Induced Voltage Detector Circuit for Sensorless Motor Drive
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Solution Overview
Problem
Conventional induced voltage detector circuits for sensor-less motor control consume power due to current flowing through resistors and require expensive comparators or multiple A/D ports, leading to high costs and circuit complexity.
Innovation Solution
The proposed induced voltage detector circuit uses a level shift circuit and a circuit with a preset threshold voltage, eliminating the need for A/D ports and reducing power consumption by directly connecting to the motor drive inverter output terminals, and incorporating hysteresis to stabilize signal detection at low revolution velocities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional induced voltage detector circuits use resistors and comparators to detect induced voltage, then detection accuracy is improved, but power consumption increases and circuit cost becomes high
Solution Approach 1:
The patent extracts the essential detection function from complex comparator circuits and implements it using simple threshold voltage comparison. By removing unnecessary components (comparators, multiple resistors) and keeping only the essential threshold comparison mechanism, the circuit achieves induced voltage detection while dramatically reducing power consumption and component count.
Solution Approach 2:
The patent replaces expensive comparator circuits with inexpensive threshold voltage reference circuits that can be implemented using simple resistive dividers and diodes. This substitution uses cheaper components that consume minimal power while maintaining sufficient detection accuracy for the application.
2Measurement precision
If comparators are used in the induced voltage detector circuit, then detection capability is improved, but circuit scale becomes large and cost becomes high
Solution Approach 1:
The patent extracts the core detection functionality from complex comparator circuits and implements it through simple threshold voltage comparison using basic passive components. This extraction eliminates the need for large-scale integrated comparator circuits, reducing both circuit scale and cost while maintaining detection capability.
Solution Approach 2:
Instead of using active comparator circuits to detect voltage thresholds, the patent inverts the approach by using passive threshold voltage references and simple switching elements. This inversion transforms a complex active detection system into a simple passive reference system, dramatically reducing circuit scale.
3Ease of manufacture
If multiple A/D ports are used to detect induced voltage without comparators, then circuit cost is reduced, but control semiconductor device becomes expensive
Solution Approach 1:
The patent makes the control semiconductor device's A/D port multi-functional by using it both for normal control operations and for induced voltage detection. This universal usage eliminates the need for dedicated detection hardware, reducing overall system cost while maintaining the required detection capability through software-based processing of A/D port data.
4Ease of manufacture
If simple resistor division is used for voltage detection, then circuit cost is reduced, but noise immunity deteriorates
Solution Approach 1:
The patent applies beforehand cushioning by introducing hysteresis through feedback resistors connected to the switching element. This hysteresis mechanism pre-compensates for noise by creating a dead zone around the threshold voltage, preventing false triggering from noise while maintaining the simplicity and low cost of the overall circuit design.
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 solution reduces power consumption, lowers costs, enables induced voltage detection without A/D ports, and achieves high noise immunity while detecting voltages at low revolution velocities.
Implementation Method 1
The proposed induced voltage detector circuit uses a level shift circuit and a circuit with a preset threshold voltage
Implementation Method 2
incorporating hysteresis to stabilize signal detection at low revolution velocities
Data Source
Figure 1~2
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Figure 5~6
AI summary
An induced voltage detector circuit (9U, 9V) detects an induced voltage of a coil (8) of a motor, and converts an input voltage into an H/L signal to be output. A motor drive semiconductor device includes the induced voltage detector circuit (9U, 9V), switching elements (10) for inverter-driving the motor, and a drive circuit (7) for driving the switching elements.