JPH05145392A - Stationary auxiliary relay circuit - Google Patents

Abstract

PURPOSE:To set the operating time and the restoration time and their quantity relation optionally by providing a transistor(TR) and a diode between an output element of a photocoupler and an output semiconductor element. CONSTITUTION:An operating time TOP depends on resistance values R8, R9 of resistors 8, 9 and a capacitance C7 of a capacitor 7 and is not depending on an input capacitance CSS of a FET4. On the other hand, a returning time TRE depends on the resistance values R8, R9 and the capacitance CSS and is not depending on the C7. Thus, the times TOP, TRE depend respectively different capacitance values C7, CSS and the circuit configuration for TOP >=TRE and the circuit configuration for TOP<TRE are set optionally. Thus, the operating time and the return time are set to optional times requested by a relay circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a static auxiliary relay circuit that electrically insulates an input and an output from each other with an optical element and obtains an on / off output to an output stage semiconductor element.

[0002]

2. Description of the Related Art FIG. 2 shows a conventional circuit diagram. The on / off input signal is applied to the input element of the photocoupler 2 through the current limiting resistor 1. Output element voltage V of photo coupler 2
_in is applied to the gate of the FET 4 which becomes an output element through the resistor 3. A parallel circuit of a resistor 5 and a capacitor 6 as a time constant circuit is provided between the gate and source of the FET 4.

In the above structure, the operating time T at which the FET 4 turns on and off with respect to the turning on and off of the input signal.
_OP and recovery time T _RE are as follows.

T _OP = − (C ₆ + C _SS ) × (R ₃ // R ₅ ) ln (1-V ₂ / V ₁ ) where V ₁ = V _sn (R ₃ / (R ₂ + R ₃ )) C _6: capacitance of the capacitor 6 C _SS: input capacitance R ₃ and FET: resistance 3 of the resistance value R _5: resistor 5 of resistance V _2: operating voltage (threshold) of _{FET T RE = - (C 6} + C _SS ) × R ₅ × ln (V ₃ / V ₁ ) where V _{3 is} the recovery voltage of the FET

[0005]

In the conventional auxiliary relay circuit, since the photocoupler 2 has a small output capacity, it is necessary to set the resistance values R ₃ and R ₅ of the resistors 3 and 5 to R ₃ << R _5. .. Therefore, the operation time T _OP and the recovery time T _RE are generally T _OP <T _RE, and there is a problem that T _OP > T _RE cannot be satisfied.

Further, in order to obtain a short operation time T _OP , the capacitance C ₆ of the capacitor ₆ is made small. However, when this capacitance becomes small, the desired characteristic is obtained due to the variation of the input capacitance C _SS of the FET 4. Design becomes difficult. vice versa,
If the resistance value R 3 of the resistor ₃ is made small and the capacitance C ₆ is made sufficiently larger than C _SS , the recovery time T _RE becomes large and T
It becomes _OP << T _RE, and it becomes impossible to obtain the desired product during the recovery time.

An object of the present invention is to provide a static auxiliary relay circuit in which the magnitude relation between the operating time and the recovery time and the value setting are arbitrary.

[0008]

In order to solve the above-mentioned problems, the present invention provides a photocoupler for electrically isolating an ON / OFF input signal, a capacitor provided in parallel with an output element of the photocoupler, and a first capacitor. A parallel circuit with a resistor and a second resistor connected in series with the parallel circuit, and a connection point between the first resistor and the second resistor provided between the output element of the photocoupler and the gate of the output semiconductor element. It is characterized by comprising a transistor which is turned on by a voltage to turn off the semiconductor element, and a diode which is provided between a collector and an emitter of the transistor and which forms a current path for turning on the semiconductor element.

[0009]

According to the present invention, by providing a transistor between the output element of the photocoupler and the output semiconductor element,
The operation time for turning off the semiconductor element depends on the time until the transistor turns on, that is, the time constant due to the capacitor and the first and second resistors.

Further, by providing a diode between the collector and the emitter of the transistor, the recovery time for turning on the semiconductor element depends on the input capacitance of the semiconductor element or the capacitance of the external capacitor and the time constant of the first and second resistors. ..

[0011]

1 is a circuit diagram showing an embodiment of the present invention, and the same elements as those in FIG. 2 are designated by the same reference numerals. Photo coupler 2
In parallel with the output element of, the parallel circuit of the capacitor 7 and the resistor 8 and the resistor 9 in series therewith are provided. Further, between the output element of the photocoupler 2 and the gate of the FET 4, the emitter and collector of a PNP transistor 10 serving as a switching means are connected, and the base of the transistor 10 is a resistor 8.
Is connected to the connection point of the resistor 9 and the resistor 9. Further, the diode 11 is provided in the forward direction from the collector to the emitter of the transistor 10 to form a current path for turning on the FET.

In this embodiment, the operating time T _OP is determined by the time until the transistor 10 is turned on, that is, the resistance values R ₈ and R 9 of the resistors ₈ and ₉ and the capacitance C _{7 of the} capacitor 7, and the input capacitance C of the FET 4 is determined. _Does not depend on _SS . In this operation time T _OP , the input impedance R _{4 of the} FET ₄ is R ₄ >
When> R ₈ + R ₉ , the following equation is obtained.

T _OP = −C ₇ × (R ₈ // R ₉ ) × ln (1-V _BE / V ₁ ), where V ₁ = V _in (R ₈ / (R ₈ + R ₉ )) V _BE : Base-emitter voltage of the transistor 10 On the other hand, the recovery time T _RE is the time until the diode 11 becomes conductive and the charge of the input capacitance C _SS is discharged, that is, the resistance values R ₈ and R 9 of the resistors ₈ and ₉ and the input capacitance. It depends on C _SS and does not depend on the capacitance C _{7 of the} capacitor 7. This return time T
_RE becomes T _RE = −C _SS × (R ₈ + R ₉ ) × ln (V ₃ / V ₁ ).

Therefore, according to this embodiment, the operating time T _OP
And the recovery time T _RE can be determined by different capacitances C ₇ and C _SS , respectively, and can be arbitrarily set in the circuit configuration in which T _OP > = T _RE and the configuration in T _OP <T _RE .

Further, since the operating time T _OP depends on the capacity of the capacitor 7, it can be set reliably and in a wide range from short time to long time without being affected by the variation of the input capacity C _SS of the FET 4.

Since the recovery time T _RE depends on the input capacitance C _{SS of the} FET 4, its variation may deviate from the design value. However, an external capacitor is added between the gate and source of the FET 4 to input it. It is possible to suppress the influence of variations in the capacitance C _SS .

In the above-mentioned embodiment, the case where the FET is used as the output element is shown. However, this can be replaced with another semiconductor element such as a transistor or a thyristor to obtain the same effect.

[0018]

As described above, according to the present invention, the off transistor and the on diode are provided between the output element of the photocoupler and the gate of the output semiconductor element, and the capacitors for both the output element side and the semiconductor element side are provided. Since the operating time and the recovery time can be set individually depending on the capacity, there is an effect that the operating time and the recovery time can be set to arbitrary times required for the relay circuit.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment.

FIG. 2 is a conventional circuit diagram.

[Explanation of symbols]

2 ... Photo coupler, 4 ... FET, 7 ... Capacitor, 8,
9 ... Resistor, 10 ... Transistor, 11 ... Diode.

Claims (1)

[Claims] 1. A photocoupler that electrically insulates an ON / OFF input signal, a parallel circuit of a capacitor and a first resistor provided in parallel with an output element of the photocoupler, and a first circuit connected in series to the parallel circuit. And a transistor provided between the output element of the photocoupler and the gate of the output semiconductor element to turn on the semiconductor element by a connection point voltage between the first resistor and the second resistor, and the transistor. A diode provided between the collector and the emitter of the diode to form a current path for turning on the semiconductor element, and a static auxiliary relay circuit.