JPS6016120Y2 - Inrush current prevention circuit - Google Patents

Description

[Detailed description of the invention] The present invention closes the power switch that connects the AC power supply and the gate of the first bidirectional switching element to make the bidirectional switching element a closed circuit, thereby allowing the AC power supply to pass through the charging resistor to the load. At the same time, a control circuit that detects changes in the load and performs sequence control is operated, and after a certain sequence control time, a contact that operates in conjunction with the control circuit is closed. After the AC power supply voltage is applied to the gate of the second bidirectional switching element to close the bidirectional switching element and the AC power supply is directly connected to the load, the inrush current that occurs when the power switch is turned on is The goal is to prevent

When a power switch is turned on by an AC-DC converter connected to an AC power source, a rush current is generated in the AC power source.

In a commonly used AC-DC converter as shown in FIG. 1, an AC power source is connected to a gate G of a bidirectional switching element 2 via a current limiting resistor B and a power switch 1, and an anode A1 is connected to the gate G of a bidirectional switching element 2. The other anode was connected to a rectifying element 3, and the DC power at both ends of the filtering capacitor C□, which was rectified by the rectifying element 3, was connected to a load 4.

When the switch 1 is closed, the power to the gate G is applied, the bidirectional switching element (TRIAC) 2 becomes conductive, and the AC power becomes a DC power at the rectifier 3, forming an AC-DC power converter.

At this time, when the switch 1 is closed, the filtering capacitor C□ connected to the load side is rapidly charged, so the charging current causes an instantaneous inrush current 5 to flow into the input AC power supply as shown in Figure 2 when the switch is turned on. After t, a stable normal alternating current flows.

Since this inrush current is extremely large, it causes voltage fluctuations in the power supply, affecting other electrical appliances that also use the AC power line, and bidirectional switching element 2 and current element 3 become momentarily overloaded, causing surges. destroyed by electric current,
It had drawbacks such as accelerating deterioration.

In order to eliminate these drawbacks, the present invention detects changes in load voltage or current after closing the main power switch, slowly charges the filter capacitor, and automatically operates other switches after charging is complete. The objective is to obtain a circuit that reduces inrush current when the load is fully loaded.

To explain the present invention with reference to Fig. 3, the AC power supply connector A-
Connect an AC power supply between B.

Since the switch is open, bidirectional switching elements (triacs) 2 and 5 are open and no alternating current flows.

However, when the switch 1 is closed, a voltage is applied to the gate G' of the bidirectional switching element 5 through the current limiting resistor R0, and the anodes A□' and A2' of the bidirectional switching element 5 are
The voltage between the connection points C and D becomes the same as that between the AC power supplies A and B.

However, since the bidirectional switching element 2 is in an open state, the AC voltage passes through the charging resistor 7, the rectifying element 3, and gradually charges the capacitor C1.

Furthermore, when the sequence control in which the control circuit 8 detects changes in the voltage or current of the load 4 by applying a power supply voltage between C and D and operates after a certain period of time is completed, the contact 6 interlocked with the control circuit 8 closes. , the AC voltage is limited by the resistor C.

9. The anode of the bidirectional switching element 2 is connected to the gate (G) of the bidirectional switching element 2 through the anode A of the element. A2 becomes conductive, and the AC voltage between the power supply terminals A and B is directly applied to the load 4 including the rectifying element 3, resulting in normal operation.

That is, as shown in FIG. 4, since the capacitor C1 is charged via the charging resistor 7 after a while when the switch 1 is connected, no inrush current is generated during the time t, and the control circuit 8 operates and the contact 6 is closed. After time t1, the operation becomes normal.

As explained above, the sequence control by the control circuit prevents inrush current from occurring.

Therefore, there is no effect on electrical appliances connected to the common voltage, preventing destruction of the rectifying element, and extending the lifespan.
A highly reliable circuit can be obtained.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing a conventional AC-DC conversion circuit;
3 is a circuit diagram of an embodiment of the inrush current prevention circuit of the present invention, and FIG. 4 is an AC input waveform diagram of the circuit of the present invention. In the figure, 1: switch, 2959 bidirectional switching element, 3: rectifying element, 4: load, 6: contact, 7: charging resistor, 8: control circuit.

Claims (1)

[Scope of utility model registration request] One end A of the AC input terminal is connected to the anode A□' of the bidirectional switching element 5 and the gate G' via the power switch 1.
, as well as the anode A of the other bidirectional switching element 2
□, and also connects the anode A2' of the bidirectional switching element 5 to the gate of the bidirectional switching element 2 via the contact 6, and connects the anode of the bidirectional switching element 2 and the rectifying element 3 via the resistor 7. A control circuit 8 is connected to the input terminal of the load 4 and further closes the contact at a predetermined time depending on a change in the voltage or current of the DC load 4.
Inrush current prevention circuit connected to.