35W Dimmable Single-String LED Driver Reference Design

The STEVAL-ILL070V4 reference design from STMicroelectronics is intended to drive one LED string with a maximum output current of 700mA. The LED current can be finely adjusted using either a 0- to 10-V interface or a pwm signal (for example, provided by a microcontroller) on the SELV portion of the board.

The universal input capability makes this reference design suitable in worldwide designs.

On the secondary side, the board includes a connector to plug an auxiliary linear on the switching voltage regulator side to supply small circuits (e.g., IoT wireless expansions like BLE, Spirit or WiFi modules). The schematic for a simple linear regulator to supply 5 V or 3.3 V is also provided.

A very high power factor and efficiency are obtained even at light loads. Input voltage variations, excessive input voltage (overvoltage like surges or bursts) and very low input voltages are managed by the HVLED001A protections, improving the reliability of the application.

STEVAL-ILL070V4 reference design board (click on image to enlarge)

The output capacitor is automatically discharged at turn-off to prevent any harm from contact with output connector.

Output open circuit and overload protections include auto restart for safe operation in lighting environments.

Key features include:

• Input voltage: VIN of 90- to 305-Vrms, 45- to 66-Hz
• Output current: 700 mA (VLED = 24 V to 48 V)
• Dimming: 100% to 10%
• Dimming interfaces: 0 - 10 V and pwm input
• High power factor, low THD
• Efficiency: > 90% @ full load
• Open load voltage limiting (52.4 V)
• Optional remote turn-off input
• Optional 3.3 V - 0.1 A voltage regulator
• Fast VOUT discharge
• RoHS compliant

STEVAL-ILL070V4 reference design (click on schematic to enlarge)