PWM Activation Pulse Shifting for Minimum Pulse Width Limits
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Solution Overview
Problem
Existing pulse width modulation (PWM) activation methods for semiconductor switching elements in electrical power converters are limited by a minimum pulse width requirement, restricting the duty cycle range and causing inefficiencies when transitioning between different duty cycles.
Innovation Solution
A device and method that generate activation signals with shifted or extended pulses within the pulse period to comply with the minimum pulse width requirement, allowing PWM operation over a wider range of duty cycles and smooth transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a minimum pulse width is enforced between switching operations, then switching element reliability is improved, but the duty cycle range is restricted and cannot reach 0 to 100 percent
Solution Approach 1:
The patent applies dynamics by making the pulse positioning flexible rather than fixed. The pulse position within the PWM period is dynamically adjusted based on the duty cycle value. When duty cycle is low, pulses are centered; when duty cycle increases and approaches the minimum pulse width constraint, pulses are shifted toward the beginning or end of the period. This dynamic repositioning allows the system to maintain reliable switching (minimum pulse width enforced) while adapting to the full 0-100% duty cycle range.
Solution Approach 2:
The patent changes the temporal parameter of pulse positioning within the PWM period. Instead of maintaining a fixed centered pulse position, the system varies the pulse start and end times based on the duty cycle value. This parameter change allows pulses to be repositioned within the period to satisfy the minimum pulse width requirement while achieving any desired duty cycle from 0 to 100%, thus resolving the contradiction between reliability and adaptability.
2Ease of manufacture
If centered pulses are used for PWM activation, then simplicity of implementation is improved, but transition smoothness between duty cycles deteriorates when minimum pulse width is approached
Solution Approach 1:
The system transitions from static centered pulse generation to dynamic pulse positioning. The pulse position is continuously adjusted based on the duty cycle value and minimum pulse width constraints. This dynamic approach ensures smooth transitions between duty cycles by preventing abrupt changes that would occur with fixed centered pulses when the minimum pulse width limit is approached.
Solution Approach 2:
The patent applies preliminary anti-action by proactively adjusting pulse positions before the minimum pulse width constraint is violated. The system calculates the appropriate pulse positioning in advance based on the duty cycle value, preventing the situation where centered pulses would result in insufficient pulse width. This anticipatory adjustment ensures continuous smooth operation without abrupt transitions or violations of switching constraints.
Data Source
AI summary
The invention comprises forming activation pulses for a pulse width modulated activation. In this case, instead of centered pulses, pulses can be formed that are shifted to the edge of a pulse period. In this way, the requirements for a minimum pulse width between two switching operations may be better complied with.