Control circuit and method for maintaining high efficiency over broad current ranges in a switching regulator circuit
DC CAFCFirst Claim
1. A circuit for controlling a switching voltage regulator, the regulator having (1) a switch coupled to receive an input voltage and including a pair of synchronously switched switching transistors and (2) an output for supplying current at a regulated voltage to a load which includes an output capacitor, the circuit comprising:
- a first circuit for monitoring the output to generate a first feedback signal;
a second circuit for generating a first control signal during a first state of circuit operation, the first control signal being responsive to the first feedback signal to vary the duty cycle of the switching transistors to maintain the output at the regulated voltage; and
a third circuit for generating a second control signal during a second state of circuit operation to cause both switchin transistors to be OFF for a first period of time during which the output capacitor maintains the output substantially at the regulated voltage.
4 Assignments
Litigations
0 Petitions
Accused Products
Abstract
A circuit and method for controlling a switching voltage regulator having (1) a switch including one or more switching transistors and (2) an output adapted to supply current at a regulated voltage to a load including an output capacitor. The circuit and method generates a control signal to turn said one or more switching transistors OFF under operating conditions when the voltage at the output is capable of being maintained substantially at the regulated voltage by the charge on the output capacitor. Such a circuit and method increases the efficiency of the regulator circuit particularly at low average current levels.
-
Citations
35 Claims
-
1. A circuit for controlling a switching voltage regulator, the regulator having (1) a switch coupled to receive an input voltage and including a pair of synchronously switched switching transistors and (2) an output for supplying current at a regulated voltage to a load which includes an output capacitor, the circuit comprising:
-
a first circuit for monitoring the output to generate a first feedback signal;
a second circuit for generating a first control signal during a first state of circuit operation, the first control signal being responsive to the first feedback signal to vary the duty cycle of the switching transistors to maintain the output at the regulated voltage; and
a third circuit for generating a second control signal during a second state of circuit operation to cause both switchin transistors to be OFF for a first period of time during which the output capacitor maintains the output substantially at the regulated voltage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33)
a one-shot circuit for generating the first control signal, the first control signal being generated over a second period of time during a switch cycle.
-
-
8. The circuit of claim 7, wherein the second period of time is a predetermined time period.
-
9. The circuit of claim 8, wherein the second circuit includes a fourth circuit for monitoring the current supplied to the load to generate a current feedback signal.
-
10. The circuit of claim 9, wherein the switch is adapted to be coupled to an inductor and the fourth circuit monitors the inductor current to generate the current feedback signal.
-
11. The circuit of claim 10, wherein the fourth circuit compares the current feedback signal to a reference current value and triggers the one-shot circuit when the current feedback signal exceeds the reference current value.
-
12. The circuit of claim 11, wherein the fourth circuit includes a current comparator for triggering the one-shot circuit, the current comparator having a first input coupled to receive the current feedback signal and a second input coupled to a current source for providing the reference current value.
-
13. The circuit of claim 12, wherein the current source includes:
-
a transconductance amplifier supplying a current substantially proportional to the difference in voltage between the first feedback signal and a constant voltage; and
a constant current source coupled in parallel with the transconductance amplifier.
-
-
14. The circuit of claim 7, wherein the second period of time is dependent upon the input voltage.
-
15. The circuit of claim 14, wherein the switch is coupled to an inductor, and wherein the second period of time is decreased in response to a decrease in the input voltage, whereby the oscillation frequency of the ripple current through said inductor is increased from an audible frequency to one that does not generate substantial user noise.
-
16. The circuit of claim 7, wherein the second period of time is dependent upon the voltage at the load.
-
17. The circuit of claim 16, wherein the switch is coupled to an inductor, and wherein the second period of time is increased in response to a decrease in the voltage at the load, whereby the total decrease in current through said inductor is increased while the first control signal is generated.
-
18. The circuit of claim 7, wherein the one-shot circuit is maintained substantially OFF during the second state of operation, whereby the efficiency of the switching regulator circuit is increased as the circuit changes from the first to the second state of operation.
-
19. The circuit of claim 12, wherein the current comparator is maintained substantially OFF during the second state of operation, whereby the efficiency of the switching regulator circuit is increased as the circuit changes from the first to the second state of operation.
-
20. The circuit of claim 1, wherein the third circuit includes a user-activated switch and wherein the second control signal is generated in response to activation of the user switch.
-
21. The circuit of claim 20 wherein:
-
the second circuit includes a transconductance amplifier supplying a current substantially proportional to the difference in voltage between the feedback signal and a constant voltage during the first state of operation; and
wherein activation of the user switch introduces hysteresis into the transconductance amplifier.
-
-
22. The circuit of claim 20, wherein the second circuit includes:
a one-shot circuit for generating the first control signal, the first control signal being generated over a second period of time during a switch cycle.
-
23. The circuit of claim 22, wherein the second period of time is a predetermined time period.
-
24. The circuit of claim 23, wherein the second circuit includes a fourth circuit for monitoring the current supplied to the load to generate a current feedback signal.
-
25. The circuit of claim 24, wherein the fourth circuit compares the current feedback signal to a reference current value and triggers the one-shot circuit when the current feedback signal exceeds the reference current value.
-
26. The circuit of claim 22, wherein the second period of time is dependent upon the input voltage.
-
27. The circuit of claim 26, wherein the switch is coupled to an inductor, and wherein the second period of time is decreased in response to a decrease in the input voltage, whereby the oscillation frequency of the ripple current through said inductor is increased from an audible frequency to one that does not generate substantially user noise.
-
28. The circuit of claim 22, wherein the second period of time is dependent upon the voltage at the load.
-
29. The circuit of claim 28, wherein the switch is coupled to am inductor, and wherein the second period of time is increased in response to a decrease in the voltage at the load, whereby the total decrease in current through said inductor is increased while the first control signal is generated.
-
30. The circuit of claim 22, wherein the one-shot circuit is maintained substantially OFF during the second state of operation, whereby the efficiency of the switching regulator circuit is increased as the circuit changes from the first to the second state of operation.
-
31. The circuit of claim 1, wherein the circuit is adapted for controlling a switching voltage regulator circuit having first and second switching transistors coupled in series between an input voltage and ground, wherein the first and second switching transistors are commonly coupled at the output terminal, and wherein the input voltage is higher than the voltage at the load, whereby the switching voltage regulator is a step-down voltage regulator.
-
32. The circuit of claim 1, wherein the circuit is adapted for controlling a switching voltage regulator circuit wherein the input voltage is lower than the voltage at the load, whereby the switching voltage regulator is a step-up voltage regulator.
-
33. The circuit of claim 1, wherein the circuit is adapted for controlling a switching voltage regulator circuit wherein the input voltage has an opposite polarity than the voltage at the load, whereby the switching voltage regulator is a polarity-inversing voltage regulator.
-
34. A method for controlling a switching voltage regulator, the regulator having (1) a switch coupled to receive an input voltage and including a pair of synchronously switched switching transistors and (2) an output for supplying current at a regulated voltage to a load which includes an output capacitor, the method comprising the steps of:
-
(a) monitoring the output to generate a first feedback signal;
(b) varying the duty cycle of the switching transistors in response to the first feedback signal to maintain the output at the regulated voltage during a first state of circuit operations;
(c) turning both switching transistors OFF for a first period of time following the first state of circuit operation so as to allow the output capacitor to maintain the output substantially at the regulated voltage by discharging during a second state of circuit operation; and
(d) turning at least one of said switching transistors ON to recharge the output capacitor following the second state of circuit operation.
-
-
35. A circuit for controlling a switching voltage regulator, the regulator having (1) a switch coupled to receive an input voltage and including a pair of synchronously switched switching transistors and (2) an output for supplying current at a regulated voltage to a load which includes an output inductor, the circuit comprising:
-
a first circuit for monitoring the output to generate a first feedback signal;
a second circuit for generating a first control signal during a first state of circuit operation, the first control signal being responsive to the first feedback signal to vary the duty cycle of the switching transistors to maintain the output at the regulated voltage; and
a third circuit for monitoring the current to the load to generate a second control signal during a second state of circuit operation to cause one of said switching transistors to be maintained OFF when the magnitude of the monitored current falls below a current threshold.
-
Specification