Switched-Capacitor Split Drive Transformer Power Conversion Architecture

 Technology

The invented power converter comprises a power distributor and inverter stage, coupled to a power combiner and rectifier stage through a split-drive transformer (SDT) stage which uses magnetic coupling to step up/down voltage and provide isolation between the distributor and combiner stages. The SDT structure architecture reduces transformer parasitic effects and absorbs the transformer parasitics into circuit operation. This ideally eliminates the effect of transformer parasitic components and enables the transformer to operate closer to their ideal transformer characteristics. Power combiner and rectifier receives the signals provided from SDT stage and combines the signals into an output provided to a load/source. The SDT architecture utilizes the transformer together with a circuit power stage (power distributor stage). Specifically, the power distributor and inverter stage has two functions: 1) to take the overall input power and voltage, condition it and distribute it to multiple paths to interface with the split-drive transformer stage, and 2) to maintain the variation of its outputs within a narrow (voltage) range even if its input has big variations. The SDT architecture combined with the circuit power stage acts to process the power in multiple voltage domains, and to compress the required operation range of each voltage domain, leading to a higher efficiency of the overall system.  

Problem Addressed

Traditionally, magnetic converter-based architectures with isolation such as forward converters or fly back converters transformers are widely used to reach high conversion ratios. They are simple, low-cost and easy to control. However, as the switching frequency is pushed higher, the converter timing becomes difficult, and the parasitic effects significantly increase the loss. Circuits using high-gain transformers or tapped inductors can provide desirable duty ratios and reduce device switching stress. However, the leakage inductance of the tapped inductor can ring with the parasitic capacitance of the switches, limiting its feasibility at high switching frequency. High-frequency-link architectures can reduce or eliminate this ringing problem by absorbing parasitics such as transformer leakage inductance into circuit operation. Such circuits can often realize soft switching and switch at a higher frequency than conventional hard-switched architectures. As the switching frequency increases, parasitics effects become larger, and associated proximity-effect currents induce more loss. To overcome these limitations, the proposed power conversion architecture incorporates advanced transformer structure design with a circuit power stage to enable the power converter to work efficiently over wide operating range.

Advantages

• Enable high conversion ratios over wide operating ranges (of voltages and powers)
• Reduces transformer parasitic effects and enables the transformer to operate closer to ideal transformer characteristics