Request for tech support

Do not see attachment. Sounds like transformer problem since you cannot get full output power. Check phasing and drain current

Dear Sir/Madam;
I have designed a 6v, 1A power supply using TinySwitch-III family by your PIExpert software for 175 to 420 vDC input. The design can be found in the attachment. The rectifier section is a half wave three phase rectifier which can be found in the attachment too.
Implementing the supply, I have the following problems:
1. The no-load output is 5.6v instead of 6v.
2. When I power up the supply connected to 75mA the output voltage is unstable e.g. the output voltage drop down for about 4s and then back to normal, 5.6v. for about 0.5s
3. When powering up the supply in no-load condition and increase the load to 210mA, it works properly. Increasing the load current more than 210mA makes the output voltage unstable e.g. the output voltage drop down for about 4s and then back to normal, 5.6v, for about 0.5s. For 210mA load, this happened after 5 minutes of normal operation.
Please consider that while some of the offered components were unavailable I have used other components instead:
D1: FR106, I used FR107
D3: SB140, I used 1N5819

It would be your kind to let me know whether you have any suggestion about the above issues.
I look forward to hearing from you.
Regards

Dear Sir/Madam;
Thank you for your support. I have changed the transformer and it starts working properly.
I will check some other items and come back to you about the output voltage if needed.
Regards

Hello,

I have designed a power supply with 40 to 300Vdc input voltage and 12W of output power/5V.

I use the TOP266KG and the components you recommends at the PI expert.

I notice in my board, how several component powered by 5V have been damaged due to a overshoot

which is able to rise 8Vpeak  and with quite energy during 7mseg, so it destroys components.

The exactly point where this happen is when the power supply starts up very close to one switch off. 

With a scope I can see how the 5V goes down quitckly due to the input capacitor and if I switch on 

the power supply when the 5v is falling down, then it appears a very damaged overshoot. You can see it 

at the picture attached.

Could you help me please to solve it? I would really apreciated.

Thanks in advance

José López

Hi Jose,

Thanks for Posting your question into forum. At what Input Voltage are you seeing this problem? Is it with full load or No Load?Could you please send us the Schematic?

Regards,

PI-KSAN

Hello PAI-SAN

+ The problem could be seen from 40 to 300V, maybe a bit more at high voltages.  Last picture was taken

at 220Vdc.

The load was 7W but it is seen at 4 or 5W as well.I attached the squematic.

Today I've noticed how if I change R6 to 150 ohms, then the overvolage is quite lower, it reaches 6V only.It

seems to be that regulation is quicker and the overvoltage is under control.

@ What do you think? any problem with this solution?

+ An other question: It is heard a audible frequency by the human ear. The Vout has a ripple of 0.35V and 

beetween peaks there is 100Khz more or less.

@ How could I reduce this sound?

@ It would be possible to reduce the ripple?

Thanks in advance by you help

José