Electricity: power supply or regulation systems – Output level responsive – Using a three or more terminal semiconductive device as the...
Reexamination Certificate
2000-04-24
2001-12-11
Patel, Rajnikant (Department: 2838)
Electricity: power supply or regulation systems
Output level responsive
Using a three or more terminal semiconductive device as the...
C323S282000
Reexamination Certificate
active
06329801
ABSTRACT:
BACKGROUND
The present invention relates generally to voltage regulators, and more particularly to control systems for switching voltage regulators.
Voltage regulators, such as DC to DC converters, are used to provide stable voltage sources for electronic systems. Efficient DC to DC converters are particularly needed for battery management in low power devices, such as laptop notebooks and cellular phones. Switching voltage regulators (or more simply “switching regulators”) are known to be an efficient type of DC to DC converter. A switching regulator generates an output voltage by converting an input DC voltage into a high frequency voltage, and filtering the high frequency voltage to generate the output DC voltage. Typically, the switching regulator includes a switch for alternately coupling and de-coupling an input DC voltage source, such as a battery, to a load, such as an integrated circuit. An output filter, typically including an inductor and a capacitor, is coupled between the input voltage source and the load to filter the output of the switch and thus provide the output DC voltage. A controller measures an electrical characteristic of the circuit, e.g., the voltage or current passing through the load, and sets the duty cycle of the switch in order to maintain the output DC voltage at a substantially uniform level.
Voltage regulators for microprocessors are subject to ever more stringent performance requirements. One trend is to operate at higher currents, e.g., 35-50 amps. Another trend is to turn on or off different parts of the microprocessor in each cycle in order to conserve power. This requires that the voltage regulator react very quickly to changes in the load, e.g., several nanoseconds to shift from the minimum to the maximum load. Another trend is to require the voltage regulator to have a “standby mode” which consumes little power at low loads. In addition to these specific trends, high efficiency is generally desirable in order to avoid thermal overload at high loads and to increase battery life in portable systems.
Unfortunately, some conventional voltage regulators operate well at either large or small loads, but not both. In addition, some buck regulators do not function properly when the output voltage is comparable to the input voltage. Other problems that occur in voltage regulators include the following: large ripple current losses, voltage overshooting during start-up and quickly changing load conditions, and electrical noise from the opening and closing of the power switches in the regulator.
Conventional controllers often employ analog control and design techniques to achieve voltage regulation. Such techniques often result in implementations of comparatively large die area and design complexity. Moreover, such implementations are not easily integrated into larger systems or ported among different processing technologies.
In view of the foregoing, there is room for improvement in voltage regulators and control systems for voltage regulators.
SUMMARY
In one aspect, the invention is directed to a voltage regulator having an input terminal to be coupled to an input voltage source and an output terminal to be coupled to a load. The voltage regulator has a first switch to intermittently couple the output terminal to the input terminal, a voltage sensor to detect a voltage at the output terminal, a current sensor to detect a current flowing along a circuit path between the input terminal and the output terminal and a controller connected to the switch, the voltage sensor and the current sensor. The controller is configured to close the first switch if the voltage is less than a first threshold voltage and the current is less than a first threshold current, and the controller is configured to open the first switch if the voltage is greater than a second threshold voltage and the current is greater than a second threshold current.
Implementations of the invention may include one or more of the following features. The first threshold current may be greater than the second threshold current, and the first threshold voltage may be equal to the second threshold voltage. The controller may receive a clock signal from an external clock, and the controller may be configured to delay switching of the first switch until a clock boundary on the external clock. A second switch may intermittently couple the output terminal to ground. The controller may be configured to open the second switch if the first switch closes or the current is less than a third threshold current (e.g., about zero current). The controller may be configured to open the first switch and close the second switch if the first switch has been open for longer than a first duration and the voltage exceeds the second threshold voltage. The controller may be configured to open the first switch if the current is greater than a fourth threshold current. The fourth threshold current may be approximately equal to a nominal maximum load current plus a ripple current. The controller may be configured to close the first switch for a minimum first duration. A filter may be positioned in the circuit path between the input terminal and the output terminal. The filter may include an inductor coupling the intermediate terminal to the output terminal, and a capacitor coupling the output terminal to ground.
In another aspect, the invention is directed to a voltage regulator having an input terminal to be coupled to an input voltage source and an output terminal to be coupled to a load. The voltage regulator has a first switch to intermittently couple the output terminal to the input terminal, a voltage sensor to detect a voltage at the output terminal, a current sensor to detect a current flowing along a circuit path, and a controller connected to the switch, the voltage sensor and the current sensor. The controller may be configured to close the first switch if the voltage is less than a first threshold voltage and the current is less than a first threshold current, and the controller is configured to open the first switch if the voltage is greater than the first threshold voltage and the current is greater than a second threshold current, the first threshold current being greater than the second threshold current.
In another aspect, the invention is directed to a voltage regulator that has an input terminal to be coupled to an input voltage source, an output terminal to be coupled to a load, a first switch to intermittently couple the output terminal to the input terminal, a voltage sensor to detect a voltage at the output terminal, a current sensor to detect a current flowing along the circuit path, and a controller connected to the switch, the voltage sensor and the current sensor. The controller is configured to direct current pulses of a fixed amplitude to the output terminal if the current load is less than a first threshold, to direct current pulses of increasing amplitude to the output terminal if the current load is between the first threshold and a second threshold, and to permit current to flow continuously to the output terminal if the current load is greater than the second threshold.
In another aspect, the invention is directed to a method of operating a voltage regulator having an input terminal to be coupled to an input voltage source and an output terminal to be coupled to a load. In the method, a voltage at the output terminal is determined, a current flowing through a circuit path between the input terminal and the output terminal is determined, a switch is closed to electrically couple the output input terminal to the input terminal if the voltage is less than a first threshold voltage and the current is less than a first threshold current, and the switch is opened if the voltage is greater than a second threshold voltage and the current is greater than a second threshold current.
Implementations of the invention may include one or more of the following features. The first threshold current may be greater than the second threshold current. The first threshold voltage may be equal to the second
Lidsky David B.
Nickel Charles
Stratakos Anthony J.
Zuniga Marco A.
Fish & Richardson PC
Patel Rajnikant
Volterra Semiconductor Corporation
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