Current Determination Circuit for Motor Coil Noise Immunity
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Solution Overview
Problem
Existing current determination circuits for three-phase motors are prone to system noise interference, leading to inaccurate determination of coil current direction, especially when the voltage is between system high and low voltage, requiring additional circuits that increase costs and complexity.
Innovation Solution
A current determination circuit comprising high and low side transistors with body diodes and corresponding circuits that output determination signals based on voltage levels, processed by a processor to determine the state of the coil current, allowing for accurate determination without measuring voltages beyond system limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the voltage of the node is compared with the system high voltage or system low voltage for determining the direction of coil current, then the instant information of the motor in operation can be obtained, but the determination result is easily affected by system noise and requires auxiliary circuits that increase cost
Solution Approach 1:
The patent introduces body diodes connected to the transistors as intermediary elements. These body diodes serve as natural voltage clamps that automatically limit the node voltage to ranges comparable with system high and low voltages during the dead zone, eliminating the need for auxiliary measurement circuits while protecting against noise interference
Solution Approach 2:
The transistor body diodes inherently provide the voltage clamping function needed for accurate current direction determination. The system utilizes the existing body diodes of the power transistors for their original protection function, and simultaneously leverages their voltage-clamping effect to enable noise-resistant current sensing without adding separate measurement circuits
2Measurement precision
If the voltage of the node is compared with the system high voltage or system low voltage for determining the direction of coil current, then the instant information of the motor in operation can be obtained, but additional auxiliary circuits are required to measure voltages beyond system limits which increases cost
Solution Approach 1:
The body diodes act as natural voltage clamps that limit the node voltage to ranges comparable with system high and low voltages during the dead zone, eliminating the need for auxiliary measurement circuits while protecting against noise interference
Solution Approach 2:
The patent utilizes the existing body diodes of the power transistors, which are already present as protective elements, to serve the dual purpose of voltage clamping and current direction sensing. This eliminates the need for expensive auxiliary measurement circuits
3Adaptability or versatility
If the voltage of the node is between the system high voltage and system low voltage, then the voltage comparison method can operate, but the direction of coil current usually cannot be determined
Solution Approach 1:
The body diodes serve as natural voltage clamps that automatically limit the node voltage to ranges comparable with system high and low voltages during the dead zone, ensuring the voltage always falls within detectable ranges while maintaining accurate current direction determination
Solution Approach 2:
The patent changes the voltage range parameter by utilizing the dead zone period when both transistors are off, during which the body diodes clamp the voltage to specific ranges. This parameter change enables reliable current direction determination that is not affected by intermediate voltage states
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 circuit effectively determines the state of the coil current in the dead zone, avoiding noise interference and unnecessary cost, and enables optimal motor operation by adjusting phase relationships, thus improving motor efficiency and reducing operational complexity.
Implementation Method 1
The high side transistor includes a first body diode, and the low side transistor includes a second body diode. The high side circuit is coupled to the high side transistor and is configured to output a first determination signal according to a first voltage between two ends of the first body diode
Data Source
AI summary
A current determination circuit is configured to determine a state of current passing through a coil of a motor and includes a high side circuit, a low side circuit and a processor. The high side circuit is configured to output a first determination signal according to a first voltage between two ends of a first body diode of a high side transistor and the voltage level of a first control signal. The low side circuit is configured to output a second determination signal according to a second voltage between two ends of a second body diode of a low side transistor and the voltage level of a second control signal. The processor is configured to receive the first determination signal and the second determination signal and determine the state of current according to the voltage level of the first determination signal and the voltage level of the second determination signal.