Low-Voltage Detection Circuit With Current Mirror Startup Boost
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional low voltage detection circuits in microcomputers face issues with delayed rise of the reference voltage after power-on and failure to maintain a high level of the low voltage detection signal during power supply voltage drops, leading to potential malfunctioning.
Innovation Solution
A low voltage detection circuit incorporating a current mirror formed by first and second transistors, with a load element and auxiliary current transistor to ensure rapid rise of the reference voltage and maintain it during power supply voltage drops, utilizing a P-channel type transistor and current limiting resistor to control auxiliary current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a conventional reference voltage generation circuit using a constant current transistor and load element is used, then the circuit structure is simple, but the reference voltage rises slowly after power-on causing delayed detection
Solution Approach 1:
The constant current generation function is segmented into two transistors (first constant current transistor and second constant current transistor) where the second transistor provides additional current during the rise phase, enabling faster voltage establishment without requiring a completely different circuit architecture
Solution Approach 2:
The second constant current transistor is preliminarily configured to provide auxiliary current during the power-on phase. This preliminary action accelerates the reference voltage rise by supplying additional current when needed most, then automatically退出 once the voltage stabilizes
2Reliability
If the reference voltage rises slowly after power-on, then the circuit structure remains simple, but the low voltage detection signal fails to reach high level causing malfunction
Solution Approach 1:
The comparator output feeds back to control the third transistor, which in turn controls the auxiliary current from the second constant current transistor. This feedback mechanism ensures the detection signal reaches high level reliably by automatically adjusting the current supply based on the actual voltage rise status
Solution Approach 2:
The second constant current transistor is preliminarily configured to provide auxiliary current during the power-on phase. This preliminary action accelerates the reference voltage rise by supplying additional current when needed most, then automatically退出 once the voltage stabilizes
3Measurement precision
If a conventional divider circuit is used to divide the power supply voltage, then the circuit is simple, but the detection fails when voltage drops gradually during normal operation
Solution Approach 1:
The comparator continuously compares the divided voltage with the reference voltage and feeds back to the third transistor. This feedback ensures precise detection during gradual voltage drops by dynamically adjusting the auxiliary current to maintain accurate comparison thresholds throughout the voltage transition
Solution Approach 2:
The third transistor dynamically adjusts the auxiliary current based on real-time voltage conditions. During gradual power supply drops, the transistor remains active longer to maintain precise detection, adapting the circuit behavior to the changing operational phase
Data Source
AI summary
A low voltage detection circuit includes a reference voltage generation circuit, a divider circuit, a comparator that serves as a comparison circuit, and a second constant current transistor connected in series with the divider circuit. An auxiliary current transistor as well as a first constant current transistor is connected in series with a load element. The auxiliary current transistor is controlled by a voltage at a drain of the second constant current transistor. A gate of the second constant current transistor and a gate of the first constant current transistor are connected with each other to form a current mirror. A size of the second constant current transistor is adjusted so that the second constant current transistor can provide a second constant current that is several times larger than a first constant current provided by the first constant current transistor.