The present embodiments relate to DC power conversion circuits. DC power conversion circuits generate a higher output voltage than the supply voltage. Three common DC power conversion circuits include boost converters, transformers, and charge pumps. Boost converters have a limited multiplication ratio due to parasitic resistances in the internal inductor. Multiple inductors in the boost configuration (“superboost”) may be used to limit the parasitic resistances. Transformers have switching-frequency limitations. Specially-designed, and thus expensive, custom transformers may be used to avoid switching-frequency limitations. Charge pumps have current limits based on the parasitic resistances in the internal capacitors. Multiple parallel capacitors may be used to reduce the current limits.
Some uses, such as in transmitter circuits for medical diagnostic ultrasound imaging or for high power car stereos, rely on a combination of a boost converter with charge pump as a transformerless switching regulator. Standard peak-current based controllers, which rely on a grounded sense resistor to measure current in the boost converter may not operate correctly with this combination because the charge pump current corrupts the sensed current. The combination is limited to those less common and more expensive circuits using current sensing in the supply path rather than the ground return.
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USPTO Backgrounds