Marvell LED controller leads new direction – SIL2012
February 2012 – At the Strategies in Light conference in Santa Clara, Marvell introduced their new LED dimmer and bulb control ICs. These devices bring not only a new capability but new price point for residential and commercial lamps. Following the keynote from Soul Semiconductor, a manufacturer of LEDs for lighting, the growth of the lighting market is several billion units, and a great deal of these will be multi-die LED units. The key drivers are overall cost of ownership, and reduced energy use. Taking into account the extended lifetimes of the LEDs vs incandescent bulbs and the reduction in manpower for the task of replacement of the lights the lighting market is recognizing the value of the new technology.
The challenge for the LED industry is to create a replacement bulb that will perform both in existing sockets and with equivalent function/use as existing bulb technology. The new Marvell 88EM8183 and 88EM8182 AC/DC LED Driver Ics address these issues. Based on Lutron dimmer compatibility, and over 110 types of existing dimmers, the driver Ics feature a single stage primate side current control, an on-chip HV start-up power supply circuit, a low standby current for off state power optimization. The chips EM8183 dimmer driver supports smart dimming down to 1 percent without flicker, as well as high efficiency up to 90% with a greater than 0.95PF power factor.
The design represent a new price point for lighting control under both AC high voltage control functions and low voltage DC drive. The following figure shows the comparison for an in-bulb driver application. Not only does the new IC reduce the overall cost, but it reduces the PCB complexity and devices on the BOM. These BOM changes include the elimination of the Opto-coupler and secondary feedback circuit, the dimmer bleeder circuit, and the external start-up power supply circuit. The reduced BOM also leads to a smaller design which allows for greated flexibility of the bulb design.
Marvell EM8183 LED Dimmer Solution Comparison
The Marvell drivers are unique in that they support multi-string and multi-LED drivers. HB LEDs are available in single units, duals and quad modules. The typical assumption is that the multi-units are all one color with the same color temperature. The variability in color temperature however is fairly large in LEDs. For that reason mixed color modules are used. These include White / Amber modules and RGBW (Red, Green, Blue, White) modules. These allow for color correction due to aging and operating temperature. The key advantage, is a single bulb can be inventoried and used from multiple applications ranging from soft light to cool light and high brightness. The multi-string drive allows for bulb characterization, so a table can be built to maintain a specific color temperature output, provided the dimmer operation is managed by a microcontroller and software. To help manage this mode of operation, the Marvell chips also have thermal management logic.
