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 voltage adjustment precision, risking power transistor breakdown.
Innovation Solution
A load switch circuit with a clamping module that includes a voltage-current converter and resistors, generating a reference voltage drop to create a flexible clamping threshold, allowing the power transistor to be dynamically controlled for freewheeling, and automatically triggering the clamp function when the output voltage falls below ground, reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an external freewheeling diode is used to protect the power transistor, then the transistor breakdown is prevented, but the inductive current discharge speed becomes slow
Solution Approach 1:
The patent combines the protection function and fast discharge function into a single integrated circuit structure. The clamping module is integrated within the load switch circuit, merging the protective clamping diode with the power transistor circuitry. This integration allows the circuit to simultaneously achieve transistor protection through clamping and fast discharge through the controlled switching of the power transistor itself, resolving the contradiction between protection reliability and discharge speed.
2Reliability
If series diodes are used for voltage clamping inside the load switch, then the output voltage is clamped, but the voltage adjustment precision is limited to discrete diode breakdown voltages
Solution Approach 1:
The patent changes the clamping mechanism from discrete diode breakdown voltage clamping to continuous adjustable threshold clamping. By using a clamping module with adjustable clamping threshold parameter, the circuit can precisely control the clamping voltage level continuously rather than in discrete steps. This parameter change enables precise adjustment of the clamping voltage to match specific application requirements, resolving the precision limitation of series diode configurations.
3Reliability
If the clamping module continuously monitors output voltage, then protection is ensured, but power consumption increases
Solution Approach 1:
The patent implements periodic or event-triggered monitoring instead of continuous monitoring. The clamping module activates its voltage monitoring and clamping functions only when needed (e.g., when the power transistor is turned off and inductive current requires freewheeling). During normal operation when protection is not required, the monitoring is reduced or suspended. This periodic action pattern ensures protection coverage when necessary while significantly reducing overall power consumption, resolving the contradiction between reliability and energy use.
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
The solution provides a flexible and efficient freewheeling path for inductive loads, preventing power transistor breakdown and reducing overall power consumption by dynamically adjusting the clamping threshold and reusing the power transistor for precise current discharge.
Implementation Method 1
The current output of the voltage-current converter generates a reference voltage drop on the first resistor
Data Source
AI summary
A load switch circuit includes a power transistor, the first terminal is configured to receive the power supply voltage, and the second terminal is the output terminal of the load switch circuit and is coupled with an external inductive load; a clamping module including at least a mutually coupled clamping unit and a driving unit; the clamping unit, including a voltage-current converter and a first resistor, the first resistor is coupled between the output terminal of the voltage-current converter and the second terminal of the power transistor, the output terminal of the drive unit is coupled to the control terminal of the power transistor when the difference between the power supply voltage and the output voltage of the power transistor is greater than or equal to the preset clamping threshold, and the clamping unit outputs an effective drive control signal to the driving unit.