Tired of tricky LED driver problems? See a design that makes dimming efficiency and protection easy all in one ready to use solution.
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The DER-660 reference design from Power Integration addresses key challenges engineers face when designing efficient, reliable, and dimmable LED drivers. It delivers a 36 V, 800 mA output from a 180–265 VAC input, combining a high-line flyback converter with a switched valley-fill PFC circuit to maintain high power factor, reduce input ripple, and minimize energy loss. This solves common problems in traditional flyback designs, such as poor efficiency, unstable output, low power factor, and high total harmonic distortion (THD). Engineers no longer need to design complex PFC stages or manually optimize energy transfer from AC input to the LED load.
The design integrates a 650 V MOSFET, sense elements, safety-rated feedback, and both primary and secondary controllers in a single IC, simplifying the challenge of primary-to-secondary communication in isolated flyback topologies. The IC manages precise constant-current and constant-voltage output without requiring complex external handshaking circuits. During startup, an internal high-voltage current source charges a capacitor, while the primary listens for secondary requests for approximately 82 ms before taking control. After startup, the primary IC is powered via an auxiliary winding, allowing continuous regulation without external bias circuitry. This integration reduces design complexity and shortens development time for engineers.
The design also addresses EMI and surge challenges. Input fuses protect against component failures, while varistors clamp transient line voltage spikes. A two-stage LC EMI filter suppresses differential and common-mode noise caused by PFC and flyback switching. Bulk capacitors filter input ripple, stabilize the flyback DC voltage, and store energy generated by the PFC during MOSFET off-time. RCD snubbers dissipate energy stored in the transformer’s leakage inductance, while series diodes and a Zener-resistor clamp prevent excessive voltage during resonance or PFC energy transfer. These protections help engineers meet regulatory EMI standards without extensive additional circuitry.
Thermal management is built into the design to solve overheating issues common in high-power LED drivers. Thermal shutdown circuitry disables the MOSFET if die temperature exceeds the set threshold, re-enabling it once it cools. Thermal foldback on the secondary reduces output power if the secondary die temperature rises too high. Voltage monitoring pins detect overvoltage by converting bulk capacitor voltage into current through resistors, providing early protection against excessive voltage stress. These integrated protections prevent PCB damage and component failures under continuous fault conditions.
Digital DALI dimming is fully supported, solving the challenge of smooth, flicker-free LED brightness control. The design uses a two-way protocol, allowing communication between LED drivers and controllers. A microcontroller interfaces with the bus through isolated optocouplers, preventing ground loops. PWM signals control LED brightness: output current is sensed, amplified, and injected into the feedback pin through a non-inverting amplifier with adjustable gain. At startup, PWM is held at maximum to keep dimming inactive; current injection begins once PWM drops below a reference, enabling full 0–100 % dimming range. A 5 V regulator powers the microcontroller with decoupling and noise-immunity components, and programming is done via a dedicated header.
Power Integration has tested this reference design. It comes with a bill of materials (BOM), schematics, assembly drawing, printed circuit board (PCB) layout, and more. The company’s website has additional data about the reference design. To read more about this reference design, click here.
