JPS6024722A - Switching circuit - Google Patents

Abstract

PURPOSE:To prevent a power source ripple from flowing into a circuit to be controlled and give the current from a power source to the circuit to be controlled through a resistance by providing said resistance which sets an LED to reverse bias by a stabilized power source when the LED is extinguished. CONSTITUTION:When a positive voltage is applied to the base of a switching transistor (SW TR) 1, this SW TR 1 is turned on, and an LED 2 is lit, and a circuit 3 to be controlled is set to a low potential through a resistance 6. At this time, though a slight current is flowed to a resistance 6' because it is constituted with a high resistance, it has not an influence upon the circuit. When no signals are applied to the base of the SW TR 1, the LED 2 is extinguished. At this time, the LED 2 is set to reverse bias by the resistance 6' connected to the stabilized power source. Since the circuit 3 to be controlled is set to a high potential through resistances 6' and 6 by the stabilized power source, a current is not flowed to the circuit 3 to be controlled from a non-stabilized power souce of much power source ripple.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a switching circuit that improves the effects of ripple from a power supply.

Conventional configuration and its problems When attempting to simultaneously control other controlled circuits in synchronization with the lighting of a light emitting diode (hereinafter abbreviated as LED), the switching circuit shown in Fig. 1 has conventionally been generally used. It was getting worse. In FIG. 1, 1 is a switching transistor, 2 is an LED, 3 is a controlled circuit, and 4 is a resistor for determining the current of the LED 2, which is connected to an unregulated power source. 5
is a resistor that controls the controlled circuit 3.

The operation of the switching circuit configured as described above will be described below.

First, the switching transistor 1 turns on when + voltage is applied to its base, and the LED 2 connected to the collector lights up. At this time, since the collector is at a low potential, the controlled circuit 3 is set to a low potential via the resistors.
Become active (or inactive). LED here
2 is a current determined by a resistor 4, and its brightness is determined.

On the other hand, when no input is applied to the base of the switching transistor 1, the switching transistor 1 is turned off, the LED 2 is turned off, and the suppressed circuit 3 is connected to the unregulated power supply via the resistor 4, the LED 2, and the resistor 5. It is set to a high potential and becomes inactive (or active).

However, in the above configuration, the controlled circuit 3 is controlled by an unregulated power supply, and hum is likely to occur due to the influence of power supply ripple.

In order to improve the generation of hum, it is possible to connect resistor 4 to a stabilized power supply, but in order to make LED 2 emit light with sufficient brightness, it is necessary to flow a large current. It is uneconomical as it requires a large size.

Purpose of the Invention The present invention solves the above-mentioned problems of the conventional technology, suppresses the generation of hum, and eliminates the burden on the stabilized power supply.
It is an object of the present invention to provide a switching circuit that controls a controlled circuit in synchronization with the lighting of the lamp.

Structure of the Invention The present invention is configured so that the controlled circuit can be controlled in synchronization with the blinking of the LED, and a resistor is provided to reverse bias the LED using a stabilized power supply when the LED is off, thereby reducing power supply ripple. By preventing current from flowing into the controlled circuit and supplying current from the stabilized power supply to the controlled circuit via the resistor, the generation of hum is suppressed.

DESCRIPTION OF THE EMBODIMENTS FIG. 2 is a circuit diagram of a switching circuit in one embodiment of the present invention. In Figure 2, 1 is a switching transistor, 2 is an LED, 3 is a controlled circuit, and 4 is an LED 2.
6 is a resistor for controlling the controlled circuit 3, which has the same configuration as the conventional example and is given the same number. 6 is a resistor that controls the LED 2 when the switching transistor 1 is off. This is the resistance set for bias.

The operation of the switching circuit of this embodiment configured as described above will be described below.

First, when a positive voltage is applied to the base of the switching transistor 1, the switching transistor 1 is turned on, the LED 2 lights up, and the controlled circuit 3 is set to a low potential via the resistor 5. This operation is the same as the configuration of the conventional example.

At this time, since the resistor 6 is made of high resistance, a small amount of current flows, but this has no effect on the circuit.

Next, when no signal is applied to the base of the switching transistor 1, the LED 2 is turned off. At this time, the LED 2 is set to reverse bias by the resistor 6 connected to the stabilized power supply. Further, since the controlled circuit 3 is set to a higher potential than the stabilized power supply via the resistors 6 and 5, no current flows to the controlled circuit 3 from the unregulated power supply with a large power supply ripple.

Effects of the Invention As described above, according to the present invention, since the LED is set to reverse bias when the switching transistor is off, the LED can be turned on without putting a burden on the stabilized power supply and without causing hum. Synchronous switching circuits can be constructed economically.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a conventional switching circuit, and FIG. 2 is a circuit diagram of a switching circuit according to an embodiment of the present invention. 1...Switching transistor, 2...
... Light emitting diode (LED), 3 ... Controlled circuit, 4 to 6 ... Resistor.

Claims (1)

[Claims] It comprises a switching transistor and a light emitting diode connected to the switching transistor and driven by an unregulated power supply, and the light emitting diode is turned on and off by turning on and off the switching transistor, and in synchronization with this, other controlled objects are turned on and off. a resistor configured to control the circuit, set the light emitting diode in reverse bias by a regulated power supply when the light emitting diode is turned off, and supply current from the regulated power supply to the controlled circuit; A switching circuit characterized by being provided with.