LDO Overcurrent Protection Using Current Mirror Feedback
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Solution Overview
Problem
Current LDO circuits lack overcurrent protection, leading to potential device damage and system malfunctions due to excessive current, which compromises their reliability and stability.
Innovation Solution
An LDO circuit device incorporating an overcurrent protection module with a series structure of resistors and error amplifiers that adjusts gate drive signals to mirror and regulate output current, utilizing P-type and N-type power switches to limit current flow when it exceeds safe levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an overcurrent protection module is added to the LDO circuit, then the reliability of the LDO circuit is improved, but the device complexity increases
Solution Approach 1:
The patent introduces a current mirror circuit as an intermediary mechanism between the output current and the control element. The current mirror circuit copies the output current through transistors Q1 and Q2, and this copied current is then used by the error amplifier to generate the control signal. This intermediary approach allows the system to monitor and control output current without directly interfering with the main power transmission path, thus improving reliability while maintaining relatively simple device structure.
Solution Approach 2:
The patent implements a feedback mechanism where the error amplifier continuously monitors the output current (through the current mirror) and adjusts the gate voltage of the pass transistor accordingly. When the output current exceeds the desired level, the error amplifier reduces the gate voltage to limit the current. This closed-loop feedback control ensures reliable operation by automatically responding to overcurrent conditions, while the feedback path uses simple components that minimize added complexity.
2Stability of the object's composition
If the LDO circuit includes overcurrent protection, then the stability of the LDO circuit is improved, but the manufacturing complexity increases
Solution Approach 1:
The patent merges the overcurrent protection function with the existing LDO circuit structure by integrating the current mirror circuit and error amplifier into the same chip. The current mirror transistors Q1 and Q2 share the same substrate and fabrication process with the main pass transistor. The error amplifier is also implemented using standard CMOS processes. This merging approach ensures stable operation through coordinated control while maintaining ease of manufacture by using unified fabrication processes and integrated circuit techniques.
Solution Approach 2:
The current mirror circuit creates a copy of the output current using transistors Q1 and Q2 with matched characteristics. This copied current signal is then used by the error amplifier for control purposes. The copying mechanism provides stable and accurate current sensing without requiring additional external components or complex manufacturing steps, as the mirror transistors are fabricated using the same process as the main circuit elements.
Data Source
AI summary
Embodiments described herein relate to an LDO circuit device and overcurrent protection circuit of an LDO circuit. An overcurrent protection circuit is added to an LDO circuit to process an output current signal of the LDO circuit. When the output current signal of the LDO circuit increases, a voltage of a gate drive signal of a power switch in the LDO circuit is increased through adjustment performed by the overcurrent protection circuit, thereby declining the current capability of the power switch in the LDO circuit and restricting an output current thereof from continuing to increase. After feedback regulation, the output current of the LDO finally reaches to a stable value.