Digital input power supply and method

• US 4,901,217 A
• Filed: 02/13/1989
• Issued: 02/13/1990
• Est. Priority Date: 12/01/1987
• Status: Expired due to Term

• Current Assignee: Apple Inc.
• Original Assignee: Apple Computer Incorporated (Apple Inc.)
• Inventors: Wilson, David
• Primary Examiner(s): BEHA JR, WILLIAM
• Application Number:
  US07/310,472
• Time in Patent Office: 365 Days
• Field of Search: 307/138, 307/261, 307/311, 361/245, 363/45, 363/126, 363/147, 328/26
• US Class Current: 363/126
• CPC Class Codes: G06F 1/26 Power supply means, e.g. regulation thereof for memories G11C
• CPC Class Codes: H02M 7/06 using discharge tubes without control electrode or semiconductor devices without control electrode

Abstract

A full-wave rectifier circuit is coupled to a pair of differential signal lines emanating from a computer. The differential signal lines which carry digital data information having a serial protocol scheme is tapped by the full-wave bridge rectifier to provide a power supply voltage to power various circuits coupled to the power supply. This scheme permits an interface unit to a serial protocol scheme of a computer to power itself from the data lines.

Claims

1. A circuit, coupled between a peripheral unit and a personal computer, for converting a differential digital signal originating from said personal computer, to a DC power supply voltage, switching between a first voltage and a second voltage, wherein said first voltage represents a first digital state and said second voltage represents a second digital state, comprising:

a pair of input terminals at a said circuit coupled to receive said differential digital signal from said personal computer;

a pair of output terminals from said circuit coupled to provide said DC power supply voltage;

rectifier means coupled between said input terminals of said circuit and said output terminals of said circuit for providing conversion of said differential digital signal to said DC power supply voltage;

said personal computer having output means to send said differential digital signal to said circuit;

said differential digital signal has said first and second voltages at approximately equal magnitude about a reference value, so as to provide a substantially continuous DC power supply voltage from said output terminals of said circuit.

2. The circuit of claim 1 wherein said differential signal is for transferring of digital data between a personal computer and peripheral unit;

and wherein said circuit provides said DC power supply voltage without interfering with said transferring of digital data.

3. The circuit of claim 2 wherein said reference value is zero volts.

4. The circuit of claim 2 wherein said transferring of digital data is compatible with RS-422 protocol.

5. A circuit, coupled between a peripheral unit and a personal computer, for converting a differential digital signal, originating from said personal computer which is used to transfer data, to a DC power supply voltage, said differential digital signal being switched between first and second voltages which correspond to first and second digital states, respectively, comprising;

a pair of input terminals at said circuit coupled to receive said differential signal, wherein said differential digital signal switches between a positive voltage and a negative voltage, but magnitude of said positive and negative voltages are approximately equal about a zero reference;

a pair of output terminals from said circuit coupled to provide said DC power supply voltage as an output;

a first diode coupled between a first of said pair of input terminals and a first of said pair of output terminals;

a second diode coupled between a second of said pair of input terminals and said first of said output terminals;

a third diode coupled between said second of said input terminals and a second of said pair of output terminals;

a fourth diode coupled between said first of said input terminals and said second of said output terminals;

wherein said four diodes operate to function as a full-wave rectifier rectifying said differential digital signal to provide said substantially continuous DC power supply voltage;

said personal computer having output means to send said differential digital signal to said circuit;

whereby a source of power is provided at the output terminal of said circuit, by said differential digital signal originating from said output means of said personal computer.

6. The circuit of claim 5 wherein said differential digital signal is compatible with RS-422 protocol.

7. The circuit of claim 6 wherein said differential digital signal switches between -3 volts and +3 volts to provide approximately +5 volts DC from said pair of output terminals.

8. The circuit of claim 7 wherein a filter capacitor is coupled across said output terminals to reduce ripple of said DC power supply voltage.

9. The circuit of claim 5 further including a pair of output signal lines coupled to said pair of input terminals to output said differential digital signal.

10. The circuit of claim 8 further including a pair of output signal lines coupled to said pair of input terminals to output said differential signal.

11. A method of coupling a full-wave rectifier circuit between a peripheral unit and a personal computer and for converting a differential digital signal, which originates from an output means of said personal computer, to a continuous DC power supply voltage, including the steps of;

coupling said output means of said personal computer to differential digital signal lines;

coupling input terminals of said full-wave rectifier circuit to other end of said differential signal lines;

providing data transfer between said personal computer and said full-wave rectifier circuit across said differential digital signal lines;

said full-wave rectifier circuit receiving said differential digital signal at said input terminals, rectifying said differential digital signal to provide a substantially continuous DC power supply voltage from said output terminals of said full-wave rectifier circuit.