7.5 Conclusions

The boost-buck is an ideal topology where the LED load voltage can be higher or lower than the supply voltage. It should also be used when the supply voltage is no more than 20% difference (worst case) from the LED load voltage. So if the LED voltage (maximum) is 20V and the supply voltage (minimum) is 23V, the difference is 3V, and 3/20 = 0.15 or 15%, so a Cuk or SEPIC should be used. If the supply voltage is more than 20% higher, use a buck topology. If the supply voltage is more than 20% lower, use a boost topology. The boost-buck is less efficient compared to buck or boost topologies.