Over-voltage Clamp Circuit Using Current Sensing
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Solution Overview
Problem
Conventional over-voltage protection methods for power delivery circuits often result in undesired power interruptions due to direct voltage sensing and control, which complicates the implementation of accurate and fast output voltage clamping.
Innovation Solution
A clamp circuit that senses output current to track and regulate output voltage, eliminating direct voltage sensing and incorporating a mirror transistor and divider circuit to generate a feedback signal for clamping, along with a gate control circuit to manage the output voltage based on a set clamping threshold, enhancing speed and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If direct voltage sensing and control is used for over-voltage protection, then protection function is achieved, but power interruptions occur and clamping accuracy deteriorates
Solution Approach 1:
The patent introduces an intermediary approach by using current sensing instead of direct voltage sensing. The current sensor detects output current changes that indicate over-voltage conditions, and the gate control circuit processes this information to generate appropriate control signals. This intermediary current-based detection method avoids the direct voltage sensing problems while maintaining protection functionality and power continuity.
Solution Approach 2:
The patent replaces the conventional voltage sensing mechanism with a current sensing mechanism. Instead of directly measuring voltage and controlling the switch based on voltage thresholds (which causes power interruptions), the system senses current through a current sensor and uses gate control to regulate the switch. This substitution eliminates the harmful voltage sensing feedback while achieving both protection and continuous power delivery.
2Ease of operation
If output voltage clamping is implemented, then power continuity is maintained, but circuit complexity increases
Solution Approach 1:
The gate control circuit performs multiple functions: it controls the output power switch during normal operation and simultaneously acts as a clamp control during over-voltage conditions. The current sensor serves dual purposes of monitoring load current and detecting over-voltage conditions through current changes. This multi-functionality reduces the need for separate clamping circuitry, thereby reducing overall circuit complexity while maintaining power continuity.
Solution Approach 2:
The patent merges the over-voltage protection function with the existing power switch control circuitry. The gate control circuit that normally controls the power switch is enhanced to also perform clamping functions by detecting over-voltage conditions through current sensing and adjusting the switch control accordingly. This integration eliminates the need for separate protection circuits, reducing complexity while maintaining continuous power delivery.
3Speed
If fast response clamping is achieved, then power continuity is maintained, but clamping accuracy deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where the current sensor continuously monitors output current and feeds this information to the gate control circuit. The gate control circuit adjusts the power switch control based on this feedback to maintain accurate clamping. This closed-loop feedback ensures both fast response (through immediate current-based detection) and high accuracy (through continuous adjustment based on sensed current conditions).
Data Source
AI summary
An apparatus includes an output transistor device configured to control an output voltage of an output node in response to a control signal and an input voltage. A current sensor is configured to sense an output current supplied from the output node. A feedback converter is configured to convert the sensed output current to a feedback signal that tracks the output voltage of the output node. The feedback converter is further configured to set a clamping threshold. A gate control circuit is configured to generate the control signal in response to the feedback signal. The gate control circuit is configured to clamp the output voltage of the output node via the control signal based on the clamping threshold.