Drive Control Device PWM Pulse Period Adjustment
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Solution Overview
Problem
Existing drive control devices for inductive loads face challenges in suppressing overshoot and undershoot of mean current when frequency spreading of PWM pulses is implemented, leading to potential noise issues and prolonged stabilization times.
Innovation Solution
A drive control device that adjusts the periods of PWM pulses based on frequency command values, incorporating middle PWM pulses with intermediate lengths between forward and after PWM pulses to smoothly change the mean current while preventing rapid changes and overshoot or undershoot.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If frequency spreading of PWM pulse is performed to improve quietness, then audible sound is suppressed, but mean current overshoot or undershoot occurs at frequency switching moments
Solution Approach 1:
The patent applies preliminary action by inserting middle PWM pulses with intermediate frequencies between the forward PWM pulse (first frequency) and after PWM pulse (second frequency). This gradual frequency transition prevents sudden current changes that cause overshoot or undershoot, while still achieving frequency spreading for noise suppression. The middle pulses prepare the system for frequency switching in a controlled manner.
Solution Approach 2:
The patent changes the frequency parameter gradually through middle PWM pulses rather than making abrupt transitions. By introducing intermediate frequency values between the first and second frequencies, the system achieves smooth parameter transformation that maintains current stability while still implementing frequency spreading to reduce audible noise.
2Object-affected harmful factors
If frequency of PWM pulse is spread to improve quietness, then noise is reduced, but long period of time is required to stabilize current
Solution Approach 1:
The middle PWM pulses perform preliminary frequency adjustment, gradually transitioning the system from the first frequency to the second frequency. This staged approach allows current to adapt incrementally, achieving stabilization faster than direct frequency switching while still providing sufficient frequency spreading to reduce audible noise effectively.
Solution Approach 2:
The patent implements dynamic frequency adjustment by introducing middle PWM pulses that bridge the frequency gap. This dynamic transition approach allows the system to adapt to frequency changes more quickly, reducing stabilization time while maintaining the noise reduction benefits of frequency spreading.
3Object-affected harmful factors
If frequency command value is switched to spread PWM frequency, then quietness is improved, but mean current overshoot or undershoot occurs
Solution Approach 1:
The middle PWM pulses serve as a preliminary transition mechanism, gradually adjusting the frequency from the first command value to the second command value. This incremental frequency change prevents sudden current deviations, maintaining control precision while achieving the quietness improvement through frequency spreading.
Solution Approach 2:
The patent changes the frequency parameter in controlled steps using middle PWM pulses with intermediate frequencies. This staged parameter transformation maintains current control precision by avoiding abrupt changes, while still achieving sufficient frequency variation to improve quietness through spreading.
Data Source
AI summary
A drive control device includes: an input unit of a command; and a control unit setting a period for rising a current in an inductive load to first and third periods in first and second commands, and setting a period for falling the current to second and fourth periods in the first and second commands, respectively. When the first command is changed to the second command, and at least one middle PMW pulse is disposed between a forward PWM pulse corresponding to the first command and an after PWM pulse corresponding to the second command, the control unit sets fifth and sixth periods in the middle PWM pulse corresponding to the first and second periods of the forward PWM pulse to a length between the first and second periods in the forward PWM pulse and the third and fourth periods in the after PWM pulse, respectively.