Bootstrap Diode Linking for Three-Level Converter Drive
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Solution Overview
Problem
Multilevel converters face challenges in obtaining a three-level output due to the inability to supply power to bootstrap circuits when the low-potential-side switch is deactivated, preventing the activation of high-potential-side switches.
Innovation Solution
A three-level converter configuration that includes a switch circuit with first to fourth switch groups connected in series, an inductor, a flying capacitor, and bootstrap circuits, where the cathode of a boot diode in the high-potential-side bootstrap circuit is connected to the anode of a boot diode in the low-potential-side bootstrap circuit, allowing power supply to the bootstrap circuits even when the low-potential-side switch is deactivated.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the low-potential-side switch is deactivated to obtain three-level output, then the output voltage level is improved, but the power supply to the bootstrap circuit is lost preventing high-potential-side switch activation
Solution Approach 1:
The patent introduces a dedicated power supply circuit as an intermediary component that provides power to the bootstrap circuit independently of the switch states. This power supply circuit includes a power supply unit connected to the high-potential-side input terminal and a power supply potential conversion unit that converts the high potential to a lower potential suitable for the bootstrap circuit, enabling continuous power supply regardless of whether the low-potential-side switch is activated or deactivated.
2Device complexity
If the bootstrap circuit is connected to the common power supply, then the circuit structure is simplified, but the high-potential-side switch cannot be activated when the low-potential-side switch is deactivated
Solution Approach 1:
The patent segments the power supply system into two independent parts: a common power supply for general circuit operation and a dedicated power supply circuit for the bootstrap circuit. This segmentation allows the bootstrap circuit to maintain its power supply independently of the common power supply's state, enabling the high-potential-side switch to be activated even when the low-potential-side switch is deactivated, without significantly increasing overall circuit 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
Enables the achievement of a three-level output by ensuring power is supplied to the bootstrap circuits, even if the low-potential side switch is deactivated, thereby allowing the high-potential side switch to be activated, thus obtaining a stable three-level output.
Implementation Method 1
A cathode of a boot diode in one of the bootstrap circuits that is connected to one of the drive circuits to drive one of the switches located at the lowest potential side in the second switch group, is connected to an anode of a boot diode in another one of the bootstrap circuits in the second switch group.
Data Source
AI summary
A three-level converter includes a switch circuit including first to fourth switch groups with n switches. A boot diode connected to a drive circuit to drive a switch on a lowest voltage side of a second switch group includes a cathode to which an anode of another boot diode of the second switch group is connected. A boot diode connected to a drive circuit to drive a switch element on a lowest voltage side of a third switch group includes a cathode to which an anode of another boot diode of the third switch group is connected. A boot diode connected to a drive circuit to drive a switch on a lowest voltage side of a fourth switch group includes a cathode to which an anode of another boot diode of the fourth switch group is connected.