Constant Current Source Calibration for Multi-Channel Current Consistency
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Solution Overview
Problem
Constant current source circuits face issues with poor current consistency among individual channels due to factors like input offset voltage of operational amplifiers and threshold voltage deviations caused by parameter mismatches in MOS tube devices.
Innovation Solution
A calibration circuit that adjusts the drain voltage of MOS tubes by changing the current flowing through a resistor, allowing for precise adjustment of output current by varying the resistance or current, thereby ensuring consistent current output across channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a current mirror is used to determine output current, then the circuit structure is simple, but the current consistency among individual channels is poor
Solution Approach 1:
The patent changes the drain voltage parameter of the MOS tube in the output channel by adjusting the current through a resistor, rather than relying on fixed current mirror ratios. This parameter adjustment compensates for process deviations and improves current consistency among channels while maintaining circuit simplicity
Solution Approach 2:
The patent introduces a resistor as an intermediary element between the bias voltage and the MOS tube drain. By adjusting the current through this resistor, the drain voltage can be precisely controlled to compensate for mismatches, achieving better current consistency without complicating the overall circuit structure
2Stability of the object's composition
If operational amplifiers are used to clamp drain potentials, then the constant current output is stable, but the input offset voltage causes drain voltage deviations among channels
Solution Approach 1:
The patent employs operational amplifiers with feedback mechanisms to clamp the drain potentials of MOS tubes to a reference voltage. This feedback control ensures stable constant current output while the adjustable resistor allows compensation for offset voltage effects, maintaining both stability and precision
Solution Approach 2:
The patent performs preliminary calibration by adjusting the resistor current to set the drain voltage before the constant current operation begins. This preliminary action compensates for offset voltages and ensures that subsequent current output remains consistent across channels
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 effectively addresses the issue of current inconsistency by calibrating drain voltages, ensuring a stable and precise constant current output, independent of operational amplifier offset voltages and MOS tube parameter mismatches.
Implementation Method 1
adjusting a voltage drop across two ends of the resistor; changing the current flowing through a resistor, allowing for precise adjustment of output current by varying the resistance or current
Data Source
AI summary
The present disclosure relates to a constant current source calibration circuit, a constant current source drive circuit, a drive chip, and an electronic device. The current calibration circuit includes a resistor and a calibration circuit connected to the resistor for adjusting a voltage drop across two ends of the resistor; and a selector or a switch connected to the two ends of the resistor, and configured to select one end of the resistor to be connected to a constant current source output channel and the corresponding other end to be supplied with a first bias voltage VD. Since the first bias voltage VD is a fixed constant, the voltage drop across the two ends of the resistor is adjusted.