Power Supply AC-Off State Sensing via PWM Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional power supply devices fail to accurately sense the AC-off state by detecting only one input line for AC power, leading to incomplete power reset and potential abnormal operation.
Innovation Solution
A power supply device with a PWM control module that senses the AC-off state by rectifying AC power into DC power and using a transformer to convert voltage, including a switch, controller, and AC-off detector to determine the AC-off state, ensuring proper power reset and normal operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the power supply device senses AC-off state by detecting only one input line, then the device structure is simple, but the sensing accuracy is insufficient leading to incomplete power reset
Solution Approach 1:
The sensing function is divided into two independent detection paths: one for detecting the AC-off state through the rectifier circuit, and another for generating the reset signal through the capacitor discharge mechanism. This segmentation allows each part to focus on a specific task, improving overall sensing accuracy without proportionally increasing complexity.
Solution Approach 2:
The capacitor is pre-charged during normal operation and automatically discharges when AC power is cut off, generating a reset signal before the system needs to be reset. This preliminary action ensures that the power supply device can quickly and accurately respond to AC-off states without requiring complex real-time detection circuits.
2Reliability
If the power supply device uses a simple detection method for AC-off state, then the device complexity is low, but the reliability is insufficient when AC input lines are shorted
Solution Approach 1:
The rectifier circuit acts as an intermediary between the AC input lines and the sensing mechanism. It converts AC voltage (whether normal or shorted) into a form that can be reliably detected by the capacitor discharge circuit, ensuring accurate AC-off state detection even when AC input lines are shorted, without requiring complex detection circuits.
Solution Approach 2:
The capacitor discharge circuit provides feedback about the AC-off state to the power supply control system. When the capacitor discharges due to AC power cutoff, it generates a reset signal that confirms the AC-off state to the system, ensuring reliable operation under short circuit conditions through this feedback mechanism.
3Reliability
If the power supply device resets driving power in AC-off state, then the abnormal operation is prevented, but the power consumption during sensing increases
Solution Approach 1:
The capacitor naturally charges and discharges in periodic cycles corresponding to the AC power state. During AC-on state, the capacitor charges; during AC-off state, it discharges to generate a reset signal. This periodic action allows the system to sense AC-off states and reset driving power reliably without requiring continuous power consumption for active sensing.
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 enables accurate sensing of AC-off states, preventing abnormal operation by resetting the driving power and maintaining normal operation, even when one or both phases of AC input lines are shorted.
Implementation Method 1
a rectifier configured to rectify AC power into DC power
Implementation Method 2
a transformer configured to supply output voltage by converting voltage of the DC power rectified by the rectifier
Data Source
AI summary
There is provided a power supply device sensing an AC-off state. The power supply device includes a rectifier configured to rectify AC power into DC power, a transformer configured to supply output voltage by converting voltage of the DC power rectified by the rectifier, and a Pulse Width Modulation (PWM) control module configured to output voltage by switching a power switching device connected to the transformer, configured to drive the power supply device by connecting power of an HV pin to a VCC pin, and configured to determine an AC-off state by sensing voltage rectified by the rectifier.