Hybrid DC-DC converter
View Patent ↗A DC-DC converter suitable for conversion of high input voltages to regulated low output voltages at very high output currents has a cascade of stages including a buck regulation stage, an unregulated switched capacitor voltage doubler, and an unregulated voltage isolation stage. These three stages are merged in a single switching structure so that each stage optimally performs its respective function while also taking advantage of characteristics and features of neighboring stages.
1. A hybrid DC-DC converter comprising cascaded first, second and third stages and regulation feedback circuitry coupled between an output of the DC-DC converter and a control input of the first stage for overall regulation of the DC-DC converter, the first stage being a switched inductance stage generating a first intermediate DC voltage from an input DC voltage, the second stage being an unregulated switched capacitance stage generating a second intermediate DC voltage as a predetermined multiple of the first intermediate DC voltage, and the third stage being an isolation stage providing the output of the DC-DC converter from the second intermediate DC voltage, the first stage operating in response to a pulse width modulation signal at the control input, provided by the regulation feedback circuitry, to generate the first intermediate DC voltage so as to achieve the overall regulation of the DC-DC converter.
2. The hybrid DC-DC converter of claim 1 , wherein the switched inductance stage employs a regulating buck converter circuit.
3. The hybrid DC-DC converter of claim 2 , wherein the regulating buck converter circuit is operated at a duty cycle in a range of 0.25 to 0.8.
4. The hybrid DC-DC converter of claim 2 , wherein the regulating buck converter circuit includes a plurality of buck converters connected and operated in interleaved fashion for higher power and improved regulation and transient response.
5. The hybrid DC-DC converter of claim 1 , wherein the unregulated switched capacitance stage is realized as a switched capacitor voltage doubler having a ladder topology and a set of switches configured as series stacked half bridge switching cells, the switches being operated out of phase and at fixed 50% duty cycle to obtain a voltage doubling effect.
6. The hybrid DC-DC converter of claim 1 , wherein the unregulated switched capacitance stage is realized as a switched capacitor voltage doubler employing resonant and soft-switching to realize voltage doubling with zero-current switching of the switches.
7. The hybrid DC-DC converter of claim 1 , wherein the unregulated switched capacitance stage is realized as a switched capacitor voltage doubler having elements that are common to both the switched inductance stage and to the isolation stage, including a common capacitor serving as both an input capacitor for the unregulated switched capacitance stage and as an output capacitor for the switched inductance stage, and including voltage divider circuitry shared by both the unregulated switched capacitance stage and the isolation stage.
8. The hybrid DC-DC converter of claim 7 , wherein the switched capacitor voltage doubler includes switched capacitor stacked half bridge switching cells operating synchronously with their mid-points at exactly one half of a circuit total voltage.
9. The hybrid DC-DC converter of claim 8 , including a dual primary, single secondary transformer having two primary windings connected in series.
10. The hybrid DC-DC converter of claim 9 , employing a matrix configuration with either multiple magnetic paths on a single transformer core or a distributed core configuration using multiple cores.
11. The hybrid DC-DC converter of claim 1 , having a hybrid full-bridge topology merging a zero-current-switching voltage doubler with a full bridge isolation stage to provide for resonant zero-current-switching operation of all switches along with zero-voltage switching of primary-side switches and soft charging of a flying capacitor.
12. The hybrid DC-DC converter of claim 1 , wherein additional switches of a full bridge converter are merged with a switched capacitor circuit branch to add power capability and interleaved operation of the voltage doubler stage.
13. The hybrid DC-DC converter of claim 1 , wherein the isolation stage is realized as a DC transformer.