Bootstrap Gate Drive for N-Type Load Switch in Wireless Power Receiver
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Solution Overview
Problem
Existing wireless power receiver integrated circuits require additional capacitors and terminals for over voltage protection (OVP) and output shutdown circuits, leading to increased complexity and cost, particularly due to the need for separate capacitors and terminals for bootstrap and OVP circuits, and the use of charge pumps for gate drive in N-type switches.
Innovation Solution
The integrated circuit design shares bootstrap capacitors and terminals for both OVP and regular operation modes, and uses these capacitors to provide gate drive for N-type load switches, eliminating the need for additional charge pumps and reducing die area and terminal requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate capacitors and terminals are used for OVP circuit, then over voltage protection is achieved, but device complexity and terminal count increase
Solution Approach 1:
The bootstrap capacitors are designed to serve dual purposes: powering the high-side FETs during normal operation and providing over voltage protection when needed. This multi-functionality eliminates the need for separate OVP capacitors and reduces terminal count, directly resolving the contradiction between achieving protection and reducing complexity
Solution Approach 2:
The patent combines the bootstrap circuit and OVP circuit into a unified structure where the same capacitors and terminals are shared between both functions. By merging these previously separate circuits, the design reduces component count and simplifies the overall system while maintaining both bootstrapping and protection capabilities
2Ease of operation
If internal charge pump is used to drive NMOS gate, then gate drive is provided, but die area increases
Solution Approach 1:
The gate drive functionality is extracted from the internal charge pump and relocated to the external bootstrap capacitors. By taking out the charge pump function and implementing it externally through the bootstrap circuit, the patent eliminates the need for large internal switching capacitors, thereby reducing die area while maintaining gate drive capability
Solution Approach 2:
The bootstrap capacitors act as intermediaries between the power source and the NMOS gate. Instead of using an internal charge pump to directly drive the gate, the bootstrap capacitors serve as external energy storage elements that provide the necessary gate drive voltage, reducing the burden on internal circuitry and die area
3Ease of operation
If external charge pump is used to drive NMOS gate, then gate drive is provided, but additional terminals and components are required
Solution Approach 1:
The bootstrap terminals are designed to serve dual purposes: providing gate drive voltage for the NMOS and enabling over voltage protection functionality. This multi-functionality eliminates the need for separate charge pump terminals, reducing the terminal count from four (two for charge pump, two for OVP) to two (bootstrap terminals), thereby resolving the contradiction between providing gate drive and reducing terminal requirements
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 design reduces the number of required capacitors and terminals, simplifies the circuit layout, and lowers costs by reusing bootstrap capacitors for OVP functions and providing gate drive for N-type switches without additional charge pumps, enhancing efficiency and reducing complexity.
Implementation Method 1
a bootstrap capacitor to a high side bootstrap terminal of the rectifier circuit. The load switch driver circuit provides gate drive to the load switch through the bootstrap terminal and the bootstrap capacitor
Data Source
AI summary
Apparatus and methods are provided to power an N-type load switch using a bootstrap capacitor. In one embodiment, an integrated circuit for a wireless power receiver comprises a first rectifier input terminal (RX1), a second rectifier input terminal (RX2), a first bootstrap terminal (HSB1), a second bootstrap terminal (HSB2), and a load switch terminal (LSW). A first and a second bootstrap circuit are coupled with HSB1 and HSB2 to power the rectifier in a regular mode. A load switch driver circuit is coupled between LSW and either HSB1 or HSB2. In the regular mode the load switch driver circuit powers a load switch through a corresponding bootstrap circuit. In an output shutdown mode, an output shutdown circuit is turned on to turn off the load switch. In one embodiment, the load switch is external to the integrated circuit. In another embodiment, the load switch is internal to the integrated circuit.