Inverter Bootstrap Circuit for Negative Gate Driver Voltage
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Solution Overview
Problem
Existing inverter technologies face challenges in cost-effectively generating auxiliary voltages for gate drivers, particularly in high-current applications, where generating negative turn-off voltages is necessary to prevent unintentional switching and reduce power losses.
Innovation Solution
A novel bootstrap technique that provides bootstrapped positive and negative auxiliary voltages to switch drivers, referenced to common potentials, allowing for efficient generation of both positive and negative auxiliary voltages without requiring a secondary winding of the power supply transformer, thereby reducing component costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a secondary winding of the power supply transformer is used to generate negative auxiliary voltage, then the reliability of preventing unintentional switching is improved, but the device complexity and component costs increase
Solution Approach 1:
The invention extracts the negative auxiliary voltage generation function from the power supply transformer by using a separate voltage inverter circuit. This separates the voltage generation function from the power supply system, eliminating the need for a secondary winding in the transformer while maintaining the ability to generate the required negative voltage for preventing unintentional switching.
Solution Approach 2:
The voltage inverter circuit serves multiple functions: it generates both positive and negative auxiliary voltages for the gate driver, and can operate independently of the power supply transformer configuration. This multi-functional approach eliminates the need for specialized transformer windings while maintaining reliability.
2Ease of manufacture
If positive auxiliary voltage is used for gate driver, then the ease of manufacture is improved, but the power loss increases due to unintentional turn-on events
Solution Approach 1:
The invention applies preliminary anti-action by providing a negative auxiliary voltage to the gate driver before any unintentional turn-on can occur. This negative voltage creates a protective state that prevents the Miller capacitance effect from causing unwanted switching, thereby reducing power loss while maintaining ease of manufacture through the bootstrap circuit approach.
3Ease of manufacture
If negative auxiliary voltage is generated using bootstrap method with diode, then the component costs are reduced, but the ability to provide stable negative voltage for high-current switches is insufficient
Solution Approach 1:
The voltage inverter circuit is self-regulating and can maintain stable negative voltage output without requiring additional expensive components. The circuit automatically adjusts to provide the required voltage stability for high-current switches while keeping component costs low through the use of standard electronic components in a bootstrap configuration.
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 control of semiconductor switches in inverters, reducing power losses and component costs by avoiding the need for additional transformer windings and diodes, while maintaining effective switch control across varying voltage states.
Implementation Method 1
Positive turn-on voltage of the upper semiconductor component can be generated using a method known as a bootstrap method, in which positive turn-on voltage is produced from the positive voltage referenced to the negative voltage busbar
Implementation Method 2
In the bootstrap method the upper gate driver receives positive auxiliary voltage through the diode connected to the gate driver when the power semiconductor connected to the negative voltage busbar is in the conducting state
Implementation Method 3
When negative turn-off voltage is used, the component can be made to cut off the passing current quicker. Furthermore, by keeping the gate in the negative potential with respect to the emitter it is possible to prevent unintentional turn-on of the component
Data Source
AI summary
A two-level or multi-level inverter are supplied with a positive auxiliary voltage (Ug+) and a negative auxiliary voltage (Ug−). A bootstrap technique provides a first positive auxiliary voltage and a first negative auxiliary voltage from the supplied potentials. The bootstrap technique provides at least one additional negative auxiliary voltage to a switch driver of at least one semiconductor switch from the first negative auxiliary voltage. At the start up of an inverter, the inverter can perform a startup sequence to provide auxiliary voltages to the respective auxiliary voltage inputs of the switch drivers by turning the power semiconductors sequentially on and off.