DC/DC Converter Overcurrent Protection Using Multi-Functional Pins
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Solution Overview
Problem
Existing DC/DC converters require additional pins for overcurrent protection, leading to increased IC package size and cost, and are prone to noise-induced errors due to signal routing issues and limited voltage range compatibility.
Innovation Solution
A DC/DC converter system that senses current through a MOSFET switch using a bipolar transistor and sense resistor, disabling the pulse-width modulated output when the current exceeds threshold levels, eliminating the need for dedicated pins and enhancing noise immunity by generating the overcurrent signal at the source.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dedicated pins are added for overcurrent protection sensing, then overcurrent protection capability is improved, but IC package size and cost increase
Solution Approach 1:
The patent makes existing converter pins multi-functional by using them for both normal converter operation and overcurrent protection sensing. The control circuit selectively uses these pins for current sensing during specific operation phases, eliminating the need for dedicated sensing pins while maintaining protection capability
Solution Approach 2:
The patent combines the overcurrent protection sensing function with the existing converter pin structure. The sensing function is merged into the control circuit that already manages the converter pins, allowing dual functionality without adding separate dedicated pins
2Reliability
If dedicated pins are added for overcurrent protection sensing, then overcurrent protection capability is improved, but package cost and PCB area increase
Solution Approach 1:
The patent makes existing converter pins multi-functional by using them for both normal converter operation and overcurrent protection sensing. The control circuit selectively uses these pins for current sensing during specific operation phases, eliminating the need for dedicated sensing pins while maintaining protection capability
Solution Approach 2:
The patent combines the overcurrent protection sensing function with the existing converter pin structure. The sensing function is merged into the control circuit that already manages the converter pins, allowing dual functionality without adding separate dedicated pins
3Area of stationary object
If single-ended sensing is used to reduce pins, then pin count is reduced, but signal integrity deteriorates due to ground differences
Solution Approach 1:
The patent introduces a controlled switching mechanism as an intermediary between the sensing pin and the comparator. The switch is controlled to connect the sensing pin to the appropriate reference potential at the correct time, eliminating ground potential differences that would cause offset errors while maintaining single-ended sensing benefits
Solution Approach 2:
The patent applies blanking circuitry that temporarily disables the comparator during critical switching transitions before the sensing is needed. This preliminary action prevents noise and ground shifts during MOSFET turn-on from causing false trips, ensuring signal integrity when sensing is activated
4Reliability
If blanking circuit is added to prevent false trips, then false trips due to noise are reduced, but overcurrent detection response time is delayed
Solution Approach 1:
The patent uses periodic switching of the sensing connection controlled by the converter's switching cycle. The sensing pin is connected to the comparator input only during specific phases of the switching cycle when current sensing is valid, naturally preventing false trips during transitions without requiring continuous blanking
Solution Approach 2:
The patent dynamically controls the connection between the sensing pin and comparator input based on the switching state. The switch connects the sensing pin during MOSFET off-state when current is stable and disconnects during transitions, adapting the sensing configuration to the real-time operating conditions to prevent false trips while maintaining rapid detection
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
This solution reduces IC package size and cost, improves noise immunity, and allows operation over an arbitrary voltage range without premature or missed overcurrent trips, addressing the limitations of prior art.
Implementation Method 1
A DC/DC converter of a type that provides a pulse width modulated signal output to a gate of a MOSFET switch... a control configured so as to sense a current generated at the output when the current through the MOSFET switch exceeds a first threshold level
Data Source
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AI summary
A DC/DC converter and a method protect a MOSFET driven by the converter from overcurrent conditions. No extra pins are required to sense the current, which saves IC package area and cost.