Multiple output voltages from a cascaded buck converter topology
First Claim
1. A circuit comprising:
- an input voltage terminal;
a first transistor having an input lead coupled to said input voltage terminal, a control lead, and an output lead coupled to a first node, said first transistor switchable to connect said input lead and said output lead in an on state and disconnect said input lead and said output lead in an off state;
a first inductive element disposed between said first node and a first output terminal;
a second transistor having an input lead coupled to said first node, a control lead, and an output lead coupled to a second node, said first transistor switchable to connect said input lead and said output lead in an on state and disconnect said input lead and said output lead in an off state;
a second inductive element disposed between said second node and a second output terminal;
a first current control device coupled between said second node and a common node, wherein current between said common node and said first inductive element is conducted through said first current control device when said first transistor is in said off state and current between said common node and said second inductive element is conducted through said first current control device when said second transistor is in said off state; and
a control circuit coupled to said control lead of said first transistor and to said control lead of said second transistor, wherein said control circuit turns said first and second transistors on and off.
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Abstract
A buck converter in accordance with the present invention provides multiple, well regulated, low voltage outputs. A cascaded buck converter comprises a main buck converter that is coupled to a subordinate buck converter through a cascade transistor in series with the free wheeling diode or transistor. The main buck converter is coupled to the free wheeling diode through the cascade transistor. Additional voltage outputs are possible by placing additional subordinate buck converters in series with the cascade transistor.
An isolated forward converter with multiple output voltages in accordance with the present invention may be derived using the cascaded buck converter topology. The cascading configuration permits multiple voltage outputs using a minimum number of switching devices while avoiding undesirable cross regulation.
133 Citations
14 Claims
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1. A circuit comprising:
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an input voltage terminal; a first transistor having an input lead coupled to said input voltage terminal, a control lead, and an output lead coupled to a first node, said first transistor switchable to connect said input lead and said output lead in an on state and disconnect said input lead and said output lead in an off state; a first inductive element disposed between said first node and a first output terminal; a second transistor having an input lead coupled to said first node, a control lead, and an output lead coupled to a second node, said first transistor switchable to connect said input lead and said output lead in an on state and disconnect said input lead and said output lead in an off state; a second inductive element disposed between said second node and a second output terminal; a first current control device coupled between said second node and a common node, wherein current between said common node and said first inductive element is conducted through said first current control device when said first transistor is in said off state and current between said common node and said second inductive element is conducted through said first current control device when said second transistor is in said off state; and a control circuit coupled to said control lead of said first transistor and to said control lead of said second transistor, wherein said control circuit turns said first and second transistors on and off. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of producing DC voltages, said method comprising;
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turning on a first transistor to couple a first inductive element to an input voltage; turning off a second transistor to permit a current carrying device to couple a second inductive element to a common node; turning on said second transistor while said first transistor is on to couple said second inductive element to said input voltage; turning off said first transistor to permit said current carrying device to couple said first inductive element to said common node; and controlling said first and said second transistors to produce a first regulated DC voltage across a first load coupled to said first inductive element, and to produce a second regulated DC voltage across a second load coupled to said second inductive element. - View Dependent Claims (12)
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13. A method of producing DC voltages, said method comprising:
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turning on a first transistor to charge a first inductive element with an input voltage; turning off a second transistor to discharge a second inductive element; turning on said second transistor while said first transistor is on to charge said second inductive element with said input voltage; turning off said first transistor while said second transistor remains on to discharge said first inductive element and said second inductive element; and controlling said first and said second transistors to produce a first regulated DC voltage across a first load coupled to said first inductive element, and to produce a second regulated DC voltage across a second load coupled to said second inductive element. - View Dependent Claims (14)
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Specification