JPS58208818A - Ac voltage controlling circuit - Google Patents

Abstract

PURPOSE:To simplify the control of AC voltage, by setting an npn TR and a pnp TR in parallel to each other to obtain an emitter follower and controlling the voltage of a bias impedance terminal connected between the emitter and the base of both TRs and in series to a load. CONSTITUTION:A variable resistance 2 for setting bias voltage a resistance 3 for dividing voltage are connected 6 in series to an AC power supply 1. The bases of an npn TR4 and a pnp TR5 are connected in common to a joint 6. The collector side is connected to an end of the supply 1 via adverse voltage preventing diodes 7 and 8; while the emitter side is connected to the other end of the supply 1 via a load L and in the form of an emitter follower. The resistance 2 is controlled to control the voltage which is applied to the bases of TRs4 and 5. Then flowing currents I1 and I2 of the TRs 4 and 5 are controlled. Thus it is possible to form a control circuit containing no higher harmonic component with simple constitution.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an alternating current voltage control circuit, and particularly relates to an alternating current voltage control circuit in which two
The present invention relates to a current-changing voltage control circuit that controls a load voltage by connecting several transistors.

Conventionally, when controlling the AC voltage of a load, simple control was performed by connecting a slide transformer or slide resistor in series with the load, but these transformers and resistors had bulky external shapes and mechanical problems. Because of this, it was difficult to make it smaller and lighter, and there were certain limits to reducing costs.

In addition, various circuits have been devised and put into practical use that control load power by connecting elements such as thyristors and triacs in series to a load. These circuits control the conduction angle by switching, so they have little loss and can control loads from small to large loads. However, on the other hand, the output voltage contains a considerable amount of harmonic components, so they are susceptible to the effects of harmonics. This method has the disadvantage that it cannot be applied to circuits in which noise and noise are a problem.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned disadvantages of conventional control surfaces and to provide an AC voltage control circuit that has a simple circuit configuration and is inexpensive.

In order to achieve the above object, an AC voltage control circuit according to the present invention has two transistors of an npn type and a pnp type connected in parallel as emitter followers, and a bias voltage connected in series with a load between the emitters and bases of both transistors. It is characterized by being configured so that the voltage between the terminals of the impedance element can be adjusted.

An embodiment of the AC voltage control circuit according to the present invention will be described below with reference to the drawings.

In FIG. 1, an AC power supply 1 is connected in series with a variable resistor 2 for setting a bias voltage and a resistor 3 for voltage division.

The NPN type transistor 4 and the PNP type transistor 5 are commonly connected to the midpoint 6 of the variable resistor 2 and the resistor 3, and the collectors of these transistors 4 and 5 are respectively connected to prevent reverse voltage. It is connected to one end of the AC power supply 1 via a diode 7.8. transistor 4,
The emitters of 5 are commonly connected, and this connection point and the AC power supply 1
A load 9 is connected between the other ends.

FIG. 2 illustrates the operating waveforms of each part in the AC voltage control circuit shown in FIG. A voltage v2 is generated between them.

This voltage v2 serves as a bias for the emitter follower-connected transistors 4 and 5, and a voltage (3) approximately equivalent to the voltage (2) is generated in the load 9.

Transistors 4 and 5 are conductive only when they are forward biased, allowing currents □ and ▪ to flow. Therefore, a load current (1+) corresponding to the bias voltage (2) flows through the load 9 every half-wave when the transistors 4 and 5 conduct.

Since the alternating current (x + z) flowing through the load 9 changes depending on the bias voltage V generated by the resistor 3, any load current can be obtained by adjusting the variable resistor 2.

In addition, in the above explanation, the variable resistor 2 is used as the impedance element for setting the bias voltage, and the fixed resistor 3 is used as the impedance element for voltage division. Both may be replaced, or an impedance element other than a resistor may be substituted.

As described above, the present invention is applicable to npn type and pn type as described above.
Two np type transistors are connected in parallel as emitter followers, and the load current is controlled by adjusting the voltage between the terminals of a voltage dividing impedance element connected in series with the load between the emitters and bases of both transistors. Since the circuit structure is simple and can be manufactured at low cost, it is possible to obtain an output waveform that is almost the same as the input waveform.

In addition, since the operation of both transistors is not a switching operation, no harmonic components are generated, and there is no need to consider noise resistance or noise. It can be widely applied to various circuits that require power adjustment.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the AC voltage control circuit of the present invention, and FIG. 2 is an operating waveform diagram thereof. 1... AC power supply, 2... Variable resistor for bias voltage setting, 3... Resistor for voltage division, 6... Midpoint,
9...Load.

Claims (1)

[Scope of Claims] C1) Two transistors of an npn type and a pnp type are connected in parallel as emitter followers, and the voltage between the terminals of a bias impedance element connected in series with a load between the emitters and bases of both transistors is adjusted. An alternating current voltage control circuit characterized in that it is configured to (2) At the midpoint of the bias voltage setting impedance element and the voltage dividing impedance element connected in series to the AC power supply,
The bases of the npn transistor and the pnpn upper type transistor are commonly connected, the collectors of these transistors are each connected to one terminal of the AC power supply via a reverse voltage prevention diode, and the emitters of both transistors are commonly connected. and a load is connected between it and the other terminal of the power source.