STEVAL-ILL016V2 STMicroelectronics

STEVAL-ILL016V2 15 Watt regulated Triac-dimmable LED driver for the North American (115 V) market Data brief Features Line voltage range: 96-132 V 60 Hz Drives strings of 4 to 12 jumper-selectable white LEDs connected in series Current: 1 A max (preset for 350 mA, as shipped) Undimmed power factor: > 0.9 LED current ripple: < 20% P-P Isolated output for safe LED heatsinking RoHS compliant Description STEVAL-ILL016V2 The STEVAL-ILL016V2 15 watt regulated Triac- dimmable LED driver is an upgraded version of the STEVAL-ILL016V1. Its purpose is to make development for different LED combinations easier to implement, and to incorporate improvements based on lessons learned from the first version. Improvements from the previous version include easy configuration of the LED voltage and current, flexible input filter layout, and sufficient space for easy modification of the basic circuitry. June 2010 Doc ID 17474 Rev 1 1/5 For further information contact your local STMicroelectronics sales office. www.st.com 5 Using the STEVAL-ILL016V2 STEVAL-ILL016V2 1 Using the STEVAL-ILL016V2 The STEVAL-ILL016V2 is shipped without the jumpers that select transformer taps for specific numbers of LEDs in each parallel string. Please refer to the schematic diagram in Figure 1, and place the jumpers in the appropriate positions. The board operates with any number of LEDs with the capacitors supplied at C14 and C15. LED ripple current is higher for smaller numbers of LEDs. The LED voltage limit for open-load protection can be set with R30, instead of R32. Refer to Figure 1 for voltage divider details. 1.1 Operation This unit is based on a PFC-flyback power converter. Design equations are provided in application note AN1059 (available on www.st.com). It is strongly recommended that this application note be studied prior to modifying the design. There are two current limits, one from the isolated secondary (optically coupled) and one on the primary side. The primary side limit responds to the line voltage, and should dominate with the line lower than 102-108 V. The current limit is set by the parallel combination of R25 and R26. Values of parts at R10 and divider R5, R6, R11 also affect the primary current. Refer to the L6562A datasheet, and application notes for the L6561 and L6562 for guidance on modifying the input side characteristics. The secondary side limit responds to the average LED current. It should take over when the line voltage is above 102-108 V. LED current is set with the resistors at R31 (shipped with 0.47 wire-wound, topside) and R35-R38 (unmounted 0805 SMT, bottomside). The schematic contains a formula for selecting resistor values and guidance for resistor selection. In dimmed operation, the primary side current limit dominates the secondary side limit is saturated, calling for full output. Current to the LEDs is limited by the dimmer Triacs conduction angle. 1.2 Additional capabilities The demonstration board output can be extended to 30 watts, on the same PCB layout, with some component changes. Several flexible transformers and higher current input filters have been designed, and application guidance is available. 1.3 First sample run errata If present, please remove the incorrect, unneeded components at locations D5 and D6. The RCD clamp consisting of D8, C4, and R18-20 perform their function. The schematic incorrectly shows a 133 kW resistor at R32. The sample has the correct value of 330 k . 2/5 Doc ID 17474 Rev 1