Multi-Level DC-DC Converter
Multi-level DC-to-DC converter circuits and methods that permit a full range of output voltages, including near and at zone boundaries. Embodiments alternate among adjacent or near-by zones, operating in a first zone for a selected time and then in a second zone for a selected time. Embodiments may include a parallel capacitor voltage balancing circuit that connects a capacitor to a source voltage to charge that capacitor, or couples two or more capacitors together to transfer charge, all under the control of real-time capacitor voltage measurements. Embodiments may include a lossless voltage balancing solution where out-of-order state transitions are allowed, thus increasing or decreasing the voltage across specific capacitors to prevent voltage overstress on the converter main switches. Restrictions may be placed on the overall sequence of state transitions to reduce or avoid transition state toggling, allowing each capacitor an opportunity to have its voltage steered as necessary for balancing.
1 . A converter circuit for converting an input voltage to an output voltage, including:
(a) a multi-level converter circuit including:
(1) an inner pair of switches coupled in series;
(2) at least one inductor coupled to a node between the inner pair of switches;
(3) at least one outer pair of switches each coupled in series with the inner pair of switches wherein each outer pair of switches brackets the inner pair of switches; and
(4) at least one capacitor each coupled between a corresponding outer pair of switches and in parallel with the inner pair of switches;
(b) a switched resistance network including a plurality of series-coupled switch and resistance element pairs, all but one switch and resistance element pair being coupled in parallel with a corresponding switch of the outer pair of switches, with the remaining switch and resistance element pair being coupled in parallel with the inner pair of switches; and
(c) a directional correction circuit, coupled to the at least one capacitor and to the switched resistance network, configured to sense deviations in a voltage across at least one coupled capacitor and generate directional correction signals to the switched resistance network that, alone or in combination, dynamically change a pattern of charge or discharge states for the at least one coupled capacitor to selectively steer the voltage across the at least one coupled capacitor towards a balanced voltage state.