Induction Heating Power Control via Crest Factor
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Solution Overview
Problem
Conventional induction heating devices for image forming apparatuses face challenges in accurately controlling power due to voltage distortion, which can lead to switching element breakdown and inaccurate power control, especially when the input voltage has a high peak value or distorted waveform.
Innovation Solution
The induction heating device incorporates a peak voltage detector, effective voltage detector, crest factor calculator, and power controller to calculate the duty ratio of the switching element based on the power needed, effective voltage, and actual crest factor of the input voltage, allowing for precise control of power delivery even with distorted waveforms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the switching element turns the induction heating coil ON and OFF based on peak voltage to control power, then power control is achieved, but the switching element can be broken down due to high peak voltage
Solution Approach 1:
The patent changes the control parameter from peak voltage-based duty ratio to effective voltage-based duty ratio. By detecting the effective voltage (Vrms) of the distorted waveform and using it to calculate the duty ratio, the system adapts to actual voltage conditions rather than relying on peak values, thereby preventing switching element breakdown while maintaining power control.
2Device complexity
If the duty ratio is changed based on peak voltage and assumed sine wave relationship, then power control is simplified, but accuracy is lost when input voltage waveform is distorted
Solution Approach 1:
The patent introduces feedback by actually measuring the effective voltage of the input waveform using a voltage detector circuit. This measured effective voltage is then fed back to the controller to calculate the accurate duty ratio. This feedback mechanism ensures that the duty ratio calculation reflects the actual voltage conditions, maintaining power control accuracy even with distorted waveforms.
Solution Approach 2:
The patent replaces the theoretical calculation method (assuming sine wave relationship between peak and effective voltage) with an actual measurement method using a voltage detector circuit. This substitution of measurement for calculation enables accurate detection of distorted waveforms and provides the basis for accurate duty ratio control.
3Power
If full-wave rectification is used to convert AC voltage to DC, then power delivery is enabled, but voltage distortion from power generator deterioration affects the relationship between Vrms and Vp
Solution Approach 1:
The system performs self-adjustment by detecting the actual effective voltage of the distorted waveform and using this information to recalculate the duty ratio. This self-service approach enables the system to adapt to voltage waveform distortions without external intervention, maintaining accurate power control across varying electrical conditions.
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 ensures accurate and reliable power control, reducing the risk of switching element breakdown and maintaining stable power delivery to the fuser, even with varying input voltage conditions, thereby improving the performance and longevity of the induction heating device.
Implementation Method 1
a coil which inductively heats a workpiece of a fuser with an input voltage obtained from an alternating current voltage by rectification
Implementation Method 2
induction heating device serving to apply heat to a heating element of a fuser
Data Source
AI summary
An induction heating device including a coil which inductively heats a workpiece of a fuser with an input voltage obtained from an alternating current voltage by rectification; a switching element coupled in series with the coil; a peak voltage detector which detects a peak value of the input voltage; an effective voltage detector which detects an effective value of the input voltage; a crest factor calculator which calculates an actual crest factor of the input voltage based on the peak value of the input voltage and the effective value of the input voltage; and a power controller which achieves control of power to the fuser by controlling the duty ratio of ON and OFF periods of the switching element.