PVA1352 driving an LED.
Fig. 1

Bidirectional Solid State Relay Circuit as Analog Switch

by Lewis Loflin

A bidirectional solid state relay (SSR) can be considered an analog switch. It can control AC or DC like a mechanical switch without the problem of mechanical contacts.

I had a PVA1352 left over from plasma cutter repair days. That is pictured above driving an LED.

The ratings for the PVA1352 is a Power MOSFET Photovoltaic Relay Single-Pole, Normally-Open, 0-100V AC/DC, at 375mA. To quote,

The output switch is controlled by radiation from a GaAlAs light emitting diode (LED), which is optically isolated from the photovoltaic generator.

The PVA13 Series overcomes the limitations of both conventional electromechanical and reed relays by offering the solid state advantages of long life, fast operating speed, low pick up power, bounce-free operation, low thermal offset voltages and miniature package.

The PVa1352 is obsolete and hard to find today. I searched for an alternative.


Fig. 2

Fig. 2 illustrates the internal construction behind bidirectional SSRs. This consists of a photovoltaic opto-coupler such as the VOM1271.

See VOM1271 Photovoltaic MOSFET Driver Circuits.

The output consists of two MOSFETs connected gate-to-gate and source-to-source. The output is taken from the two drain connections on the MOSFETs.

The positive side of the VOM1271 goes to the gates and the negative to sources. While N-channel MOSFETs are used here, P-channel works just as well reverse the positive and negative connections. I have built both.

PVA1352 electrical connections.
Fig. 3

Fig. 3 is the electrical connections to the PV1352 that doesn't show the two MOSFETs.

PVT212 electrical connections.
Fig. 4

Fig. 4 illustrates a PVT212 described as "Power MOSFET Photovoltaic Relay Single-Pole, Normally-Open, 0-150V, 550mA AC / 825mA DC.

It has an extra connection to the MOSFET source connections allowing alternate electrical connections as shown.

For more on this subject see Build High Power MOSFET Directional Switch Relay

Alternative Parts

The Vishey VOM1271T is available from Mouser Electronics for $2.33 each or $1.94 each Qty 10.

An alternative is the Toshiba TLP3906 $2.08 each or $1.69 each Qty 10.





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