Active Filter Circuit Reduces Input Voltage Ripple in Inverter Apparatus
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Solution Overview
Problem
Conventional inverter apparatuses face challenges in suppressing input voltage ripple without using high-capacitance smoothing capacitors, which limits their lifespan and effectiveness, especially when using film capacitors, which provide insufficient ripple suppression.
Innovation Solution
An inverter apparatus incorporating an active filter circuit with a buffer capacitor, inductor, rectifier device, and switch device, along with a switching control circuit, that stores and releases energy to reduce input voltage ripple, allowing for the use of lower capacitance film capacitors and effectively drawing DC power from the input supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a high-capacitance smoothing capacitor (electrolytic capacitor) is used to suppress input voltage ripple, then the ripple suppression effect is improved, but the apparatus lifetime is limited due to short capacitor lifetime
Solution Approach 1:
The patent introduces an active filter circuit as an intermediary component between the power supply and the inverter circuit. This active filter includes a buffer capacitor, inductor, and switching device that work together to suppress input voltage ripple without requiring a large smoothing capacitor. The active filter circuit acts as a mediator that handles the ripple suppression function, allowing the use of smaller, longer-lived film capacitors instead of large electrolytic capacitors.
Solution Approach 2:
The patent changes the capacitance parameter of the smoothing capacitor from high capacitance (electrolytic capacitor) to low capacitance (film capacitor). By introducing the active filter circuit, the system can operate effectively with a much smaller capacitor value, thereby extending the apparatus lifetime while maintaining adequate ripple suppression through the combined action of the active filter and the smaller film capacitor.
2Duration of action of stationary object
If a low-capacitance smoothing capacitor (film capacitor) is used to extend apparatus lifetime, then the apparatus lifetime is improved, but the ripple suppression effect is insufficient
Solution Approach 1:
The active filter circuit serves as an intermediary that compensates for the insufficient ripple suppression capability of low-capacitance film capacitors. The active filter actively counteracts voltage ripples through its switching mechanism, enabling the system to use durable film capacitors while achieving adequate ripple suppression performance.
Solution Approach 2:
The patent employs a dynamic active filter circuit with switching devices that actively adjust to counteract voltage ripples. Unlike passive capacitive filtering, this dynamic approach allows the system to maintain effective ripple suppression with smaller capacitor values by actively compensating for ripple variations in real-time through controlled switching operations.
3Object-affected harmful factors
If a smoothing capacitor with high capacitance is used, then the ripple suppression effect is improved, but the device complexity and cost increase
Solution Approach 1:
The active filter circuit acts as an intermediary that enables the use of simpler, lower-capacitance film capacitors instead of complex high-capacitance electrolytic capacitors. The active filter handles the heavy lifting of ripple suppression, allowing the capacitor to be a simpler component with lower specifications.
Solution Approach 2:
The patent replaces expensive, high-capacitance electrolytic capacitors with cheaper, low-capacitance film capacitors combined with an active filter circuit. While the active filter adds circuit complexity, the overall system becomes more cost-effective and reliable by using durable film capacitors that don't require frequent replacement.
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 active filter circuit reduces input voltage ripple, enabling the use of lower capacitance film capacitors instead of high-capacitance electrolytic capacitors, thereby extending the apparatus' lifespan and improving ripple suppression without the need for high-capacitance smoothing capacitors.
Implementation Method 1
The inductor stores energy while the switch device is on and releases the energy while the switch device is off
Implementation Method 2
the rectifier device is configured to conduct so as to allow the energy stored in the inductor to be released
Implementation Method 3
a buffer capacitor connected between an input node and an output node... the capacitor is charged to the DC voltage of the input power supply. During a period in which the AC voltage output from the inverter apparatus is near the maximum, the capacitor is discharged
Data Source
AI summary
In an inverter apparatus, an output voltage of an active filter circuit that steps up and smoothes a DC voltage is converted into an AC voltage by an inverter circuit. The active filter circuit includes a capacitor and a rectifier device connected between an input node and an output node. An inductor, one end of which is connected to the input node and the other end of which is connected the output node through the rectifier device, and a switch device connected between the other end and a low-potential-side line, and a first control circuit for the switch device are provided. The inductor stores energy while the switch device is on and releases the energy while the switch device is off. The rectifier device conducts such that the stored energy of the inductor is released.