Auxiliary Charge Pump for RFID Rectifier Impedance
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Solution Overview
Problem
RFID transponders with MOSFET-based rectifiers face inefficiencies due to high impedance at varying input voltage levels, particularly during low power operations, leading to increased leakage current and reduced rectification efficiency for both reading and writing procedures.
Innovation Solution
An auxiliary charge pump with a cascade configuration of first and second charge pump stages and a diode clamp, utilizing a regulating transistor to maintain a constant output voltage, reduces impedance and prevents voltage increase, ensuring efficient rectification across varying input voltage levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If MOSFETs are used in rectifier stages, then integration into CMOS processes is improved, but high impedance at varying input voltage levels increases leakage current and reduces rectification efficiency
Solution Approach 1:
The patent implements dynamic biasing of MOSFETs in rectifier stages by connecting auxiliary charge pumps to the gate terminals. The bias voltage is dynamically adjusted based on input voltage levels, allowing the rectifier to maintain optimal performance across varying power conditions. This dynamic control resolves the contradiction by enabling CMOS integration while compensating for impedance variations that cause efficiency losses.
Solution Approach 2:
The patent changes the operating parameters of MOSFETs by applying auxiliary bias voltages through charge pumps. By modifying the gate-source voltage parameter dynamically, the system maintains low impedance and high rectification efficiency across different input voltage levels, thus resolving the contradiction between CMOS compatibility and reliable rectification performance.
2Reliability
If auxiliary charge pumps are used to maintain constant bias, then rectification efficiency is improved, but device complexity increases
Solution Approach 1:
The patent merges the auxiliary charge pump functionality with the existing rectifier stage circuitry by integrating the charge pumps directly into the rectifier block. This consolidation reduces overall device complexity while maintaining the efficiency benefits of dynamic biasing, as the auxiliary circuits share common structures and processes with the main rectifier.
Solution Approach 2:
The auxiliary charge pumps are controlled by detection circuits that automatically sense input voltage levels and adjust bias accordingly. This self-service mechanism eliminates the need for complex external control systems, reducing device complexity while maintaining high rectification efficiency through automatic adaptation to varying power conditions.
3Use of energy by moving object
If voltage biased diodes are used in charge pump stages, then low power operation is achieved, but higher impedance increases leakage current at higher input power levels
Solution Approach 1:
The patent implements dynamic switching between different biasing modes for the charge pump stages. At low input power levels, voltage biased diodes provide low power operation. At higher input power levels, the system dynamically transitions to a different biasing mode that reduces impedance and minimizes leakage current, thus resolving the contradiction between low power operation and leakage reduction across varying power conditions.
Solution Approach 2:
The patent changes the biasing parameters of the charge pump stages based on input power levels. By adjusting the bias voltage and current parameters dynamically, the system achieves low power operation when needed while preventing excessive leakage current at higher power levels, effectively resolving the energy loss contradiction.
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
The auxiliary charge pump maintains constant bias for MOS devices, enhancing rectification efficiency and reducing leakage current, thereby improving overall performance of RFID transponders across different power levels.
Implementation Method 1
An auxiliary charge pump with a cascade configuration of first and second charge pump stages and a diode clamp, utilizing a regulating transistor to maintain a constant output voltage
Implementation Method 2
The rectifier rectifies and amplifies the voltage of the AC signal to charge a storage capacitor and/or to power digital circuitry of the transponder
Implementation Method 3
The RF interrogating signal induces an AC signal within the loop antenna that is provided to the rectifier
Data Source
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Figure 5
AI summary
The present invention relates in one aspect to an auxiliary charge pump for a RFID rectifier, the charge pump, which comprises a first charge pump stage (11; 111) connected to an input (14; 114), a second charge pump stage (12; 112) connected to the input, a diode clamp (13; 113) connected to an output (15; 115), and a regulating transistor (16; 116) having a gate connected with an output (21; 121) of the first charge pump stage and having a source and a drain, wherein one of the source and the drain is coupled to the diode clamp. In further aspects the invention relates to a RFID transponder, to a multistage rectifier and to a rectifier stage comprising such an auxiliary charge pump.