T-Type Inverter Absorption Unit Reduces Switch Voltage Stress
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Solution Overview
Problem
Existing T-type three-level inverter circuits face challenges with weak absorption capacity and high voltage stress on bidirectional switches, requiring high-voltage withstanding tubes that are difficult to adapt to high-frequency applications and result in increased losses.
Innovation Solution
A T-type three-level inverter circuit design featuring a bidirectional switch with controllable switches in inverse series connection, an absorption unit comprising resistors, capacitors, and diodes, which reduces voltage stress by clamping capacitors to bus voltages, allowing for the use of transistors with lower breakdown voltage and minimizing losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If RC absorption scheme is used in bidirectional switch, then circuit structure is simple, but absorption capacity is weak and voltage stress is high
Solution Approach 1:
The absorption unit is segmented into two symmetrical halves, each handling one polarity of voltage stress. Each half includes a resistor, capacitor, and diode connected in specific configuration to provide independent absorption for positive and negative voltage excursions, thereby strengthening overall absorption capacity while maintaining structural clarity
Solution Approach 2:
The bidirectional switch is configured with symmetrical absorption circuits on both sides, creating equipotential conditions for voltage stress distribution. This symmetry ensures that both controllable switches experience equal voltage stress conditions, optimizing the use of lower-breakdown-voltage transistors while maintaining balanced absorption performance
2Strength
If high-voltage withstanding tube is adopted, then voltage stress resistance is improved, but adaptability to high-frequency application deteriorates and loss increases
Solution Approach 1:
Absorption capacitors are introduced as intermediary elements between the voltage stress source and the controllable switches. These capacitors absorb voltage spikes and reduce the stress transmitted to the switches, allowing the use of transistors with lower breakdown voltage ratings while maintaining high-frequency operation capability
Solution Approach 2:
The absorption unit changes the voltage stress parameters by clamping the voltage across controllable switches to lower values. By introducing capacitors with specific capacitance values, the peak voltage stress is reduced from the original high-voltage level to a lower level that standard transistors can withstand, thereby enabling high-frequency operation with reduced losses
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
The design effectively reduces voltage stress on switches, enabling the use of lower-cost transistors with lower breakdown voltage, while maintaining strong absorption capacity and minimizing losses, thus improving the circuit's efficiency and adaptability to high-frequency applications.
Implementation Method 1
a second terminal of the first capacitor and a positive electrode of the first diode are respectively connected to a first electrode and a second electrode of the first controllable switch
Implementation Method 2
When the first controllable switch in the bidirectional switch is off, the first capacitor clamps the first controllable switch through the first diode, and a clamping voltage is the positive bus voltage
Implementation Method 3
a second terminal of the second capacitor and a negative electrode of the second diode are respectively connected to a second electrode and a first electrode of the second controllable switch
Implementation Method 4
When the second switch in the bidirectional switch is on, the second capacitor clamps to the negative bus through the second resistor and the third diode. When the second controllable switch in the bidirectional switch is off, the second capacitor clamps the second controllable switch through the second diode
Implementation Method 5
a first terminal of the first resistor is connected to a positive bus terminal, and a second terminal of the first resistor is connected to a first terminal of the first capacitor
Implementation Method 6
the absorption unit including a first resistor, a first capacitor, a first diode, a second resistor, a second capacitor, and a second diode
Data Source
AI summary
This invention relates to a T-type three-level inverter circuit. The circuit includes an absorption unit. In the absorption unit, a first terminal of the first resistor is connected to a positive bus terminal, and a second terminal of the first resistor is connected to a first terminal of the first capacitor and a negative electrode of the first diode; a second terminal of the first capacitor and an positive electrode of the first diode are respectively connected to an emitter and a collector of the first controllable switch tube; a first terminal of the second resistor is connected to a negative bus terminal, and a second terminal of the second resistor is connected to a positive electrode of a third diode; a negative electrode of the third diode is connected to both a first terminal of the second capacitor and a positive electrode of a second diode; and a second terminal of the second capacitor and a negative electrode of the second diode are respectively connected to a collector and a emitter of the second controllable switch tube. As the T-type three-level inverter circuit according to the invention is implemented, a voltage stress on the bidirectional switch tube is effectively reduced due to strong absorption capacity of the absorption unit, and thus the bidirectional switch tube can adopt a tube having a relatively low breakdown voltage value. Moreover, the absorption unit has a low cost and a small loss.