Dual-Switch Flyback Converter High-Side Driving Circuit
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Solution Overview
Problem
Dual-switch flyback power converters face limitations in maximum duty cycle and high-side driving capability due to insufficient voltage levels in the high-side driving circuit, which can be exacerbated by the need for an auxiliary power supply, increasing costs.
Innovation Solution
The dual-switch flyback power converter employs a second transformer with an auxiliary winding and a floating winding to generate an auxiliary voltage and floating voltage, respectively, to power the control circuits and driving circuits, allowing for enhanced high-side driving capability and reduced cost by utilizing these voltages to power the high-side driving circuit and providing a floating ground reference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a charge pump circuit is used to power the high-side driving circuit, then the high-side driving circuit can be powered, but the maximum duty cycle is limited and the capacitor may be unable to be charged to maintain sufficient voltage level
Solution Approach 1:
The patent introduces a secondary transformer as an intermediary power supply system. The transformer includes a primary winding connected to the input voltage, a secondary winding for rectified power, and an auxiliary winding that generates a floating voltage. This intermediary transformer system resolves the contradiction by providing dedicated power for the high-side driving circuit through the auxiliary winding, eliminating the duty cycle limitations of charge pump circuits.
Solution Approach 2:
The power supply system is segmented into multiple independent windings on the transformer. The primary winding powers the main circuit, the secondary winding powers control circuits through rectification, and the auxiliary winding specifically powers the high-side driving circuit. This segmentation allows each winding to be optimized for its specific function, enabling full duty cycle operation without voltage level constraints.
2Power
If an auxiliary power supply is added to ensure sufficient voltage level, then the high-side driving capability is improved, but the system cost increases
Solution Approach 1:
The transformer is designed with multi-functionality, serving both as the main power transfer device and as the auxiliary power supply source. The auxiliary winding on the transformer generates the floating voltage needed for high-side driving without requiring a separate auxiliary power supply device. This universal design reduces system complexity and cost while ensuring sufficient high-side driving capability.
3Productivity
If the duty cycle of the switching signal is increased, then the power conversion efficiency is improved, but the capacitor cannot be charged to maintain sufficient voltage level
Solution Approach 1:
The auxiliary winding on the transformer preliminarily charges the capacitor connected to it during the transformer's operation. This preliminary charging action ensures that the capacitor maintains sufficient voltage level even when the main switching duty cycle is increased for improved efficiency. The auxiliary winding operates independently to maintain the voltage level without being constrained by the main duty cycle.
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 configuration ensures a sufficient high-side driving capability and reduces the cost of the dual-switch flyback power converter by utilizing the generated auxiliary and floating voltages, overcoming the limitations of duty cycle and driving capability while minimizing the need for external power supplies.
Implementation Method 1
A second switching signal generated by the second control circuit is utilized to switch the second transformer for generating an auxiliary voltage to power the first control circuit, the second control circuit, the high-side driving circuit, and the low-side driving circuit
Implementation Method 2
The second switching signal is further utilized to switch the second transformer for generating a floating voltage to power the high-side driving circuit
Implementation Method 3
The two diodes are coupled to the first transformer to circulate energy of a leakage inductance of the first transformer to an input power rail of the flyback power converter
Data Source
AI summary
A dual-switch flyback power converter includes a control circuit to generate a switching signal. A high-side driving circuit includes a pulse generation circuit. The pulse generation circuit generates a pulse-on signal and a pulse-off signal to control two transistors in response to the switching signal. The two transistors further respectively provide a level-shift-on signal and a level-shift-off signal to a comparison circuit to enable/disable a high-side driving signal. Without using a charge pump circuit to power the high-side driving circuit, a floating winding of a transformer is utilized to provide a floating voltage to power the high-side driving circuit, which reduces the cost of the dual-switch flyback power converter and ensures a sufficient high-side driving capability of the high-side driving circuit.