Wireless Power Transfer Feedback Control for DC-Link Voltage Stability
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Solution Overview
Problem
Conventional wireless power transfer systems face challenges in maintaining a constant DC-link voltage and preventing overvoltage in small cooking appliances, where load states change frequently, making it difficult to control output power effectively.
Innovation Solution
A wireless power transfer system that includes a wireless power transfer apparatus and a wireless power reception apparatus, where the latter checks the DC-link voltage and transmits data to the former to adjust the power transmission, using an inverter with switching elements to maintain a stable output level, and a controller to adjust the frequency of the current output based on the target level and reference voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the wireless power transfer apparatus controls output power level based on input power variations (conventional method), then the control system is simple, but it cannot maintain constant DC-link voltage when load state changes rapidly
Solution Approach 1:
The patent implements a feedback mechanism where the wireless power reception apparatus monitors its own DC-link voltage and communicates this information back to the wireless power transfer apparatus. The transfer apparatus then adjusts its output power level based on this feedback to maintain constant DC-link voltage. This resolves the contradiction by adding feedback control that stabilizes voltage without requiring complex internal control circuitry in the reception apparatus.
Solution Approach 2:
The wireless power reception apparatus performs self-diagnosis of its DC-link voltage status and autonomously determines the appropriate power level needed. It then communicates this requirement to the transfer apparatus, which adjusts its output accordingly. This self-service approach allows the system to maintain voltage stability without requiring complex control systems in either apparatus.
2Ease of manufacture
If the wireless power transfer apparatus uses a simple control method based on input power, then the control method is easy to implement, but it cannot prevent overvoltage when load state changes rapidly
Solution Approach 1:
The system takes preliminary anti-action by having the reception apparatus monitor DC-link voltage proactively and communicate voltage status to the transfer apparatus before overvoltage damage can occur. The transfer apparatus then preemptively adjusts its output power to prevent overvoltage conditions, rather than reacting after damage has occurred. This resolves the contradiction by maintaining simple control implementation while preventing harmful overvoltage effects.
3Device complexity
If the wireless power transfer apparatus monitors only input power, then the monitoring is simple, but it cannot detect rapid load state changes in the reception apparatus
Solution Approach 1:
The patent establishes a feedback loop where the reception apparatus monitors its own load state and DC-link voltage, then communicates this information to the transfer apparatus. This feedback mechanism allows the transfer apparatus to detect rapid load state changes accurately without requiring complex monitoring systems, as the reception apparatus performs the detection and reports the results.
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 system effectively maintains a constant DC-link voltage and prevents overvoltage in the wireless power reception apparatus, ensuring stable operation and protecting components from damage due to rapid load state changes.
Implementation Method 1
an inverter that outputs a current to the transmitting coil by operating a plurality of switching elements
Implementation Method 2
a magnetic field is changed by an alternating current flowing through a primary coil among two adjacent coils when the alternating current with varying current intensity flows through the primary coil, whereby magnetic flux passing through a secondary coil is changed, and an induced electromotive force is generated on the secondary coil
Data Source
AI summary
A system includes a wireless power transfer apparatus and a wireless power reception apparatus. The wireless power transfer apparatus includes a transmitting coil, an inverter including switching elements, and a first controller configured to calculate an output level of power transmitted through the transmitting coil, receive data on a target level for power transmitted through the transmitting coil from the wireless power reception apparatus, and control the inverter based on comparing the output level and the target level. The wireless power reception apparatus includes a receiving coil, a rectifier configured to rectify power transmitted from the receiving coil, a capacitor connected to the rectifier, and a second controller configured to calculate a voltage applied to the capacitor, determine the target level based on comparing the calculated voltage and a first reference voltage, and transmit the target level to the wireless power transfer apparatus.