Switch Transistor Power Limiting with Voltage-Based Current Control
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Solution Overview
Problem
Conventional power-limiting technologies for switch transistors in Power over Ethernet (PoE) systems lack an accurate control mechanism, leading to increased on-resistance (Ron) and inability to lower power when current is too large, making it difficult to maintain operation current within predetermined limits.
Innovation Solution
A power supply apparatus and method incorporating a switch transistor, voltage detection circuit, power-limiting circuit, and current-limiting circuit, which uses analog-to-digital and digital-to-analog conversion to generate a current-limiting signal based on a predetermined voltage-current curve, controlling the switch transistor to maintain operation current within set limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional power-limiting technologies are used to limit the power of the switch transistor, then the operation power is reduced, but the control precision is insufficient and the operation current cannot be accurately maintained
Solution Approach 1:
The patent implements a feedback control mechanism where the operation current of the switch transistor is continuously monitored and compared against the target current value derived from the voltage-current curve. The control circuit adjusts the gate voltage of the switch transistor based on the current deviation, forming a closed-loop feedback system that precisely maintains the operation current at the desired level while limiting power consumption.
Solution Approach 2:
The patent replaces conventional analog power-limiting mechanisms with a digital control system. The operation voltage is converted to digital form, processed through calculation circuits that implement the voltage-current curve logic, and then converted back to analog control signals. This digital substitution enables more precise calculation and control of the operation current compared to traditional analog approaches.
2Power
If the conduction degree of the switch transistor is lowered to reduce current, then the operation current is reduced, but the on-resistance increases and power cannot be effectively lowered
Solution Approach 1:
The patent dynamically adjusts the conduction state of the switch transistor based on real-time operation voltage measurements and the predetermined voltage-current curve. Rather than using a fixed conduction degree, the control circuit continuously modifies the gate voltage to maintain the optimal balance between current limitation and on-resistance management, adapting to changing operating conditions to effectively limit power while minimizing resistance increases.
3Ease of operation
If a single network connection is used for Power over Ethernet, then the connection simplicity is improved, but the power control precision deteriorates
Solution Approach 1:
The patent segments the power control function into distinct modular components: voltage detection circuit, analog-to-digital conversion circuit, calculation circuit for generating current-limiting signals, digital-to-analog conversion circuit, and current-limiting circuit. This segmentation allows each component to perform its specific function with high precision while maintaining the overall simplicity of the single network connection interface.
Data Source
AI summary
The present invention discloses a power supply apparatus having power limiting mechanism. A switch transistor is controlled by a control voltage such that a power supply unit supplies a power to a powered device when the switch transistor is controlled to be conducted, wherein the switch transistor has an operation current, an operation voltage and an operation power under conduction. A voltage detection circuit detects the operation voltage. A power-limiting circuit performs analog-to-digital conversion on the operation voltage, generates a current-limiting signal related to a current-limiting value according to the operation voltage based on a predetermined voltage-current curve and performs digital-to-analog conversion on the current-limiting signal to generate a reference voltage. A current-limiting circuit receives the reference voltage and a feedback voltage generated according to the operation current to perform comparison and generate the control voltage accordingly to control the switch transistor to keep the operation current at the current-limiting value.