JPH0134556Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a bidirectional three-terminal thyristor trigger circuit, and in particular, when performing AC power control, the bidirectional three-terminal thyristor (triack) is triggered near the zero voltage phase, and the triax conducts. This invention relates to a triact trigger circuit that has a function of detecting that a trigger signal has been generated and stopping the trigger signal.

Conventionally, this type of trigger circuit detects the zero voltage phase in both positive and negative directions by detecting the voltage between terminals _T1 and _T2 of triac 2 using PNP transistors 4 and 5, as shown in FIG. Then, the conduction of the triax 2 is detected, and the signal is current-amplified by the NPN transistor 10 to generate a trigger pulse.

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

In this type of circuit, in order to reduce noise generation, the trigger pulse is constant-designed to be applied as close to the zero voltage phase as possible, but in the circuit shown in Figure 1, the PNP transistor 4 operates as an emitter follower. Since current amplification of the signal cannot be performed, the resistor 7 is made small to increase the emitter current when the AC power supply 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, after the triax 2 conducts, in order to stop the trigger signal, the on-voltage of the PNP transistors 4 and 5 is divided by resistors 6 and 7, and after the triax 2 conducts, it is applied between the base and emitter of the PNP transistors 4 and 5. lowering the voltage. 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 in order to increase the ratio of the resistor 7 to the resistor 6, the conduction of the PNP transistors 4 and 5 is This must occur at a certain point when the AC power supply has passed from the zero voltage phase. Furthermore, in this circuit, the NPN transistor 10 is required for the purpose of making the polarity of the trigger pulse negative and for amplifying the detection signal current. As a result, the trigger mode of the triax 2 was the T ₂ ⁺ G ^- and T ₂ ^- G ^- modes, which were somewhat insensitive, and required a large trigger current.

In this invention, by operating the zero-voltage phase detection transistor with its emitters grounded, this transistor has detection and current amplification functions, and the trigger mode of the triax can be changed to the sensitive T ₂ ⁺ G ⁺ and
By setting the T ₂ ^- G ^- mode and obtaining the zero voltage phase and the conduction signal of the triac from between the terminal T ₂ and the gate terminal, it is possible to omit the transistor for inverting amplification, do not use a high power dissipation resistor, and reduce the voltage to zero. This realizes trigger pulse application near the phase.

FIG. 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, 16 and 17 are resistors, 11 and 18 are capacitors, 12 and 19 are diodes, 14 is an NPN transistor, and 15 is a PNP transistor.

In the figure, when the power supply 1 is turned on, the capacitor 11 is charged through the diode 12 and the resistor 13 with the _T1 terminal side of the triac 2 being positive.
The capacitor 18 is charged through a resistor 13 and a diode 19 to have a polarity opposite to that of the capacitor 11 . When the AC power supply 1 is in a cycle in which the _T1 terminal side of the triac 2 is positive, the base current of the PNP transistor 15 flows from the AC power supply 1 to the _T1 terminal of the triac 2,
Since the current flows through the emitter, base, and resistor 7 of the PNP transistor 15 and the load resistor 3, the PNP transistor 15 performs an emitter-grounded current amplification operation, and the trigger current of the triax 2 is generated from the PNP transistor 15 from the capacitor 11 through the resistor 17. Emitter current is given. This trigger mode is T ₂ ^- , G ^- , which is a mode in which conduction is easy. Triack 2 is activated by applying trigger current.
When conducts, the voltage between the terminal T ₂ and the gate terminal becomes sufficiently lower than the on-voltage between the terminal T ₁ and the terminal T ₂ , so that the base bias of the PNP transistor 15 is no longer applied, and the trigger current is not supplied. Stop.

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

When the AC power supply 1 is in a cycle in which the terminal T 2 of the triac ₂ is positive, the polarity is reversed and the operation state is the same as described above, and a trigger current is supplied from the capacitor 18 by the NPN transistor 14. The trigger mode in this case is T ₂ ⁺ G ⁺ , which is an easy trigger mode.

FIG. 3 shows an embodiment of the present invention in which a transistor 22 is connected to control the supply and stop of trigger pulses using electrical signals.

In the figure, when a negative signal is applied to the control terminal 21, the transistor 22 conducts as a bidirectional transistor, and the PNP transistor 1
No base current flows through NPN transistor 5, NPN transistor 15, and NPN transistor 14, and no trigger pulse is generated. When no negative signal is applied to the control terminal 21, the trigger operation is the same as that of the circuit shown in FIG.

As described above, in the circuit diagram of the present invention, by operating the zero-voltage phase detection transistor with its emitter grounded, this transistor has the detection and current amplification functions, and the triac is easily conductive.
The trigger mode is T ₂ ⁺ G ⁺ and T ₂ ^- G ^- , and the detection of the zero voltage phase and the conduction of the triax is performed at the terminal T _2.
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 drawings]

FIG. 1 is a circuit diagram showing a conventional triact trigger circuit, FIG. 2 is a circuit diagram showing an embodiment of the present invention, and FIG. 3 is a circuit for controlling the circuit shown in FIG. 2 using electric signals. In the figure, 1... AC power supply, 2... Triack, 3...
Load resistance, 4, 5, 15, 22...PNP transistor, 6, 7, 8, 9, 13, 16, 17, 2
0...Resistor, 10,14...NPN transistor,
11, 18... Capacitor, 12, 19... Diode, 21... Control terminal.

Claims (1)

[Scope of utility model registration request] first and second capacitors each having one end connected to one end of the AC power source; a first resistor having one end connected to the other end of the AC power source; and the first resistor having one end connected to the other end of the AC power source.
a first diode having an anode connected to the other end of the capacitor and a cathode connected to the other end of the first resistor; a second diode having an anode connected to the other end; and a bidirectional diode having a first terminal connected to the one end of the AC power source and a second terminal connected to the other end of the AC power source via a load. 3-terminal thyristor and the bidirectional 3
An emitter is connected to the gate of the terminal thyristor,
A base is connected to the second terminal of the bidirectional three-terminal thyristor via a second resistor, and the base is connected to the second terminal of the bidirectional three-terminal thyristor.
a PNP transistor whose collector is connected to the other end of the capacitor via a third resistor; an emitter is connected to the gate of the bidirectional three-terminal thyristor; a base is connected to the base of the PNP transistor; A collector is connected to the other end of the capacitor No. 2 via a fourth resistor.
A bidirectional three-terminal thyristor trigger circuit comprising an NPN transistor.