Problem with using UC3855: Low output Voltage

Papajo · 23rd June 2011, 11:54 AM

Hello everybody...
I am trying to use UC3855 (or UC2855) from TI, but i have a problem with output voltage. Some informations:

Vin 85-270Vac
Vout 400Vdc
Pomax 2.5KW
Fs 150KHz

My main inductor is 200uH, ZVT inductor at about 10uH, STW45NM50 for main MOSFET and STW20NM50 for ZVT MOSFET (both of them are driven with ACPL-H312-000E), STTH6012 for main Diode and DSEI30-10A for the ZVT circuit.

In the tests i am doing now, i use as load 1KW. For whatever input voltage i apply, from 85 to 240V, i haven't seen the output Voltage going above 300V. However, switching of the MOSFETS seems to be correct (using a scope).

I also have problem with the temperature of the ZVT inductor (in just 1 min of working, the temperature of the core goes to almost 100oC).

Has anybody who used UC3855 noticed anything similar in output voltage?

23rd June 2011, 11:54 AM	#1
Papajo diyAudio Member Join Date: Jun 2011	Problem with using UC3855: Low output Voltage Hello everybody... I am trying to use UC3855 (or UC2855) from TI, but i have a problem with output voltage. Some informations: Vin 85-270Vac Vout 400Vdc Pomax 2.5KW Fs 150KHz My main inductor is 200uH, ZVT inductor at about 10uH, STW45NM50 for main MOSFET and STW20NM50 for ZVT MOSFET (both of them are driven with ACPL-H312-000E), STTH6012 for main Diode and DSEI30-10A for the ZVT circuit. In the tests i am doing now, i use as load 1KW. For whatever input voltage i apply, from 85 to 240V, i haven't seen the output Voltage going above 300V. However, switching of the MOSFETS seems to be correct (using a scope). I also have problem with the temperature of the ZVT inductor (in just 1 min of working, the temperature of the core goes to almost 100oC). Has anybody who used UC3855 noticed anything similar in output voltage?

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