CMOS Backup Power Switching With Dynamic Switchover Thresholds
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Solution Overview
Problem
Existing CMOS power switching circuits face challenges in providing uninterrupted power to load circuits, as they often consume excessive standby power and can unnecessarily drain backup power supplies due to fixed switchover thresholds and continuous operation of backup switch circuits, leading to reduced battery life and inefficient power management.
Innovation Solution
A CMOS power switching circuit that uses a voltage selection circuit to output the highest voltage between primary and backup power supplies, a voltage sensor to set a dynamic switchover threshold based on the backup power supply only when the primary supply is lower, and a power transfer switch controlled by a low-power CMOS design to minimize leakage and standby current, ensuring efficient switching between power sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a power switching circuit uses a fixed switchover threshold and continuous operation of backup switch circuits, then the load circuit can be switched to backup power supply when primary power fails, but the backup power supply is unnecessarily drained and standby power consumption is excessive
Solution Approach 1:
The patent applies dynamics by making the switchover threshold variable rather than fixed. The threshold dynamically adjusts based on the primary power supply voltage: when primary voltage is above a first threshold, the switchover threshold is set to a second threshold; when primary voltage drops below the first threshold, the switchover threshold switches to a third threshold. This dynamic adjustment prevents unnecessary backup power consumption while ensuring reliable switching when truly needed.
Solution Approach 2:
The patent changes the parameter of switchover threshold based on the state of the primary power supply. By monitoring the primary power supply voltage and adjusting the switchover threshold accordingly (using different thresholds based on primary voltage levels), the system optimizes backup power usage while maintaining reliability. This parameter change approach directly addresses the contradiction by adapting the switching behavior to current operating conditions.
2Measurement precision
If the backup power supply is continuously monitored and used as voltage reference, then the switchover can be detected accurately, but the backup power supply voltage drops due to continuous discharge
Solution Approach 1:
The patent applies dynamics by conditionally using the backup power supply as a voltage reference only when needed. The backup power supply serves as voltage reference for setting the switchover threshold only when the primary power supply voltage is below the first threshold. When primary voltage is adequate, the backup power supply is not continuously discharged, preserving its voltage level while still enabling accurate switchover detection when required.
3Duration of action of stationary object
If the switchover threshold is set low to extend backup power life, then backup power is preserved, but the load circuit may not switch to backup power when primary power actually fails
Solution Approach 1:
The patent resolves this contradiction through dynamic threshold adjustment based on primary power voltage levels. When primary voltage is high (above first threshold), a higher switchover threshold (second threshold) is used, enabling timely switching. When primary voltage drops (below first threshold), a lower switchover threshold (third threshold) is used, which extends backup power life while still detecting genuine failures. This dynamic approach ensures both reliability and extended backup duration.
Solution Approach 2:
The patent changes the switchover threshold parameter based on the primary power supply voltage state. By implementing different threshold levels (second threshold when primary voltage is adequate, third threshold when primary voltage is low), the system adapts its detection sensitivity to current conditions, ensuring reliable failure detection while optimizing backup power utilization.
4Reliability
If a voltage selection circuit outputs the highest voltage between primary and backup supplies, then the load circuit receives optimal voltage, but the circuit complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the power supply system into distinct operational modes based on voltage thresholds. The voltage selection circuit operates in segmented stages: when primary voltage exceeds the first threshold, the system operates in primary-power mode; when primary voltage drops below the first threshold, it transitions to backup-power mode. This segmentation simplifies the control logic compared to continuous voltage comparison, reducing circuit complexity while maintaining voltage stability.
Data Source
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AI summary
A Complementary Metal Oxide Semiconductor (CMOS) power switching circuit and a method for operating a CMOS power switching circuit are described. A CMOS power switching circuit includes a voltage selection circuit configured to output the highest output voltage between an output voltage of a primary power supply and an output voltage of a backup power supply and a control circuit configured to connect a load circuit to either the primary power supply or the backup power supply by comparing the output voltage of the primary power supply with a power supply switchover level that is set as a function of the highest output voltage. The backup power supply serves as a voltage reference to set the power supply switchover level only when the output voltage of the primary power supply is lower than the output voltage of the backup power supply.