JPH0559441B2 - - Google Patents

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.Generally, the voltage is stabilized at the lowest voltage limit for battery use, and when the input voltage is higher than that, it is stabilized. On the other hand, a series control stabilization circuit is used to prevent the output voltage from changing. 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 the battery 1 increases when it becomes old after long-term use or when the ambient temperature is low, and when the variable load 4 instantaneously consumes a large current, the terminal voltage of the battery fluctuates greatly. , the voltage of the constant load 3 also fluctuates outside the control range of the stabilizing circuit 2, which has the disadvantage of making the circuit unstable.

The present invention eliminates the above-mentioned conventional drawbacks,
The basic configuration of the present invention will be explained 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, which are the same as the conventional example shown in FIG. 5 is a current limiting circuit, 6 is a switch, 7 is a voltage detection circuit, and 8 is a bypass capacitor.

Next, we will discuss the operation of the basic configuration of the present invention in the second section.
This will be explained with figures. In the figure, when the terminal voltage of battery 1 is sufficiently high, switch 6 is turned on, and when the terminal voltage of battery 1 becomes low due to fluctuations in battery 1 and the variable load, this is detected by voltage detection circuit 7 and switch 6 is turned on. is turned OFF, and the current limit 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, an embodiment of the present invention will be described with reference to FIG. 1 is a battery, 2 is a stabilizing circuit, 3 is a constant load, 4 is a variable load, and these are the second
This is the same basic configuration of the present invention as shown in the figure. 9
is a resistor, which corresponds to the current limiting circuit 5 in FIG. 10 is a transistor, which is the switch 6 in FIG.
corresponds to 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 constant voltage diode 13 and the V _BE of the transistor 10, the base current of the transistor 10 flows through the resistor 12, 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 battery 1 decreases, Zener current no longer flows, and therefore transistor 1
The base current of 0 also does not flow and the transistor 10 is in a cut-off state, and the resistor 9 is connected in series with the variable load 4 to limit the load current. Therefore, even if the power supply voltage reaches an abnormal level, stable operation can be obtained by temporarily limiting the current supplied to the variable load 4. Then, as soon as the terminal voltage of the battery 1 is restored, the above-mentioned restriction is canceled, so there is an effect that self-recovery can be achieved in a short time.

As explained above, according to the present invention, a simple circuit configuration in which the transistor for detecting the power supply voltage and the transistor for controlling the load current are the same transistor is used to power a battery-operated device having a variable load. This has the advantage of preventing unstable operation of equipment due to abnormal voltage drops.

[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 showing the basic configuration of the present invention, and FIG. 3 is a wiring diagram of an embodiment showing the configuration of the present invention. 1... Battery, 5... Current limiting circuit, 6... Switch, 7... Voltage detection circuit.

Claims (1)

[Claims] 1. a power supply terminal, a load circuit, a current limiting circuit connected between the terminal and the load circuit,
This current limiting circuit has a collector at one end, an emitter at the other end, a transistor connected from the above terminal to the base through a first resistor, and a constant voltage connected from the base of this transistor through a second resistor. A power supply circuit consisting of a diode.