Still lacking parameters.

You've stated the voltage you're looking to control is 19 volts. Okay, fine. But what is the current? Milliamperes? Amps? Kilo amps?

The typical laptop supplies are anywhere from 65 to 100 watts. At 19 volts, that's 3.4 to 5.2 amps. Is that enough for your heater? Do you know it's wattage? If so, at what rated voltage?

Since most digital pots are good for a few milliamps, I think you need to take that of the list of possible solutions.

Now a question for you. If you said your heater is 19 watts at 19 volts, it will consume 1 amp. If I apply 50% voltage, 9.5 volts, I'll have a heater that dissipates 9.5 watts, right? Yes, of course it will.

Now, what would happen if I applied 19 volts but I turned the voltage on for 1 second and off for 1 second in a continuous fashion? What would the *effective* wattage be with that 50% duty cycle pulse applied to my heater?

If you're not the OP, please allow him to respond, please ?