Multi-Input LDO Regulator With Cascode Switching for Heat Control
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Solution Overview
Problem
Conventional low-dropout (LDO) regulators with multiple voltage supply inputs face inefficiencies in power dissipation, leading to higher temperature at the pass transistor during short circuits and require separate error amplifiers and current limiters for each input, increasing cost and design complexity.
Innovation Solution
A voltage regulation circuit with switching circuitry that includes a cascode arrangement between a high voltage-rated cascode transistor and a lower-rated pass transistor, distributing power dissipation and using a single error amplifier and current limiter for multiple inputs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional LDO regulators with multiple voltage supply inputs are used, then each input requires separate error amplifiers and current limiters, but this increases device complexity and cost
Solution Approach 1:
The patent merges multiple input control functions into a single error amplifier and current limiter by using switching circuitry that selectively connects different voltage supply inputs to the pass transistor. This allows one error amplifier and one current limiter to serve multiple voltage inputs, reducing device complexity while maintaining adaptability.
Solution Approach 2:
The error amplifier and current limiter are designed to be universal components that can handle multiple voltage supply inputs through the switching mechanism. The switching circuitry enables these components to function with different input voltages without requiring separate dedicated circuits for each input.
2Adaptability or versatility
If conventional LDO regulators with multiple voltage supply inputs are used, then each input requires separate error amplifiers and current limiters, but this increases device size and cost
Solution Approach 1:
The patent combines multiple input handling capabilities into a single physical device structure by using switching circuitry. This allows one error amplifier, one current limiter, and one pass transistor to serve multiple voltage supply inputs, significantly reducing the overall device size compared to having separate circuits for each input.
Solution Approach 2:
The universal design of the error amplifier and current limiter, enabled by the switching mechanism, allows these components to handle multiple voltage inputs within a single compact device footprint, reducing the total device size while maintaining support for multiple voltage supply inputs.
3Productivity
If conventional LDO regulators are used without cascode arrangement, then the pass transistor dissipates all power during short circuits, but this causes higher temperature at the pass transistor
Solution Approach 1:
The patent segments the power dissipation function by introducing a cascode transistor in series with the pass transistor. During short circuit conditions, the cascode transistor dissipates a portion of the power, thereby reducing the temperature burden on the pass transistor while maintaining the overall power dissipation capability of the regulator.
Solution Approach 2:
The cascode transistor acts as an intermediary element between the voltage supply input and the pass transistor. It mediates the power dissipation during short circuits by absorbing excess voltage and current, protecting the pass transistor from overheating while enabling the system to handle high power dissipation requirements.
Data Source
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AI summary
A voltage regulator is described that includes an error amplifier configured to provide an error signal based on a comparison of a reference voltage and a voltage at a voltage divider coupled to an output node of the voltage regulation circuit, a pass transistor configured to selectively pass current from an input node to the output node based on the error signal, and switching circuitry configured to selectively couple one of a first voltage supply input and a second voltage supply input to the input node. The switching circuitry includes a first leg that includes a first switch and a transistor that is coupled in a cascode arrangement with the pass transistor and a second leg that includes a second switch.