Efficient Retrofit LED Drivers For Existing Infrastructures

A significant advantage for LED retrofit lamps is that these lamps do not require a new electrical infrastructure. Due to their long life and reliability, they have been pervasive in many commercial and residential lighting applications. However, making retrofit LED lamps fit in the form factor of previous light source and function correctly in existing infrastructures (including triac or trailing-edge dimmers, electronic transformers, sockets) without flicker is a real challenge to the designer. So, the LED Driver solutions for wide input voltage range such as 120V AC/230V AC and 12V AC input lamps used in automotive, tracklighting and tasklighting applications (e.g, cabinet lamps and desk lamps) should be compatible with triac and trailing-edge dimmers and electronic transformers. They must also provide additional features like good PFC and limited external components. Here are some LED driver reference designs for LED retrofit lamps that more or less meet these design challenges. Take a look!
  • 1W to 5W Retrofit LED Driver for MR16: This reference design implements a 1W to 5W LED driver configured in size and features for MR16 LED replacement though it can drive HBLED (high-brightness LED) in a variety of lighting applications. In general illumination applications such as track lighting (for example, desk lamps and under-cabinet lights), the power source is a 12 Vac or +12 Vdc source that can be very loosely regulated. So the LEDs need to be driven by a constant current source. This design features an auto-detect circuit in combination with the NCP3065 which allows input from a 12 Vdc or 12 Vac supply and still maintains targeted output current regulation. The ON Semiconductor NCP3065 is the heart of the circuit operating at ~150 kHz in a non–isolated configuration. The reference design can handle 350mA average LED current. Click here to get detailed reference design.
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  • Buck-boost LED Driver for AR111 Lamp: Here is a reference design for an AR111 lamp LED driver which drives ten LEDs in 5S2P configuration, i.e., two parallel strings of five LEDs. The core IC in the design is MAX16819 used in buck-boost mode. The MAX16819 is a step-down HB LED driver that provides a cost-effective solution for LED bulbs such as MR16 and other LED illumination applications, and a wide dimming range of 5000:1. The input voltage to the circuit is 12VAC and the average output current is 500mA per string. Four Schottky diodes provide full-wave rectification, and eight capacitors filter the voltage. Tantalum capacitors are used to offer superior performance under elevated temperatures. To know more, click here.
  • 230V AC/ 120 V AC Retrofit LED driver with High Efficiency and Power Factor: This AC/DC LED driver reference design is intended for application in E27-type (and similar type) retrofit light sources and is based on an UBA3070. There are two versions of the reference design. One is intended to operate at 230V (AC) 50Hz mains voltage and the other is intended to operate at 120V (AC) 60Hz. Both the options provide an output power of approximately 6W to 10 W into a string of typically eight white LEDs although it can be used for loads outside this range. The LED driver is based upon the principle of a boundary conduction buck mode power converter and an AC/DC Graetz bridge rectifier input stage combined with a Spangler circuit. The design achieves high efficiency and Power Factor (PF) compliant with current regulations. The circuit is optimised for an output voltage ranging from 20V to 30V. To know more, click here.
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  • High Power Boost LED Driver for AR111 and MR16: This is a 20W LED driver reference design ideal for MR16 and AR111 applications which need good compatibility to DC voltages, AC voltages and electronic transformers and convert power from these sources to a regulated average LED current. The design implements a boost topology LED driver based on TPS92560. The TPS92560 is a simple LED driver designed to drive high power LEDs by drawing constant current from the power source. The power source for the design can be 12VDC, 12VAC / 50Hz 60Hz or 12VAC E-transformer. The design can drive an LED Load of 30V – 40V at a regulated average LED Current of 500mA. The system shows an efficiency of 86 per cent at 12V DC and a high power factor of greater than 0.9 at 12V AC. Click here to get detailed reference design.


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