Transformerless LED digital alarm clock
AssigneeGTC Properties, Inc.
InventorsThomas G. Guyett, Michael H. Reeves, Stephen B. Hobbs
Life of this patent
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Abstract
A transformerless LED digital display clock circuitry using AC line voltage as a primary source of power is disclosed. The AC line voltage is substantially reduced to around 10 volts or less and then rectified to provide DC power to the quartz analog clock. Also included is a NiCad battery circuitry used as a power backup and to allow for occasional but high current using devices. The LED digital display is made up of four separate "digit" displays each independently controlled by four separate cathode outputs from a microprocessor.
Claims15
A transformerless LED digital clock circuitry using AC line voltage as a source of power comprising:
- a pair of line terminals for receiving a source of single phase AC power having a line voltage level of between about 100 and 225 volts;
- a rectifier having a pair of inputs connected through said pair of line terminals to said source of single phase AC power and further including positive and negative outputs for providing a rectified power output;
- a voltage divider series circuit connected between one of said line terminals and one of said pair of inputs of said rectifier, said series circuit including a series connected resistor and a capacitor, said resistor and capacitor selected to substantially drop the voltage of said received AC power;
- a capacitor connected across said positive and negative outputs of said rectifier to filter said rectified power output;
- a diode circuit connected across said positive and negative outputs of said rectifier to clamp said rectified and filtered power output at a DC voltage of between about 3.6 VDC and 5.0 VDC for use as a low voltage DC power source;
- a positive DC output terminal connected to said positive output of said rectifier and a negative DC output terminal connected to said negative output of said rectifier;
- a source of clocking pulses;
- an LED display comprised of at least four individually controlled single digit displays, each of said single digit displays including a multiplicity of LED's for forming at least one selected number between 0 and 9, each of said LED's including a cathode and a anode;
- and
- a microprocessor connected to said source of clock pulses and across said low voltage DC power, said microprocessor providing at least four cathode outputs at four separate non-overlapping predetermined periods of time, one each of said cathode outputs connected to the LED cathodes of one of said four single digit displays, and said microprocessor further providing a multiplicity of anode outputs, specific ones of said multiplicity connected to specific LED anodes of each of said four single digit displays.
Dependencies are inferred from the claim text.