Hello everyone
im trying to bring back to life an old electric scooter which uses a 24v Brushed DC motor rated at 500w, but the motor controller died so i've been trying to design and make a low cost but efficient alternative to control the speed of the motor
So far i know that i should use a power mosfet coupled with pwm to control the speed but when selecting the components, ive come across H Bridges, but a feature of the scooter is that it has a ratchet on the drive sprocket so it can only move the wheel forward so i dont need a full h bridge right? since i dont need it to change directions
my main cuestion is: What are the advantages of using a half H bridge vs using a single power mosfet?
after all im only using a single motor and in one way only. Is there any benefit like handling more current?
And should i use a mosfet driver or stick to logic mosfets? What do you think of using new or experimental transistors like GaN FETs? Maybe i should stick with the cheap h bridge modules? theres so many types of mosfets that i dont really know which one to use
Here are some of the components i've come up with so far
You will need at minimum a 100 Ampere, very low Rds(on) MOSFET and appropriate MOSFET driver for single direction speed control. Don't forget the beefy inductive kick diode!
yepetuardo:
my main cuestion is: What are the advantages of using a half H bridge vs using a single power mosfet?
after all im only using a single motor and in one way only. Is there any benefit like handling more current?
You'll have no motor braking with a single switching element, its a 1-qradrant controller, it will coast on
merrily when you shut down the throttle, so a separate mechanical brake will need to be operated simply
to control speed (not just for emergency stop).
With a half-H-bridge you can program it to have active braking (2-quadrant control). For instance using
synchronous-rectification mode the throttle will actively speed control both up and down. For this the
power supply needs to be a battery system as it has to absorb power, not just deliver it.
And should i use a mosfet driver or stick to logic mosfets? What do you think of using new or experimental transistors like GaN FETs? Maybe i should stick with the cheap h bridge modules? theres so many types of mosfets that i dont really know which one to use
For high power operation, always use gate driver chips, you need the switching efficiency and protection
they confer. Dead-time control is vital, so choose driver with this feature. Expect to blow up(*) a few MOSFETs
in testing even so, high power electronics is completely unforgiving of mistakes (!)