Induction Hob Power Measurement Using Duty Cycle Switching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing induction heating coil systems in induction hobs lack precise power measurement accuracy, especially when multiple coils are used together, leading to inaccuracies in cooking programs and power delivery.
Innovation Solution
The method involves controlling the induction heating coil using a converter with a half-bridge or full-bridge circuit, varying frequency and duty cycle, and measuring current and voltage to accurately determine power, with switching between different duty cycles at zero crossings or within half-waves to compensate for measurement errors, allowing for precise power measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single duty cycle is used for controlling the induction heating coil, then the control is simple, but measurement errors in power calculation occur due to voltage measurement inaccuracies
Solution Approach 1:
The patent applies periodic action by alternating between a first duty cycle and a second duty cycle (where the second duty cycle is the complement of the first, i.e., 1-DC) in periodic intervals. This periodic switching allows the system to perform multiple voltage measurements under different duty cycle conditions, then calculate an averaged power value that compensates for measurement errors. The periodic nature ensures that both duty cycle states are sampled regularly, improving measurement precision without requiring permanently complex hardware.
2Measurement precision
If voltage and current are measured continuously to calculate power, then power measurement accuracy is high, but the measurement process becomes complex and error-prone
Solution Approach 1:
The patent applies preliminary action by pre-establishing the relationship between duty cycle and voltage measurement conditions. Before performing power calculations, the system deliberately switches between known duty cycle states (DC and 1-DC) to obtain voltage measurements that are then used in a predetermined calculation formula. This preliminary structuring of measurements under controlled conditions simplifies the overall measurement process while maintaining accuracy, as the calculation methodology is established in advance based on the duty cycle switching pattern.
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
This approach enables precise and accurate power measurement of the induction heating coil, reducing measurement errors and ensuring accurate control of cooking programs, even under varying load conditions.
Implementation Method 1
an induction heating coil (15a, 15b) of a device for wirelessly transmitting power to a consumer, in particular a converter (18) for an induction hob
Implementation Method 2
The converter is operated in a half-bridge or full-bridge circuit. Furthermore, the converter is operated at a frequency and a duty cycle, whereby both the frequency and duty cycle can be varied to adjust the power delivered by the induction heating coil
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
In a method for measuring the power at an induction heating coil controlled by an inverter, the inverter is operated in a half-bridge or full-bridge configuration. The inverter operates at a specific frequency and duty cycle. The current through the induction heating coil is measured. In at least one operating mode for controlling the induction heating coil, the system switches between a first duty cycle and a second duty cycle, the second duty cycle being determined by subtracting the first duty cycle from the first. The voltage across the half-bridge or full-bridge is then measured.