X Capacitor Discharge Circuit for Switching Converters
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Solution Overview
Problem
Existing EMI filter circuits for switching converters do not efficiently and safely discharge the X capacitor after disconnection from a power source, posing safety risks due to residual voltage.
Innovation Solution
A discharge circuit and method that includes a first voltage detection circuit to indicate disconnection from an AC power source, triggering a discharge module to safely discharge the X capacitor during a predetermined time period and verifying the power source type through voltage sampling and comparison.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the switching converter is disconnected from power source, then safety risk increases due to residual voltage on X capacitor, but continuous discharging increases power loss
Solution Approach 1:
The patent applies preliminary action by detecting power source disconnection in advance and initiating the discharging operation before the voltage becomes dangerously high. The voltage detection circuit monitors the input terminals and triggers the discharge switch to activate the discharging path proactively, preventing safety hazards before they occur while avoiding continuous discharging that would waste energy.
Solution Approach 2:
The patent implements periodic action through intermittent discharging controlled by timing signals. Instead of continuous discharging, the system periodically activates the discharge switch for predetermined time intervals, allowing the X capacitor to discharge in cycles. This approach maintains safety by periodically reducing voltage while minimizing power loss by keeping the discharge path inactive during normal operation.
2Reliability
If voltage detection is implemented to determine power source connection status, then discharging control improves, but device complexity increases
Solution Approach 1:
The patent applies universality by designing the voltage detection circuit to serve multiple functions: it detects both AC and DC power source connections, determines when discharging should be activated, and provides control signals for the discharge switch. This multi-functional approach improves discharging control reliability while avoiding the need for separate dedicated circuits for each function, thereby limiting the increase in device complexity.
Solution Approach 2:
The patent uses an intermediary approach by introducing a voltage detection circuit that acts as a mediator between the power source and the discharging circuit. This detection circuit translates the complex task of power source identification into simple voltage level comparisons, enabling reliable discharging control through intermediate signal processing rather than direct complex control logic.
3Reliability
If discharging operation is activated continuously, then voltage safety is ensured, but efficiency decreases due to constant power consumption
Solution Approach 1:
The patent applies dynamics by making the discharging operation adaptive rather than static. The discharge switch is dynamically controlled based on real-time voltage detection results and timing signals. The system transitions between active discharging and idle states according to actual needs, ensuring voltage safety when required while maximizing efficiency during normal operation, thus optimizing the balance between safety and productivity.
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 ensures low power loss, high efficiency, and high security by accurately determining the power source type and preventing false triggering, thereby safely discharging the X capacitor.
Implementation Method 1
a first voltage detection circuit, configured to provide a first indicating signal based on a voltage across the two input terminals of the switching converter
Implementation Method 2
discharging the X capacitor during a first time period
Implementation Method 3
a second voltage detection circuit, configured to sample a voltage across the two input terminals of the switching converter and configured to generate a sampled signal accordingly
Data Source
AI summary
A discharge circuit for an X capacitor has a first voltage detection circuit providing a first indicating signal based on a voltage across two input terminals of a switching converter to indicate whether the two input terminals are connected to an AC power source, and a discharge module starting a discharge operation on the X capacitor based on first indicating signal, and the discharge operation discharges the X capacitor during a first time period, and stops discharging the X capacitor and compares a sampled signal with the voltage across the two input terminals during a following second time period.