Bypass Mode Power Converter for Wireless Energy Transfer
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Solution Overview
Problem
Existing wireless power transfer systems face challenges in energy efficiency and reliability, particularly when using n-type high-side transistors in DC-DC converters, as they require complex circuitry and are prone to over-currents during bypass operations.
Innovation Solution
A power converter with a bypass mode that utilizes a high-side n-type transistor, enabled by a charge pump and a bootstrap circuit, which allows for efficient operation by reducing the voltage differential and preventing over-currents through a bypass switch protection system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a high-side n-type transistor is used in the DC-DC converter, then energy efficiency is improved, but the circuit complexity increases and over-current risks arise during bypass operations
Solution Approach 1:
A bootstrap circuit is introduced as an intermediary mechanism to generate the required gate drive voltage for the high-side n-type transistor. This bootstrap circuit uses a capacitor that is charged during the off-state of the transistor and discharged during the on-state, providing the necessary voltage boost without requiring a complex isolated power supply or driver circuitry.
Solution Approach 2:
The bootstrap capacitor is pre-charged to the required voltage level before the high-side transistor needs to be activated. This preliminary charging action ensures that when the transistor needs to turn on, the gate drive voltage is already available, eliminating the need for complex real-time voltage generation circuits.
2Loss of energy
If the DC-DC converter operates in bypass mode, then energy losses are reduced, but over-current protection circuitry is required
Solution Approach 1:
A feedback mechanism is implemented that monitors the voltage differential between input and output terminals. When the voltage differential drops below a threshold indicating bypass mode operation, the feedback circuit automatically activates the bypass switch. This feedback-based control eliminates the need for complex over-current protection circuitry by preventing over-current conditions through intelligent switching based on real-time voltage monitoring.
Solution Approach 2:
The bypass switch protection system operates autonomously by using the voltage differential itself as the control signal. The system self-regulates by comparing the voltage differential against a reference threshold and automatically switching the bypass mode on or off, without requiring external protection circuitry or complex control logic.
3Adaptability or versatility
If the voltage differential between input and output terminals is reduced, then bypass mode activation is enabled, but precise voltage threshold detection is required
Solution Approach 1:
Instead of requiring precise detection of a single voltage threshold, the system uses a hysteresis band with upper and lower voltage thresholds. When the voltage differential exceeds the upper threshold, bypass mode is activated; when it drops below the lower threshold, bypass mode is deactivated. This partial action approach with a voltage window provides robust operation without requiring ultra-precise single-threshold detection, tolerating variations in operating conditions.
Data Source
AI summary
A system and method of wireless power transfer using a power converter with a bypass mode includes a power converter. The power converter includes a pulsed switch, a capacitor configured to supply a drive voltage to the pulsed switch, a first circuit configured to charge the capacitor when the power converter operates in a switched mode of operation, and, a second circuit configured to charge the capacitor when the power converter operates in a bypass mode of operation.