DESIGN, CONTROL AND IMPLEMENTATION OF INVERTERS TOPOLOGIES APPLIED TO DOMESTIC INDUCTION HEATING Student: Peter Doyle Supervisor: Prof. Gerard Hurley Ignacio Lope Final Year Project Presentation

Topics to be discussed: Function of Domestic Induction Heating Appliance Circuit Design and Analysis Digital Control Achieving Optimal Power Output Circuit Simulation Experimental Results Tasks to be completed

Function of Domestic Induction Heating Appliances V I f = 50Hz V dc V ac I ac DC Bus f = 20 kHz – 100 kHz

Circuit Design and Analysis Circuit Objectives: Maintain Zero voltage switching Generate a AC voltage Be able to produce a variable frequency 30kHz - 70kHz to control Power Output

Function of the Half-Bridge

Digital Control The Half-Bridge is controlled by an FPGA The variable switching frequency is generated by the FPGA from 70kHz - 30kHz depending on the required power output. This signal is sent to the Signal Driver to improve the strength of the signal at its source before it is transmitted to the transistors on the PCB. The Signal Driver has the logic inverse.

Digital Control After the FPGA was programmed it was discovered that when the FPGA is turned on the output of the pins went high for 1.8sec. The Solution was to add a relay circuit to isolate the PCB from mains voltage until intentionally switched on.

Achieving Optimal Power Output As shown in the graph below the resonant frequency, fr, (freq. at max power output) varies depending on the value of the resonant capacitor, Cr. The Switching frequency, fsw, must be greater than the resonant frequency to ensure Zero voltage switching.

Circuit Simulation

Experimental Results

Load 70khz Load 35kHz

Tasks to be Completed: Design a compete simulation of the Half-Bridge circuit including, filters, mains voltage rectification, switching topography and power output. Design of the printed circuit board (PCB) including choke, signal drivers, half bridge and common mode filter. Justify the selection of all component values. Test the half bridge in small signal DC conditions. Order PCB. Test under mains voltage conditions and demonstrate using existing control circuitry.

QUESTIONS?