SCR Rectifier With Supercapacitor for Back-EMF Energy Recovery
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Solution Overview
Problem
Conventional variable-frequency drives (VFDs) require a braking unit with electrolytic capacitors to prevent damage from counter electromotive force (EMF) generated by inductive loads, which increases complexity and size, and does not efficiently manage energy storage and reuse.
Innovation Solution
An AC-to-DC converter using a supercapacitor or lithium-ion capacitor with silicon controlled rectifiers (SCRs) and control units to convert AC input voltage to DC output voltage, eliminating the need for a braking unit by storing and reusing energy from counter EMF, and stabilizing the DC output voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a braking unit with electrolytic capacitor is used to prevent counter EMF damage, then component reliability is improved, but device complexity and size increase
Solution Approach 1:
The patent removes the braking unit (switch and bleeder resistor) from the conventional VFD circuit by extracting its protective function and integrating it directly into the rectifier circuit through the controlled rectifier's anti-parallel diode configuration, thereby simplifying the overall device structure while maintaining component protection
Solution Approach 2:
The patent merges the counter EMF protection function with the rectifier circuit by using the anti-parallel diode of the controlled rectifier to handle both rectification and counter EMF suppression, combining multiple functions into a single integrated circuit structure
2Reliability
If a braking unit with electrolytic capacitor is used to prevent counter EMF damage, then component reliability is improved, but the size of VFD increases
Solution Approach 1:
The patent removes the braking unit (switch and bleeder resistor) from the conventional VFD circuit by extracting its protective function and integrating it directly into the rectifier circuit through the controlled rectifier's anti-parallel diode configuration, thereby simplifying the overall device structure while maintaining component protection
Solution Approach 2:
The patent merges the counter EMF protection function with the rectifier circuit by using the anti-parallel diode of the controlled rectifier to handle both rectification and counter EMF suppression, combining multiple functions into a single integrated circuit structure
3Stability of the object's composition
If conventional electrolytic capacitor is used for filtering, then filtering function is achieved, but energy storage and reuse efficiency is poor
Solution Approach 1:
The patent changes the fundamental parameter of the energy storage medium from conventional electrolytic capacitor to supercapacitor, utilizing the supercapacitor's significantly higher capacitance value to achieve both superior voltage stabilization and efficient energy storage and reuse, with energy efficiency reaching up to 60%
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 reduces the size and complexity of the VFD, enables efficient energy storage and reuse, and achieves up to 60% reduction in electric energy consumption compared to conventional systems, while protecting components from counter EMF damage.
Implementation Method 1
an energy storage element, a plurality of silicon controlled rectifiers (SCRs), and a first control unit. The energy storage element is one of a supercapacitor and a lithium-ion capacitor
Implementation Method 2
The SCRs are configured to receive a control signal, and to be controlled to switch between a conducting state and a non-conducting state based on the control signal so as to convert the AC input voltage into a DC output voltage
Implementation Method 3
The first control unit is configured to detect zero-crossing points of the AC input voltage and a magnitude of the DC output voltage, and to generate the control signal based on the zero-crossing points and the magnitude of the DC output voltage
Data Source
AI summary
An AC-to-DC converter adapted to receive an AC input voltage includes an energy storage element, a plurality of SCRs, and a first control unit. The energy storage element is a supercapacitor or a lithium-ion capacitor. The SCRs are electrically connected to each other to form a full-bridge rectifier that is disposed to receive the AC input voltage, and are electrically connected to the energy storage element. The SCRs are configured to receive a control signal, and to be controlled to switch between a conducting state and a non-conducting state based on the control signal so as to convert the AC input voltage into a DC output voltage. The first control unit is configured to generate the control signal based on the AC input voltage and the DC output voltage in a manner that causes the DC output voltage to be at a predetermined voltage magnitude.