Is it OK to use a zener diode without a series resistor in a transformer-less power supply?

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Thread Starter

Michael George

Joined Feb 8, 2015
In many circuits, I found that a resistor should be connected in series with zener diode to protect it.
In this circuit, If a series resistor is used, The voltage of the load would NOT be the voltage on the zener diode. The load voltage would be the rectified voltage (230 * 1.414 = 325.22 V DC ). So, We have to use zener diode without the series resistor. But what about the protection of zener diode? The voltage across it is - 325.22 V DC. Is that ok?
Would you give me part number of a zener diode that is suitable for this circuit?
Thank you,


Joined Jun 5, 2013
In this case, the capacitor, C1 is acting in place of the series resistor you would normally find in a DC based zener regulator.



Joined Mar 31, 2012
As noted, discussion of transformerless power supplies is against the User Agreement, therefore this thread has been closed.
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