AP3776B

Document number: DS36737 Rev. 6 - 2

9 of 17

www.diodes.com

December 2015

© Diodes Incorporated

AP3776B

Figure 2. The Operation Waveform of Flyback PSR System

AP3776B).The current rises up linearly at a rate of:

M

L

t

dt

t

dip

)

(

Vin

)

(



(1)

CS

CS

PK

R

V

I



(2)

2

2

1

PK

M

I

L

Eg







(3)

So the power transferring from the input to the output is given by:

SW

PK

M

f

I

L

P









2

2

1

(4)

The maximum frequency for AP3776B system is about 84kHz.

Constant Voltage Operation

As to constant-voltage (CV) operation mode, the AP3776B detects the auxiliary winding voltage at FB pin to regulate the output voltage. The

auxiliary winding voltage is coupled with secondary side winding voltage, so the auxiliary winding voltage at secondary rectification diode D1

conduction time is:





Vd

V

N

N

V

OUT

S

AUX

AUX







(5)

Where the Vd is the diode forward voltage drop.

t

ONP

t

ONS

t

OFFS

t

OFF