Peak Voltage Detection in Wireless Resonant Transmitters
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Solution Overview
Problem
High frequency resonant power management systems face challenges in accurately measuring peak-to-peak voltage across the primary inductor L in differential class-D configurations due to step jumps and high common mode noise, making it difficult to design a high bandwidth differential amplifier for efficient power transfer in wireless charging systems.
Innovation Solution
A methodology and circuitry that uses a summing block coupled across the terminals of the primary L to generate a DC voltage signal proportional to the peak-to-peak voltage across the primary C, eliminating voltage jumps and common mode noise, and employs a sample/hold circuit with a reasonably fast comparator for low power signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high bandwidth differential amplifier is used to measure peak-to-peak voltage across the primary L or C, then measurement precision is improved, but power consumption increases and device complexity increases
Solution Approach 1:
The patent extracts only the necessary measurement information (peak-to-peak voltage) by using simple voltage detection circuits that sample the voltage at specific points during the switching cycle, rather than using a continuous high-bandwidth amplifier. The peak detector circuit captures voltage extremes and computes peak-to-peak value through basic arithmetic operations, eliminating the need for power-hungry high-frequency amplification.
Solution Approach 2:
The patent uses voltage sampling and holding circuits that create simplified copies of the voltage waveform at critical moments, rather than continuously amplifying the full high-frequency signal. By capturing voltage snapshots at switching events and processing these copied values through low-power digital logic, the system achieves accurate measurement without the power penalty of continuous high-bandwidth analog amplification.
2Measurement precision
If a high bandwidth differential amplifier with good common mode rejection is used, then measurement precision is improved, but device complexity and difficulty of manufacture increase
Solution Approach 1:
The patent extracts the essential measurement function by using simple voltage sampling circuits that detect voltage levels at specific moments in the switching cycle. Rather than designing a complex high-bandwidth differential amplifier with excellent common-mode rejection, the invention uses basic voltage dividers, sample-and-hold circuits, and digital computation to derive peak-to-peak voltage, dramatically reducing design complexity while maintaining measurement accuracy.
Solution Approach 2:
The patent replaces the complex analog high-bandwidth differential amplifier system with a hybrid approach combining simple analog voltage sampling with digital signal processing. By using microcontroller-based voltage measurement and computation, the system eliminates the need for complex analog amplifier design, substituting mechanical/electrical complexity with programmable logic that is easier to manufacture and adjust.
3Productivity
If peak-to-peak voltage measurement is performed in a differential class-D configuration, then power transfer efficiency is improved, but voltage jumps and common mode noise make measurement difficult
Solution Approach 1:
The patent applies preliminary action by sampling the voltage at predetermined moments in the switching cycle, specifically at the rising and falling edges of the gate drive signals. By capturing voltage information at these predetermined critical instants before the problematic voltage jumps occur, the system can accurately measure peak-to-peak voltage without being affected by the subsequent switching transients and common-mode noise inherent in differential class-D configurations.
Solution Approach 2:
The patent implements feedback by using the measured peak-to-peak voltage information to adjust the operating parameters of the power amplifier. The microcontroller processes the voltage measurements and provides feedback control to optimize the class-D amplifier operation, ensuring efficient power transfer while compensating for any measurement uncertainties. This closed-loop approach maintains both efficiency and measurement accuracy.
Data Source
AI summary
A wireless resonant power transmitter includes a first half-bridge and a second half-bridge adapted to be class D driven that are coupled to drive a series resonant circuit including a primary inductor (L) having a high side terminal and a low side terminal, and primary capacitor (C). A peak voltage sensor that includes a summing block is coupled across the high side terminal and the low side terminal of the primary L, and a peak-to-peak voltage detector is coupled to an output of the summing block to generate a DC voltage signal that is proportional to a peak-to-peak voltage across the primary C.