Browse Prior Art Database

Application of Threshold Switches to Limit Standby Energy Loss

IP.com Disclosure Number: IPCOM000028020D
Original Publication Date: 2004-Apr-19
Included in the Prior Art Database: 2004-Apr-19
Document File: 7 page(s) / 67K

Publishing Venue

Motorola

Related People

Roger L. Franz: AUTHOR

Abstract

Standby energy losses are reduced by application of threshold switches. A typical voltage-controlled threshold switch remains in a state of low conductance until reaching a specific value of applied potential, above which it becomes highly conducting. This function is sometimes called bistability, or negative differential resistance (NDR). For voltage controlled threshold switches, many types of materials may be used in their fabrication, including the chalcogenides (periodic table VIa elements including Se and Te), other types of non-crystalline or amorphous glasses, various III-V semiconductors and compound semiconductors including GaN, and organic semiconductors. Application to one of today’s most pressing problems with increasing standby losses in ultra large scale integrated circuits (ULSI) is explained.

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Application of Threshold Switches to Limit Standby Energy Loss

By Roger L. Franz

Abstract

Standby energy losses are reduced by application of threshold switches. A typical voltage-controlled threshold switch remains in a state of low conductance until reaching a specific value of applied potential, above which it becomes highly conducting. This function is sometimes called bistability, or negative differential resistance (NDR). For voltage controlled threshold switches, many types of materials may be used in their fabrication, including the chalcogenides (periodic table VIa elements including Se and Te), other types of non-crystalline or amorphous glasses, various III-V semiconductors and compound semiconductors including GaN, and organic semiconductors. Application to one of today’s most pressing problems with increasing standby losses in ultra large scale integrated circuits (ULSI) is explained.

Nature of the Problem

Standby energy loss has for years been a problem with wall-mounted transformer power supplies that remain in an “on” state, using electrical energy, even when no load is applied. The standby losses of a single such unit that is connected to normal house current supply may easily be on the order of 1W. Continuous operation of a single supply for one year consumes 9kW. When multiplied by the number of such supplies per household, the wasted energy on a global scale is significant.

Standby losses have also become critical in developing ULSI devices with low power requirements. Leakages from many thousands of transistors per device contribute substantially to current consumption and heat dissipation. As more transistors are integrated into ULSI devices, and gate oxide thickness continue to be reduced, the magnitude of this leakage has increased dramatically. In particular, portable products like hand-held phones and laptop computers are limited by battery life, and customers would be pleased if standby energy waste could be reduced as much as possible to increase the operating time of these products.

Performance and Selection of Switch Type

Threshold switches may be either current controlled and voltage controlled. As shown in Fig. 1, their operating curves are N-shaped and S-shaped, respectively. A thyristor is an example of a current-controlled switch. Addition of a current-activated threshold switch in series with the transformer primary would greatly reduce these standby losses. Below a threshold, the switch effectively turns off the leakage through the transformer primary. When a load is applied, the current immediately increases until the threshold switch exceeds its threshold, at which time it switches on and remains on as long as the load is applied. When the load is removed, the threshold switch falls below its threshold and returns to its off state. While Fig. 1 shows Direct Current (DC) curves, it is well known that threshold switches may function with Alternating Current (AC) with dynamic switching. Note that a co...