Re: H-BRIDGE and DC-SERVO DRIVE improvement help!

thanks dave for such an helpful information
oh pc cant generate such a high frequency PWM!! i have plan to
generate this PWM signal through use of some comparator chips some
triangular wave generators made up of opamps.
I' havent done that yet but i will do that. there is information
available on net for PWM generators for dc motor:
http://www.solorb.com/elect/solarcirc/pwm1/

or maybe i will use some 8051 compatible microconroller to do this
PWM stuf.
regards
@sim,

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "turbulatordude"
<davemucha@j...> wrote:

> check out,
>
> http://www.armory.com/~rstevew/Public/Motors/H-Bridges/Blanchard/h-
> bridge.htm
>
> I'm not sure about the speed of switching for the transistors, but

it

> appears that you are not addressing any back EMF unless it is

handled

> by the darlintons.
>
> and it if I am not mistaken, MOSFET's will be easy to size for the
> voltage and amps.
>
> Also, what software are you using ? and what dwell time do you have
> for the on time and off time between pulses ?
>
> Dave
>
>
>
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Asim Khan" <asimtec@y...>
> wrote:
> > Hi forum:
> >
> > I had build the H-Bridge by looking at this following
> > design:
> >
> > http://cet.ssu.portsmouth.oh.us/~jlindeman/h-bridge/hbridge.html
> >
> > This above design uses PNP and NPN DARLINTON BJTS TIP12X series

in

> > its
> > design. This design works ok as far as the switching frequesny
> > applied is no more than 3~4Khz. I had put it in an application
> where
> > the PWM freqyncy is 11.7KHz. at high frequenies this design

fails,

> > burning transistors.
> > I had tested this desin in my lab and i found that when you drive
> the
> > left PNP darlinton and the right NPN darlinton by appliying the

PWM

> > signal at left side then the right side PNP darlinton starts
> getting
> > heat up, when the PWM frequency is 10~20Khz, and eventually the
> right
> > side PNP darlinton blasts!!
> > It seems the the right side PNP darlinton recieves the driving
> pulses
> > when it should not get driven. since in an hbridge at a single
> moment
> > there only two transistors should conduct, and in my case 3
> > transitors starts conducting which causes so much high current
> > through the transitor.
> > same happens when i apply the PWM signal at right hand side, but
> this
> > time the left side PNP darlinton starts getting heatup
> >
> > I had also tried MJ11032(NPN) AND MJ11033(PNP) darlinton high

speed

> > switch transistors(specially designed for hi amp inductive load
> > swithching) with 50AMP continuos current capability in my
> > circuit. but observations were the same.
> > I need to design a professional dc-servo drive which can operate
> upto
> > 80V and can deleiver around 20-30AMP.
> >
> > please suggest what changes should i made in this schematic so

that

> > i can use this H-BRIDGE design for HI frequency PWM signals and

for

> > hi amp loads !
> > i request everyone to please suggest me any designs and or links
> > best regards
> > @sim