Comparator for synchronous rectification and method of operation
First Claim
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1. A boost converter, comprising:
- a comparator having;
a first and second N-channel transistors, a source of the first and second N-channel transistors coupled to ground, a drain of the first and second N-channel transistors coupled to a respective control gate of the first and second N-channel transistors;
a switch connected between the drain and the control gate of the second N-channel transistor and operated by a N-gate signal,a first P-channel transistor having a drain coupled to the drain of the second N-channel transistor and a source coupled to a drain of a third P-channel transistor and a drain of a fourth P-channel transistor,the third P-channel transistor includes a control gate coupled to a complimentary N-gate signal, and a source coupled to an output voltage of the converter,the fourth P-channel transistor includes a control gate coupled to a P-gate signal, and a source coupled to a coil voltage,a second P-channel transistor having a drain coupled to the drain of the first N-channel transistor and a source coupled to a drain of a fifth P-channel transistor and a drain of a sixth P-channel transistor,the fifth P-channel transistor includes a control gate coupled to the P-gate signal, and a source coupled to the VOUT of the converter, andthe sixth P-channel transistor includes a control gate coupled to the complimentary N-gate signal, and a source coupled to the VOUT of the converter.
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Abstract
A boost converter includes a comparator having first and second gain stages that operate in compare and auto-zero modes. The comparator measures voltage drop across a P-channel transistor to determine when current through an inductor reaches zero. When the inductor current reaches zero, the P-channel transistor becomes inactive to prevent a reduction in efficiency caused by allowing negative inductor current to draw current from a load. The comparator is then placed in a low power state. When the comparator is not in a compare mode, the comparator can operate in an auto-zero mode to cancel offset when measuring the input of the comparator.
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Citations
20 Claims
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1. A boost converter, comprising:
a comparator having; a first and second N-channel transistors, a source of the first and second N-channel transistors coupled to ground, a drain of the first and second N-channel transistors coupled to a respective control gate of the first and second N-channel transistors; a switch connected between the drain and the control gate of the second N-channel transistor and operated by a N-gate signal, a first P-channel transistor having a drain coupled to the drain of the second N-channel transistor and a source coupled to a drain of a third P-channel transistor and a drain of a fourth P-channel transistor, the third P-channel transistor includes a control gate coupled to a complimentary N-gate signal, and a source coupled to an output voltage of the converter, the fourth P-channel transistor includes a control gate coupled to a P-gate signal, and a source coupled to a coil voltage, a second P-channel transistor having a drain coupled to the drain of the first N-channel transistor and a source coupled to a drain of a fifth P-channel transistor and a drain of a sixth P-channel transistor, the fifth P-channel transistor includes a control gate coupled to the P-gate signal, and a source coupled to the VOUT of the converter, and the sixth P-channel transistor includes a control gate coupled to the complimentary N-gate signal, and a source coupled to the VOUT of the converter. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A DC-DC boost converter comprising:
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an inductor having a first terminal coupled to a coil voltage; a capacitor having a first terminal coupled to a second terminal of a switch and a second terminal coupled to ground; a comparator having a first input coupled to the coil voltage and a second input coupled to ground, the comparator including; a first diode-connected N-channel transistor; a second diode-connected N-channel transistor having a switch coupled between a drain and a control gate; a capacitor having a first terminal coupled to a control gate of the first diode-connected N-channel transistor and a second terminal coupled to the control gate of the second diode-connected N-channel transistor; a first P-channel transistor having a drain coupled to a drain of the second diode-connected N-channel transistor; a third P-channel transistor having a drain coupled to a source of the first P-channel transistor, a control gate coupled to a complementary N-gate signal and a source coupled to an output voltage of the converter; a fourth P-channel transistor having a control gate coupled to a P-gate signal, a drain coupled to the source of the first P-channel transistor and a source coupled to the coil voltage; a second P-channel transistor having a drain coupled to a drain of the second diode-connected N-channel transistor and a control gate coupled to a control gate of the first P-channel transistor; a fifth P-channel transistor having a control gate coupled to the P-gate signal, a drain coupled to a source of the second P-channel transistor and a source coupled to the VOUT; a sixth P-channel transistor having a drain coupled to the source of the second P-channel transistor, a control gate coupled to a complementary N-gate signal and a source coupled to the VOUT. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification