AC Input Filter Capacitor Discharge Circuit for Safety Compliance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing power supply systems, particularly switching mode power supplies, face challenges in efficiently discharging X capacitors to meet safety guidelines like IEC 60950, with previous methods being either ineffective or costly.
Innovation Solution
A converter with an integrated discharge circuit that detects AC line voltage transitions, uses a timer to reset, and employs a constant current source or silicon controlled rectifier to discharge input filter capacitors to a lower threshold, transferring charge to a supply capacitor when the AC line is disconnected.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional discharge methods are used for X capacitors, then power consumption is reduced, but discharge requirements per IEC 60950 safety guidelines are not met
Solution Approach 1:
The discharge circuit utilizes the existing AC line voltage transitions and system startup circuitry to automatically discharge the X capacitor when the AC line is disconnected. The circuit detects the absence of AC voltage and activates the discharge path without requiring external control signals or additional power consumption, thereby meeting safety discharge requirements while maintaining low power operation.
Solution Approach 2:
The patent introduces a discharge circuit with a switch element (such as an SCR or transistor) that acts as an intermediary to create a controlled discharge path for the X capacitor. This intermediary component enables the capacitor to discharge through a dedicated low-impedance path when needed, while remaining high-impedance during normal operation to minimize power consumption.
2Reliability
If existing discharge circuits are implemented, then X capacitor discharge is achieved, but implementation cost increases
Solution Approach 1:
The discharge circuit is integrated with the existing startup circuitry and AC voltage detection mechanisms in the power supply system. By merging the discharge function with existing components such as the AC detector, timer, and startup capacitor circuitry, the patent eliminates the need for separate dedicated discharge control circuits, thereby reducing component count and implementation cost while maintaining effective capacitor discharge capability.
Solution Approach 2:
The discharge circuit is designed to serve multiple functions: it detects AC line presence, controls the discharge timing, and provides the discharge path itself. The same circuit elements that monitor AC voltage for startup purposes are also utilized to trigger and control the X capacitor discharge process, making the system multi-functional and cost-effective.
3Reliability
If discharge circuit is added to meet safety guidelines, then discharge time is reduced, but system complexity increases
Solution Approach 1:
The discharge circuit is pre-configured with a low-impedance discharge path that remains dormant during normal AC-powered operation. When the AC line is disconnected, the circuit automatically activates this pre-prepared discharge path, enabling rapid capacitor discharge without requiring complex real-time control algorithms or multiple switching stages. The discharge path is prepared in advance and simply activated when needed.
Solution Approach 2:
The patent extracts the essential discharge function from complex control circuits and implements it through a simple, dedicated discharge path with a single switch element. By separating the discharge function from the main power conversion and control circuitry, the design achieves fast discharge capability with minimal additional complexity, using only a few discrete components added to the existing system.
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 efficiently discharges X capacitors within a short time frame, ensuring compliance with safety guidelines while being cost and time efficient, and does not interfere with system restart times.
Implementation Method 1
A converter with an integrated discharge circuit that detects AC line voltage transitions
Implementation Method 2
employs a constant current source or silicon controlled rectifier to discharge input filter capacitors
Implementation Method 3
uses a timer to reset
Data Source
Figure 1~4
Figure 2
Figure 3
AI summary
In accordance with an embodiment, a power supply (10) may include a filter stage (32,20,34) coupled to an input terminal (80A) of a discharge circuit (80) and a supply capacitor (52) coupled to an output terminal (80B) of the discharge circuit (80). In accordance with another embodiment, a method for discharging at least one capacitor includes discharging the at least one capacitor in response to a signal at the input terminal of the discharge circuit being different from a reference signal.