JPS6216054B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a triac drive circuit.

Triacs (bidirectional three-pole thyristors) currently on the market can be triggered stably with a small input, unless an input is applied to the main electrode on the gate side, that is, the _T1 electrode, so that the gate or G electrode becomes negative. Conventionally, as shown in FIG. 1, the solution was to make the positive pole of the power supply B of the control circuit common to one pole of the AC power supply E. However, since it is customary for general electronic circuits to have a common negative terminal, there are cases where it is absolutely necessary to use a common negative terminal for the power supply B of the control circuit, and in such cases, the pulse transformer P and diode are A method using D was used, but the drawback was that pulse transformers were expensive and not easy to obtain.

The object of the present invention is to solve the above-mentioned problems and to construct a single power supply control negative pole common type triac drive circuit using general elements such as transistors, resistors, and capacitors.

To explain in detail using example diagrams, in FIG. 3,
The _T1 electrode of the triax S, the emitter of the transistor Q, that is, the ground terminal a, the negative pole of the DC power supply B, and one pole of the AC power supply E are commonly connected, and the _T2 electrode of the triax S is connected through the load L. and is connected to the other pole of the AC power supply E. The collector of the transistor Q is connected to the positive pole of the DC power source B via a load resistor _R1 , and a resistor R and a capacitor C are connected in series between the G electrode of the triax S and the collector of the transistor Q.

In FIG. 3, at the base of transistor Q,
When a positive pulse as shown in the figure is input, transistor Q becomes conductive and the charge on capacitor C changes from C to R.
→Q → T ₁ → Discharge along the path of G, and try-attack S
is triggered. In other words, the triax S is
Since it is triggered by a G input lower than the _T1 potential,
It turns on stably even with a small input. When the transistor Q is cut off, a charging current flows through the capacitor C from the power source B along the path R ₁ →R → C → G → T ₁ →B to prepare for the next trigger.

According to the present invention, the negative side of the DC power supply of the transistor circuit that controls the triax is made common to one pole of the AC power supply, and the _T1 pole of the triax connected to the AC power supply in series with the load is grounded to the driving transistor circuit. The gate electrode of the triac is It can be made negative with respect to the _T1 electrode, and has the effect of triggering the tri-attack with a small input.Therefore, as a DC power supply, the current consumption is almost only the charging current of the capacitor. Therefore, the capacity is extremely small, and it is possible to construct a so-called energy-saving type device. Moreover, the negative side of the DC power supply of the transistor circuit that controls the triax is connected to the AC power supply.
By making the power supply common to the negative pole of the control circuit, it is possible to use common elements such as transistors, resistors, and capacitors instead of using expensive parts such as pulse transformers as in the past. In addition to being easy to configure, the negative side of the DC power supply for transistor circuits can be shared in common, similar to general electronic circuits, and has the effect of simplifying circuit design.

FIG. 4 shows another embodiment, which is a circuit for increasing the gate trigger current in the case of a large capacity triac. The collector of the transistor Q is further connected to one end of a capacitor C via an output stage formed by connecting transistors Q ₁ and Q ₂ in a totem pole connection, and the other end of the capacitor C is connected to the gate G of the triac S.

In FIG. 4, when a negative pulse as shown is applied to the base of transistor Q, transistor Q is turned off, transistor _Q1 is turned off, and transistor _Q2 is turned on. Therefore, the charge on capacitor C is C→R→
Discharge occurs along the path Q ₂ →T ₁ →G, and the triax S is
It will be triggered by a negative gate input voltage for _T1 pole. In this way, the triac can be stably turned on by grounding the driving transistor circuit A on the negative side and by setting the gate trigger voltage to negative. Next, when transistor Q returns to on, transistors Q ₁ and Q ₂ also return to on and off, respectively, and capacitor C is charged along the path of B→Q ₁ →R ₁ →C→G→T ₁ . Also, in the circuit of Fig. 4, when transistor Q is turned off, B→R ₂ →R ₃ →
The input current of transistor Q ₂ flows through the path R ₄ →Q ₂ , but by choosing a transistor with a high current amplification rate for transistor Q ₂ , this current can be made very small, so it is The advantage is that the current required is extremely small.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing a conventional example, Fig. 2 is a main circuit diagram showing another conventional example, Fig. 3 is a circuit diagram showing one embodiment of the present invention, and Fig. 4 is a circuit diagram showing another embodiment. FIG. E...AC power supply, B...DC power supply, S...Triack, L...Load, Q, _Q1 , _Q2 ...Transistor, C
…Capacitor, R, R ₁ , R ₂ , R ₃ , R ₄ … Resistor, D
...diode, A...transistor circuit, a...ground terminal, b...output terminal.

Claims (1)

[Claims] 1. Make the negative side of the DC power supply of the transistor circuit that controls the triax common to one pole of the AC power supply, and connect the _T1 pole of the triax connected to the AC power supply in series with the load together with the ground terminal of the driving transistor circuit. A triac drive circuit characterized in that the output terminal of the transistor circuit is connected to the gate of the triac via a capacitor and, if necessary, a resistor.