Programmable-Threshold Power Supply Selector Circuit
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Solution Overview
Problem
Existing power supply selector circuits often switch unnecessarily between main and backup power supplies when voltages are close or fluctuating, leading to instability and potential damage due to feed-through current, and lack the ability to set a programmable voltage threshold for switching decisions.
Innovation Solution
A programmable-threshold power supply selector circuit that uses an open-loop decision circuit to compare the main power supply voltage to a programmable threshold voltage, allowing the main power supply to be used until the voltage falls below the threshold, at which point the backup supply is switched to, thereby reducing unnecessary switching and instability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a power supply selector switches between main and backup power supplies based on voltage comparison, then the system can maintain power supply stability, but unnecessary frequent switching occurs when voltages are near one another causing instability and feed-through current
Solution Approach 1:
The patent introduces a programmable threshold voltage parameter that changes the switching decision criterion from simple voltage comparison to threshold-based comparison. This parameter modification prevents unnecessary switching by establishing a clear voltage threshold boundary, thereby resolving the contradiction between maintaining power supply stability and avoiding frequent switching instability.
Solution Approach 2:
The patent introduces an open-loop decision circuit as an intermediary component that mediates the switching decision between main and backup power supplies. This decision circuit evaluates the voltage against a programmable threshold and controls the switching transistors accordingly, preventing direct comparison-based switching that causes instability when voltages are相近.
2Device complexity
If a simple voltage comparison method is used to select power supply, then the circuit complexity is reduced, but the ability to control switching decision and prevent unnecessary switching is lost
Solution Approach 1:
The patent adds a programmable threshold voltage parameter to the simple voltage comparison method. This parameter enhancement maintains relative circuit simplicity while significantly improving switching control capability, allowing the system to distinguish between normal voltage fluctuations and actual power supply failures.
3Speed
If the power supply selector monitors voltage closely to detect failures, then the response time to power supply failure is reduced, but unnecessary switching occurs due to voltage fluctuations
Solution Approach 1:
The patent modifies the detection parameter from direct voltage comparison to threshold-based voltage comparison. This parameter change maintains fast failure detection capability while filtering out noise from normal voltage fluctuations, thereby improving switching reliability.
4Stability of the object's composition
If a programmable threshold voltage is introduced for switching decisions, then unnecessary switching is reduced, but the device complexity increases
Solution Approach 1:
The patent implements a programmable threshold voltage parameter that can be configured through software or hardware settings. This parameter-based approach achieves switching stability without requiring complex control logic, as the threshold value itself encodes the switching decision criteria.
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
The programmable-threshold power supply selector reduces unnecessary switching and instability by allowing the main power supply to be used until its voltage falls below a programmable threshold, minimizing feed-through current and ensuring stable operation.
Implementation Method 1
Comparator 12 compares these power supply voltages and drives the gates of switch transistors 14, 16 with switch control voltages VSW1, VSW2
Implementation Method 2
Switch transistors 14, 16 select either VDD1 or VDD2 to drive the output supply voltage VDO to power the system
Data Source
AI summary
A programmable-threshold power supply selector has two power-supply inputs VDD1 and VDD2. The higher of these two voltages is pre-selected as a common supply that powers all transistors and circuitry in the programmable-threshold power supply selector, including substrates under transistors. An open-loop decision circuit is very stable since it uses no feedback. A tunable voltage divider divides VDD1 by a programmable divisor. The divided VDD1 is compared to a reference voltage to generate switch-control signals. The switch-control signals drive the gates of p-channel switch transistors that connect either VDD1 or VDD2 to an output supply voltage. The different programmable divisor values effectively cause VDD1 to be compared to a programmable threshold voltage VTH. The switch transistors switch the output supply voltage to VDD2 only when VDD1 falls below VTH. The output supply voltage remains at VDD1 even when VDD1 falls below VDD2, eliminating unnecessary power switching.