PVI5050N series photovoltaic output opto-couplers.

Fig. 1

Connecting Crydom MOSFET Solid State Relays

by Lewis Loflin

In earlier webpages we studied different ways of using photovoltaic output opto-couplers driving power MOSFETs.

Let's look briefly at earlier ideas.

Fig. 1 illustrates the PVI5050N series photovoltaic MOSFET drivers. These don't include an internal gate bleeder resistor which must be added externally.

For these type of units such as the PVI1050N the LEDs can both be turned on at the same time and output pins 6 and 7 can be connected together to generate a higher voltage required by some power MOSFETs. Make sure to add an external gate bleeder resistor.

Enhancement mode MOSFET switch with photovoltaic drive opto-coupler.

Fig. 2

Fig. 2 illustrates using an enhancement mode MOSFET with photovoltaic output opto-coupler. Unlike the earlier transistor based opto-couplers the problem of limitations due to C-E breakdown and Vgs is eliminated. We are limited only by the drain-source current and voltage ratings.

This creates a N.O. relay that is turned on when the LED emitter is turned on.

For more on MOSFETs see:

Internal block diagram Crydom D1D40 MOSFET output SSR.

Fig. 3

Fig. 3 illustrates how the above ideas come together with the Crydom D1D40 type SSRs. We have an input circuit rated 3.5-32 volts, a dual type opto-coupler, and N-channel power MOSFET and various protection circuits.

Fig. 4

Fig 4 shows what the D1D40 case style that can be bolted to a chassis for heat sinking purposes. These come in number of current and voltage ratings.

How to connect Crydom and other solid state relays.

Fig. 5

Fig. 5 shows how to connect solid state relays in general. These are DC input and output - note voltage polarity.

Fig. 6

Fig. 6 shows the PC board mount Crydom DM0063 SSR. They come in a number of current and voltage ratings.

Fig. 7

Fig. 7 internal diagram and electrical connections Crydom DM0063. again this is a DC input and output device so observe polarity.

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