JPH08298447A - Semiconductor relay - Google Patents

Abstract

PURPOSE: To obtain a semiconductor relay in which a delay time at switching is extended without extending a rise time at switching. CONSTITUTION: A photovoltaic diode array 2a is coupled optically with a light emitting element 1a comprising a light emitting diode and the photovoltaic diode array 2a is connected between a gate and a source of an output MOSFET 3a in the n-channel enhancement mode via a resistor 5a. A gate of a drive transistor(TR) 4a connects to a connecting point between the photovoltaic array 2a and the resistor 5a and the source of the TR 4a is connected to a source of the output MOSFET 3a, and the drain of the TR 4a is connected to a gate of the output MOSFET 3a. A MOSFET 6 in the p-channel depletion mode is connected across the resistor 5a and the gate of the MOSFET 6 connects to the gate of the output MOSFET 3a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor relay, and more particularly, it converts an input signal into an optical signal by a light emitting element, and converts the optical signal into an electrical signal by a photovoltaic diode array optically coupled to the light emitting element. And an optical coupling type semiconductor relay configured to drive the output MOSFET by the electric signal.

[0002]

2. Description of the Related Art A conventional semiconductor relay is shown in FIG.
As shown in (b), the first light emitting element 1a and the second light emitting element 1a, which are light emitting diodes that are turned on and off in response to an input signal.
Light emitting element 1b, the first photovoltaic diode array 2a and the second photovoltaic diode array 2b optically coupled to the respective light emitting elements 1a, 1b, and the photovoltaic elements of the respective photovoltaic diode arrays 2a, 2b. A first output MOSFET 3a and a second output MO that are turned on / off by electric power, respectively.
SFET 3b and each photovoltaic diode array 2a, 2
A resistor 5 as an impedance element connected between the cathode side of b and each of the output MOSFETs 3a and 3b.
a and 5b. Further, the sources of the first driving transistor 4a and the second driving transistor 4b are connected to the sources of the output MOSFETs 3a and 3b, respectively, and the drains of the driving transistors 4a and 4b are connected to the output MOSFET 3a, respectively. , 3b are connected to the gate. Here, the first output MOSFET 3a
Is in the enhancement mode (normally off type), and the drain current does not flow when the gate voltage is zero (that is, it is in the off state). On the other hand, the second output MO
The SFET 3b is in the depletion mode (normally on type), and the drain current flows even when the gate voltage is zero (that is, it is in the on state).

The operation of the semiconductor relay will be described below. First, the first output MOSFET 3a is
Since the light emitting element 1a is in the off state when the light emitting element 1a is off, it is between the relay output terminals 8A and 8B (that is, the first output MOS).
The area between the drain and the source of the FET 3a) is in a high impedance state. Input terminals 7A at both ends of the first light emitting element 1a,
Voltage source (not shown) or current source (not shown) between 7B
And the current is passed in the forward direction of the first light emitting element 1a, the first light emitting element 1a emits light (emits an optical signal).

When the first light emitting element 1a emits an optical signal,
The first photovoltaic diode array 2a receives the optical signal and generates photovoltaics in which the anode side of the first photovoltaic diode array 2 is positive. This photovoltaic is the first
Is applied between the gate (G) and the source (S) of the first output MOSFET 3a via the resistor 5a, and at the same time, the n-channel depletion mode field effect transistor (FET) via the first resistor 5a. Is applied between the drain (D) and the source of the first driving transistor 4a.

Then, due to the photovoltaic power, the current for charging the gate capacitance of the first output MOSFET 3a and the current flowing from the drain to the source of the first driving transistor 4a pass through the first resistor 5a. Flows as a photocurrent through. Therefore, the gate of the first driving transistor 4a is biased to a negative voltage with respect to the source by the voltage across the first resistor 5a. This bias voltage causes a high impedance state between the drain and source of the first driving transistor 4a, so that the first output MOSF
The gate capacitance of ET3a is efficiently charged.

By the above operation, the relay output terminal 8A,
Since the high impedance state changes to the low impedance state during 8B, the first output MOSFET 3a is inverted from the off state to the on state. That is, the first output MO
The SFET 3a functions as a normally open contact. Further, since the second output MOSFET 3b is in the ON state when the second light emitting element 1b is turned off, it is between the relay output terminals 8C and 8D (that is, the drain of the second output MOSFET 3b.
(Between sources) is in a low impedance state.

When a current is passed in the forward direction of the second light emitting element 1b, the second light emitting element 1b emits an optical signal, and the second photovoltaic diode array 2b receives the optical signal to generate a second signal.
The photovoltaic diode array 2b generates a positive photovoltaic voltage on the anode side. This photovoltaic power is supplied to the second output MO through the second resistor 5b as an impedance element.
At the same time as being applied between the source and gate of the SFET 3b, it is applied between the drain and source of the second driving transistor 4b which is an n-channel depletion mode FET through the second resistor 5b.

Then, the photoelectromotive force causes the source potential of the second output MOSFET 3b to be higher than the gate, and the voltage across the second resistor 5b causes the gate of the second driving transistor 4b to be the source. Biased to a negative voltage. This bias voltage causes a high impedance state between the drain and source of the second driving transistor 4b, so that the second output MOSFET 3b is formed.
When the source potential with respect to the gate of becomes higher than the threshold voltage, the second output MOSFET 3b is turned off.

By the above operation, the relay output terminal 8C,
During 8D, the low impedance state changes to the high impedance state. That is, the second output MOSFET 3b functions as a normally closed contact. On the other hand, when the input current between the input terminals 7A and 7B is cut off, the first light emitting element 1a
Does not emit light (since it does not emit an optical signal),
There is no photovoltaic power in the first photovoltaic diode array 2a, and there is no photocurrent flowing through the first resistor 5. Therefore, the bias voltage that puts the first driving transistor 4a in the high impedance state disappears,
Driving transistor 4a returns to the ON state. And
The first output MO is supplied via the driving transistor 4a.
The electric charge accumulated in the gate capacitance of the SFET 3a is discharged, and the relay output terminals 8A and 8B return to the high impedance state.

That is, the circuit of FIG. 4 (a) functions as a normally closed contact, and the circuit of FIG. 4 (b) functions as a normally open contact. Therefore, by using both contacts, one contact side is in a conducting state (Mak).
It is possible to configure a break-before-make contact (BBM contact) in which the other contact side is in a non-conducting state before becoming e). This block diagram is shown in FIG. In FIG. 5, a semiconductor relay A composed of the circuits of FIGS.
Is symbolically described by the first light emitting element 1a and the second light emitting element 1b and the contacts 9a and 9b. here,
The contacts 9a and 9b are the photovoltaic diode arrays 2a and 2b of the circuits of FIGS. 4A and 4B, and the output MOSFs.
ET3a, 3b and driving transistors 4a, 4b
And resistors 5a and 5b.

In the circuit of FIG. 5, the semiconductor relay A is connected to the BBM.
In order to operate as a point, it is controlled outside the semiconductor relay A.
The control circuit B is provided. Control circuit B emits first light
Resistor R connected in series with element 1a₁And the second light emitting element
Resistor R connected in series with 1b ₂, R₃And the resistance R₃Average
Column-connected capacitors C₁Have and. Also, each light emission
An npn-type transistor is provided at each connection point between the elements 1a and 1b.
Ta Tr₁Is connected to the collector (C) of the transistor T
r₁The base R (B) has a resistance R_FourConnected,
Star Tr₁The emitter (E) of is grounded.

The operation of the above circuit will be described below with reference to FIG. As shown in FIG. 6A, when the control signal to the base of Tr ₁ becomes High level and the transistor Tr ₁ is turned on, the second light emitting element 1b immediately emits light, but the capacitor C ₁ is not charged. The first light emitting element 1a until
A sufficient current does not flow to the first light emitting element 1a, and the first light emitting element 1a emits light later than the second light emitting element 1b. That is, FIG.
6 (c) after the contact 7b is turned off as shown in FIG. 6 (b).
As described above, the control circuit B is configured so that the contact 9a is turned on and the contact 9a and the contact 9b are simultaneously turned off. That is, the first light emitting element 1a
By causing the second light emitting element 1b to emit light with a delay, the normally open contact 9a is turned on and then the normally open contact 9a is turned on, thereby operating as a BBM contact.

[0013]

However, according to the above structure, in order to perform the operation as the BBM contact,
Since it is necessary to add a control circuit B having a capacitor, a resistor, a transistor, etc. to the outside of the semiconductor relay A as an external circuit, there has been a problem that the number of parts at the time of mounting increases and the mounting area increases.

The present invention has been made in view of the above reasons, and the object of the invention of claim 1 is not to affect other characteristics and to increase the rising time at the time of switching, An object of the present invention is to provide a semiconductor relay that can prolong the delay time during switching. It is an object of the invention of claim 2 to provide a semiconductor relay capable of forming a BBM contact without using an external circuit.

An object of the invention of claim 3 is to provide a semiconductor relay that can be operated as a multi-pole BBM contact relay.

[0016]

In order to achieve the above-mentioned object, a light-emitting element that generates an optical signal in response to an input signal, and a photovoltaic element that receives the optical signal to generate a photovoltaic power are provided. A photovoltaic diode array that is generated, an impedance element that is connected in series to the photovoltaic diode array, and the photovoltaic element is applied between the gate and the source through the impedance element, Enhancement mode output MOSFET that changes to a second impedance state, and the output MOS
A control electrode is connected between the gate and source of the FET, and a connection point between the impedance element and the photovoltaic diode array is connected so that a high impedance state is generated when the photovoltaic power is generated and the photovoltaic power is generated. In a semiconductor relay having a driving transistor that is in a low impedance state when disappearing, a depletion mode MOSFET is connected in parallel to the impedance element, and the gate and the source of the MOSFET are respectively the gate and the source of the output MOSFET, respectively. It is characterized by being connected to.

According to a second aspect of the present invention, a light emitting element that generates an optical signal in response to an input signal, a first photovoltaic diode array that receives the optical signal and generates a photovoltaic power, and the first photovoltaic diode array are provided. A first impedance element connected in series to one photovoltaic diode array;
Enhancement mode first output MOSFET that is applied between the gate and source via the impedance element and changes from the first impedance state to the second impedance state, and the gate and source of the first output MOSFET A control electrode is connected to the first impedance element and a connection point between the first photovoltaic element array and the first photovoltaic diode array, and a control electrode is connected to the high impedance state at the time of generation of the photovoltaic force. A first driving transistor that is in a low impedance state when power is lost, and a first depletion mode MOSFET is connected in parallel to the first impedance element, and a gate and a source of the first MOSFET are connected to the first MOSFET. Is connected to the gate and source of the first output MOSFET, respectively. The conductor relay section includes a second photovoltaic diode array that receives an optical signal generated by the light emitting element of the first semiconductor relay section and generates a photovoltaic force, and the second photovoltaic diode array. Second connected in series
Second impedance element and the second output MOSFET in the depletion mode in which the photovoltaic is applied between the gate and the source through the second impedance element to change from the third impedance state to the fourth impedance state. Is connected between the gate and source of the second output MOSFET, and a control electrode is connected to a connection point between the second impedance element and the second photovoltaic diode array. It is characterized in that it is combined with a second semiconductor relay section having a second driving transistor which is in a high impedance state when electric power is generated and is in a low impedance state when the photovoltaic power disappears.

The invention of claim 3 is characterized in that a plurality of the semiconductor relays are provided on the same substrate.

[0019]

According to the structure of the present invention, the depletion mode MOSF is arranged in parallel with the impedance element.
Since ET is connected, and the gate and the source of the MOSFET are connected to the gate and the source of the output MOSFET, respectively, until the output MOSFET starts to turn on when a photovoltaic power is generated in the photovoltaic diode array. Is a MOSF between the gate and source of the driving transistor.
The driving transistor is clamped to ET and the driving transistor is turned on, the current to the gate capacitance of the output MOSFET decreases, and the time for charging the gate capacitance can be lengthened. After the output MOSFET starts to turn on, the depletion mode MOSFET is turned off, and the driving transistor is biased by the impedance element to be turned off.
The gate capacitance of the FET is quickly charged.

According to the second aspect of the present invention, the semiconductor relay unit 1 is used as the normally open contact and the semiconductor relay unit 2 is used as the normally closed contact, whereby the delay time when the normally open contact is turned on is lengthened. Thus, it can be operated as a semiconductor relay having a break-before-make contact in which the normally open contact is turned off and then the normally open contact is turned on. According to the configuration of the invention of claim 3, since a plurality of semiconductor relays of claim 2 are provided on the same substrate, it is possible to operate as a multi-pole break-before-make contact.

[0021]

The present invention will be described below with reference to examples. In the semiconductor relay of the present embodiment, as shown in FIG. 1, a photovoltaic diode array 2a is optically coupled to a light emitting element 1a composed of a light emitting diode. Also, output MOS
The photovoltaic diode array 2a is connected between the gate and source of the FET 3a through a resistor 5a as an impedance element. The output MOSFET 3a is in the n-channel enhancement mode. The driving transistor 4a is in the n-channel depletion mode, and its gate has the photovoltaic diode array 2a.
And a resistor 5a. Further, the source of the driving transistor 4a is connected to the source of the output MOSFET 3a, and the drain of the driving transistor 4a is connected to the gate of the output MOSFET 3a. A p-channel depletion mode MOSFET 6 is connected to both ends of the resistor 5a, and
The gate of ET6 is connected to the gate of the output MOSFET 3a.

The operation of this embodiment will be described below.
When an input current flows in the forward direction of the light emitting element 1a, the light emitting element 1a generates an optical signal, and this optical signal generates a photovoltaic power at both ends of the photovoltaic diode array 2a. This photovoltaic force is applied between the gate and source of the output MOSFET 3a via the resistor 5a, and at the same time, flows through the driving transistor 4a. Then, the current for charging the gate capacitance of the output MOSFET 3a and the current flowing through the driving transistor 4a flow through the resistor 5a.

At this time, if the MOSFET 6 is not present, the gate of the driving transistor 4a is negatively biased by the voltage between the terminals of the resistor 5a as described in the conventional example, and the driving transistor 4a instantaneously becomes a high impedance state, and the output The gate capacitance of the power MOSFET 3a is efficiently charged. However, in this embodiment, the MOSFET 6
Since the gate and source of the driving transistor 4a are clamped (shorted) by the driving transistor 4a, the driving transistor 4a
Remains in a low impedance state. Therefore, the charging current of the gate capacitance of the output MOSFET 3a decreases, and the charging time of the gate capacitance becomes longer.

Output threshold voltage of MOSFET 6
If the gate-source voltage when the FET 3a starts to turn on is set, the MOSFET 6 turns off when the output MOSFET 3a starts to turn on, and the gate of the driving transistor 4a is negatively biased by the voltage across the resistor 5a terminals. Then, the driving transistor 4a is instantly brought into a high impedance state, the gate capacitance of the output MOSFET 3a is efficiently charged, and the output MOSFET 3a is turned on.

That is, the delay time until the output MOSFET 3a starts to be turned on is increased so that the output M
When the OSFET 3a starts to turn on, it quickly turns on. In the semiconductor relay of this embodiment, a case will be described in which a square wave pulse signal as shown in FIG. 2A is input to the light emitting element 1a. Below is the delay time from the rise of the input signal to the start of turning on the output MOSFET 3a, that is, the time until the gate-source voltage of the output MOSFET 3a reaches the threshold voltage from Td ₁ , Td ₂ , Td. ₃ , output MOSFET 3a
Rise time for the gate-source voltage of the transistor to reach the saturation level (ON state) from the threshold voltage is Tr ₁ , Tr
_2, Tr _3, represents the operation time a combination of the delay time and rise time as _{T on1, T on2, T on3} .

For example, if there is no MOSFET 6,
The output signals of the power MOSFET 3a are two points in FIG.
As indicated by the chain line, Td₁Start to turn on with delay time of
, Tr₁Turned on at the rising time of
Time T_on1). Here, for example, the photovoltaic diode
Gate array of output MOSFET 3a
Insert a resistor (not shown) in the path to pass the charging current to the capacitance.
Then, if the charging current is limited, as shown in FIG.
Delay time Td₂Can be long, but a single-dot chain
As shown by the line, the rise time Tr₂Even longer, dynamic
Work time T_on2Will be longer than necessary. But
However, connect the MOSFET 6 to both ends of the resistor 5a.
As shown by the solid line in Fig. 2 (b),
Time Tr ₃To Tr₁When delaying without making it longer
Interval Td₃Td₁It can be longer.

As described above, the MOSF is provided at both ends of the resistor 5a.
By connecting the ET6 and applying the gate-source voltage of the output MOSFET 3a between the gate and the source of the MOSFET 6, the rise time at the time of switching ON without affecting other characteristics. The delay time at the time of switching on can be lengthened without lengthening the length.

Therefore, the semiconductor relay is a normally open contact, and the semiconductor relay shown in FIG. 3 (a) shown in the conventional example is a normally closed contact, and a circuit as shown in FIG. 3 is constructed to share an input signal. (Input an input signal to the input terminals 7A and 7B)
As a result, it is possible to operate as a semiconductor relay having a BBM contact in which the normally open contact turns on after the normally closed contact turns off as shown in FIG. 6 without the control circuit B as shown in FIG. 5 of the conventional example. .

Further, by forming a plurality of semiconductor relays having the BBM contacts on the same substrate, a multi-pole BBM is formed.
It can be operated as a contact relay.

[0030]

According to the structure of the invention of claim 1, the depletion mode M is arranged in parallel with the impedance element.
Since the OSFET is connected and the gate and the source of the MOSFET are connected to the gate and the source of the output MOSFET, respectively, until the output MOSFET starts to turn on when the photovoltaic power is generated in the photovoltaic diode array. Is M between the gate and source of the driving transistor.
The driving transistor is clamped by the OSFET to be turned on, the current to the gate capacitance of the output MOSFET is reduced, and the time for charging the gate capacitance can be lengthened. After starting to turn on, depletion mode MOSFET
Is turned off and the driving transistor is biased by the impedance element to be turned off, so that the gate capacitance of the output MOSFET can be charged quickly.

According to the second aspect of the present invention, the semiconductor relay unit 1 is used as the normally open contact and the semiconductor relay unit 2 is used as the normally closed contact, whereby the delay time when the normally open contact is turned on is lengthened. As a result, the normally-closed contact is turned off, and then the normally-open contact is turned on. Thus, the semiconductor relay having the break-before-make contact can be operated.

According to the configuration of the invention of claim 3, since a plurality of the semiconductor relays are provided on the same substrate, there is an effect that it can be operated as a multi-pole break-before-make contact.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

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

FIG. 3 is a circuit diagram showing another embodiment of the present invention.

FIG. 4 is a circuit diagram showing a conventional example.

FIG. 5 is a circuit diagram showing a conventional example.

FIG. 6 is an operation explanatory diagram of a conventional example.

[Explanation of symbols]

 1a Light emitting element 2a Photovoltaic diode array 3a Output MOSFET 4a Driving transistor 5a Resistor 6 MOSFET 7A, 7B Input terminal 8A, 8B Output terminal

Claims (3)

[Claims] 1. A light-emitting element that generates an optical signal in response to an input signal, a photovoltaic diode array that receives the optical signal and generates photovoltaic power, and is connected in series to the photovoltaic diode array. An impedance element, an enhancement mode output MOSFET in which the photovoltaic power is applied between the gate and the source via the impedance element to change from the first impedance state to the second impedance state, and the output MOSFET A control electrode is connected between the gate and the source of the MOSFET, and a connection point between the impedance element and the photovoltaic diode array is brought into a high impedance state when the photovoltaic power is generated. In a semiconductor relay equipped with a driving transistor that becomes a low impedance state when the , A depletion mode MOSFET is connected in parallel to the impedance element, and a gate and a source of the MOSFET are connected to the output MOS.
A semiconductor relay characterized by being connected to the gate and source of an FET. 2. A light emitting element which generates an optical signal in response to an input signal, a first photovoltaic diode array which receives the optical signal and generates a photovoltaic power, and the first photovoltaic power. A first impedance element connected in series to the diode array, and the photovoltaic power is applied between the gate and the source through the first impedance element to change from the first impedance state to the second impedance state. Enhancement mode first output MOSFET
Is connected between the gate and the source of the first output MOSFET, and a control electrode is connected to a connection point between the first impedance element and the first photovoltaic diode array. A first driving transistor that is in a high impedance state when electric power is generated and is in a low impedance state when the photovoltaic power disappears, and connects a first MOSFET in a depletion mode in parallel to the first impedance element. And the first
Of the first output MOSFET is connected to the gate and the source of the first MOSFET, respectively.
A semiconductor relay unit for receiving a light signal generated by the light emitting element of the first semiconductor relay unit to generate a photoelectromotive force;
A photovoltaic diode array, a second impedance element connected in series to the second photovoltaic diode array, and the photovoltaic power applied between the gate and the source via the second impedance element. The second output MOSFET in the depletion mode in which the third impedance state is changed to the fourth impedance state
Is connected between the gate and source of the second output MOSFET, and a control electrode is connected to a connection point between the second impedance element and the second photovoltaic diode array. A semiconductor relay characterized by being combined with a second semiconductor relay section comprising a second driving transistor which is in a high impedance state when power is generated and is in a low impedance state when the photovoltaic power disappears. 3. A semiconductor relay comprising a plurality of semiconductor relays according to claim 2 provided on the same substrate.