Electricity: power supply or regulation systems – In shunt with source or load – Using choke and switch across source
Reexamination Certificate
1999-12-08
2001-02-13
Sterrett, Jeffrey (Department: 2838)
Electricity: power supply or regulation systems
In shunt with source or load
Using choke and switch across source
C323S283000, C323S284000
Reexamination Certificate
active
06188206
ABSTRACT:
BACKGROUND
This disclosure relates to voltage regulators and more specifically, to a hysteretic mode synchronous buck voltage regulator.
A voltage regulator converts an input voltage to a regulated output voltage. Although there are many types and applications for voltage regulators, one such type is a switching, DC-to-DC, step-down voltage regulator, or “buck” regulator. The switching regulator is often chosen due to its small size and efficiency. An example of a typical application is a battery-powered electronic device such as a portable computer. In an example such as this, a voltage regulator is required to provide a predetermined and constant output voltage to a load from an often-fluctuating input voltage source, the battery.
A hysteretic-mode voltage regulator works by regulating the output voltage according to a particular hysteresis level or output voltage ripple. A hysteretic controller in the voltage regulator maintains the output voltage within a hysteresis band centered about the internal reference voltage. The level of hysteresis or ripple is fixed through the entire load range of the voltage regulator.
In a switching regulator, the field-effect transistors (FETs) switch on and off to maintain a certain switching frequency. During this switching time, the transistors enter a linear region where much power is dissipated because the FETs are sourcing current.
SUMMARY
The inventors noticed that when the voltage regulator is heavily loaded, average transition FET power dissipation increases in response to an increase in switching frequency. However, when the voltage regulator is lightly loaded, the transition FET power dissipation becomes negligible compared to an inductor ripple current. An increase in the ripple current causes magnetic inductor core loss and output capacitor equivalent-series-resistance (ESR) loss. Thus, when the regulator is lightly loaded, the inductor ripple current increases in response to a decrease in switching frequency. Therefore, it is advantageous to vary the switching frequency of the regulator according to the load indication. This ability to vary the switching frequency significantly reduces the quiescent power dissipation of the voltage regulator.
A dynamic switching voltage regulator includes a load indicator, power switches, and a controller. The load indicator generates a load signal responsive to different output load conditions of the regulator. The controller receives the load signal and drives the power switches at a first switching frequency. The controller changes the switching frequency to a second frequency in response to a change in the load signal.
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Nguyen Don J.
Solivan Thovane
Fish & Richardson P.C.
Intel Corporation
Sterrett Jeffrey
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