Motor Drive Circuit Frequency Stability via Amplitude-Current Compensation
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Solution Overview
Problem
In motor drive circuits, varying oscillation voltage amplitudes lead to frequency changes in pulse signals, causing noise and potential motor driving issues due to frequencies entering the audible range.
Innovation Solution
A motor drive circuit with a triangle wave generation circuit that adjusts the charging/discharging current of a capacitor based on an amplitude control voltage, maintaining a constant oscillation voltage frequency and duty ratio of the pulse signal, independent of amplitude variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the amplitude of oscillation voltage is changed to match different speed control voltage ranges, then the oscillation voltage can be adapted to different microcomputer specifications, but the frequency of the oscillation voltage and pulse signal changes, causing noise and motor driving issues
Solution Approach 1:
The patent changes the parameter of charging/discharging current amount to compensate for amplitude changes. When oscillation voltage amplitude changes, the charging/discharging current is adjusted proportionally, which maintains a substantially constant pulse signal frequency despite amplitude variations, thereby preventing noise and ensuring reliable motor operation
Solution Approach 2:
The patent implements a feedback mechanism where the control voltage that adjusts oscillation amplitude also controls the charging/discharging current amount. This feedback loop ensures that when amplitude changes occur, the current is automatically adjusted to maintain stable pulse frequency, resolving the contradiction between adaptability and reliability
2Productivity
If the amplitude of oscillation voltage is increased to expand the speed control range, then the duty ratio control range is improved, but the pulse signal frequency enters the audible region causing noise
Solution Approach 1:
The patent simultaneously changes two parameters: oscillation voltage amplitude and charging/discharging current amount. By increasing the current proportionally with amplitude, the pulse frequency remains stable in the ultrasonic region, allowing expanded speed control range without generating audible noise
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
Prevents noise and ensures the motor can be driven at a consistent frequency, unaffected by oscillation voltage amplitude, thereby maintaining reliable motor operation.
Implementation Method 1
a triangle wave generation circuit configured to charge/discharge a capacitor with a charging/discharging current having a current amount according to an amplitude control voltage for controlling an amplitude of an oscillation voltage that varies in a triangle wave shape
Implementation Method 2
a pulse signal generation circuit configured to generate a pulse signal having a duty ratio corresponding to a level of a speed control voltage for controlling a rotational speed of a motor, based on a comparison result between the speed control voltage and the oscillation voltage
Data Source
AI summary
A motor drive circuit comprising: a triangle wave generation circuit configured to charge/discharge a capacitor with a charging/discharging current having a current amount corresponding to an amplitude control voltage for controlling an amplitude of an oscillation voltage that varies in a triangle wave shape, and to output a charging voltage of the capacitor as the oscillation voltage; a pulse signal generation circuit configured to generate a pulse signal having a duty ratio corresponding to a level of a speed control voltage for controlling a rotational speed of a motor, based on a comparison result between the speed control voltage and the oscillation voltage output from the triangle wave generation circuit; and a drive circuit configured to intermittently drive a motor coil based on the pulse signal.