Author Topic: Capacitors in series for higher voltage applications  (Read 201 times)

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Offline Red_Micro

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Capacitors in series for higher voltage applications
« on: May 19, 2020, 09:48:31 pm »
From the first circuit below, the red area is a startup network. The App Note states:

Quote
The dimensioning of the startup network starts from the choice of the MOSFET Q3. Q3 is a depletion MOSFET and is connected to the middle point between the input capacitors C6 & C8. This enables the MOSFET to be rated to 500V.

My question is: if I have three capacitors in series, then the bus voltage is divided by three. Now I don't have a single middle point, but two middle points. Is it okay if I connect my startup transistor in the second point, like shown in the picture?


 

Offline T3sl4co1l

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Re: Capacitors in series for higher voltage applications
« Reply #1 on: May 19, 2020, 10:19:55 pm »
Sure... but, will that point have enough minimum voltage, and is the resistor divider dimensioned such that 1. adequate startup current can be delivered and 2. the upper caps won't be overvolted in the process?

Tim
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