JPS60121924A - Rush current preventng circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

TECHNICAL FIELD The present invention relates to a power supply device having a smoothing capacitor on the input side, and more particularly to an inrush current prevention circuit for reducing inrush current flowing through the capacitor when a switch is turned on.

BACKGROUND OF THE INVENTION In general, in the power supply device described above, a large rush current flows through the capacitor when the switch is turned on. If this inrush current is particularly large and the capacity of the primary power supply that supplies power to the power supply is low, the voltage of the main power supply will drop when the switch is turned on, and it will take time for the power supply to operate normally. .

In the worst case, the -high power supply voltage may not return to normal, and the power supply may not operate normally.

In order to reduce this rush current, a rush current prevention circuit is provided in the power supply device. FIG. 1 is a circuit diagram of a power supply device having this inrush current prevention circuit, in which a resistor 9, a thyristor 12, and a power transformer 8 (N1
．． N is a thyristor drive circuit (winding N3 of power transformer 8) that uses the output of the primary winding and secondary winding, respectively.
An inrush current prevention circuit consisting of a diode and a 10° capacitor 11) is provided in front of the input capacitors 8 and 4. Immediately after the switch 2 is turned on, the current flowing from the -order power supply 1 to the input capacitors 8 and 4 is limited by the resistor 9. After the input capacitors 8 and 4 are sufficiently charged, the thyristor 12 is driven, and the current flowing through the resistor 9 is bypassed by the thyristor 12, thereby reducing the rush current.

However, in this conventional inrush current prevention circuit, the power transformer 8 for voltage conversion is provided with the auxiliary winding N3, which increases the cost of the power transformer 8. Furthermore, since the thyristor 12 is used as an element to bypass the current flowing through the resistor 9, the loss generated by the resistor 9 is small, but the loss constantly generated in the thyristor 12 is a value that cannot be ignored as a power supply device. Ta.

In Fig. 1, 5 is a choke coil, 6 is a power supply, a transformer 8 is a resistor, and 7 is an object of the invention.Therefore, an object of the present invention is to provide an inexpensive motor with low loss due to the current flowing through the input capacitor. An object of the present invention is to provide an inrush current prevention circuit.

Structure of the Invention The inrush current prevention circuit of the present invention includes a resistor and a relay contact connected in parallel between one end of a smoothing capacitor and one end of an input side, and a contact part of a relay connected to the input side of the resistor,
It has a time constant circuit consisting of a resistor and a capacitor, a transistor connected to the connection point between the resistor and the capacitor of this time constant circuit, and a transistor connected to the fill part of the collector relay. After the specified time has elapsed, the voltage across the capacitor of the time constant circuit operates the transistor, which applies voltage to the coil of the relay and closes the contact of the relay. The current flowing through the resistor is bypassed to the relay contact, reducing the loss that constantly occurs due to this resistor.

Example The present invention will be described below with reference to drawings of embodiments.

FIG. 2 is a block diagram of a power supply device having an inrush current prevention circuit according to an embodiment of the present invention.

In this embodiment, in the conventional circuit shown in FIG.
1. Eliminate the thyristor 12 and install a current limiting resistor 9 and relay contact section 18 between one end of the capacitor 8 and one end of the input.
2 are connected in parallel, and a time constant circuit consisting of a resistor 14 and a capacitor 15 is connected to the input side of the resistor 9, and the base is connected to the connection point of the resistor 14 and capacitor 15 of this time constant circuit, and biased by the capacitor 15. A transistor 16 is provided, the collector of which is connected to the coil portion 181 of the relay to operate the relay.

Next, the operation of this circuit will be explained. When switch 2 is turned on, the charge m1 is limited to capacitor 8°4 through resistor 9! The flow flows. At this time, since no voltage is generated in the capacitor 15, the transistor 16 does not operate.
Therefore, the coil part 181 of the relay, the contact part 1 of the relay
82 doesn't work either. Then, when the time set by the time constant circuit has elapsed, the voltage across the capacitor 15 turns on the transistor 16, and the coil section 181 of the relay
A voltage is applied to the relay, and the contact portion 182 of the relay is closed. As a result, the current flowing through the resistor 9 bypasses toward the contact portion 182 of the relay.

The values of the resistor 14 and capacitor 15 of the time constant circuit are set so that the coil section 181 of the relay operates after the 11t% current flowing into the capacitor 8.4 is sufficiently reduced. As described above, the inrush current prevention circuit of the present invention has a simple configuration and is therefore inexpensive, and since a relay contact is used instead of a conventional thyristor, there is little loss due to current flowing through the input capacitor.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a power supply device having a conventional inrush current prevention circuit, and FIG. 2 is a circuit diagram of a power supply device having a rush current prevention circuit according to an embodiment of the present invention. 1 Primary power supply, 2: Switch, 8.4: Capacitor, 5: Choke coil, 6: Switching transistor, 7: Drive circuit S 8: Power transformer, 9: Resistor, 1
81: Relay coil section, 182: Relay contact section, 1
4: resistor, 15: capacitor, 16:) transistor. Patent applicant: NEC Corporation Figure 1 Figure 2

Claims (1)

[Claims] In a power supply device having a smoothing capacitor on the input side, a resistor and a relay contact part are connected in parallel between one end of the capacitor and one end of the input side, and a resistor and a relay are connected to the input side of the resistor. A time constant circuit consisting of a capacitor, the base is connected to the connection point of the resistor and the capacitor of this time constant @ path, and the collector is connected to the coil part of the relay, and after the switch is turned on, the time set by the time constant circuit is connected. After , the time constant circuit is activated by the voltage across the capacitor, which applies voltage to the coil of the relay, closes the contact of the relay, and causes the current to flow through the resistor in parallel with the contact of the relay. An inrush current prevention circuit comprising a bypass sacell transistor toward a contact part of a relay.