Primary-Side Voltage Control for Inductive Power Transfer
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Solution Overview
Problem
Existing inductive power transfer (IPT) systems require complex and costly secondary-side controllers to regulate output power, and primary-side power control methods, such as frequency modulation, are difficult to implement effectively without feedback loops, adding complexity and cost.
Innovation Solution
A method to control the output voltage of a pickup in an IPT system by estimating the output voltage from the voltage across the primary conductive path, adjusting the current in the primary conductive path to match the required output voltage, using phase angle and mutual inductive coupling calculations, without the need for communications between the pickup and power supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If secondary-side controllers are used to regulate output power, then power control is achieved, but system complexity and cost increase
Solution Approach 1:
The patent inverts the conventional control architecture by moving the power control function from the secondary side (pickup) to the primary side (power supply). Instead of using secondary-side controllers to regulate output power, the system uses primary-side control circuits to sense and regulate the output, eliminating the need for complex secondary-side power conditioners and switched-mode controllers.
Solution Approach 2:
The patent extracts the power control function from the secondary side and relocates it to the primary side. By taking out the power conditioner and switched-mode controller from the pickup circuit, the system achieves power control without the complexity and cost associated with secondary-side control components.
2Power
If frequency modulation is used for primary-side power control, then power control is achieved, but implementation difficulty and controller complexity increase
Solution Approach 1:
The patent changes the control parameter from frequency modulation to amplitude modulation. Instead of varying the frequency of the primary current to control power, the system modulates the amplitude of the primary current. This simplifies the controller design and makes implementation more practical while achieving the same power control objective.
Solution Approach 2:
The patent replaces the complex frequency modulation mechanism with a simpler amplitude modulation system. By substituting frequency-based control with amplitude-based control, the system achieves power regulation with a less complex controller that is easier to implement and tune.
3Power
If amplitude modulation is used for primary-side power control, then power control is achieved, but feedback loop complexity increases
Solution Approach 1:
The patent introduces an intermediary sensing mechanism that allows the primary side to detect secondary side conditions without requiring complex direct feedback. By using the sensed voltage and current on the primary side as intermediaries, the system can infer secondary side status and adjust primary side control accordingly, simplifying the feedback loop.
Solution Approach 2:
The patent implements a feedback mechanism where the primary side controller senses the output conditions and adjusts the primary current amplitude accordingly. This closed-loop feedback ensures stable power control while maintaining relatively simple circuitry by using the primary side as the control point rather than requiring complex secondary side feedback paths.
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
Enables effective primary-side control of the output voltage, reducing system complexity and cost, improving efficiency and reliability by eliminating the need for secondary-side feedback, while maintaining control over power transfer.
Implementation Method 1
The primary conductive path, typically in the form of an elongated conductive loop or track, is energised by the AC power supply to create a continuously varying magnetic field about the track.
Implementation Method 2
The or each pickup includes an inductive coil, in which a voltage is induced by the changing magnetic flux passing through the coil in accordance with Faraday's law of induction, thereby achieving contactless inductive power transfer.
Data Source
AI summary
A method is provided for controlling the output voltage of a pickup in an inductive power transfer (IPT) system without any additional form of communications for feedback from the pickup to the power supply. The method comprising the steps of deriving an estimate of the output voltage of the pickup from the voltage across the primary conductive path, and adjusting the current in the primary conductive path so that the estimated pickup output voltage matches a required pickup output voltage. In particular, an estimate of the pickup output voltage is derived from the magnitude and phase angle of the voltage in the primary conductive path.