premkumar9
Member
The peak forward current is much higher than average current. Design will ensure that current will not exceed permissible limits (As i mentioned earlier LED is are connected in parallel serial combination with series resistance with each branch)Then the LEDs instantly burn out because the peak current is too high.
It is an accepted fact that switching regulation is far more efficient than series regulation where efficiency comes down as input voltage increases. Here we have to conclude that only switched mode regulation will meet my needs.Of course the battery limits the current. It and its connecting wires have resistance.
The mosfet also has on-resistance that limits the current.
These current-limiting resistances either are too low so the current is too high and the LEDs burn out, or the resistances waste a lot of battery power like a linear regulator.
PWM reduces the heating of the Mosfet driver if its on-resistance is low enough. An external current-limiting device is needed and it wates power by making heat. Efficiency is not any better than a linear regulator and might be worse.
A buck converter increases efficiency.
Then about buck converter. What I am suggesting is also something with the same principle. Only difference is conventional buck converter uses and inductor to store energy and supply it to the load when the series transistor is OFF. In this case since the load is LED I am driving higher current (of course with in permissible peak current limits) when transistor is ON to maintain the average brightness and there is no current flow when it is OFF. I want to avoid inductor.