PWM Control Method for Multiple Electrical Loads
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Solution Overview
Problem
Conventional pulse-width modulation (PWM) control of multiple electrical loads results in significant jumps in the number of loads switched on or off at a given time, leading to steep changes in current profiles, which can cause electromagnetic compatibility issues and component overload or damage.
Innovation Solution
A method where each consumer is switched on or off within a duty cycle for a continuous period, with switch-on and switch-off times selected to minimize the difference between the number of switch-on and switch-off processes, ensuring that only one consumer is switched at a time, and if multiple are switched, they are done so simultaneously to maintain a flat current profile.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional PWM control switches all consumers on at the beginning of the duty cycle, then the control is simple and straightforward, but the number of consumers switched on simultaneously causes steep current increases and electromagnetic compatibility issues
Solution Approach 1:
The duty cycle is divided into multiple sub-intervals, and consumers are segmented into different switching groups. Each group is switched on at different time points within the duty cycle rather than all at once, which segments the current draw and avoids steep current increases while maintaining control simplicity.
2Object-affected harmful factors
If consumers are switched on at different times within the duty cycle, then the current profile becomes smoother, but the control complexity increases significantly
Solution Approach 1:
The patent applies partial action by switching on only a subset of consumers at each time point within the duty cycle, rather than switching all consumers simultaneously or using complex staggered switching for all consumers. This partial switching approach achieves sufficient current smoothing without requiring excessive control complexity.
3Reliability
If the switching times are optimized to minimize current spikes, then electromagnetic compatibility is maintained, but the control algorithm becomes more complex
Solution Approach 1:
The switching times for different consumer groups are predetermined and pre-planned within the duty cycle structure. By preliminarily arranging which consumers switch on at which time points, the system achieves electromagnetic compatibility without requiring complex real-time decision algorithms during operation.
Data Source
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AI summary
The present invention relates to a method for pulse-width modulated control of several electrical loads, comprising that each load is switched on or off during a duty cycle (14) according to a predetermined duty cycle for a continuous period (26) and that the switching-on (28) and switching-off times (30) of loads whose duty cycle for the respective duty cycle is neither 0 nor 1 are selected within the duty cycle depending on the duty cycles of all loads such that at every time the amount of the difference between the number of switching-on events (28) and the number of switching-off events (30) is minimal.