TNY267PN: Operation at 50 Hz
We may have a problem at 230 Vac/50Hz. We have a power supply using a TNY267PN and PNY-12238 transformer from Premier Magnetics Inc. One secondary is used for the +12V o/p. One secondary is used to provide -12V through a linear regulator. A +5 o/p is derived from the +12V o/p through a linear regulator. The +12V o/p, before the +5V linear regulator is fed back to the TNY267 through an optpcoupler. We are not sure if the power supply is collapsing, oscillating, restarting or doing something else in a way that will upset any of the following relations: +12V > +5V > gnd > -12 V where all differentials must be > 2V. We have seen no problems at 60 Hz. (My first post. Any help is welcome.) Tx. JJ
Comments
Thanks for the help. I inherited the design and do not know what tools (if any) were used in the design. The design may have been taken from a reference design or from an applications note. By bulk capacitor I presume you mean the cap at the primary of the switching transformer. If so it is 4300 pF.
jjtech
Canada
The bulk cap is also called DC input storage capacitor C_IN as shown in Figure 1 of Application Notes AN-23
http://www.powerint.com/sites/default/files/product-docs/an23.pdf
Would you please tell me your input voltage range and output current for each output voltage so that we can determine whether you have sufficient capacitance of the bulk cap.
TNY267PN at 50 Hz: The bulk cap is 22 uF 400 V electrolytic. The 4300 pF cap is is the snubber. Requested info will follow. Can you direct me to an app note using the TNY267PN with the PNY-12238 tranformer?
Thanks again.
jjtech
Canada
The power supply loads are on the low side with a total of 1 to 2 Watts for all three loads. As the +12V supplies the +5V through a linear regulator I would guess that this load at the PNY-12238 transformer is 50 to 100 mA (i.e. 600 to 1200 mW). The load at the PNY-12238 transformer for the -12V side is much lower at 8 to 10 mA or 96 to 120 mW. Thanks again. JJ
I should have noted that the smps input is 85-265 VAC/VDC. We have tested the design in a lower power applications down to 60 Vac. Rgards. jjtech
Although you have not given your detailed specification of your power supply, I suspect that you have barely enough workable bulk cap voltage at 230Vac/60Hz. The bulk cap voltage will be lower at 230Vac/50Hz. Have you designed your power supply using our PI Expert software (PIXLs Designer)? If you've used 50Hz when you ran our software, the design should have considered the correct worst case bulk cap voltage. You may try to put on a very big bulk cap to see if the problem is gone or not. Bur eventually, you should try to find the correct transformer parameters using our PIXLs and compare them to your existing transformer to find the differences.