Dual Path Hybrid DC-DC Converter with Flying Capacitors
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Solution Overview
Problem
Existing DC-DC converters face challenges in achieving high efficiency and power density, particularly in systems with high conversion rates, due to high inductance conduction losses and the need for additional flying capacitors, which complicates the control stage and increases passive element size.
Innovation Solution
A dual path hybrid DC-DC conversion circuit using two flying capacitors and a power inductor, where the switching state of the switches alternates to ensure that either the first or second flying capacitor and the power inductor supplies power to the output, effectively reducing the average inductance current and conduction loss by shunting the inductance current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a traditional hybrid DC-DC converter is used, then the system can achieve high conversion rate, but the average inductance current is equal to the load current causing high conduction loss
Solution Approach 1:
The patent divides the single inductance current path into two parallel paths by introducing two flying capacitors (CF1, CF2). The inductance current is segmented such that during different switching phases, the load current is supplied by either the inductance alone or the inductance combined with a flying capacitor, thereby reducing the average current through the inductance and reducing conduction loss while maintaining high conversion rate capability.
2Reliability
If additional flying capacitors are added to balance the circuit, then system reliability is improved, but device complexity increases
Solution Approach 1:
The patent implements a self-balancing mechanism where the two flying capacitors automatically equalize their voltages through their respective switching phases. During phase 1, CF1 charges while CF2 discharges, and during phase 2, the roles reverse. This self-service voltage balancing eliminates the need for additional balancing capacitors and complex control circuits, thereby improving reliability without significantly increasing device complexity.
3Quantity of substance
If smaller passive elements are used to miniaturize the product, then power density is improved, but manufacturing precision requirements increase
Solution Approach 1:
The two flying capacitors serve multiple functions simultaneously: they participate in voltage conversion, reduce inductance current, and self-balance their voltages. This multi-functionality allows the use of smaller capacitor values compared to traditional designs where capacitors would need to be larger for voltage ripple filtering alone, thereby improving power density without excessively stringent manufacturing precision requirements.
Data Source
AI summary
A direct current to direct current conversion circuit includes: an input end, a first flying capacitor, a second flying capacitor, a power inductor, a first state switch, a second state switch, and an output end; when the first state switch is turned on, and the second state switch is turned off, the input end, the first flying capacitor, the power inductor, the second flying capacitor and the output end are connected, the power inductor and the second flying capacitor supply power to the output end, and the first flying capacitor and the chip inductance are charged; and when the first state switch is turned off, and the second state switch is turned on, the first state flying capacitor, the power inductor, the second flying capacitor and the output are connected, the power inductor and the flying capacitor supply power to the output end, and the second flying capacitor is charged.