PFC - how to calculate input voltage, switching frequency etc

[Stenberg]

Hi,

I want to calculate input voltage (ex. U(dc)=85V-260V), current, power, switching frequency for after the diode bridge and before the PFC-circuits (Boost PFC and Totem-pole Bridgeless PFC) in order to, later on, simulate the PFC-circuits.

Overview: "wall socket - ac/dc-converter [EMI filter - diode bridge - PFC] - dc/dc-converter - battery"

The information I have right now is input values for the ac/dc-converter: Pin= 920W, Iin=4A, f=50Hz, Vin(ac)=230V.

The end-goal is to calculate values for the components (D, L, Switch) for the PFC-circuits and calculate the losses in the circuits.


Any advice? Thanks!

//Stenberg

 

[Tony Stewart]

www.ti.com/lit/ug/tidubk8b/tidubk8b.pdf

Possible PFC stage topologies for SMPS:
• Boost converter
• Buck converter
• Flyback converter
• Cuk converter
• SEPIC converter

Possible PFC stage operation modes:
• Continuous Conduction Mode (CCM)
• Discontinuous Conduction Mode (DCM)
• Critical Conduction Mode; Boundary Conduction Mode;Transition Mode) (CRM; TM)

Interleaving PFC boost converters has great advantages, especially input/ output current ripple reduction
1) benefits for bulk capacitor
2) benefits for input filter (Differential Mode acting)
Modern superjunction MOSFETs are the ideal active switch for PFC
A 600V ultrafast Si diode can perform well in a (2Ø) CRM PFC boost converter

 

[tcmtech]

Why do you feel you need PFC on such a small load?

 

[AnalogKid]

Unitrode (now a part of TI) invented the boost PFC control chip under contract from a power supply company, then got permission to release it to the world. They have several generations of parts, each more complex and more efficient than the last. There are a ton of old app notes that drill down into every detail, plus the handouts from the Unitrode power supply design seminar series. I think TI preserved all of it somewhere.

Note that a 1 kW PFC is not exactly a beginner's project. Vicor tried one and failed; so did Astec. Lambda abandoned the full-brick format, put theirs in a double-wide brick, and had good success with it. Internally it was the Unitrode app note almost part-for-part, except for a very sexy inductor.

ak

 

[ronsimpson]

I have only used boost PFC. Not easy project.
Read this .PDF. I think it is only 500 watts but is a good example.
https://www.ti.com/lit/ug/tidudf3/tidudf3.pdf

 

[Stenberg]

Thanks for all the reply's!

tcmtech: I have picked apart an on-board charger for a plug-in hybrid and the goal was to design a smaller version of this. Since the on-board charger (higher output power arount 3,5kW) had (boost interleaved) PFC I assumed to continue with it but try and reduce the amount of components, hence use (boost PFC). I know I use lower power but I assumed that the PFC still was needed for reduction of AC current harmonics and to make sure to be within international regulations about reducing harmonic current. Should I not have PFC?

 

[tcmtech]

If it's part of an original systems design and works or can be made to work there no reason not to use it but otherwise it needs some degree of justification that fit your application.

Personally I don't really concern myself with power factor control on things unless it's a high powered device or a group of them that has to run near the limits of its supply circuit for long periods of time like say running a induction motor or eset of them or like devices that draws 16 - 18 amps at full load off of a 20 amp circuit where some PF clean up could free up 2 - 4+ amps of headroom on the lines feeding things.