[SOLVED] ORing diodes replacement for high voltage (160V)

[ats2]

Hello,
I have 2 input voltage for oring, voltages between 150-160Volts.
The output current is about 10Amps, so there is a lot of loss on diodes.
ORing controllers are generally below 75Volts.
Is there any way to do this with n channel mosfet?


Regards.

 

[mtwieg]

Sure you can do it, but I don't think anyone makes a dedicated IC which works at such voltages. You'd have to roll your own using an isolated supply and isolated gate drivers. You could try doing it with fancy integrated isolated supplies like the ADUM6132.

 

[schmitt trigger]

There are photovoltaic optocouplers which are designed to produce a low current supply to drive isolated Mosfets.

For instance, the Toshiba TLP190B mentions:

The TLP190B consists of an infrared emitting diode optically coupled to a series connected photodiode array which is suitable for MOSFET gate drivers.

TLP190 : Mini Flat Package, 4Pin, one circuit.
• Open voltage: 7.0V (min)
• Short current: 12.0 μA (min)
• Isolation voltage: 2500 Vrms (min)
• UL-recognized: UL 1577, File No.E67349
• cUL-recognized: CSA Component Acceptance Service No.5A

There are other companies that make similar products. Google photovoltaic output optoisolators.

 

[ats2]

Thank you,
what about enabling the isolated driver? Using a voltage comparator, or is there any other simple solution?
Kind Regards.

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Thank you,
I used vishay vo1263 before. But for this ORing application I doubt if would be slow at turn on and off.
If I use mosfet IPT111N20NFD total gate charge 87nC. VO1263 current is about 30uA. So, turn on time is about 87n/30u= 3 miliseconds.
Turn off time is longer too. So, I am not sure if this relatively high turn on and of duration cause large reverse currents.

 

[schmitt trigger]

Yes, they are slow to turn on and off.

For the turn on, you could rely in the Mosfet's intrinsic body diode or use an external diode in parallel.

For the turn off, I remember that there are photovoltaic optocouplers which incorporate a fast turn off circuit. If I recall correctly, they were manufactured by Ixys. but other vendors may have them as well.

 

[ats2]

Thank you,
what about enabling the isolated driver? Using a voltage comparator, or is there any other simple solution?
Kind Regards.

 

[mtwieg]

Some sort of comparator with hysteresis would be a good start. Depends on exactly how you want the circuit to behave.

If you use an isolated supply, you could put all the voltage/current sensing circuitry on the isolated side. That would simplify things quite a bit (but maybe make debugging trickier).

I've also seen app notes where hotswap and OR-ing controllers are used with voltages beyond their ratings by providing them with a virtual ground that tracks the output voltage (usually uses some zener diodes or bjts). Using an isolated supply is also an option for creating the virtual ground.

 

[schmitt trigger]

Good trick mtwieg.

 

[mtwieg]

Here's one LT app note that gives some examples:
https://www.analog.com/media/en/technical-documentation/application-notes/an107f.pdf

This circuit in figure 3 should be applicable to arbitrarily high voltages, though the dissipation in that resistor may become quite high. At that point an isolated supply might be a more attractive option.

 

[ats2]

Thank you.

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I also found similar product of diodes incorporated ZXGD3111.