supply device according to the present invention can detect overcurrent protection with a simple configuration by detecting a current flowing through at least one switching element. Applicable to.

Configuration diagram of DC power supply apparatus according to Embodiment 1 of the present invention The wave form diagram which shows each current waveform in Embodiment 1 of this invention Configuration diagram of DC power supply device according to another aspect of embodiment 1 of the present invention Configuration diagram of DC power supply apparatus according to Embodiment 3 of the present invention Configuration diagram of DC power supply apparatus according to Embodiment 4 of the present invention Configuration diagram according to an example of a conventional DC power supply device Waveform diagram showing each current waveform according to an example of a conventional DC power supply device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 AC power supply 2 Reactor 3a, 3b, 3c, 3d Switching element 4a, 4b, 4c, 4d, 4e, 4f Diode 5 Current detector 6 Smoothing capacitor 7 Load 8 Switching element control means 9 Switching element overcurrent detection means 10 Shunt resistance 11 Comparator 12 MOSFET
13 Temperature detection and temperature correction means

Claims (5)

In a direct current power supply device that generates direct current from an alternating current power supply by switching operation, any two of the switching arms including reverse parallel connection circuits of switching elements and diodes or switching elements having a reverse conduction function are included. A series connection circuit connected in series and a plurality of series connection circuits including the same elements in a form including a switching element in a series connection circuit in which two diodes are connected in series are connected in parallel, and the plurality of series connection circuits A capacitor and a load are connected in parallel between parallel connection points, a reactor is connected between each internal connection point of each of the plurality of series connection circuits and an AC power supply, and at least one switching element of the plurality of series connection circuits A current detector that detects the current flowing through the Switching element overcurrent detection means for determining whether the current flowing in the current detector is detected based on the current rating of the switching element that does not detect the current flowing in the current detector among the plurality of series-connected circuits A DC power supply device comprising switching element control means for controlling a switching element so as to obtain a current waveform that is substantially positive and negative symmetrical and is larger than the current rating of the element. 2. The DC power supply device according to claim 1, wherein an input current is controlled by detecting a current flowing through at least one switching element among the plurality of series connection circuits. The DC power supply device according to claim 1 or 2, wherein a current flowing through at least one switching element among the plurality of series connection circuits is detected by a shunt resistor. The DC power supply device according to any one of claims 1 to 3, wherein a switching element that detects a current flowing through a current detector among a plurality of series connection circuits is configured by a MOSFET. 5. The DC power supply device according to claim 4, further comprising a temperature detection means in the vicinity of the MOSFET or in the vicinity of the MOSFET, and correcting the temperature characteristic of the on-resistance of the MOSFET.