LCD display precharge regulator circuit

Details LCD display precharge regulator circuit LCD display precharge regulator circuit

1994-01-28

1995-06-13

Callahan, Timothy P.

Miscellaneous active electrical nonlinear devices, circuits, and

Specific identifiable device, circuit, or system

With specific source of supply or bias voltage

327540, H01J 1982

Patent

active

054246733

ABSTRACT:
An LCD precharge regulator circuit providing current directly from the input battery voltage to precharge the LCD display. A first switch activates a precharge regulator coupled to the unregulated DC input voltage, to supply the power for the initial current surge from the DC input to charge the LCD display. The precharge regulator includes a transistor and a biasing circuit. The biasing circuit initially turns the transistor fully on, but increasingly biases the transistor off as the LCD display charges to just below the operating voltage of the LCD display. A delay circuit activates a second switch after the LCD display is substantially charged, where the second switch connects the supply voltage from the DC/DC converter to the LCD display. At that point, the transistor is biased off, isolating the LCD display from the DC input voltage. Thus, the supply voltage need only sustain the charge on the LCD display after being substantially charged. Low power series resistors are provided to serve as a fuse, which fail to an open circuit condition, isolating the LCD display from high input voltage levels in the event of excessive current flowing into an overvoltage Zener diode.

REFERENCES:
patent: 4529890 (1985-07-01), Kobayashi et al.
patent: 4565960 (1986-01-01), Takata et al.
patent: 4617473 (1986-10-01), Bingham
patent: 4686388 (1987-08-01), Hafner
patent: 5023476 (1991-06-01), Watanabe et al.
patent: 5187396 (1993-02-01), Armstrong, II et al.
patent: 5272393 (1993-12-01), Horiguchi et al.

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