PFM-PWM DC-DC converter providing DC offset correction to PWM error amplifier and equalizing regulated voltage conditions when transitioning between PFM and PWM modes
First Claim
1. A multi-mode DC-DC converter for supplying a regulated DC output voltage to a load comprising:
- an output power switching stage having upper and lower power switches coupled between an input voltage terminal and a reference voltage terminal and having a common node therebetween coupled by way of an output inductor to an output node from which said regulated DC output voltage is supplied;
a control circuit for controlling switching of said upper and lower power switches of said output power switching stage for respectively different modes of operation of said multi-mode DC-DC converter in accordance with respectively different switching control signals applied thereto;
a plurality of switching control signal generators, which are operative to generate said respectively different switching control signals, in response to which said control circuit controls switching of said upper and lower power switches of said output power switching stage during said respectively different modes of operation of said multi-mode DC-DC converter; and
a mode transition control circuit, coupled with said plurality of switching control signal generators, and being operative to prevent an anomaly in said DC output voltage at a transition between respectively different modes of operation of said multi-mode DC-DC converter.
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Accused Products
Abstract
To prevent a voltage glitch in the regulated DC output voltage of a PWM/PFM DC-DC converter when switching between PFM and PMW modes, the error amplifier of the converter'"'"'s PWM regulation path is provided with a DC voltage offset correction mechanism. This mechanism “zeros-out” DC voltage offsets that may be present in the voltage regulation path, thereby enabling the error amplifier to accurately regulate the converter'"'"'s output voltage. When the converter transitions between PFM and PWM modes, the DC offset correction mechanism establishes initial conditions of the error amplifier that effectively ensure that the converter'"'"'s regulated output voltage at the beginning of a new “switched-to” PWM mode cycle is DC offset-free.
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Citations
20 Claims
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1. A multi-mode DC-DC converter for supplying a regulated DC output voltage to a load comprising:
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an output power switching stage having upper and lower power switches coupled between an input voltage terminal and a reference voltage terminal and having a common node therebetween coupled by way of an output inductor to an output node from which said regulated DC output voltage is supplied; a control circuit for controlling switching of said upper and lower power switches of said output power switching stage for respectively different modes of operation of said multi-mode DC-DC converter in accordance with respectively different switching control signals applied thereto; a plurality of switching control signal generators, which are operative to generate said respectively different switching control signals, in response to which said control circuit controls switching of said upper and lower power switches of said output power switching stage during said respectively different modes of operation of said multi-mode DC-DC converter; and a mode transition control circuit, coupled with said plurality of switching control signal generators, and being operative to prevent an anomaly in said DC output voltage at a transition between respectively different modes of operation of said multi-mode DC-DC converter. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method of controlling the operation of a multi-mode DC-DC converter for supplying a regulated DC output voltage to a load, said multi-mode DC-DC converter including
an output power switching stage having upper and lower power switches coupled between an input voltage terminal and a reference voltage terminal and having a common node therebetween coupled by way of an output inductor to an output node from which said regulated DC output voltage is supplied, a control circuit for controlling switching of said upper and lower power switches of said output power switching stage for respectively different modes of operation of said multi-mode DC-DC converter in accordance with respectively different switching control signals applied thereto, and a plurality of switching control signal generators, which are operative to generate said respectively different switching control signals, in response to which said control circuit controls switching of said upper and lower power switches of said output power switching stage during said respectively different modes of operation of said multi-mode DC-DC converter, said method comprising the steps of: -
(a) monitoring an electrical parameter of one of said plurality of switching control signal generators; and (b) in the course of a transition between respectively different modes of operation of said converter, controlling the operation of said one of said plurality of switching control signal generators, in accordance with the electrical parameter monitored in step (a) so as to prevent an anomaly in said DC output voltage for said respectively different modes of operation of said converter. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19)
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20. For use with a pulse width modulation (PWM) mode to pulse frequency modulation (PFM) mode DC-DC converter for supplying a regulated DC output voltage to a load, said PWM mode to PFM mode DC-DC converter including
an output power switching stage having upper and lower power switches coupled between an input voltage terminal and a reference voltage terminal and having a common node therebetween coupled by way of an output inductor to an output node from which said regulated DC output voltage is supplied; -
a control circuit for controlling switching of said upper and lower power switches of said output power switching stage for said PWM and PFM modes of operation of said converter in accordance with respective PWM and PFM switching control signals applied thereto; and PWM and PFM switching control signal generators, which are operative to respectively generate PWM and PFM switching control signals, in response to which said control circuit controls switching of said upper and lower power switches of said output power switching stage during said PWM and PFM modes of operation of said converter, said PWM switching control signal generator including an error amplifier; the improvement comprising; a DC offset voltage correction circuit, that is coupled with said error amplifier, and is operative to place a DC offset correction voltage across said error amplifier at the time of said transition from PFM mode operation to PWM mode operation of said converter, that is effective to compensate for one or more DC offset voltages in a voltage regulation path of said PWM waveform generator.
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Specification