Phase-Shifted Full-Bridge Converter with Current Injection
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Solution Overview
Problem
Traditional phase-shifted full-bridge power converter topologies fail to achieve soft switching across secondary rectifiers, leading to voltage spikes and ringing, which negatively impact efficiency and require additional protective apparatus.
Innovation Solution
A pulse-shifted full-bridge DC-DC converter design with a transformer having leakage inductance between primary and secondary windings, featuring a bridge configuration with linear and resonant legs, synchronous rectifiers, and a current-injection circuit that ensures zero-voltage switching by discharging parasitic capacitance using magnetizing current and injection current, regardless of leakage inductance strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional phase-shifted full-bridge topology is used, then primary switching elements achieve zero voltage switching, but secondary rectifiers experience voltage spikes and ringing
Solution Approach 1:
The patent introduces a current injection circuit as an intermediary component that actively manages the current waveform. This circuit includes injection switches and current sources that superimpose additional current components onto the transformer secondary current, enabling the secondary rectifiers to turn off at zero current despite operating in continuous conduction mode. The intermediary circuit mediates between the traditional phase-shifted full-bridge operation and the desired soft switching condition for secondary devices.
Solution Approach 2:
The patent fundamentally changes the current parameter characteristics by injecting additional current components into the transformer secondary winding. By controlling the injection switches and current sources, the system modifies the instantaneous current waveform to ensure it reaches zero at specific moments when secondary rectifiers need to turn off, thereby achieving soft switching conditions through parameter manipulation rather than relying on natural discontinuous conduction.
2Reliability
If leakage inductance is increased to achieve soft switching, then zero voltage switching is obtained for primary switches, but converter complexity and component count increase
Solution Approach 1:
The current injection circuit serves as an intermediary that replaces the need for increased leakage inductance. Instead of relying on large leakage inductance values to naturally create soft switching conditions, the patent introduces active current injection components that directly enforce zero current turn-off for secondary rectifiers and zero voltage turn-on for primary switches, thereby achieving the same reliability benefit with different (and more controllable) means.
Solution Approach 2:
The patent substitutes the passive mechanical/electrical parameter approach (relying on fixed leakage inductance values) with an active control system. The current injection circuit uses controllable switches and current sources to dynamically shape the current waveform, replacing the static reliance on leakage inductance with an active control mechanism that can adapt to different operating conditions.
3Object-affected harmful factors
If additional protective apparatus (snubbers) are added to suppress voltage spikes, then secondary rectifier protection is improved, but device complexity and energy loss increase
Solution Approach 1:
The patent converts the potentially harmful voltage spikes and ringing into beneficial soft switching conditions. By using current injection to ensure zero current turn-off for secondary rectifiers, the natural current zero-crossing points are utilized to achieve lossless switching. This transforms what would normally be harmful transient phenomena into useful switching opportunities, eliminating the need for energy-dissipating snubber circuits.
Solution Approach 2:
The current injection circuit enables the converter to achieve soft switching through its own operational characteristics rather than requiring external protective components. The system uses its own current waveform, modified by the injection circuit, to naturally provide the zero current turn-off condition for secondary rectifiers, making the system self-sufficient for protection without additional energy-lossy components.
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
Guarantees zero-voltage switching for all switching elements, eliminating the need for minimum leakage inductance and reducing voltage spikes and ringing, thereby enhancing converter efficiency and reliability.
Implementation Method 1
a leakage inductance is formed between the at least one primary winding and at least one secondary winding
Implementation Method 2
using the energy in the leakage inductance to discharge the parasitic capacitance
Implementation Method 3
the charge of the parasitic capacitance across the secondary switching elements is effectuates with a current source
Implementation Method 4
the magnetizing current amplitude was increased in the transformer or in an inductor to form a virtual magnetizing current, in order to have enough energy in magnetizing current to discharge the parasitic capacitances
Implementation Method 5
turning on a current-injection switching element corresponding to a bottom switching element of the resonant leg with a time delay with respect to the moment of said switching off the upper switching element to reflect an injection current, flowing through said current-injection switching element, in a secondary winding
Data Source
AI summary
Systems and method for optimizing the efficiency of operation of electronic circuits, configured structured according to a true soft-switching phase-shifted full-bridge topology (where all the primary switching elements turn on at zero voltage and the secondary switching elements turn off at zero current with no ringing and no spikes across the secondary switching elements) with the use of unique current-injection approaches. An additional advantage of the embodiments of this invention is that the true soft switching feature applies regardless of the leakage inductance in the transformer.