Class E Coil Driver Optimizes Switch On Time for ASK Modulation
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Solution Overview
Problem
Conventional wireless power transfer systems for implanted medical devices require a bulky coil driver with many discrete components, leading to high power consumption and a large external controller, which is not suitable for portable and lightweight applications.
Innovation Solution
A feedback-controlled coil driver that optimizes the switch 'on time' of the LC tank circuit, reducing power dissipation and minimizing the number of discrete components by using a capacitor to modulate the power signal and a feedback loop to control the switch 'on time', allowing for efficient power transfer without manual adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional class E amplifier coil driver is used, then power transfer function is achieved, but the driver requires many discrete components (capacitors CT1, CT2 and RF choke LC) resulting in large size and high power consumption
Solution Approach 1:
The patent combines multiple discrete components (capacitors and RF choke) into an integrated LC tank circuit with inductor LP and capacitor CP. This merging reduces the number of separate components while maintaining the power transfer function, directly addressing the contradiction between power consumption and device complexity.
Solution Approach 2:
The LC tank circuit serves multiple functions: it acts as both the resonant circuit for power transfer and the filtering element, replacing the separate RF choke and capacitors. This multi-functionality reduces component count and simplifies the overall driver architecture.
2Weight of moving object
If discrete components are used in the coil driver, then the power transfer function is achieved, but the external controller becomes large and bulky
Solution Approach 1:
By merging the RF choke and capacitors into a single LC tank circuit structure, the physical footprint of the external controller is reduced. The integrated design eliminates the need for multiple discrete components, directly addressing the size reduction requirement for portable applications.
3Productivity
If manual adjustment of inductance and capacitance values is used to optimize switch on time, then maximum power transfer is achieved, but the system requires manual intervention and complex component selection
Solution Approach 1:
The LC tank circuit is designed to self-resonate at the operating frequency, automatically optimizing the power transfer without requiring manual adjustment of inductance or capacitance values. The circuit self-regulates the switch on time through its resonant characteristics, eliminating the need for manual intervention.
Solution Approach 2:
The patent utilizes the resonant frequency parameter of the LC tank circuit to automatically determine the optimal switch on time. By operating at the resonant frequency where XL = XC, the system achieves maximum power transfer without manual parameter adjustment.
4Adaptability or versatility
If a capacitor is coupled into the coil circuit for ASK modulation, then power signal modulation is achieved, but power is dissipated on series elements increasing power consumption
Solution Approach 1:
The modulation capacitor CM is integrated into the LC tank circuit rather than being connected in series with external elements. This merging allows ASK modulation to be achieved while avoiding power dissipation on series elements, as the capacitor operates within the resonant circuit where reactive power is exchanged rather than dissipated.
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 results in a minimized power consumption and reduced component count, enabling a smaller, more efficient coil driver that maximizes the ratio of peak coil current to delivered power, suitable for portable and transcutaneous power transfer applications.
Implementation Method 1
a series resonant circuit including a series resonant inductor LP and a series resonant capacitor CP
Implementation Method 2
a series resonant circuit including a series resonant inductor LP and a series resonant capacitor CP
Implementation Method 3
at a resonant frequency of the series resonant circuit
Implementation Method 4
a primary coil LP, which inductively couples and powers secondary coil, LS
Data Source
AI summary
A feedback controlled coil driver with ASK modulation is disclosed. A class E coil driver drives an LC circuit to generate a magnetic signal via the inductor. A modulation capacitor is coupled to the LC circuit to modulate the coil driver signal. The voltage across the coil driver switch is sampled. The difference between the sampled voltage and a reference voltage is integrated and compared to a ramp voltage to obtain an optimal on time for the coil driver switch such that coil current is maximized.