Current-controlled on/off power line switching of electrical devices

• US 4,675,537 A
• Filed: 04/01/1985
• Issued: 06/23/1987
• Est. Priority Date: 04/01/1985
• Status: Expired due to Fees

• Current Assignee: Voltec Pte Limited
• Original Assignee: Voltec Pte Limited
• Inventors: Mione, Lawrence J.
• Primary Examiner(s): Shoop, Jr., William M.
• Assistant Examiner(s): Ip, Shik Luen Paul
• Application Number:
  US06/718,663
• Time in Patent Office: 813 Days
• Field of Search: 307/38, 307/39, 307/43, 307/42, 307/71, 307/73, 307/129, 307/130, 307/131, 307/132 R, 307/132 E, 307/112, 307/141, 307/113, 307/141.4, 307/116, 307/125, 361/91, 361/92, 361/93, 361/111, 361/90
• US Class Current: 307/38
• CPC Class Codes: G06F 2200/261 PC controlled powerstrip
• CPC Class Codes: H01H 47/001 Functional circuits, e.g. logic, sequencing, interlocking circuits
• CPC Class Codes: H01H 47/18 for introducing delay in the operation of the relay short-circuited conducting sleeves, bands or discs H01H50/46
• CPC Class Codes: Y02D 10/00 Energy efficient computing, e.g. low power processors, power management or thermal management

Abstract

A switching control circuit has first and second output terminals, the first output terminal being connected by way of a control resistor to one of a pair of input terminals which, in use of the circuit are connected to an electrical power source, the second output terminal being connected to the other input terminal. A sensing and delay portion of the circuit is connected across the resistor and, in response to current flowing through the resistor when the power switch of a first electrical device, such as a disc drive, connected to the input terminals is initially turned on, energizes a relay after a predetermined time delay elapses from the time that the resistor current reaches a given threshold value, the energized relay serving to connect one or more pairs of other output terminals of the circuit across the pair of input terminals, so that source power will then be supplied via the relay to the other output terminal pairs and to any other electrical devices, such as a monitor, printed and computer, whose power input terminals are respectively connected thereto. Following turn-off of the power switch, the same circuit portion deenergizes the relay after a second predetermined time delay elapses from the time that resistor current diminishes to a second given threshold value, so that source power to the other electrical devices will cease. Use of a high gain amplifier at the input of the sensing and delay portion of the circuit sharply reduces the power dissipation required of the resistor for any given threshold value of current therethrough, thus providing consequent cool operation and avoiding fuse or other line protection.

Claims

1. A switching control circuit for electrical devices, comprising:

(a) a pair of input terminals which, in use of said circuit, are connected to a source of power for electrical devices whose switching on and off is to be effected;

(b) a control resistor;

(c) a first pair of output terminals, one terminal of which is connected by way of said control resistor to one of said input terminals, the other output terminal being connected to the other input terminal, said output terminals to be connected in power supplying relation to a first electrical device having an on/off power switch;

(d) a second pair of output terminals;

(e) energizable means responsive to energization thereof for connecting said second pair of output terminals across said pair of input terminals; and

(f) sensing and delay means including a high gain amplifier having an input connected across said control resistor for producing a voltage output

in response to current caused to flow through said control resistor when the first electrical device is connected to said first pair of output terminals and its said on/off power switch is initially turned on, said sensing and delay means further including circuitry coupled to said high gain amplifier and responsive to said voltage output thereof for energizing said energizable means after a predetermined time delay elapses from the time that said high gain amplifier voltage output reaches a given threshold value, whereby power from said power source will then be supplied via said energizable means to said second pair of output terminals and to any second electrical device whose power input terminals are connected thereto.

2. A switching control circuit according to claim 1, wherein said energizing circuitry is additionally responsive to the voltage output of said high gain amplifier for deenergizing the energizable means after a second predetermined time delay elapses from the time that the high gain amplifier voltage output has diminished to a second given threshold value lower than the first given threshold value following turn-off of said power switch, whereby power from said power source will then cease to be supplied via said energizable means to said second pair of output terminals and to any second electrical device whose power input terminals are connected thereto.

3. A switching control circuit according to claim 1, wherein at least one additional pair of output terminals are connected in parallel with said second pair of output terminals.

4. A switching control circuit according to claim 2, wherein at least one additional pair of output terminals are connected in parallel with said second pair of output terminals.