audible noise from 120w smps
Dear sirs,
we have designed a 12v 10A smps using PI expert, At power up the voltage is OK. when loaded with 1A load performance is Ok. but when we load around 4A, we get a high frequency noise, and after afew minutes the output shuts down and starts blinking. we do require an immediate solution for this, pl provide necessary support. The device is TOP249 and the transformer is ETD39.
regards
padmanabhan.k
Comments
Dear sir,
To-day i have tested the circuit and found the following,
1.the output diode and the TOpswitch are heating.
2.the snubber was getting little hot, found that the fast recovery diode was wired up in place of the Ultrafast diode, after replacement the snubber heat came down, but the TOPswitch continues to heat up and produces audible noise after a load of 40%, and continues to shut down.
3.for trials we replaced the TOP249y with 250Y, the noise continues, but the shutdown time has increased from
1m... about 3mts.During the whole trials the output voltage remains constant at 12.18v till shutdown.
Sir,
1. Could you please probe the voltage across the secondary diode and confirm that the off-time voltage across it is indeed lower than the PIV rated for the diode.
2. Since the secondary diode is heating, you might want to replace it with one that is rated for 30A -or- provide better heatsinking to the diode and check if it resolves the issue.
hi, padmanabhan
you can solve the problem, i am have the same problem, no noise problem, but yes the power output problem
please help me
thank you very muc
Sir,
Since the output shuts down after some time and starts blinking (and the fact that the power supply is well regulated under a load of 1A), there seems to be a thermal issue followed by auto-restart.
1. Try to find out if there are any devices that are overheating. (The clamp or the secondary diode are the usual suspects)
2. Kindly observe the load voltage and confirm that the device is actually in auto-restart. The device will be in auto-restart when the feedback loop is open circuited.