NFC Power Harvesting Controller for Depleted Battery Operation
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Solution Overview
Problem
Near field RF communicators face challenges in operating when the primary power supply is insufficient or unavailable, particularly in devices like mobile phones where the battery is depleted, and they need to derive power from a received RF field to maintain functionality and communicate data, especially in scenarios like transport tickets or secure data transfers.
Innovation Solution
A near field RF communicator design incorporating a rectifier to derive power from an RF field, a shunt regulator, a controller, and a secondary power supply (FPSU) that operates only when the primary power supply is inadequate and the received RF field exceeds a certain threshold, ensuring continuous operation by switching on the FPSU under controller control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the NFC communicator relies on the primary power supply (battery), then the device structure remains simple, but the communicator cannot operate when the battery is depleted or removed
Solution Approach 1:
The system dynamically changes the power supply mode by switching between primary battery power and secondary RF field power based on the availability and status of the primary power supply. The controller monitors battery status and activates the secondary power supply derivation circuit only when needed, changing the operational parameters of the power system to maintain reliability without permanent complexity
Solution Approach 2:
The patent introduces a secondary power supply derivation circuit as an intermediary power source that activates only when the primary power supply is insufficient. This intermediary system includes RF field receiving antennas and rectification circuits that convert ambient RF fields into usable power, providing a bridge solution when the primary battery is depleted without requiring a permanent dual-power architecture
2Adaptability or versatility
If the NFC communicator derives power from the received RF field, then it can operate without primary power supply, but the power availability depends on RF field strength and may not be sufficient for all operations
Solution Approach 1:
The system dynamically adjusts the power derivation mode based on real-time conditions. The controller continuously monitors RF field strength, battery status, and power consumption requirements, switching between battery power, RF field power, or a combination thereof. This dynamic adaptation ensures the most reliable power configuration is used for each operational context
Solution Approach 2:
The system prepares for power shortages by having the secondary RF field power derivation circuit ready to activate when the primary power supply becomes insufficient. The controller anticipates power needs and switches to the secondary power source beforehand to prevent operational interruption, cushioning against the risk of power failure
3Power
If the NFC communicator needs to power peripheral devices (secure element, display, interface), then the power requirements increase, but the available power from RF field or depleted battery may be insufficient
Solution Approach 1:
The secondary power supply derivation circuit is designed to provide universal power support for multiple peripheral devices including secure elements, display drivers, and interface systems. The same RF field receiving and rectification infrastructure serves multiple power-intensive functions, allowing a single power management system to handle diverse peripheral power requirements without proportionally increasing complexity
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 near field RF communicators to operate reliably even when primary power is low or unavailable, providing sufficient power to both the communicator and peripheral devices, ensuring uninterrupted data transfer and functionality.
Implementation Method 1
at least one rectifier to provide a rectified supply using the induced voltage
Implementation Method 2
an antenna circuit to couple with the H field of a received RF signal to provide an induced voltage
Data Source
AI summary
A near field RF communicator has an antenna circuit to couple with the H field of an RF magnetic field and a power supply deriver to derive a rectified auxiliary power supply from the received magnetic field. Rectification may be performed using an actively switched rectifier having a passive mode of operation. A sub regulation system is provided to regulate the auxiliary power supply to inhibit the possibility of temporally varying power requirements of the near field RF communicator or its host causing an apparent load modulation of a signal that is transmitted or received by the communicator.