Alon Cervera

A High-Efficiency Resonant Switched Capacitor Converter With Continuous Conversion Ratio

A resonant switched capacitor converter with high efficiency over a wide and continuous conversion ratio is introduced. The efficiency of the topology depends primarily on the conduction losses and is decoupled, to a large extent, from the voltage conversion ratio. This is an advantage over classical switched capacitor converters in which the efficiency is strongly related to the conversion ratio. The operation principle applies three zero current switching (ZCS) states to charge, discharge and balance the remaining charge of the flying capacitor. This results in a Gyrator-behaved voltage-dependent current source with a wide voltage conversion ratio (smaller as well as greater than unity) as well as bidirectional power flow capabilities. The analytical expressions for conversion ratio and expected efficiency are provided and validated by simulation and experiments. The experimental verification of the converter demonstrates peak efficiency of 96%, and above 90% efficiency over a wide range of voltage gains and loading conditions. In addition, the system was found to be highly efficient at the extreme cases of both light and heavy loads.

Enhanced Differential Power Processor for PV Systems: Resonant Switched-Capacitor Gyrator Converter With Local MPPT

This paper introduces an enhanced differential power processor topology and principle of operation for photovoltaic (PV) systems that is based on switched-capacitor technology, featuring local maximum power point tracking (MPPT) capability, zero current switching, high efficiency over wide-operation range, and reduced size. The new converter operates as a voltage-dependent current-source and is regulated by dead-time or frequency control. Local MPPT on the individual PV elements is realized and the operation is demonstrated by simulation and experiments. Differential power processing operation is verified using 150-W prototypes, demonstrating ultimate improvement in the power harvesting capability of above 90% and up to 99% out of the available power in the string, under different insolation levels.

Design and evaluation of a modular resonant switched capacitors equalizer for PV panels

A switched-capacitor based equalization scheme is proposed for overcoming the adverse effect of shaded panels in a serially connected PV array. The proposed solution is based on a modular approach, in which each two panels are connected to a resonant switched-capacitor converter. The distribution of currents and power extraction improvement have been derived and verified experimentally and design guidelines to meet desired power loss level requirements have been developed. The experimental equalizing module was designed for 185W PV panels and was found to boost the maximum available power by about 50% when interfaced with two serially connected PV panels under insolation ratios between 20% and 100%. The analytical, simulation and experimental results suggest that the proposed approach is effective in extracting all available power with relatively high efficiency.

Multiple Conversion Ratio Resonant Switched-Capacitor Converter With Active Zero Current Detection

This paper introduces an active method for zero current switching (ZCS) for resonant switched capacitor converters (SCC) with wide dynamic range. The method is demonstrated on a Binary SCC that features wide range of conversion ratios. Due to the resultant high efficiency of the converter operating under soft-switching conditions, it is applicable for higher power levels up to the medium power range (100W). The resonant operation is achieved with single air core inductor and precise commutation at zero current. The sensing signals of the resonant currents are obtained from the flying capacitors rather than form the inductive element in which the current includes a dc component. The zero detection method developed is capable of compensating for both the processing delays (from detection to switching action) and for the large variations of the resonant characteristics (due to transition between sub-circuits) and for any other component variations. A prototype with maximum input voltage of 100V and 19 conversion ratios was built and tested experimentally. The current sensing was implemented with a simple, cost-efficient, passive, sensor. For proper construction of the higher power experimental prototype, a simple and efficient, isolated gate driver was also developed.

Enhanced differential power processor for PV systems: Resonant switched-capacitor gyrator converter with local MPPT

This paper introduces an enhanced differential power processor topology and principle of operation for photovoltaic (PV) systems that is based on switched-capacitor technology, featuring local maximum power point tracking (MPPT) capability, zero current switching, high efficiency over wide-operation range, and reduced size. The new converter operates as a voltage-dependent current-source and is regulated by dead-time or frequency control. Local MPPT on the individual PV elements is realized and the operation is demonstrated by simulation and experiments. Differential power processing operation is verified using 150-W prototypes, demonstrating ultimate improvement in the power harvesting capability of above 90% and up to 99% out of the available power in the string, under different insolation levels.

A high efficiency resonant switched capacitor converter with continuous conversion ratio

A resonant switched capacitor converter with high efficiency over a wide and continuous conversion ratio range is introduced. The efficiency of the topology depends primarily on the conduction losses and is decoupled, to a large extent, from the voltage conversion ratio. This is an advantage over classical switched capacitor converters, for which the efficiency is strongly related to the conversion ratio. The operation principle applies three zero current switching states to charge, discharge, and balance the remaining charge of the flying capacitor. This results in a gyrator, i.e., a voltage-dependent current source, with a wide range of voltage conversion ratios (smaller as well as greater than unity) as well as bidirectional power flow capabilities. The analytical expressions for the conversion ratio and expected efficiency are provided and validated through simulations and experiments. The experimental verifications of the converter demonstrate peak efficiency of 96% and above 90% efficiency over a wide range of voltage gains and loading conditions. In addition, the system was found to be highly efficient at the extreme cases of both light and heavy loads.

Resonant Switched-Capacitor Voltage Regulator With Ideal Transient Response

A new, small and efficient voltage regulator, realized using a resonant switched-capacitor converter technology, is introduced. Voltage regulation is implemented by means of simple digital pulse density modulation. It displays an ideal transient response with a zero-order nature to all disturbance types. The newly developed topology acts as a gyrator with a wide range of voltage conversion ratios (below as well as above unity) with constant efficiency characteristics for the entire operation range. The operation of the voltage regulator is verified on a 20 W experimental prototype, demonstrating ideal transient recovery without over/undershoots in response to load and line transients. Simple design guidelines for the voltage regulation system are provided and verified by experiments.

Resonant switched-capacitor voltage regulator with ideal transient response

A new, small and efficient voltage regulator realized using a resonant switched capacitor converter (RSCC) technology is introduced. Voltage regulation is implemented by means of simple digital pulse density modulation (PDM). It displays an ideal transient response with a zero-order response to all disturbance types. The newly developed RSCC acts as a gyrator with a wide range of voltage conversion ratios (below as well as above unity) with constant efficiency characteristics for the entire operation range. The operation of the voltage regulator is verified on a 20W experimental prototype, demonstrating ideal transient recovery without over/undershoots in response to load and line transients. Simple design guidelines for the voltage regulation system are provided and verified by experiments.

Multiple conversion ratio resonant switched-capacitor converter with active zero current detection

This paper introduces an active method for zero current switching (ZCS) for resonant switched capacitor converters (SCC) with wide dynamic range. The method is demonstrated on a Binary SCC that features wide range of conversion ratios. Due to the resultant high efficiency of the converter operating under soft-switching conditions, it is applicable for higher power levels up to the medium power range (100W). The resonant operation is achieved with single air core inductor and precise commutation at zero current. The sensing signals of the resonant currents are obtained from the flying capacitors rather than form the inductive element in which the current includes a dc component. The zero detection method developed is capable of compensating for both the processing delays (from detection to switching action) and for the large variations of the resonant characteristics (due to transition between sub-circuits) and for any other component variations. A prototype with maximum input voltage of 100V and 19 conversion ratios was built and tested experimentally. The current sensing was implemented with a simple, cost-efficient, passive, sensor. For proper construction of the higher power experimental prototype, a simple and efficient, isolated gate driver was also developed.

Envelope tracking power supply for volume-sensitive low-power applications based on a resonant switched-capacitor converter

This paper introduces a new envelope tracking power supply to enhance the performance and reduce the overall volume of transmitter modules. The realization is based on a gyrator resonant switched-capacitor converter (GRSCC) that acts as a controlled bi-directional current source with a virtually instantaneous response to create the desired envelope. A quasi-non-casual control method is further applied to closely track high-rate signals without further increasing the switching frequency. The resultant dynamic performance for a given envelope reference signal is significantly improved, providing envelope supply voltage without clipping distortion. Design example and simulations are detailed, and the operation of envelope tracker is verified on a 150mW prototype switched at 2.3MHz, able to track a 1MHz envelope with less than half the losses of a linear regulator.