Constant On-Time Regulator With Increased Maximum Duty Cycle
First Claim
1. A buck switching regulator formed on an integrated circuit and receiving an input voltage, the buck switching regulator controlling a high-side switch and a low-side switch using a feedback control loop to drive a switch output node for generating a switching output voltage, the switch output node being coupled to an LC filter circuit external to the integrated circuit to generate a regulated output voltage having a substantially constant magnitude on an output node, the regulated output voltage being fed back to the buck switching regulator to a voltage divider for generating a feedback voltage on a feedback voltage node, the buck switching regulator comprising:
- an on-time control circuit for generating a first signal for controlling the high-side switch under a minimum on-time and variable off-time feedback control loop, the first signal turning off the high-side switch at the expiration of a first on-time duration or at the expiration of a maximum on-time, the first on-time duration being at least a minimum on-time and being expanded to the maximum on-time when the feedback voltage remains less than a reference voltage, and the maximum on-time comprising a first maximum on-time and a second, extended maximum on-time greater than the first maximum on-time, wherein the second, extended maximum on-time is applied when a minimum off-time was used for the high-side switch during the previous switching cycle.
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Abstract
A buck switching regulator receives an input voltage and provides a switching output voltage on a switch output node using a minimum on-time, variable off-time feedback control loop. The buck switching regulator includes an on-time control circuit for generating a first signal for turning off the high-side switch at the expiration of a first on-time duration or at the expiration of a maximum on-time. The first on-time duration is at least a minimum on-time and is allowed to expand to a maximum on-time when the feedback voltage remains less than a reference voltage. The maximum on-time includes a first maximum on-time and a second, extended maximum on-time. The second maximum on-time is applied when a minimum off-time was used for the high-side switch during the previous switching cycle. In another embodiment, the second maximum on-time is applied only when the switching regulator is not being current limited.
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Citations
12 Claims
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1. A buck switching regulator formed on an integrated circuit and receiving an input voltage, the buck switching regulator controlling a high-side switch and a low-side switch using a feedback control loop to drive a switch output node for generating a switching output voltage, the switch output node being coupled to an LC filter circuit external to the integrated circuit to generate a regulated output voltage having a substantially constant magnitude on an output node, the regulated output voltage being fed back to the buck switching regulator to a voltage divider for generating a feedback voltage on a feedback voltage node, the buck switching regulator comprising:
an on-time control circuit for generating a first signal for controlling the high-side switch under a minimum on-time and variable off-time feedback control loop, the first signal turning off the high-side switch at the expiration of a first on-time duration or at the expiration of a maximum on-time, the first on-time duration being at least a minimum on-time and being expanded to the maximum on-time when the feedback voltage remains less than a reference voltage, and the maximum on-time comprising a first maximum on-time and a second, extended maximum on-time greater than the first maximum on-time, wherein the second, extended maximum on-time is applied when a minimum off-time was used for the high-side switch during the previous switching cycle. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method in buck switching regulator receiving an input voltage and controlling a high-side switch and a low-side switch using a feedback control loop to drive a switch output node for generating a switching output voltage, the switch output node being coupled to an LC filter circuit to generate a regulated output voltage having a substantially constant magnitude on an output node, the regulated output voltage being fed back to the buck switching regulator to a voltage divider for generating a feedback voltage on a feedback voltage node, the method comprising:
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providing a first on-time duration for the high-side switch being at least a minimum on-time and being expanded to a maximum on-time when the feedback voltage remains less than a reference voltage;
providing a first maximum on-time or a second, extended maximum on-time greater than the first maximum on-time as the maximum on-time;
applying the first maximum on-time when a minimum off-time was not used for the high-side switch during the previous switching cycle;
applying the second, extended maximum on-time when a minimum off-time was used for the high-side switch during the previous switching cycle; and
generating a first signal for turning off the high-side switch under a minimum on-time and variable off-time feedback control loop, the first signal turning off the high-side switch at the expiration of the first on-time duration or at the expiration of the first or second maximum on-times. - View Dependent Claims (10, 11, 12)
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Specification