AP1695-20C 查看數據表（PDF） - Diodes Incorporated.
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AP1695-20C Datasheet PDF : 15 Pages
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AP1695-20C
Application Information Based on Buck Structure
The AP1695-20C 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
F1
N
BD1
TVS1
L1
R9
C1
C2
R2
ZD1
R3
Q2
R4
D1
LED+
D2
+
R10
C4
T1
LED-
C3
R5
U1 6
5
FB
VCC
7
Drain
R6
R1 3 RI
1
S
4 GND
R7
2
CS
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:
1
Io _ mean
k
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.
0 When no dimmer is connected with the driver (
), the output current DC value can be got as:
Io _ mean
k
1
Vcs_ref
R8
AP1695-20C
Document number: DS37538 Rev. 1 - 2
8 of 15
www.diodes.com
March 2015
© Diodes Incorporated
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