Go Down

Topic: PWM H-Bridge circuit (Read 29 times) previous topic - next topic

will_eng

Thank you i will change that and give it a try.

drspectro

I am pretty sure the power window motors I have seen for sale have been described as "limited duty cycle".  A reduced duty cycle would also reduce your transistor heating...  

jfunk

will_eng:
The TC4428 has 1 inverting output and 1 non-inverting output. Your schematic shows that you are switching both the HIGH/LOW side fets with the same output. This will create a temporary shoot through state each time you switch that side on/off (as the voltage in the 4428 changes, there will be time when both the N-channel and P-channel will be at around 6-8 volts which will cause both fets on the same side of the h-bridge to be partially open at the same time). Using PWM will multiply this problem. You should use 1 tc4428 to drive each side of the bridge. Input A is Inverting, you should drive the P-channel fets with this, Input B is non-inverting to drive the N-channel fets. You can then tie in both inputs into a single control pin for 2 wire operation. IE, turn on control A, and you will turn on the N-channel of the left side, and the P-channel of the right side (and vise versa).  I will post a schematic that I use when I can.

I am using the FQP47P06 P-channel fets with good success, but they also make a complementary N-channel with or without a logic level gate:

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=FQP50N06L-ND

jfunk

here is a rough schematic... minus the capacitors and such. This turns on opposite legs of the H-bridge on at the same time thereby avoiding the shoot through condition.

Edgars K?rkli?š

Here are some realy good materials - about Field effect transistors, their characteristics (current, thermal..utt.) and "H-bridge's" building with them....

First time on Arduino forum :P sorry for double post - I need 1 "normal" mesage, to be able to post links

Go Up