Offline LED driver for retrofit lamps that can be dimmed to zero brightness without flickering

The MAX16841 LED dimmer with universal input (90VAC to 265VAC) operates on international dimmer models, saving design time and cost.
SUNNYVALE, CA—October 10, 2011—Maxim Integrated Products (NASDAQ: MXIM) introduces the MAX16841, an offline LED driver that provides flicker-free dimming from full brightness to zero using both leading-edge (triac) and trailing-edge (transistor) dimmers. Constant-frequency control optimizes efficiency at both high and low AC line voltages. With a wide input range of 90VAC to 265VAC, the MAX16841 is a universal solution for dimmer models in Japan, China, the US, and Europe, simplifying the replacement of incandescent and halogen bulbs and eliminating compatibility issues with existing dimmer installations. The MAX16841 operates without electrolytic capacitors, extending the life of LED lamps and saving space and cost. This LED driver is ideal for retrofit dimmable LED lamps and general-purpose LED bulbs in industrial, commercial and residential lighting applications.

Dimming issues in retrofit applications

A dimmer increases or decreases the amount of power supplied to a lamp, thereby increasing or decreasing the amount of light emitted. The two most common voltage regulation methods today are leading-edge (triac) and trailing-edge (transistor) dimmers. Both types of dimmers adjust the amount of power reaching the lamp by removing a portion of the AC waveform. As the names suggest, leading-edge dimmers remove the leading edge of the waveform just after it crosses zero, while trailing-edge dimmers remove a portion just before it crosses zero. Leading-edge dimmers are suitable for resistive or inductive loads, while trailing-edge dimmers are suitable for use with resistive or capacitive loads.

To seamlessly retrofit existing lamps, LED lamps must be compatible with both leading-edge and trailing-edge dimmers. These dimmers are typically designed for the purely resistive loads of existing halogen and incandescent lamps. However, LED drivers are highly nonlinear and are not fully compatible with the purely resistive loads of dimmers. Therefore, when installing LED lamps into existing electrical systems with built-in dimmers, the LED lamps typically flicker, are undimmable, and in some cases, fail to light at all.

The MAX16841 solves this dimming problem by controlling the lamp's input current using a unique, proprietary method. The driver actively shapes the input current, ensuring flicker-free operation with most electronic transformers and dimmers. Now, LED lamp designers can safely drop-in halogen and incandescent lamps and dim them to zero brightness, eliminating the need for costly facility upgrades.

*Outstanding flexibility optimizes efficiency under all operating conditions
The MAX16841 can be designed in isolated (flyback) and non-isolated (buck) configurations, making it ideal for both high AC line voltages (220VAC to 230VAC) and low AC line voltages (100VAC to 120VAC). The constant-frequency control scheme improves efficiency by using optimal conduction mode (DCM or CCM) depending on the input voltage. Additionally, the MAX16841's current control technology improves dimming efficiency because the switching regulator itself already ensures sufficient hold current, eliminating the need for a current bleeder for the dimmer's hold current.

*Expand your applications with universal inputs, reducing design time and costs

The MAX16841 can be configured for a universal input (90VAC to 265VAC), providing flicker-free dimming in global retrofit applications. The MAX16841 eliminates the need for a separate LED driver to meet international voltage requirements, reducing inventory and design costs.

*Extends lamp life and saves space

The MAX16841 can be designed without an electrolytic capacitor. Since electrolytic capacitors are typically the first components to fail in a driver circuit, this design approach extends the life of the LED lamp. If the existing design includes an electrolytic capacitor, the MAX16814 ensures that the lamp continues to operate even if the capacitor fails.

Additionally, the design without electrolytic capacitors reduces driver cost and size, making it suitable for small form factors.