T
treez
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Regarding offline SMPS's for driving LED lightbulbs of 7W+, virtually every single semiconductor company offering (as linked below) is using power factor correction, even though PFC is officially not required below 25W.
Why is this?
Is it because non power factor corrected circuits have large-ish electrolytic caps after the mains rectifier bridge which may get damaged by overvoltage spikes when/if the bulb is accidentally connected to a triac dimmer? (ie, overvoltage spikes due to input filter resonance).
Or is it because they are genuinely concerned about losses in the electricity supply system?
Or is it because mains voltage spikes might damage a primary side electrolytic capacitor, more than say a film capacitor?
Or is it because PFC operation means an overall lower voltage across the switching fet, which means less switching losses?
Or is it because operation with dimmers requires the primary dc bus voltage to fall quickly as the phase cut dimmer turns off?
Or is it because they don't want electrolytics at the primary dc bus, because they eventually get worn out by inrush current every time the led bulb is turned on?
http://www.ti.com/lit/ds/symlink/tps92010.pdf
http://www.ti.com/lit/ds/symlink/lm3447.pdf
http://cds.linear.com/docs/en/datasheet/3799fa.pdf
**broken link removed**
Why is this?
Is it because non power factor corrected circuits have large-ish electrolytic caps after the mains rectifier bridge which may get damaged by overvoltage spikes when/if the bulb is accidentally connected to a triac dimmer? (ie, overvoltage spikes due to input filter resonance).
Or is it because they are genuinely concerned about losses in the electricity supply system?
Or is it because mains voltage spikes might damage a primary side electrolytic capacitor, more than say a film capacitor?
Or is it because PFC operation means an overall lower voltage across the switching fet, which means less switching losses?
Or is it because operation with dimmers requires the primary dc bus voltage to fall quickly as the phase cut dimmer turns off?
Or is it because they don't want electrolytics at the primary dc bus, because they eventually get worn out by inrush current every time the led bulb is turned on?
http://www.ti.com/lit/ds/symlink/tps92010.pdf
http://www.ti.com/lit/ds/symlink/lm3447.pdf
http://cds.linear.com/docs/en/datasheet/3799fa.pdf
**broken link removed**
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