how to make 150-315 VAC input 5V 0.5A output design like DI152

Posted by: kemred on 11/07/2012

I want to modify DI 152 to operate in 150-315V AC input, but PIEXPERT gives an error above 300VAC input, how can I do, I thing Vor is around 20-30 V for this design and with 350VAC input total ;

315*sqrt(2)+Vor+Vspike(200V) =445+30+200= 675V so 25V margin left, can this be done?

Or should I use an external power switch?

Best regards,

Comments

I think the voltage stress should be ok, based on the RDK295, which is a 5V4A design for 90Vac-295Vac input. Tny290 and TNY280 are almost same thing, and I donot think 10Vac is a lot difference, because the Vds can be controlled by snubber design too.

I do not know why the PI expert gives error . If the error is caused by high Vds, you have to reduce the Vor. Anyway you can not just use the same transformer as the one for di-152, because the volateg stress is the biggest issue for your application. you have to rduce Vor for your design.

Regards

I tried the DI152 design for 315 V there is not any problem,

Vor is around 40 V for this design and max voltage is 315*1.414= 445V

When I tried DI152 I see a spike when turn off around 200 V so I see a 640V stress on mosfet, Due to AN16 there must not be such a stress for 40V VOR, according to this note stress will be around 1,5*1,4*40+20V= 100V, and total drain voltage be around 550 V, so due to this theory there must not be any dangerous spike but since I see 200 V I add serial TVS to snubber limit the spike,

I thing decreasing VOR further more will increase Dmax which is abot 0.8 for DI152.. so it is not feasible am I right?

Best regards,

Actually lower Vor means lower duty cycle. But a little bit lower Vor cannot help you a lot for voltage stress, since 40V is not a big deal for 640V. You can reduce the damp resistor R2 from 100 ohm to 50 ohm or even 20ohm. The spike can be much better, but you need to double check the EMI.

You are right Dmax proportional with VOR.. Thanks for the snubber values but I want to know how to design snubber easily and correctly, is there any detailed application note?

I will try resistor values you advised, do we need to increase power of the R2?

Same size should be used as R2, although the power loss should be less with a lower value resistor.

Fo rthe snubber design, I really do not know which document is good from PI, but you can google it. I believe you can find some articles on the snubber.

Regards