TOPSwitch-JX, LM431 or LMV431 device

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Hello,

I'm designing a flyback converter using the TOPSwitch-JX. The output power is 50,4 W (84V * 0.6A).

The problem that I have found is that the device LM431 only can reach around 30 V and I have an output voltage of 84 V so I presume that the control loop wont work well.

Could this represent a problem to control the switching device? Can I use three LM431 devices in series to reach 84 V and control the closed loop?

Thanks and kind regards,

What exactly mean LM431 cab reach only around 30V. How are you designing your power supply?

In the datasheet of the LM431 says:

"The output voltage may be set at any level greater than 2.5 V (VREF) up to 36 V merely by selecting two external resistors that act as a voltage divided network."

If I want to design the power converter to supply 84V the LMV431 must reach or surpass those 84V in order to prevent the current from flowing through the optocoupler when the voltage is equal or lower than 84V, and allow the current flowing through the optocoupler when the voltage is higher than 84V. That makes any sense? so I guess that I have to put a zener of 84V or a LMV431 (around 30V) plus a zener of around 60V in series. Is it correct?

Thanks.

you don't need to put any zener diode. As the LM431 ref takes 2.5 V , put a feedback circuit from Vout to the vref pin of LM431, just use a normal potential divides from Vout (84V).