Miscellaneous active electrical nonlinear devices – circuits – and – Signal converting – shaping – or generating – Amplitude control
Reexamination Certificate
2002-06-18
2003-12-02
Tran, Toan (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Signal converting, shaping, or generating
Amplitude control
C327S321000
Reexamination Certificate
active
06657475
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to voltage clamps and more specifically to a DC voltage bus clamp that provides protection from electrical current released from a load.
2. Discussion of the Prior Art
A load such as a DC motor will release electrical current when slowed or stopped. The electrical current released from the load may damage a power supply such as a rectified AC source or a DC source through a DC voltage bus. It appears that only complicated solutions exist for protecting the power source from damage due to reverse current.
Accordingly, there is a clearly felt need in the art for a DC voltage bus clamp that provides protection from electrical current released from a load without undue complexity.
SUMMARY OF THE INVENTION
The present invention provides a DC voltage bus clamp that provides protection from electrical current released from a load. The DC voltage bus clamp includes a transistor, a bleed resistor, and a pull-down diode. The transistor is placed in parallel with the load. If the power source supplies AC voltage, a filter capacitor is placed in parallel with the load. One end of the bleed resistor is connected to a positive terminal of the load and the other end of the bleed resistor is connected to a cathode of the pull-down diode. A gate or base of the transistor is connected to the other end of the bleed resistor. An anode of the pull-down diode is connected to ground and the cathode is connected to the gate or base of the transistor. A power resistor may be connected between the load and the transistor to help dissipate the electrical current discharged from the load. In a second embodiment of the DC voltage bus clamp, a hysteresis circuit is added to the DC voltage bus clamp to trigger the transistor suddenly. The hysteresis circuit includes a pull down transistor with a gate or base that is supplied with reverse electrical current from a slowed or stopped load. Capacitive and inductive filtering may be added to DC voltage bus clamp to prevent false triggering of the transistor.
A third embodiment of the DC voltage bus clamp includes the transistor, a resistor sensing circuit, the bleed resistor, and a sense resistor. The transistor is placed in parallel with the load. If the power source supplies AC voltage, a filter capacitor is placed in parallel with the bleed resistor. One end of the bleed resistor is connected to a positive terminal of the load. One end of the sense resistor is connected to ground and the other end is connected to the other end of the bleed resistor. The resistor sensing circuit is connected between the other end of the sense resistor and the gate or base of the transistor. A power resistor may be added between the load and the transistor to help dissipate the electrical current discharged when the load is slowed or stopped.
Accordingly, it is an object of the present invention to provide a DC voltage bus clamp that provides protection from electrical current released from a load without undue complexity.
These and additional objects, advantages, features and benefits of the present invention will become apparent from the following specification.
REFERENCES:
patent: 4186418 (1980-01-01), Seiler
patent: 5138192 (1992-08-01), Hsu
patent: 5861738 (1999-01-01), Becker-Irvin et al.
patent: 6064249 (2000-05-01), Duvvury et al.
patent: 6097235 (2000-08-01), Hsu et al.
patent: 6169439 (2001-01-01), Teggatz et al.
patent: 6445239 (2002-09-01), Zierhut
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