Audible Noise from TNY268PN based AC/DC converter circuit (battery charger)
Hi Power Integrations Support Team,
I have designed battery charger circuit based on TNY268PN to charge 12V 2.2Ah Sealed Lead Acid Battery. I attached the circuit schematic to this thread. The schematic is based on the circuit given in TNY268PN datasheet (Datasheet Figure 14 2.5W CV CC Battery charger schematic). Charger setpoint is set to around 13.6V and current limit is set to around 600mA. The circuit charges battery as expected, but there is audible noise problem in the circuit as described below.
1. When battery is not connected to the circuit, there is an audible noise.
2.When battery is connected to the circuit, and battery initial voltage is below charger setpoint voltage (in my case it is around 13.6V), there is an audible noise until battery reaches to the setpoint. When battery reaches charger setpoint (i.e), cicuit does not produce any audible noise.
Could you please offer me some solution to solve audible noise problem and also, I would like to know how to calculate R and C values for snubber circuit.
This is first time I am designing AC/DC converter. I am sorry if these are basic questions.
Thank you in advance for your help,
Regards,
Ahmet
Files
| Attachment | Size |
|---|---|
| Charger schematic | 188.4 KB |
Has the transformer been varnished? It is relatively common for an unvarnished transformer to make audible noise since the core faces on the outer legs will rub together in response to the varying AC flux.