CV/CC synchronous buck -- do they exist?!...

[Piotr Wyderski]

boB wrote:

Typically, voltage feedback is given back to the chip but you could
certainly send it a current feedback signal or combination with extra
ciruitry.

The point is to avoid the circuitry. I was used to the belief that CC/CV
is a pretty standard application for a switcher and was using that every
now and then back in the UCC384x days.

Now it looks like the CC mode capability is an eccentric need, let alone
CC/CV. Sending the current feedback signal to the part might end up in
an endless reset sequence, as most of the newest controllers check if
the FB voltage is above some internal threshold and turn off if not.
One is either dead in the water or is about to start a peek-a-boo game
with the IC designer. An uphill battle, given the fact that he is being
paid full-time for making your life harder.

I am afraid that the 0 to VREF FB days are gone.

Best regards, Piotr

 

[Piotr Wyderski]

boB wrote:

Typically, voltage feedback is given back to the chip but you could
certainly send it a current feedback signal or combination with extra
ciruitry.

The point is to avoid the circuitry. I was used to the belief that CC/CV
is a pretty standard application for a switcher and was using that every
now and then back in the UCC384x days.

Now it looks like the CC mode capability is an eccentric need, let alone
CC/CV. Sending the current feedback signal to the part might end up in
an endless reset sequence, as most of the newest controllers check if
the FB voltage is above some internal threshold and turn off if not.
One is either dead in the water or is about to start a peek-a-boo game
with the IC designer. An uphill battle, given the fact that he is being
paid full-time for making your life harder.

I am afraid that the 0 to VREF FB days are gone.

Best regards, Piotr

 

[sea moss]

On Sunday, July 19, 2020 at 3:21:01 PM UTC-7, Piotr Wyderski wrote:

boB wrote:

Typically, voltage feedback is given back to the chip but you could
certainly send it a current feedback signal or combination with extra
ciruitry.

The point is to avoid the circuitry. I was used to the belief that CC/CV
is a pretty standard application for a switcher and was using that every
now and then back in the UCC384x days.

Now it looks like the CC mode capability is an eccentric need, let alone
CC/CV. Sending the current feedback signal to the part might end up in
an endless reset sequence, as most of the newest controllers check if
the FB voltage is above some internal threshold and turn off if not.
One is either dead in the water or is about to start a peek-a-boo game
with the IC designer. An uphill battle, given the fact that he is being
paid full-time for making your life harder.

I am afraid that the 0 to VREF FB days are gone.

Best regards, Piotr

If you inject a little current into the FB pin, the chip will still regulate the FB pin at its normal voltage. The output voltage will sag to compensate. It works really well as long as you keep the extra current-derived loop slower than the normal loop; 10x slower works well. I\'m using this technique in one of my current designs and you can drive into a short just fine..

 

[sea moss]

On Sunday, July 19, 2020 at 3:21:01 PM UTC-7, Piotr Wyderski wrote:

boB wrote:

Typically, voltage feedback is given back to the chip but you could
certainly send it a current feedback signal or combination with extra
ciruitry.

The point is to avoid the circuitry. I was used to the belief that CC/CV
is a pretty standard application for a switcher and was using that every
now and then back in the UCC384x days.

Now it looks like the CC mode capability is an eccentric need, let alone
CC/CV. Sending the current feedback signal to the part might end up in
an endless reset sequence, as most of the newest controllers check if
the FB voltage is above some internal threshold and turn off if not.
One is either dead in the water or is about to start a peek-a-boo game
with the IC designer. An uphill battle, given the fact that he is being
paid full-time for making your life harder.

I am afraid that the 0 to VREF FB days are gone.

Best regards, Piotr

If you inject a little current into the FB pin, the chip will still regulate the FB pin at its normal voltage. The output voltage will sag to compensate. It works really well as long as you keep the extra current-derived loop slower than the normal loop; 10x slower works well. I\'m using this technique in one of my current designs and you can drive into a short just fine..

 

[sea moss]

On Sunday, July 19, 2020 at 3:21:01 PM UTC-7, Piotr Wyderski wrote:

boB wrote:

Typically, voltage feedback is given back to the chip but you could
certainly send it a current feedback signal or combination with extra
ciruitry.

The point is to avoid the circuitry. I was used to the belief that CC/CV
is a pretty standard application for a switcher and was using that every
now and then back in the UCC384x days.

Now it looks like the CC mode capability is an eccentric need, let alone
CC/CV. Sending the current feedback signal to the part might end up in
an endless reset sequence, as most of the newest controllers check if
the FB voltage is above some internal threshold and turn off if not.
One is either dead in the water or is about to start a peek-a-boo game
with the IC designer. An uphill battle, given the fact that he is being
paid full-time for making your life harder.

I am afraid that the 0 to VREF FB days are gone.

Best regards, Piotr

If you inject a little current into the FB pin, the chip will still regulate the FB pin at its normal voltage. The output voltage will sag to compensate. It works really well as long as you keep the extra current-derived loop slower than the normal loop; 10x slower works well. I\'m using this technique in one of my current designs and you can drive into a short just fine..

 

[Piotr Wyderski]

sea moss wrote:

> If you inject a little current into the FB pin, the chip will still regulate the FB pin at its normal voltage. The output voltage will sag to compensate. It works really well as long as you keep the extra current-derived loop slower than the normal loop; 10x slower works well. I\'m using this technique in one of my current designs and you can drive into a short just fine.

The plan for now is to check if the TPS54428 wants to mate with the
INA199. According to the datasheet the controller, there should be no
hiccup. I will share the results in due course.

Best regards, Piotr

 

[Piotr Wyderski]

sea moss wrote:

> If you inject a little current into the FB pin, the chip will still regulate the FB pin at its normal voltage. The output voltage will sag to compensate. It works really well as long as you keep the extra current-derived loop slower than the normal loop; 10x slower works well. I\'m using this technique in one of my current designs and you can drive into a short just fine.

The plan for now is to check if the TPS54428 wants to mate with the
INA199. According to the datasheet the controller, there should be no
hiccup. I will share the results in due course.

Best regards, Piotr

 

[Piotr Wyderski]

sea moss wrote:

> If you inject a little current into the FB pin, the chip will still regulate the FB pin at its normal voltage. The output voltage will sag to compensate. It works really well as long as you keep the extra current-derived loop slower than the normal loop; 10x slower works well. I\'m using this technique in one of my current designs and you can drive into a short just fine.

The plan for now is to check if the TPS54428 wants to mate with the
INA199. According to the datasheet the controller, there should be no
hiccup. I will share the results in due course.

Best regards, Piotr