Dimmable single-stage 15W LED bulb driver in distribution

February 20, 2014 // By Graham Prophet
From distributor Ismosys, Dialog’s iW3609 digital LED driver is designed as the driver for 15W solid-state-lighting (SSL) retrofit bulb applications: it operates with most wall dimmers including leading-edge dimmers (R-type or R-L type) and trailing-edge dimmers (R-C type).

The device is a 15W single-stage, AC/DC offline power supply controller for dimmable LED luminaires that require high power factor (PF), low total harmonic distortion, good TRIAC dimmer capability and low BOM cost. Developed by Dialog's Power Conversion Business Group, formerly iWatt Inc, the iW3609 detects the dimmer type used, providing dynamic impedance to interface with the dimmer and at the same time control the LED brightness.

The iW3609 reduces the BOM cost by using low-cost bipolar junction transistors (BJTs), eliminating high-voltage electrolytic capacitors and by including built-in over-temperature protection (OTP) derating with no NTC resistor. It uses iWatt’s PrimAccurate primary-side sensing technology to achieve LED current regulation under different AC line and LED load voltages, without using a secondary-side feedback circuit, thereby eliminating an opto-coupler. A proprietary input current shaping option enables the iW3609 to balance the power loss of the bleeder circuit.

iW3609 key features include;

High PF of over 0.92 and Low THD of less than 20%

Proprietary input current shaping option - enables the iW3609 to balance the power loss of the bleeder circuit

PrimAccurate - Isolated Off-Line AC/DC Controller

Wide dimmer compatibility - leading edge, trailing edge and non-traditional R, R-C and R-L Types

1% to 100% Wide Dimming Range

Meets IEC61000-3-2 current harmonic requirements and NEMA SSL6 dimming curve standard

Resonant control to achieve high efficiency: of over 82% typ. (without dimmer)

LED over-temperature protection with automatic derating of LED

The iW3609 operates the main power converter that delivers current to the LED load in quasi-resonant mode to deliver high power efficiency with minimal electro-magnetic interference (EMI). The commonly utilised converter topologies for the iW3609 are buck-boost and flyback. The iW3609’s cycle-by-cycle waveform analysis technology allows for fast dimmer setting response. When no dimmer is present, the device optimises the power factor, minimises the current harmonic distortion to the AC line, and regulates the output at nominal output current value over a wide input