DC Power Supply Switching Control for Zero-Crossing Short-Circuit Prevention
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Solution Overview
Problem
Conventional DC power supply devices face issues with preventing vertical short-circuits between switching elements due to deviations in zero-crossing timing, which can lead to element breakdown and heat damage, especially when noise affects the AC voltage.
Innovation Solution
A DC power supply device with a rectifier circuit, a reactor, and a charging unit including two switching elements connected in series, controlled by a unit that sets a dead time based on zero-crossing timing to prevent simultaneous switching and includes a control unit that synchronizes switching operations with zero-crossing events to maintain power stability and reduce harmonics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dead time is provided to prevent vertical short-circuit between switching elements, then short-circuit prevention is improved, but noise sensitivity and zero-crossing timing deviation cause unreliable protection
Solution Approach 1:
The control unit continuously monitors the actual zero-crossing timing and adjusts the dead time duration dynamically based on detected deviations. This feedback mechanism ensures that the dead time remains effective even when noise causes timing variations, maintaining reliable short-circuit prevention without being overly sensitive to noise
Solution Approach 2:
The dead time is transformed from a fixed value to a dynamic parameter that adapts to actual operating conditions. The control unit modifies the dead time duration in real-time based on zero-crossing detection, allowing the system to maintain optimal protection while accommodating noise-induced timing variations
2Use of energy by moving object
If zero-crossing timing is used to control switching elements, then power conversion efficiency is improved, but timing deviation leads to simultaneous switching and vertical short-circuit
Solution Approach 1:
The control unit detects zero-crossing timing in advance and proactively adjusts the dead time duration before switching operations occur. This preliminary adjustment ensures that even if timing deviations occur during switching, the protective dead time is already optimized to prevent simultaneous switching and vertical short-circuit
Solution Approach 2:
The system continuously monitors zero-crossing timing and uses this feedback to dynamically adjust the dead time, ensuring that power conversion efficiency is maintained while preventing timing deviation from causing simultaneous switching
3Speed
If switching elements are operated at high frequency, then power conversion speed is improved, but risk of simultaneous switching and element breakdown increases
Solution Approach 1:
The dead time duration is made dynamic and adapts to the switching frequency and zero-crossing timing. At higher switching frequencies, the control unit automatically adjusts the dead time to maintain adequate separation between switching events, preventing simultaneous switching and element breakdown while preserving high conversion speed
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 prevents vertical short-circuits between switching elements, thereby avoiding element breakdown and heat damage, even when zero-crossing timing deviates, ensuring reliable operation and power quality.
Implementation Method 1
a rectifier circuit that converts AC power into DC power
Implementation Method 2
a reactor connected at one end to one output terminal of the rectifier circuit
Implementation Method 3
a charging unit including a first switching element and a second switching element connected in series between another end of the reactor and another output terminal of the rectifier circuit
Data Source
AI summary
A DC power supply device includes: a rectifier circuit; a reactor connected at one end to one output terminal of the rectifier circuit; a charging unit including a first and second switching element connected in series between another end of the reactor and another output terminal of the rectifier circuit, the charging unit configured to charge a first and second capacitor connected in series between output terminals to which a load is connected; and a control unit that controls the charging unit. The control unit sets, based on the timing at which the zero-crossing occurs, a dead time in which both the and second switching element are off, and when states of the first and second switching element at a time of occurrence of the zero-crossing match a predetermined set of states, reverses the states of the first switching element and the second switching element.