Battery-initiated touch-sensitive power-up

• US 5,249,298 A
• Filed: 12/28/1992
• Issued: 09/28/1993
• Est. Priority Date: 12/09/1988
• Status: Expired due to Fees

• Current Assignee: Dallas Semiconductor Corporation (Analog Devices, Inc.)
• Original Assignee: Dallas Semiconductor Corporation (Analog Devices, Inc.)
• Inventors: Bolan, Michael L., Little, Wendell L.
• Primary Examiner(s): RICHARDSON, ROBERT
• Application Number:
  US07/998,897
• Time in Patent Office: 274 Days
• Field of Search: 364/DIG. 1, 364/DIG. 2, 395/750, 365/229
• US Class Current: 713/340
• CPC Class Codes: G06F 1/24 Resetting means
• CPC Class Codes: G06F 1/30 Means for acting in the event of power-supply failure or interruption, e.g. power-supply fluctuations for resetting only G06F1/24
• CPC Class Codes: G06F 1/3203 Power management, i.e. event-based initiation of a power-saving mode
• CPC Class Codes: G06F 1/3209 Monitoring remote activity, e.g. over telephone lines or network connections
• CPC Class Codes: G06F 11/0754 by exceeding limits
• CPC Class Codes: G06F 11/1415 at system level

Abstract

A power-switching device (such as a gate-controlled TRIAC) is used to connect and disconnect a computer system'"'"'s power supply unit from the power-line connection. This power-switching device is controlled by a battery-powered circuit. The battery-powered circuit monitors a contact pad, and powers up the system when the user touches the contact. Thus, when the system is powered down, all parts of the system are disconnected from AC power.

Claims

1. A circuit, comprising:

(a) first and second power input nodes;

(b) an output node;

(c) a sense input node;

(d) a first switch between said output node and an internal node;

(e) a comparator with inputs connected to said first and second power input nodes and with output driving a second switch between said internal node and said first power input node, wherein (i) when a voltage at said first power input node exceeds a voltage at said second power input node, said second switch connects said internal node to said first power input node, but (ii) when said voltage at said first power input node is less than said voltage at said second power input node, said second switch disconnects said internal node from said first power input node;

(f) a detector with input connected to said sense input node and with output driving said first switch, wherein a voltage change at said sense node detected by said detector when said first switch disconnects said internal node from said output node drives said first switch to connect said internal node with said output node; and

(g) a timer coupled to said detector, said timer starting a time interval when said detector detects said voltage change, wherein said timer at the end of said time interval drives said first switch to disconnect when said comparator drives said second switch to disconnect.

2. The circuit of claim 1, wherein:

(a) said second power input node connects to said internal node through a diode.

3. The circuit of claim 1, further comprising:

(a) an AC to DC power supply with output connected to said first power input node, and with off-on control connected to said output node.

4. The circuit of claim 1, wherein:

(a) said detector includes (i) a flip-flop with a falling edge clock input connected to said sense node, Q output driving said first switch, and Q output driving a D input and (ii) a pullup for said sense node.

5. The circuit of claim 1, wherein:

(a) said timer includes a ring oscillator and a divider; and

(b) said comparator disables said oscillator when said voltage at said first power input node exceeds a voltage at said second power input node.

6. A system, comprising:

(a) a DC power converter with power input node, a power output node, and an off/on control node;

(b) a battery with a battery output node;

(c) a sense input node;

(d) a first switch between said off/on control node and an internal node;

(e) a comparator with inputs connected to said power output node and said battery output node and with output driving a second switch between said internal node and said power output node, wherein (i) when a voltage at said power output node exceeds a voltage at said battery output node, said second switch connects said internal node to said power output node, but (ii) when said voltage at said power output node is less than said voltage at said battery output node, said second switch disconnects said internal node from said power output node;

(f) a detector with input connected to said sense input node and with output driving said first switch, wherein a voltage change at said sense node detected by said detector when said first switch disconnects said internal node from said off/on control node drives said first switch to connect said internal node with said off/on control node and turn on said DC power converter; and

(g) said battery connects to said internal node through a diode.

7. A pushbutton power control system, comprising:

(a) a pushbutton coupled to clock a flip-flop with each activation of said pushbutton changing the state of said flip-flop;

(b) a battery coupled through a diode to an internal node;

(c) a power supply with an off/on control node and a power output node, wherein the voltage at said power output node exceeds that of said battery when said power supply is on;

(d) a first switch coupling said off/on control node to said internal node, the state of said flip-flop determining the setting of said first switch;

(e) a second switch coupling said power output node to said internal node, the setting of said second switch determined by the sign of the voltage difference between said battery and said power output node, with said switch connecting said power output node to said internal node when the voltage at said power output node exceeds that of said battery;

(f) wherein activation of said pushbutton when said power supply is off and said first switch is disconnecting said off/on control node and said internal node will clock said flip-flop and thereby connect said off/on control node to said internal node through said first switch and turn on said power supply and thereby connect said power output node to said internal node, and wherein a subsequent activation of said pushbutton will disconnect said off/on control node from said internal node and thereby turn off said power supply.

8. The system of claim 7, further comprising:

(a) a timing circuit coupled to reset said flip-flop to the state of said first switch disconnecting said internal and off/on control nodes when said timing circuit has been enabled for a predetermined time interval, said timing circuit disabled when said second switch connects said power output and internal nodes.