Load Switch Inrush Current Control via Dual Adjustment Stages
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Solution Overview
Problem
Conventional charge switches face operational dangers due to excessive positive and negative inrush currents when power supply is turned on or off, with existing solutions either failing to limit negative inrush currents or increasing circuit complexity and energy consumption.
Innovation Solution
An electronic circuit with a comparison stage that determines the direction of inrush currents and activates specific adjustment stages to limit either positive or negative inrush currents, using a pMOS switching transistor and current mirror modules to manage the gate voltage of the transistor, thereby controlling inrush currents with low complexity and energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a conventional charge switch with a P-type MOS transistor is used to obtain lower resistance in the on state, then the switching performance is improved, but excessive positive and negative inrush currents occur when power supply is turned on or off
Solution Approach 1:
The control circuit activates the first adjustment stage before the positive inrush current reaches dangerous levels by detecting when the input voltage exceeds the output voltage. This preliminary detection and response limits the peak current before it can cause operational damage. Similarly, the second adjustment stage is preliminarily positioned to handle negative inrush currents when the output voltage exceeds the input voltage.
Solution Approach 2:
The comparison stage continuously monitors the voltage difference between input and output terminals, providing real-time feedback to the control circuit. This feedback mechanism enables dynamic adjustment of the MOS transistor gate voltage through the adjustment stages, allowing the system to respond automatically to inrush current conditions and maintain safe operating levels.
2Object-affected harmful factors
If a conventional solution is used to control positive inrush current, then positive inrush current is limited, but negative inrush current cannot be limited
Solution Approach 1:
The control circuit is designed with dual adjustment stages that can handle both positive and negative inrush current scenarios. The first adjustment stage manages positive inrush currents when input voltage exceeds output voltage, while the second adjustment stage manages negative inrush currents when output voltage exceeds input voltage, making the system universally applicable to both current directions.
Solution Approach 2:
The system dynamically switches between the first and second adjustment stages based on the real-time voltage comparison result. When VIN > VOUT, the first stage is activated; when VOUT > VIN, the second stage is activated. This dynamic adaptation allows the circuit to respond appropriately to different inrush current conditions without requiring separate dedicated circuits for each case.
3Measurement precision
If a precise current source based on bandgap principle is used, then inrush current control precision is improved, but circuit complexity and energy consumption increase
Solution Approach 1:
The invention extracts only the essential voltage comparison function needed for inrush current control, eliminating the complex bandgap reference circuitry. By using a simple voltage comparator to detect the direction of inrush current and activating appropriate adjustment stages, the system achieves sufficient control precision without the overhead of precise current source implementation.
Solution Approach 2:
The control circuit uses simple, low-cost components such as voltage comparators and adjustment stages rather than expensive precise current sources. The system accepts that the control mechanism needs to be active only transiently during inrush events, allowing the use of simpler components that are sufficient for the temporary control requirement rather than investing in permanently active high-precision circuits.
Data Source
AI summary
An electronic circuit includes a switch coupled between an input terminal intended to receive a first voltage and an output terminal coupled to a decoupling capacitor and intended to also be coupled to a load. A comparison stage is configured to compare the first voltage and a second voltage that is present at the output terminal. A first adjustment stage is configured to limit a positive inrush current flowing between the input terminal and the output terminal and a second adjustment stage is configured to limit a negative inrush current flowing between the output terminal and the input terminal. A control circuit is configured to activate either the first adjustment stage or the second adjustment stage as a function of a result of the comparison.