Reference design for Low cost Triac Based LED driver

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  • The cost of power LEDs is rapidly decreasing, while performance is improving.
  • The design is based on a Triac based dimmable 15 W LED driver.

 

LED driver
LED driver

Dimming LEDs can extend the life cycle further, and also reduce power drain. By far the
most common dimming method is the Triac phase-control dimmer, which directly replaces
the AC On-Off switch.

The reference design is based on the development of a low-cost driver for LEDs that is compatible with Triac phase-control dimmers. The design gives luminaire manufacturers a low-cost, commonly available dimming option for home fixtures. A side benefit is that, when not wired to a dimmer, the unit’s power factor is over 0.9.

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The design is based on the ST Microelectronics ST L6562A transition-mode PFC controller driving a single stage PFC-flyback power converter.

Some of the design features for the design are :

  • The circuit is designed for working in operating input voltage of 90V -130V.
  • The circuit is designed to drive a dimmable Triac based device with a maximum power consumption of 15 Watt.
  • The design uses a single-stage PFC flyback converter, which saves space, costs, and components. The PFC-flyback converter does away with the large input capacitor (usually an electrolytic) and replaces it with a small film capacitor. It hence contributes to reducing the size of the LeD driver which is an important factor for the LED-based drivers.
  • The input current waveform should be matched with the input voltage, and the input current level should be adjusted to give the required output.
  • The power factor of the device should be optimised according to the application of the LED driver which is defined by the use of LED in industrial or residential applications. Generally, residential appliances have a power factor of 0.7 and industrial appliances range from 0.9. The design offers a Power Factor of 0.97 in undimmed mode.
  • The design is capable of driving a maximum of 14 LED’s connected in an array.
  • The output of the driver is isolated for more mounting options and also provides a ripple factor of less than 20 per cent.
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These are some of the features been provided by the reference design which can help in the design of a 15-watt dimmable Triac based driver useful for LED’s as well as FAN and speed control-based applications.

The design contains implementation and full design files.  All the documents can be downloaded here.

 


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