Induction Heating Inverter Phase Control for Snubber Loss Reduction

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Solution Overview

Problem

Induction heating devices face challenges in effectively controlling output and preventing discharge loss of snubber capacitors, leading to heat generation and potential damage from hard switching.

Innovation Solution

The induction heating device incorporates a working coil, an inverter with switching elements, snubber capacitors, a phase detector, and a controller that adjusts the operating frequency based on phase information and user input to optimize output and prevent snubber capacitor discharge loss.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If the induction heating device uses traditional output control methods based on resonance current and voltage magnitude, then the output can be measured, but discharge loss occurs in the snubber capacitor and hard switching damage is generated

Engineering Contradiction:

Improvedischarge loss of snubber capacitorVSAvoidhard switching damage

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The patent implements a feedback control mechanism where the controller continuously monitors the phase difference between resonance current and switching voltage, and adjusts the operating frequency accordingly. This closed-loop feedback system enables precise output control while preventing snubber capacitor discharge loss and hard switching damage by maintaining optimal phase relationship.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent changes the control parameter from magnitude-based (current/voltage amplitude) to phase-based (phase difference) control. By measuring and controlling the phase difference between resonance current and switching voltage, the system achieves accurate output control without causing snubber capacitor discharge loss or hard switching damage.

Inventive Principle:

Principle #35Parameter changes

2Power

If the induction heating device increases output power, then heating performance is improved, but heat generation and damage risk increase

Engineering Contradiction:

Improveoutput power of working coilVSAvoidheat generation and damage

Core Design Contradiction:

PowerVSObject-affected harmful factors

Solution Approach 1:

The feedback control mechanism monitors phase difference and adjusts operating frequency to maintain optimal operating conditions. This enables the system to increase output power when needed while automatically preventing excessive heat generation and damage risks through continuous phase-based regulation.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent implements dynamic control by continuously adjusting the operating frequency based on real-time phase difference measurements. This dynamic adaptation allows the system to optimize power output while preventing harmful effects, rather than using fixed operating parameters.

Inventive Principle:

Principle #15Dynamics

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 solution enhances output control, reduces heat generation, and minimizes damage by ensuring safe operation, thereby improving product performance and reliability.

Implementation Method 1

In the induction heating method, eddy current may be generated in the object (e.g., the cooking vessel) made of metal based on a magnetic field generated, around the coil, when a high-frequency power of a predetermined magnitude is applied to the coil to heat the object.

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

a phase detector electrically that is connected between the inverter and the working coil and configured to detect a phase difference between the resonance current applied to the working coil and a switching voltage applied to the second switching element

Methodology Applied

Scientific EffectPhase detection:

Implementation Method 3

a controller that is configured to receive, from the phase detector, phase information including the phase difference, provide the inverter with a switching signal to thereby control the switching operation, and adjust an operating frequency of the switching signal based on the phase information to thereby control an output of the working coil

Methodology Applied

Scientific EffectFrequency modulation:

Implementation Method 4

a snubber capacitor including a first snubber capacitor electrically connected to the first switching element, and a second snubber capacitor electrically connected to the second switching element

Methodology Applied

Scientific EffectCapacitance energy storage: Capacitance

Data Source

PatentUS11528783B2Induction heating device having improved output control function

Publication Date: 2022.12.13 LG ELECTRONICS INC

AI summary

An induction heating device includes a working coil, an inverter including a first switching element and a second switching element that are configured to perform a switching operation and to apply a resonance current to the working coil, a snubber capacitor including a first snubber capacitor connected to the first switching element, and a second snubber capacitor connected to the second switching element, a phase detector configured to detect a phase difference between the resonance current applied to the working coil and a switching voltage applied to the second switching element, and a controller configured to receive, from the phase detector, phase information including the phase difference, provide the inverter with a switching signal to thereby control the switching operation, and adjust an operating frequency of the switching signal based on the phase information to thereby control an output of the working coil.