UC1845A: Need Application circuit for Buck Application

manoj kumar kakireni muni

Part Number: UC1845A
Other Parts Discussed in Thread: UCC28C42, LM5104

Hi Team,

we are working on a buck application using the IC UC1845A, for 120V to 15V conversion. pls provide us the reference implementation.

Please share us the TINA spice model for this IC.

The datasheet has only flyback and boost implementation circuits. If TI has any circuit that is implemented using IC UC1845A as a BUCK converter, pls do share with us.

thankyou

Manoj

over 3 years ago

0 Steven Mappus1 over 3 years ago

TI__Mastermind 29305 points

Hi Manoj,

Thanks for connecting through E2E. Unfortunately TI does not have a TINA model for UC1845A as mentioned in this E2E thread. For the power stage only, you could download TI Power Stage Designer and simulate the buck using your design parameters. Using a general purpose PWM to control a buck power stage is fairly straight forward. I would say the most challenging part is the need for a high-side, level shifted gate drive which is detailed in this E2E thread along with some good references. Good luck with your design.

Regards,

Steve M

0 manoj kumar kakireni muni over 3 years ago in reply to Steven Mappus1

Prodigy 140 points

Hi Steven,

Thanks for your reply. I referred the threads and is referring to Level shifters. But the Level shifters stage includes bootstrap cap connection to PWM driver. But these ICs (UC1845A or UCC28C42) does not have BST pins. Also these ICs have Totem Pole outputs, we are not sure how to implement BUCK configuration.

So we request you to provide some reference CKT, so that we can simulate and config for our requirement (120V to 15V).

A paper drawn circuit is also fine at earliest. Your support is much appreciated.

thanks in advance

Regards

Manoj.

0 Steven Mappus1 over 3 years ago in reply to manoj kumar kakireni muni

TI__Mastermind 29305 points

Manoj,

It is not so popular to make a buck converter from UCx84y PWM controllers and this is why I cannot readily provide a reference design or example. Here is one E2E thread asking about a buck converter using UC2843. You are correct that the UC1845A does not have a BST pin and they are totem pole, GND referenced outputs. We need to level shift from GND by either using a gate drive transformer or isolated gate driver or half-bridge driver. Using a half-bridge driver such as LM5104 between the OUT of the PWM and the high-side MOSFET will provide the missing BST function you mentioned.

Steve M

Power management

Power management forum

UC1845A: Need Application circuit for Buck Application