Electricity: power supply or regulation systems – In shunt with source or load – Using choke and switch across source
Reexamination Certificate
1999-10-26
2001-01-30
Berhane, Adolf (Department: 2838)
Electricity: power supply or regulation systems
In shunt with source or load
Using choke and switch across source
C363S059000
Reexamination Certificate
active
06181114
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to processing systems and specifically to a boost circuit for a processing system.
BACKGROUND OF THE INVENTION
Typically a power supply in a desktop computer requires the maintenance of an auxiliary output voltage for the operation of the service processor and for internal house keeping. This auxiliary output voltage is generally a separate small power supply within a power supply and is used to provide continuous current even when other power outputs are turned off However, this small power supply adds extra cost and instrumentation to the overall system.
FIG. 1
depicts a conventional auxiliary bias circuit in a power supply. The area enclosed by the dashed line contains a flyback auxiliary power supply
10
. The remaining represents a boost circuit and a chopper circuit. The boost circuit and chopper circuit include a boost inductor
12
, MOSFET transistors
16
,
24
, a pulse width modulator
18
, capacitors
20
,
44
, a transformer
22
, an inductor
42
and diodes
14
,
38
,
40
. The flyback auxiliary power supply
10
includes a pulse width modulator
26
, a transistor
28
, a transformer
30
, a diode
32
, a capacitor
33
, an error amplifier
34
and an opto-coupler
36
.
To further understand the operation of a conventional auxiliary bias circuit in a power supply, please refer now to the flowchart of FIG.
2
. First, the input voltage to the flyback
10
is provided by the boost voltage developed across the bulk capacitor
20
, via step
102
. Next, the pulse width modulator
26
is used to chop this voltage through transformer
30
and transistor
28
at a high switching frequency (100 kHz), via step
104
. Transformer
30
then transforms the bulk voltage to the secondary side where it gets rectified by diode
32
and filtered by capacitor
33
, via step
106
. Finally, the error amplifier
34
regulates the output voltage by modulating the pulse width of pulse width modulator
26
, via step
108
.
Because the flyback auxiliary power supply
10
is segregated from the boost circuit, it requires a separate pulse width modulator
26
, a separate transformer
30
, and a separate MOSFET transistor
28
which increases the cost of the power supply system.
Accordingly, what is needed is a circuit that decreases the cost of the power supply system. The present invention addresses such a need.
SUMMARY OF THE INVENTION
A boost circuit is disclosed. The circuit comprises a boost transistor, a pulse width modulator coupled to the boost transistor, and a boost inductor coupled to the boost transistor and the pulse width modulator, the boost inductor including a winding which provides an auxiliary output voltage.
Through the use of the boost circuit in accordance with the present invention, the auxiliary output voltage is generated by the boost stage operation. Ergo, the present invention provides the auxiliary output voltage supply by using the same pulse width modulator and primary switching devices as used by the boost stage. The use of a boost circuit in accordance with the present invention thereby eliminates the need for the components required to maintain the auxiliary output voltage. Accordingly, system space can be saved and there is a reduction in manufacturing costs.
REFERENCES:
patent: 5504418 (1996-04-01), Ashley
patent: 5691627 (1997-11-01), Shum
patent: 5691889 (1997-11-01), Bazinet et al.
patent: 6037754 (2000-03-01), Harper
Hemena William
Malik Randhir
Berhane Adolf
International Business Machines - Corporation
Sawyer Law Group LLP
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