Phase-Shift DC-DC Converter Dead-Time Correction
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Solution Overview
Problem
DC-DC converters with phase-shift modulation and zero-voltage switching face challenges due to asymmetrical operation of bridge diagonals caused by power-supply disturbances and lack of symmetry in the driving stage, leading to potential transformer saturation.
Innovation Solution
A method that measures the direct current in the transformer to adjust the duty cycle of one diagonal relative to the other, by modifying the dead times of the driving signals to ensure symmetrical volt-seconds application, using a current sensor and controller module to calculate and apply correction values to the dead times, thereby maintaining average symmetry without requiring complex timing circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If phase-shift modulation with zero-voltage switching is used, then switching losses are reduced and efficiency is improved, but asymmetrical operation of bridge diagonals occurs due to power-supply disturbances and driving stage asymmetry
Solution Approach 1:
The patent employs a feedback mechanism where the DC current in the transformer is measured and used to adjust the duty cycle of one diagonal relative to the other. A controller module calculates correction values based on the measured current and applies them to the dead times of the driving signals, creating a closed-loop control system that actively compensates for asymmetries and maintains balanced operation.
Solution Approach 2:
The invention dynamically changes the dead time parameter of the driving signals to compensate for asymmetries. By measuring the DC current in the transformer and calculating appropriate correction values, the system adjusts the dead times of the bridge diagonals to maintain symmetrical volt-seconds application, thereby preventing transformer saturation while preserving the efficiency benefits of zero-voltage switching.
2Reliability
If dead time correction is applied to maintain symmetrical operation, then transformer saturation is prevented, but device complexity increases due to current sensing and control circuitry
Solution Approach 1:
The system uses the transformer's own DC current as the feedback signal for correction. By measuring the current that naturally flows in the transformer and using this information to adjust the driving signals, the system makes the transformer self-regulating, preventing saturation without requiring external intervention or complex additional control mechanisms.
Solution Approach 2:
The controller module performs multiple functions: it generates the basic phase-shift modulation signals, measures or receives the DC current information, calculates the correction values, and applies the dead time adjustments. This multi-functional approach consolidates control tasks into a single unit, reducing overall system complexity despite the added control capabilities.
3Device complexity
If standard driving circuits are used without correction, then device complexity is reduced, but asymmetrical operation leads to transformer saturation
Solution Approach 1:
The patent uses a current sensor and simple controller module that can be implemented with readily available, cost-effective components. Rather than requiring complex, expensive precision timing circuits, the invention employs affordable current sensing elements and standard control electronics that perform the necessary dead time corrections, achieving reliable transformer protection at low cost.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables symmetrical operation of the converter diagonals, preventing transformer saturation and allowing for the use of standard driving circuits, while emulating the effect of a capacitor in series without the associated costs and complexity.
Implementation Method 1
a resonant inductance 17, to provide for zero-voltage switching of each of the switch modules 13 of the bridge 12
Data Source
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AI summary
Described herein is a method of DC-DC conversion with phase-shift modulation and zero-voltage switching, which envisages supplying an input voltage (Vin) to an H-bridge of switches (12), a primary winding (15) of the transformer (14) and a series-connected resonant inductance (17) being connected between the legs of the bridge (12), the switches being turned on off according to an alternating sequence, the sequence comprising a dead time during which the switches are turned off. According to the invention, said method envisages making a measurement of the current (i(t)) that flows in the transformer (14), calculating a correction of the dead-time value as a function of said measurement of the current (i(t)) for cancelling out a difference of magnetic flux in the transformer generated by a first diagonal (13a, 13d) of the bridge (12) with respect to a second diagonal (13b, 13c) of the bridge (12).