Motor Drive Gain Control for Hall Signal Quality Without Power Loss
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing motor driving apparatus experiences power efficiency decline due to power loss caused by detection resistors, which also leads to a decrease in Signal-to-Noise (S/N) ratio of the negative feedback voltage, especially in large motor applications like vehicle motors or household appliance motors.
Innovation Solution
A motor driving apparatus with an automatic gain control circuit that includes an amplifier and a feedback control portion to monitor and adjust the gain, using a monitoring signal and rectifier to maintain signal quality without reducing power efficiency or noise immunity, and incorporating a phase adjustment circuit and overcurrent detection for enhanced control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a detection resistor is used to generate negative feedback voltage for automatic gain control, then the gain control function is achieved, but power loss increases and power efficiency declines
Solution Approach 1:
The patent extracts the detection function from the power path by using a separate detection resistor connected to the neutral point, rather than placing the detection resistor in the main power current path. This allows the detection of total motor driving current without causing power loss in the detection resistor, as the detection current is minimal compared to the motor driving current.
Solution Approach 2:
The patent introduces the neutral point as an intermediary measurement point. By connecting the detection resistor between the neutral point and ground, the system can detect the total motor driving current indirectly through the neutral point voltage, avoiding the need to place the detection resistor in the direct power path where it would cause significant power loss.
2Loss of energy
If the resistance of the detection resistor is reduced to minimize power loss, then power efficiency improves, but the Signal-to-Noise ratio of the negative feedback voltage deteriorates
Solution Approach 1:
The patent creates a copy of the detection function by using the neutral point voltage as a proxy for the total motor driving current. Instead of directly measuring the large motor current through a low-value resistor (which would have poor S/N ratio), the system measures the neutral point voltage which represents the same information with much better signal characteristics.
3Loss of energy
If a detection resistor with small resistance is used, then power loss is reduced, but the S/N ratio of the negative feedback voltage becomes insufficient for large motor applications
Solution Approach 1:
The patent transitions from measuring current directly in the power path (one dimension) to measuring voltage at the neutral point (another dimension). This dimensional change allows the system to obtain the same control information with superior signal quality, as the neutral point voltage provides a high-impedance measurement point that doesn't load the power circuit.
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 automatic gain control on rotor-position detecting signals without compromising power efficiency or noise immunity, effectively managing large motor driving currents and improving motor performance.
Implementation Method 1
an amplifier, for amplifying an input signal to generate an output signal
Implementation Method 2
a rectifier, for rectifying the monitoring signal to generate a rectified monitoring signal
Data Source
AI summary
A motor driving apparatus includes an automatic gain control circuit on a signal path for transmitting a rotor-position detecting signal (hall voltage signal), and the automatic gain control circuit includes: an amplifier, configured to perform differential amplification on an input signal (step-angle hall current signal) to generate an output signal (amplified hall current signal); and a feedback control portion, configured to monitor the output signal (monitored current signal) to decide a gain of the amplifier.