Synchronous rectifier for boost converters
First Claim
1. A boost DC-DC converter circuit comprising:
- an input terminal for coupling to a voltage source;
an inductive energy storage element coupled to said input terminal;
a composite rectifier coupled to said inductive storage element, said composite rectifier comprising at least two opposite polarity transistors;
a switch coupled between ground and a node formed between said inductive storage element and said composite rectifier;
control circuitry coupled to said switch;
driver circuitry coupled to said composite rectifier; and
an output terminal coupled to said composite rectifier for coupling to a load.
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Accused Products
Abstract
A boost DC-DC converter with a synchronous composite rectifier is presented. The boost DC-DC converter limits inductive in-rush current, includes a shutdown mode, operates also in step-down mode, and can be fabricated using conventional bipolar processes. The composite rectifier includes a power NPN transistor and a lateral PNP transistor. During converter start-up and in step-down mode (when the output voltage is less than the input voltage), the lateral PNP transistor drives the power NPN transistor. The lateral PNP transistor is biased such that inductive volt-second balance can be maintained, limiting in-rush current. In boost mode (when the output voltage is higher than the input voltage), the lateral PNP transistor is disabled and the power transistor is driven into saturation. Again, inductive volt-second balance can be maintained.
34 Citations
18 Claims
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1. A boost DC-DC converter circuit comprising:
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an input terminal for coupling to a voltage source; an inductive energy storage element coupled to said input terminal; a composite rectifier coupled to said inductive storage element, said composite rectifier comprising at least two opposite polarity transistors; a switch coupled between ground and a node formed between said inductive storage element and said composite rectifier; control circuitry coupled to said switch; driver circuitry coupled to said composite rectifier; and an output terminal coupled to said composite rectifier for coupling to a load. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A method of limiting inductive in-rush current in a boost DC-DC converter, said converter comprising an output terminal for coupling to a load, an input terminal for coupling to a voltage source, an inductive storage element coupled between said input terminal and said output terminal, a switch coupled between ground and a node formed between said inductive storage element and said output terminal, and control circuitry coupled to said switch, said method comprising:
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providing a composite rectifier coupled between said node and said output terminal, said composite rectifier comprising; a power bipolar transistor, and a lateral bipolar driver transistor coupled to said power transistor, said power and driver transistors being of opposite polarity; monitoring voltages at said input terminal and said output terminal; biasing said composite rectifier such that said driver transistor is disabled and said power transistor is saturated when voltage at said output terminal is at least equal to voltage at said input terminal; and biasing said composite rectifier such that said driver transistor drives said power transistor when voltage at said output terminal is less than voltage at said input terminal, said power transistor operating outside saturation such that voltage across said composite rectifier is allowed to vary. - View Dependent Claims (17, 18)
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Specification