IR2110 - Half bridge waveform

Thread Starter

Coucou80

Joined Apr 7, 2018
16
I designed a circuit to power a little dc motor through the use of Half-bridge powered by a ir2110 ic.
The good news is on the scope I see the MOSFET gates opening at opposite timing (DC - from ~0 to 12 volt for LO and DC - from ~ 0 to + Vs + 12 Volts for HO).
So here is my question. At load location what should the waveform look like? AC or Pulse DC ?
 

MrSalts

Joined Apr 2, 2020
613
I designed a circuit to power a little dc motor through the use of Half-bridge powered by a ir2110 ic.
The good news is on the scope I see the MOSFET gatea opening at opposite timing (DC - from ~0 to 12 volt for LO and DC - from ~ 0 to + Vs + 12 Volts for HO).
So here is my question. At load location what should the waveform look like? AC or Pulse DC ?
Assuming your switching speed (changing directions) is much slower than the start-up time of the motor, you'll see essentially a square wave. There will be some rounding of the leading edge of the wave as the motor changes direction.

If you change direction so quickly that the motor is not up to speed before switching direction, you will see some type of triangle wave. The faster you switch, the lower the peak-to-peak voltage you will see on your scope (assuming to "switching" means your input swings enough to turn off the N-channel and turns on the P-channel in one flip). If a switching event can stop at zero-volts and leave both N and P channels off, then your waveform will look more ie a sawtooth at high switching speeds.
 

Thread Starter

Coucou80

Joined Apr 7, 2018
16
Thank you all for the interest in my post. I'm impressed with the numerous responses I got and the quality of the observation received in such a quick time :)
To get back to topic, if we look at this video (which has nothing to do with my particular project) : Ultrasonic Mist Maker || DIY or Buy - YouTube from 5:10 to 5:18 the author mentions that Half-Bridges produces an AC signal and this is what is confusing me .... I dont see how a Half-Bridge can produce an AC signal unless "maybe" if coupled with a transformer. H-Bridge would ba a totaly different beast though and it is not what I'm attempting to construct.

In my mind a square wave is AC signal as it alternates from positive to negative in a "square wave maner". While pulse DC signal is not crossing the 0volt line. Author seems to explain that the signal crosses the 0 line with the use of a half-bridge.
 
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