Dual-Input LDO Voltage Regulator Circuit for Low Dropout Efficiency
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Solution Overview
Problem
Existing voltage regulation solutions face challenges in achieving high efficiency, handling extended input voltage ranges (9-18 V), managing low dropout voltages, and maintaining small area requirements, especially in applications like hard disk drives.
Innovation Solution
A dual-input single-output voltage regulator with 'zero' dropout and automatic input selection, utilizing a dual-input Low DropOut (LDO) arrangement that switches to an internally generated power supply when the external power supply becomes too low, ensuring efficient operation and minimal current flow from the external to the internal power supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a conventional voltage regulator is used, then the circuit is simple, but the dropout voltage is high and system efficiency decreases
Solution Approach 1:
The voltage regulator is divided into two separate input circuits (first input circuit and second input circuit) that can be independently controlled. Each input circuit has its own pass transistor and control logic, allowing the system to segment the power supply paths and select the optimal input source based on voltage levels, thereby improving efficiency without excessive complexity
Solution Approach 2:
The regulator dynamically switches between two input voltage sources (VM and VP) based on real-time voltage level detection. The control circuit continuously monitors input voltages and automatically transitions between inputs, making the system adaptive and efficient across varying operating conditions while maintaining manageable complexity through automated control
2Use of energy by moving object
If a dual-input LDO arrangement is used, then system efficiency increases, but device complexity increases
Solution Approach 1:
The control circuit performs preliminary detection of input voltage levels before switching occurs. By anticipating the need for input switching and preparing control signals in advance, the system efficiently transitions between inputs without instability or excessive complexity in the switching mechanism
Solution Approach 2:
The regulator incorporates feedback mechanisms where the output of each input circuit feeds back to the control logic, enabling automatic selection and switching between inputs. This feedback-driven approach maintains system efficiency through optimal input selection while keeping the control architecture systematic and manageable
3Reliability
If the power supply voltage becomes too low, then voltage regulation fails, but switching to internal power supply increases current flow
Solution Approach 1:
A control circuit acts as an intermediary between the two input circuits and the output. This intermediary selectively activates either the first or second input circuit based on voltage conditions, preventing direct current flow from VM to VP and ensuring that switching occurs only when necessary for maintaining reliable voltage regulation
Solution Approach 2:
Each input circuit is designed with localized control characteristics - the first input circuit handles normal voltage conditions while the second handles low-voltage conditions. This local optimization allows each circuit to be tuned for its specific operating range, maintaining regulation reliability without unnecessary current flow between power supplies
4Adaptability or versatility
If extended input voltage range is supported, then adaptability increases, but maintaining low dropout voltage becomes difficult
Solution Approach 1:
The regulator dynamically adapts its operating mode based on input voltage level. By continuously monitoring the input voltage and switching between two different input circuits optimized for different voltage ranges, the system maintains adaptability across extended voltage ranges while preserving low dropout performance in each operating mode
Solution Approach 2:
The system changes operational parameters by switching between two distinct input circuits with different characteristics. Each circuit is optimized for specific voltage ranges, allowing the overall system to handle extended input voltage ranges while maintaining low dropout voltage through parameter optimization in each operating region
Data Source
AI summary
A dual-input, single-output low-dropout voltage regulator circuit includes: a first supply terminal, a second supply terminal and an output terminal, and first and second transistors having current paths coupled respectively between the first and second terminal and the output terminal. First and second drive circuit blocks are coupled respectively to the first and second supply terminals and drive the control terminals of the first and second transistors to provide a regulated voltage at the output terminal from the voltage on the first supply terminal and the second supply terminal. An input circuit block is sensitive to the voltage at the output terminal and is coupled to the first and second drive circuit blocks and configured to activate the second transistor to provide regulated voltage at the output terminal from the second terminal as a result of the voltage at the output terminal becoming lower than a desired value.