AP1694AS-13

Document number: DS37789 Rev. 1 - 2

8 of 14

www.diodes.com

July 2015

© Diodes Incorporated

AP1694AS-13

Application Information Based on Buck Structure

The AP1694AS-13 uses constant on time control method within one AC cycle to achieve the high power factor. When the dimmer is connected to

the driver, although a part of input voltage is cut off by the dimmer, the system still operates in constant on time mode. In this way, good dimmer

compatibility can be realized.

T1

OUT

+

VCC

FB

OUT

CS

GND

C3

R7

R5

R6

R4

D1

C4

R3

Q1

BD1

C1

L1

R8

D2

R1

RI

SGND

R2

R9

RF

L

N

C2

Z1

Q2

F1

TVS1

U1 AP1694AS-13

Figure 1. Typical Buck Application Circuit

When the dimmer is connected, and the conduction angle of the dimmer is



can be determined as:

_

1

sin( )

1

( , )

( , )

28

2

0

cs ref

o

pk

V

if

II

R

else



 

 

 











 

 



（

）

In consideration of the dead zone of the buck structure, the output current DC value can be calculated as below:

_

0

1

( , )

o mean

o

I

k

I

d



  







Where,

_

cs ref

V

is the reference of the current sense, and the typical value is 1V.



is the phase of the input voltage.

k is the current modification coefficient , and the value is approximate to be 0.7.

When no dimmer is connected with the driver (

0

s_ref

_

1

8

c

o mean

V

Ik

R



  