Load Switch Clamping Circuit for Fast Inductive Current Discharge
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Solution Overview
Problem
Existing load switch circuits face challenges in providing an efficient freewheeling path for inductive current, as external diodes lead to slow discharge speed and internal clamping mechanisms have limited adjustability and high power consumption.
Innovation Solution
A load switch circuit with a clamping module that includes a voltage-current converter and resistors, allowing for dynamic adjustment of the clamping threshold and automatic triggering when the output voltage is lower than ground, reducing power consumption by reusing the power transistor for freewheeling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a freewheeling diode is used externally to protect the power transistor, then the transistor is protected from breakdown, but the discharge speed of inductive load current becomes slow
Solution Approach 1:
The patent combines the protection function and freewheeling function into a single internal circuit structure within the load switch. The clamping module integrates voltage detection, current limiting, and freewheeling path provision, eliminating the need for external diodes while achieving both protection and fast discharge through unified control of the power transistor.
2Reliability
If diodes connected in series are used for clamping the output voltage, then the voltage clamping is achieved, but the adjustability of clamping voltage becomes limited
Solution Approach 1:
The patent employs a dynamic control mechanism where the clamping threshold is not fixed by discrete diode breakdown voltages but can be continuously adjusted through control signals. The controller dynamically regulates the power transistor's gate voltage to maintain the output voltage at the desired clamping level, enabling flexible adaptation to different voltage requirements.
3Device complexity
If internal clamping mechanisms are used to clamp output voltage, then the circuit structure is simplified, but the power consumption increases
Solution Approach 1:
The patent implements periodic or conditional activation of the clamping function. The controller monitors the output voltage and only activates the power transistor for clamping when the voltage exceeds the threshold, rather than maintaining continuous conduction. This on-demand operation significantly reduces power consumption compared to always-on internal clamping mechanisms.
Data Source
AI summary
A load switch circuit includes a power transistor. A first terminal is configured to receive a power supply voltage, and a second terminal is the output terminal of the load switch circuit and is coupled with an external inductive load. A clamping module includes at least a mutually coupled clamping unit and a driving unit. The clamping unit includes a voltage-current converter and a first resistor, the first resistor coupled between the output terminal of the voltage-current converter and the second terminal of the power transistor. The positive input terminal of the voltage-current converter receives the power supply voltage, and the negative input terminal is coupled to the second terminal of the power transistor.