For the below circuit, VIN = 12V. (using 220V to 12V adapter) and frequency of 3.3V PWM signal : 500 Hz
In the below case we have two white light strips connected in parallel which will result in total of 4A of current. The issue is the MOSFETs (Part no: TSM240N03CX RFG ) which we are using is not able to support 4A of current. You can check the datasheet
So, can you suggest me the possible design changes that are required in our circuit such that it will support 4A of current.
Rds(on) is not guaranteed with 3.3V drive and the specifications are rather on the optimistic side even with proper drive. At 4.1A the dissipation could be in the 0.85W range which is very high for an SOT-23. 1.56W is purely a theoretical number. Rds(on) is specified at a given Vgs and it increases significantly (about 50% typically) at maximum Tj, further increasing the \$\text I^2\text R\$ power dissipation.
I suggest a beefier MOSFET designed for 3.3V or less drive, for example an AON7524 which will dissipate around 100-120mW with 4.1A drain current flowing, barely enough to get warm if you give it a square inch or so of copper.
You should not get much in the way of switching losses at only 500Hz with a zero ohm gate resistor, but if you add a larger resistance in there you will increase switching losses. Beefier MOSFETs tend to have more gate charge so they switch more slowly for a given amount of available gate drive current. Something to keep in mind if you're thinking of increasing PWM frequency. At some point a gate driver circuit capable of driving peak currents in the amperes rather than mA or tens of mA becomes desirable.
Actually the datasheey says it DOES support 4.1amps at Tc100°, and 6.5amps at Tc 25°.
Having said that, two obvious options are-- 1) use a higher rated mosfet. Part number will be easy to find. 2) connect your LED strips in series and use a 24 v power source.
Alternately, you haven't mentioned your pwm duty cycle. If this is lowered, you might still get desired brightness at lower average power.
Lastly, also not mentioned is how you are controlling this current?
Is this a theoretical design or a practical observation?
