Wireless Charger Charge Pump for Low-Frequency Bootstrap Drive
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Solution Overview
Problem
The challenge lies in using a single antenna for both wireless charging and secure wireless data transfer, where the lower operating frequency for data transfer results in undercharged bootstrap capacitors, leading to improper operation of the bridge rectifier.
Innovation Solution
A wireless charging and data transmission system with a full bridge circuit formed by parallel half bridges, utilizing a charge pump circuit to generate and maintain a master bootstrap voltage, and switch circuits to couple nodes during conduction periods, ensuring the bootstrap voltage remains above the rectified voltage, thus maintaining proper operation of high-side transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a single antenna is used for both wireless charging and secure wireless data transfer, then device space is saved, but the bootstrap capacitors are not fully charged at lower operating frequencies, causing the bridge to fail to operate properly
Solution Approach 1:
A charge pump circuit is introduced as an intermediary component between the antenna and the bridge rectifier. This charge pump actively manages the bootstrap capacitor charging process, ensuring sufficient voltage is maintained on the capacitors even during low-frequency data transfer operations, thereby enabling reliable bridge operation across both wireless charging and data transfer modes
Solution Approach 2:
The system dynamically adjusts operating parameters by switching between different modes: during wireless charging, the bridge operates at high frequency with standard bootstrap charging, while during data transfer, the charge pump activates to maintain bootstrap capacitor voltage despite the lower operating frequency, effectively adapting the voltage parameters to match operational requirements
2Adaptability or versatility
If the bridge operates at lower frequency for secure data transfer, then data transfer function is enabled, but the bootstrap capacitors remain undercharged, preventing proper high-side transistor operation
Solution Approach 1:
The charge pump circuit performs preliminary charging action on the bootstrap capacitors before the high-side transistors need to switch. By proactively maintaining the capacitor voltage through controlled charging cycles managed by the state machine, the system ensures that sufficient voltage is available whenever high-side switching is required, regardless of the overall operating frequency
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 solution enables efficient operation of the wireless charging and data transmission system by maintaining the bootstrap voltage above the rectified voltage, ensuring the high-side transistors are sufficiently turned on, even during low-frequency data transfer, preventing discharge and maintaining system functionality.
Implementation Method 1
a charge pump circuit to generate and maintain a master bootstrap voltage at a master node as being equal to a voltage at a supply node plus a given voltage
Implementation Method 2
a capacitor coupled between the master node and the voltage at the supply node and holding the master bootstrap voltage
Implementation Method 3
a comparator configured to compare the feedback voltage to a reference voltage and generate a comparison output based thereupon
Data Source
Figure 1
Figure 2
AI summary
A wireless charging and data transmission system (15) that includes first (MN2, MN4) and second (MN1, MN3) half-bridges coupled in parallel between supply (VRECT) and ground nodes. Each half-bridge includes high-side (MN3, MN4) and low-side (MN1, MN2) transistors. A first high-side driving circuit (8) drives the control terminal of the high-side transistor (MN4) of the first half-bridge (MN2, MN4) with a first bootstrap voltage (BOOT1) at a first node (N8), and a second high-side driving circuit (7) drives the control terminal of the high-side transistor (MN3) of the second half-bridge (MN1, MN3) with a second bootstrap voltage (BOOT2) at a second node (N9). A charge pump circuit (10) generates and maintains a master bootstrap voltage (BOOT) at a master node (N2), which is equal to the voltage at the supply node (VRECT) plus a given voltage. A switch circuit couples the master node (N2) to the first node (N9) during the low-side conduction period of the first half-bridge (MN2, MN4) and couples the master node (N2) to the second node (N9) during the low-side conduction period of the second half-bridge (MN1, MN3).