Dual-Mode Constant Voltage Circuit for PSRR and Oscillation Stability
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Solution Overview
Problem
Constant voltage circuits face a trade-off between power supply rejection ratio (PSRR) and oscillation resistance due to parasitic inductance, which affects their reliability in both testing and normal operation, particularly in devices like smartphones and drive recorders.
Innovation Solution
A constant voltage circuit with two operation modes: a test mode for high stability against parasitic inductance and a normal mode for superior PSRR and responsiveness, utilizing a mode selection circuit to adjust operating currents in gain stages and output stage to optimize performance based on the operating mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the constant voltage circuit operates in normal mode with standard operating current, then power supply rejection ratio (PSRR) and responsiveness are superior, but oscillation resistance deteriorates due to parasitic inductance
Solution Approach 1:
The patent implements dynamic operation mode switching between test mode and normal mode based on operational requirements. The mode selection circuit dynamically adjusts the operating state of the constant voltage circuit, enabling it to adapt to different conditions (testing vs. normal operation) and optimize performance characteristics accordingly.
Solution Approach 2:
The patent changes the operating current parameter to resolve the contradiction. In test mode, a first operating current is used that provides high stability against parasitic inductance, while in normal mode, a second operating current is used that provides superior PSRR and responsiveness. This parameter change allows the circuit to optimize for different operational requirements.
2Object-affected harmful factors
If the constant voltage circuit is designed for high stability against parasitic inductance, then oscillation resistance improves, but power supply rejection ratio and responsiveness deteriorate
Solution Approach 1:
The circuit dynamically switches between two operational states (test mode and normal mode) depending on whether stability against parasitic inductance or PSRR performance is the priority. This dynamic adaptation allows the circuit to achieve high stability when needed without permanently sacrificing PSRR characteristics.
Solution Approach 2:
The operating current parameter is changed based on the operational mode. In test mode, the first operating current is selected to maximize stability against parasitic inductance, while in normal mode, the second operating current is selected to maximize PSRR and responsiveness, thus resolving the trade-off through conditional parameter optimization.
3Device complexity
If a single operation mode is used for both testing and normal operation, then device complexity is reduced, but reliability deteriorates due to inability to optimize for different conditions
Solution Approach 1:
The constant voltage circuit is designed with multi-functionality to operate effectively in both test mode and normal mode. The mode selection circuit and configurable operating currents enable the same hardware to fulfill different functional requirements (testing with high stability vs. normal operation with high PSRR), thus achieving universality without requiring separate dedicated circuits for each mode.
Data Source
AI summary
According to one embodiment, a constant voltage circuit includes: a first gain stage that outputting a first voltage amplifying a difference voltage between a divided voltage of an output voltage and a reference voltage; a second gain stage outputting a second voltage amplifying the first voltage; a second transistor, one end of which is coupled to the input voltage terminal, and other end of which is coupled to an output voltage terminal, controlling the output voltage to be constant in accordance with the second voltage applied to the gate; and a first circuit selecting one of a first operation mode and a second operation mode. When the first operation mode is selected, a first current flows to the first node, and when the second operation mode is selected, a second current flows to the first node.