Three-Phase BLDC Current Sensing Without Shunt Resistors
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Solution Overview
Problem
Existing methods for driving three-phase motors with three-phase current are inefficient due to high power consumption and the need for numerous components, particularly shunt resistors, which cause energy loss and heat generation.
Innovation Solution
A method and device using a half-bridge configuration with semiconductor power control means, such as FETs or IGBTs, that measures and calculates three-phase current phases to determine the rotation angle and current phases for each sector, eliminating the need for shunt resistors and reducing component count and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If shunt resistors are used to measure three-phase current, then current measurement is achieved, but power consumption increases and heat generation occurs
Solution Approach 1:
The patent extracts and eliminates the shunt resistors from the measurement system. Instead of using traditional shunt resistors to measure current, the invention uses the existing half-bridge configuration's semiconductor power control means to detect current by measuring voltage across the lower switch, thereby removing the energy-consuming component while maintaining measurement capability
Solution Approach 2:
The patent introduces an intermediary approach where the voltage measurement across the semiconductor switch serves as a mediator to indirectly determine current flow. This allows current information to be obtained without directly passing current through measurement resistors, thus reducing power loss
2Measurement precision
If shunt resistors are used for current measurement, then current data is obtained, but heat generation increases
Solution Approach 1:
The patent removes shunt resistors from the circuit, which are the primary heat-generating components in current measurement systems. By using voltage measurement across the semiconductor switch instead, the system eliminates the source of excessive heat generation while maintaining current measurement accuracy
3Adaptability or versatility
If full-bridge configuration is used with semiconductor power control means, then motor control capability is achieved, but component count and cost increase
Solution Approach 1:
The patent makes the half-bridge configuration perform multiple functions: it provides motor control capability while simultaneously enabling current measurement through its inherent semiconductor switches. The lower switch in the half-bridge serves dual purposes as both a power control element and a current sensing point, eliminating the need for separate measurement components
Solution Approach 2:
The patent merges the power control function and current measurement function into a single integrated approach using the half-bridge configuration. The measurement of voltage across the lower semiconductor switch combines both the power switching operation and the current sensing operation, reducing overall system complexity
Data Source
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AI summary
A method for driving a three-phase BLDC motor with three-phase current supplies the motor with power by means of a power supply with the current. The power supply has semiconductor power control means being arranged in half-bridge configuration, and the motor control is connected to the power supply to perform the following steps. The current flowing is measured directly for each phase with respect to the positive waves from the current, and then the angle of rotation of the motor is determined. It is determined which of six equal rotation angle sectors with 60° each is present at current. Then the current of each phase is determined for each of the six rotation angle sectors, wherein the current I_phase of each phase is partly determined for at least one sector from a measured value for one of the phases alone, is partly determined for at least one sector from two measured values for two of the phases by subtraction and/or addition, and is partly determined for at least one sector by a trigonometrical function.