Voltage Regulator Adaptive Current Limiting
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Solution Overview
Problem
Conventional voltage regulators for mobile devices experience prolonged rise times in output voltage due to unnecessary current limiting by first output current limiting circuits, which are activated even when the input voltage is slowly increasing, leading to inefficient charging of external capacitors.
Innovation Solution
A voltage regulator with a detecting circuit to assess the rise speed of the input voltage, allowing the first output current limiting circuit to operate only when the rise speed is fast, and switching to a second output current limiting circuit with a higher current limit value after a predetermined time, thereby controlling the output current and reducing rush currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the first output current limiting circuit is activated to limit rush current, then the output stage transistor is protected from excessive current, but the rise time of the output voltage becomes longer due to unnecessary current limiting when input voltage increases slowly
Solution Approach 1:
The patent applies dynamics by making the current limiting circuit adaptive rather than static. The detecting circuit continuously monitors the rise speed of the input voltage and dynamically adjusts which current limiting circuit is active. When the input voltage rises quickly, the first current limiting circuit with lower limit value is activated to protect against rush current. When the input voltage rises slowly, the second current limiting circuit with higher limit value takes over to allow faster output voltage rise, thus resolving the contradiction between protection and speed.
Solution Approach 2:
The patent changes the parameter of current limit value based on the rising speed of input voltage. The system switches between two different current limit values (first current limit value and second current limit value) depending on the detected rise speed. This parameter change allows the system to optimize between protection (lower current limit) and performance (higher current limit) dynamically, preventing unnecessary current limitation that would extend the output voltage rise time.
2Object-generated harmful factors
If the first output current limiting circuit limits the drain current of the output stage transistor, then rush current is controlled, but the current available for charging external capacitors is reduced, prolonging the voltage rise time
Solution Approach 1:
The system dynamically selects between two current limiting modes based on the actual operating conditions. The detecting circuit monitors whether the input voltage is rising quickly or slowly, and accordingly activates either the first current limiting circuit (for rapid rise conditions to limit rush current) or the second current limiting circuit (for slow rise conditions to maximize charging current). This dynamic adaptation resolves the contradiction between limiting harmful rush current and maintaining fast charging speed.
Solution Approach 2:
The patent changes the current limit parameter based on the rising speed condition. When input voltage rises slowly, the system uses a higher current limit value that allows more current to charge external capacitors without creating harmful rush current. When input voltage rises quickly, a lower current limit value is applied to suppress rush current. This conditional parameter change optimizes both rush current control and capacitor charging speed.
3Device complexity
If a single current limiting circuit is used, then the circuit structure is simple, but it cannot adapt to different input voltage rise speeds, causing unnecessary current limitation
Solution Approach 1:
The patent segments the current limiting function into two separate circuits: a first output current limiting circuit for handling rapid voltage rises and a second output current limiting circuit for handling slow voltage rises. Each circuit is optimized for its specific function, with the first circuit having a lower current limit for rush current protection and the second circuit having a higher current limit for efficient charging. This segmentation allows the system to adapt to different operating conditions without requiring a complex single circuit that tries to handle all scenarios.
Solution Approach 2:
The current limiting system achieves multi-functionality by incorporating two current limiting circuits that can operate in different conditions. The system universally handles both rapid voltage rise scenarios (using the first current limiting circuit) and slow voltage rise scenarios (using the second current limiting circuit). This multi-functional approach allows a single current limiting subsystem to adapt to various input voltage conditions, improving versatility without excessive complexity.
Data Source
AI summary
Provided is a voltage regulator in which a rush current of an output circuit can be limited and a rise time of an output voltage is short. The voltage regulator includes a first output current limiting circuit and a second output current limiting circuit which are used to control the output circuit, and a detecting circuit for detecting a rise speed of an input voltage. The operation of the first output current limiting circuit whose detection current value is low is controlled by the detecting circuit.