LT1248 Facing a trouble while AC/DC Conversion.

Hello all,

I have designed an 1KW AC/DC conversion with PFC using LT1248.

I have observed some weird performance here,

1. First of all, When i connected VCC from another low current AC/DC converter, It's output voltage got dropped to 3.7VDC from 17VDC, which was working fine before connecting the output to LT1248.

2. So, I connected the bench power supply with 17VDC and observed no switching at the transistor, so no 400VDC at output as per my design, instead I am getting 315VDC which is just smoothing of pulsating DC output from rectifier by 560uF capacitor.

3. Now i removed 17VDC connection from Bench power supply and left the connection open, I got a mild current shock at my hand when I touched the wire which was connected to VCC pin, Shockingly, there is same amount of shock I felt when i touched the GND pin too. This observation is made When AC is turned ON. Below schematic will show the circuit in this condition.

I am unable to understand the situation here, Also Please forgive me if my English is bad, as English is not my first language.

[Edit] : I have checked continuity of all pins, no pin is shorted. also I have checked any short externally happening, none are observed. Shock is bothering me, mainly the voltage difference between VCC and GND, when measured potential difference is around 1.7VDC and reduce gradually when AC is turned off.

Thanks and best regards,

Jayanth Pasumarthi.



[Edit] : I have checked continuity of all pins, no pin is shorted. also I have checked any short externally happening, none are observed. Shock is bothering me, mainly the voltage difference between VCC and GND, when measured potential difference is around 1.7VDC and reduce gradually when AC is turned off.
[edited by: p_j at 9:51 AM (GMT 0) on 30 May 2019]