JPH0242073Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a bidirectional 3-terminal thyristor trigger circuit, and particularly when performing AC power control, the bidirectional 3-terminal thyristor (hereinafter referred to as TRIACK) is triggered near the zero voltage phase, and the thyristor trigger circuit is activated. The present invention relates to a triact trigger circuit that has a function of detecting conduction and stopping the trigger signal.

Conventionally, this type of trigger circuit detects the voltage between terminals _T1 and _T2 of triac 2 using PNP transistors 4 and 5, as shown in FIG.
Detects zero voltage phase in both positive and negative directions and detects conduction of triac 2, and detects NPN transistor 1.
0 to amplify the signal and generate a trigger pulse.

In the figure, the PNP transistor 4 performs zero voltage phase detection when the _T1 terminal side of the triac 2 of the AC power source 1 is positive, and performs a grounded emitter amplification operation. The PNP transistor 5 performs zero voltage phase detection when the terminal T2 side of the triac ₂ is positive,
The emitter follower operates using the AC power supply 1 as a signal source.

In this type of circuit, the constant design is such that the trigger pulse is applied as close to the zero voltage phase as possible in order to reduce noise generation, but in the circuit shown in Figure 1, the PNP transistor 5 operates as an emitter follower, so the signal Since current amplification cannot be performed, the resistor 7 is made small to increase the emitter current when the AC power source 1 is close to the zero voltage phase, thereby bringing the trigger pulse supply close to the zero voltage phase. For this reason, it was necessary to use a resistor 7 with a large allowable loss. In addition, in order to stop the trigger signal after triax 2 conducts, the ON voltage of PNP transistors 4 and 5 is divided by resistors 6 and 7, and after triax 2 conducts, the PNP
The voltage applied between the base and emitter of transistors 4 and 5 is reduced. This constant design takes into account variations in the on-voltage of the triac 2 and variations in the base-emitter voltage of the PNP transistors 4 and 5, and increases the ratio of the resistor 7 to the resistor 6, so that the conduction of the PNP transistors 4 and 5 is This had to happen at a certain point when the AC power supply 1 had passed from the zero voltage phase. Furthermore, in this circuit, in order to make the polarity of the trigger pulse negative and to amplify the detection signal current, an NPN transistor 10
was necessary.

In this invention, by operating the transistor for zero voltage phase detection with its emitter grounded, this transistor has the function of detection and current amplification, and the zero voltage phase and the conduction signal of the triac are connected between the _T2 terminal and the gate terminal. By obtaining this, it is possible to omit a transistor for inverting amplification, to not use a high power loss resistor, and to apply a trigger pulse near the zero voltage phase.

Figure 2 shows an embodiment of the present invention, in which 1 is an AC power supply, 2 is a triax, 3 is a load resistor, 7, 1
3, 17, 18 are resistors, 11 is a capacitor, 12
is a diode, 14 is a PNP transistor, 15
is an NPN transistor, and 16 is a constant voltage diode.

In the figure, when a power source 1 is turned on, a capacitor 11 is charged through a diode 12 and a resistor 13 with the terminal _T1 side of the triac 2 being positive.
When the AC power supply 1 is in a cycle in which the terminal T ₁ side of the triax 2 is positive, the base current of the PNP transistor 14 flows from the AC power supply 1 to the terminal T ₁ of the triax 2, the emitter, the base, the resistor 7, and the load resistance of the PNP transistor 14. Because it flows through 3,
The PNP transistor 14 performs a grounded emitter current amplification operation, and the emitter current of the PNP transistor 14 is applied from the capacitor 11 via the resistor 17 as the trigger current of the triac 2.

When the triac 2 becomes conductive due to the application of the trigger current, the voltage between the terminal T ₂ and the gate terminal becomes sufficiently lower than the on-voltage between the terminals T ₁ and the terminals T ₂ , so that the base bias of the PNP transistor 14 is applied. The trigger current will no longer be supplied.

This trigger current stop operation causes capacitor 1
It is possible to suppress unnecessary discharge of 1, resulting in a power-saving design.

If the AC power supply 1 is in a cycle in which the _T2 terminal of the triac 2 is positive, the NPN transistor 15
Since the base current flows from the AC power supply 1 through the load resistor 3, the constant voltage diode 16, the base of the NPN transistor 15, the emitter, and the capacitor 11, the NPN transistor 15 performs a grounded emitter current amplification operation and is used as the trigger current of the triac 2. is from capacitor 11 through resistor 18
A collector current of NPN transistor 15 is applied.

After the triax 2 is turned on, the AC power supply 1 operates in the same way as in the cycle in which the _T1 terminal of the triax 2 is positive.

Since the voltage regulator diode 16 limits the charging voltage of the capacitor 11 to the Zener voltage, it facilitates the selection of the collector-emitter withstand voltage of the transistors 14 and 15 and the design of the trigger current, and shifts the voltage level after the triator 2 conducts. This prevents the charge of the capacitor 11 from being wasted through the collector-emitter of the NPN transistor 15.

FIG. 3 shows another embodiment of the present invention.

In the embodiment shown in FIG. 2, the triat trigger current was a gate negative mode current, whereas the third
The trigger current in the figure is in a gate positive mode and has a polarity opposite to that of the embodiment shown in FIG.

The operation is similar to the embodiment shown in Fig. 2;
PNP transistor 14, NPN transistor 15
are respectively the NPN transistor 19 and
It corresponds to the PNP transistor 20 and supplies a trigger current with opposite polarity.

As described above, in the circuit of the present invention, by operating the transistor for zero voltage phase detection with its emitter grounded, this transistor has the function of detection and current amplification, and the detection of the zero voltage phase and the conduction of the triac is carried out at terminal _T2 . and the gate terminal, there is an advantage that the trigger pulse can be supplied in the vicinity of the zero voltage phase without adding an amplifying transistor or using a high power dissipation resistor.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a conventional triact trigger circuit, FIG. 2 is a circuit diagram showing one embodiment of the present invention, and FIG. 3 is a circuit diagram showing another embodiment of the present invention. In the figure, 1... AC power supply, 2... Triack, 3... Load resistance, 4, 5, 14, 20...
...PNP transistor, 6, 7, 8, 9, 13,
17,18...Resistance, 10,15,19...
NPN transistor, 11...Capacitor, 12
...Diode, 16... Constant voltage diode.

Claims (1)

[Scope of utility model registration request] A bidirectional three-terminal thyristor having a first terminal connected to one end of the AC power source and a second terminal connected to the other end of the AC power source via a load, and one end connected to the one end of the AC power source. a diode connected between the other end of the AC power supply and the other end of the capacitor, and the bidirectional 3
emitter connected to the gate of the terminal thyristor,
a first conductivity type thyristor having a base connected to the second terminal of the bidirectional three-terminal thyristor via a first resistor and a collector connected to the other end of the capacitor via a second resistor; 1 transistor, and a collector connected to the gate of the bidirectional three-terminal thyristor via a third resistor;
a bidirectional three-terminal thyristor trigger circuit comprising a second transistor of opposite conductivity type having a base connected to the base of the first transistor via a constant voltage circuit and an emitter connected to the other end of the capacitor; .