JPS6016190B2 - AC power supply - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an AC power supply, and particularly to an AC power supply having an inverter circuit.

Generally, an AC power supply device with an inverter circuit includes a rectifier circuit that rectifies the AC current from the AC power supply, a smoothing circuit that removes the AC component of the AC current from the rectifier circuit, and a smoothing circuit that converts the DC current from the smoothing circuit into AC current. It consists of an inverter circuit.

The smoothing circuit in the above-mentioned conventional device has a smoothing capacitor for absorbing the alternating current component of the direct current from the rectifier circuit, but when the AC power is turned on and the direct current is supplied from the rectifier circuit to the smoothing circuit, the smoothing circuit If the smoothing capacitor of the circuit is simply connected in series with the rectifier circuit, an inrush current will flow through the smoothing capacitor, which is inconvenient. FIG. 1 shows a conventional example for preventing this rush current. An AC power supply 12 is connected to the input of the rectifier circuit 10, and the rectifier circuit 1
A smoothing circuit 14 is connected to the output of 0.

The smoothing circuit 14 consists of a circuit in which a resistor 16 and a switch 18 are connected in parallel, and a smoothing capacitor 20 connected in series with this circuit, and both ends of the smoothing capacitor 20 serve as an output of the smoothing circuit 14.

Note that the switch 18 has a terminal that is turned on and off by an external signal. When the AC power supply 12 is turned on, the switch 18 is in an open state in advance, and a charging current is supplied from the rectifier circuit 10 via the smoothing capacitor and the resistor 16.

Then, when the charging of the smoothing capacitor 20 is completed and there is no risk of inrush current, an external signal causes the switch 1 to
8 is closed and resistor 16 is shorted. The switch 18 generally consists of a magnetic contactor, and this magnetic contactor is energized by a signal from an external timer circuit after a certain period of time after the AC power supply 12 is turned on, and both ends of the resistor 16 are short-circuited, and the smoothing capacitor 20 is short-circuited. Charging is performed.

FIG. 2 shows a conventional example different from that in FIG. 1, and the difference from FIG. 1 is that the circuit in which the resistor 16 and switch 18 in FIG. The difference is that the diode 24 is replaced with a circuit connected in parallel.

Note that the anode of the diode 24 is connected to the load side of the AC reactor 22. In Fig. 2, AC power supply 12
When the two smoothing capacitors are turned on, the charging current flowing through the two smoothing capacitors is limited by the AC reactor 22, thereby suppressing inrush current.

The diode 24 functions to release the energy stored in the AC reactor 22 between both terminals of the AC reactor 22, thereby suppressing an increase in the terminal voltage of the smoothing capacitor 20. According to the conventional example shown in FIGS. 1 and 2 described above, the resistor 16, the switch 18
, since the AC reactor 22 is required, there is a drawback that the entire device becomes large in size when the load current is large, that is, when the inverter capacity is large.

Furthermore, this has resulted in an increase in the price of the product, which poses an obstacle to cost reduction. The present invention has been made in view of the above-mentioned problems, and its purpose is to provide a small and inexpensive AC power supply device.

In order to achieve the above object, the present invention provides a rectifier circuit having a rectifier that inputs alternating current from a power source and rectifies it;
An alternating current power supply having a smoothing circuit having a smoothing capacitor for removing the alternating current component of the rectifier circuit output current, and an inverter circuit having a transistor circuit that performs on/off operation to convert the direct current output of the smoothing circuit to alternating current. In the double bond, the smoothing circuit is provided with a diode connected with opposite polarity between the smoothing capacitor and the rectifier circuit, and the transistor circuit has a positive side transistor and a negative side transistor. The outer anode of the collector is connected to the cathode of a diode connected to the positive side of the rectifier circuit, and the outer terminal of the emitter is connected to one terminal of a DC reactor that suppresses sudden changes in the main circuit current. The cathode of this diode is connected to the anode of a diode for energy regeneration, and the cathode of this diode is connected to the positive side of a smoothing capacitor, and the transistor on the positive side supplies a charging current to the smoothing capacitor for a certain period of time after the power is turned on by an external on/off signal. It is characterized by supplying a smoothing capacitor to prevent rush current from flowing into the smoothing capacitor.

Preferred embodiments of the present invention will be described below based on the drawings.

Note that the same members as in FIGS. 1 and 2 are designated by the same reference numerals and their explanations will be omitted. FIG. 3 shows a preferred embodiment of the present invention, in which a rectifier circuit 14 is connected to the output of a rectifier circuit 10 supplied with alternating current from an alternating current power source 12. In FIG.

The rectifier circuit 14 consists of a diode 28 and a smoothing capacitor 20, and the cathode of the diode 28 is connected to the positive side of the rectifier circuit 10 to prevent charging current from flowing directly from the rectifier circuit 10 to the smoothing capacitor 201. The smoothing capacitor 20 is composed of an electrolytic capacitor, and the positive terminal (indicated by + in the diagram) of the smoothing capacitor 20 is connected to the anode of the diode, and the negative terminal (indicated by - in the diagram) of the smoothing capacitor 20 is connected to the negative side of the rectifier circuit 10. has been done.
The cathode of the diode 28 and the negative electrode of the smoothing capacitor 20 are connected from the cathode of the diode 28 to the diode 30-1 → positive side transistor 31-1 → DC reactor 32-1 for suppressing sudden changes in the main circuit current → diode 34-1.
→A circuit for energy regeneration in which the negative side transistors 36-1 are connected in this order, the cathode is connected to the connection point between the transistors 3-1-1 and the DC reactor 32, and the anode is connected to the negative electrode of the smoothing capacitor 20. Diode 38-1, DC reactor 32-1, and diode 34
The anode is connected to the connection point with the smoothing capacitor 2
a first transistor circuit 4 consisting of a diode 40 for energy regeneration whose cathode is connected to the positive electrode of the transistor 4;
1-1 are connected.

The collector of a transistor 31 is connected to the cathode of the diode 30, and the collector of a transistor 36-1 is connected to the power source of the diode 34-1. The diodes 38-1 and 40-1 used for energy regeneration clamp the voltage generated in the DC reactor 32-1 during switching of the corresponding transistors 31-1 and 36-1, respectively, and transfer the energy to the smoothing capacitor 2. It has the function of regenerating by bypassing the river.

A second transistor circuit 41-2 and a third transistor circuit 41-3 having a similar configuration are connected in parallel to the first transistor circuit 41-1 having the above configuration. 26 consists of first, second, and third transistor circuits.

Note that the same members as those in the first transistor circuit are given the same reference numerals. Note that each transistor 30-1, 30-2,
A control circuit 42 is connected to the bases of 30-13, 36-1, 36-2, and 36-3 as described later.

A preferred embodiment of the present invention has the above configuration, and its operation will be explained below.

As mentioned above, the control circuit 42 is connected to each transistor of the inverter circuit 26, and FIG. 4 shows this connection diagram.

The control circuit 42 includes transistors 30-1, 30-2, 30-3 and 36-1, 36-2 of the inverter circuit 26.
, 36-3, an oscillation circuit 46 that outputs pulses to the base control circuit 44, and a fixed time base control circuit 44 and oscillation circuit 46 after the AC power supply 12 is turned on. Timer 4 outputs timer output to base control circuit 44 and oscillation circuit 46 to turn on
It consists of 8.

Further, FIG. 5 shows a waveform diagram of each part of the control circuit 42, and the waveform 100 is the output waveform of the timer 48, and the waveform 102
indicates the output waveform of the oscillation circuit 46, and waveform 104 indicates the output waveform of the base control circuit 44.

When the AC power supply 12 is turned on, the timer 48 is turned on, and the timer output shown in waveform 100 is supplied to the base control circuit 44 and the oscillation circuit 46, and the base control circuit 44 receives a pulse shown in the waveform 102 of the oscillation circuit 46. is supplied.

As a result, the base control circuit 44 supplies a pulse shown in waveform lo4 only to the transistor 31-1, and the transistor 31-1 is controlled to be turned on or off. As the transistor 31-1 turns on and off, the diode 30-1 becomes the transistor 3-1 as shown by the broken line in FIG.
-1→DC reactor 32-1→diode 40-1→
A charging current flows in the order of the positive electrode of the smoothing capacitor 20, and the smoothing capacitor 20 is charged. As described above, according to the present invention, after the AC power supply 12 is turned on and before the inverter circuit 26 performs its control operation, the externally provided control circuit 42 controls the positive side transistor 31 for a certain period of time determined by the timer 46. 11 is turned on and the smoothing capacitor 20 is sufficiently charged through the above-mentioned path, and then the operation of the inverter circuit 26 is started, so it is possible to ensure that an inrush current is supplied from the power supply to the smoothing capacitor during operation. This can be reliably prevented, and as a result, there is no need for resistors, switches, DC reactors, etc. that were conventionally required, and the device can be made smaller and lower in price.

As mentioned above, the smoothing circuit includes a diode 28 that prevents direct charging of the smoothing capacitor from the rectifier circuit, thereby ensuring that the smoothing capacitor 20 is prevented from receiving a large charging current directly from the rectifier circuit 10. ing. FIG. 6 shows an output current waveform diagram of the transistor 31-1, and FIG. 7 shows the charging characteristics of the smoothing capacitor 20.

The rectangular axes in FIGS. 6 and 7 are the same time axis, the vertical axis in FIG. 6 represents the output current of the transistor 31-1, and the vertical axis in FIG. 7 represents the terminal voltage of the smoothing capacitor 20. , it can be understood that the smoothing capacitor 20 is charged by the output current of the transistor 31-1.

Note that the DC reactor 32-1 is connected in series to the transistors 31-1, and prevents the charging current from becoming excessive, thereby preventing the transistors of the inverter circuit 26 from being destroyed.

The above explanation describes the charging action of the smoothing capacitor 20 at the time of starting the device, but after the circuit starts,
Like a normal smoothing circuit, the smoothing capacitor 20 is intended to absorb surge voltage or regenerate energy at each switching time of the inverter circuit 26, and as described above, each positive and negative regenerated energy is transferred from the diode 40 or 38 to the smoothing capacitor. 2 Rivers are returned.

When the power supply voltage drops, the smoothing capacitor 2
The charged charges are discharged from the diode 28 toward the main circuit, thereby making it possible to compensate for a drop in the power supply voltage. As explained above, according to the present invention, by controlling the transistors of the inverter circuit of an AC power supply having an inverter circuit on and off by an external control circuit, the smoothing capacitor 20 is charged in advance in a very simple manner, thereby preventing inrush current. It became possible.

As a result, even if the inverter capacity increases, the circuit for preventing inrush current does not become larger.
Since there are no contacts, it is possible to provide a small, inexpensive, and highly reliable AC power supply device.

[Brief explanation of the drawing]

1 and 2 are circuit diagrams showing a conventional example of smoothing capacitor inrush current prevention, FIG. 3 is a circuit diagram showing a preferred embodiment of the present invention, and FIG. 4 is a circuit diagram showing each transistor of the inverter circuit 26. Connection diagram with control circuit 42, FIG. 5 shows control circuit 4
2 shows the waveform diagram of each part, FIG. 6 shows the output current waveform diagram of the transistors 31-1, and FIG. circuit, 14 is a smoothing circuit, 20 is a smoothing capacitor, 26
Inverter circuit, 28, 30, 38 are diodes, 3
1 is a transistor, 32 is a DC reactor, 42 is a control circuit, 44 is a base control circuit, 46 is an oscillation circuit, and 48 is a timer. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7

Claims (1)

[Claims] 1. A rectifier circuit that has a rectifying element that inputs alternating current from a power source and rectifies it, a smoothing circuit that has a smoothing capacitor that removes the alternating current component of the rectifier circuit output current, and converts the direct current output of the smoothing circuit to alternating current. an inverter circuit having a transistor circuit that performs on/off operations to It has a positive side transistor and a negative side transistor, and the collector of the positive side transistor is connected to the cathode of a diode whose anode is connected to the positive side of the rectifier circuit, and the emitter suppresses sudden changes in the main circuit current. It is connected to one terminal of a DC reactor, the other end of this DC reactor is connected to the anode of a diode for energy regeneration, the cathode of this diode is connected to the positive side of a smoothing capacitor, and the transistor on the positive side is connected to an external An AC power supply device characterized in that a charging current is supplied to a smoothing capacitor for a certain period of time after power is turned on in response to an on/off signal from a power source, thereby preventing rush current from flowing into the smoothing capacitor.