Power Switching Circuit Voltage Selection and Blocking
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Solution Overview
Problem
Dual-interface NFC or RFID tags face issues with power switching circuits getting trapped in certain states due to inadequate voltage selection and blocking mechanisms, leading to improper operation when RF input is absent or below threshold.
Innovation Solution
A power switching circuit incorporating a bandgap reference circuit, supply selection circuit, and voltage blocking circuit (POR) to select the highest available voltage and block lower voltages, ensuring immediate startup and preventing power switches from receiving sub-threshold voltages, thereby preventing the circuit from getting trapped in a certain state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a power switching circuit uses multiple supply voltages from RF and contact interfaces, then the circuit can operate in dual-interface mode, but the circuit may get trapped in certain states due to inadequate voltage selection and blocking mechanisms
Solution Approach 1:
The voltage blocking circuit (POR) performs preliminary action by blocking sub-threshold voltages before they can enter the bandgap reference circuit. This prevents the circuit from getting trapped in invalid states by proactively preventing harmful voltage conditions rather than reacting to them after they occur.
Solution Approach 2:
The supply selection circuit acts as an intermediary between the multiple supply voltage sources (RF and contact interfaces) and the bandgap reference circuit. It selectively connects the highest valid supply voltage to the bandgap reference circuit, mediating between conflicting voltage sources and preventing state trapping issues.
2Reliability
If the bandgap reference circuit receives a sub-threshold voltage, then the circuit may start up improperly, but adding voltage blocking mechanisms increases circuit complexity
Solution Approach 1:
The voltage blocking circuit (POR) performs multiple functions: it blocks sub-threshold voltages, prevents improper startup conditions, and works cooperatively with the supply selection circuit. This multi-functionality reduces the need for separate protection circuits, thereby limiting the increase in overall circuit complexity while improving startup reliability.
3Use of energy by moving object
If the supply selection circuit selects the highest voltage without blocking lower voltages, then power efficiency is improved, but the bandgap reference circuit may receive invalid voltages causing improper operation
Solution Approach 1:
The voltage blocking circuit performs preliminary validation by blocking sub-threshold voltages before they reach the bandgap reference circuit. This allows the supply selection circuit to efficiently select the highest voltage without risking improper operation, as the blocking circuit has already eliminated invalid voltage options.
Solution Approach 2:
The power switching circuit employs feedback mechanisms where the voltage blocking circuit monitors supply voltages and prevents invalid voltages from affecting circuit operation. This feedback loop ensures that only valid voltages are processed by the supply selection circuit, maintaining both power efficiency and operational reliability.
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 solution enables immediate startup of the bandgap reference circuit and prevents the power switching circuit from being trapped in a certain state, ensuring reliable operation by promptly selecting the highest available voltage and blocking lower voltages, thus maintaining efficient power switching in dual-interface tag circuits.
Implementation Method 1
a bandgap reference circuit (BGR) configured to receive an input voltage and to generate a reference voltage in response to receiving said input voltage
Implementation Method 2
a supply selection circuit configured to receive at least two supply voltages, to select the highest voltage of said supply voltages and to provide said highest voltage to the bandgap reference circuit
Implementation Method 3
the power switching circuit further comprises a voltage blocking circuit configured to block the second supply voltage if said second supply voltage is below a threshold
Data Source
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AI summary
According to a first aspect of the present disclosure, a power switching circuit is provided, comprising: a bandgap reference circuit configured to receive an input voltage and to generate a reference voltage in response to receiving said input voltage; a supply selection circuit configured to receive at least two supply voltages, to select the highest voltage of said supply voltages and to provide said highest voltage to the bandgap reference circuit. According to a second aspect of the present disclosure, a corresponding method of operating a power switching circuit is conceived.