Third version of the PWM dimmer and test results
In this article I will present the third version of the PWM dimmer I have described in previous articles. I have made major changes to the control circuit, the topology of the dimmer, and the construction of the device. I will also quantitatively compare the performance of the dimmer to previous versions and to a phase control dimmer. Schematic Topology The previous versions of the dimmer used only one transistor and one rectifier, switching the live connection through a filter network. This method worked, but was very inefficient and caused the MOSFET and the inductors to dissipate alot of power. This version uses two MOSFETS, one switching the output to live and the other switching it to neutral. The schematic is shown below: The circuit now consists of two MOSFETS in a half-bridge. The gate drive circuit and the MOSFET/rectifier circuit have not changed since the last revision. Filter The 600uH inductor and 100nF capacitor form a filter similar to one found in a buck converter.