Just a note here:
PWM only limits the power you draw, and NOT the instantaneous current drawn. This is because PWM is digital (pulse width modulation) and is all about switching something on/off enough times to approximate the amount of "power" that you would get with a lower voltage. As this is the way the MOSFETs are expected to work in all our electronics circuitry (on/off), it's the only real way to drive the outputs. It's also (generally) fairly efficient.
This means: You still need to have wiring (and electronics) that can handle twice the current if you're using a heating element that was previously used at 12V, when using it at 24V.
The main thing here is fuses (eg: on your electronics), which may blow if they get too much current, or your PSU may not be capable of producing that much instantaneous current and shut down.
Personally, I just prefer to use a heating element that draws a reasonable amount of current at the expected voltage to give the desired amount of power. For an extruder, and for 24V, I tend to use 18 ohm or 22 ohm resistor coated in vitrified enamel (~32W or ~26W respectively), or a ceramic heater that's been specced for no more than 40W @ 24V.
Comparison: A 6.8 ohm resistor at 12V puts out ~21W, and a 5.6 ohm resistor at 12V puts out nearly 26W - and they're pretty standard values used in most hot ends.
PS: Note that if we were to drive a MOSFET with an analog method, we'd require a much more complex circuit, everything would be much less efficient, and we'd have a lot of excess heat in the MOSFETs as a by-product.
PWM only limits the power you draw, and NOT the instantaneous current drawn. This is because PWM is digital (pulse width modulation) and is all about switching something on/off enough times to approximate the amount of "power" that you would get with a lower voltage. As this is the way the MOSFETs are expected to work in all our electronics circuitry (on/off), it's the only real way to drive the outputs. It's also (generally) fairly efficient.
This means: You still need to have wiring (and electronics) that can handle twice the current if you're using a heating element that was previously used at 12V, when using it at 24V.
The main thing here is fuses (eg: on your electronics), which may blow if they get too much current, or your PSU may not be capable of producing that much instantaneous current and shut down.
Personally, I just prefer to use a heating element that draws a reasonable amount of current at the expected voltage to give the desired amount of power. For an extruder, and for 24V, I tend to use 18 ohm or 22 ohm resistor coated in vitrified enamel (~32W or ~26W respectively), or a ceramic heater that's been specced for no more than 40W @ 24V.
Comparison: A 6.8 ohm resistor at 12V puts out ~21W, and a 5.6 ohm resistor at 12V puts out nearly 26W - and they're pretty standard values used in most hot ends.
PS: Note that if we were to drive a MOSFET with an analog method, we'd require a much more complex circuit, everything would be much less efficient, and we'd have a lot of excess heat in the MOSFETs as a by-product.