1694AM-G1 查看數據表（PDF） - Diodes Incorporated.
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1694AM-G1 Datasheet PDF : 15 Pages
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A Product Line of
Diodes Incorporated
Application Information Based on Buck Structure (Cont.)
Fault Protection
Over Voltage Protection and Output Open Protection
AP1694A
VCC
RFB1
RFB2
FB
AP1694A
Figure 4. OVP Circuit
The output voltage is sensed by the auxiliary winding voltage of the Buck transformer, the VCC pin and FB pin provide over voltage protection
function. When the output is open or large transient happens, the output voltage will exceed the rated value. When the voltage of Vcc cap exceeds
VCC_OVP or VFB_CV, the over voltage is triggered and the IC will discharge VCC. When the VCC is below the UVLO threshold voltage, IC will start a
new work cycle and the Vcc cap is charged again by start resistance. If the over voltage condition still exists, the system will work in hiccup mode.
Attention: If the external fast startup circuit is adding in the application and the over voltage protection and output open protection happen, the IC
will trigger latch.
Output Short Protection
When the output is shorted, the output voltage will be clamped at 0. At this condition, VCC will drop down without auxiliary winding for power supply.
And the VCC will drop to UVLO threshold voltage, the IC will shut down and restart a new operating cycle, and the VCC is charged by startup
resistance. When VCC is higher than Vcc_start voltage, IC will output a bunch of pulse to control power switch on and off. When still no FB signal
detected the device will not output more pulse. So the VCC will drop to VCC UVLO threshold again. If output short condition still exists, the system
will operate in hiccup mode.
Attention: If the external fast startup circuit is adding in the application, the device will not work at UVLO mode, and the device will work at
minimum toff mode.
Over Temperature Protection
AP1694A has two kinds of over temperature protection processes. First, the system is operating normally, the ambient temperature is changed to
+170°C suddenly, the IC will trigger over temperature protection which leads to a latch work mode. Second, if the system starts when the ambient
temperature is higher than +150°C, over temperature protection will be triggered. So the AP1694A can startup successfully when the ambient
temperature is less than +150°C.
Components Selection Guide
If the system’s spec is changed, please refer to the design sheet of the AP1694A and select the compatible system parameter. When the system
needs to be adjusted slightly, please refer to the table below and adjust the value of the related component.
Item
IO
Output Current Ripple
ton_initial
Output Open Voltage
Dimming Performance
EMI
Line Compensation
Description
Output current
Small current ripple is good for LED life
System initial on time, used to startup the system
Setting the output voltage when the LED is open
Improve the dimming performance
Pass EN 55022 class B with 6DB margin
To get a good line regulation
Related Components
R8
C4
R1
R5, R6
R1, RF, R9, C2, C4
L1, C1
R7
AP1694A
Document number: DS37094 Rev. 1 - 2
11 of 15
www.diodes.com
May 2014
© Diodes Incorporated
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