JPS5854741B2 - semiconductor switch circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor switch circuit, and more particularly to an improvement of a switch circuit having a self-holding function using a triac.

FIG. 1 is a circuit diagram showing a conventional switch circuit having a self-holding function using a triac.

In the figure, 1 is an AC power supply, 2 is a triac, and 3 is a load.

A first main electrode T1 of the triac 2 is connected to one connection terminal of the AC power source 1 via a load 3, and a second main electrode T2 thereof is connected to the other connection terminal of the AC power source 1.

4 is a capacitor, 5 is a rectifier diode, and capacitor 4
One end is connected to the fourth main electrode T1 of the triac 2, and the other end is connected to the connection point between the load 3 and the AC power source 1 via the rectifier diode 5.

6, 1 is a push button switch whose contact is closed only when it is pressed; 8 is a push button switch whose one end is connected to the gate G of the triac 2, and the other end is connected to the connection point between the capacitor 4 and the rectifier diode 5; It is a resistance for limiting the IT flow.

Push button switch 1 is connected to both ends of resistor 8.

9 has one end connected to the second main electrode T2 of the triac 2 and the other end connected to the triac 2 via the push button switch 6.
This is a current limiting resistor connected to the connection point between the gate G and the resistor 8.

Next, the operating mechanism of the conventional switch circuit described above will be explained.

First, when the push button switch 6 is pressed to close its contact, the connection point between the AC power source 1 and the triac 2 becomes a positive potential.
In a half cycle (hereinafter referred to as a "positive half cycle") in which the connection point between the AC power source 1 and the load 3 becomes a negative potential, the AC power source 1 is connected to the resistor 9, the push button switch 6, and the first gate G1 of the triac 2. A current flows in the loop returning to the AC power source 1 through the main electrode T1 and the load 3, and this current turns on the triac 2, so that power is supplied from the AC power source 1 to the load 3.

In addition, in a half cycle (hereinafter abbreviated as "negative half cycle") in which the connection point between the AC power supply 1 and the triac 2 has a negative potential and the connection point between the AC power supply 1 and the load 3 has a positive potential, the above-mentioned loop A current flows in the opposite direction to the above current.

This reverse current causes the triac 2 to turn on, as in the positive half cycle, and power is supplied from the AC power supply 1 to the load 3.

In this way, while the contact of the pushbutton switch 6 is closed, power is supplied from the AC power source 1 to the load 3, and during the positive half cycle, the capacitor 4 is charged to the polarity shown by the action of the rectifier diode 5. be done.

Next, when the contacts of the pushbutton switch 6 are opened, the gate current from the pushbutton switch 6 to the gate G of the triac 2 disappears, and the transition to the on state of the triac 2 for the next half cycle is stored in the capacitor 4. It is done by electric charge.

That is, when the pushbutton switch 6 is opened during the positive half cycle of the AC power source 1, the capacitor 4 is charged during this positive half cycle, and the point in time when the voltage of the AC power source 1 becomes lower than the voltage of the capacitor 4 is reached. During the next negative half cycle, the discharge current of the capacitor 4 flows in a loop from the capacitor 4 through the [th] main electrode T1, the gate G1 and the resistor 8, and returns to the capacitor 4.

Therefore, even if the contact of the pushbutton switch 6 is opened, the gate current continues to be supplied to the triac 2, so that the triac 2 continues to be in the on state even during the negative half cycle.

Furthermore, the discharge time constant, which is the product of the capacitor 4 and the resistor 8, should be set large so that a current greater than the gate trigger current can flow through the gate G of the triac 2 even at the end of the negative half cycle. For example, even in the next positive half cycle,
Triac 2 remains on.

During this positive half cycle capacitor 4 is charged again,
TRIAC 2 can continue to remain on.

In this way, by increasing the discharge time constant, even when the pushbutton switch 6 is opened during the negative cycle of the AC power supply 1, the triac 2 is turned on by the discharge current of the capacitor 4, and the triac 2 is turned on during the next positive cycle. During the half cycle, the capacitor 4 is charged again and the triac 2 can continue to remain on.

Next, when the contact of the pushbutton switch γ is closed, the charge stored in the capacitor 4 is immediately discharged in a loop that returns to the capacitor 4 through the first main electrode T1, the gate G1, and the pushbutton switch γ. Regardless of whether the half cycle is positive or negative, the gate current is no longer supplied to the triac 2 at the beginning of the next half cycle, so the triac 2 is turned off.

In this way, once triac 2 is turned off,
Since the pushbutton switch 6 is open, no charge is stored in the capacitor 4, so the pushbutton switch γ
Even if the triac 2 is released, the triac 2 will not be turned on from now on.

As described above, when the push button switch 6 is pressed, power is supplied from the AC power source 1 to the load 3, and when the push button switch 7 is pressed, the supply of power is stopped.

By the way, in a switch circuit with a self-holding function using a triac, the discharge period of the capacitor 4 must last for at least half a cycle of the AC power supply 1 from the end of a positive half cycle to the beginning of the next positive half cycle. It is.

Therefore, even if the discharge current of the capacitor 4 is large immediately after the start of discharge, if the discharge time constant of the capacitor 4 is small, the discharge current will attenuate below the gate trigger current of the triac 2 at the beginning of the next positive half cycle. TRIAC 2 will not turn on.

To prevent this, it is necessary to set the discharge time constant of the capacitor 4 to a large value.

However, if the resistance value of the resistor 8 is set to a large value, the discharge current of the capacitor 4 becomes less than the gate current of the triac 2. Therefore, by setting the resistance value of the resistor 8 to a large value, the discharge time constant of the capacitor 4 is increased. Can not do it.

Therefore, the only way to increase the discharge time constant is to increase the capacitance value of the capacitor 4.

If the capacitance value of the capacitor 4 becomes large, not only the shape and size of the capacitor 4 becomes large, but also the power loss of the resistor 8 increases, so it is necessary to use the resistor 8 with a large shape and size.

. Generally, as the rated current capacity of a triac increases, its gate trigger current also increases, so it is necessary to increase the discharge current of the capacitor.

To give an example for reference, a triac with a rated current of about IOA has a gate trigger current of 15 to 30m.
It is about A.

Therefore, in a conventional semiconductor switch using a high power triac with a large rated capacity, a large capacity capacitor 4
Moreover, since the power loss of the resistor 8 is large, it is very difficult to reduce the size of the resistor 8.

The present invention has been made in view of the above-mentioned drawbacks, and uses a low-power triac with a small gate trigger current as an auxiliary triac to significantly reduce the capacitance of the capacitor that supplies the gate trigger current. The purpose is to miniaturize a switch circuit using a triac.

FIG. 2 is a circuit diagram showing an embodiment of the switch circuit according to the present invention.

In the figure, the second main electrode T2a is connected to the second main electrode T2 of the main triac 2 and the first main electrode T1a is connected to the second main electrode T2a of the main triac 2.
is the main triac, an auxiliary triac 42 is connected to the gate G of the main triac 2, one end is connected to the connection point between the gate G of the main triac 2 and the first main electrode T1a of the auxiliary triac 2a, and the other end is connected to the rectifier diode 5. AC power supply 1 through
A capacitor 8a connected to the connection point between the capacitor 4a and the load 3 is a resistor whose one end is connected to the gate Ga of the auxiliary triac 2a and the other end is connected to the connection point between the capacitor 4a and the rectifier diode 5.

One end of the push button switch 6 is connected to the connection point between the second main electrode T2a of the auxiliary triac 2a and the AC power source 1 via a resistor 9, and the other end is connected to the gate G of the auxiliary triac 2a.
connected to a.

The pushbutton switch 7 is connected between the first main electrode T1a of the auxiliary triac 2a and its gate Ga.

Next, the operating mechanism of the switch circuit of this embodiment will be explained.

First, when the push-button switch 6 is pressed and its contact is closed, in the positive half cycle, the voltage from the AC power supply 1 to the resistor 9, the push-button switch 6, and the auxiliary triac 2a (Ga1) is
A current flows in a loop through the first main electrode T1a1, the gate G1 of the main triac 2, the fourth main electrode T1, and the load 3 and back to the AC power supply 1.

This current immediately turns on the auxiliary triac 2a.

When the auxiliary triac 2a is turned on, a current larger than the above current is supplied from the auxiliary triac 2a to the gate G of the main triac 2, the main triac 2 is turned on, and power is supplied to the load 3 from the AC power supply 1.

At this time, a current flows in a loop from the AC power supply 1 through the second main electrode T2 of the main triac 2, its gate G1 capacitor 4a1, and the rectifier diode 5 and returns to the AC power supply 1. This current is rectified by the rectifier diode 5. As a result, the capacitor 4a is charged to the polarity shown.

In the negative half cycle, the AC power source 1 passes through the load 3, the first main electrode T1 of the main triac, its gate G1, the first main electrode T1a1 of the auxiliary triac, its gate Ga1, the push button switch 6 and the resistor 9. A current flows in the loop returning to.

In addition, for recirculation, the auxiliary triac 2a is connected to the capacitor 4a.
A discharge current of the capacitor 4a flows in a loop returning to the capacitor 4a through the gate Ga1 of the main electrode T1 a % and the resistor 8a, and this discharge current turns on the auxiliary triac 2a.

When the auxiliary triac 2a is turned on, a current larger than the discharge current is supplied from the auxiliary triac 2a to the gate 1-G of the main triac 2, the main triac 2 is turned on, and power is supplied to the load 3 from the AC power supply 1. Ru.

In this manner, power continues to be supplied to the load 3 from the AC power source 1 while the contact of the push button switch 6 is closed.

Next, the case where the push button switch 6 is opened again will be described.

If the pushbutton switch 6 is opened at any time during a positive half cycle, the discharge current of the capacitor 4a is switched from the end of this positive half cycle to the following negative half cycle to the first main current of the auxiliary triac 2a. Since it flows from the electrode TIa to its gate Ga, this discharge current turns the auxiliary triac 2a on at the beginning of the half cycle of the above number.

When the auxiliary triac 2a is turned on, the main triac 2 is turned on, as described above, and power is supplied from the AC power supply 1 to the load 3.

In this way, even during the above number of half cycles, the capacitor 4
a continues to discharge, but if the discharge time constant of capacitor 4a is set large so that this discharge current becomes larger than the gate trigger current of auxiliary triac 2a until the beginning of the next positive half cycle, then At the beginning of the positive half cycle, the auxiliary triac 2a is turned on again, and at the same time the main triac 26 is turned on, and power supply to the load 3 is maintained.

When the main triac 2 is turned on during the positive half cycle, the capacitor 4a is charged and returns to its original state.

Therefore, even if the push button switch 6 is opened, the capacitor 4a1 rectifier diode 5, the auxiliary triac 2
Power can be continuously supplied from the AC power source 1 to the load 3 due to the self-holding ability that is influenced by the discharge time constant of the capacitor 4a of the self-holding circuit consisting of a1 and the resistor 8a.

Then, even if the pushbutton switch 6 is opened at any point in the negative half-cycle, the auxiliary triac 2a is opened at the beginning of the next positive half-cycle by a similar operating mechanism as described above.
is turned on, the main triac 2 is also turned on, and power continues to be supplied to the load 3.

The case where the contact of the pushbutton switch 6 is closed during the positive half cycle has been explained above, but the operating mechanism will also be explained when it is closed during the negative half cycle, as the operating mechanism is easier to understand than the operating mechanism described above. omitted.

Next, when the contact of the push button switch T is closed, the first main electrode T1a of the auxiliary triac 2a and its gate Ga
Since the charge in the capacitor 4a is discharged at the same time that the auxiliary triac 2a is short-circuited, the auxiliary triac 2a is turned off in the next half cycle.

Therefore, the gate trigger current is not supplied to the main triac 2 of 4G, so the main triac 2 is turned off.

Therefore, when the main triac 2 and the auxiliary triac 2a are turned off, there is no charging loop to the capacitor 4a, so the capacitor 4a is not charged.

Therefore, even if the pushbutton switch 1 is opened, the main triac 2 is in the OFF state, so the load 3 is disconnected from the AC power supply 1.
The supply of power to is stopped.

Note that the push button switch 1 connected to the first main electrode T1a of the auxiliary triac 2a and its gate Ga may be connected to both ends of the resistor 8a.

The self-holding ability of this embodiment depends on the discharge time constant, which is the product of the capacitance value of the capacitor 4a and the resistance value of the resistor 8a.

By the way, the gate trigger current of the auxiliary triac 2a is smaller than the gate trigger current of the main triac 2, and can be reduced to at least 1/10 or less, so the resistance value of the resistor 8a can be made smaller than that of the resistor 8 of the conventional switch circuit. It can be increased by 10 times compared to .

Therefore, the capacitance value of the capacitor 4a can be set to 1710 of the capacitor 4 of the conventional switch circuit.

The resistor 9 of this embodiment is divided into two, and the divided resistors are connected between the second main electrode T2 of the main triac 2 and the second main electrode T2a of the auxiliary triac 2a and the second anode T2a. There is no problem even if it is inserted between the push button switch 6 and the push button switch 6.

As described above in detail, according to the present invention, a low-power auxiliary triac is connected between the gate of the main triac and its second main electrode, and the first main electrode of the auxiliary triac and its second main electrode are connected to each other. Since a self-holding circuit consisting of a capacitor and a resistor is connected between the gate and the gate, the following effects are achieved.

That is, since the gate trigger current of the auxiliary triac is significantly smaller than that of the main triac, the capacitance of the capacitor of the self-holding circuit can be reduced.

Therefore, even if you are creating a switch circuit using a main triac with a large rated current, you only need to add one low-power auxiliary triac without using a large capacitor, making the switch circuit relatively simple. In addition, since the capacitance of the capacitor becomes smaller, there is less power loss due to the resistance of the self-holding circuit, and the temperature of the switch circuit does not rise due to this power loss, making it possible to downsize the switch circuit of the high-power triac. be able to.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a conventional switch circuit having a self-holding function using a triac, and FIG. 2 is a circuit diagram showing an embodiment of the switch circuit according to the present invention. In the figure, 1 is an AC power supply, 2 is a main triac, 2a
is the auxiliary triac, 3 is the load, 4a is the capacitor, 5
is a rectifier diode, 6 is the first push button switch, γ
is a second pushbutton switch, 8a is a first resistor, and 9 is a second resistor. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1 A main triac whose first main electrode is connected to the fourth terminal of the AC power source via a load and whose second main electrode is connected to the second terminal of the AC power source, and a first main triac connected to the gate of this main triac. an auxiliary triac having a main electrode connected thereto and a second main electrode connected to a second main electrode of the main triac, and a rectifier having a cathode connected to a connection point between the load and the first terminal of the AC power supply. A diode, one end connected to the main electrode of the auxiliary triac and the other end connected to the anode of the rectifier diode, a capacitor, one end connected to the gate of the auxiliary triac and the other end connected to the capacitor and the rectifier diode. a first resistor connected to the connection point of the auxiliary triac; a first pushbutton switch having one end connected to the second terminal of the AC power source via the second resistor and the other end connected to the gate of the auxiliary triac; , and one end connected to the first main electrode of the auxiliary triac and the other end connected to the gate of the auxiliary triac, or one end connected to one end of the first resistor and the other end connected to the other end of the first resistor. a second connected to the end of the capacitor for discharging the charge of the capacitor;
a push-button switch for discharging the charge of the capacitor between the first main electrode and the gate of the auxiliary triac and through the @1 resistor during a half cycle of the AC power supply. The capacitance value of the capacitor and the resistance value of the first resistor are set so that a predetermined amount or more of the charged charge remains, and the charged charge of the capacitor is discharged only between the first main electrode and the gate of the auxiliary triac. The semiconductor switch circuit may be characterized in that the capacitance value of the capacitor is set so that the charge charged in the capacitor is equal to or less than the predetermined amount during a half cycle of the AC power supply.