Power Control Unit for High-Frequency Dielectric Heating
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Solution Overview
Problem
Existing high-frequency dielectric heating systems face challenges in maintaining consistent output due to variations in magnetron types and temperatures, leading to distorted input current waveforms and inefficient power control.
Innovation Solution
A power control unit that includes an input current detection section and a conversion section to modulate the on-time of a switching transistor, suppressing instantaneous fluctuations in the input current waveform, and a mix circuit to adjust the on-time based on input current and voltage information, ensuring stable output regardless of magnetron variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the output pulse width of the inverter control circuit is adjusted to continuously change the heating output of the magnetron, then the power supplied to the magnetron increases, but the heater temperature cannot be maintained in an appropriate range and the heating output can only be changed in a slight range
Solution Approach 1:
The patent divides the control function into two independent parts: (1) inverter control circuit that supplies power to the magnetron, and (2) separate heater power control that independently regulates heater temperature. This segmentation allows the magnetron power and heater temperature to be controlled independently, resolving the contradiction between expanding heating output range and maintaining heater temperature stability.
Solution Approach 2:
The patent introduces a separate heater power control circuit as an intermediary between the power supply and the heater. This intermediary component decouples the heater power control from the magnetron power control, enabling independent regulation of heater temperature while maintaining stable operation across the full heating output range.
2Reliability
If waveform shaping is performed based on prospective control system to make input current waveform close to sine wave, then power factor improves, but the system cannot follow up variations or types of characteristics of magnetrons, anode temperature fluctuations, and load changes
Solution Approach 1:
The patent employs feedback control by detecting the actual input current waveform and using this information to dynamically adjust the inverter control. The feedback mechanism allows the system to continuously adapt to variations in magnetron characteristics, anode temperature changes, and load conditions while maintaining a sine-wave-like input current waveform and high power factor.
Solution Approach 2:
The patent transitions from a static prospective control system to a dynamic feedback-based control system. The control parameters are continuously adjusted based on real-time detection of operating conditions, enabling the system to adapt dynamically to magnetron variations and maintain optimal performance across different operating states.
3Reliability
If a complex control system with waveform shaping circuit and multiple processing stages is used to correct input current waveform, then input current waveform distortion is reduced, but the system configuration becomes complicated and large-scaled
Solution Approach 1:
The patent extracts the essential waveform shaping function from a complex multi-stage control system and implements it through a simplified inverter control circuit with feedback. By taking out only the necessary control elements and eliminating redundant processing stages, the system achieves effective input current waveform correction with a compact and simple configuration.
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
The solution allows for stable and efficient high-frequency dielectric heating by correcting input current waveforms and improving power factor, even with variations in magnetron types and temperatures, through a simplified and miniaturized system configuration.
Implementation Method 1
an inverter circuit for rectifying AC power supply voltage, converting it into high frequency AC
Implementation Method 2
converting it into high frequency power
Implementation Method 3
magnetron such as a microwave oven
Implementation Method 4
high-frequency dielectric heating
Data Source
Figure 1
Figure 2
Figure 3(a)~3(b)
AI summary
A power control unit for high-frequency dielectric heating not affected by variations in the types or the characteristics of magnetrons, power supply voltage fluctuation, etc., is provided. The unit has an input current detection section 71, 72 for detecting input current of an inverter circuit 10 for rectifying 31 AC power supply voltage 20, performing high frequency switching, and converting into high frequency power, mixes input current waveform information 90 of the input current detection section and power control information 91 for controlling so that output of the input current detection section becomes a predetermined value in a mix circuit 81, outputs ON voltage information 92, makes a comparison between the ON voltage information and a sawtooth wave from a sawtooth wave generation circuit 83 in a PWM comparator 82, performs pulse width modulation, and outputs a drive signal for controlling turning on/off of a switching transistor 39 of an inverter circuit.