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PDF ( 数据手册 , 数据表 ) AL1677

零件编号 AL1677
描述 HIGH EFFICIENCY AND ACCURACY LED DRIVER CONVERTER
制造商 Diodes
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AL1677 数据手册, 描述, 功能
AL1677
UNIVERSAL, HIGH EFFICIENCY AND ACCURACY LED DRIVER CONVERTER
Description
The AL1677 is a universal AC-input (85~277 VAC), high-efficiency and
high-accuracy Buck LED-driver converter. The AL1677 topology
provides accurate constant current (CC) line and load regulation,
operating at boundary conduction mode (BCM) to ease in EMI/EMC
qualification and testing to meet the latest regulatory laws.
The AL1677 system removes the auxiliary winding and external high-
voltage MOSFET with few external components to create a low bill of
material (BOM) cost solution. The AL1677 has rich protection features
to enhance system safety and reliability. With thermal foldback
function, the AL1677 can reduce output current when the drivers
temperature is higher than the setting value.
Pin Assignments
(Top View)
GND 1
ROVP 2
NC 3
VCC 4
8 CS
7 CS
6D
5D
SO-8
The AL1677 is available in SO-8 package.
Features
> 90% Efficiency
Valley Detection to Minimize Switching Loss
Universal 85 to 277 VAC Input Range
Internal MOSFET up to 500V
Tight Current Sense Tolerance : ± 3%
Low Startup Current: 170µA
Low Operation Current: 100µA (Static)
Standard Inductor (no auxiliary winding)
Internal Protections
- Undervoltage Lockout (UVLO)
- Leading-Edge Blanking (LEB)
- Cycle-by-cycle Overcurrent Protection(OCP)
- Output Open/Short Protection(OVP/OSP)
- Open-Load and Reload Detection
- Thermal Foldback Function(TFP)
- Over-Temperature Protection(OTP)
SO-8 Package
Totally Lead-Free & Fully RoHS Compliant (Notes 1 & 2)
Halogen and Antimony Free. “Green” Device (Note 3)
Applications
Retrofit LED Lamps
High Voltage DC-DC LED Driver
General Purpose Constant Current Source
Notes:
1. No purposely added lead. Fully EU Directive 2002/95/EC (RoHS) & 2011/65/EU (RoHS 2) compliant.
2. See http://www.diodes.com/quality/lead_free.html for more information about Diodes Incorporated’s definitions of Halogen- and Antimony-free, "Green"
and Lead-free.
3. Halogen- and Antimony-free "Green” products are defined as those which contain <900ppm bromine, <900ppm chlorine (<1500ppm total Br + Cl) and
<1000ppm antimony compounds.
AL1677
Document number: DS37526 Rev. 1 - 2
1 of 13
www.diodes.com
November 2015
© Diodes Incorporated







AL1677 pdf, 数据表
AL1677
Application Information (continued)
Output Open Protection (OVP)
AL1677 has output open-voltage protection controlled when the LED is open, which can prevent the output voltage from increasing to a very high
value. This feature can help the system designer select a smaller volume capacitor. The output voltage is set by the external resistor R3, shown in
Figure 1.
When LED is open, the toff time can be calculated as:
toff
L1VCS _ REF
VOVP R5
Where
VOVP is the output open voltage,
The output voltage is set by R3, and R3 is:
R3 VROVP _ REF toff VROVP _ REF L1
12 CREF VCS _ REF 12 CREF VOVP R5
Where
VROVP_REF is the internal ROVP pin 0.5Vs reference,
CREF is the internal 6pF capacitor.
Thermal Foldback Protection (TFP)
AL1677 has a thermal foldback function and adopts a self-adaptive control method, which can prevent the system from breaking down due to high
temperatures. The overheating temperature is set at +140°C typical. When the junction temperature of the IC is higher than +140°C typical, the
device will linearly decrease the internal reference voltage to decrease the output current. As a result of this feature, the device can control the
systems output power at high ambient temperatures, to control the quantity of heat of the system. This enhances the safety of the system at high
temperatures.
The thermal foldback waveform is shown below:
Output current
100%
50%
TFOLD=140 OTP
Junction temperature/°C
Figure 2. Thermal foldback waveform
Over-Temperature Protection (OTP)
The AL1677 has OTP protection function. When the junction temperature reach to +170°C typical, the IC will trigger an over-temperature
protection condition which causes the device to shut down and latched. Once OTP has triggered, the system will resume after the systems AC
source supply has been reset and power up.
Design Parameters
Setting the Current Sense Resistor R5
The AL1677 uses peak current control method to obtain constant current control and senses the peak current of the inductance cycle by cycle.
The sample value is compared with the internal 0.4V reference. When the sampling value is up to 0.4V, the IC control of the internal MOSFET will
turn off.
The peak current of the inductance is:
AL1677
Document number: DS37526 Rev. 1 - 2
8 of 13
www.diodes.com
November 2015
© Diodes Incorporated














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