HVLED007 datasheet(12/33 Pages) STMICROELECTRONICS

Il numero della parte	HVLED007

Spiegazioni elettronici	Transition mode PFC controller for flyback converters

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Application information

HVLED007

12/33

DS12866 Rev 1

Equation 4

Solving (Equation 4) for VCt (θ):

Equation 5

Figure 6. Key waveforms of the ICS circuit in figure 5

VCt (θ) is connected to the (-) input of the PWM comparator through the low-pass filter Rf Cf,

whose purpose is to remove unwanted high frequency noise. The associated time constant

(≈ 100 ns) is such that the voltage across Cf is not significantly different from that across Ct,

so that VCt (θ) is actually the reference Vcsref (θ) for the current loop. If we substitute the

expression (Equation 3) of IMULT into (Equation 5) we find:

Equation 6

that has exactly the desired form (Equation 2) with:

Equation 7

I MULT 

 T 

=

V Ct 



--------------------TON 



VCt 

 = I

MULT



 R





T ON 



-------------------

Vcsref

IMULT

Vcsref

Vcs t

Vcsref 

 = V

Ct 

 = [K

p Vinpk sin 

 V

c] kI Rt





T ON 



-------------------

Vcsx = Kp Vinpk

 V

 k

I Rt

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