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TOP256EN

Posted by: sheldon on

Hi,
please find attach the schematic for top256EN power supply,
the schematic has details of the complete specs,

the problem is that 5v/1.5A will be the main power supply, the device turns of . when input above 200VAC , this condition is loaded at 5V o/p, only for 800mA and the device shuts off, when on no load the device can operate on full input,
the device is not able to take load when the other outputs are loaded,

please help in this regards,

waiting for positive reply,

thanking You

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Comments

Submitted by PI-Surak on 04/04/2012

Remove Z2 to see if you are geting indavertant OV shutdown.

Also check drain current with scope to make sure transformer is functioning properly

Submitted by sheldon on 04/11/2012

it was tested by removing Z2 zener,

no use?

If it functions without Z2 it would mena that the primary bias circuit it is charging on leakage spikes and you may have to increase the value of Z2 to keep from causing inadvertandt shutdown.

Submitted by sheldon on 04/12/2012

Can this circuit work without the OVP section,

Submitted by sheldon on 04/17/2012

I was Measuring bias Winding it measured about 30V ,

can this be redesigned using PI expert does the outcome of the PI Expert is Optimized,

Pls Help in this Regards,

Thanking You

Submitted by PI-Surak on 04/19/2012

You need to measure bias from bias winding at min load and make sure there is at least 9V. Less than that will cause insufficient bias for feedback opto coupler to drive C-pin correctly.

If you want to use OV function you could just select zener with higher breakdown V and leave bias winding unchanged.