bridgeless pfc controller - Page 1
Forum section: electronics / projects

author: ali_asadzadeh
author_rank: Super Contributor
timestamp: June 21, 2017, 08:44:34 am
content: Hi,Do you recommend any bridgeless pfc controller IC or app-note to implement it with a MCU?I know about the UCC28070DWR, but it's rather expensive

author: MagicSmoker
author_rank: Super Contributor
timestamp: June 21, 2017, 06:18:29 pm
content: You can use a standard UC3854 or similar type of PFC controller for the "totem-pole" and "symmetrical boost" bridgeless PFC topologies. Note that in most (all?) bridgeless topologies you either need to use opto-feedback or a differential/instrumentation amplifier with a common mode input range that comfortably exceeds the mains voltage to allow the controller IC to monitor the output voltage. EMI filtering can be especially challenging in bridgeless PFC designs as well.

author: ali_asadzadeh
author_rank: Super Contributor
timestamp: June 22, 2017, 07:03:12 am
content: Thanks for the info, Do you recommend any web-links or app-notes?

author: MagicSmoker
author_rank: Super Contributor
timestamp: June 22, 2017, 06:58:23 pm
content: Quote from: ali_asadzadeh on June 22, 2017, 07:03:12 amI will attach one app note on the totem-pole boost PFC topology that I personally think is very valuable; you should be able to use that information to jump start searching elsewhere for more. Also, the symmetrical boost is briefly covered by its inventor, Sanjaya Maniktala, in his most excellent book "Switching Power Supply Design & Optimization".

author: ali_asadzadeh
author_rank: Super Contributor
timestamp: June 23, 2017, 09:15:08 am
content: Thanks MagicSmoker, I appreciated it a lot

author: MagicSmoker
author_rank: Super Contributor
timestamp: June 23, 2017, 10:24:34 am
content: You're welcome, and as a bonus prize for thanking me (hah) I'll toss out some of my opinion based on experience:Years ago the only real choice of PFC controller IC was the venerable Unitrode (now TI) UCx854 (where x = 1, 2, 3 and signifies temperature range). It's still a workhorse and the basic design has been copied by many others, if not the pinout - you can spot the functional copies by the use of a "multiplier out" pin and the placement of the current sense resistor in the negative return line along with a rather high maximum current sense voltage in the range of 2.5V. The high Isense voltage gives better noise immunity for sure, but it also requires a relatively high wattage resistor to deal with a given output power.These days, if I need PFC below about 300-400W and the application is cost-sensitive I like International Rectifier's (now Infineon) One-Cycle ICs. This control scheme doesn't need to sense the input voltage and has a current sense input scaled to 1V (also in the return line, like the UCx854). The current version is IR1155, but you'll find papers referring to bridgeless PFC using the original part in this series, the IR1150.I've also used On Semi's NCP1631, which is a two channel interleaved controller IC that operates in Boundary Conduction Mode operation (or, as they call it, Critical Conduction Mode). On-Semi has an app-note on bridgeless PFC as well that is pretty good, including a clever way to get the necessary current sense signal using current transformers rather than a shunt resistor in the return line. Lessee... AND8481 looks like the right document.Finally, I really despise the UCC28070 as a result of the problems I had trying to get it to work in a high power front end I was designing a few years ago. The details are kind of fuzzy, but I do recall that 3 respins of the board did not improve its twitchy/unstable behavior, and that I ended up using a relatively massive amount of output capacitance to stop it from repeatedly tripping overvoltage protection. In the end I had to abandon it completely because I couldn't be sure it wouldn't trip OVP in the field if either the downstream converter or the genset supplying it power suddenly unloaded. A quick check of the e2e forums shows that people are still having similar problems with it so I would definitely avoid it.Hope that helps. Don't kill yourself playing with the mains, etc.

author: ali_asadzadeh
author_rank: Super Contributor
timestamp: June 23, 2017, 12:52:31 pm
content: Really thanks MagicSmoker, I will try not to blow myself up

author: Oleander
author_rank: Contributor
timestamp: July 06, 2017, 06:34:03 pm
content: @ MagicSmokerWhat would you use for a 1500W off-line, 1 phase PFC controller ?With traditional input bridge.I am about to design it and I'd like to use the interleaved scheme, if possible.