SSL1523 datasheet(5/21 Pages) NXP

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UM10406

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User manual

Rev. 01 — 3 August 2010

5 of 21

NXP Semiconductors

UM10406

SSL1523 5 W LED driver

Demo board connections

The demo board can be operated from mains voltages of 120 V (AC) (60 Hz) up to

230 V (AC) (50 Hz). The board is designed to work with multiple high power LEDs with a

total working voltage of 12 V to 25 V. The output current can be set by resistor R18, see

Section 7. A dedicated LED load connected to K3 can be supplied on request. The

connector K2 can be used to attach other LED loads. The output voltage is limited to a

maximum of 33 V. When attaching a LED load to an operational board (hot plugging), an

inrush peak current will occur due to discharge of capacitor C10. After (some)

discharge(s), the LEDs may deteriorate and/or become damaged.

4.1 Connecting the demo board:

• If a galvanic isolated transformer is used, this should be placed between the AC

source and the demo board.

• Connect a user-defined LED (string) to the connector K2 as shown in Figure 3. Make

sure that the anode of the LED (string) is connected to + (bottom side of this

connector).

Functional description

The SSL1523 IC (Ref. 3) has several internal functions which include the following:

• The SSL1523 controls and drives the flyback converter.

• Over Current Protection (OCP) of the internal FET at 0.5 V on the SOURCE pin.

• The converter frequency is set with an internal oscillator, the timing of which is

controlled by external RC components on pin RC.

• The REG pin controls the on-time of the internal switch between 0 % and 75 %.

This board is optimized to operate at a power factor of 0.9 in the nominal application with

six LEDs on the output. In order to achieve this, the converter operates dominantly at a

constant ton mode. The output power of the converter is buffered by capacitor C10, and

therefore the circuit exhibits resistive input current behavior (see Figure 4).

Fig 3.

Demo board connection diagram

pin 1: LED +

pin 6: LED

−

pin 5: LED

−

pin 4: LED

−

pin 3: LED +

pin 2: LED +

pin 1: LED +

pin 2: LED

−

019aaa134

pin 2:

−

pin 1:

pin 3: N

pin 1: L

pin 2:

control input from

external opto coupler

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