Large signal gain modifier circuit

Details Large signal gain modifier circuit Large signal gain modifier circuit

1999-08-19

2001-01-23

Han, Jessica (Department: 2838)

Electricity: power supply or regulation systems

Output level responsive

Using a three or more terminal semiconductive device as the...

C323S276000

Reexamination Certificate

active

06177784

ABSTRACT:

TECHNICAL FIELD
The present invention relates to feedback circuits for error amplifiers requiring fast transient response and, more particularly, to a gain modifier circuit for reducing voltage transients due to large step loads commonly associated with communications satellites having time division multiple access (TDMA) operation.
BACKGROUND OF THE INVENTION
Communications satellites with TDMA operation often experience significant bus voltage transients induced by repetitive large step load increases or decreases. These load transients can occur when, for example, a satellite having at least two power sources switches from using one source such as a solar array to another source such as a battery. Currently, to reduce the effects of the transient voltages, the gain/bandwidth of the feedback loop is increased to improve the power controller response time.
There are several disadvantages associated with the conventional scheme of increasing the feedback loop gain or bandwidth. Specifically, there are limitations on how much the feedback loop gain or bandwidth can be increased without impacting feedback loop stability. The amount of feedback loop gain/bandwidth is usually limited by the L-C comer of the power converter, the right half-plane zero, and the power converter switching frequency. In addition, to significantly increase the gain/bandwidth of the feedback loop, the feedback compensation is often complicated. For example, average current mode control may be necessary to increase the loop gain.
DISCLOSURE OF THE INVENTION
Accordingly, it is an object of the present invention to provide an improved feedback loop gain control circuit having improved stability and response time.
According to the present invention, the foregoing and other objects and advantages are attained by a feedback loop gain modifier circuit comprising two (2) diodes and a resistor coupled and parallel with a resistor in the AC feedback path of an amplifier. The diodes are connected such that one diode conducts on a voltage bus overshoot and the other diode conducts on a voltage bus undershoot. In this manner, during large step load transients, one of the gain modifier circuits diodes conducts thereby coupling the resistors in parallel resulting in a modified the gain/bandwidth of the feedback loop.
An advantage of the present invention is that the feedback gain modifier circuit does not affect small signal feedback loop stability because it is only activated when a large transient is present. In other words, the feedback loop can be stable in a large signal sense while the small signal loop stability is not affected, due to the non-linearity of the converter loop gain between small and large signals. Another advantage is that the feedback gain modifier circuit is a simple diode-resistor network. In addition, although the feedback gain modifier circuit is located in the bus voltage sense path, it does not affect the DC operating point of the power converter.
Other objects and advantages of the invention will become apparent upon reading the following detailed description and appended claims, and upon reference to the accompanying drawings.


REFERENCES:
patent: 3967219 (1976-06-01), Dolby
patent: 5777866 (1998-07-01), Jacobs et al.
patent: 6009000 (1999-12-01), Siri

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