Induction Heating Load Impedance Estimation via Capacitor Voltage
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Solution Overview
Problem
Conventional induction heating devices require high-performance controllers to accurately calculate load impedance, leading to increased costs due to the need for high sampling frequencies of high-frequency resonance voltages.
Innovation Solution
An induction heating device with a first voltage sensor to measure the voltage applied to a resonant capacitor, a second voltage sensor to measure the supply voltage, and a controller that calculates resistance and inductance values based on these voltage values, allowing for accurate impedance calculation without a high-performance controller.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high-performance controller is used to sample resonance voltage at high sampling frequency, then impedance calculation accuracy is improved, but device cost increases
Solution Approach 1:
The patent changes the measurement parameters by measuring voltage across the resonant capacitor instead of directly sampling the high-frequency resonance voltage. This parameter substitution allows impedance calculation using lower-frequency voltage variations that can be accurately captured by standard controllers, resolving the contradiction between measurement precision and device complexity
Solution Approach 2:
The patent introduces the resonant capacitor voltage as an intermediary measurement point. By measuring the voltage across the capacitor rather than the coil voltage directly, the system obtains information about the resonance state through a lower-frequency signal that standard controllers can handle, thus avoiding the need for high-performance controllers while maintaining measurement accuracy
2Measurement precision
If resonance voltage is sampled at high sampling frequency, then impedance calculation accuracy is improved, but sampling hardware requirements increase
Solution Approach 1:
The patent changes what parameter is being measured - instead of sampling the high-frequency resonance voltage directly, it measures the voltage across the resonant capacitor. This voltage contains information about the resonance state but varies at a lower frequency that can be easily sampled by standard ADCs, thus improving measurability while maintaining calculation accuracy
Solution Approach 2:
The patent substitutes direct high-frequency voltage sampling with a different measurement approach - measuring capacitor voltage and using computational methods to derive impedance. This replaces the need for high-speed sampling hardware with standard measurement components combined with signal processing algorithms
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
Enables precise impedance calculation and output power control, reducing costs and improving temperature estimation accuracy.
Implementation Method 1
an induction heating method is a method in which an eddy current is generated in a container made of a metal component using a magnetic field generated around a coil when high-frequency power of a predetermined magnitude is applied to the coil so that the object to be heated itself is heated
Implementation Method 2
an eddy current is generated in a container made of a metal component using a magnetic field generated around a coil
Implementation Method 3
a resonant capacitor configured to form a resonant circuit together with the working coil
Data Source
AI summary
An induction heating device according to an embodiment comprises: a working coil which is disposed at a position corresponding to a heating area where an object to be heated is placed, and forms a load together with the object to be heated; a resonant capacitor which forms a resonant circuit together with the working coil; an inverter circuit which includes a plurality of switching elements and supplies a current to the working coil; a first voltage sensor which measures a voltage value applied to the resonant capacitor; a second voltage sensor which measures a supply voltage value supplied to the resonant circuit through the inverter circuit; and a controller which, when the working coil is in operation, calculates at least one of the resistance value of the load and the inductance of the load on the basis of the voltage value of the resonant capacitor and the supply voltage value.