Power Conversion Apparatus Using Parasitic Capacitance for Zero-Voltage Switching
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Solution Overview
Problem
Power conversion efficiency deteriorates in PFC circuits due to reverse currents through parasitic capacitance when switching elements change states, leading to power loss and harmonic issues in converting alternating voltage to direct voltage.
Innovation Solution
A power conversion apparatus with a series circuit of capacitors and switches, along with an inductor and diodes, uses a controller to adjust switching frequencies based on output voltage levels, ensuring zero-voltage switching conditions to minimize power loss and maintain sinusoidal input currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a PFC circuit with switch element is used to improve harmonic characteristics, then input current sine wave quality is improved, but power conversion efficiency deteriorates due to reverse current loss
Solution Approach 1:
The patent utilizes the parasitic capacitance of the diode, which was previously causing harmful reverse current loss, to enable zero-voltage switching. By timing the switch element activation to coincide with the natural voltage zero-crossing point created by the parasitic capacitance discharge, the harmful reverse current is converted into a beneficial switching condition that eliminates power loss while maintaining harmonic correction functionality.
Solution Approach 2:
The patent changes the operational parameters of the PFC circuit by carefully controlling the switching timing of the switch element. By adjusting when the switch element is activated relative to the AC input cycle and utilizing the voltage transient caused by parasitic capacitance, the circuit achieves zero-voltage switching operation, thereby eliminating the power loss associated with traditional PFC circuits while maintaining their harmonic correction capability.
2Productivity
If switch element is switched from off to on state in PFC circuit, then power conversion function is maintained, but reverse current flows through diode causing power loss
Solution Approach 1:
The patent employs preliminary action by allowing the parasitic capacitance of the diode to discharge and create a zero-voltage condition before the switch element is activated. This preliminary voltage transient, caused by the reverse current flowing through the parasitic capacitance when the diode switches off, is harnessed to ensure that the subsequent switch element turn-on occurs at zero voltage, thereby preventing power loss while maintaining the power conversion function.
3Object-generated harmful factors
If PFC circuit is incorporated into AC to DC conversion circuit, then input current waveform is improved, but overall system efficiency deteriorates
Solution Approach 1:
The patent converts the harmful effect of parasitic capacitance in the PFC circuit into a beneficial zero-voltage switching mechanism. By timing the switch element activation to utilize the voltage transient caused by parasitic capacitance discharge, the circuit achieves lossless switching while maintaining the harmonic correction function, thereby improving overall system efficiency without sacrificing input current waveform quality.
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 apparatus achieves high-efficiency power conversion with reduced harmonic noise and stable output voltage by controlling switching frequencies, maintaining sinusoidal input currents without deteriorating power conversion efficiency.
Implementation Method 1
If the switch element is turned on, a current flows to the inductor and magnetic energy is stored in the inductor
Implementation Method 2
Through the electrical energy, an electric charge is stored in the smoothing capacitor, and a voltage of the smoothing capacitor rises due to an increase in the electric charge
Implementation Method 3
When the switch element is switched from the off state to the on state, a reverse current instantly flows to the diode through a parasitic capacitance component of the diode
Data Source
AI summary
A power conversion apparatus sets a point between AC input terminals of a full-wave rectifying circuit as an input terminal of an alternating voltage, connects a series circuit of two capacitors between the input terminals, connects a series circuit of two switches between DC output terminals of the full-wave rectifying circuit, connects one end of a series circuit of a third capacitor and an inductor with a midpoint of the two switches, connects the other end thereof with a connection point of two capacitors, connects a positive electrode side terminal of a smoothing capacitor with a DC output terminal of a positive electrode of the full-wave rectifying circuit via a first diode, connects a negative electrode side terminal of the smoothing capacitor with a DC output terminal of a negative electrode of the full-wave rectifying circuit via a second diode for preventing counter current.