I need to send a signal through fiber optic to switch a DC/DC Converter (I want it to be on when there is photocurrent, and off when there isn't), I can't use a normal cable because I want to do that in a region sensitive to EMI (ElectroMagnetic Interference).

I'm also using fiber optic for transmitting another signals and that works well, but I'm struggling with the design of this switch.

I thought of using a NPN or PNP as a switch but I don't know how can I polarise it, since I don't know how the DC/DC Converter will affect to the polarisation of the transistor.

For the fiber optic link I'm using the transmitter SFH757V and the receiver SFH250V, and like the photo, my DC/DC Converter is TSR 1-2450.

Thanks in advance!

TSR 1-2450 Datasheet

SFH757V Datasheet

SFH250V Datasheet


simulate this circuit – Schematic created using CircuitLab

  • 1
    \$\begingroup\$ I suggest that you look at schematics using a "high side" PMOS switch, for example: electronics.stackexchange.com/questions/42030/… Replace the NPN T1 in that schematic with your optical receiver. The DCDC converter will be the load \$\endgroup\$ – Bimpelrekkie May 28 '19 at 11:56
  • \$\begingroup\$ Thanks @Bimpelrekkie! I will give it a try, I never thought about using PMOS, I guess I always try to use BJTs \$\endgroup\$ – takihama May 28 '19 at 20:38
  • \$\begingroup\$ The reason for suggesting a PMOS is that the optical receiver will only generate a very small current, that might not be enough for a BJT to fully switch on (saturate) but that is no issue for a MOSFET as that only requires a voltage. \$\endgroup\$ – Bimpelrekkie May 28 '19 at 20:59
  • \$\begingroup\$ I also thought of using a cascade of two NPNs to assure saturation mode at highers load currents, aprox 1 A that is the maximal current that the converter can provide \$\endgroup\$ – takihama May 28 '19 at 22:19

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