Phase-Shifted Full Bridge Converter Dynamic Dead Time Control
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Solution Overview
Problem
Phase-shifted full bridge type DC/DC converters face reduced power conversion efficiency due to changes in resonance waveforms caused by variations in input and output magnitudes, and existing solutions either fail to effectively manage these changes or result in increased device size.
Innovation Solution
A switching power supply device with a phase-shifted full bridge type DC/DC converter that includes a power factor improvement circuit, output current and voltage detecting circuits, and a control unit dynamically adjusting dead times based on detected output current and voltage to optimize switching operations, using a data table to determine optimal dead times for Zero Voltage Switching (ZVS) control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If dead times are fixed at one fourth of resonance period, then ZVS control is simplified, but power conversion efficiency decreases when resonance waveform changes due to input/output variations
Solution Approach 1:
The patent implements dynamic dead time adjustment by measuring the actual resonance period through detection circuits and calculating optimal dead times based on detected waveform characteristics, allowing the system to adapt to input/output variations and maintain high efficiency across different operating conditions
Solution Approach 2:
The patent employs feedback mechanisms by detecting the actual resonance waveform and using this information to adjust dead times, creating a closed-loop control system that continuously optimizes performance based on real-time system state
2Loss of energy
If saturable choke coil is added to change inductance according to load, then unnecessary power loss is reduced, but device size increases
Solution Approach 1:
The patent extracts and eliminates the saturable choke coil from the system, replacing its function with a control method that adjusts dead times based on detected resonance waveforms, thereby reducing device size while maintaining the ability to optimize power loss across different load conditions
Solution Approach 2:
The patent replaces the mechanical/physical solution of using a saturable choke coil with an electronic control approach that uses detection circuits and control logic to achieve similar power loss reduction without adding physical components
3Loss of energy
If dead times are dynamically adjusted based on resonance waveform, then power conversion efficiency is maintained, but control complexity increases
Solution Approach 1:
The patent implements self-service control by having the system automatically detect its own resonance waveform and autonomously adjust dead times without external intervention, simplifying the user interface while maintaining sophisticated internal control
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 suppresses switching loss and achieves high power conversion efficiency while preventing the device from becoming overly large, even when resonance waveforms deviate from standard forms, and eliminates the need for a saturable choke coil.
Implementation Method 1
by controlling Zero Voltage Switching (ZVS), switching loss is reduced in the related art
Implementation Method 2
Dead times Td1 and Td2 are normally set to one fourth of a resonance period determined from inductance avid capacitance values included in a circuit to be opened and closed by switching elements Sa, Sb, Sc, and Sd. The inductance and the capacitance values for generating resonance are, for example, resonance inductor L and parasitic capacitance Cr of switching elements Sa, Sb, Sc, and Sd
Implementation Method 3
The inductance and the capacitance values for generating resonance are, for example, resonance inductor L and parasitic capacitance Cr of switching elements Sa, Sb, Sc, and Sd
Data Source
AI summary
A switching power supply device includes a power factor improvement circuit, a phase-shifted full bridge type DC/DC converter that is arranged in a rear stage of the power factor improvement circuit and has a full-bridge type switching circuit, an output current detecting circuit for detecting an output current to be supplied to a load, an output voltage detecting circuit for detecting an output voltage to be supplied to the load, and a power factor improvement circuit output voltage detecting circuit for detecting a power factor improvement circuit output voltage, which is input from the power factor improvement circuit to the DC/DC converter. The switching power supply device further includes a control unit for dynamically changing dead times of the full-bridge type switching circuit based on the power factor improvement circuit output voltage, and the output current and the output voltage to be supplied to the load, and the control unit applies the dead times that have been changed to control switching of the full-bridge type switching circuit.