Not sure if there is quick answer but is there simple way to do bidirectional power supply (power supply plus DC load)? This application would be small, maybe no more than 10 W or 20 W DC load. This question came up recently and I can't seem to find my copy of Art of Electronics and I don't remember if such a topic is even covered.

Scot

On 24/7/22 12:26, Scot Bohnenstiehl wrote:
> Not sure if there is quick answer but is there simple way to do bidirectional power supply (power supply plus DC load)? This application would be small, maybe no more than 10 W or 20 W DC load. This question came up recently and I can't seem to find my copy of Art of Electronics and I don't remember if such a topic is even covered.

A 4-quadrant motor driver can source or sink (regenerate) power in
either polarity.

The other thing to look for is a SMU (Source Measurement Unit), a piece
of lab equipment.

Clifford Heath

søndag den 24. juli 2022 kl. 05.20.46 UTC+2 skrev bill....@ieee.org:
> On Sunday, July 24, 2022 at 12:26:29 PM UTC+10, Scot Bohnenstiehl wrote:
> > Not sure if there is quick answer but is there simple way to do bidirectional power supply (power supply plus DC load)? This application would be small, maybe no more than 10 W or 20 W DC load. This question came up recently and I can't seem to find my copy of Art of Electronics and I don't remember if such a topic is even covered.
> If you hook up one end of an inductor to a positive power supply with a P=channel power MOSFET, and the same end to ground with an N-channel power MOSFET and alternately turn one and then other other on (but not both at the same time) the voltage at the other end of the inductor will be some fraction of the output voltage of the positive power supply determined by the mark-to-space ratio of drive wave forms - if both are on for 50% of the time it will be half.
>
> This is independent of the direction of the current flow through the inductor.
>
> Obviously the inductor must be able handle the current flowing through it (not burn out or saturate) and so must the MOSFET switches, and there's going to be a ripple element in the current which you may need to filter out.
>
> Single chip microcontrollers can generate the switching waveforms - mostly you will need a driver chip to boost the output signal to the voltage and currents the MOSFET's need to switch fast enough to do the job - and most single chip micros come with an A/D converter that will let you monitor what's going on, and adapt the drive waveforms to create the effect you want.
>

that just pumps the current into the input supply, so that must be able to source and sink

søndag den 24. juli 2022 kl. 04.26.29 UTC+2 skrev Scot Bohnenstiehl:
> Not sure if there is quick answer but is there simple way to do bidirectional power supply (power supply plus DC load)? This application would be small, maybe no more than 10 W or 20 W DC load. This question came up recently and I can't seem to find my copy of Art of Electronics and I don't remember if such a topic is even covered.
>

how should it behave when loading? constant current, constant resistance,constant voltage, constant power, or some combination

On Sun, 24 Jul 2022 16:36:00 +1000, Clifford Heath
<no_spam@please.net> wrote:

>On 24/7/22 12:26, Scot Bohnenstiehl wrote:
>> Not sure if there is quick answer but is there simple way to do bidirectional power supply (power supply plus DC load)? This application would be small, maybe no more than 10 W or 20 W DC load. This question came up recently and I can't seem to find my copy of Art of Electronics and I don't remember if such a topic is even covered.
>
>A 4-quadrant motor driver can source or sink (regenerate) power in
>either polarity.
>
>The other thing to look for is a SMU (Source Measurement Unit), a piece
>of lab equipment.
>
>Clifford Heath

Kepco makes BOP, bipolar operational, power supplies.

The brute force way to do this is a power opamp with suitable supply
rails, depending on the voltages you want. Like, an OPA547 and a
trimpot.

I'm designing both programmable power supplies and programmable loads
now, but haven't considered doing both in one board.

Any load has to get rid of incoming power. A linear circuit has to
dump it locally, into heat sinks. A switcher will push it uphill into
its power supply, which has to tolerate being back-driven.

On Sunday, 24 July 2022 at 07:21:31 UTC-7, jla...@highlandsniptechnology.com wrote:
...
>
> Any load has to get rid of incoming power. A linear circuit has to
> dump it locally, into heat sinks. A switcher will push it uphill into
> its power supply, which has to tolerate being back-driven.

Regenerative electronic loads are getting common for high-power testing of batteries and motors in electric vehicle development.

https://www.eapowered.com/products/el-elr-electronic-loads/?utm_medium=cpc&utm_source=google&utm_campaign=PDCT-ELR&utm_adgroup=%7Badgroup%7D&utm_content=002-ETA&utm_term=regenerative%20dc%20electronic%20load&gclid=Cj0KCQjw2_OWBhDqARIsAAUNTTGz-nscx1sfixajgzlWEmJqrsfIqOtwwyFtcBRf2h4sKNEYt02MTJ4aAo8IEALw_wcB

https://dynesystems.com/products/drives/

kw

On Sun, 24 Jul 2022 05:49:19 -0700 (PDT), Lasse Langwadt Christensen
<langwadt@fonz.dk> wrote:

>søndag den 24. juli 2022 kl. 05.20.46 UTC+2 skrev bill....@ieee.org:
>> On Sunday, July 24, 2022 at 12:26:29 PM UTC+10, Scot Bohnenstiehl wrote:
>> > Not sure if there is quick answer but is there simple way to do bidirectional power supply (power supply plus DC load)? This application would be small, maybe no more than 10 W or 20 W DC load. This question came up recently and I can't seem to find my copy of Art of Electronics and I don't remember if such a topic is even covered.
>> If you hook up one end of an inductor to a positive power supply with a P=channel power MOSFET, and the same end to ground with an N-channel power MOSFET and alternately turn one and then other other on (but not both at the same time) the voltage at the other end of the inductor will be some fraction of the output voltage of the positive power supply determined by the mark-to-space ratio of drive wave forms - if both are on for 50% of the time it will be half.
>>
>> This is independent of the direction of the current flow through the inductor.
>>
>> Obviously the inductor must be able handle the current flowing through it (not burn out or saturate) and so must the MOSFET switches, and there's going to be a ripple element in the current which you may need to filter out.
>>
>> Single chip microcontrollers can generate the switching waveforms - mostly you will need a driver chip to boost the output signal to the voltage and currents the MOSFET's need to switch fast enough to do the job - and most single chip micros come with an A/D converter that will let you monitor what's going on, and adapt the drive waveforms to create the effect you want.
>>
>
>that just pumps the current into the input supply, so that must be able to source and sink

Yes. Conservation Of Energy can be annoying.

On 7/23/2022 10:26 PM, Scot Bohnenstiehl wrote:
> Not sure if there is quick answer but is there simple way to do bidirectional power supply (power supply plus DC load)? This application would be small, maybe no more than 10 W or 20 W DC load. This question came up recently and I can't seem to find my copy of Art of Electronics and I don't remember if such a topic is even covered.
>
> Scot

The answer to the question as posed is yes.
Have the output on signal (level, switch, whatever) of the power
supply energize a relay. Have the relay switch between the load
function when de-energized and the supply function when energized.
But I don't think that's what you want. I think you need to supply
more "what I want" criteria.

Ed

On Sat, 23 Jul 2022 19:26:26 -0700 (PDT), Scot Bohnenstiehl
<scotbohnenstiehl@gmail.com> wrote:

>Not sure if there is quick answer but is there simple way to do bidirectional power supply (power supply plus DC load)? This application would be small, maybe no more than 10 W or 20 W DC load. This question came up recently and I can't seem to find my copy of Art of Electronics and I don't remember if such a topic is even covered.
>
>Scot

Do you mean a power supply that would be bi-diretional had it not used
a non-synchronous rectifier ?

Many architectures can be BD if you use a SR.

boB

On 7/23/2022 10:26 PM, Scot Bohnenstiehl wrote:
> Not sure if there is quick answer but is there simple way to do bidirectional power supply (power supply plus DC load)? This application would be small, maybe no more than 10 W or 20 W DC load. This question came up recently and I can't seem to find my copy of Art of Electronics and I don't remember if such a topic is even covered.
>
> Scot

For modest powers the synchronous Cuk converter can operate
bidirectionally with few not many modifications:

<https://www.researchgate.net/figure/Bidirectional-Cuk-converter-structure_fig1_236153344>

The cap can be split and a transformer added to isolate it and avoid the
polarity inversion on the output if needed. The transformer doesn't need
to store energy so it doesn't need to be large

On Sunday, 31 July 2022 at 11:41:27 UTC-7, bitrex wrote:
> On 7/23/2022 10:26 PM, Scot Bohnenstiehl wrote:
> > Not sure if there is quick answer but is there simple way to do bidirectional power supply (power supply plus DC load)? This application would be small, maybe no more than 10 W or 20 W DC load. This question came up recently and I can't seem to find my copy of Art of Electronics and I don't remember if such a topic is even covered.
> >
> > Scot
> For modest powers the synchronous Cuk converter can operate
> bidirectionally with few not many modifications:
>
> <https://www.researchgate.net/figure/Bidirectional-Cuk-converter-structure_fig1_236153344>
>
> The cap can be split and a transformer added to isolate it and avoid the
> polarity inversion on the output if needed. The transformer doesn't need
> to store energy so it doesn't need to be large

Many switching power supply configurations can operate bidirectionally if required.

The Prius (and the other Toyota hybrids) has a buck/boost converter from the 200V battery to the variable voltage main bus (200-650V) to feed the motor drivers. It can transfer up to 30kW in the Prius.

In an AC powered supply the issue is that you also need a bidirectional AC to DC converter. It is not enough just to extract power from the load and provide it as DC - it needs to be converted to 50/60Hz AC and fed back to the power source.

kw

On Sun, 31 Jul 2022 18:41:03 -0700 (PDT), "ke...@kjwdesigns.com"
<keith@kjwdesigns.com> wrote:

>On Sunday, 31 July 2022 at 11:41:27 UTC-7, bitrex wrote:
>> On 7/23/2022 10:26 PM, Scot Bohnenstiehl wrote:
>> > Not sure if there is quick answer but is there simple way to do bidirectional power supply (power supply plus DC load)? This application would be small, maybe no more than 10 W or 20 W DC load. This question came up recently and I can't seem to find my copy of Art of Electronics and I don't remember if such a topic is even covered.
>> >
>> > Scot
>> For modest powers the synchronous Cuk converter can operate
>> bidirectionally with few not many modifications:
>>
>> <https://www.researchgate.net/figure/Bidirectional-Cuk-converter-structure_fig1_236153344>
>>
>> The cap can be split and a transformer added to isolate it and avoid the
>> polarity inversion on the output if needed. The transformer doesn't need
>> to store energy so it doesn't need to be large
>
>Many switching power supply configurations can operate bidirectionally if required.
>
>The Prius (and the other Toyota hybrids) has a buck/boost converter from the 200V battery to the variable voltage main bus (200-650V) to feed the motor drivers. It can transfer up to 30kW in the Prius.
>
>In an AC powered supply the issue is that you also need a bidirectional AC to DC converter. It is not enough just to extract power from the load and provide it as DC - it needs to be converted to 50/60Hz AC and fed back to the power source.
>
>kw

A synchronous buck supply is interesting. Suppose we are driving a
customer's gadget and he has a lot of input capacitance. Suppose we
are outputting 24 volts and suddenly get a request to output 5. Our
loop sees the voltage error and starts cranking down the duty cycle,
which starts pumping energy uphill into our top power rail. That
back-charges our supply. But only for a little while, until the fb
loop winds us down to zero duty cycle = infinite reverse step-up.

Given that, we can probably absorb the zot of reverse energy in a
reasonable cap, with a transzorb for luck. If the lower fet doesn't
explode.

The right-half-plane dilemma works to our advantage. Fun.