Variable power supply design

[engr_joni_ee]

Hi, I am looking for variable power supply design for SiPM that can set the output voltage between 25 V to 30 V and can deliver current of about 2 A. Is it possible to control the bias voltage with an FPGA ?

 

[barry]

1) what is the “bias voltage”? Do you mean the output voltage?
2) if you use a DAC then of course you can control the voltage with an FPGA. If you can accept coarser control, then you can use digital switches.

 

[engr_joni_ee]

Yes, the bias voltage is the bias voltage of the SiPM which is the output of the variable/programmable power supply. I am wondering which manufacture have such programmable power supply that can vary the output between 25 V to 30 V with current 2 A ?

 

[wwfeldman]

there are many manufacturers
you can start here

Equipment - Power Supplies (Test, Bench) | Electronic Components Distributor DigiKey

Equipment - Power Supplies (Test, Bench) are in stock at DigiKey. Order Now! Test and Measurement ship same day

www.digikey.com

i suggest choosing "active" and "in stock"
then find the input voltage range you have,
the output voltage range that includes your required range,
and since you want 2 A, pick one that is at least 4A capable.

other things to look for
adjustable current limit
survives short circuit
remote voltage sense (so the supply gets the voltage correct where it is used)

 

[engr_joni_ee]

I need to include programmable power supply in my design in PCB. This means that standard lab power supply is not an option. I am not able to find what I am looking for.

 

[barry]

There are many, many, many switching regulators that are capable of what you want. There are even eval boards. Just connect a simple DAC to your FPGA and connect the DAC output to the control input of the regulator.

You may not even need a DAC. You could just use some binary weighted resistors connected to your FPGA.

 

[KlausST]

Hi,

I'm not sure what you are looking for.

To get a variable voltage power supply there are several options:
* using a digital pot in the feedback
* using SMPS controller with digital interface
* manipulating feedback with PWM
* manipulating feedback with DAC
*....

Klaus

 

[engr_joni_ee]

I am basically looking for an "isolated" variable/programable power supply with 28 V input that can be programmed by FPGA through DAC to give output between 25 V to 30 V with current of about 2 A. I have searched but not able to find the isolated programable power supply with the mentioned specs.

 

[barry]

I am basically looking for an "isolated" variable/programable power supply with 28 V input that can be programmed by FPGA through DAC to give output between 25 V to 30 V with current of about 2 A. I have searched but not able to find the isolated programable power supply with the mentioned specs.

You said nothing about isolation or input voltage in your original post. Maybe now would be a good time to state ALL your requirements, rather than just letting people guess what you want.

 

[engr_joni_ee]

I am sorry for not providing enough information in the first post.

I just listed down the requirements for the isolated dc-dc converter PCB mount chip/module. I am looking for anything similar which is attach.

Vin: 28 V
Vout: 25 V to 30 V
Output Current: 2 A.
Package: PCB mount

 

[BradtheRad]

To step volts up and down, a buck-boost converter is the short path.

However since you only wish to add or drop a few volts...
It makes equal sense to build a boost converter, and install an additional diode drop. Then you get 25V output by shutting off the switch.
Output is unregulated. Set desired voltage by changing bias or duty cycle.
The inductor needs to be rated to carry 2A, and saturate at 3A. A similar component must be in a prepackaged converter if that's what you prefer.

As for the buck-boost type, it needs an inductor rated to saturate around 5A. Of course that's greater bulk and expense.

 

[KlausST]

Hi,

You showed the Traco converters.
* You could use one of them to get about 35V isolated
* then add a step-down (buck) with SPI_EEPOT in the feedback. Use optocouplers for SPI isolation.

Klaus

 

[engr_joni_ee]

There are many, many, many switching regulators that are capable of what you want. There are even eval boards. Just connect a simple DAC to your FPGA and connect the DAC output to the control input of the regulator.

You may not even need a DAC. You could just use some binary weighted resistors connected to your FPGA.

I am not able to find the regulators with analog control signal as an input to control the output voltage. Could you please some example of such regulators ? I gues you ment linear regulator here.

You also mentioned switching mode regulators whoes output voltage can be control by PWM signal, right ?

You

--- Updated Mar 17, 2022 ---

To step volts up and down, a buck-boost converter is the short path.

However since you only wish to add or drop a few volts...
It makes equal sense to build a boost converter, and install an additional diode drop. Then you get 25V output by shutting off the switch.
Output is unregulated. Set desired voltage by changing bias or duty cycle.
The inductor needs to be rated to carry 2A, and saturate at 3A. A similar component must be in a prepackaged converter if that's what you prefer.

As for the buck-boost type, it needs an inductor rated to saturate around 5A. Of course that's greater bulk and expense.

View attachment 174499

Hi, I think I am getting the idea. I am just wondering about the ripples/fluctuations at the output. Can they be removed by adding more capacitors in parallel to the load ?

 

[KlausST]

Hi,

You also mentioned switching mode regulators whoes output voltage can be control by PWM signal, right ?

Almost every regulator (linear, switching) with feedback pin can be controlled by PWM or DAC...
There is no need for a special controllable regulator.
--> https://www.edaboard.com/threads/design-of-pwm-controlled-smps-output-voltage.377215/post-1616040

Klaus

 

[BradtheRad]

I am just wondering about the ripples/fluctuations at the output. Can they be removed by adding more capacitors in parallel to the load ?

My post #11 shows the concept of a boost converter. You can change the 220uF to any value you wish. My example has ripple a few tenths of a volt (theoretical).

In case you decide to homebrew your power supply...
For a buck converter it's comparatively easy to make output voltage adjustable and regulated. It's not so easy with a boost converter.