PWM AC/DC Topology for Isolated DC Loads With Low AC Ripple
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Solution Overview
Problem
Existing AC/DC conversion systems, particularly those using 12-pulse SCR rectifiers, suffer from high AC ripple voltage, large filter size and weight, high cost, and poor power factor, leading to inconsistencies in electroplating processes and increased manufacturing costs due to thickness variations and inefficient use of plating solutions.
Innovation Solution
The implementation of an adjustable AC/DC conversion topology using a PWM inverter, sinewave filter, multiphase isolation transformer, and multi-pulse diode bridge rectifier, which generates a regulated isolated DC load with ultra-low AC ripple by operating at higher frequencies, reducing filter size and weight, and improving power factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If 12-pulse SCR rectifiers are used for AC/DC conversion, then the system can provide regulated DC output, but the AC ripple voltage becomes high and filter size increases
Solution Approach 1:
The patent applies dynamic control by using PWM inverters that can rapidly adjust switching frequencies and duty cycles to regulate DC output while minimizing AC ripple. The system dynamically adapts operating parameters based on load conditions to maintain low ripple across varying output requirements
Solution Approach 2:
The invention changes key operating parameters by switching from fixed-frequency SCR rectification to variable-frequency PWM operation. By adjusting switching frequency and pulse width parameters, the system achieves both regulated DC output and reduced AC ripple without requiring oversized filters
2Object-affected harmful factors
If higher frequency operation is used to reduce AC ripple, then ripple voltage decreases, but system complexity increases
Solution Approach 1:
The PWM inverter circuit performs multiple functions simultaneously: it rectifies AC to DC, regulates output voltage, minimizes AC ripple, and provides transient load control. This multi-functionality reduces overall system complexity despite the higher switching frequencies used
3Object-affected harmful factors
If larger filters are used to reduce AC ripple, then ripple voltage decreases, but filter size and weight increase
Solution Approach 1:
The patent replaces mechanical/filter-based ripple reduction with electronic control methods. PWM switching and active circuitry substitute for large passive LC filters, achieving ripple reduction without the weight penalty of oversized filtering components
4Reliability
If 12-pulse SCR rectifiers are used, then DC output can be regulated, but power factor deteriorates
Solution Approach 1:
The system employs feedback control mechanisms that monitor output conditions and adjust input current waveform accordingly. This feedback ensures unity power factor operation while maintaining regulated DC output, as the control system actively corrects power factor based on real-time load conditions
5Reliability
If conventional AC/DC conversion is used, then basic DC output is achieved, but transient load control is poor
Solution Approach 1:
The PWM control system provides dynamic response to transient load changes by rapidly adjusting switching parameters. This dynamic control capability enables excellent transient load regulation while maintaining stable DC output under varying conditions
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 solution achieves significant reduction in AC ripple voltage, filter size, and cost, while maintaining consistent film thickness and reducing manufacturing costs by providing a stable and efficient electroplating process with improved power factor and transient load control.
Implementation Method 1
a PWM inverter to generate a first AC signal
Implementation Method 2
a sinewave filter to receive the first AC signal and provide a filtered AC signal
Implementation Method 3
generating a plurality of isolated AC signals according to the filtered AC signal using a multiphase isolation transformer
Implementation Method 4
rectifying the isolated AC signals to generate a DC rectifier output signal using a multi-pulse diode bridge rectifier
Implementation Method 5
filtering the DC rectifier output signal to generate a filtered DC rectifier output signal using an output filter
Implementation Method 6
The DC signal is coupled through the blocking diode to a corresponding anode
Data Source
AI summary
Systems, methods and power converters are disclosed to provide regulated individual DC output signals to anode structures using a PWM inverter to generate a first AC signal, a sinewave filter to provide a filtered AC signal, a multiphase isolation transformer to provide a plurality of isolated AC signals, a multi-pulse diode bridge rectifier to provide a DC rectifier output signal, an output filter to provide a filtered DC rectifier output signal, and a blocking diode to provide the filtered DC rectifier output signal.