How to fix unstable output frequency ?

[srikavis]

I have 500Watts using SG3524, the problem is the output frequency is not stable as 50Hz. when i increase the load the the frequency also increases more, output voltage also i have to increase to 270v and above, otherwise it is not supporting more load,i replaced SG3524 also,can use SG3525 instead of SG3524.The battery charging voltage is 13v using SMPS Charger ckt. pls tell me how can fix this problem.:sad:

 

[mvs sarma]

Re: Frequency Not stable

as the pwm changes , your frequency measurement appears increasing , otherwise, frequency need not change. how ever you need to ensure that the 12V supply to the chip s cleaner from the load related disturbances, by taking precautions. the R and C used for the osc should better be MFR and polypropylene (box type , instead of a simple disc cap, as disc caps are bad as frequency setting components.

Artwork plays a big role in stability. always use separate wires from battery to the chip and related components. let the battery have separate (thicker wires that feed the load side.
NEVER USE BREAD BOARDED DESIGNS FOR THIS.
Hope with these checks and mods , you can be able to stabilize your board / design

 

[pranam77]

Re: Frequency Not stable

Ensure that the oscillator power pins are getting regulated/ stabilised, and filtered power supply and the biasing components are of high grade as "MVS" mentioned, for better frequency stability.