Forward-Flyback DC-DC Converter with LC Resonant Circuit
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Solution Overview
Problem
Existing DC-DC converter topologies, such as the active-clamped flyback converter, face challenges in achieving high efficiency above 94% due to difficulties in optimizing circuit structures for low cost and wide input voltage ranges.
Innovation Solution
The forward-flyback DC-DC converter topology incorporates a transformer, main switch, clamp circuit, rectifying switches, LC resonant circuit, and output capacitor, with specific winding configurations and switch control strategies to achieve zero-current and zero-voltage switching, reducing energy loss and selecting appropriate diodes for lower voltage ratings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If active-clamped flyback DC-DC converter topology is used, then low cost and wide input voltage range are achieved, but efficiency above 94% cannot be met
Solution Approach 1:
The patent divides the converter operation into two distinct modes: forward mode and flyback mode. The transformer secondary winding is segmented into two separate windings (forward winding and flyback winding), each optimized for its specific operating mode. This segmentation allows each mode to operate with optimized circuit parameters, achieving high efficiency in both modes while maintaining overall system performance above 94%.
Solution Approach 2:
The patent implements dynamic switching between forward and flyback modes based on real-time operating conditions. The control circuit dynamically adjusts the main switch and clamp switch states to transition between modes, optimizing efficiency across different input voltage ranges and load conditions. This dynamic operation enables the converter to maintain high efficiency (above 94%) across a wide input voltage range by adapting to changing conditions.
2Loss of energy
If forward-flyback DC-DC converter topology is used, then efficiency is improved, but circuit structure complexity increases
Solution Approach 1:
The patent designs the transformer with both forward and flyback windings that can operate in different modes, making the circuit topology multi-functional. The same basic circuit structure can operate in forward mode, flyback mode, or a combination of both, depending on the switching states. This universality allows the patent to achieve high efficiency across different operating conditions without requiring completely separate circuit designs for each mode, thereby limiting the increase in complexity.
Solution Approach 2:
The patent employs an active clamp circuit that automatically manages the transformer's leakage inductance and magnetizing inductance. The clamp switch and clamp capacitor work together to reset the transformer core and recover energy during both forward and flyback modes. This self-service mechanism reduces the need for additional complex control circuits and external components, achieving high efficiency while keeping the overall circuit structure manageable.
3Loss of energy
If zero-current switching is implemented, then efficiency is enhanced, but switch control complexity increases
Solution Approach 1:
The patent implements preliminary action by using the LC resonant circuit to prepare the current conditions before switching occurs. The resonant circuit pre-charges or pre-discharges capacitors and builds up current in inductors in advance of the switching event. This preliminary preparation ensures that when the main switch or rectifying switches turn on or off, the current is already at the desired level (zero or peak), enabling zero-current switching and minimizing switching losses without requiring complex real-time control adjustments.
Solution Approach 2:
The patent employs periodic resonant oscillations in the LC circuit to achieve zero-current switching at regular intervals. The resonant circuit naturally oscillates at its resonant frequency, creating periodic current waveforms that pass through zero at predictable points in the cycle. By synchronizing the switch timing with these periodic zero-crossing points, the patent achieves zero-current switching with simple timing control rather than complex real-time current sensing and adjustment circuits.
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 topology enhances efficiency by up to 3% compared to prior art, maintains high efficiency across varying loads, and allows for cost-effective implementation with suitable diode selection, making it suitable for high output voltage applications like the Super Charger.
Implementation Method 1
the LC resonant circuit being connected with the first output terminal, the second output terminal and an unlike terminal of the forward winding and the flyback winding so that the first and second rectifying switches implement zero-current switching
Implementation Method 2
A primary winding of the transformer and the main switch are connected in series between a first input terminal and a second input terminal
Data Source
AI summary
A forward-flyback DC-DC converter topology includes a transformer, a main switch, a clamp circuit, first and second rectifying switches, an LC resonant circuit and an output capacitor; a primary winding of the transformer and the main switch are connected in series between a first input terminal and a second input terminal, the clamp circuit constituted by a clamp capacitor and a clamp switch connected in series is connected in parallel with the primary winding or with the main switch, a secondary winding of the transformer includes a forward winding and a flyback winding, a terminal of the primary winding through which current flows into is a dotted terminal of the primary winding, and a connecting mode of a secondary side of the transformer is: the dotted terminal of the forward winding being connected with a first output terminal via the first rectifying switch, a dotted terminal of the flyback winding being connected with a second output terminal via the second rectifying switch, the LC resonant circuit being connected with the first and the second output terminals and an unlike terminal of the forward winding and the flyback winding so that the first and the second rectifying switches implement zero-current switching, and the output capacitor being connected between the first and the second output terminals.