Hi all,
I read that running a new HPWM command resets the internal timer and may cause glitches if already running a HPWM output. I am running a Picaxe 20x2.
I am running a synchronous buck DC converter, and would like it to change between Buck and Synchronous Buck modes on the fly. The output is charging a battery.
A high side mosfet is connected to pin C.5 and a low side Mosfet to pin C.4 via a half bridge gate driver IC.
I am using:
SETFREQ M64
HPWM 1, pwmHHHH, 1, 249, DutyCycle
which runs the converter in Half bridge synchronous conversion mode @ 64khz.
My application benefits from running the converter in non-synchronous mode now and then (may need to change every few seconds). Which means I need to issue a new HPWM 0 or 1* command. Now I know from experience that if the low side Mosfet stays on for any amount of time greater than say a millisecond the Mosfet will short the battery and destroy the converter. So at the moment I am being cautious and disabling pwm (HPWM off) for (300 / 8) milliseconds with a Pause 300 command before issuing this command to run in single mode (Buck) conversion:
HPWM 0, pwmHHHH, %0001, 249, DutyCycle
My Question is, do you think it is actually necessary to use the HPWM OFF command and Pauses in this scenario, or do you think the momentary reset of the timer that happens with another HPWM command shouldn't cause enough of an output PWM waveform corruption that would keep the low side signal on for any appreciable time (>1mS) to warrant it and I should just run the "HPWM 0, pwmHHHH, %0001, 249, DutyCycle" command while it is already switching.
I will test this personally if no one else has experience with this but i'm not keen on blowing up expensive Mosfets when someone else may have experience in this area
Cheers,
Adrian
I read that running a new HPWM command resets the internal timer and may cause glitches if already running a HPWM output. I am running a Picaxe 20x2.
I am running a synchronous buck DC converter, and would like it to change between Buck and Synchronous Buck modes on the fly. The output is charging a battery.
A high side mosfet is connected to pin C.5 and a low side Mosfet to pin C.4 via a half bridge gate driver IC.
I am using:
SETFREQ M64
HPWM 1, pwmHHHH, 1, 249, DutyCycle
which runs the converter in Half bridge synchronous conversion mode @ 64khz.
My application benefits from running the converter in non-synchronous mode now and then (may need to change every few seconds). Which means I need to issue a new HPWM 0 or 1* command. Now I know from experience that if the low side Mosfet stays on for any amount of time greater than say a millisecond the Mosfet will short the battery and destroy the converter. So at the moment I am being cautious and disabling pwm (HPWM off) for (300 / 8) milliseconds with a Pause 300 command before issuing this command to run in single mode (Buck) conversion:
HPWM 0, pwmHHHH, %0001, 249, DutyCycle
My Question is, do you think it is actually necessary to use the HPWM OFF command and Pauses in this scenario, or do you think the momentary reset of the timer that happens with another HPWM command shouldn't cause enough of an output PWM waveform corruption that would keep the low side signal on for any appreciable time (>1mS) to warrant it and I should just run the "HPWM 0, pwmHHHH, %0001, 249, DutyCycle" command while it is already switching.
I will test this personally if no one else has experience with this but i'm not keen on blowing up expensive Mosfets when someone else may have experience in this area
Cheers,
Adrian