JPS5924319A - Power supply circuit - Google Patents

Abstract

PURPOSE:To prevent a drop of the terminal voltage of a battery due to a large current which flows instantaneously to cause an unstable operation of an equipment, by connecting a current limiting circuit between a power supply terminal and a load circuit. CONSTITUTION:When the terminal voltage of a battery 1 is higher than the Zener voltage of a constant voltage diode 13 and voltage VBE of a transistor TR10, the base current of the TR10 flows through a resistance 12. Thus the collector and emitter of the TR10 become conductive, and a resistor 9 is short- circuited. Therefore a fluctuating load 4 is connected directly to the battery 1. While no Zener current flows when the terminal voltage of the battery 1 has a drop. Accordingly the base current to the TR10 does not flow and is converted to cut off state. Then the resistor 9 is set in series to the load 4 and limits the load current. This ensures a stable operation despite an abnormal level of the power supply voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power supply circuit for equipment operated by batteries, and its purpose is to prevent the terminal voltage of the battery from decreasing due to instantaneous large current flow.

FIG. 1 shows a conventional power supply circuit using a battery as a power source.

In Figure 1, 1 is a battery, and 2 is a stabilizing circuit that prevents voltage changes due to battery discharge from appearing on the output side.
In general, a series control stabilizing circuit is used which stabilizes the voltage at the lower limit of battery use and prevents the output voltage from changing with respect to input voltages higher than that. 3 is a constant load, for example, a load such as a class A amplifier circuit where the load current is approximately constant. Reference numeral 4 denotes a variable load, such as a class B amplifier circuit, whose load current fluctuates greatly.

In this type of circuit, the internal resistance of battery 1 increases when it becomes old after long-term use or when the ambient temperature is low.
When the variable load 4 instantaneously mutes a large current, the terminal voltage of the battery fluctuates greatly, and goes out of the control range of the stabilizing circuit 2, causing the voltage of the constant load 3 to also fluctuate, which has the drawback of making the circuit unstable. there were.

The present invention eliminates the above-mentioned drawbacks of the conventional technology, and one embodiment of the present invention will be described below with reference to FIG. 2.

1 is a battery, 2 is a stabilizing circuit, 3 is a constant load, and 4 is a variable load r, which are the same as the conventional example shown in FIG. 6 is a current limiting circuit, 6 is a switch, 7 is a voltage detection circuit, and 8 is a bypass capacitor.

Next, the operation of the above embodiment will be explained with reference to FIG. In the figure, when the terminal voltage of the battery 1 is sufficiently high, the switch 6 is turned on, and when the terminal voltage of the battery 1 becomes low due to fluctuations in the battery 1 and the variable load, this is detected by the voltage detection circuit 7.
is detected, the switch 6 turns OFF, and the current limiting circuit 5
is connected between the current 1 and the variable load 4 to limit the load current.

Such an operation can prevent the terminal voltage of the battery 1 from decreasing and stabilize the operation of the constant load 3.

Furthermore, another specific embodiment will be described with reference to FIG. 3. 1 is a battery, 2 is a stabilizing circuit, 3 is a constant load, and 4 is a variable load, which are the same as the embodiment shown in FIG.

9 is a resistor, which corresponds to the current limiting circuit 5 in FIG. 1
o is a transistor, which corresponds to the switch 6 in FIG.

11 and 12 are resistors, and 13 is a constant voltage diode (Zener diode).

Next, the operation of the above embodiment will be explained with reference to FIG. When the terminal voltage of the battery 1 is higher than the Zener voltage of the voltage regulator diode 13 and ■BE of the transistor 10, the resistor 12
- The base current of the transistor 10 flows, the collector and emitter become conductive, and the resistor 9 is short-circuited. Therefore, the variable load 4 is directly connected to the battery 1.

On the other hand, when the terminal voltage of the battery 1 decreases, the Zener current stops flowing, so that the transistor 10fd is cut off, with no current flowing through the transistor 1, and the resistor 9 is connected in series with the variable load 4 to limit the load current. Therefore, stable operation can be obtained even if the power supply voltage reaches an abnormal level.

As described above, the present invention has the advantage that it is possible to prevent unstable operation of a device with a simple circuit configuration against an abnormal drop in the power supply voltage of the device due to battery operation with a variable load.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional power supply circuit, FIG. 2 is a block diagram of a power supply circuit according to an embodiment of the present invention, and FIG. 3 is a wiring diagram of the embodiment showing a specific configuration. 1...Battery, 6...Current limiting circuit, 6
...Switch, 7...Voltage detection circuit.

Claims (1)

[Claims] A current limiting circuit is connected between a power supply terminal and a load circuit, and is connected in parallel to the current limiting circuit, and when the voltage of the power supply terminal reaches a predetermined level, the input and output of the current limiting circuit are short-circuited. A power supply circuit characterized by being provided with a switch means.