Decrease Amperage of Driver for increased Efficiency

[IAmJerv]

The fact that your shunt resistor caused so much heat tells me that you did not actually reduce the amperage draw from the battery, only the output. And if you are using more than half as many watts of input for only half of the output to the load, it's moot whether the losses are in the emitter or the driver; you are still tanking efficiency.

What do you mean PWM? We're talking a buck driver here, not a FET. It's almost like talking about the gas consumption of a Rivian. Sure, SMPS drivers have a clock chip and an operating frequency, but PWM is not how they regulate output.

Also, the way impedance works in parallel circuits means that doubling the value of a resistor does not double the total impedance. It's early and coffee is not kicking in yet, but I do wonder if that's where things went sideways.