EVALPWD13F60 PWD13F60 only output pulses and not a permanent output

JESQU · ‎2018-11-28

Hi Im using EVALPWD13F60

VS = 100V

VCC = 8V

HINx and LINx = 3.3v

GND = I connected the GND of my 100v supply, the microcontroller GND and the 8v supply GND.

Output 1 to Output 2 = 5k resistor

The problem that I'm facing is that I can only get pulses of around 10ms when I put HINx + LINy to High. These pulses are of 100V. They're only pulses even when I keep the inputs at high.

What I've noticed is that if I put HINx and LINy input to high at the same time I don't even get a pulse, I have to put first LINy to high then HINx to high then I get this pulse. But I cannot get a permanent output.

I've measured and my 8v is constant, also the 3.3v and the 100V. On the attached photo you can see the 100V input on blue and the PWD output on Yellow.

Any clue about what's happening' Thanks!!!

fabbri.fabio · ‎2019-02-13

To properly turn on high side MOSFET (the one drive by HIN), the bootstrap capacitor (the one between BOOT and OUT, supplying the floating structure) shall be charged first.

To charge the capacitor thru the integrated bootstrap diode, a low resistance path shall be placed between OUT to GND. This is normally accomplished in these bootstrap architectures by turning on the low side MOSFET asserting the LIN input for the time required to charge the capacitor.

This is the reason why you need to assert the LIN pin before asserting HIN pin for proper operation.

For example, with the integrated diode and the capacitor used in the eval board (220 nF) a time in the range of 100us is sufficient. If you need a longer high side turn-on time you should consider increasing the bootstrap capacitor and eventually increasing the 8V supply to 15V.

The bootstrap diode architecture is the cheapest and simpler approach to supply the floating structure, used on most of high voltage motor drivers. But if you need to keep the high side MOS indefinitely high (duty cycle 100%), the bootstrap architecture is not suitable and you have to use a different approach. If a duty cycle <100% is possible, you can consider recharging the bootstrap capacitor periodically turning on the low side MOSFET.