Simulation Techniques During the Process of LED Driver Development
Every LED driver is composed by one, two or sometimes three different topologies based on power electronic components: magnetics, MOSFETs and DIODEs working under hard conditions. The electronics reliability is limited by the stress that these components are able to support. More and more, LED drivers are demanded with a wide range of output power, so the operation of this kind of topologies integrated in the LED driver has many variations far away from its optimal design operation. This is especially critical in topologies like LLC resonant topology (going out of ZVS operation or third resonance problems) or Power Factor Corrector Booster topology (increasing switching power losses due to very light load operation).
Guaranteed reliability without an over-cost in materials involves a fitted development by means of optimal magnetics design and knowing the behaviour of that topology in all range of the LED driver operation. Using topologies simulations, magnetics involved in the LED driver can be designed in an optimal way, fitting them into the application. Using this way of design, all functional parameters, such as frequency operation or Duty Cycle can be estimated and fixed in final application. It is especially interesting if we may foresee Conducted Electro-Magnetic Interferences by setting switching frequencies.
Also, this method provides all information about electrical parameters like voltage or currents through components, allowing the engineer to estimate power losses and how are they distributed on the circuit, in all components. In addition, power losses can be distributed in a regular way between transformer and semiconductors or between wire and core in a transformer in order to find the maximum efficiency allow in the application, achieving the best trade-off.
Most of simulation models have been developed in State-Space apart from LLC topology. This is because of the First Harmonic Approximation (FHA design method), since it doesn`t fit enough with the model of an LLC resonant topology in a constant current LED driver application, including a wide output voltage range. Also, LED load for the constant current LED driver in LLC simulation must be calculated in every point of LLC resonance, following its gain behaviour.
In conclusion, simulating topologies during the design process a LED driver can provide the necessary analytic tools to estimate functional parameters, electrical parameters, power losses and efficiency by fitting the magnetics. Thus, product reliability might be maintained without producing a component over design, and so it’s corresponding over cost.