Power Converter Input Discharge Circuit for EMI Capacitor Safety
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Solution Overview
Problem
Existing discharge circuits for EMI filter capacitors in power systems dissipate power continually when the electrical energy source is connected, which is inefficient and violates emerging energy efficiency standards.
Innovation Solution
A discharge circuit using a control circuit and switch configuration that maintains high impedance when the energy source is connected, and switches to discharge the capacitor quickly when the source is disconnected, minimizing power dissipation and ensuring safety by discharging the capacitor to a safe voltage within a specified time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If resistors are permanently connected across the X capacitor terminals to discharge the capacitor, then the voltage across the input terminals is reduced to a safe value within the specified time, but power is dissipated continually in the resistance when the source of electrical energy is connected
Solution Approach 1:
The patent applies the dynamics principle by making the discharge circuit dynamically controllable through a control circuit that monitors the connection state of the electrical energy source. The switching element changes the impedance state of the discharge circuit based on detected conditions: high impedance (off state) when the source is connected to minimize power loss, and low impedance (on state) when the source is disconnected to ensure safety discharge. This dynamic adaptation resolves the contradiction between continuous safety discharge capability and continuous power dissipation.
Solution Approach 2:
The patent employs parameter changes by varying the impedance parameter of the discharge circuit based on the operational state. The control circuit detects whether the electrical energy source is connected and accordingly adjusts the impedance of the discharge circuit between high and low states. This parameter change allows the system to achieve both low power dissipation during normal operation and effective discharge during disconnection, resolving the technical contradiction.
2Speed
If the impedance of the discharge circuit is kept low to ensure rapid discharge, then the discharge time constant is reduced, but power dissipation increases continually
Solution Approach 1:
The patent makes the discharge circuit impedance dynamic rather than static. The control circuit monitors the connection state of the electrical energy source and switches the discharge circuit impedance between high and low states accordingly. When the source is connected, the impedance is high to minimize power dissipation. When the source is disconnected, the impedance switches to low to achieve rapid discharge. This dynamic impedance control resolves the contradiction between discharge speed and power dissipation.
3Loss of energy
If a switching element is introduced to control the discharge circuit, then power dissipation is minimized during operation, but the device complexity increases
Solution Approach 1:
The patent applies the multi-functionality principle by designing a control circuit that performs multiple functions: it monitors the connection state of the electrical energy source, determines whether discharge is needed, and controls the switching element accordingly. This integrated approach consolidates multiple functions into a single control mechanism, reducing the overall device complexity while achieving the goal of minimizing power dissipation through controlled switching.
Solution Approach 2:
The control circuit is configured to automatically detect the connection state of the electrical energy source and autonomously control the switching element without requiring external intervention. The circuit serves itself by using its own monitoring capability to trigger the appropriate discharge action, simplifying the overall system architecture while achieving energy efficiency.
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 virtually eliminates power dissipation in discharge resistors while ensuring the EMI filter capacitors are discharged safely and efficiently when the energy source is uncoupled, aligning with energy efficiency standards and safety requirements.
Implementation Method 1
capacitance (102) between a pair of input terminals (120, 140) of the power converter
Implementation Method 2
dissipate power continually in the resistance
Data Source
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AI summary
[A circuit to discharge a capacitance between input terminals of a power system is disclosed. An example circuit includes a control circuit coupled to an input of a power system. The control circuit is coupled to detect whether an electrical energy source is coupled to an input of the power system. A switch is also included and is coupled to the control circuit and to the input of the power system. The control circuit is coupled to drive the switch in a first operating mode when the electrical energy source is coupled to the input of the power system. The control circuit is coupled to drive the switch in a second operating mode when the electrical energy source is uncoupled from the input of the power system. A capacitance coupled between input terminals of the input of the power system is discharged through the switch to a threshold voltage in less than a maximum period of time from when the electrical power source is uncoupled from the input terminals of the power system.