Power Supply Device with Capacitor Backup for CMOS Data Retention
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Solution Overview
Problem
Current power supply devices fail to maintain data in the CMOS storage area of a system chip when a coin battery is replaced, leading to data loss due to the lack of power during the replacement process.
Innovation Solution
A power supply device comprising a first battery, a capacitor, and a monitoring circuit that detects battery and capacitor voltages, providing backup power through the capacitor when the battery voltage is low, ensuring data integrity during battery replacement by switching to the capacitor voltage as maintenance voltage when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a monitoring circuit is used to detect battery voltage and remind users to replace the coin battery, then the user is notified before complete power loss, but the data is still lost during the battery replacement process because no backup power is provided
Solution Approach 1:
The capacitor is pre-charged to a voltage higher than the second threshold during system operation before battery replacement is needed. When the coin battery is removed, this pre-charged capacitor immediately provides backup power to maintain CMOS data, eliminating the data loss problem that occurs with mere monitoring alerts.
Solution Approach 2:
The capacitor serves as a cushioning energy storage device that is charged in advance during normal operation. When the coin battery voltage drops below the first threshold, the monitoring circuit triggers capacitor charging, creating an energy buffer that cushions against data loss during the subsequent battery replacement period.
2Reliability
If the capacitor is continuously charged during system operation, then backup power is always available, but energy is wasted when the coin battery still has sufficient power
Solution Approach 1:
The monitoring circuit continuously monitors the coin battery voltage and uses this feedback to control the charging circuit. When the battery voltage is above the first threshold, the charging circuit remains off, preventing energy waste. When the voltage drops below the threshold, the charging circuit activates to charge the capacitor, ensuring backup power availability only when needed.
Solution Approach 2:
Instead of continuous charging, the system applies partial charging action only when necessary (when battery voltage < first threshold). The capacitor is charged to a voltage higher than the second threshold, which is excessive compared to minimum requirements, ensuring sufficient backup power duration for battery replacement while avoiding continuous energy consumption.
3Measurement precision
If the capacitor voltage is set to match the battery voltage threshold, then the switching point is clear, but the capacitor may not provide sufficient backup power duration for complete battery replacement
Solution Approach 1:
The capacitor is charged to a voltage higher than the second threshold (e.g., 3.3V or 3.6V) rather than exactly at the second threshold (e.g., 2.8V). This excessive charging ensures that the capacitor can provide backup power for the complete battery replacement process, including user notification and physical replacement time, while the monitoring circuit maintains precise threshold detection for triggering the charging action.
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 solution effectively maintains data in the CMOS storage area by providing a stable voltage during battery replacement, preventing data loss and ensuring system parameters are retained.
Implementation Method 1
The capacitor stores a capacitor voltage
Implementation Method 2
The charging circuit is coupled to the capacitor. The monitoring circuit detects whether the battery voltage is less than a first threshold and whether the capacitor voltage is larger than a second threshold and generates a control signal according to the determination result
Data Source
AI summary
A power supply device is provided. The power supply device provides a maintenance voltage at an output terminal to a system chip of a system and includes a first battery, a capacitor, a charging circuit, and a monitoring circuit. The first battery provides a battery voltage. The capacitor stores a capacitor voltage. The charging circuit is coupled to the capacitor. The monitoring circuit detects whether the battery voltage is less than a first threshold and whether the capacitor voltage is larger than a second threshold and generates a control signal according to the determination result. When the monitoring circuit detects that the battery voltage is less than the first threshold and the capacitor voltage is not larger than the second threshold, the monitoring circuit asserts the control signal to control the charging circuit to charge the capacitor.