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LED Lighting Solution using ON Semi’s NCP1216


With continuous pursue for more effective use of Earth's energy sources, demand for solutions to better utilization of energy is increasing. This is even so after the recent oil crisis.

Together with World direction to eradicate Thomas Edison's invention, the incandescent light latest by 2017, it develops an urgent need for alternate lighting solution. As such much research and development are done on providing a more efficient light source at night, and one such possible replacement is the high brightness LED source.

With improvement in its technology, high-brightness LEDs are becoming popular in the lighting industry for the following reasons:
  1. High luminosity;
  2. Low power consumption;
  3. Easy to mount;
  4. low space occupancy;
It is therefore an ideal candidate for incandescent replacement.

Principle of Operation

An important part of the LED lighting design is the Fly-back Converter topology, which provides the necessary isolation and flexible power handling.

Figure 1 shows a block structure of a Fly-back Converter. It resembles the AC/DC convertor with a twist of a constant current output. The structure comprises the followings:
  1. PWM controller
    • The central control for power conversion (AC-DC), voltage and current control;

  2. Bridge rectifier
    • Perform essential function of power rectification, the initial phase of AC-DC conversion;

  3. Fly-back transformer
    • Isolates primary and secondary side of the circuit;

  4. Opto-coupler
    • This complete the circuit with performing the feedback function to the PWM controller;

As a result, it is possible for the system to work in either of conditions: constant voltage versus constant current.

WPG reference solution to LED Lighting control

An LED Lighting solution is developed by WPG Electronics (SA) Pte Ltd to allow customers a faster time to market. It is base on On Semi PWM Controller, NCP1216A. The solution makes it possible to drive up to 4 high brightness LEDs of maximum 1W each (a total of 4 Watts).

Specifications of WPG solution is as follows:
  1. Universal AC Input : 85V to 260V AC
  2. Output Power : 3.3 W
  3. Output Current : 250 mA
  4. Isolation : Galvanic Isolation
  5. Maximum component height : 12mm
  6. Overall PCB size : 50mm x 40mm

NCP1216A is selected for its features as follows:
  1. Duty cycle operation
    • The NCP1216 series can operates with a wide Duty cycle operation up to 75% for NCP1216 and limited duty cycle of 45% for NCP1216A;

  2. Dynamic self supply
    • It has capability to generate a DC voltage (VCC) of up to 40V from the high voltage DC rail;

  3. Current mode control
    • The specialty of this is its adjustable skip cycle which allows skip operation at low peak current;

  4. EMI signature improvement
    • The chipset uses Internal Frequency Dithering to up-set and thus lowering the effect;

  5. Switching frequencies selection
    • NCP1216 comes with a few ranges of Fixed switching frequency version at 65kHz, 100kHz, 133kHz;

  6. Ramp Compensation
    • Sub harmonic oscillations can be compensated;

  7. Over Current Protection
    • Through device low power burst mode operation;

  8. Low Standby Power
    • By skipping switching cycles, in light load condition;

  9. External MOSFET
    • flexibility in the selection of the MOSFET wrt the application;

  10. Internal Temperature Shutdown

The Fly-back Transformer poses one of the strongest challenges to our design. There are two critical Factors governing the design:
  1. Primary Inductance
    The primary inductance should be sufficient to store the required "per cycle" energy at manageable current. From the secondary power, the required energy per cycle is derived and then the primary inductance is computed.

  2. Design space allocation
    Space is another constraint in design of LED lighting solution. This is especially so when we are designing replacement to incandescent light source of E27 model (standard light bulb). Stress is added onto the transformer in terms of size.Both requirements of the transformer contradict each others, since the transformer capacity in energy storage is proportional to its size. To allow larger capacity while shrinking its physical size thus requires improvement in technology. The design of the transformer therefore would require expertise in such field, with knowledge of technical and material at the same time. WPG worked with Singapore KAMI Electronics Industry Pte Ltd for the purpose.


By completing our lighting solution, WPG has demonstrated our capability in design and development of LED lighting solution. The continuation of our development process is already in the pipeline to work on different variation of production ready LED lighting solutions, namely on E27, MR16, LED street lighting, table lamp.

The benefits to our customers would be a working model which will shorten the time needed to market. Our technical experts in this field will also be an added advantage to our customers during design and modification process. The experience we have gained from our design process is valuable and thus give our customers an edge over competition.

The LED lighting solution from WPG is an ideal adaptation for customers who are interested in an immediate solution to gain competitive edge in a new frontier of the market. The provision of such solution is another effort by WPG to ensure value added to our customers' need. WPG view our customers as partner in growth, we will continue to do so in time to come.

Written by Ammoni A. Robert
Edited by C. H. Siew