DC/DC Converter Soft Switching With Predictive Frequency Control
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Solution Overview
Problem
High power electronic systems face significant energy losses during power conversion, particularly due to turn-on losses in switches used in high-frequency power converters, which are not efficiently addressed by existing technologies.
Innovation Solution
A variable-frequency explicit model predictive control and optimal-frequency model predictive control approach is implemented to achieve zero-voltage soft switching in DC/DC power converters, using a controller to vary the switching frequency based on inductor current and other parameters, thereby minimizing turn-on power losses and improving efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-frequency switching is used in power converters, then power conversion efficiency and power density are improved, but turn-on power losses increase significantly
Solution Approach 1:
The patent applies preliminary action by pre-charging the switch capacitor through a dedicated capacitor charging circuit before the switch turns on. This ensures that the capacitor voltage is already at the required level (equal to the input voltage) before switching occurs, eliminating the need for the switch to handle both voltage charging and power conversion simultaneously, thereby reducing turn-on losses while maintaining high-frequency operation
Solution Approach 2:
The patent segments the switching function into two separate circuits: a capacitor charging circuit that pre-charges the switch capacitor, and a power conversion circuit that performs the actual power conversion. This segmentation allows the switch to only handle current commutation without bearing the burden of capacitor charging, thus reducing turn-on power losses while maintaining high-frequency switching capability
2Speed
If wide band gap devices (SiC or GaN) are used, then high-frequency operation and low switching losses are achieved, but turn-on losses remain much higher than turn-off losses
Solution Approach 1:
The patent introduces an intermediary capacitor charging circuit that acts as a mediator between the input voltage source and the switch capacitor. This intermediary circuit pre-charges the capacitor through a separate path, allowing the main power switch to operate at high frequency with minimal turn-on losses, as the capacitor is already charged and ready for switching without requiring the switch to simultaneously handle voltage buildup
3Device complexity
If traditional PI controller is used, then control simplicity is maintained, but turn-on power losses during transient period cannot be eliminated
Solution Approach 1:
The patent applies preliminary action by implementing a capacitor charging circuit that operates continuously or anticipatorily to maintain the switch capacitor voltage at the required level before transient events occur. This preliminary charging action ensures that during transient periods, the switch can turn on without significant power losses because the capacitor is already charged, unlike traditional PI controllers that react after deviations occur
Data Source
AI summary
Disclosed are methods, systems, devices, and other implementations, including a voltage converter device that includes one or more inductive elements to deliver inductor current to an output section of the voltage converter device, at least one switching device to control current flow at the output section of the voltage converter device, and a controller to controllably vary, according to a predictive model, a subsequently applied switching frequency to the at least one switching device to maintain zero-voltage switching based, at least in part, on the inductor current of the one or more inductive elements.