JP2691988B2 - DC stabilization power supply non-startup countermeasure circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a non-startup countermeasure circuit for a DC stabilized power supply, and more specifically, a non-startup in a state where a reverse voltage is applied to the output side of the DC stabilized power supply. It is about circuits.

(Prior Art) FIG. 7 shows a circuit example (transistor series regulator) of a conventional DC stabilized power supply. In FIG. 7, the block 1 surrounded by the alternate long and short dash line is a stabilized DC power supply, and are input terminals to which a DC voltage in a rough smoothed state is applied, and are output terminals from which a stabilized DC voltage is output. is there. Q is a control transistor which is connected in series between the input terminal and the output terminal and keeps the output voltage constant by changing the degree of conduction, and its base is an integrated circuit that constitutes an error amplifier. The output terminal of the IC is connected. A voltage obtained by dividing the output voltage of the stabilized DC power supply 1 by the resistors R ₃ and R ₄ is input to the integrated circuit IC. on the other hand,
A block 2 surrounded by a broken line is a fold-down type overcurrent protection circuit for protecting the control transistor Q against an overload or a short circuit on the load side.

As a normal output voltage stabilizing operation, in the integrated circuit IC, the error between the midpoint voltage of the resistors R ₃ and R ₄ and the internal reference voltage is calculated by the amplifier A, and the output voltage of the amplifier A is controlled. The base of the transistor Q _A for Darlington connection with the transistor Q for driving is driven, and the output voltage is maintained at a predetermined value by the feedback control.

On the other hand, as the operation of the fold-back type overcurrent protection circuit 2, the difference between the voltage across the resistor R _{S and} the voltage across the resistor R ₁ is applied between the base and emitter of the transistor Q _B. output There conduction limits of the transistor Q base-emitter transistor from the time it reaches the rising voltage Q _B is the transistor Q _a starting conduction _B is started, a decrease in the DC stabilized power supply 1 output current as the load becomes heavier As a result, the voltage drops and the circuit element is effectively prevented from being damaged by the overcurrent.

(Problems to be Solved by the Invention) Although the conventional DC stabilized power supply is configured and operates as described above, the output terminal,
In a state in which the reverse voltage E _R is applied to (these states often occur), there is a drawback that the output voltage may not rise because the output cannot rise. That is, due to the structure of the integrated circuit IC, the transistor Q _B has the eighth
As shown in FIG. 9 and FIG. 9, the parasitic transistors Q _K are equivalently connected, and no inconvenience occurs during normal use, but when the reverse voltage E _R is applied, the transistors Q _B , Q _K The thyristor having the PNPN structure constituted by turns on, and the base and emitter of the transistors Q _A and Q are kept short-circuited, so that the startup cannot be performed. That is, in FIG. 7 and FIG. 9, the thyristor constituted by the transistors Q _B and Q _K is turned on when a positive signal is given to the base of the transistor Q _B from the positive electrode of the reverse voltage E _R via the resistor R _2. The reverse voltage E _R of the positive electrode →
The main current flows in the negative electrode path of the emitter → reverse voltage E _R of the integrated circuit IC of the constant voltage diode Z → amplifier emitter → transistor Q input terminal → the transistor Q _K one of A _B, the application of a reverse voltage E _R The thyristor remains on as long as it continues. Therefore, a DC voltage is applied to the input terminal, and the integrated circuit IC
Even after the operation started, the transistors Q _A and Q could not be driven.

(Means for Solving Problems) The present invention has been proposed in view of the above points, and an object of the present invention is to make it easy even when a reverse voltage is applied to the output side of a DC stabilized power supply. Another object of the present invention is to provide a non-startup countermeasure circuit for a stabilized DC power supply capable of starting up.

In order to achieve the above object, the present invention is applied to a DC regulated power supply having a fold-back type overcurrent protection circuit, which is connected in series with an input terminal of an error amplifier of the fold-down type overcurrent protection circuit. A non-startup countermeasure circuit for a stabilized DC power supply, which is characterized in that it is provided with switch means that is connected to the switch and is turned on only when an input voltage is applied.

(Function) In the non-startup countermeasure circuit for the DC stabilized power supply of the present invention, the input terminal of the error amplifier of the fold-back type overcurrent protection circuit is stabilized by the switch means that is turned on only when the input voltage is applied. Since the power supply is disconnected when the power supply is not operating, the thyristor in the error amplifier does not turn on even in a usage state in which a reverse voltage is applied to the output terminal, and startup can be easily performed. It is a thing.

Hereinafter, the present invention will be described in detail with reference to the drawings showing examples.

FIG. 1 is a basic circuit configuration diagram showing an embodiment of a non-startup countermeasure circuit for a stabilized DC power supply of the present invention. In FIG. 1, reference numeral 3 denotes a non-startup countermeasure circuit, which has a transistor Q _OP as switch means connected in series with the input terminal of the error amplifier U1 of the fold-back type overcurrent protection circuit. _A drive signal is applied to the base of _OP via diode D _OP from the midpoint of resistor R _OP and capacitor C _OP connected in series between the input terminal of the stabilized DC power supply and circuit ground, and the input voltage is applied. It is supposed to turn on only at times.

FIG. 2 is a circuit configuration diagram of a stabilized DC power supply to which the non-startup countermeasure circuit of FIG. 1 is applied, and is the same as the conventional DC stabilized power supply described in FIG. 7 except for the non-startup countermeasure circuit 3. The parasitic transistor Q _K in the integrated circuit IC is shown for clarity.

Then, in the non-operating state in which the DC voltage E is not applied to the input terminal, when the reverse voltage E _R is applied between the output terminals, the thyristor by the transistors Q _B and Q _K in the integrated circuit IC is used. Can be turned on, but
Since the transistor Q _OP of the non-startup countermeasure circuit 3 is off, the main current (reverse current) path of the thyristor is cut off and will not be turned on.

Therefore, when the DC voltage E is applied to the input terminal in this state, the integrated circuit IC is supplied with power and is in an operating state, and drives the control transistor Q via the transistor Q _A to operate the DC stabilized power supply. Output rises. On the other hand, the capacitor C _OP is charged through the resistor R _OP with a time constant of T = R _OP × C _OP , and the voltage turns on the transistor Q _OP through the diode D _OP, and the transistor Q _B in the integrated circuit IC.
The emitter of is connected to one end of the resistor R _S , but at this point the output voltage of the stabilized DC power supply has risen sufficiently and the reverse voltage E _R has disappeared, so the fold-back type overcurrent protection circuit It can be operated normally.

As described above, in the non-startup countermeasure circuit of the present invention, the reverse voltage is applied to the output terminal without affecting the original electric characteristics of the stabilized DC power supply or the operation of the fold-back type overcurrent protection circuit. It is possible to completely prevent the inactivation in the state. It goes without saying that the error amplifier can be applied not only to an integrated circuit, but also to an error amplifier composed of discrete components.

3 to 6 are circuit configuration diagrams showing another embodiment of the non-startup countermeasure circuit. FIG. 3 shows the circuit of FIG. 1 with the time constant circuit omitted (capacitor C _OP omitted), Fourth
The figure shows a circuit in which a resistor R _BE is connected between the base and emitter of the transistor Q _{OP in} the circuit of FIG. 1 to turn off the transistor Q _OP deeper. FIG. 5 shows the time constant circuit from the circuit of FIG. Is omitted (capacitor C _OP is omitted), and FIG. 6 shows a circuit configuration for the negative power supply. Also,
In FIG. 6, the capacitor C _OM may be omitted, or the resistor R _BE may be connected between the base and emitter of the transistor Q _OM .

(Effects of the Invention) As described above, the present invention is applied to a DC stabilized power supply having a fold-back type overcurrent protection circuit, and is applied to an error amplifier of the fold-down type overcurrent protection circuit. Since the switch means that is connected in series with the input terminal and turns on only when an input voltage is applied is provided, the input terminal of the error amplifier of the fold-back type overcurrent protection circuit is disconnected when the DC stabilized power supply is not operating. Since the thyristor in the error amplifier does not turn on even in a usage state in which a reverse voltage is applied to the output terminal, there is an effect that the activation can be easily performed.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment of a non-startup countermeasure circuit for a DC stabilized power supply according to the present invention, and FIG. 2 is a circuit configuration diagram of a DC stabilized power supply to which the non-startup countermeasure circuit in FIG. 1 is applied. 3 to 6 are circuit configuration diagrams showing other embodiments of the non-startup countermeasure circuit, FIG. 7 is a circuit configuration diagram of a conventional DC stabilized power supply, and FIGS. 8 and 9 are error amplifiers. It is explanatory drawing of the parasitic transistor formed in the integrated circuit which comprises. 1 ... DC stabilized power supply, 2 ... F-shaped drooping type overcurrent protection circuit, 3 ... Non-startup countermeasure circuit, Q ... Control transistor, U1 ... Error amplifier, Q _OP ... Transistor, D _OP ......
Diode, R _OP ...... Resistance, C _OP ...... Capacitor

Claims (1)

(57) [Claims] 1. An input voltage applied to a stabilized direct current power supply having a fold-back type overcurrent protection circuit and connected in series with an input terminal of an error amplifier of the fold-down type overcurrent protection circuit. A non-startup countermeasure circuit for a stabilized DC power supply, characterized in that it comprises switch means that is turned on only when a voltage is applied.