Self-Adjusting Current Injection for Soft Switching
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Solution Overview
Problem
Conventional DC-DC and AC-DC converters face challenges in achieving zero voltage switching across primary switches and zero current switching through rectifier means, often resulting in increased conduction losses and restricted input voltage and output current ranges, particularly in resonant and constant frequency pulse width modulation topologies.
Innovation Solution
The Rompower Current Injection Technology (RCIT) self-adjusts current injection amplitude to enable zero voltage and zero current switching in all topologies, both continuous and discontinuous modes, by using a current injection circuit with a controlled voltage source and unidirectional current injection switch, effectively converting hard switching converters into true soft switching converters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If resonant topologies shape current in half sinusoidal shape to achieve zero voltage switching, then switching efficiency improves, but frequency modulation becomes necessary which is not acceptable in some applications
Solution Approach 1:
The patent segments the switching control into two independent parts: frequency remains constant while the current injection timing and duration are modulated to achieve power control. This separates the frequency function from the power modulation function, allowing constant frequency operation with efficient switching.
Solution Approach 2:
The current injection circuit acts as an intermediary that enables zero voltage switching without requiring frequency modulation. It mediates between the constant frequency PWM controller and the primary switch, actively creating the conditions for soft switching while maintaining fixed frequency operation.
2Loss of energy
If conventional solutions are applied to specific topologies to achieve zero voltage switching, then switching losses are reduced, but device complexity increases and control becomes more complex
Solution Approach 1:
The current injection circuit is designed with universal applicability across multiple converter topologies (flyback, forward, push-pull, bridge). The same basic circuit architecture and control strategy work for different topologies, reducing the need for topology-specific complex control schemes and minimizing overall device complexity.
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
RCIT reduces control complexity, minimizes power dissipation, and increases efficiency, leading to higher power density by ensuring all switching elements turn on at zero voltage and current through rectifiers reaches zero before turn-off, regardless of operating conditions.
Implementation Method 1
a current injection reflected into the primary winding discharging a parasitic capacitance reflected across the primary switch
Data Source
AI summary
A method includes providing a transformer with primary and current injection windings, a primary switch connected to the primary winding, a parasitic capacitance reflected across the primary switch, a secondary rectifier means, and a current injection circuit including a current injection switch connected to the current injection winding, and a unidirectional current injection switch connected to the current injection winding. The method includes switching on the current injection switch to start a current injection flowing from a controlled voltage source, through the unidirectional current injection switch and further through the current injection winding. The current injection reflects into the primary winding, thereby discharging the parasitic capacitance reflected across the primary switch. The method includes turning on the primary switch with a delay time after the current injection switch turns on and turning off the current injection switch after the current injection reaches zero amplitude.