SMPS DESIGN USING TNY276-P
I am designing SMPS using TNY276P (7.2W). I referred your design DER-108
My BP/M pin capacitor is .1 uF & I am deriving 1 output of 24VDC with max. of 200mA current.
While testing drain waveforms, TON-TOFF-TNO_CONDUCTION, I am getting it as
TON_TOFF_TNO_CONDUCTION_TOFF & then cycle is repeated . Means I am gettinf TOFF twice in each ON-OFF cycle of Mosfet. Can you give any idea?
Presently I am testing this SMPS on 70VDC , but I have to then test it on 330VDC which I am deriving from 230VAC. So I will not get isolating of neutral to source pin of TNY276P. What is remedy?
Comments
Dear Sir,
I referred your design DER-108 for this design.
If I removed secondary winding, (i.e. diode of secondary) , now only primary & bias windings are in picture & my circuit works well. i.e. I get EN/UV pin waveform 1.1V to zero &BP/M pin voltage= 5.78 to 6V.
If I placed the diode of secondary winding from which I am deriving 24V, it gets overheated & my circuit fails i.e. feedback winding also collapses.
I used the same transformer design procedure which you have given in DER-108 also BP/M pin cap= 10uF as per your suggesstion.
Can you please solve it?
Dear Sir,
I referred your design DER-108 for this design.
If I removed secondary winding, (i.e. diode of secondary) , now only primary & bias windings are in picture & my circuit works well. i.e. I get EN/UV pin waveform 1.1V to zero &BP/M pin voltage= 5.78 to 6V.
If I placed the diode of secondary winding from which I am deriving 24V, it gets overheated & my circuit fails i.e. feedback winding also collapses.
I used the same transformer design procedure which you have given in DER-108 also BP/M pin cap= 10uF as per your suggesstion.
Can you please solve it?
Thanks for your support.
I got my yesterday's problem solved.
Now my SMPS is working for 70VDC & I am getting output=15VDC for no load.
I want 24VDC so I will increase no. of turns of secondary winding.
But now I am facing a serious problem. I moved to variable AC Input
using auto-transformer. When AC Inut=65VAC, my TNY-276P burned out.
So I removed feedback by removing 27VZ Zener diode (Design is
according to DER-108)
Again I tried to test but as soon as my input=65VAC, again my TNY-276P
burned out. Rest all circuit is well but only TNY-276P is burning. Can
you please solve out this problem?
TinySwitch uses on-off control. So you cannot expect a repeating periodic pattern. TinySwitch will maintain output regulation by skipping cycles as and when necessary.
Another thing - If you want to use the TNY276P you may need to use it in the increased current limit mode (CBP = 10 uF capacitor) which will make the TNY276P look like the TNY267P from a current limit standpoint.