Electricity: power supply or regulation systems – Output level responsive – Using a three or more terminal semiconductive device as the...
Reexamination Certificate
1998-05-14
2001-03-13
Wong, Peter S. (Department: 2838)
Electricity: power supply or regulation systems
Output level responsive
Using a three or more terminal semiconductive device as the...
C323S282000, C327S541000
Reexamination Certificate
active
06201374
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to electrical power systems and more particularly relates to the integration of voltage regulation and power switching systems.
BACKGROUND OF THE INVENTION
The power requirements for electrical and electronic systems being designed today are placing increasing demands upon power supply designs. The latest semiconductor devices call for lower and lower supply voltage levels. The typical 5 V supply has been reduced to 3.3 V for many components. Many semiconductor devices already available require an even lower supply voltage of 2.8 V such as memory devices.
A high level block diagram illustrating an example of a prior art power supply distribution system in an electronic device is shown in FIG.
1
. The power supply distribution system, generally referenced
200
, comprises a power supply
202
, power supply wires or cables
204
, sense wires
206
for voltage feedback, distribution bus
208
and a plurality of printed circuit cards (PCBs)
210
,
212
.
The power supply
202
receives an input voltage from a source of electrical power and functions to generate an output voltage which is distributed to the power distribution bus
208
via cables
204
. Cables
206
comprise sense wires to provide voltage feedback to the power supply
202
. The power supply
202
utilizes the feedback voltage in maintaining a stable output voltage.
Typical systems comprise a plurality of PC boards that connect to a backplane via a modular connector. For example printed circuit board
210
connects to the power distribution bus, i.e., the typically the backplane, via connector
220
. Similarly, printed circuit board
212
connects to the power distribution bus via connector
222
.
On some printed circuit boards, also termed plug-in boards or modules, electrical power is delivered directly to the board once the board
210
is seated in the connector
220
. The electrical load placed on the power supply
202
is represented by the load block
211
on printed circuit board
210
.
On other printed circuit boards electrical power is switched on the board itself. Printed circuit board
212
is an example of such a type of board. After the board
212
is seated in the connector
222
, electrical power flows to the load
213
only when switches
215
are closed. In this case, electrical power to the plug-in modules like module
213
is controlled by switching devices such as switches
215
on board
212
. Typically, the unit housing the distribution system
200
comprises a central control unit (not shown) which functions to control electrical power to the modules. Once a new module is installed in the system, for example, a request is made to the central control unit to activate the new module. Upon receiving the request, the central control unit examines the functional parameters of the particular module and if the parameters are within predetermined tolerances, the central control unit switches on electrical power to the new plug-in module.
The switching device
215
may comprise any suitable switch such as an electromechanical relay, solid sate relay, transistor or other controllable switching device.
The prior art electrical power distribution scheme described above, however, fails to deliver electrical power with sufficient accuracy when the required voltage levels begins to drop, for example, to 3.3 V and less. This is a major disadvantage especially considering that, the current trend in electronic technology is to operate electronic components at lower and lower voltages, e.g., 3.3 V +/−5%, 2.8 V +/−5% or lower. At such low voltage values, the current needed to be supplied is fairly large while the permitted variability of the voltage supply is only a few tens of millivolts. Even a small modest impedance naturally existent in the copper traces and connectors making up the power distribution path will cause voltage drops much larger than tens of millivolts. To make matters worse, the impedance in the copper traces and the connectors is usually not a design parameter that can be adjusted arbitrarily. In actuality, the impedance in the copper trances and the connectors is typically unpredictable.
The following example illustrates the problems associated with the prior art power distribution system. Consider a plug-in module that consumes 100 W which at 3.3 V draws approximately 30 A. An impedance of 10 m&OHgr; would generate a drop of approximately 300 mV. This voltage drop is already almost twice as large as the 5% tolerance of 165 mV. In another example, if one considers a power FET, the typical R
DS
(On) impedance is approximately 4 m&OHgr;. A current of 40 A yields a voltage drop of 160 mV which almost equals the 3.3 V 5% tolerance. Further, higher impedances, lower supply voltages and tighter tolerances only worsen the problem.
SUMMARY OF THE INVENTION
The present invention in a power switching and voltage regulation system that utilizes the conventional switching element is a new way. In prior art approaches, the switching element is configured to present a minimal impedance with zero impedance being ideal. The system of the present invention, in contrast, utilizes the switching element to impose an impedance in a controlled manner. The power source supplying an input DC voltage is intentionally set to a higher voltage than the level required by the plug-in module. The voltage supplied is required to be sufficiently high such that the voltage delivered to the plug-in module, i.e., the load, exceeds the maximum permitted voltage level of the voltage required by the particular plug-in module.
Once the switching device is turned on, the switching element exerts an impedance which functions to drop the voltage supplied to the load to the required value. The impedance is generated in accordance with a feedback control signal. The drop in voltage is achieved in accordance with a reference signal input to a comparison circuit such as an operational amplifier.
Two embodiments of the present invention are presented. The first embodiment discloses a system wherein a plurality of DC output voltages are generated in which all the output voltage levels are the same. The second embodiment also discloses a system wherein a plurality of DC output voltages are generated however the level of each output voltage is independent of the others.
There is therefore provided in accordance with the present invention a power switching and voltage regulation system for providing regulated electrical power to at least one plug-in module, the system comprising a voltage regulator coupled to a source of electrical power, the voltage regulator for generating an intermediate supply voltage, an on/off control unit for receiving an on/off command from an external source, a reference voltage generator for generating a reference voltage, the reference voltage regulator responsive to an output signal produced by the on/off control unit and regulation means for providing a controlled impedance which functions to regulate the intermediate supply voltage so as to provide an output voltage at a predetermined level to the plug-in module.
The system further comprises a fuse in series with the intermediate supply voltage output from the voltage regulator. In addition, the regulation means comprises an off state wherein electrical power to the plug-in module is turned off and an on state wherein a controlled impedance is placed in series with the intermediate supply voltage so as to generate the output voltage to the plug-in module.
Further, the regulation means comprises on/off control means for either turning electrical power to the plug-in module off or for enabling a controlled impedance and a controlled impedance placed in series with the intermediate supply voltage, the controlled impedance responsive to the on/off control means so as to maintain the output voltage at a predetermined level.
The controlled impedance may comprise a switching device, a semiconductor transistor or a semiconductor field effect transistor (FET). The regulation means compr
Ater Dan
Ben-Meir Samuel
3Com Corporation
Patel Rajni Kant D.
Weitz David J.
Wilson Sonsini Goodrich & Rosati
Wong Peter S.
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