Half Bridge Inverter with Reactive Filter for Parasitic Resonance
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Solution Overview
Problem
Conventional half bridge inverter circuits face issues with parasitic resonances and high-voltage spikes when used with electrical loads having substantial inductance, requiring large filters that increase cost and limit frequency range, while existing filters with lower cut-off frequencies are too large and inefficient.
Innovation Solution
A half bridge circuit with a filter having a 3 dB roll-off frequency greater than 5 kHz and a cut-off frequency greater than 50 kHz, utilizing III-N transistors that can switch at frequencies up to 80 kHz or higher without substantial losses, allowing for a compact and efficient design by eliminating the need for diodes and reducing the size of inductive and capacitive elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a filter with low cut-off frequency is used to attenuate switching waveform, then filtering effectiveness is improved, but filter size and cost increase substantially
Solution Approach 1:
The patent changes the switching frequency parameter from conventional 12-50 kHz to much higher frequencies (100 kHz to 1 MHz), which allows the filter cut-off frequency to be raised proportionally. This parameter change enables effective filtering with much smaller inductor and capacitor values, resolving the contradiction between filtering effectiveness and filter size.
Solution Approach 2:
The patent uses high-frequency periodic switching action (100 kHz to 1 MHz) instead of conventional low-frequency switching. This high-frequency periodic action allows the use of smaller filter components while maintaining effective attenuation of switching ripple, as the higher frequency provides more frequent resetting of the filter components.
2Volume of stationary object
If switching frequency is increased to reduce filter size, then filter components can be smaller, but switching losses increase substantially
Solution Approach 1:
The patent replaces conventional mechanical/semiconductor switches (IGBTs, MOSFETs) with resonant switching using capacitive and inductive elements. The resonant tank circuit performs the switching function through natural oscillation at the desired high frequency, eliminating the need for active semiconductor switches and their associated switching losses.
Solution Approach 2:
The patent employs resonant vibration at high frequencies (100 kHz to 1 MHz) using an LC tank circuit. This resonant oscillation enables high-frequency operation without the switching losses inherent in conventional semiconductor switches, as the energy transfer occurs through the natural resonance of the circuit elements rather than forced switching.
3Device complexity
If conventional switches are used in half bridge, then circuit simplicity is maintained, but maximum switching frequency is limited to 50 kHz
Solution Approach 1:
The patent uses high-frequency periodic resonant oscillation (100 kHz to 1 MHz) instead of conventional low-frequency switching. The resonant tank circuit naturally oscillates at the desired high frequency when energized, providing the high-speed operation needed while maintaining circuit simplicity through the use of passive resonant elements rather than complex active switching control.
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
Enables the delivery of sinusoidal AC voltage signals at frequencies above 1 kHz with minimal distortion, achieving a compact module size and high output power while preventing substantial output ripple, thus addressing the limitations of conventional filters and inverter circuits.
Implementation Method 1
A filter 20, which includes an inductive element 21 and a capacitive element 22, is then used to filter the switching waveform
Implementation Method 2
the filter 20 must have a sufficiently low cut-off frequency to effectively attenuate the switching waveform
Implementation Method 3
any capacitance in the cable 14 or motor 15 will be charged and discharged at the switching rate
Implementation Method 4
utilizing III-N transistors that can switch at frequencies up to 80 kHz or higher without substantial losses
Implementation Method 5
reducing the size of inductive and capacitive elements
Data Source
AI summary
An electronic component comprising a half bridge adapted for operation with an electrical load having an operating frequency is described. The half bridge comprises a first switch and a second switch each having a switching frequency, the first switch and the second switch each including a first terminal, a second terminal, and a control terminal, wherein the first terminal of the first switch and the second terminal of the second switch are both electrically connected to a node. The electronic component further includes a filter having a 3 dB roll-off frequency, the 3 dB roll-off frequency being less than the switching frequency of the switches but greater than the operating frequency of the electrical load. The first terminal of the filter is electrically coupled to the node, and the 3 dB roll-off frequency of the filter is greater than 5 kHz.