Ismosys stocking dimmable single-stage digital LED driver for 15W SSL retrofit bulb applications

Dialog Semiconductor’s pan-European sales & marketing representative, Ismosys, has released details of its new high performance, 15W single-stage, AC/DC offline power supply controller for dimmable LED luminaires that require high Power Factor (PF), low total harmonic distortion, outstanding TRIAC dimmer capability and low BOM cost.

Developed by Dialog”s Power Conversion Business Group, formerly iWatt Inc, the new iW3609 uses advanced digital control technology to detect the dimmer type used, providing dynamic impedance to interface with the dimmer and at the same time control the LED brightness.

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

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 advanced dimmer detection technology used in the iW3609 enables the device to operate efficiently with most wall dimmers, including leading-edge dimmers (R-type or R-L type) and trailing-edge dimmers (R-C type). In addition, 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 voltage range.

According to Ismosys Nigel Watts, the iW3609 uses Dialog’s EZ-EMI technology to minimise the external component count by simplifying the EMI filter: “Intelligent dimmer detection technology minimises the bleeding power loss, Watts said. “Furthermore, the digital control loop of the iW3609 maintains stable overall operating conditions without the need for loop compensation components. A current shaping option is available to balance the power loss of the bleeder circuit.”


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