Power Supply Selector Circuit for Low-Drop Multi-Source Switching
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Solution Overview
Problem
Existing power supply selection circuits face challenges in accurately selecting a power supply with minimal voltage drop and low power consumption, particularly in low-voltage systems, and require complex circuits like charge pumps and clock circuits to prevent current flow between power supplies.
Innovation Solution
A power supply selector comprising a first selection module, a control module, and a second selection module that compares voltages to generate control signals, allowing for accurate selection of the highest or lowest voltage power supply without voltage drop issues, using PMOS transistors and a drive module to improve driving capability, and eliminating the need for charge pumps and clock circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If diode structure is used for power supply selection, then current flow between power supplies is prevented, but voltage drop of 0.5-0.6V occurs which is unfavorable for low-voltage systems
Solution Approach 1:
The patent changes the operating parameters of the transistor by dynamically adjusting its threshold voltage through a control circuit. By modifying the threshold voltage parameter, the transistor can operate in different modes to achieve both low voltage drop and current flow prevention, resolving the contradiction between reliability and energy loss.
Solution Approach 2:
The patent transforms the static diode structure into a dynamic transistor-based switch that can adapt its characteristics based on operating conditions. The transistor's gate voltage is dynamically controlled to adjust the conduction state, enabling the system to maintain low voltage drop while preventing current flow between power supplies through active control.
2Loss of energy
If Schottky diodes are used to reduce voltage drop, then voltage drop decreases to 0.2-0.3V, but the structure complexity increases
Solution Approach 1:
The patent uses standard CMOS transistors that are already present in the process to create the power supply selection function, rather than introducing specialized Schottky diodes. This copying approach leverages existing device structures to achieve the desired functionality with lower voltage drop and reduced complexity.
Solution Approach 2:
The patent makes the transistor serve multiple functions: power supply selection, voltage level adaptation, and current flow control. By designing the transistor to perform these multiple functions, the patent eliminates the need for separate Schottky diodes and other additional components, reducing overall structure complexity while maintaining low voltage drop performance.
3Reliability
If charge pump and clock circuit are added to prevent current flow, then current flow between power supplies is prevented, but circuit complexity and power consumption increase
Solution Approach 1:
The patent extracts and removes the charge pump and clock circuit from the system by implementing current flow prevention directly through the transistor's gate control. This extraction eliminates the need for these additional complex components while maintaining the reliability of current flow prevention through the simpler transistor-based approach.
Solution Approach 2:
The transistor's gate control circuit automatically manages the power supply selection and current flow prevention without requiring external charge pumps or clock signals. The control circuit uses the existing power supply voltages to self-regulate the transistor states, enabling the system to prevent current flow between power supplies using its own internal resources rather than additional external components.
4Power
If threshold voltage is lost in NMOS switch, then voltage transmission accuracy decreases, but overdrive voltage can be increased to reduce on-resistance
Solution Approach 1:
The patent dynamically changes the transistor's threshold voltage parameter through gate control to optimize both power transmission and voltage accuracy. By adjusting the threshold voltage, the system can reduce on-resistance for better power transmission while maintaining sufficient voltage transmission accuracy through controlled operation modes.
Solution Approach 2:
The patent implements a control circuit that monitors the power supply voltages and provides feedback to adjust the transistor gate voltages accordingly. This feedback mechanism ensures that the transistor operates in the optimal region to minimize both voltage transmission error and on-resistance, resolving the contradiction between power and measurement precision.
Data Source
AI summary
In the field of electronic technologies, a power supply selector and a power supply selection method are provided. The power supply selector includes: a first selection module, configured to select a power supply from multiple candidate power supplies; a control module, coupled to the first selection module, and configured to use the power supply selected by the first selection module as a power supply, and compare voltages of the multiple candidate power supplies to generate a control signal of each candidate power supply; and a second selection module, coupled to the control module, and configured to select a power supply for output in the multiple candidate power supplies under the control of the control signal of each candidate power supply. The technical solution is used to select a power supply from multiple candidate power supplies.