AC/DC offline LED power supply controllers lowers BOM costs

Developed by Dialog's Power Conversion Business Group, formerly iWatt, 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 device 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 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.

Key features include High PF >0.92 and Low THD <20%; proprietary Input Current Shaping Option that enables the iW3609 to balance the power loss of the bleeder circuit; wide Dimmer Compatibility - Leading Edge, Trailing Edge and Non-Traditional R, R-C and R-L Types - Automatic Detection of Dimmer Type; 1% to 100% Wide Dimming Range; resonant Control to Achieve High Efficiency:  >82% typ. (without dimmer); and LED Over-Temperature Protection with Automatic Derating of LED.

The device 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 device are buck-boost and flyback.

The advanced dimmer detection technology 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 minimises 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.”