Digitally Self-Calibrated ZVS Detection for Wireless Power EMI Reduction
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Solution Overview
Problem
Wireless power systems face significant electromotive interference (EMI) due to switching inverter stages, which is mitigated by conventional smoothing capacitors that slow down switching edges and increase power dissipation.
Innovation Solution
A digitally self-calibrated zero-voltage switching (ZVS) detection system that continuously calibrates the switching point of the inverter using a calibration loop with a state machine, a divider, a calibration ramp generator, a comparator, multiplexers, and a digital feedback circuit to optimize switching points and reduce EMI.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional smoothing capacitors are used to mitigate EMI, then EMI is reduced, but switching edges are slowed down and power dissipation increases
Solution Approach 1:
The patent removes the smoothing capacitor from the circuit entirely. Instead of using a capacitor to mitigate EMI, the invention employs a ZVS detection system with a comparator that detects when the switching node voltage reaches zero, enabling switching to occur at the optimal moment without requiring energy-dissipating smoothing components.
Solution Approach 2:
The patent implements a feedback mechanism where the comparator continuously monitors the switching node voltage and provides feedback signals to control the switching timing. This closed-loop feedback enables precise zero-voltage detection and timing control, allowing EMI reduction without the energy losses associated with conventional capacitor-based approaches.
2Object-affected harmful factors
If conventional smoothing capacitors are used to mitigate EMI, then EMI is reduced, but switching edges are slowed down
Solution Approach 1:
The patent removes the smoothing capacitor that was causing the slowing of switching edges. By eliminating this component and using active zero-voltage detection instead, the circuit maintains fast switching edges while still mitigating EMI through precise timing control.
Solution Approach 2:
The feedback-based ZVS detection system provides real-time information about the switching node voltage state, enabling the control logic to switch at precisely the right moment. This active control mechanism maintains fast switching edges without the edge-slowing effect of passive capacitor-based EMI mitigation.
3Loss of energy
If a digitally self-calibrated ZVS detection system is implemented, then EMI and power dissipation are reduced, but device complexity increases
Solution Approach 1:
The patent integrates multiple functions into a unified ZVS detection system. The same comparator and control logic that detect zero-voltage conditions also manage the calibration process and generate the calibrated threshold, eliminating the need for separate calibration circuits and reducing overall system complexity despite the added intelligence.
Solution Approach 2:
The system performs self-calibration automatically without requiring external intervention or separate calibration equipment. The calibration ramp generator and comparator work together to autonomously determine and store the appropriate threshold values, making the system self-configuring and reducing the complexity burden of the enhanced functionality.
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 reduces EMI and power dissipation by continuously optimizing switching points, enhancing the efficiency and performance of wireless power transmission.
Implementation Method 1
a transmitter driving a transmit coil and a receiver with a receiver coil placed proximate to the transmit coil. The receiver coil receives the wireless power generated by the transmit coil
Implementation Method 2
a comparator; a first multiplexer coupled to receive a divider output signal from the divider and a calibration ramp signal from the calibration ramp generator and provide a signal to the comparator based on a calibration enable signal
Data Source
AI summary
In some embodiments, a threshold calibration system to provide a zero voltage switching signal is presented. The system includes a divider coupled to a switching node; a calibration ramp generator; a reference voltage generator; a comparator; a first multiplexer coupled to receive a divider output signal from the divider and a calibration ramp signal from the calibration ramp generator and provide a signal to the comparator based on a calibration enable signal; a second multiplexer coupled to receive reference voltages from the reference voltage generator, the second multiplexer provided a threshold signal to the comparator; and a digital feedback circuit receiving an output signal from the comparator and providing the zero voltage switching signal.