Converter including a bootstrap circuit and method
First Claim
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1. A bootstrap circuit suitable for use in a converter, comprising:
- a low side transistor having a control terminal and first and second current carrying terminals;
a high side transistor having a control terminal and first and second current carrying terminals, the first current carrying terminal of the high side transistor coupled to the second current carrying terminal of the low side transistor to form a node;
a sense circuit having first, second, third, and fourth input terminals and an output terminal, the first input terminal of the sense circuit coupled to the node and the output terminal of the sense circuit configured to drive the control terminal of the low side transistor;
an energy storage element having a first terminal and a second terminal, the first terminal of the energy storage element directly connected to the first input terminal of the sense circuit and the second terminal of the energy storage element directly connected to the second input terminal of the sense circuit; and
a first logic gate having first and second input terminals and an output terminal, the first input terminal of the first logic gate coupled to the output terminal of the sense circuit, the second input terminal of the first logic gate coupled to the fourth input terminal of the sense circuit, and the output terminal of the first logic gate coupled to the control terminal of the high side transistor.
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Abstract
In accordance with an embodiment, a converter includes a circuit and method for charging a bootstrap capacitor. The circuit monitors a voltage across the bootstrap capacitor and enables charging the bootstrap capacitor in response to the voltage across the bootstrap capacitor being less than a threshold voltage.
17 Citations
20 Claims
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1. A bootstrap circuit suitable for use in a converter, comprising:
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a low side transistor having a control terminal and first and second current carrying terminals; a high side transistor having a control terminal and first and second current carrying terminals, the first current carrying terminal of the high side transistor coupled to the second current carrying terminal of the low side transistor to form a node; a sense circuit having first, second, third, and fourth input terminals and an output terminal, the first input terminal of the sense circuit coupled to the node and the output terminal of the sense circuit configured to drive the control terminal of the low side transistor; an energy storage element having a first terminal and a second terminal, the first terminal of the energy storage element directly connected to the first input terminal of the sense circuit and the second terminal of the energy storage element directly connected to the second input terminal of the sense circuit; and a first logic gate having first and second input terminals and an output terminal, the first input terminal of the first logic gate coupled to the output terminal of the sense circuit, the second input terminal of the first logic gate coupled to the fourth input terminal of the sense circuit, and the output terminal of the first logic gate coupled to the control terminal of the high side transistor. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A converter comprising:
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first and second transistors, each transistor of the first and second transistors having a control electrode and first and second current carrying electrodes, wherein the second current carrying electrode of the first transistor is directly coupled to the first current carrying electrode of the second transistor to form a node; a bootstrap circuit comprising; a sense circuit having first, second, third, and fourth input terminals and an output terminal, the first input terminal coupled to the node, the output terminal of the sense circuit coupled to the control terminal of the first transistor; and a first logic gate having first and second input terminals and an output terminal, the first input terminal of the first logic gate coupled to the output terminal of the sense circuit, the output terminal of the first logic gate coupled to the control terminal of the second transistor; and an energy storage element having a first terminal and a second terminal, the first terminal of the energy storage element directly connected to the first input terminal of the sense circuit and the second terminal of the energy storage element directly connected to the second input terminal of the sense circuit. - View Dependent Claims (8)
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9. A converter comprising:
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first and second transistors, each transistor of the first and second transistors having a control electrode and first and second current carrying electrodes, wherein the second current carrying electrode of the first transistor is coupled to the first current carrying electrode of the second transistor to form a first node; and a bootstrap circuit comprising; a sense circuit having first, second, third, and fourth input terminals and an output terminal, the first input terminal coupled to the node, wherein the sense circuit comprises; a sense amplifier having first and second input terminals and an output terminal; a comparator having first and second input terminals and an output terminal, the first input terminal of the comparator coupled to the output terminal of the sense amplifier; a second logic gate having first and second input terminals and an output terminal, the first input terminal of the second logic circuit coupled to the output terminal of the comparator; and a one shot having an input terminal and an output terminal, the input terminal coupled to the output terminal of the second logic gate and the output terminal of the one shot serving as the output terminal of the sense circuit; and a first logic gate having first and second input terminals and an output terminal, the first input terminal of the first logic gate coupled to the output terminal of the sense circuit; and an inverter coupled between the output terminal of the sense circuit and the first input terminal of the first logic gate. - View Dependent Claims (10, 11, 12, 13, 14, 15)
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16. A method for operating a converter, comprising:
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providing first and second transistors and an energy storage element, the first transistor having a control electrode and first and second current carrying electrodes and the second transistor having a control electrode and first and second current carrying electrodes, wherein the second current carrying electrode of the first transistor is directly coupled to the first current carrying electrode of the second transistor at a switching node, the energy storage element having a first terminal and a second terminal, the first terminal of the energy storage element directly connected to the switching node; providing a bootstrap circuit comprising; a sense circuit having first, second, third, and fourth input terminals and an output terminal, the first input terminal of the sense circuit directly coupled to the switching node and to the first terminal of the energy storage element, the second terminal of the sense circuit connected to the second terminal of the energy storage element, and the output terminal of the sense circuit coupled to the control electrode of the first transistor; and a first logic gate having first and second input terminals and an output terminal, the first input terminal of the first logic gate coupled to the output terminal of the sense circuit and the output terminal of the first logic gate coupled to the control electrode of the second transistor; sensing a signal across the energy storage element to generate a sense signal, the signal across the energy storage element at the first and second input terminals of the sense circuit; and in response to the sense signal being less than a reference level, turning on the second transistor and holding the first transistor in an off state, wherein a current flowing through the second transistor charges the energy storage element. - View Dependent Claims (17, 18, 19, 20)
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Specification