JPH04332217A - Long life photo mos relay - Google Patents

Abstract

PURPOSE:To realize a photo MOS relay with a long service life even when it is used for long time in 'ON' state with respect to a photo MOS relay. CONSTITUTION:The first light emitting diode 10, the first photo electromotive diode 20 that generates an electromotive force from the light output of the first light emitting diode 10, and photo MOS relay 1 consisting of the first and second MOS type field effect transistors 30 and 40 that are turned 'ON' and 'OFF' by the output of the first photoelectromotive diode 20, wherein are installed the second photoelectromotive diode 60 that generates an electromotive force by using the light output from the second light emitting diode 50 connected in the direction opposite to the first photoelectromotive diode 20, and a state holding means 70 that holds an 'ON' state by using the output of the photoelectromotive diode 20 and that holds an 'OFF' state by using the output of the second photoelectromotive diode 60 so that only when the 'ON' or 'OFF' state occurs, the first or second light emitting diode 10 or 50 is driven by single emitting pulse current.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photomos relay. Photomos relays are beginning to be used as an alternative to mechanical relays. For example, in monitoring equipment, etc.
Until now, mechanical relays have been used to completely disconnect the input and output signals from ground.

However, since mechanical relays operate mechanically, they have a physically finite lifespan, and
Contacts that turn electrical signals on and off can sometimes cause poor contact and have low reliability.

[0003] Photomos relays have no mechanically moving parts, so they can provide higher reliability than mechanical relays, but there is a demand for photomos relays with even higher reliability and longer life.

0004

2. Description of the Related Art FIG. 8 shows a diagram illustrating a conventional example. In the figure, 10 is a light emitting diode, 20 is a photovoltaic diode, and 30 and 40 are MOS field effect transistors (hereinafter referred to as FETs) whose gates and sources are connected to each other and whose train is an output terminal. It is.

[0005] When a current If is passed between the terminals A and B, the light emitting diode 10 emits light, and the light output generates an electromotive force at both ends of the photovoltaic diode 20. This electromotive force is F
It is applied between the gates and sources of ET30 and 40, and the FET
30 and 40 are turned on, and conduction occurs between terminals C and D.

Conversely, unless a current If is passed between terminals A and B, the light emitting diode 10 will not emit light, the FETs 30 and 40 will be turned off, and the terminals C and D will be open. FIG. 9 is a time chart of the conventional example, and shows the “on” and “off” of If.
In response to this, the light emitting diode 10 emits light, and the FET 30
, 40 is applied with voltage Vo, and terminals C and D are "on",
Go “off”. Vth shown in the figure is a threshold voltage between the gate and source at which the FETs 30 and 40 are turned on.

[0007]

In the conventional example described above, the terminals C and D are turned on and off in response to the turning on and off of If.

[0008] There are the following three usage states of such a relay. ■ Used in the "on" state and remains in that state for a long time. ■ Used in the "off" state and remains in that state for a long time.

[0009] ■ Cases where "on" and "off" are frequently repeated. There is a problem with using the PhotoMOS relay in the condition ■. This means that if the "on" state is long, the light emitting diode 10
This is because the light continues to emit light.

Generally, the amount of light emitted by the light emitting diode 10 has a characteristic that it decreases with time, so when a constant current If is applied, the light output gradually decreases with the passage of time, and the output of the photovoltaic diode 20 decreases. Will it stop occurring?
Alternatively, only a voltage lower than the threshold voltage Vth that turns on the FETs 30 and 40 in the next stage can be generated.

The present invention aims to extend the life of a photomos relay that is used for long periods of time in the "on" state.

0012

Means for Solving the Problems FIG. 1 is a block diagram illustrating the principle of the present invention. In the figure, 1 is a photomos relay, 10 is a first light emitting diode that emits light according to an input signal, and 20 is a first light emitting diode 10.
30 and 40 are first and second photovoltaic diodes that are turned on and off depending on the output of the first photovoltaic diode 20; This is a second MOS field effect transistor.

Further, 50 is a second light emitting diode provided in the photomos relay 1, and 60 is a light output output from the second light emitting diode 50, which is connected in the opposite direction to the first photovoltaic diode 20. 70 is a second photovoltaic diode that receives light and generates an electromotive force, and 70 maintains the "on" state by the output of the first photovoltaic diode 20, and the output of the second photovoltaic diode 60. The light-emitting diode 10 and 50 are state-holding means that maintain the "off" state by the "on" and "off" states, and drive the first and second light emitting diodes 10 and 50 with a single pulse current only when the light-emitting diodes 10 and 50 are turned on or off.

[0014]

[Operation] Two sets of first and second light emitting diodes 10 and 50 and first and second photovoltaic diodes 20 and 60 are provided, and the output of the first photovoltaic diode 20 is connected to the state holding means 70 as a positive electrode. The output of the second photovoltaic diode 50 is input to the state holding means 70 with negative polarity.

The state holding means 70 maintains the "on" state and "off" state by a single input of positive polarity and a single input of negative polarity.
, 50 are driven by a single pulse current, the life of the photoMOS relay 1 can be extended.

Furthermore, by providing a rectifier circuit 80 between the photovoltaic diode 20 and the MOS field effect transistors 30 and 40, the light emitting diode 10 can be driven with a pulse current, and the life of the photoMOS relay 1 can be extended. It becomes possible to

Furthermore, the FETs 31 and 41 whose threshold voltage Vth is a negative voltage are used, and the photovoltaic diode 20
By applying the output of FET 31 and 41 between the gates and sources of FETs 31 and 41 in a negative potential direction, the light emitting diode 10 does not emit light when the photo MOS relay 1 is in the "on" state, thereby extending the life of the photo MOS relay 1. It becomes possible to

[0018]

Embodiment FIG. 2 is a diagram illustrating an embodiment of the present invention. In the figure, 10 and 50 are light emitting diodes, 20 and 60 are photovoltaic diodes, 30 and 40 are FETs, 71 is a thyristor as a state holding means 70, R3 and R4 are resistors, and ES is a battery.

Here, a pulse current If1 is applied between terminals A and B.
When the light is supplied, the light emitting diode 10 emits light, the light reaches the photovoltaic diode 20, and a pulse voltage is generated in the photovoltaic diode 20. The potential at point g is positive with respect to point h, and the thyristor 71 is turned on.

At this time, the potential e at point i is e=[R3/(
R3+R4)]×(5-0.7)V, FET30
, 40 are turned on.

5 indicates the voltage of the battery ES, and 0.7 indicates the voltage drop due to the thyristor 71. Next, when a pulse current If2 is passed between the terminals E and F, the light emitting diode 50 emits light.
The light reaches the photovoltaic diode 60 and generates a pulsed voltage across the photovoltaic diode 60.

At this time, the potential at point g is negative with respect to point h, and the thyristor 71 is turned off, turning the FETs 30 and 40 off. With the configuration shown in FIG. 2, a single pulse current is applied to the light emitting diodes 10 and 50 only when the FETs 30 and 40 change states between "on" and "off".

FIG. 3 shows a time chart of an embodiment of the present invention. FIG. 4 is a diagram illustrating another embodiment (1) of the present invention. This is an example in which a rectifier circuit 80 consisting of resistors R1, R2 and a capacitor C is added to the conventional structure of FIG. 8, and the driving current of the light emitting diode 10 is a pulse current.

FIG. 5 is a time chart of another embodiment (1) of the present invention. The voltage across capacitor C is Vo
shall be. Here, when a pulse current If shown in (A) is passed between terminals AB, the light emitting diode 10 emits light in a pulsed manner, and upon receiving the light pulse, the photovoltaic diode 20 generates a pulse voltage.

Capacitor C is charged with time constant τ=R1·C and discharged with time constant τ=R2·C, and the voltage across capacitor C has the voltage waveform shown in (B). The lowest value of this smoothed voltage is the threshold voltage V of FETs 30 and 40.
By selecting the values of resistors R1, R2 and capacitor C such that they do not become less than th,
FETs 30 and 40 are "on" even if the emits light in a pulsed manner.
state can be maintained.

FIG. 6 is a diagram illustrating another embodiment (2) of the present invention. FET 30 constituting the conventional example of FIG.
In this example, depletion type FETs 31 and 41 having a threshold voltage Vth of -2V are used instead of 40.

FIG. 7 is a diagram illustrating the characteristics of a depletion type FET. In Figure 6, a current I between terminals A and B
When f is applied, the light emitting diode 10 emits light, and upon receiving the light, the photovoltaic diode 20 generates a voltage.

Here, the potential at point g is negative with respect to point h, and the gates of FETs 31 and 41 are
The potential between sources is approximately -3V. Depression type FE
The drain current-gate-source voltage characteristic of T is shown in (A), and the drain current-drain-source voltage characteristic is shown in (B). From the figure, when VGS=3V, FETs 31 and 41 are
You can see that it does not turn on.

Conversely, the light emitting diode 10 does not emit light unless the current If is passed between the terminals A and B, so the voltage across the photovoltaic diode 20 becomes "0" and the FETs 31 and 4
It can be seen from the figure that 1 is "on".

[0030] Therefore, when "If", FET31
, 41 are "off", If FETs 31 and 41 are "off"
can be in the "on" state, Photomos relay 1
When the light-emitting diode 10 is used in the "on" state for a long time, the light-emitting diode 10 can be used in a non-emitting state, resulting in a longer lifespan.

[0031]

[Effects of the Invention] According to the present invention, by using a thyristor, a light emitting diode is driven with a single pulse current only when the photomos relay is turned on or off.
By rectifying the output of the photovoltaic diode with a rectifier circuit, the light emitting diode is driven with a pulsed current.
By using a depletion type FET, a long-life photoMOS relay can be realized by turning the drive current of the light emitting diode "off" when the photomos relay is in the "on" state.

[Brief explanation of drawings]

[Figure 1] Block diagram explaining the principle of the present invention

[Figure 2
] Diagram explaining an embodiment of the present invention

[Figure 3] Time chart of the embodiment of the present invention

[Fig. 4] Diagram explaining another embodiment (1) of the present invention

[Fig. 5] Time chart of other embodiment (1) of the present invention

[Fig. 6] Diagram explaining another embodiment (2) of the present invention

[Figure 7] Diagram explaining the characteristics of depletion type FET

[Figure 8] Diagram explaining the conventional example

[Figure 9] Time chart of conventional example

[Explanation of symbols]

10, 50 Light emitting diode 20, 60 Photovoltaic diode 30, 40 FET 31, 41 Depression type FET 70 State holding means 71 Thyristor 80 Smoothing circuit ES Battery R1, R2, R3, R4 Resistor C Capacitor

Claims (3)

[Claims] 1. A first light emitting diode (10) that emits light in response to an input signal;
) receives the light output from the first photovoltaic diode (20) and generates an electromotive force, and is turned on and off by the output of the first photovoltaic diode (20). The first and second MOS field effect transistors (30, 4
0), the second light emitting diode (50) is connected in the opposite direction to the first photovoltaic diode (20). ) a second photovoltaic diode (60) that receives the light output output from the photovoltaic diode (60) and generates an electromotive force;
state holding means (70) for maintaining the "on" state by the output of the photovoltaic diode (20) and maintaining the "off" state by the output of the second photovoltaic diode (60); Only when “on” or “off” are the first and second
A long-life photomos relay characterized by driving light emitting diodes (10, 50) with a single pulse current. 2. A photoMOS relay (1) comprising a light emitting diode (10), a photovoltaic diode (20), and first and second MOS field effect transistors (30, 40).
), a rectifier circuit (80) consisting of first and second resistors (R1, R2) and a capacitor (C) for rectifying the output of the photovoltaic diode (20) is provided, and the light emitting diode (10) is A long-life photomos relay that is driven by pulsed current. 3. A light-emitting diode (10), a photovoltaic diode (20), and an output of the photovoltaic diode (20), the cut-off threshold voltage for turning "on" and "off" is set at a negative potential. 1 and a second MOS field effect transistor (31, 41), the output of the first photovoltaic diode (20) is connected to the first and second MOS field effect transistor (31, 41). A long-life photoMOS relay characterized by applying a negative potential between the gate and source.