Capacitor Discharge Control via AC Signal Detection
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Solution Overview
Problem
In power supplies, x-capacitors can remain charged after being removed from an outlet, posing a safety hazard and requiring rapid discharge to comply with international safety standards, while existing solutions like discharge resistors consume power and may not accurately detect AC signal removal.
Innovation Solution
A device that stores peak and valley voltage levels and frequency of an AC signal, periodically checks for changes in these values to determine if the AC signal has been removed, and discharges the capacitor using AC detect and discharge components that minimize standby power consumption and ensure safety within specified timeframes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If discharge resistors are used to discharge the capacitor, then the capacitor can be discharged safely, but standby power consumption increases
Solution Approach 1:
The patent implements periodic detection of the AC signal presence and triggers capacitor discharge only when the AC signal is removed. The controller periodically monitors the voltage across the capacitor and compares it to reference values to determine when discharge is needed, rather than continuously discharging through a resistor. This periodic action eliminates constant power consumption while ensuring safety when required.
Solution Approach 2:
The system uses the existing voltage detection circuitry and controller to monitor capacitor charge status and automatically trigger discharge when needed. The detector utilizes the same sampling circuit that monitors AC input voltage, and the controller self-manages the discharge process by activating the discharge switch based on detected conditions, eliminating the need for separate discharge resistor components.
2Reliability
If discharge resistors are used to discharge the capacitor, then the capacitor can be discharged, but the solution does not accurately detect AC signal removal
Solution Approach 1:
The patent implements a feedback mechanism where the controller continuously monitors the voltage across the capacitor through the detector and adjusts its operation based on the detected voltage levels. The detector samples the capacitor voltage and feeds this information back to the controller, which compares it against reference values to accurately determine when the AC signal has been removed and when discharge should be triggered.
Solution Approach 2:
The patent replaces the passive mechanical discharge resistor approach with an active electronic control system. Instead of relying on a fixed resistor to continuously discharge the capacitor, the system uses electronic voltage detection, digital signal processing, and controlled switching to achieve precise discharge timing based on actual AC signal presence detection.
3Reliability
If the capacitor is discharged rapidly to meet safety standards, then safety compliance is achieved, but complex discharge circuits may be required
Solution Approach 1:
The patent makes the existing voltage detection circuitry serve dual purposes: monitoring AC input voltage during normal operation and detecting capacitor charge status for safety discharge. The same sampling circuit and controller that manage power conversion also handle safety monitoring, eliminating the need for separate dedicated discharge detection circuits and reducing overall system complexity.
Solution Approach 2:
The patent combines the AC voltage detection function with the capacitor discharge detection function into a single integrated system. The detector circuit samples voltage from both the AC input and the capacitor, and the controller processes both signals to determine when discharge is needed, merging multiple safety and monitoring functions into one unified control mechanism.
Data Source
AI summary
An example method includes storing a peak voltage level, a valley voltage level, and a frequency of a signal that corresponds to an alternating current (AC) signal across a capacitor; periodically determining whether a current peak voltage level of the signal is different than the stored peak voltage level of the signal or a current valley voltage level of the signal is different than the stored valley voltage level of the signal; determining, based on whether the current peak voltage level of the signal is different than the stored peak voltage level or the current valley voltage level of the signal is different than the stored valley voltage level, whether the AC signal has been removed from the capacitor; and in response to determining that the AC signal has been removed from the capacitor, discharging the capacitor.