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AL9910EV5

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Issue 3 – June 2011 www.diodes.com
© Diodes Incorporated, 2011
AL9910EV5 BUCK LED DRIVER USER GUIDE
Fig. 1 AL9910EV5 evaluation board connection diagram
AL9910EV5
Issue 3 – June 2011 www.diodes.com
© Diodes Incorporated 2011
2
DESCRIPTION
The AL9910EV5 is an offline non-isolated LED driver Evaluation board designed to work on both 115V and
230V AC line voltages. It provides a constant LED current output which drives a single string of between 14
and 18 LEDs, with a LED current of 240mA.
The evalution board is designed with a footprint to fit iinside a T8 LED fluorescent replacement lamp tube. It
will provide a total LED power ranging from 10W to 13W.
AL9910EV5 SETUP AND TESTING PROCEDURE
Prerequiste
1. AL9910EV5 evaluation board.
2. A set of 240mA LEDs strings with 14 to 18 series-connected LEDs. The LEDs should be mounted on a
heatsink capable of a power dissipation of 10 to 13W.
3. For safety reasons during testing, please use an isolated 115V or 230V AC source from the output of an
isolation tranformer. For public demonstration, the evaluation board and LEDs should be fitted into a
transparent case with sufficient insulation to meet the local safety requirements.
Connections and Power up
1. Preset the isolated AC source to either 115VAC or 230VAC.
2. ENSURE THAT THE AC SOURCE IS SWITCHED OFF OR DISCONNECTED.
3. Connect the anode wire of the LED string to the LED+ terminal which is located at the right hand side of
evaluation board.
4. Connect the cathode wire of the LED string to the LED - terminal which is located at the right hand side of
the evaluation board.
5. Connect a voltmeter & ammeter according to the connection diagram in Figure 1 if LED current and
voltage measurements are required.
6. Connect the two AC line wires to the AC1 and AC2 terminals which are located at the left hand side of
evaluation board.
7. Ensure that the area around the board is clear and safe, and preferably that the board and LEDs are
enclosed in a transparent safety cover.
8. Turn on the mains switch. LED string should light up with LED current of 240mA +/-15%. DO NOT TOUCH
THE BOARD, LEDs OR BARE WIRING.
Caution: The AL9910EV5 is a non-isolated design. All
terminals carry high voltage during operation!
AL9910EV5
Issue 3 – June 2011 www.diodes.com
© Diodes Incorporated 2011
3
OPERATION
The AL9910A device is a PWM high-efficiency LED driver control IC. It allows efficient operation of High
Brightness (HB) LEDs from voltage sources ranging from 85VAC up to 265VAC. The AL9910A can be
configured to work in either fixed frequency or constant OFF-time mode. In fixed frequency mode, the
AL9910A controls an external MOSFET at a fixed switching frequency up to 300kHz, which can be
programmed using a single resistor. The LED string is driven at a constant current rather than at a constant
voltage, thus providing constant light output and enhanced reliability. The output current can be programmed
between a few milliamps and more than 1.0A.
Input filter and Rectifier section
In order to meet the EMI requirement, Cx1, Cx2, CX3, CX4, L1 and L2 are used to provide sufficient filtering
for both differential-mode and common-mode noise generated from the switching converter circuit after the
bridge rectifier.
The rectified line voltage from the bridge rectifier DB1 is fed into a valley-filled passive power factor correction
stage to provide a high power factor for the AC line input. The passive PFC stage comprises of C11, C2, D1,
D2, D3 and R1. This design gives power factors of greater than 0.9 at low line voltage.
Constant Current Buck Converter section
The buck converter section consists of LED controller AL9910A (U1), Ultra-fast free-wheeling rectifier SF30JG
(D4), Inductor (L3 and L4) and a high voltage MOSFET switch (Q1). On this evaluation board, the AL9910A is
configured to operate in the constant OFF-time mode to provide the best LED current regulation. The constant
OFF-time of the AL9910A’s gate output is set to approximately 14µs using resistor R9. Please refer to the
product datasheet for more details on how to configure the constant OFF-time mode.
The circuit values have been designed to provide an output current of 240mA. The LED current level is set by
resistors R5-R7. For detailed applications information please refer to the AL9910/A datasheet.
There is also provision for an optional gate transistor pair (Q2) to drive a MOSFET with a higher gate charge if
a higher LED current is required. Q2 is a high current gate driver in a SOT23-6 package.
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AL9910EV5

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EVAL BOARD T8 LED DVR 240MA
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