Adjustable Current Limiting Circuit for Fast, Protected PMIC Startup
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Solution Overview
Problem
Conventional current limiting circuits in power management integrated chips have a fixed current limiting value, leading to failed boot-ups under heavy loads or damage due to excessive current during short-circuited back-end loads during booting-up.
Innovation Solution
A current limiting circuit with an adjustable current limiting value, comprising a boost unit, variable voltage unit, comparison units, and constant current unit, which controls the state of a transistor to set the current limiting value dynamically, preventing damage from excessive current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the current limiting value is excessively small, then the power management integrated chip cannot establish the voltage within the specified time during booting-up under a heavy-load, but the components are protected from excessive current
Solution Approach 1:
The patent implements dynamic current limiting by using a boost circuit to generate a variable voltage that controls the gate of the isolation transistor. The current limiting value changes dynamically during the booting-up process, starting small to protect components and increasing to enable heavy-load operation within specified time, thus resolving the contradiction between component protection and booting-up speed
Solution Approach 2:
The patent changes the current limiting parameter from a fixed value to a variable value that evolves during operation. By using the boost circuit to generate a time-varying control voltage, the current limiting value transitions from a protective low value to a performance-enabling high value, simultaneously achieving component protection and meeting booting-up time requirements
2Productivity
If the current limiting value is excessively large, then the power management integrated chip can establish voltage quickly during booting-up, but the components are damaged by long-term high current when the back-end load is short-circuited
Solution Approach 1:
The patent uses dynamic control of the isolation transistor gate voltage through the boost circuit and comparison unit. The system continuously monitors the voltage drop across the transistor and adjusts the gate voltage accordingly, enabling high current during normal booting-up while automatically limiting current when abnormal conditions like short-circuit occur, thus preventing component damage
Solution Approach 2:
The patent implements a feedback mechanism where the voltage drop across the isolation transistor is continuously monitored by the comparison unit. This feedback signal controls the gate of the isolation transistor, creating a self-regulating system that maintains safe current levels during short-circuit conditions while enabling fast booting-up under normal conditions, resolving the contradiction between speed and safety
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Prevents failed boot-ups under heavy loads and protects the power management integrated chip from damage due to short-circuited back-end loads by allowing adjustable current limiting, ensuring safe and reliable operation.
Implementation Method 1
The boost unit is configured to cause a voltage at the second terminal of the boost unit to be higher than a voltage at the first terminal of the boost unit
Data Source
AI summary
A current limiting circuit includes a first voltage terminal, a second voltage terminal, a first transistor and a current limiting module. The first transistor includes an input terminal and an output terminal of the first transistor that are connected in series on a path formed by the first voltage terminal and the second voltage terminal. The current limiting module is electrically connected to a control terminal of the first transistor. The current limiting module is configured to output a control signal to the control terminal of the first transistor for controlling a state of the first transistor so that a current limiting value of the current limiting circuit is adjustable.