Miscellaneous active electrical nonlinear devices – circuits – and – Signal converting – shaping – or generating – Synchronizing
Reexamination Certificate
2000-07-20
2001-07-10
Lam, Tuan T. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Signal converting, shaping, or generating
Synchronizing
C327S198000, C327S538000
Reexamination Certificate
active
06259287
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to voltage regulator circuits in general and more particularly to low cost stable voltage regulators controlled by a constant current generator having a voltage regulator device and having a low voltage inhibit circuit.
2. Description of the Related Art
It is well known that microcomputers operating from regulated power supplies must be inhibited during both the power-up phase and also in the event that the DC power to the regulated power supply is interrupted or drops below a predetermined level. U.S. Pat. No. 5,313,112 issued on May 17, 1994 to Macks entitled “Low Voltage Inhibiting Circuit For A Microcomputer” and is incorporated herein by reference, sought to find a low cost solution to achieving the desired functions. This patent required separate voltage regulating circuits. One circuit to provide the regulated supply voltage and another circuit to use as a comparison reference for the power on reset and the low voltage inhibit functions.
In U.S. Pat. No. 5,760,625 issued on Jan. 2, 1998 to Macks entitled “Low Cost Microcomputer Power Supply With Power On Reset And Low Voltage Inhibit Functionality” that is incorporated herein by reference, describes a five volt regulator with a reset circuit. This circuit is not robust to the swings in the power feed potential. In automotive applications the power feed is the vehicle battery which is subject to large variations in potential from 3 to 18 volts.
SUMMARY OF THE INVENTION
Still other times the power supply must be provided with a reset or inhibit function when the regulated supply is dropping below its regulated voltage. This voltage drop out occurs when the power feed in the vehicle drops below about six to eight volts. When the power feed drops below this level, the regulated supply will begin to supply less than its intended voltage. In the case that the regulated supply is providing power to a microcomputer, it is imperative that the reset or inhibit line be activated when the five volt regulator can no longer supply five volts. This function of activating the reset line under low output voltages from the five volt regulator is referred to as the “low voltage inhibit”.
It is therefore a principal advantage of the invention to provide low cost voltage regulator responsive to voltage swings of a power supply while maintaining a constant regulated voltage.
It is also a key advantage of the invention to maintain a constant regulated load current to the load during load current swings.
It is yet another advantage of the invention to generate a voltage inhibit signal for controlling an output load such as a microcomputer. The voltage inhibit signal responds to the input signal to the voltage regulator and the voltage generated by the regulating element to generate either one of two binary logic states.
These and other advantages will become apparent from a stable regulated voltage supply and low voltage inhibit supply for maintaining a regulated voltage to a load independently of the voltage input from the power supply. The stable regulated supply has an input for receiving a voltage signal from a power supply such as a battery. The output of the regulated supply is operatively connected to a load such as a microcomputer. A current amplifier voltage regulator is connected in circuit between the input and the output for supplying current to the load upon demand at a regulated voltage.
A zener diode is electrically connected in circuit between the input and a reference potential, such as ground. The zener diode has a zener voltage substantially equal to the desired output of the voltage regulator. A constant current generator is electrically connected in circuit with the zener diode and operates to maintain a specified current through the zener diode for operating the zener diode at its zener voltage. The constant current generator shunts all current in excess of the low-test current from the zener diode. The constant current generator controls the current amplifier voltage regulator to maintain its output at substantially the value of the zener voltage regardless of the current demand of the load.
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Lam Tuan T.
Mollon Mark
Nguyen Hiep
Visteon Global Technologies Inc.
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