UC3842: Average Current Mode PWM Controller

C.S.

Part Number: UC3842

Tool/software:

We are designing a controller where we need to implement average current mode operation for a product that was designed for the (now obsolete) UC3848.

Are there any other controllers that support this mode of operation? Or is there an application note explaining how this can be implemented with a 'regular' buck or boost converter?

I understand average current mode is also widely used on CCM PFC controllers. I have toyed with the idea of using one, and taking the line input voltage (used for the fast current shaping loop) as our control signal, although this would be a more 'unusual' approach.

Any recommendations welcome. Thanks

4 months ago

0 Hong Huang 4 months ago

TI__Guru 58015 points

Hi,

You need to add an average current circuit in your feedback. This note provides the idea

https://www.ti.com/lit/an/slua079/slua079.pdf?ts=1722442215149&ref_url=https%253A%252F%252Fwww.google.com%252F

Also this one:

https://www.ti.com/video/5400631988001?keyMatch=average%20current%20mode%20control&tisearch=search-everything

There are some reasons why not having them like peak current mode but what ever i cannot find any. You can add average current circuit externally.

PFC uses it due to helping lowering THD and better PF.

0 C.S. 3 months ago in reply to Hong Huang

Prodigy 60 points

I made a controller board based on OnSemi NCP1653, which worked surprisingly well. It proves the point that It can be easily implemented with minimun board space and a small number of passives.

Unfortunatelly the NCP1653 operates at a fixed 66KHz switching frequency and I need at least two switching frequencies to cather for converters using mosfet and IGBT (Possibly a third if we want to test SiC).

I looked at the UCC20180 which seems to fit the bill, but as many other newer controllers, it doesn't directly sense the input voltage. Is there any other way to set the input current?

The datasheet notes: "External compensation of the inner current loop is applied by means of the ICOMP pin." and also "Soft Start is programmed by the capacitance on this pin" which gives me an idea it could potentionally be done?

0 Hong Huang 3 months ago in reply to C.S.

TI__Guru 58015 points

Hi,

I cannot find UCC20180 from ti.com.

Besides, UCC20180 is a different device so you need to create a new thread to get support.

Power management

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UC3842: Average Current Mode PWM Controller