JP2002100970A - Switching circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve the high-speed operation of a switch, which supplies operating power to a load from an AC power supply regarding a switching circuit, using a field-effect transistor. SOLUTION: The switching circuit is provided with two field-effect transistors Q1, Q2, in which built-in diodes D1, D2 are connected in series so as to be reverse in polarity across a power supply PW and loads LD1 to LDn and control circuits CON1 to CONn, which apply control voltages to gates of the two transistors Q1, Q2 so as to on/off-control the transistors Q1, Q2. Gate voltages are applied to the transistors Q1, Q2 as the power supplies for photoelectric converters PC1 to PCn, for capacitors C1 to Cn and for the control circuits CON1 to CONn.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a field effect transistor which can control the supply and stop of operating power from a power source to various loads such as a linear motor, a normal motor, an electromagnetic clutch, an electromagnetic valve and an electromagnetic relay at a high speed. Switch circuit.

[0002]

2. Description of the Related Art An apparatus including various mechanically operating parts includes a plurality of motors, electromagnetic clutches, and the like.
The on / off of the switch is controlled. The switch in this case is different from a manual power switch, etc.
The on / off operation is performed relatively frequently. Therefore, it is common to use a relay.

For example, as shown in FIG. 7, a power supply PW is connected between loads LD1 to LDn such as a motor and an electromagnetic clutch and a power supply PW.
By individually connecting the contacts S1 to Sn of the relays and selectively driving the relays (not shown), the contacts S1 to S
n is selectively turned on, and the operating power is supplied to the load from the power supply PW via the turned on contact. If the motor as a load is frequently rotated and stopped, the relay contacts for driving the load are frequently turned on and off.

[0004]

The relay contact S1 for supplying operating power from the power supply PW to the loads LD1 to LDn.
To Sn have an operation delay of about several tens ms or more.
Therefore, the loads LD1 to LDn can be quickly driven at a predetermined timing.
It is difficult to control on / off of the operation of the relay, and the power for driving the relay cannot be ignored if the number of relays is large. Noise generated when the contacts S1 to Sn are turned on and off is generated by the contacts S1 to Sn and the load L.
There is a problem that it propagates through a connection line between D1 and LDn and adversely affects other electronic circuits.

Therefore, a semiconductor switch that does not include a mechanical contact and can operate at high speed is considered. As such a semiconductor switch, a bipolar transistor, a field effect transistor, or the like is used. However, the bipolar transistor can be applied to a DC power supply but cannot be applied to an AC power supply. Field effect transistors
A configuration with a low on-resistance of about several mΩ is also known and can be applied to an AC power supply, but a field-effect transistor having a relatively large current capacity has a configuration including a built-in diode (also referred to as a body diode). There is a problem that a rectified current flows through this built-in diode. An object of the present invention is to provide a switch circuit using a field-effect transistor capable of high-speed operation even when the power supply is AC.

[0006]

A switch circuit according to the present invention will be described with reference to FIG.
To LDn, built-in diodes D1 and D2, respectively.
Are applied in series with each other so that the polarities of the field effect transistors Q1 and Q2 are opposite to each other, and a control voltage is applied to the gates of the two field effect transistors Q1 and Q2 to turn on the field effect transistors Q1 and Q2. , And control circuits CON1 to CONn for performing off control.

Each of the control circuits CON1 to CONn can include a transistor for applying the operating voltage converted by the photoelectric converter to the gates of the field effect transistors Q1 and Q2 according to a control signal. The first transistor applies the operating voltage converted by the photoelectric converter to the gates of the field effect transistors Q1 and Q2 in accordance with the ON control signal, and the input capacitance of the gates of the field effect transistors Q1 and Q2 in accordance with the OFF control signal. And a second transistor for discharging the charge of the second transistor. The control circuit includes a control transistor that applies a control signal to a base, and a complementary transistor that is controlled by the control transistor.The operating voltage converted by the photoelectric converter is used to control one of the conductive transistors of the complementary transistor. And a gate connected to the gate of the field-effect transistor via the other conductive type transistor to discharge the charge of the input capacitance of the field-effect transistor.

[0008]

FIG. 1 is an explanatory view of a first embodiment of the present invention, wherein PW is a power supply, LD1 to LDn are loads such as a motor and an electromagnetic clutch, Q1 and Q2 are field effect transistors, D1 , D2 are built-in diodes of field effect transistors, CON1 to CONn are control circuits, C1 to Cn
Denotes a capacitor, PC1 to PCn denote photoelectric converters composed of electromotive force semiconductor elements such as solar cells, P denotes a light source such as a light emitting diode or a lamp, and cont1 to connt denote control signals from a higher-level control unit (not shown). .

The sources of the two field effect transistors Q1 and Q2 are connected in common, and one of the field effect transistors
1 is connected to the power supply PW, and the drain of the other field effect transistor Q2 is connected to the load. That is, the built-in diodes D1 and D2 are connected in series such that they have opposite polarities. Thus, when the field effect transistors Q1 and Q2 are turned off, the power supply PW is reliably turned off when the power supply PW is a DC power supply.
Since 2 has the opposite polarity, it can be surely turned off. When the field effect transistors Q1 and Q2 are turned on,
Whether the power supply PW is direct current or alternating current, the operating power can be supplied to the load.

The control circuits CON1 to CONn apply a gate voltage for ON / OFF control of the field effect transistors Q1 and Q2 in accordance with control signals cont1 to conn. Must be electrically insulated. For this purpose, the primary winding of the transformer is connected to, for example, a power supply PW, and the transformer is provided with secondary windings corresponding to the control circuits CON1 to CONn. It can also be.
In that case, the area occupied by the transformer and the rectifying / smoothing circuit increases.

Therefore, as shown in the figure, the light source P and the photoelectric converters PC1 to PCn corresponding to the control circuits CON1 to CONn are used.
And a light source P such as a light emitting diode or a lamp
And emits the emitted light beams to the photoelectric converters PC1 to PC1
Cn, and the converted output voltages of the photoelectric converters PC1 to PCn are stored in the capacitors C1 to Cn.
The terminal voltage of Cn is a gate voltage applied from the control circuits CON1 to CONn to the gates of the field effect transistors Q1 and Q2. In this case, a light source corresponding to the photoelectric converters PC1 to PCn may be provided to form a photocoupler.

As described above, since the switch circuit is a switch circuit in which two field-effect transistors Q1 and Q2 are connected in series, a non-contact configuration, high-speed operation is possible, and low on-resistance results in noise. Without any occurrence of load LD1
On / off of the operation of the LDn can be controlled at high speed, and a configuration with low power loss can be realized.

FIG. 2 is an explanatory view of a second embodiment of the present invention, wherein Q1 and Q2 are field effect transistors, PW is a power supply, LD is a load, PC is a photoelectric converter, C is a capacitor,
Q3 is a transistor, R1 is a resistor, Cin is an input capacitance of the field effect transistors Q1 and Q2, and cont is a control signal. The light source for the photoelectric converter PC and the built-in diodes D1, D2 of the field-effect transistors Q1, Q2.
Are not shown.

It is conceivable to control the on / off of the gate voltage of the field effect transistors Q1 and Q2 by turning on / off the light incident on the photoelectric converter PC from the light source. Converter P with semiconductor element
Since the operating speed of C is slow, it is difficult to rapidly raise the gate voltage in response to the control signal. Therefore, as described above, the capacitor C is charged with the voltage converted by the photoelectric converter PC to be used as a power supply for the control circuit, and the on / off of the gate voltage is controlled at high speed by the transistor Q3.

For example, when the control signal cont is set to a high level ("1"), the transistor Q3 is turned on,
The terminal voltage of the capacitor C is applied as a gate voltage to the gates of the field effect transistors Q1 and Q2, and the input capacitance Ci
When n is rapidly charged and its terminal voltage exceeds the threshold value, the field effect transistors Q1 and Q2 are turned on. As a result, the operating power is supplied from the power supply PW to the load LD, and the load LD starts operating.

The control signal cont is set to low level ("0").
Then, the transistor Q3 is turned off, and the input capacitance Ci of the field effect transistors Q1 and Q2 via the resistor R1.
When the electric charge accumulated in n is discharged and the gate potential falls below the threshold, the field effect transistors Q1 and Q2 are turned off, the operating power supplied from the power supply PW to the load LD is cut off, and the load LD stops operating. Stop.

FIGS. 3A and 3B are explanatory diagrams of the operation. FIG. 3A shows the control signal cont, and FIG. 3B shows the field effect transistor Q.
1 shows the drain-source voltage of Q2. Note that Vp
Is the power supply voltage. For example, as shown in (a), when the control signal cont is set to "1", the transistor Q3 is turned on at a high speed, and the terminal voltage of the capacitor C is applied to the gates of the field effect transistors Q1 and Q2. Q1 and Q2 can be turned on at high speed. Therefore, the drain-source voltages of the field effect transistors Q1 and Q2 rapidly become zero from the power supply voltage Vp.

When the control signal cont is set to "0", the transistor Q3 is turned off, and the resistance R1
Via the input capacitance C of the field effect transistors Q1 and Q2
The accumulated charge of in is discharged. At that time, the gate voltages of the field effect transistors Q1 and Q2 decrease according to the time constant including the resistance R1, and the drain-source voltage rises to the power supply voltage Vp with a sloped characteristic as shown in FIG. FIG.
The configuration of the control circuit shown in FIG.
By the high-speed turning on of Q2, an operating voltage can be applied so that the timing of the load LD is not delayed.

FIG. 4 is an explanatory diagram of the third embodiment of the present invention. The same reference numerals as those in FIG. 2 denote the same parts, and Q3 is the first.
In this case, the control signal on is applied to the base of the first transistor Q3, and the control signal off is applied to the base of the second transistor Q4. That is, the control signal on of “1” is applied to the base of the first transistor Q3 to turn on the transistor Q3,
The terminal voltage of the capacitor C is changed to the field-effect transistor Q1,
Turn on by applying to the gate of Q2. At this time, the control signal off is set to "0" to turn off the second transistor Q4.

Next, the control signal on is set to "0" and the control signal of
If f is “1”, the first transistor Q3 is off,
The second transistor Q4 is turned on, and the charge stored in the input capacitance Cin of the field effect transistors Q1 and Q2 is transferred to the second transistor Q4.
, And the turn-off of the field effect transistors Q1 and Q2 can be accelerated. Accordingly, high-speed turning on and off of the operating voltage applied to the load LD from the power supply PW can be realized.

In this case, the first transistor Q3 and the second transistor Q3
It is necessary to set the timing of the control signals on and off so that the transistor Q4 does not turn on at the same time. For example, the control signal o shown in (c) and (d) of FIG.
Guard times t1 and t2 are set between the rise and fall of n and off, respectively, and t1 = t2 can also be set. Thus, simultaneous turning on of the transistors Q3 and Q4 can be prevented. The drain-source voltages of the field effect transistors Q1 and Q2 are as shown in FIG.

FIG. 5 is an explanatory view of a fourth embodiment of the present invention. The same reference numerals as in FIG.
Denotes an npn-type pnp-complementary transistor, Q7 denotes a pnp-type control transistor, and R2 denotes a resistor. The gates of the field effect transistors Q1 and Q2 are connected to the commonly connected emitters of the complementary transistors Q5 and Q6, and the collector of the control transistor Q7 is connected to the complementary transistor Q5.
5, Connect to the base of Q6.

Therefore, when the control signal cont is set to "1", the control transistor Q7 is turned off, one of the complementary transistors Q5 and Q6 is turned on, and the other transistor Q6 is turned off. Thereby, the terminal voltage of the capacitor C is applied to the gates of the field effect transistors Q1 and Q2 via the transistor Q5, the field effect transistors Q1 and Q2 are turned on, and the operating power is supplied from the power supply PW to the load LD.

When the control signal cont is set to "0", the control transistor Q7 is turned on, one of the complementary transistors Q5 is turned off and the other transistor Q6 is turned on, and the input capacitance Cin of the field effect transistors Q1 and Q2 is turned on. Is rapidly discharged, the field-effect transistors Q1 and Q2 are turned off, and the load LD
Is shut off.

Assuming that the control signal cont in this case is as shown in FIG. 2 (f), the drain-source voltage of the field effect transistor is as shown in FIG. 2 (g). That is, the field effect transistors Q1 and Q2 are turned on at high speed by the control signal cont of "1", the voltage between the drain and the source becomes zero, and the control signal cont of "0"
As a result, the field effect transistors Q1 and Q2 are turned off at high speed, and the voltage between the drain and the source becomes the voltage Vp of the power supply PW.
Becomes

FIG. 6 is an explanatory view of the fifth embodiment of the present invention. The same reference numerals as those in FIG.
Is a diode. The diodes D3 and D4 connected to the emitters of the complementary transistors Q5 and Q6 use the forward voltage drop as a bias voltage. And the emitter potential of the transistor Q5 is reduced so that the transistor Q5 is not turned on before the transistor Q6 is turned off. The on / off control of the field effect transistors Q1 and Q2 is the same as that shown in FIG.

[0027]

As described above, according to the present invention, the power supply P
2 connected in series between W and loads LD1 to LDn such that built-in diodes D1 and D2 have opposite polarities, respectively.
A plurality of field-effect transistors Q1 and Q2, and control circuits CON1 to CONn for applying a control voltage to the gates of the two field-effect transistors Q1 and Q2 to turn on and off the field-effect transistors Q1 and Q2. The present invention can be applied to the case where the power supply PW is an AC power supply or a DC power supply. When driving various loads intermittently, there is an advantage that ON / OFF of the operating voltage can be controlled at high speed and with low loss. . Also, the photoelectric converter PC is connected to the control circuits CON1 to CO
By using a power source of Nn, it is possible to reduce the size and weight. Further, by using the photoelectric converter PC as a power source and controlling the on / off of the gate voltages of the field effect transistors Q1 and Q2 at high speed by transistors, there is an advantage that the on / off of the field effect transistors Q1 and Q2 can be accelerated. is there.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a second embodiment of the present invention.

FIG. 3 is an operation explanatory diagram.

FIG. 4 is an explanatory diagram of a third embodiment of the present invention.

FIG. 5 is an explanatory diagram of a fourth embodiment of the present invention.

FIG. 6 is an explanatory diagram of a fifth embodiment of the present invention.

FIG. 7 is an explanatory diagram of a conventional example.

[Explanation of symbols]

 Q1, Q2 Field effect transistor D1, D2 Built-in diode PW power supply LD1 to LDn Load CON1 to CONn Control circuit cont1 to conn Control signal C1 to Cn Capacitor PC1 to PCn Photoelectric converter P Light source

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference)

Claims (4)

[Claims] 1. Two field effect transistors connected in series between a power supply and a load such that built-in diodes have opposite polarities, and a control voltage is applied to gates of the two field effect transistors. And a control circuit for turning on and off the field effect transistor. 2. The switch circuit according to claim 1, wherein the control circuit includes a transistor for applying an operating voltage converted by a photoelectric converter to a gate of the field-effect transistor according to a control signal. 3. The control circuit includes: a first transistor for applying an operating voltage converted by a photoelectric converter to a gate of the field-effect transistor according to an ON control signal; and a gate of the field-effect transistor according to an OFF control signal. 2. The switch circuit according to claim 1, further comprising: a second transistor for discharging the charge stored in the input capacitor. 4. The control circuit includes a control transistor for applying a control signal to a base, and a complementary transistor controlled by the control transistor, and supplies an operating voltage converted by a photoelectric converter to one of the complementary transistors. The field effect transistor is applied to the gate of the field effect transistor via the transistor of the conductivity type, and the charge connected to the input capacitance of the field effect transistor is discharged via the transistor of the other conductivity type. The switch circuit according to claim 1, wherein