Wireless Power Inverter PWM Shaping for Emissions Bandwidth
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Solution Overview
Problem
Burst mode wireless power transfer systems experience undesired electromagnetic emissions due to inefficiencies in power delivery, leading to electromagnetic emissions that fall outside specified bandwidth ranges, affecting operating efficiency and compliance with regulatory standards.
Innovation Solution
The implementation of control circuitry in wireless power transmitters that modifies drive signals for the inverter switching devices to shape the coil current burst envelope using symmetrical or complementary pulse width modulation schemes, ensuring the bandwidth of the wireless power transfer signal falls within a specified range by extending the minimum on time and adjusting pulse widths or amplitudes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If burst mode wireless power transfer is used to enhance operating efficiency, then power delivery efficiency is improved, but electromagnetic emissions fall outside specified bandwidth ranges
Solution Approach 1:
The patent applies dynamics by making the switching device on-time variable and adaptive. The control circuitry dynamically adjusts the on-time of the switching device based on real-time system conditions to shape the coil current burst envelope, ensuring that the bandwidth of wireless power transfer signals remains within specified ranges while maintaining burst mode efficiency. This dynamic adjustment resolves the contradiction by allowing the system to adapt its operational characteristics rather than using fixed timing parameters.
Solution Approach 2:
The patent employs parameter changes by modifying the on-time parameter of the switching device in the inverter circuit. By extending or adjusting the on-time, the control circuitry shapes the coil current burst envelope to control the bandwidth characteristics of electromagnetic emissions. This parameter adjustment allows the system to maintain efficient burst mode operation while ensuring compliance with electromagnetic emission bandwidth specifications.
2Object-affected harmful factors
If the on time of switching devices is extended to shape the coil current burst envelope, then electromagnetic emissions are constrained within specified bandwidth, but the complexity of control circuitry increases
Solution Approach 1:
The patent applies self-service by implementing a control circuitry that autonomously monitors and adjusts the switching device on-time without requiring external intervention. The control circuitry automatically shapes the coil current burst envelope by extending the on-time as needed, and this self-regulating mechanism maintains electromagnetic emissions within specified bandwidth ranges while managing its own operational parameters, thereby reducing the need for additional complex external control systems.
3Object-affected harmful factors
If pulse width modulation signals are used to shape the coil current burst envelope, then bandwidth compliance is achieved, but ripple voltage increases
Solution Approach 1:
The patent employs parameter changes by adjusting the on-time parameter of the switching device in response to ripple voltage conditions. The control circuitry monitors system parameters and dynamically modifies the pulse width modulation signals to shape the coil current burst envelope, thereby maintaining bandwidth compliance while attempting to minimize ripple voltage generation through optimized timing parameters.
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
This approach effectively constrains electromagnetic emissions within a specified bandwidth, enhancing operating efficiency and compliance with regulatory standards by optimizing power transfer and reducing ripple voltage, thereby improving the overall performance of wireless power transfer systems.
Implementation Method 1
Wireless power transfer, in which power is delivered via magnetic/inductive coupling between a power transmitter (PTx) and a power receiver (PRx)
Implementation Method 2
In some applications, burst mode wireless power transfer may be provided to enhance operating efficiency. Bursty operation of wireless power transmitters may result in undesired electromagnetic emissions.
Data Source
AI summary
A wireless power transmitter can include a coil, an inverter coupled to the coil, and control circuitry coupled to the inverter that, responsive to receiving a burst request pulse from a wireless power receiver, initiates inverter operation, driving the coil and powering the receiver. The control circuitry can operate inverter switches so bandwidth of the wireless power transfer signal falls within a specified range by: (a) extending a minimum on time of the switches, (b) modifying pulse width modulation (PWM) drive signals supplied to the switches to shape a coil current burst envelope, and/or (c) modifying PWM signal amplitude supplied to the switches. Modifying the PWM drive signals can include using a symmetrical PWM scheme in which the positive and negative pulses are symmetrical in width on a cycle-by-cycle basis or using a complementary PWM scheme in which the positive and negative pulse widths are complementary on a cycle-by-cycle basis.