Constant Current Source Circuit Voltage Feedback Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing constant current source circuits in LSI circuits face challenges in maintaining precise current output at low voltages due to variations in output voltage, leading to high current variations and increased manufacturing costs.
Innovation Solution
A constant current source circuit is designed with a control voltage generation section to detect output voltage and adjust the reference current, using a current mirror section to stabilize output current, thereby reducing the influence of output voltage variations on the output current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the minimum output voltage of a constant current source is reduced, then the operation voltage can be reduced, but the threshold voltage Vt of MOS transistor cannot be reduced proportionally, causing current instability
Solution Approach 1:
The patent employs a feedback mechanism where the output voltage is detected and used to adjust the reference current through a control voltage generation section. This feedback loop compensates for voltage variations and maintains stable current output even when operating at reduced voltages, resolving the contradiction between low operation voltage and current stability.
Solution Approach 2:
The patent dynamically adjusts the reference current based on the output voltage level. By changing the reference current parameter in response to voltage changes, the circuit maintains constant output current despite operating at lower voltages where traditional constant current sources would fail to stabilize current properly.
2Reliability
If MOS transistors with very large area are used to secure voltage margins at low voltages, then current stability improves, but manufacturing cost increases
Solution Approach 1:
The patent uses dynamic adjustment of the reference current based on real-time output voltage detection. Instead of relying on oversized transistors to provide static voltage margins, the circuit dynamically compensates for voltage drops, allowing the use of smaller, more cost-effective transistors while maintaining stability.
Solution Approach 2:
The constant current source circuit monitors its own output voltage and automatically adjusts its reference current to maintain stability. This self-regulating mechanism eliminates the need for oversized transistors that would otherwise be required to provide sufficient voltage headroom, reducing manufacturing costs.
3Device complexity
If conventional constant current source circuits are used at low voltages, then circuit simplicity is maintained, but output current variations increase due to output voltage changes
Solution Approach 1:
The patent introduces a feedback control mechanism that detects output voltage and adjusts the reference current accordingly. This feedback loop significantly reduces output current variations caused by voltage changes, achieving high current precision while adding only moderate circuit complexity through the control voltage generation section.
Data Source
AI summary
A current source includes a first MOS transistor of a first channel type including a drain connected to an output terminal, and a source directly connected to a first power supply, a second MOS transistor of the first channel type including a drain connected to a gate, the gate of the second MOS transistor being connected to the gate of the first transistor, and a source directly connected to the first power supply, a third MOS transistor of a second channel type opposite the first channel type including a drain connected to the drain of the second MOS transistor, a fourth MOS transistor of the second channel type including a drain connected to the source of the third MOS transistor, a gate connected to a first bias voltage, and a source directly connected to second power supply voltage, and a control voltage generator that detects an output voltage on the output terminal and provides a shifted version of the output voltage to the gate of the third MOS transistor.