UC1901-SP: CC/CV Without Opto-coupler

Karthik Venkateshaiah

Part Number: UC1901-SP
Other Parts Discussed in Thread: UC1843-SP,

Hi,

I am designing a DC-DC fly-back converter using UC1843-SP PWM controller for space application. The use of Opto-coupler is prohibited in my application hence feedback control is done with UC1901-SP (magnetic feedback). My converter has to work in CC/CV mode (constant 500mA load current ). With magnetic feedback my converter is working good in CV mode of operation. Now my question is

a) Can i achieve CC/CV output without Opto-coupler ?

b) If yes Can i use UC1901-SP with external CC circuit for achieving CC/CV output ?

c) If not UC1901-SP can you please suggest any IC for achieving CC/CV output without Opto-coupler

Thanks & Regards,

Karthik Venkateshaiah.

over 3 years ago

0 Daniel Hartung over 3 years ago

TI__Mastermind 26145 points

Hey Karthik,

You are able to do feedback without optocoupler with UC1901-SP.

There is an example here:

https://www.ti.com/tool/TIDA-070002

Thanks,

Daniel

0 Karthik Venkateshaiah over 3 years ago in reply to Daniel Hartung

Prodigy 130 points

Hey Daniel,

Thanks for the application note. I already referred this document which is just a CV (constant voltage) output but for my application i need both CC/CV (constant current/ constant voltage). I need a clarification whether i can use UC1901-SP for achieving CC/CV output or can use only for CV output (In feedback controlling).

Thanks,

Karthik Venkateshaiah

0 Daniel Hartung over 3 years ago in reply to Karthik Venkateshaiah

TI__Mastermind 26145 points

Hey Karthik,

The UC1901-SP is used to bring the error signal over the isolation barrier.

While I don't have a specific application note for CC feedback and it, it should be possible to achieve CC/CV with it.

Below is an app note that shows how to do CC without the isolated feedback loop.

https://www.ti.com/lit/an/snva829/snva829.pdf?ts=1628604306229&ref_url=https%253A%252F%252Fwww.google.com%252F

Adding the circuit to the input of the UC1901-SP instead of into the controller is the one major change needed.

Thanks,

Daniel

0 Karthik Venkateshaiah over 3 years ago in reply to Daniel Hartung

Prodigy 130 points

Hey Daniel,

Thanks for the application note. In my application Isolated feedback is must. I have to get clarification on two things,

1) Should i use two separate loop for voltage control and current control ? means two UC1901-SP IC ?

2) what is the maximum voltage that UC1901-SP can withstand at PIN 11 (INV) ?

Thanks & Regards,

Karthik Venkateshaiah,

0 Daniel Hartung over 3 years ago in reply to Karthik Venkateshaiah

TI__Mastermind 26145 points

Hey Karthik,

The circuit to create the feedback for CV/CC would be implemented on the secondary side and then that voltage would be brought over using the UC1901-SP.

There would likely only need to be 1 UC1901-SP

Thanks,

Daniel

0 Karthik Venkateshaiah over 3 years ago in reply to Daniel Hartung

Prodigy 130 points

Hey Daniel,

Got it. and what is the maximum voltage that UC1901-SP can withstand at PIN 11 (INV) ? it is not clear in the datasheet.

Thanks,

Karthik Venkateshaiah.

+1 Daniel Hartung over 3 years ago in reply to Karthik Venkateshaiah

TI__Mastermind 26145 points

Hey Karthik,

INV is an error amplifier input thus the maximum voltage is 35 V.

Thanks,

Daniel

+1 Karthik Venkateshaiah over 3 years ago in reply to Daniel Hartung

Prodigy 130 points

Hey Daniel,

Thanks for the inputs.I am happy to say my converter is working in CC/CV mode with UC1901-SP.

Thanks & Regards,

Karthik Venkateshaiah.

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UC1901-SP: CC/CV Without Opto-coupler