QR Inverter Switching Control for Low-Loss Induction Cooking
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Induction cooking appliances with quasi-resonant inverters suffer from switching losses in the IGBT-switch, which reduce the lifespan of the inverter and affect efficiency.
Innovation Solution
A control method and system that regulates the switch-on and switch-off periods of the power switching device in the QR inverter circuit based on the minimum and maximum voltages across the switching device, synchronizing the switch-on instant with the minimum voltage to minimize losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the IGBT-switch is used in the QR inverter circuit, then the inverter can operate with a simple topology and cost-effective architecture, but switching losses occur which reduce the lifespan and efficiency of the switching device
Solution Approach 1:
The control unit determines the minimum voltage value during the switch-off period before the next switching cycle begins. By using this predetermined minimum voltage information to regulate the switch-off period, the system performs preliminary preparation to ensure optimal switching conditions are achieved, thereby reducing switching losses while maintaining the simple QR inverter topology
Solution Approach 2:
The control unit continuously monitors the voltage across the IGBT-switch during the switch-off period, determines the minimum voltage value, and uses this feedback information to dynamically regulate the switch-off period. This closed-loop control ensures that switching losses are minimized by adjusting the timing based on actual voltage conditions, improving efficiency without complicating the inverter architecture
2Loss of energy
If the switch-on and switch-off periods are extended to reduce switching losses, then the efficiency improves, but the switching frequency decreases which may affect the cooking performance
Solution Approach 1:
The control unit dynamically adjusts the switch-off period based on the determined minimum voltage value during each switching cycle. Rather than using fixed timing, the system adapts the switch-off duration to the actual voltage conditions, allowing optimal balance between reducing switching losses and maintaining adequate switching frequency for effective induction cooking
Solution Approach 2:
The control unit changes the timing parameters (switch-off period) based on the measured minimum voltage value. By adjusting these parameters dynamically according to operating conditions, the system optimizes the trade-off between minimizing switching losses and maintaining sufficient switching frequency for effective cooking performance
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Reduces switching losses, extends the lifespan of the switching device, and improves the efficiency of the inverter circuit while maintaining a cost-effective electronic architecture.
Implementation Method 1
induction heating coils, which are associated with the cooking zones and generate time-varying magnetic fields inducing eddy current in the loads
Implementation Method 2
generate time-varying magnetic fields inducing eddy current in the loads
Implementation Method 3
The internal resistances of loads cause the induced eddy currents to generate heat in loads itself
Data Source
AI summary
Method to control a quasi-resonant inverter (13) in an induction cooking appliance (1) provided with an induction heating coil (4). A switching device (21) is electrically connected to the induction heating coil (4) by a node (20) having a first voltage (VC(t)) which is indicative of the voltage across the power switching device (21). The method includes: providing to the switching device (21) an enabling signal (K1) comprising a plurality of pulses, in order to switch-on and switch-off the switching device (21) for a switch-on period (tON) and a switch-off period (tOFF), determining a second voltage (VCmin) indicative of the minimum value of the first voltage (VC(t)) during the switch-off period (tOFF), regulating the switch-off period (tOFF) based on the second voltage (VCmin), and regulating the enabling signal (K1) based on the regulated switch-off period (tOFF).