Electricity: power supply or regulation systems – Output level responsive – Using a three or more terminal semiconductive device as the...
Reexamination Certificate
2000-01-28
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...
C323S285000, C323S351000
Reexamination Certificate
active
06201376
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is directed to an apparatus and method for establishing an operating parameter for electrical power supply apparatuses. The present invention is especially directed to an apparatus and method for establishing shutdown output current for DC-to-DC power converter apparatuses. In most contemporary DC-to-DC power converter apparatuses, there is an inherent current limit involved in the operation of the apparatus. That is, beyond a certain point, the power generated by the converter device becomes substantially constant, so as output or load current (I) increases, the output voltage (V) decreases. When this condition is reached, it is frequently desireable for the apparatus to turn off. Turning off is desireable because the low output voltage is not adequate for the load, and the increased output current can harm the DC-to-DC converter. It is desirable for DC-to-DC power converter apparatuses to be flexible in their applicability to various products. Such flexibility allows a manufacturer of such apparatuses to reduce the number of discrete apparatus models that must be offered in order to provide a product line that addresses a wide range of possible applications. One aspect of such desired flexibility is to provide users, or customers, with a capability to control the output current limit for DC-to-DC power converter apparatuses. That is, users of DC-to-DC apparatuses desire that they may set the current limit for the apparatus. Such control has been made available to users of such apparatuses in the past, but there are problems with such earlier offerings, especially at low output current levels.
Earlier solutions to providing customer, or user control of the current limit for DC-to-DC power converter apparatuses involved an estimating methodology that introduced significant error into the turn-off point of the apparatus and risked uncontrolled, and therefore unanticipated shut down of the apparatus. Such earlier solutions introduced an offset to a programming signal in order to avoid nuisance shut down occurrences at low current level settings. The offset thus introduced adversely affected the accuracy of the apparatus response over a significant range of operation.
There is a need for an improved user programmable adaptive current shutdown method and apparatus for use with power supply apparatuses. Such a method and apparatus is especially needed in connection with DC-to-DC power converters at low output current levels.
SUMMARY OF THE INVENTION
An apparatus for establishing an operating parameter, such as a shutdown circumstance, for a power supply device having an output. The apparatus comprises: (a) a first signal source; (b) a second signal source; (c) a third signal source; and (d) a state device. The first signal source is controllable for selectively generating a programming signal. The second signal source generates a load indicating signal and is connected with the power supply device. The third signal source generates an offset signal. The state device has a first input and a second input and changes state when the first input has a predetermined relationship with the second input. The first input is determined by relative values of the programming signal and the offset signal. The offset signal may be a constant value or it may be related with the output of the power supply device. The power supply device shuts down when the state device changes state in a predetermined manner.
The method of the present invention comprises the steps of: (a) providing, in no particular order, the following signals: (1) a programming signal appropriate for the shutdown circumstance; and (2) an offset signal; (b) applying a signal representative of the output to a first input of a state device; (c) substantially simultaneously with step (b), applying one of the following signals to a second input of the state device: (1) the programming signal; or (2) a combination of the programming signal and the offset signal; and (d) changing state of the state device when the first input has a predetermined relationship with the second input. The shutdown circumstance is effected when the state changes in a predetermined manner.
The invention is particularly suited for user-programming of output current limits for DC-to-DC power converter devices. Present such programming capabilities employing prior art apparatuses and methods introduce programming errors because a fixed offset voltage is imposed upon programming voltages in order to avoid a situation where the power converter device is “locked out” and cannot turn on.
It would be useful to have an apparatus and method for programming DC-to-DC power converter shutdown current parameter levels in a manner that diminishes programming errors and still avoids placing a power converter device in a “lock out” state where it is unable to turn on.
It is, therefore, an object of the present invention to provide an apparatus and method for programming a DC-to-DC power converter's shutdown current with diminished programming errors as compared with prior art apparatuses and methods.
It is a fuirther object of the present invention to provide an apparatus and method for programming a DC-to-DC power converter's shutdown current without placing the power converter in a “lock out” state, unable to turn on.
Further objects and features of the present invention will be apparent from the following specification and claims when considered in connection with the accompanying drawings, in which like elements are labeled using like reference numerals in the various figures, illustrating the preferred embodiments of the invention.
REFERENCES:
patent: 4823070 (1989-04-01), Nelson
Mondul Donald David
Mweene Loveday Haachitaba
Laxton Gary L.
Lucent Technologies - Inc.
Wong Peter S.
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