JPH02303315A - High-speed return circuit for power source circuit provided with shutdown type protective circuit - Google Patents

Abstract

PURPOSE:To make it return to high-speed after a protective circuit has operated by quickly discharging the charge, which was accumulated in a main capacitor, after turning off a power switch. CONSTITUTION:Currents are rectified, and are supplied to a power transformer after being switched into AC by a switching control block provided with shutdown type overcurrent protective circuit. In case that the shutdown type overcurrent protective circuit operates or a power switch 10 is cut, the output of winding 2 vanishes, and the rectification output vanishes, so a transistor 4 becomes off and a transistor 6 becomes on, whereby the charge of a main capacitor 1 is discharged through resistances 7 and 8. Therefore, the operation of the overcurrent protective circuit stops, and next when the power switch 10 is turned on, it starts up speedily.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a power supply circuit for a shutdown type protection circuit 11, in which the power supply circuit from the time when the power switch is turned off to the time when the power switch is restored after the shutdown circuit is activated. This invention relates to a high-speed recovery circuit that shortens the time.

[Conventional technology]

A general switching ta circuit is shown in Figure 2,
A protection circuit is provided to prevent the switching element from being destroyed when an excessive Ti current flows or an overvoltage is applied to the switching element. This protection circuit includes a shunt-down type that maintains a disabled state while the power switch is turned on to prevent output power from being output in the event of overcurrent or overvoltage, and When this happens, there is a limiter type that suppresses the current or voltage to a set value.

Depending on how the setting values are determined, the liminter type may not destroy the switching element, but it may continue to maintain a poor condition, so if you are concerned about safety, a shutdown type protection circuit is recommended. is good.

[Problem to be solved by the invention]

However, the disadvantage of a shutdown type protection circuit is that even if the power switch is turned off after the protection circuit operates, the protection circuit continues to operate as long as power is supplied by the main capacitor. , during that time, the power output cannot be turned on even if the power switch is turned on.

SUMMARY OF THE INVENTION An object of the present invention is to provide a power supply circuit that can quickly restore the IT power supply circuit operation by quickly discharging the charge stored in the main capacitor when the power switch is turned off.

[Means to solve the problem]

In order to solve the above problems, in this invention, when the protection circuit of the power supply circuit is activated and the power switch is turned off, the primary winding of the power transformer senses that the power output is no longer output. The circuit has a circuit configuration in which two transistors that connect a discharge resistor in parallel with the main capacitor operate as an on/off switch.

However, in order to prevent this circuit from operating when the puff switch is turned on, a capacitor is used to
The system is designed to prevent trouble during start-up, and allows for quick recovery after the power supply protection circuit is activated.

[Effect]

Is it configured as above? 1tfi circuit is Sha7)・
Even after the down-type protection circuit operates, the charge stored in the main capacitor is quickly discharged, so even if the power switch is turned on immediately after the power switch is turned off, the output of the power supply circuit will still rise. It becomes like this.

〔Example〕

An embodiment of the present invention will be described below based on FIG.
The main capacitor l shown in the drawing is the main capacitor of a power supply with a shutdown type overcurrent protection circuit. 2 is a primary winding of a power transformer that senses whether power is on or off, and a diode 3 is provided to rectify the output of the secondary winding.

Further, a transistor 4 is connected which receives the output of the diode 3 and performs a switching operation, and a resistor 5 which sets a bias so that the VCt of the transistor 4 has an appropriate value is connected to the collector of the transistor 4.

A transistor 6 that operates in an opposite phase to the transistor 4 is connected to the collector side of the transistor 4. The emitter of the transistor 6 has the opposite phase to the transistor 4, and the emitter of the transistor 6
A resistor 7 is connected to set the bias so that the VCf of VCf becomes an appropriate value. Furthermore, transistor 6
A discharge resistor 8 for discharging the charge stored in the main capacitor l is connected to the collector of the main capacitor l. By configuring the circuit like this, a shutdown type overcurrent protection circuit can operate, and the power switch I
The circuit operates when O is turned off. here,
Since there is a possibility that it will operate even when the power switch 10 is turned on, there is a structure in the base of the transistor so that when the power switch 10 is turned on, the transistor 6 will not be turned on until the output of the negative winding 2 rises. , the capacitor 9 is inserted.

〔Effect of the invention〕

As explained above, this invention provides a simple circuit that quickly discharges the charge stored in the main capacitor in a power supply circuit with a built-in zero-down type protection circuit when the power switch is turned off. This addition has the effect of quickly recovering after the protection circuit operates.

[Brief Description of the Drawings] Fig. 1 is a circuit diagram showing an embodiment of a 74H that incorporates the high-speed recovery circuit of the present invention, and Fig. 2 is a circuit diagram showing a conventional example of a power supply with a built-in shutdown type protection circuit. It is a diagram. 1... Main, Capacitor 2... Winding for power on/off detection 3... Winding 2 Diode for output voltage rectification 4... Transistor 5... Bias setting resistor for transistor 4 6. ...Transistor 7...Operation mode setting resistor 8 of transistor 6...
Main capacitor discharge TL resistor 9... Capacitor IO... Power switch and above Applicant Seiko Electronics Co., Ltd. Agent Patent attorney Takayuki Hayashi Mokobe

Claims (3)

[Claims] (1) In a power supply circuit with a built-in shutdown type overcurrent protection circuit, in order to prevent the switching element from being destroyed due to excessive current flowing through the switching element, when the power supply circuit is turned off, A high-speed recovery circuit for power supply circuits with a shutdown type protection circuit that discharges the main capacitor in a short period of time. (2) A high-speed recovery circuit for a power supply circuit with a shutdown type protection circuit according to claim 1, wherein the protection circuit is operated only by the charge accumulated in the main capacitor of the power supply circuit. . (3) For a power supply circuit with a shutdown type protection circuit according to claim 1, wherein on/off of the power supply circuit is determined based on the winding output of the primary side of a power transformer of the power supply circuit. Fast return circuit.