Inverter Bridge Control via Drain-Source Voltage Measurement
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Solution Overview
Problem
Existing control devices for inverter bridge circuits face challenges in reliably interrupting current during short circuits in electric motors, leading to potential damage from high-voltage peaks, and require costly and complex solutions involving phase isolators and additional sensors.
Innovation Solution
A control device with voltmeters and a logic circuit that measures drain-source voltage to determine current direction and intensity, allowing for controlled phase isolation through specific control signals, thereby preventing sudden current interruptions and reducing the risk of high-voltage spikes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If phase isolators are deactivated based on rotor angular velocity, then current interruption capability is improved, but manufacturing cost increases due to oversizing requirements
Solution Approach 1:
The invention changes the control parameter from rotor angular velocity to drain-source voltage measurement. By monitoring the actual voltage across the FET, the system directly detects current flow conditions without needing to oversize phase isolators for worst-case scenarios, thereby reducing manufacturing costs while maintaining reliable current interruption capability.
Solution Approach 2:
The invention replaces the mechanical/indirect measurement approach (rotor angular velocity sensing) with an electrical measurement approach (voltmeter across FET drain-source). This substitution provides direct information about current flow conditions, eliminating the need for oversizing phase isolators and reducing manufacturing costs.
2Measurement precision
If additional ammeters are installed to detect zero ampere current, then phase isolation accuracy is improved, but device complexity increases
Solution Approach 1:
The voltmeter serves multiple functions: it measures drain-source voltage to detect current flow conditions, determines current direction, and provides input for phase isolation control. This multi-functionality eliminates the need for separate ammeters while maintaining accurate phase isolation timing.
Solution Approach 2:
The invention uses drain-source voltage as an intermediary parameter to indirectly measure current flow conditions. Instead of directly measuring current with ammeters, the voltmeter measures voltage across the FET, which serves as a proxy for current flow, simplifying the device while maintaining measurement precision.
3Measurement precision
If voltmeters are connected to each FET for drain-source voltage measurement, then current detection accuracy is improved, but device complexity increases
Solution Approach 1:
The invention uses drain-source voltage as an intermediary parameter to detect current flow conditions. By measuring voltage across the FET rather than directly measuring current, the system achieves accurate current detection while using simpler and more integrated voltage measurement circuits that are already present in power module control.
Solution Approach 2:
The FET's own drain-source voltage provides the measurement signal needed for current detection. The power device itself generates the measurement parameter, eliminating the need for separate current sensing circuits and reducing overall device complexity while maintaining high detection accuracy.
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 solution enables reliable and cost-effective current interruption, minimizing damage to inverter components and extending the service life of phase isolators by using a small number of components to detect and manage current states in the bridge circuit.
Implementation Method 1
The voltage drop is measured at the FET, in particular at its body diode, in order to determine the current intensity - qualitatively and/or quantitatively - and the current direction of the respective phase.
Data Source
Figure 1~2
Figure 3~5
AI summary
The invention relates to a control device for a bridge circuit for controlled generation of AC current. The control device comprises a voltmeter for each FET of a bridge branch, wherein each voltmeter is connectable to the respective FET for drain-source voltage measurement and outputs measured and/or state values, a field effect transistor as phase isolator for each AC current output, wherein the phase isolator(s) is/are connectable to a respective AC current output and switchable by a respective control signal; and a logic circuit for detecting the values of the voltmeters and for outputting control signals to a respective phase isolator. Furthermore, the invention relates to a bridge circuit comprising such a control device.