Self-powered computer accessory device for power extraction from attached data signals and method of operating thereof

• US 5,438,678 A
• Filed: 03/23/1994
• Issued: 08/01/1995
• Est. Priority Date: 03/23/1993
• Status: Expired due to Fees

• Current Assignee: Smith, Peter L.
• Original Assignee: Smith, Peter L.
• Inventors: Smith, Peter L.
• Primary Examiner(s): Ray, Gopal C.
• Application Number:
  US08/035,934
• Time in Patent Office: 496 Days
• Field of Search: 395/750, 395/325, 395/200, 364/707, 307/261, 307/66, 340/310 A, 363/126
• US Class Current: 713/300
• CPC Class Codes: G06F 1/26 Power supply means, e.g. regulation thereof for memories G11C

Abstract

A self-powered intelligent computer accessory device has a serial data input port and a parallel data output port and is used for interconnection from computer to computer and between a computer and a peripheral device. The accessory device uses a full wave diode bridge to generate bipolar supply voltages referenced to ground from the serial data port to power a microprocessor of the accessory device. A power extraction circuit is provided on the output side of the microprocessor for extracting power from standard pull-up resistors within the peripheral device to power an output buffer circuit. The period of time in which power is extracted from the pullup resistors is maximized by using an enable control signal from the microprocessor to ensure that the output buffer circuit is only driving the external peripheral device during the output data strobe sequence and at all other times is not consuming power. The buffer circuit is constructed and controlled such that it is capable of driving the load of the external peripheral device but draws virtually no power in performing this task.

Claims

1. A self-powered computer accessory device for extracting operating power from attached signals, the device comprising:

a serial data input port;

a parallel data output port;

a microprocessor for processing data passing between said input port and said output port;

a diode circuit between said data input port and said microprocessor for generating bipolar voltages from serial data received at said input data port and providing operating power to said microprocessor;

a parallel output buffer circuit coupled between said microprocessor and said data output port;

a power extraction circuit connected to signal lines of said data output port for deriving unipolar voltages from a peripheral device connected to said data output port,

said unipolar voltages having different voltage levels from said bipolar voltages and providing power for driving said output buffer circuit; and

a level translation circuit between said microprocessor and said buffer circuit and including, for each of said signal lines, a driver provided in said microprocessor, a receiver provided within said output buffer circuit and a resistor between each driver and each corresponding receiver, wherein each receiver has a low switching threshold which is sufficiently below maximum levels of said bipolar voltages so that said level translation circuit facilitates reliable data transfer from said input port to said output port despite said different voltage levels.

2. An accessory device as defined in claim 1, wherein said power extraction circuit comprises resistors and diodes connected to said signal lines, respectively, and a capacitor for receiving charge from said resistors and diodes depending on a voltage on said capacitor and a voltage on a respective signal line.

3. An accessory device as defined in claim 1, further comprising means for providing a control signal from said microprocessor to said buffer circuit for maximizing the time during which said power is derived from the peripheral device to control said buffer circuit so as to enable said buffer circuit only to drive said peripheral device during an output data strobe sequence and disable said output buffer circuit to thereby prevent said output buffer circuit from consuming power at all other times.

4. A method for extracting operating power from attached signals in a self-powered computer accessory device including a serial data input port, a parallel data output port, a microprocessor between said input port and said output port, and an output buffer circuit, the method comprising the steps of full wave rectifying an incoming data signal input to said input port to generate positive and negative supply voltages to power said microprocessor;

deriving supply voltages positive in respect to ground only from a peripheral device connected to said output port to drive said buffer circuit by said supply voltages;

directly coupling data signals from said microprocessor to said output buffer circuit;

providing in said device a power extract circuit and a level translation circuit each coupled to said buffer circuit; and

controlling said output buffer circuit by said power extraction circuit and said level translation circuit so that virtually no power is consumed in driving data to the peripheral device.