Variable Voltage Converter Gate Driver Alternating PWM
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Solution Overview
Problem
Variable voltage converters in electric vehicles face inefficiencies due to the need for dead time in pulse width modulation to prevent cross-conduction, limiting duty cycles and voltage range.
Innovation Solution
A gate driver system that alternates pulse width modulation ON periods for switches in a variable voltage converter, allowing for the removal of dead time and enabling increased duty cycles by operating in traction or generator modes based on throughput magnitude, thereby reducing switching and heat losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dead time is used in pulse width modulation to prevent cross-conduction, then switch reliability is improved, but duty cycle range and voltage range are limited
Solution Approach 1:
The system dynamically switches between two PWM schemes based on operating conditions: using dead time PWM for cross-conduction prevention during bidirectional power flow, and zero dead time PWM for maximum duty cycle range during unidirectional power flow. This dynamic adaptation resolves the contradiction by adjusting the control strategy according to real-time operational requirements.
Solution Approach 2:
The invention changes the PWM control parameter (dead time duration) based on the operating mode. By detecting whether the variable voltage converter is operating in traction mode or generator mode, the system adjusts the PWM parameters accordingly - applying dead time when needed for reliability and eliminating dead time when maximizing duty cycle range is the priority.
2Reliability
If dead time is used in pulse width modulation, then cross-conduction is prevented, but switching losses and heat losses increase
Solution Approach 1:
The system changes the PWM parameter (dead time) based on operational mode detection. In traction mode where bidirectional power flow requires cross-conduction prevention, dead time is applied. In generator mode where power flow is unidirectional, dead time is eliminated, reducing switching losses and heat losses while maintaining reliability through alternative control strategies.
3Adaptability or versatility
If alternating pulse width modulation ON periods are used for traction and generator gates, then duty cycle range is increased to 95%, but control complexity increases
Solution Approach 1:
The control system is segmented into distinct operational modes (traction mode and generator mode) with dedicated PWM strategies for each. This segmentation allows the system to apply simplified control logic within each mode while achieving overall high duty cycle range capability, managing complexity through structured mode-based control architecture.
Solution Approach 2:
The system dynamically selects between different PWM control strategies based on the detected operating mode. This dynamic control approach enables the system to achieve 95% duty cycle range by alternating between traction-specific and generator-specific PWM schemes, managing control complexity through adaptive mode-based decision making.
4Loss of energy
If mode toggling is implemented based on throughput magnitude, then efficiency is enhanced, but control precision requirements increase
Solution Approach 1:
The system uses feedback from throughput magnitude measurements to dynamically determine the optimal operating mode. By continuously monitoring throughput and comparing it against threshold values, the control system adjusts the PWM strategy in real-time, enhancing energy efficiency while managing measurement precision requirements through threshold-based decision logic.
Data Source
AI summary
A vehicle power system may include a gate driver configured to drive a traction gate and a generator gate corresponding to switches of a variable voltage controller such that the gates have alternating pulse width modulation ON periods. The gates may be driven in response to a throughput magnitude falling below a threshold. The gate driver may be further configured to drive the gates such that a duty cycle of one of the gates is zero in response to the throughput exceeding the threshold.