Power Supply Discharge Circuit Using Control Unit Voltage Sampling
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Solution Overview
Problem
Conventional power supply apparatuses incur energy loss due to the presence of a bleeder resistor, which is used to discharge electric energy from an AC safety capacitor, posing a risk of electric shock when the power is turned off.
Innovation Solution
A power supply apparatus that omits the bleeder resistor by using a control unit to sample and compare the voltage between the AC safety capacitor's terminals and the AC input voltage, determining whether to discharge the capacitor based on the stability of the input voltage, thereby reducing energy loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bleeder resistor is configured to discharge electric energy from the AC safety capacitor, then user safety is improved (electric shock risk avoided), but energy loss increases
Solution Approach 1:
The patent implements periodic discharge of the AC safety capacitor by using the control unit to detect voltage levels at specific time intervals (e.g., 100ms periods) and activate the discharge circuit only when voltage exceeds the threshold, rather than continuous discharge through a bleeder resistor. This periodic action maintains safety while significantly reducing energy loss.
Solution Approach 2:
The control unit utilizes its existing voltage sampling and processing capabilities to simultaneously perform both control functions and safety discharge detection. By reusing the voltage detection mechanism already present in the power supply system, the patent eliminates the need for separate dedicated discharge components, reducing overall system energy consumption while maintaining safety.
2Reliability
If a bleeder resistor is used to discharge the AC safety capacitor, then electric shock risk is eliminated, but device complexity increases
Solution Approach 1:
The control unit is designed to perform multiple functions: it controls the power conversion circuit operation, samples voltage for control decisions, and simultaneously detects voltage levels on the AC safety capacitor to trigger discharge when needed. This multi-functionality eliminates the need for separate dedicated discharge control circuitry, reducing overall device complexity.
Solution Approach 2:
The patent combines the voltage sampling function and the discharge control function into a single integrated control unit. The same voltage detection mechanism used for power conversion control is also used to monitor AC safety capacitor voltage, merging multiple safety and control functions into one component, thereby simplifying the overall circuit architecture.
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
This approach allows for real-time detection of stable AC input voltage and controlled discharge of the capacitor, eliminating the need for a bleeder resistor and reducing energy loss, resulting in a power-saving effect.
Implementation Method 1
an AC safety capacitor in the EMI filter is used to filter noises probably existed in an AC signal. As the capacitor has a characteristic of storing electric energy
Implementation Method 2
a bleeder resistor is further configured in the EMI filter to connect the AC safety capacitor in parallel, such that when an AC power of the power supply apparatus is turned off, the AC safety capacitor can discharge the electric energy through the bleeder resistor
Implementation Method 3
the control unit samples and holds a voltage between two terminals of the AC safety capacitor to obtain a holding voltage, and compares the holding voltage and the AC input voltage during each period of a clock signal
Data Source
AI summary
A power supply apparatus is provided. The power supply apparatus includes a power conversion circuit, an AC safety capacitor and a control unit. An AC input voltage is received by an input side of the power converting circuit, and is converted to a DC output voltage. The AC safety capacitor is connected across the input side. The control unit controls the operation of the power converting circuit, where the control unit samples and holds a voltage between two terminals of the AC safety capacitor to obtain a holding voltage, and compares the holding voltage and the AC input voltage during each period of a clock signal, so as to decide to discharge electric energy stored by the AC safety capacitor according to a comparison result.