UC2526: A Certain PWM pulses are missing after certail sequence of proper PWM Pulses.

Ramana murthy

Expert 1640 points

Part Number: UC2526

Dear Sir,

UC2526 is regulating Buck Converter output Volatge.

0 John Griffin1 over 4 years ago

Hello Murthy,

You have 2000 microFarads of capacitance on the CSS pin of this ic and you are using the RESET pin to turn on and off the PWM.

Do you realise that pulling RESET low causes the internal Q1 transistor to short out the CSS capacitor and forces the ic to absorb this energy ?

The CSS pin has an absolute max sink current rating of 200mA and you need to limit the discharge current on CSS to a value well below this limit.

I suggest that you use an open collector transistor on the error amplifier output and drive this transistor low to reset your PWM.

Regards

John

0 Ramana murthy over 4 years ago in reply to John Griffin1

Expert 1640 points

Dear Sir,

Please Suggest Schematic how to Connect

"i suggest that you use an open collector transistor on the error amplifier output and drive this transistor low to reset your PWM."

0 Ramana murthy over 4 years ago in reply to John Griffin1

Expert 1640 points

Dear sir,

To limit the Charging current and discharging current.

But i am using this configuration from many days.it is working fine.

0 John Griffin1 over 4 years ago in reply to Ramana murthy

Hello Murthy,

If you are happy that it is working fine then that's your decision.

I dont have anything further to add to my previous suggestions.

Regards

John

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