Fast Switching Current Mirror Circuit for Large MOSFETs
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Solution Overview
Problem
Existing current mirror circuits in switch-mode regulators are inefficient due to high space and power consumption, and slow switching speeds, making them unsuitable for modern miniaturized electronic devices that require fast switching and low power consumption.
Innovation Solution
A fast switching current mirror circuit is designed with a large output transistor, a current source, a first current mirror for biasing, a feedback sub-circuit, and a second current mirror for residual current sinking, along with complementary clock switches to control the gate voltages of the output transistor, optimizing current mirroring and switching efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a large size sink transistor is used to pull down the gate of the output transistor quickly, then the switching speed is improved, but the space consumption and power consumption increase significantly
Solution Approach 1:
The patent divides the single large sink transistor into multiple smaller sink transistors (first sink transistor and second sink transistor). This segmentation allows the circuit to achieve the required total sink current capability while using smaller individual transistors that occupy less total area and consume less power.
Solution Approach 2:
The patent combines multiple sink transistors to work together in parallel, achieving the aggregate sink current capability of a single large transistor while avoiding the space and power penalties. The multiple transistors are merged functionally to provide the necessary gate discharge current.
2Speed
If a large size sink transistor is used to pull down the gate of the output transistor quickly, then the switching speed is improved, but the power consumption increases
Solution Approach 1:
The patent segments the sink function across multiple smaller transistors, each consuming less power individually. The combined power consumption of multiple smaller transistors is less than that of a single large transistor providing the same total current.
Solution Approach 2:
The patent uses multiple copies of smaller sink transistor circuits instead of one large sink transistor. Each copy provides a portion of the required sink current, and the cumulative effect achieves the desired switching speed with reduced power consumption.
3Use of energy by stationary object
If a buffer amplifier is added to limit the discharge current, then the power consumption is reduced, but the space consumption increases
Solution Approach 1:
The patent replaces the buffer amplifier with segmented sink transistors that inherently limit current through their smaller sizes. This segmentation approach achieves current limiting functionality without requiring the additional space of a buffer amplifier stage.
Solution Approach 2:
The patent extracts the current limiting function from the buffer amplifier and implements it directly through the sizing and configuration of the sink transistors. This removes the need for the buffer amplifier component entirely, saving space while maintaining power efficiency.
4Use of energy by stationary object
If the sink current is reduced to save power and space, then the space and power consumption are reduced, but the switching speed becomes slow
Solution Approach 1:
The patent segments the sink current capability across multiple transistors that activate in coordination. During switching transitions, the combined sink current is sufficiently large to achieve fast switching, while during steady state, the effective current consumption is reduced.
Solution Approach 2:
The patent creates a dynamic sink current capability where the effective sink strength varies with operating conditions. The circuit provides high sink current during switching events for fast speed, and lower effective current consumption during steady state for power efficiency.
Data Source
AI summary
The present invention discloses a fast switching current mirror circuit and method for generating fast switching current. The circuit and method for fast switching of a current mirror with large MOSFET size will save space and current consumption.