Bias Voltage Circuit for Accurate Replica Current Sensing
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Solution Overview
Problem
Existing replica-based current monitoring circuitry in switching circuits, such as boost converters, suffers from inaccuracies due to drift in gate drive voltage differences between the switch and replica devices, leading to measurement errors.
Innovation Solution
A multiplexer circuit is introduced to select between a fixed voltage and a floating voltage, ensuring accurate gate drive voltage is supplied to replica devices, maintaining common mode voltage and safe operating area, thereby minimizing measurement errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a floating voltage is used to drive the replica sense device gate, then the gate drive voltage tracks the switch gate voltage, but when the switch is off, the floating voltage becomes undefined causing measurement errors
Solution Approach 1:
The patent introduces a multiplexer circuit as an intermediary between the floating voltage source and the replica sense device gate. The multiplexer selects between the floating voltage (when switch is on) and a fixed reference voltage (when switch is off), ensuring the replica device always receives a valid, stable gate drive voltage. This resolves the contradiction by mediating the transition between voltage sources based on switch state.
Solution Approach 2:
The gate drive voltage supply is made dynamic by implementing state-dependent selection. The multiplexer circuit dynamically switches between providing the floating voltage (which tracks the switch gate voltage during conduction) and a fixed reference voltage (during non-conduction), adapting the voltage source to the operational state of the main switch to maintain measurement accuracy and device reliability.
2Measurement precision
If the multiplexer circuitry is added to select between floating and fixed voltages, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The multiplexer circuit is designed to perform multiple functions: it acts as a voltage selector for the replica sense device, provides a default reference voltage level, and enables the circuit to operate correctly in both switch on and off states. This multi-functionality justifies the added complexity by consolidating several requirements into a single circuit component.
Solution Approach 2:
The patent changes the voltage parameter supplied to the replica sense device gate based on the switch state. By implementing state-dependent voltage selection through the multiplexer, the circuit adapts the gate drive voltage parameter to maintain optimal operating conditions, improving measurement accuracy despite the increased circuit complexity.
Data Source
AI summary
Circuitry for supplying a bias voltage to a replica sense device of current sensing circuitry for a switch of a switching circuit, the circuitry comprising: multiplexer circuitry configured to receive a first voltage and a second voltage, wherein the first voltage is a floating voltage and the second voltage is a fixed voltage, wherein the multiplexer circuitry is configured to select and output one of the first voltage and the second voltage, such that the first voltage is output by the multiplexer circuitry when the switch is switched on and the second voltage is output by the multiplexer circuitry when the switch is switched off.