Input Capacitor Discharge Control in Power Conversion Circuits
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Solution Overview
Problem
Conventional power conversion devices with input capacitor discharge functions using discharge resistors suffer from increased power consumption, which affects efficiency and power factor.
Innovation Solution
A power conversion device and control circuit that utilize a second controller to detect signal waveforms at the input terminal and control a power switch to discharge the input capacitor, reducing power consumption while maintaining high efficiency and power factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a discharge resistor is used to discharge the input capacitor, then the input capacitor discharge function is achieved and user safety is improved, but the power conversion device has preset power consumption which affects efficiency and power factor
Solution Approach 1:
The patent implements periodic discharge action by detecting AC waveform cycles and controlling the power switch to discharge the input capacitor at specific periods (e.g., at zero-crossing points or specific phases of the AC cycle). This replaces continuous discharge through a resistor with periodic discharge events, significantly reducing power consumption while maintaining safety.
Solution Approach 2:
The patent makes the power conversion device itself perform the discharge function using its existing power switch and control circuitry, rather than relying on a separate discharge resistor. The controller utilizes the AC input waveform and internal power switch to create a self-service discharge mechanism that eliminates the need for dedicated discharge components.
2Reliability
If a discharge resistor is configured in parallel with the input capacitor, then the discharge function is provided, but the device complexity increases and efficiency decreases
Solution Approach 1:
The patent makes the power switch serve multiple functions: it acts as both the main power conversion switch and the input capacitor discharge switch. The same power switch that performs rectified power conversion also performs capacitor discharge when controlled by the controller during specific AC waveform conditions, eliminating the need for a separate discharge resistor.
Solution Approach 2:
The patent merges the discharge function with the existing power conversion circuitry by combining the discharge path through the power switch and diode that already exist in the power conversion topology. This integration eliminates separate discharge components and simplifies the overall circuit configuration.
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 reduces power consumption and maintains high efficiency and power factor in power conversion devices by discharging the input capacitor through the existing power conversion loop, without requiring changes to the power conversion circuit design.
Implementation Method 1
The second controller detects a signal waveform at the input terminal, and controls the first controller in response to the signal waveform at the input terminal, so as to utilize the power switch to discharge the charge stored in the input capacitor
Data Source
AI summary
A power conversion device and a control circuit are provided. The power conversion device includes a power conversion circuit and a control circuit. The control circuit includes a first controller and a second controller. The power conversion circuit includes an input capacitor, a rectifier circuit, and a power switch. The input capacitor is coupled to an input terminal of the power conversion device. The rectifier circuit converts an input AC power into a rectified power. The first controller operates the power switch to cause the power conversion circuit to convert the rectified power into an output power. The second controller detects a signal waveform at the input terminal, and controls the first controller in response to the signal waveform at the input terminal, so as to utilize the power switch to discharge the charge stored in the input capacitor.