Full-Bridge Induction Heating Inverter Frequency Control With PSM
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Solution Overview
Problem
Existing induction heating control methods using full-bridge series resonance inverters suffer from significant frequency variation in mid-to-low power sections, leading to increased switching loss and noise due to high switching frequencies.
Innovation Solution
A power control method and device that minimize frequency variation by defining power sections (high, mid, and low power) and using phase shift modulation (PSM) in mid-to-low power sections to control the switching frequency, reducing switching loss and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If pulse frequency modulation (PFM) is used to control output power in mid-to-low power sections, then output power can be reduced, but switching frequency becomes excessively high causing increased switching loss and noise
Solution Approach 1:
The patent divides the power control range into multiple sections (high-power section, mid-power section, and low-power section) with different switching frequency ranges. By segmenting the control strategy according to power levels, the system can apply appropriate frequency limits for each section, preventing excessively high switching frequencies in mid-to-low power sections while maintaining effective power control.
Solution Approach 2:
The patent dynamically adjusts the switching frequency based on the current power section and load conditions. Rather than using a fixed frequency or purely frequency-based PFM control, the system adaptively selects switching frequencies within predetermined ranges for different power sections, optimizing the balance between power control and switching loss reduction.
2Power
If pulse frequency modulation (PFM) is used to control output power in mid-to-low power sections, then output power can be reduced, but frequency variation becomes significant making control unstable
Solution Approach 1:
The patent segments the frequency control into predetermined frequency ranges corresponding to different power sections. By assigning specific frequency ranges to mid-power and low-power sections, the system limits frequency variation within each section, providing more stable frequency control compared to unrestricted PFM.
Solution Approach 2:
The patent changes the control parameter from pure frequency modulation to a combined approach where the switching frequency is constrained within predetermined ranges based on the current power section. This parameter change stabilizes frequency variation while maintaining the ability to control output power across different sections.
3Measurement precision
If high switching frequency is used in low-power section, then power control precision can be improved, but noise increases due to repetitive on and off
Solution Approach 1:
The patent separates the control strategy into different frequency ranges for high-power, mid-power, and low-power sections. For low-power sections, it predetermines appropriate frequency ranges that balance control precision with noise reduction, avoiding excessively high frequencies that cause repetitive switching noise while maintaining sufficient control resolution.
4Device complexity
If single-stage pulse frequency modulation is used for all power sections, then control simplicity is maintained, but switching loss increases significantly in mid-to-low power sections
Solution Approach 1:
The patent divides the power control into multiple sections with different switching frequency strategies. While maintaining relatively simple control logic, it applies segmented frequency range limitations that significantly reduce switching loss in mid-to-low power sections compared to unrestricted single-stage PFM control.
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 proposed solution effectively minimizes frequency variation, reduces switching loss and noise, and enhances operational efficiency by adjusting switching frequencies according to power sections using PSM.
Implementation Method 1
Induction heating is widely used in homes and industries due to advantages of fast heating speed, eco-friendliness of not using fossil fuels, and high efficiency due to direct heating
Implementation Method 2
The existing full-bridge series resonance inverter may include a circuit in which switches S1 to S4 are arranged in a full bridge form as shown in FIG. 1, and the switches S1 to S4 may be switched according to a switching frequency based on pulse frequency modulation (PFM) to output power for induction heating
Data Source
AI summary
A power control method and device for minimizing frequency variation of a full-bridge induction heating inverter are provided. The power control method includes, as a switching frequency for operating the full-bridge induction heating inverter increases, defining a section of output power that is output from the full-bridge induction heating inverter to include at least a mid-power section and a low-power section and in the mid-power section and the low-power section, limiting a variation range of the switching frequency by controlling power of a switch in the full-bridge induction heating inverter using phase shift modulation (PSM).