cupoftea
Advanced Member level 6
Hi,
We all agree that if you have a constant load, then the best power factor is gained by using a bona fide Boost PFC controller, such as eg LT1248 etc, and using the textbook low voltage feedback loop bandwidth etc etc.
But what if you have a highly transient load, on/off/on......full load to no load and vice versa , continuously........
....is the usual Boost PFC stage actually of much use in this circumstance?
Woudlnt a faster voltage loop COT (constant off time) Boost converter, which rose its current reference up from zero every 10ms, but then (if fully loaded) quickly went to peak current without waiting for the mans peak....woudlnt that actually give a better overall power factor in the case of highly transient load?
I mean, take a standard Boost PFC stage, (ie low voltage feedback loop bandwidth of some 10 Hz or so) and no load to full load (and vice versa) it irregularly, every few seconds or so.......your mains current is not going to be a constant amplitude sinusoidal wave as you know....wouldnt some other way be better for "overall" PFC, in this case?
What i'm saying is...if your load is highly transient in nature, and at a particular "burst rate", then typical Boost PFC is very definetely not going to give you the best power factor...other methods would....those other methods being the sort that dont give good power factor when the load is constant?
We all agree that if you have a constant load, then the best power factor is gained by using a bona fide Boost PFC controller, such as eg LT1248 etc, and using the textbook low voltage feedback loop bandwidth etc etc.
But what if you have a highly transient load, on/off/on......full load to no load and vice versa , continuously........
....is the usual Boost PFC stage actually of much use in this circumstance?
Woudlnt a faster voltage loop COT (constant off time) Boost converter, which rose its current reference up from zero every 10ms, but then (if fully loaded) quickly went to peak current without waiting for the mans peak....woudlnt that actually give a better overall power factor in the case of highly transient load?
I mean, take a standard Boost PFC stage, (ie low voltage feedback loop bandwidth of some 10 Hz or so) and no load to full load (and vice versa) it irregularly, every few seconds or so.......your mains current is not going to be a constant amplitude sinusoidal wave as you know....wouldnt some other way be better for "overall" PFC, in this case?
What i'm saying is...if your load is highly transient in nature, and at a particular "burst rate", then typical Boost PFC is very definetely not going to give you the best power factor...other methods would....those other methods being the sort that dont give good power factor when the load is constant?