JP4275223B2 - Power supply - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement of a power supply apparatus that uses a commercial AC power supply as input, rectifies and smoothes it, converts it appropriately, and supplies power to a load.
[0002]
[Prior art]
FIG. 4 is a connection diagram showing a power supply apparatus that converts a conventional DC power source into high-frequency AC power of several KHz to several tens KHz by an inverter circuit and outputs it. In the figure, reference numeral 1 denotes an AC power source, and a single-phase commercial AC power source or a three-phase commercial AC power source is used. Reference numeral 2 denotes a rectifier circuit that rectifies power from the AC power source 1 and converts it into DC, and is composed of diodes 3 to 6. C1 is a capacitor that smoothes the output of the rectifier circuit 2, and 7 is an inverter circuit that converts the output of the capacitor C1 into high-frequency AC power and supplies it to a load (not shown). Reference numeral 13 denotes an inverter control circuit that outputs a drive signal for alternately switching on the switching elements constituting the inverter circuit 7. In the figure, the output of the AC power source 1 is rectified by the rectifier circuit 2, smoothed by the capacitor C 1, and converted into high-frequency AC power by the inverter circuit 7.
[0003]
4, the capacitor C1 because the maximum value of the output of the rectifier circuit 2 is charged, about 1.4 times the voltage of the effective output voltage of the AC power supply 1 is supplied to the inverter circuit 7. Therefore, when the output of the AC power supply 1 is 200 to 230 V (hereinafter referred to as a 200 V system), the rectified and smoothed voltage is 280 to 322 V. Therefore, the rated voltage of each element used in the inverter circuit 7 is 600 V. Things are used. In addition, when the output of the AC power supply 1 is 380 to 460 V (hereinafter referred to as 400 V system), the rectified and smoothed voltage is 532 to 644 V, so the rated voltage of each element used in the inverter circuit 7 is 1000 V Or the thing of 1200V is used.
[0004]
[Problems to be solved by the invention]
In the above conventional apparatus, the AC power supply 1 is 200V system and 400V system, and the elements used for the inverter circuit 7 and, for example, an inverter transformer for transforming the output of the inverter circuit 7 connected to the inverter circuit 7 and the like. Since these parts must be prepared, there is a problem that the cost is increased.
[0005]
[Means for Solving the Problems]
The invention according to claim 1 is a series circuit comprising a rectifier circuit that uses a commercial AC power supply as an input, rectifies the output of the commercial AC power supply into a DC, and two capacitors connected between the output terminals of the rectifier circuit. A first switching element having one terminal connected to the positive output terminal of the series circuit, a second switching element having one terminal connected to the negative output terminal of the series circuit, and a first switching element A first diode connected between the other terminal of the element and the series connection point of the series circuit; and a second diode connected between the other terminal of the second switching element and the series connection point of the series circuit. Between the smoothing circuit connected between the connection point between the diode, the first switching element and the first diode, and the connection point between the second switching element and the second diode, and between both terminals of the smoothing circuit Input power connected to An output conversion circuit for converting the characteristic suitable to the load, at the same time when the first and the commercial AC power source and a switching element and second switching element a predetermined conduction time ratio is a system of low voltage, commercial AC power source Is a high voltage system , a switching element control circuit that alternately performs ON-OFF control without overlapping each other, and when the commercial AC power supply is a low voltage system, two capacitors are connected in parallel to provide a commercial AC power supply. When the system is a high-voltage system, the power supply device includes a changeover switch in which two capacitors are connected in series .
[0007]
According to a second aspect of the invention, the switching element control circuit, to claim 1, which is a circuit for determining the ON-OFF time ratio in accordance with the difference between the detected value of the output voltage or output current of the smoothing circuit and the set value It is a power supply device of description.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a connection diagram showing an example of an embodiment of the present invention. In the figure, reference numeral 1 denotes an AC power source, and a single-phase commercial AC or a three-phase commercial AC power source is used. Reference numeral 2 denotes a rectifier circuit that rectifies power from the AC power source 1 and converts it into DC, and is composed of diodes 3 to 6. C2 and C3 are series capacitors connected between the output terminals of the rectifier circuit 2, and the capacitances of the capacitors C2 and C3 are set equal. Reference numerals 8 and 9 denote switching elements, and reference numeral 14 denotes a switching element control circuit for controlling a conduction time ratio between the switching elements 8 and 9. When the voltage of the commercial AC power supply 1 is low, both are used simultaneously. When the voltage of 1 is a high voltage, a drive signal for alternately repeating ON and OFF at a predetermined conduction time rate and frequency is output without overlapping both. Reference numerals 10 and 11 denote diodes, C4 denotes a smoothing capacitor, and 7 denotes an inverter circuit that converts the output of the capacitor C4 into high-frequency AC power and supplies it to a load (not shown). Reference numeral 13 denotes an inverter control circuit that outputs a drive signal for alternately switching on the switching elements constituting the inverter circuit 7.
[0009]
In FIG. 1, a case where a commercial AC power supply of 400V system is used will be described. First, while the switching element 8 is ON and the switching element 9 is OFF, the output of the AC power supply 1 is rectified by the rectifier circuit 2, and the output of the rectifier circuit 2 is rectified circuit 2 → switching element 8 → inverter circuit 7. → Diode 11 → Capacitor C3 → Rectifier circuit 2 At this time, the voltage supplied to the inverter circuit 7 becomes the charging voltage of the capacitor C2, and when the capacitors C2 and C3 have the same capacity, the output of the AC power source 1 is rectified and smoothed by half. Voltage. Next, while the switching elements 8 and 9 are OFF, the power charged in the capacitor C4 flows through the path of the capacitor C4 → the inverter circuit 7 → the capacitor C4. Next, while the switching element 8 is OFF and the switching element 9 is ON, the output of the AC power supply 1 is rectified by the rectifier circuit 2, and the output of the rectifier circuit 2 is rectified circuit 2 → capacitor C2 → diode 10 → It flows through the path of the inverter circuit 7 → the switching element 9 → the rectifier circuit 2. At this time, the voltage supplied to the inverter circuit 7 becomes a charging voltage of the capacitor C3, and becomes a voltage half that of a voltage obtained by rectifying and smoothing the output of the AC power supply 1. As a result, a voltage ½ of the voltage obtained by rectifying and smoothing the output of the AC power supply 1 is always supplied to the inverter circuit 7.
[0010]
Note that if the ON and OFF repetition frequency of the switching elements 8 and 9 is set high, the capacitance of the capacitor C4 can be reduced.
[0011]
Next, when using a 200V commercial AC power supply, the switching elements 8 and 9 are simultaneously turned ON, whereby the inverter circuit 7 can be supplied with the entire voltage obtained by rectifying and smoothing the AC power supply 1. As a result, substantially the same voltage is supplied to the inverter circuit 7 in the 200V system and the 400V system.
[0012]
FIG. 2 is a connection diagram showing an example of another embodiment of the present invention. In the figure, 12 is a reactor, 15 is an output voltage setting device, 16 is an output voltage detector, and 17 is a comparator. The other components having the same functions as those of the apparatus shown in FIG. In the same figure, the reactor 12 can restrict | limit the peak value of the electric current which flows into the capacitor | condenser C2 or C3, and can make the rating of the capacitor | condensers C3 and C4 small. Furthermore, the reactor 12 can limit the peak value of the current flowing through the switching elements 8 and 9, and can protect the switching elements 8 and 9 from overcurrent.
[0013]
In FIG. 2, the output voltage is detected by the output voltage detector 16, the detection signal Vf is compared with the setting signal Vr of the output voltage setting device 15 by the comparator 17, and the difference signal ΔV = Vr−Vf is switched. It is supplied to the element control circuit 14. The switching element control circuit 14 determines the output pulse width so as to have a conduction time ratio corresponding to the input signal ΔV, and drives the switching elements 8 and 9. As a result, the output voltage is feedback-controlled so as to be maintained at a value corresponding to the set value of the output voltage setting unit 15, which is sufficient for fluctuations in the output voltage and load of the commercial AC power supply 1. A stable output voltage can be supplied to the inverter circuit 7. In the figure, other operations are the same as those of the apparatus shown in FIG.
[0014]
When the output voltage is fed back and controlled to match the set value as shown in FIG. 2, a power conversion circuit that converts this output into a characteristic suitable for the load, the inverter circuit 7 shown in FIG. Since a specific voltage is always supplied regardless of the voltage of the commercial AC power supply, these circuits need only have a single voltage rating, so that the circuit can be standardized.
[0015]
FIG. 3 is a connection diagram showing an example of still another embodiment of the present invention. In the figure, reference numerals 18 and 19 denote change-over switches, and the other parts having the same functions as those of the apparatus shown in FIG. In the figure, when the 200V system is used as the AC power source 1, the changeover switches 18 and 19 are switched to the A side, the capacitors C2 and C3 are connected in parallel, and when the 400V system is used as the AC power source 1, the switching is performed. The switches 18 and 19 are switched to the B side, and the capacitors C2 and C3 are connected in series. As a result, it is possible to equalize the ability to reduce the voltage ripple due to the capacitors C2 and C3 when both the 200V system and the 400V system are used as the AC power supply 1.
[0016]
When the constant current characteristic is used to maintain the output current at the set value, the output voltage setter 15 is an output current setter and the output voltage detector 16 is an output current detector, whereby the difference signal between the two is compared. 17 and the pulse width of the switching element control circuit 14 may be determined based on the difference signal. Further, in order to match the output voltage and output current of the inverter circuit 7 with the target values, the inverter control circuit 13 may have an output feedback control function. In FIG. 2, the output voltage detector 16 is replaced with an inverter circuit. 7 so that the switching element control circuit 14 can control the final output if the conduction time rate of the switching elements 8 and 9 is determined by the difference between the detected value and the set value. Become. In this case, the inverter control circuit 13 may simply use the one that determines the operating frequency of the inverter circuit 7 and performs ON-OFF control at a constant time rate.
[0017]
【The invention's effect】
As described above, the power supply device of the present invention transforms the elements to be used for the inverter circuit 7 and, for example, the output of the inverter circuit 7 connected to the inverter circuit 7 when the AC power supply 1 is a 200V system and a 400V system. Parts such as inverter transformers can be used in common, and it is not necessary to use different models using parts corresponding to the 200V system and 400V system. Since it can be applied, the production cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a connection diagram illustrating an example of an embodiment of the present invention.
FIG. 2 is a connection diagram illustrating an example of another embodiment of the present invention.
FIG. 3 is a connection diagram showing still another example of the embodiment of the present invention.
FIG. 4 is a connection diagram showing a conventional power supply device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 AC power supply 2 Rectifier circuit 3, 4, 5, 6 Diode 7 Inverter circuit 8, 9 Switching element 10, 11 Diode 12 Reactor 13 Inverter control circuit 14 Switching element control circuit 15 Output voltage setting device 16 Output voltage detector 17 Comparator 18, 19 changeover switch

Claims (2)

A rectifier circuit having a commercial AC power supply as an input and rectifying the output of the commercial AC power supply into a direct current;
A series circuit composed of two capacitors connected between the output terminals of the rectifier circuit;
A first switching element having one terminal connected to the positive output terminal of the series circuit;
A second switching element having one terminal connected to the negative output terminal of the series circuit;
A first diode connected between the other terminal of the first switching element and a series connection point of the series circuit;
A second diode connected between the other terminal of the second switching element and a series connection point of the series circuit;
A smoothing circuit connected between a connection point between the first switching element and the first diode and a connection point between the second switching element and the second diode;
An output conversion circuit that converts input power connected between both terminals of the smoothing circuit into a characteristic suitable for a load;
The first switching element and the second switching element are connected to each other at a predetermined conduction time ratio and when the commercial AC power source is a low-voltage system , and simultaneously when the commercial AC power source is a high-voltage system. A switching element control circuit that performs ON-OFF control alternately without performing ,
A switch for connecting the two capacitors in parallel when the commercial AC power source is a low-voltage system and for connecting the two capacitors in series when the commercial AC power source is a high-voltage system; Power supply. 2. The power supply device according to claim 1, wherein the switching element control circuit is a circuit that determines an ON-OFF time ratio in accordance with a difference between a detected value of the output voltage or output current of the smoothing circuit and a set value.

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