AP1695 Ver la hoja de datos (PDF) - Diodes Incorporated.
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AP1695 Datasheet PDF : 15 Pages
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A Product Line of
Diodes Incorporated
AP1695
Application Information Based on Buck Structure
The AP1695 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 as constant on time mode, in this way good dimmer
compatibility can be realized.
RF
L
BD1
L1
LED+
F1
N
TVS1
R9
C1
C2
R3
R2
Q2
+
D2
R10
C4
ZD1
T1
LED-
R4
D1
C3
R5
U1 6
VCC
5
FB
7
Drain
R6
R1
3
RI
1
S
4 GND
R7
CS 2
R8
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 got as below:
Io (, )
1
2
I
pk
(
,
)
1
2
0
Vcs _ ref
R8
sin( )
i（f
else
）
In consider 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 cut off 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 got as:
Io _ mean
k
1
Vcs_ref
R8
AP1695
Document number: DS37312 Rev. 1 - 2
8 of 15
www.diodes.com
June 2014
© Diodes Incorporated
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