Forums

phase-shift pwm control with DSP

Started by Robert Imhoff October 29, 2004
Hello

I would like to inquire if anyone has attempted to implement a
phase-shift PWM control for a full-bridge DC-DC converter with the
built-in PWM module of the 56800E DSPs, or is that too complicated and
one should use a separate dedicated chip?

The idea is to phase-shift the PWM pulses to the two pairs of switches,
rather than varying the pulse widths ...
I guess if at all this should be done with timers rather than the pwm
module, but I would be grateful for any advice.

Many thanks!
Robert



hi Robert.you can acquire easily phase shift PWM
pulses via PWM module of the DSP.
biggest problem is to same dead time values for the
two leg of the full- bridge topology(acceptable for
most design).....

also you should consider resolotion of the PWM
pulses..in my opinion much then 100khz not possible
with DSP(56f8300E series)..because of the resolution
decreases...

isa

(ps:search old messages.i have asked same question
before) --- Robert Imhoff <> wrote:

> Hello
>
> I would like to inquire if anyone has attempted to
> implement a
> phase-shift PWM control for a full-bridge DC-DC
> converter with the
> built-in PWM module of the 56800E DSPs, or is that
> too complicated and
> one should use a separate dedicated chip?
>
> The idea is to phase-shift the PWM pulses to the two
> pairs of switches,
> rather than varying the pulse widths ...
> I guess if at all this should be done with timers
> rather than the pwm
> module, but I would be grateful for any advice.
>
> Many thanks!
> Robert

__________________________________




Robert and Isa,

I implemented a phase-shift PWM for a soft switch
DC-DC converter( AC - DC rectifier) by using
Freescale's MC56F8322/23. Because PWM module in
MC56F8322/23 has a special feature called " Asymmetric
PWM Output" ( see MC56F8300 peripheral user manual,
section 11.4.6, page 11-18). If you use this feature,
you can not only implement phase-shift PWM, but also
can have the differenet deadtime on each half bridge.
This is very important for reducing switching losses
between light load and heavy load. Unlike other DSPs
which need use software to update PWM duty cycle on
every half PWM cycle, 8323 PWM uses hardware to do
phase-shift PWM. It is a very useful feature for power
supply applications.
Charlie.

--- isa g <> wrote:

> hi Robert.you can acquire easily phase shift PWM
> pulses via PWM module of the DSP.
> biggest problem is to same dead time values for the
> two leg of the full- bridge topology(acceptable for
> most design).....
>
> also you should consider resolotion of the PWM
> pulses..in my opinion much then 100khz not possible
> with DSP(56f8300E series)..because of the resolution
> decreases...
>
> isa
>
> (ps:search old messages.i have asked same question
> before) > --- Robert Imhoff <> wrote:
>
> > Hello
> >
> > I would like to inquire if anyone has attempted to
> > implement a
> > phase-shift PWM control for a full-bridge DC-DC
> > converter with the
> > built-in PWM module of the 56800E DSPs, or is that
> > too complicated and
> > one should use a separate dedicated chip?
> >
> > The idea is to phase-shift the PWM pulses to the
> two
> > pairs of switches,
> > rather than varying the pulse widths ...
> > I guess if at all this should be done with timers
> > rather than the pwm
> > module, but I would be grateful for any advice.
> >
> > Many thanks!
> > Robert
> >
> >
>
> __________________________________

__________________________________




Hello Charlie,

Many thanks for your input!
I had been poring over that paragraph in the Peripheral User Manual but
had been thrown off by the "ISENS" option, thinking it would only work
with the current sense input pins, but now that you confirm this, it
becomes clear that one just has to set the ICC to "1" and then directly
control the up-count and down-count separately.

While on the subject of DC-DC conversion, would you have any advice on
what topology and switching methode would be best suited if one needs
to adapt to a rather wide range of input voltages?
The goal is to take the power coming from a wind turbine generator
ranging from 70 to 350 Volt DC (depending on the wind) and obtain a
steady 400 Volt DC to feed into an inverter. The current coming from
the generator would be around 3 Amp at 70 Volt up to 15 Amp at 350
Volt.
(This is straying off-topic, my apologies for that!)

Many thanks!
Robert On 03.11.2004, at 23:26, Charlie W wrote:

>
> Robert and Isa,
>
> I implemented a phase-shift PWM for a soft switch
> DC-DC converter( AC - DC rectifier) by using
> Freescale's MC56F8322/23. Because PWM module in
> MC56F8322/23 has a special feature called " Asymmetric
> PWM Output" ( see MC56F8300 peripheral user manual,
> section 11.4.6, page 11-18). If you use this feature,
> you can not only implement phase-shift PWM, but also
> can have the differenet deadtime on each half bridge.
> This is very important for reducing switching losses
> between light load and heavy load. Unlike other DSPs
> which need use software to update PWM duty cycle on
> every half PWM cycle, 8323 PWM uses hardware to do
> phase-shift PWM. It is a very useful feature for power
> supply applications. >
> Charlie.
>
> --- isa g <> wrote:
>
>> hi Robert.you can acquire easily phase shift PWM
>> pulses via PWM module of the DSP.
>> biggest problem is to same dead time values for the
>> two leg of the full- bridge topology(acceptable for
>> most design).....
>>
>> also you should consider resolotion of the PWM
>> pulses..in my opinion much then 100khz not possible
>> with DSP(56f8300E series)..because of the resolution
>> decreases...
>>
>> isa
>>
>> (ps:search old messages.i have asked same question
>> before)
>>
>>
>> --- Robert Imhoff <> wrote:
>>
>>> Hello
>>>
>>> I would like to inquire if anyone has attempted to
>>> implement a
>>> phase-shift PWM control for a full-bridge DC-DC
>>> converter with the
>>> built-in PWM module of the 56800E DSPs, or is that
>>> too complicated and
>>> one should use a separate dedicated chip?
>>>
>>> The idea is to phase-shift the PWM pulses to the
>> two
>>> pairs of switches,
>>> rather than varying the pulse widths ...
>>> I guess if at all this should be done with timers
>>> rather than the pwm
>>> module, but I would be grateful for any advice.
>>>
>>> Many thanks!
>>> Robert
>>>
>>>
>>
>>
>>
>>
>> __________________________________
>>
> >
>
> __________________________________ > _____________________________________
> Note: If you do a simple "reply" with your email client, only the
> author of this message will receive your answer. You need to do a
> "reply all" if you want your answer to be distributed to the entire
> group.
>
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>
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>






thanks Charlie!it is really good news....
i have written a little program producing phase
shift...i was supposing that i have to put same dead
time for two legs of the bridge....what is the way of
the different dead time for the two leg...(there is
just one dead time genarator for all PWMs)

isa
--- Charlie W <> wrote:

>
> Robert and Isa,
>
> I implemented a phase-shift PWM for a soft switch
> DC-DC converter( AC - DC rectifier) by using
> Freescale's MC56F8322/23. Because PWM module in
> MC56F8322/23 has a special feature called "
> Asymmetric
> PWM Output" ( see MC56F8300 peripheral user manual,
> section 11.4.6, page 11-18). If you use this
> feature,
> you can not only implement phase-shift PWM, but also
> can have the differenet deadtime on each half
> bridge.
> This is very important for reducing switching losses
> between light load and heavy load. Unlike other DSPs
> which need use software to update PWM duty cycle on
> every half PWM cycle, 8323 PWM uses hardware to do
> phase-shift PWM. It is a very useful feature for
> power
> supply applications. >
> Charlie.
>
> --- isa g <> wrote:
>
> > hi Robert.you can acquire easily phase shift PWM
> > pulses via PWM module of the DSP.
> > biggest problem is to same dead time values for
> the
> > two leg of the full- bridge topology(acceptable
> for
> > most design).....
> >
> > also you should consider resolotion of the PWM
> > pulses..in my opinion much then 100khz not
> possible
> > with DSP(56f8300E series)..because of the
> resolution
> > decreases...
> >
> > isa
> >
> > (ps:search old messages.i have asked same question
> > before)
> >
> >
> > --- Robert Imhoff <> wrote:
> >
> > > Hello
> > >
> > > I would like to inquire if anyone has attempted
> to
> > > implement a
> > > phase-shift PWM control for a full-bridge DC-DC
> > > converter with the
> > > built-in PWM module of the 56800E DSPs, or is
> that
> > > too complicated and
> > > one should use a separate dedicated chip?
> > >
> > > The idea is to phase-shift the PWM pulses to the
> > two
> > > pairs of switches,
> > > rather than varying the pulse widths ...
> > > I guess if at all this should be done with
> timers
> > > rather than the pwm
> > > module, but I would be grateful for any advice.
> > >
> > > Many thanks!
> > > Robert
> > >
> > >
> >
> >
> >
> >
> > __________________________________
> >
> >
>
> __________________________________ >
>
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>
> _____________________________________
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> client, only the author of this message will receive
> your answer. You need to do a "reply all" if you
> want your answer to be distributed to the entire
> group.
>
> _____________________________________
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>
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>
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__________________________________



Robert,

You got it. Set ICCx to "1: you can get true
phase-shift PWM. Do you want isolated DC voltage
boost? If yes, phase shift DC-DC converter is a good
topolog because it is a soft switch forward converter
which uses smaller isolation transformer. You should
put DSP on secondary side in order to eliminate costly
analog isolation. You can use one DSP to control both
DC-DC converter and inverter.

Attached topolog is good for non-isolation converter.
If you have any other questions, I can find someone in
Freescale ( Motorola SPS) who specializes Digital
Power to talk to you
Thansk!

Charlie
--- Robert Imhoff <> wrote:

>
> Hello Charlie,
>
> Many thanks for your input!
> I had been poring over that paragraph in the
> Peripheral User Manual but
> had been thrown off by the "ISENS" option, thinking
> it would only work
> with the current sense input pins, but now that you
> confirm this, it
> becomes clear that one just has to set the ICC to
> "1" and then directly
> control the up-count and down-count separately.
>
> While on the subject of DC-DC conversion, would you
> have any advice on
> what topology and switching methode would be best
> suited if one needs
> to adapt to a rather wide range of input voltages?
> The goal is to take the power coming from a wind
> turbine generator
> ranging from 70 to 350 Volt DC (depending on the
> wind) and obtain a
> steady 400 Volt DC to feed into an inverter. The
> current coming from
> the generator would be around 3 Amp at 70 Volt up to
> 15 Amp at 350
> Volt.
> (This is straying off-topic, my apologies for that!)
>
> Many thanks!
> Robert > On 03.11.2004, at 23:26, Charlie W wrote:
>
> >
> > Robert and Isa,
> >
> > I implemented a phase-shift PWM for a soft switch
> > DC-DC converter( AC - DC rectifier) by using
> > Freescale's MC56F8322/23. Because PWM module in
> > MC56F8322/23 has a special feature called "
> Asymmetric
> > PWM Output" ( see MC56F8300 peripheral user
> manual,
> > section 11.4.6, page 11-18). If you use this
> feature,
> > you can not only implement phase-shift PWM, but
> also
> > can have the differenet deadtime on each half
> bridge.
> > This is very important for reducing switching
> losses
> > between light load and heavy load. Unlike other
> DSPs
> > which need use software to update PWM duty cycle
> on
> > every half PWM cycle, 8323 PWM uses hardware to do
> > phase-shift PWM. It is a very useful feature for
> power
> > supply applications.
> >
> >
> >
> > Charlie.
> >
> > --- isa g <> wrote:
> >
> >> hi Robert.you can acquire easily phase shift PWM
> >> pulses via PWM module of the DSP.
> >> biggest problem is to same dead time values for
> the
> >> two leg of the full- bridge topology(acceptable
> for
> >> most design).....
> >>
> >> also you should consider resolotion of the PWM
> >> pulses..in my opinion much then 100khz not
> possible
> >> with DSP(56f8300E series)..because of the
> resolution
> >> decreases...
> >>
> >> isa
> >>
> >> (ps:search old messages.i have asked same
> question
> >> before)
> >>
> >>
> >> --- Robert Imhoff <> wrote:
> >>
> >>> Hello
> >>>
> >>> I would like to inquire if anyone has attempted
> to
> >>> implement a
> >>> phase-shift PWM control for a full-bridge DC-DC
> >>> converter with the
> >>> built-in PWM module of the 56800E DSPs, or is
> that
> >>> too complicated and
> >>> one should use a separate dedicated chip?
> >>>
> >>> The idea is to phase-shift the PWM pulses to the
> >> two
> >>> pairs of switches,
> >>> rather than varying the pulse widths ...
> >>> I guess if at all this should be done with
> timers
> >>> rather than the pwm
> >>> module, but I would be grateful for any advice.
> >>>
> >>> Many thanks!
> >>> Robert
> >>>
> >>>
> >>
> >>
> >>
> >>
> >> __________________________________
> >>
> >>
> >
> >
> >
> >
> > __________________________________
> >
> >
> >
> >
> >
> > _____________________________________
> > Note: If you do a simple "reply" with your email
> client, only the
> > author of this message will receive your answer.
> You need to do a
> > "reply all" if you want your answer to be
> distributed to the entire
> > group.
> >
> > _____________________________________
> > About this discussion group:
> >
> > To Join:
> >
> > To Post:
> >
> > To Leave:
> >
> > Archives:
> http://www.yahoogroups.com/group/motoroladsp
> >
> > More Groups: http://www.dsprelated.com/groups.php3
> >
> > Yahoo! Groups Links
> >
> >
> >
> >
> >
> >
>

__________________________________



Attachment (not stored)
Voltage boost.pdf
Type: application/pdf

Isa,

There is a little bit trick to do this. Use PWM0 and
PWM1 to control one half bridge. Use PWM 2 and PWM5 to
control another half brideg. So phase shift between
PWM2 and PWM5 will add or subtract an addition
deadtime to the one generated by deadtime register.

Charlie

--- isa g <> wrote:

>
>
> thanks Charlie!it is really good news....
> i have written a little program producing phase
> shift...i was supposing that i have to put same dead
> time for two legs of the bridge....what is the way
> of
> the different dead time for the two leg...(there is
> just one dead time genarator for all PWMs)
>
> isa >
> --- Charlie W <> wrote:
>
> >
> > Robert and Isa,
> >
> > I implemented a phase-shift PWM for a soft switch
> > DC-DC converter( AC - DC rectifier) by using
> > Freescale's MC56F8322/23. Because PWM module in
> > MC56F8322/23 has a special feature called "
> > Asymmetric
> > PWM Output" ( see MC56F8300 peripheral user
> manual,
> > section 11.4.6, page 11-18). If you use this
> > feature,
> > you can not only implement phase-shift PWM, but
> also
> > can have the differenet deadtime on each half
> > bridge.
> > This is very important for reducing switching
> losses
> > between light load and heavy load. Unlike other
> DSPs
> > which need use software to update PWM duty cycle
> on
> > every half PWM cycle, 8323 PWM uses hardware to do
> > phase-shift PWM. It is a very useful feature for
> > power
> > supply applications.
> >
> >
> >
> > Charlie.
> >
> > --- isa g <> wrote:
> >
> > > hi Robert.you can acquire easily phase shift PWM
> > > pulses via PWM module of the DSP.
> > > biggest problem is to same dead time values for
> > the
> > > two leg of the full- bridge topology(acceptable
> > for
> > > most design).....
> > >
> > > also you should consider resolotion of the PWM
> > > pulses..in my opinion much then 100khz not
> > possible
> > > with DSP(56f8300E series)..because of the
> > resolution
> > > decreases...
> > >
> > > isa
> > >
> > > (ps:search old messages.i have asked same
> question
> > > before)
> > >
> > >
> > > --- Robert Imhoff <> wrote:
> > >
> > > > Hello
> > > >
> > > > I would like to inquire if anyone has
> attempted
> > to
> > > > implement a
> > > > phase-shift PWM control for a full-bridge
> DC-DC
> > > > converter with the
> > > > built-in PWM module of the 56800E DSPs, or is
> > that
> > > > too complicated and
> > > > one should use a separate dedicated chip?
> > > >
> > > > The idea is to phase-shift the PWM pulses to
> the
> > > two
> > > > pairs of switches,
> > > > rather than varying the pulse widths ...
> > > > I guess if at all this should be done with
> > timers
> > > > rather than the pwm
> > > > module, but I would be grateful for any
> advice.
> > > >
> > > > Many thanks!
> > > > Robert
> > > >
> > > >
> > >
> > >
> > >
> > >
> > > __________________________________
> > >
> > >
> >
> >
> >
> >
> > __________________________________
> >
> >
> >
> >
> > ------------------------ Yahoo! Groups Sponsor
> > --------------------~-->
> > $9.95 domain names from Yahoo!. Register anything.
> >
>
http://us.click.yahoo.com/J8kdrA/y20IAA/yQLSAA/PNArlB/TM
> >
>
--------------------------------~->
> >
> >
> > _____________________________________
> > Note: If you do a simple "reply" with your email
> > client, only the author of this message will
> receive
> > your answer. You need to do a "reply all" if you
> > want your answer to be distributed to the entire
> > group.
> >
> > _____________________________________
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> >
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> >
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> >
> >
> >
> >
> >
> >
> >
> >
>
> __________________________________ >
>
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>
--------------------------------~->
>
>
> _____________________________________
> Note: If you do a simple "reply" with your email
> client, only the author of this message will receive
> your answer. You need to do a "reply all" if you
> want your answer to be distributed to the entire
> group.
>
> _____________________________________
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__________________________________


Just wondering if anyone has had any experience with getting a serial port program working, something on SCI 0 or 1.. And if anyone has any ideas?

Currently I’m working with the DSP56858 on Codewarrior 6.1 with the SDK. Would like to use interrupts and dma transfers, but at the moment, just want to get polling working first, so at least I know it works.. Have read the manual but it is very unclear on exactly what steps you need to do, to do anything J

 

If anyone can help, thanks J

 

Rajesh Singh

r...@shockdesign.com.au

www.shockdesign.com.au