Current Limit Circuit Using Un-mirrored Bond Wire Voltage
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Solution Overview
Problem
Existing current limit circuits for semiconductor components are costly and prone to inaccuracies due to the use of different silicon substrates for discrete power MOSFETs and integrated circuits, leading to potential over-current conditions that can damage the circuitry.
Innovation Solution
A current limit circuit that generates and compares voltages using un-mirrored currents, employing a comparator and charge pump to control a power MOSFET, allowing for precise current limiting without relying on current mirroring techniques, enabling the use of semiconductor components manufactured using different process flows.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current mirroring techniques are used to control power MOSFET with integrated circuit, then current limiting function is achieved, but manufacturing cost increases and accuracy deteriorates due to substrate mismatches
Solution Approach 1:
The patent extracts the current sensing function from the integrated circuit and places it directly at the power MOSFET substrate. By taking out the current mirror requirement and using direct voltage comparison across the MOSFET, the design eliminates the need for matching transistors between different substrates, thereby improving accuracy without increasing complexity
Solution Approach 2:
The patent introduces an intermediary voltage comparison mechanism that directly measures the voltage drop across the power MOSFET source-drain terminals. This intermediary measurement approach bypasses the need for current mirroring through separate transistors, achieving accurate current limiting while reducing the number of components required
2Ease of manufacture
If discrete power MOSFET and integrated circuit are manufactured on separate silicon substrates, then各自 manufacturing process requirements are met, but current matching accuracy deteriorates
Solution Approach 1:
The patent segments the current limiting function into two independent parts: the power MOSFET on its substrate and the control circuitry on the integrated circuit substrate. By using direct voltage comparison rather than current mirroring, each substrate can be manufactured independently with their own process requirements while maintaining system accuracy
Solution Approach 2:
The patent uses voltage as an intermediary parameter to bridge the two separate substrates. Instead of requiring direct current matching between substrates, the voltage drop across the MOSFET is measured and compared, allowing independent manufacturing while maintaining precision through the intermediary voltage measurement
3Reliability
If complex current mirror circuit with multiple transistors and resistors is used, then current limiting control is achieved, but circuit cost increases
Solution Approach 1:
The patent extracts only the essential current sensing function from the complex current mirror circuit. By taking out just the voltage measurement capability and eliminating the need for matching transistors and multiple resistors, the design achieves over-current protection with fewer components
Solution Approach 2:
The power MOSFET itself provides the current sensing function through its inherent source-drain voltage drop. The circuit uses this self-generated voltage signal for comparison and control, eliminating the need for external sensing resistors or complex mirror circuits, thereby reducing component count while maintaining protection reliability
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 provides precise current limiting, reducing the risk of catastrophic device failure and allowing for the efficient manufacture of multi-chip components with diverse semiconductor process flows, thereby lowering costs and improving performance.
Implementation Method 1
operating a charge pump in response to the un-mirrored current level
Data Source
AI summary
A current limit circuit and a method for limiting current flow. The current limit circuit includes a transistor having a control electrode and current carrying electrodes. A wire is coupled to one of the current carrying electrodes. An output of a comparator is coupled to the control electrode of the transistor through a charge pump. One input of the comparator is coupled to the current carrying electrode of the transistor that is coupled to the wire and the other input of the comparator is coupled for receiving a voltage. Preferably the wire is a bond wire. The current flowing through the wire sets the input voltage appearing at the input of the comparator coupled to the current carrying electrode of the transistor. In response to the comparison of the voltages at the input of the comparator, the transistor remains turned-on or it is turned-off.