Inverter Current Detection Using Bootstrap Power
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Solution Overview
Problem
Conventional inverter systems require an additional transformer tap for power supply to the overcurrent detection circuit, increasing the size and cost of small-capacity inverters, while existing methods using a DCN detection resistor fail to detect grounding issues in non-corresponding phases.
Innovation Solution
An inverter apparatus utilizing a bootstrap power supply derived from the switching circuit, with an auxiliary circuit comprising a diode, resistor, and capacitor, to power the current detection circuit, eliminating the need for an additional power supply and transformer tap.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an additional transformer tap is used to power the overcurrent detection circuit, then the detection capability is improved, but the device volume and cost increase
Solution Approach 1:
The existing transformer is made to serve dual purposes: its primary function of voltage transformation and an additional function of providing auxiliary power through the secondary winding. The secondary winding, which would otherwise be unused, is utilized to power the overcurrent detection circuit, making the transformer a multi-functional component that eliminates the need for separate power supply windings.
Solution Approach 2:
The transformer serves itself by using its own secondary winding to generate the auxiliary power needed for the detection circuit. Instead of requiring an external or additional power supply system, the transformer leverages its inherent structure to provide both main power transformation and auxiliary power generation, making the system self-sufficient.
2Device complexity
If a DCN detection resistor is used for overcurrent detection, then the device complexity is reduced, but the detection reliability deteriorates due to inability to detect grounding in non-corresponding phases
Solution Approach 1:
The patent introduces an auxiliary power supply circuit as an intermediary component that enables the detection circuit to operate independently at the DCP potential. This intermediary power supply allows the use of high-impedance detection resistors that would otherwise be incompatible with the available power, thereby enabling comprehensive grounding detection while keeping the overall circuit design relatively simple.
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 solution reduces the size and production cost of the overcurrent detection circuit by using bootstrap power, allowing for effective detection of overcurrents without additional switching mode power supplies, while maintaining the ability to detect grounding issues.
Implementation Method 1
a capacitor connected in parallel with the serially connected diode and resistor
Data Source
AI summary
An inverter apparatus having a power supply circuit includes a converter circuit for rectifying AC power into DC power, a smoothening circuit for smoothening the rectified DC power, an inverter circuit for converting the smoothened DC into AC at a variable frequency through a plurality of switches to control a load, and a current detection circuit for detecting overcurrent from the smoothened DC supplied from the inverter circuit, wherein the inverter circuit applies bootstrap power for driving the switches to the current detection circuit to use the bootstrap power as power of the current detection circuit. When bootstrap power for driving switch gates is used, it is possible to use the bootstrap power as the power of the current detection circuit by adding the auxiliary circuit composed of a small number of passive elements.