Phase control for a computer system multi-phase power supply

Details Phase control for a computer system multi-phase power supply Phase control for a computer system multi-phase power supply

2000-05-30

2001-09-18

Han, Jessica (Department: 2838)

Electricity: power supply or regulation systems

Output level responsive

Using a three or more terminal semiconductive device as the...

C323S267000, C713S300000

Reexamination Certificate

active

06291976

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
Not applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to power supplies for computer systems. More specifically, the invention relates to switching power supplies for computer systems. More specifically still, the present invention relates to generating phase control signals for switching power supplies having multiple phases.
2. Background of the Invention
As computer system technology advances, specifically as manufacturing techniques related to microprocessors or central processing units (CPUs) advances, more and more transistors and related functionality are placed on a single die of a CPU. As more transistors are placed closer together on semiconductor substrates, less insulation material (in the form of oxide layers) exists between each transistor. Accordingly, CPU operating voltages are lowered to protect against electrical breakdown between transistors. However, adding transistors to a CPU increases the amount of electrical current the CPU requires. Thus, while the operating voltage for CPUs is generally dropping as technology advances, required operating currents are steadily rising. For example, Intel Corporation's most recent processor named the Pentium® 4 may have operating voltages in the range of 0.9-1.7 volts. Operating voltage for a particular processor, even in the same series, may differ depending on the characteristics of the particular CPU. While Intel's Pentium® 4 processor has a low voltage requirement, the processor may require as many as 50-60 Amps of current at peak loads. Compared to Intel's Pentium® II processor, which required only 20 Amps or less, this new processor as much as triples the amperage demand. Every computer system has a power supply that converts the 120 Volt alternating current (AC) found in a standard wall receptacle to suitable direct current (DC) voltages. This conversion from AC to DC is typically done by a switching power supply. A switching power supply supplying power to the Pentium® 4 processor should be capable of supplying current swings having transient response in the range of 100 Amps per micro-second. Prior CPU's may have required as little as 50 amps per micro-second transient response. Thus, there are increasing demands on the capabilities of switching power supplies with each advance in CPU technology. Other microprocessors may have similar power requirements, for example an AMD Athlon®.
FIG. 1
shows an exemplary partial electrical schematic of a single phase blick-type switching power supply. The circuit shown in
FIG. 1
is said to have only a single phase because it has only one switch and inductor combination. If there were several of these switch and inductor combinations present, the power supply would be considered a multi-phase switching power supply. Buck-type switching power supplies are designed to provide lower direct current (DC) voltages than applied at their inputs while supplying the current demand of a load (c.g., CPU). Power supplies provide reduced DC voltages by “chopping” the supply voltage (i.e. turning on and off at a particular frequency )via switch
1
and then averaging, by means of an inductor/capacitor circuit
2
, the chopped voltage to produce DC voltage at the desired level.
In the early days of microprocessor technology, a computer system switching power supply may have had only a single phase, as explained above, inasmuch as the processor voltage and amperage requirements were such that a single phase switching power supply was capable of producing the desired voltage with the desired current. While a single phase switching power supply may be capable of meeting average voltage and current requirements, a single phase alone may not be capable of meeting higher transient requirements of modern CPUs. Another consideration in switching power supply design, especially as related to power supplies mounted on a motherboard, is the amount of space required to implement such a supply. If a single switching phase is used, the inductor and capacitor in the averaging portion of the circuit may need to be excessively large occupying too much space on the motherboard.
Increasing the number of phases in a switching power supply permits the capacitor and inductor in each phase to be smaller, as is well understood in the art. Thus, in response to demands such as these, manufacturers generally have increased the number of phases in switching power supplies to meet increasing amperage requirements, space limitations and transient response requirements. However, there are various problems associated with having multiple phases in a switching power supply including how to generate phase control signals as the number of phases increases.
BRIEF SUMMARY OF THE INVENTION
The problems noted above are solved in large part by a method and apparatus for generating phase enable signals to be coupled to switches of the various phases of a switching power supply. The phase enable signals are created by generating a master clock signal having a frequency substantially equal to the number of phases multiplied by the switching frequency of each phase. This master clock signal couples to a shift register clock input signal. One of the shift output signals of the shift register, a feedback signal, is coupled to the shift input of the shift register by way of an inverting buffer. By clocking the shift register at the frequency of the master clock, and thereby shifting in the inverted representation of one of the shift Output signals, a series of phase enable signals are generated with each having the same frequency, yet shifted in phase. The master clock generation in combination with the shift register is easily adapted to accommodate switching power supplies having a various number of switching phases.


REFERENCES:
patent: 5581274 (1996-12-01), Tagawa
patent: 6052790 (2000-04-01), Brown

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