Synchronous rectifier circuit and method of use in switching voltage converter

A synchronous rectifier circuit comprising:

• (a) a comparator having a first input coupled to a first conductor and a second input coupled to a reference voltage conductor, the first conductor conducting a current that also flows through an inductor;
• (b) a logic circuit having an input coupled to an output of the comparator, a first output, and a second output;
• and
• (c) a first transistor having a gate coupled to the first output, a source coupled to the reference voltage conductor, and a drain coupled to the first conductor, and a second transistor having a gate coupled to the second output, a source coupled to the reference voltage conductor, and a drain coupled to the first conductor.

A synchronous rectifier circuit comprising:

• (a) a comparator having a first input coupled to a first conductor and a second input coupled to a reference voltage conductor, the first conductor conducting a current that also flows through an inductor;
• (b) a logic circuit having an input coupled to an output of the comparator, a first output, and a second output;
• and
• (c) a first transistor section having a gate coupled to the first output, a source coupled to the reference voltage conductor, and a drain coupled to the first conductor, and a second transistor section having a gate coupled to the second output, a source coupled to the reference voltage conductor, and a drain coupled to the first conductor.

A signal conversion circuit comprising:

• (a) a first transistor having a drain connected to receive an unregulated input voltage, a gate connected to receive a feedback control signal, and a source connected to a first conductor;
• (b) an inductor having a first terminal coupled to the first conductor and a second terminal connected to produce a regulated output voltage on an output conductor;
• (c) a feedback control circuit coupled between the gate of the first transistor and the output conductor for regulating switching of the first transistor in response to the regulated output voltage;
• (d) an synchronous rectifier circuit including
• i. a comparator having a first input coupled to the first conductor and a second input coupled to the reference voltage conductor,
• ii. a logic circuit having an input coupled to an output of the comparator, a first output, and a second output,
• iii. a first transistor section having a gate coupled to the first output, a source coupled to the reference voltage conductor, and a drain coupled to the first conductor and a second transistor section having a gate coupled to the second output, a source coupled to the reference voltage conductor, and a drain coupled to the first conductor, the body diode having a cathode coupled to the first conductor and an anode coupled to the ground conductor.

A signal conversion circuit comprising:

• (a) a first transistor having a source connected to the reference voltage conductor, a gate connected to receive a feedback control signal, and a drain connected to a first conductor;
• (b) an inductor having a first terminal coupled to an input receiving an unregulated input voltage and a second terminal connected the first conductor;
• (c) a feedback control circuit coupled between the gate of the first transistor and an output conductor for regulating switching of the first transistor in response to a regulated output voltage;
• and
• (d) a synchronous rectifier circuit including
• i. a comparator having a first input coupled to the first conductor and a second input coupled to the output conductor,
• ii. a logic circuit having an input coupled to an output of the comparator, a first output, and a second output, and
• iii. a first transistor having a gate coupled to the first output, a drain coupled to the output conductor, and a source coupled to the first conductor and a second transistor having a gate coupled to the second output, a drain coupled to the output conductor, and a source coupled to the first conductor.

A voltage converter circuit comprising:

• (a) a first transistor having a drain connected to receive an unregulated input voltage, a gate connected to receive a feedback control signal, and a source connected to a first conductor;
• (b) an inductor having a first terminal coupled to the first conductor and a second terminal connected to produce a regulated output voltage on an output conductor;
• (c) a feedback control circuit coupled between the gate of the first transistor and the output conductor for regulating switching of the first transistor in response to the regulated output voltage;
• (d) a synchronous rectifier circuit including
• i. a comparator having a first input coupled to the first conductor and a second input coupled to the reference voltage conductor,
• ii. a logic circuit having an input coupled to an output of the comparator, a first output, and a second output,
• iii. a second transistor having a gate coupled to the first output, a source coupled to the reference voltage conductor, and a drain coupled to the first conductor, and
• iv. a third transistor having a gate coupled to the second output, a source coupled to the reference voltage conductor, and a drain coupled to the first conductor.

A method of providing synchronous switching of a current flowing through an inductor and a first conductor, comprising:

• (a) providing a comparator having a first input coupled to the first conductor and a second input coupled to a reference voltage conductor, and providing a logic circuit having an input coupled to an output of the comparator, a first output, and a second output;
• (b) operating the comparator to produce a “1” level in response to a change of voltage of the first conductor caused by the flow of the current;
• and
• (c) operating the logic circuit in response to the “1” level to turn on both a first transistor and a second transistor in response to a first switching of the comparator to a “1” level, and to turn off only the first transistor in response to a second switching of the comparator to the “1” level, and to turn off the second transistor in response to a third switching of the comparator to the “1” level, the first transistor having a gate coupled to the first output, a source coupled to the reference voltage conductor, and a drain coupled to the first conductor, and the second transistor having a gate coupled to the second output, a source coupled to the reference voltage conductor, and a drain coupled to the first conductor.

A circuit for providing synchronous switching of a current flowing through an inductor and a first conductor, comprising:

• (a) a comparator having a first input coupled to the first conductor and a second input coupled to a reference voltage conductor;
• (b) means for operating the comparator to produce a “1” level in response to a change of voltage of the first conductor caused by the flow of the current;
• and
• (c) means for operating in response to the “1” level to turn on both a first transistor and a second transistor in response to a first switching of the comparator to a “1” level, and to turn off only the first transistor in response to a second switching of the comparator to the “1” level, and to turn off the second transistor in response to a third switching of the comparator to the “1” level, the first transistor having a gate coupled to the first output, a source coupled to the reference voltage conductor, and a drain coupled to the first conductor, and the second transistor having a gate coupled to the second output, a source coupled to the reference voltage conductor, and a drain coupled to the first conductor.

A voltage converter circuit comprising:

• (a) a first transistor having a drain connected to receive an unregulated input voltage, a gate connected to receive a feedback control signal, and a source connected to a first conductor;
• (b) an inductor having a first terminal coupled to the first conductor and a second terminal connected to produce a regulated output voltage on an output conductor;
• (c) a feedback control circuit coupled between the gate of the first transistor and the output conductor for regulating switching of the first transistor in response to the regulated output voltage;
• and
• (d) a synchronous rectifier circuit including
• i. a comparator having a first input coupled to the first conductor and a second input coupled to the reference voltage conductor,
• ii. a logic circuit having an input coupled to an output of the comparator, a first output, and a second output,
• iii. a second transistor having a gate coupled to the first output, a source coupled to the reference voltage conductor, and a drain coupled to the first conductor;
• and
• (e) wherein the logic circuit is operative to produce a first logic signal indicative of when the first transistor is completely turned off and to rapidly turn on the second transistor in response to the first logic signal to avoid delay associated with the comparator.

A voltage converter circuit comprising:

• (a) a first transistor having a drain connected to receive an unregulated input voltage, a gate connected to receive a feedback control signal, and a source connected to a first conductor;
• (b) an inductor having a first terminal coupled to the first conductor and a second terminal connected to produce a regulated output voltage on an output conductor;
• (c) a feedback control circuit coupled between the gate of the first transistor and the output conductor for regulating switching of the first transistor in response to the regulated output voltage;
• and
• (d) a synchronous rectifier circuit including
• i. a comparator having a first input coupled to the first conductor and a second input coupled to the reference voltage conductor,
• ii. a logic circuit having an input coupled to an output of the comparator, a first output, and a second output,
• iii. a second transistor having a gate coupled to the first output, a source coupled to the reference voltage conductor, and a drain coupled to the first conductor;
• (e) wherein the logic circuit includes means for producing a first logic signal indicative of when the first transistor is completely turned off and rapidly turning on the second transistor in response to the first logic signal to avoid delay associated with the comparator.