Inverter Circuit Control for Wide-Range Zero-Voltage Switching
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Solution Overview
Problem
Conventional inverter circuits face challenges in performing zero voltage switching (ZVS) and achieving high efficiency due to the dependency on the ratio between DC input voltage and AC output voltage, and significant changes in switching frequency with AC output voltage variations.
Innovation Solution
The inverter circuit includes a series circuit with a control switch and synchronous rectification switch connected in parallel to a DC power supply, a reactor, and an output capacitor, controlled by a circuit that manages the ON and OFF times of these switches to maintain zero voltage switching across a wide range of AC output voltage values, using specific ON times and reverse current settings to stabilize switching frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional critical inverter circuit performs synchronous rectification, then zero voltage switching can be achieved, but only when DC input voltage is equal to or more than twice the AC output voltage (Vin≥2VO)
Solution Approach 1:
The patent applies dynamic control by making the ON time of the synchronous rectification switch variable based on the instantaneous AC output voltage value. The control circuit dynamically adjusts the ON time according to the relationship between DC input voltage and instantaneous AC output voltage, enabling zero voltage switching across a wide voltage range without being constrained by the conventional Vin≥2VO limitation.
2Productivity
If switching frequency is increased to improve conversion speed, then productivity increases, but switching losses increase reducing efficiency
Solution Approach 1:
The patent applies partial action by using synchronous rectification only during the appropriate phase when the synchronous rectification switch is turned on, rather than continuous switching. This allows the control switch to operate at higher frequencies for fast response while the synchronous rectification switch handles current conduction during specific intervals, reducing overall switching losses while maintaining high conversion speed.
3Adaptability or versatility
If switching frequency is made variable to adapt to AC output voltage changes, then adaptability improves, but efficiency decreases due to high switching losses
Solution Approach 1:
The patent introduces an intermediary control mechanism that uses the relationship between DC input voltage and instantaneous AC output voltage to determine the ON time of the synchronous rectification switch. This intermediary control layer allows the system to adapt to voltage changes while maintaining optimal switching conditions, avoiding excessive switching frequency changes that would cause high losses.
4Adaptability or versatility
If DC input voltage is increased to expand operating range, then adaptability improves, but device complexity and cost increase
Solution Approach 1:
The patent changes the control parameter from fixed switching frequency or fixed voltage ratios to variable ON time of the synchronous rectification switch based on instantaneous voltage conditions. By adjusting the ON time parameter dynamically according to the relationship between DC input voltage and AC output voltage, the system achieves wide voltage range adaptability without increasing hardware complexity.
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 approach enables reliable zero voltage switching and reduces switching frequency variations, leading to improved efficiency and reduced switching losses across all phases of AC output voltage.
Implementation Method 1
a reactor (L) having one end connected to a connection point between the control switch Q1 and the synchronous rectification switch Q2... generate reverse current in the reactor
Implementation Method 2
an output capacitor (Co) that is connected between another end of the reactor (L) and a power supply line of a DC power supply... outputs the AC output voltage to both ends
Data Source
AI summary
An inverter circuit (100) includes a series circuit connected in parallel to a DC power supply (Vin) and having a control switch (Q1) and a synchronous rectification switch (Q2) connected in series, a reactor (L) having one end connected to a connection point between the control switch (Q1) and the synchronous rectification switch (Q2), an output capacitor (Co) connected between a power line of the DC power supply (Vin) and another end of the reactor (L), and a control circuit that controls ON time (tonQ1) of the control switch (Q1) and ON time (tonQ2) of the synchronous rectification switch (Q2) so as to generate reverse current (Ir) in the reactor (L) in an entire range of an instantaneous value (VO) of AC output voltage (vo).