AP3965 datasheet(6/13 Pages) DIODES

6 / 13 page

AP3965/66/71

Document number: DS36531 Rev. 3 - 2

6 of 13

www.diodes.com

November 2013

AP3965/66/71

A Product Line of

Diodes Incorporated

Operation Description

RFB1

RFB2

RCS

GND

AP3965/66/71

NAUX

IOUT

VAUX

vIN

CPC

CCPC

Figure 1 Simplified Flyback Converter Controlled by AP3965/66/71

Constant Primary Peak Current

The primary current Ip(t) is sensed by a current sense resistor RCS as shown in Figure 1.

The current rises up linearly at a rate of:

)

(

)

(

dip

…………(1)

See equation 2

Figure 2 Primary Current Waveform

As illustrated in Figure 2, when the current Ip(t) rises up to Ipk, the switch Q1 turns off. The constant peak current is given by:

Rcs

Vcs

Ipk

…………(2)

The energy stored in the magnetizing inductance LM each cycle is therefore:

M Ipk

⋅

…………(3)

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

Ipk

⋅

…………(4)

Where fSW is the switching frequency. When the peak current Ipk is constant, the output power depends on the switching frequency fSW.

AP3965 Datasheet(PDF) 6 Page - Diodes Incorporated

AP3965 Datasheet(HTML) 6 Page - Diodes Incorporated

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13

Datasheet Download

Link URL