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AP1694AS-13

OFFLINE, HIGH PF, HIGH EFFICIENCY DIMMABLE LED DRIVER CONTROLLER

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.

L1

L

RF

N

F1

BD1

C1

TVS1

R9

R2

C2

Z1

R3

D2

Q2

D1

R4

C3

VCC FB

R1

RI

OUT

SGND

GND CS

U1 AP1694AS-13

Q1

R7 R8

+

C4

OUT

T1

R5

R6

Figure 1. Typical Buck Application Circuit

  When the dimmer is connected, and the conduction angle of the dimmer is

; according to the control principle of the IC, the output current

can be determined as:

Io

(

,

)



1

2



I

pk

(

,

)



1



2

0



Vcs _ ref

R8

sin( )

i（f 

else

 ）

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

 Io _ mean



k1





0 Io (, )d

Where,

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

 is the cutoff angle of dimmer.

 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 ), the output current DC value can be calculated by:

Io _ mean



k

1



 Vcs_ref

R8

AP1694AS-13

Document number: DS37789 Rev. 1 - 2

8 of 14

www.diodes.com

July 2015

© Diodes Incorporated

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