SWITCHING DC-TO-DC CONVERTER WITH DISCONTINUOUS PULSE SKIPPING AND CONTINUOUS OPERATING MODES WITHOUT EXTERNAL SENSE RESISTOR
First Claim
1. A switching DC-to-DC converter which generates an output potential Vout at an output node in response to an input potential, said converter comprising:
- a switching controller configured to generate at least one switch control signal including a first switch control signal in response to a first feedback signal indicative of the output potential Vout and a second feedback signal indicative of kVout, where k is a constant, the switching controller having a switching period; and
external circuitry including a first power switch and an inductor, wherein the first power switch has an input coupled to receive the input potential and an output coupled to a first node and is coupled to receive the first switch control signal, the inductor is coupled between the first node and the output node, and an inductor current flows through the inductor during operation of the converter, wherein the switching controller is configured to operate in a continuous mode in which the inductor current remains above zero and the first switch control signal causes the first power switch to operate with a continuous mode duty cycle determined by the first feedback signal, and the switching controller is configured to enter a discontinuous pulse skipping mode in response to the inductor current falling to zero, wherein in the discontinuous pulse skipping mode, the first switch control signal causes the first power switch to operate with a duty cycle which is the longer of a minimum duty cycle and a discontinuous mode duty cycle, wherein the discontinuous mode duty cycle is a duty cycle at which the converter would operate in response to said first feedback signal when said converter generates the output potential in response to the input potential during a discontinuous mode without pulse skipping.
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Accused Products
Abstract
A switching DC-to-DC converter having at least one power channel including an inductor and a controller which generates at least one power switch control signal for at least one power switch of each power channel. The converter is configured to operate in a continuous mode when the inductor current remains above zero, to enter a discontinuous pulse skipping mode of operation when the inductor current falls to zero (which occurs when the load current is below a threshold value), and to leave the discontinuous pulse skipping mode and resume continuous mode operation when the inductor current rises above zero. The main difference between the continuous and discontinuous pulse skipping modes is that in the continuous mode, a power switch has a duty cycle determined by a feedback signal indicative of the converter'"'"'s output potential Vout (so that the duty cycle is independent of the current drawn from the converter by the load), and in the discontinuous pulse skipping mode the power switch has a duty cycle which is the longer of a minimum duty cycle and a discontinuous (non-pulse-skipping) mode duty cycle. The discontinuous pulse skipping mode is more efficient than the continuous mode under conditions of low load current. Preferably, the controller includes cycle-skipping circuitry operable in the discontinuous pulse skipping mode and optionally also the continuous mode to cause the power switch to remain off for at least one cycle under the condition that the converter'"'"'s output potential rises above a threshold. Preferably, the cycle-skipping circuitry includes a comparator which compares an error amplifier output (indicative of the converter output potential) with a threshold potential, and logic circuitry (e.g., an AND gate coupled to the comparator output) which asserts a latch-clearing signal once per switching cycle when the comparator output indicates that the converter'"'"'s output has risen above the threshold. Other aspects of the invention are a switching controller for use in such a converter and a method for generating power switch control signals for such a converter in a discontinuous pulse skipping mode of operation.
37 Citations
47 Claims
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1. A switching DC-to-DC converter which generates an output potential Vout at an output node in response to an input potential, said converter comprising:
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a switching controller configured to generate at least one switch control signal including a first switch control signal in response to a first feedback signal indicative of the output potential Vout and a second feedback signal indicative of kVout, where k is a constant, the switching controller having a switching period; and
external circuitry including a first power switch and an inductor, wherein the first power switch has an input coupled to receive the input potential and an output coupled to a first node and is coupled to receive the first switch control signal, the inductor is coupled between the first node and the output node, and an inductor current flows through the inductor during operation of the converter, wherein the switching controller is configured to operate in a continuous mode in which the inductor current remains above zero and the first switch control signal causes the first power switch to operate with a continuous mode duty cycle determined by the first feedback signal, and the switching controller is configured to enter a discontinuous pulse skipping mode in response to the inductor current falling to zero, wherein in the discontinuous pulse skipping mode, the first switch control signal causes the first power switch to operate with a duty cycle which is the longer of a minimum duty cycle and a discontinuous mode duty cycle, wherein the discontinuous mode duty cycle is a duty cycle at which the converter would operate in response to said first feedback signal when said converter generates the output potential in response to the input potential during a discontinuous mode without pulse skipping. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 18, 19, 20, 21, 22, 23, 24, 27, 28, 29, 30, 31)
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17. A switching DC-to-DC converter which generates an output potential Vout at an output node in response to an input potential, said converter comprising:
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a switching controller configured to generate at least a first switch control signal and a second switch control signal in response to a first feedback signal indicative of the output potential Vout and a second feedback signal indicative of kVout, where k is a constant, the switching controller having a switching period; and
external circuitry including a first power switch, a second power switch, and an inductor, wherein the first power switch has an input coupled to receive the input potential, an output coupled to a first node, and a control terminal coupled to receive the first switch control signal, the second power switch has an input coupled to the first node, an output coupled to a second node, and a control terminal coupled to receive the second switch control signal, the inductor is coupled between the first node and the output node, and an inductor current flows through the inductor during operation of the converter, wherein the switching controller is configured to operate in a continuous mode in which the inductor current remains above zero and the first switch control signal causes the first power switch to operate with a continuous mode duty cycle determined by the first feedback signal, and the switching controller is configured to enter a discontinuous pulse skipping mode in response to the inductor current falling to zero, wherein in the discontinuous pulse skipping mode, the first switch control signal causes the first power switch to operate with a duty cycle which is the longer of a minimum duty cycle and a discontinuous mode duty cycle, wherein the discontinuous mode duty cycle is a duty cycle at which the converter would operate in response to said first feedback signal when said converter generates the output potential in response to the input potential during a discontinuous mode without pulse skipping.
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32. A switching controller having a switching period for use with power channel circuitry of a switching DC-to-DC converter, wherein the power channel circuitry generates an output potential Vout at an output node in response to an input potential, the power channel circuitry includes a first power switch and an inductor, the first power switch has an input coupled to receive the input potential and an output coupled to a first node, and the inductor is coupled between the first node and the output node so that an inductor current flows through the inductor during operation of the converter, said controller comprising:
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switch control signal generation circuitry configured to generate at least one switch control signal including a first switch control signal in response to set and reset signals; and
additional circuitry coupled to the switch control signal generation circuitry and to receive a first feedback signal indicative of the output potential Vout and a second feedback signal indicative of kVout, where k is a constant, wherein the additional circuitry is configured to generate the set signals and the reset signals in response to the first feedback signal and the second feedback signal, wherein the controller is configured to operate in a continuous mode in which the inductor current remains above zero and the first switch control signal causes the first power switch to operate with a continuous mode duty cycle determined by the first feedback signal, and the controller is configured to enter a discontinuous pulse skipping mode in response to the inductor current falling to zero, wherein in the discontinuous pulse skipping mode, the first switch control signal causes the first power switch to operate with a duty cycle which is the longer of a minimum duty cycle and a discontinuous mode duty cycle, wherein the discontinuous mode duty cycle is a duty cycle at which the converter would operate in response to said first feedback signal when said converter generates the output potential in response to the input potential during a discontinuous mode without pulse skipping. - View Dependent Claims (33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43)
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44. A method for generating a power switch control signal for a DC-to-DC converter which generates an output potential Vout at an output node in response to an input potential by switching at least a first power switch having an input coupled to receive the input potential and an output coupled to a first node, wherein the converter has an inductor coupled between the first node and the output node so that an inductor current flows through the inductor during operation of the converter, said method including the steps of:
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(a) in a continuous mode in which the inductor current remains above zero, generating the power switch control signal in response to a feedback signal indicative of the output potential Vout, such that said power switch control signal causes the first power switch to operate with a continuous mode duty cycle determined by the feedback signal; and
(b) entering a discontinuous pulse skipping mode when the inductor current falls to zero, and in the discontinuous mode, generating the power switch control signal in response to a second feedback signal indicative of kVout , where k is a constant, and in response to the feedback signal, such that said power switch control signal causes the first power switch to operate with a duty cycle equal to the longer of a minimum duty cycle and a discontinuous mode duty cycle, wherein the discontinuous mode duty cycle is a duty cycle at which the converter would operate in response to said feedback signal when said converter generates the output potential in response to the input potential during a discontinuous mode without pulse skipping. - View Dependent Claims (45, 46, 47)
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Specification