JPH07184369A - Power supply holding circuit - Google Patents

Abstract

PURPOSE:To provide a power supply holding circuit which can quickly cancel the self holding function without allowing that the charges charged in a charge accumulating means for stabilizing the power supply are supplied, at the time of cancelling the self holding function, to a switching means for cancelling the self holding function. CONSTITUTION:A transistor T3 (P type) is connected in parallel with a transistor T2 in the side of a battery 1 between the connecting points. The transistor T3 is provided with its emitter and base connected through a resistor 24, the emitter is connected to the emitter of transistor T2, while the base is connected to the collector of transistor T1 through a resistor 25 and a diode 26. Moreover, the collector of transistor T3 is connected to the resistors 23, 19.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply holding circuit that self-holds a voltage, and more particularly to a power supply holding circuit that can surely cancel the self-holding function when the power is cut off.

[0002]

2. Description of the Related Art Conventionally, a power supply holding circuit having a self-holding function as shown in FIG. 3 has been known. In FIG. 3, when the switch 2 is off, the transistor T1 (N
Shape) is off because the base is not powered. Transistor T2 whose emitter and base are connected
In the (P-type), power is supplied to its emitter through the diode 4, but since the transistor T1 connected to the base of the transistor T2 is off, there is not much potential difference between the emitter and the base of the transistor T2. As a result, it is off.

When the switch 2 is turned on, power is supplied from the battery 1 to the base of the transistor T1 and the transistor T1 is turned on. Then Transiter T2
The potential difference between the emitter and the base of the transistor (the voltage drop of the resistor 15) increases, and the transistor T2 also turns on. When the transistor T2 is turned on, power is supplied from the battery 1 to the constant voltage circuit 7, and the capacitor C1 for smoothing the power is charged.

Here, once the transistor T2 is turned on, a current path is formed from the battery 1 to the base of the transistor T1 through the diode 4 → transistor T2 → resistor 23 → diode 10, so that the transistor T1 is turned on. Hold the state. Therefore, even if the switch 2 is turned off, the transistors T1 and T2 continue to maintain the on state, and the power supply from the battery 1 to the constant voltage circuit 7 is self-maintained.

In such a state, in order to cancel the self-holding function, the transistor T4 is turned on by outputting a high level signal from the CPU 13 to the base of the transistor T4 (N type) via the resistor 22. . Then, the potential at the voltage dividing point e of the resistors 19 and 20 connected to one end of the bandpass capacitor C2 drops at once, so the potential at the other end of the capacitor C2 also drops at the same amount. As a result, the base power supply of the transistor T1 is lost, so that the transistor T1 is turned off and the self-holding function is released.

[0006]

However, in the above-mentioned conventional device, when the self-holding function is released, the capacitor C1 is charged even if the transistor T4 is turned on and the base potential of the transistor T1 is once lowered. Since the capacitor C2 is immediately charged with the electric charge via the resistor 23, the base potential of the transistor T1 may rise faster than the switching time of the transistor T1. Therefore, in such a case, there is a problem that the transistor T1 is not turned off and the self-holding function cannot be released. Further, in the past, the capacitor C1
Suppresses the influence of the electric charge charged in the
In order to turn off 1, the capacity of the capacitor C1 had to be reduced.

Therefore, the present invention has been made in view of the above problem, and when the self-holding function is released, the charge stored in the charge storage means for stabilizing the power supply is supplied to the switching means for releasing the self-holding function. It is an object of the present invention to provide a power supply holding circuit that can quickly release the self-holding function without the need.

[0008]

In order to achieve the above object, the present invention provides a load circuit that is supplied with power from a battery and a first operation that starts once the load circuit is connected to the battery.
A switching circuit; a second switching circuit provided between the battery and the load circuit, the second switching circuit communicating the power supply path from the battery to the load circuit only during the operation of the first switching circuit; By changing the operating voltage of the first switching means and the capacity storage means connected in parallel to the second switching means and smoothing the power supplied to the load circuit,
Fourth switching means for stopping the operation of the switching means, self-holding the power supply from the battery to the load circuit by starting the operation of the first switching means, and the self-holding by the operation of the fourth switching means. In the power supply holding circuit for releasing the above, one end thereof is connected between the battery and the second switching means, and the power supply path from the battery to the first switching means is communicated only during the operation of the first switching means. The power supply holding circuit is characterized by including a third switching means.

[0009]

With the above structure, in the present invention, when the first switching means operates, the second switching means operates,
Power is supplied from the battery to the load circuit via the second switching means, and the capacitance storage means is charged with electric charges. In addition, the third switching means operates and the third
Power is supplied from the battery to the first switching means via the switching means. As a result, self-holding is started.

Here, when the fourth switching means operates, the operating voltage of the first switching means changes to stop the first switching means, and accordingly, the second switching means also stops to transfer the battery to the load circuit. The power supply path is cut off and the self-holding function is released. At this time, since the path between the capacitance storage means and the third switching means is cut off by the second switching means, the electric charge charged in the capacitance storage means is passed through the third switching means to the first switching means. Will no longer be supplied to.

[0011]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is an electric circuit diagram showing the overall structure of this embodiment, in which the right side of the broken line is formed on a printed circuit board. The same parts as those in FIG. 3 are designated by the same reference numerals. As shown in FIG. 1, the feature of this embodiment is that the transistor T3 (P3) is provided between the connection point f and the connection point g.
Shape) is connected in parallel with the transistor T2 and to the battery 1 side.

The transistor T3 has its emitter and base connected via a resistor 24, the emitter connected to the emitter of the transistor T2, and the base connected to the resistor 2;
5, it is connected to the collector of the transistor T1 via the diode 26. The collector of the transistor T3 is connected to the resistors 23 and 19. Next, the operation of the present embodiment configured as described above will be described using the time charts (a) to (d) of FIG.

First, at time t1, when the switch 2 is turned on, power is supplied from the battery 1 to the base of the transistor T1 via the diode 8 and the resistor 14, the base potential c rises, and the transistor T1 is turned on. . Then, the potential difference between the emitter and the base of the transistor T2 (the voltage drop of the resistor 15) increases, and the transistor T2 is turned on. When the transistor T2 is turned on, power is supplied from the battery 1 to the constant voltage circuit 7, and the capacitor C1 for smoothing the power is charged. further,
Transistor T3 emitter-base potential difference (resistor 2
4) becomes large and the transistor T3 is also turned on. When the transistor T2 is turned on, a current path is formed from the battery 1 to the base of the transistor T1 through the diode 4 → transistor T3 → resistor 23 → diode 10.

Once the switch 2 is turned on, a current path is formed from the battery 1 to the base of the transistor T1, so that the transistor T1 maintains the on state. Therefore, even if the switch 2 is turned off, the transistor T
1, T2, T3 keep the ON state, and the constant voltage circuit 7
The power supply to is self-maintained. In this embodiment,
When the switch 2 is turned off at time t2, the CPU 1
3 recognizes that the switch 2 is off and releases the self-holding function. Specifically, the transistor T4 is turned on by outputting a high level signal from the CPU 13 to the base of the transistor T4 (N type) via the resistor 22.
Then, the potential at the voltage dividing point e of the resistors 19 and 20 connected to one end of the bypass capacitor C2 drops, so the potential c at the other end of the bypass capacitor C2 drops by the potential drop at the voltage dividing point e. Then, the base power supply of the transistor T1 disappears and the transistor T1 is turned off.
The potential difference between the emitter and the base of No. 3 becomes small, and the transistors T2 and T3 are turned off. Transistors T2 and T3
Is turned off, the electric charge charged in the capacitor C1 is not discharged to the capacitor C2, so that the base potential c of the transistor T1 does not rise immediately. Therefore, the transistor T1 can be surely turned off to cancel the self-holding function.

That is, in the conventional circuit of FIG.
As shown by the broken line in (c), when the transistor T4 is turned on to release the self-holding function at time t2, the electric charge charged in the capacitor C1 is immediately discharged to the capacitor C2. The potential c was rising immediately. On the other hand, in the present embodiment, as shown by the solid line in FIG. 2C, when the transistor T4 is on, the capacitor C1 and the capacitor C2 are reliably cut off by the transistor T2, so that the rise of the base potential c becomes gentle. The transistor T1 can be surely turned off.

Further, in this embodiment, since the rise of the base potential c becomes moderate, there is no need to reduce the capacity of the capacitor C1 and it is possible to set a completely stable capacity for smoothing the power supply. Furthermore, in the present embodiment, the self-holding function can be reliably released not only when the switch 2 is off, but also when the battery 1 is in an unstable state.

In this embodiment, the transistor T1 corresponds to the first switching means, and the transistor T1
2 corresponds to the second switching means, and the transistor T3
Corresponds to the third switching means, the transistor T4 corresponds to the fourth switching means, the constant voltage circuit 7 corresponds to the load circuit, and the capacitor C1 corresponds to the capacitance storage means.

[0018]

As described above, according to the present invention, the path from the capacitance storage means to the third switching means is cut off by the second switching means during the operation of the fourth switching means, so that during the operation of the fourth switching means. There is an excellent effect that the electric charge charged in the capacitance storage means is not supplied to the first switching means via the third switching means, and the self-holding function can be quickly released.

[Brief description of drawings]

FIG. 1 is an electric circuit diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a time chart for explaining the operation of FIG. 1, in which (a) shows ON / OFF of the switch 2, and (b).
Shows the on / off of the transistor T1, (c) shows the change of the base potential c, and (d) shows the on / off of the transistor T4.

FIG. 3 is an electric circuit diagram showing a configuration of a conventional technique of the present invention.

[Explanation of symbols]

 1 Battery 2 Switch 7 Constant Voltage Circuit T1, T2, T3, T4 Transistor C1 Capacitor

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical indication location H03K 17/60 17/73 9383-5J H03K 17/73 F

Claims (1)

[Claims] 1. A load circuit that is supplied with power from a battery, a first switching means that starts operation once connected to the battery, and a load circuit that is provided between the battery and the load circuit. A second switching means that communicates a power supply path from the battery to the load circuit only during operation of the switching means, and a power supply that is connected to the second switching means in parallel with the load circuit and is supplied to the load circuit. And a fourth switching means for stopping the operation of the first switching means by changing the operating voltage of the first switching means, the battery storing the battery when the operation of the first switching means is started. Self-holding the power supply to the load circuit from
In a power supply holding circuit that releases the self-holding by the operation of the fourth switching means, one end thereof is connected between the battery and the second switching means, and the battery is connected to the battery only during the operation of the first switching means. A power supply holding circuit comprising: a third switching means that communicates a power supply path to the first switching means.