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Integrated current source feedback and current limiting element

An intrinsically safe circuit and power supply technology, applied in circuit devices, emergency protection circuit devices, emergency protection circuit devices for limiting overcurrent/overvoltage, etc., can solve problems such as increasing voltage loss, reduce the number of components, reduce Low cost and low voltage loss

Inactive Publication Date: 2007-05-30
MICRO MOTION INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

One problem with adding a current limiting circuit is that the current-to-voltage conversion increases the output resistance, adding to the voltage loss after losing the voltage necessary to meet intrinsic safety standards

Method used

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  • Integrated current source feedback and current limiting element
  • Integrated current source feedback and current limiting element
  • Integrated current source feedback and current limiting element

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Embodiment Construction

[0087] The power supply of the present invention is such that the total output resistance does not exceed that required to prevent ignition of explosives in hazardous environments. A general intrinsically safe power supply 100 is shown in FIG. 1 to illustrate the difference between a power supply according to the present invention and a general intrinsically safe power supply.

[0088] The prior art intrinsically safe power supply 100 delivers sufficient power to the load for proper operation while limiting worst case voltage, current and power levels so as not to ignite hazardous materials. The voltage limiting circuit 101 limits the load voltage. In power supply 100 , the voltage limiting circuit is a zener diode Z1 connected between paths 110 and 120 . Those skilled in the art will recognize that more than one zener diode can be connected between paths 110 and 120 to limit the voltage. For purposes of discussion, voltage limiting circuit 101 limits the voltage across a lo...

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Abstract

A circuit for supplying power to an intrinsically safe circuit having a power supply and output terminals includes an integrated current source feedback and current limiting element. Voltage limiting circuitry between the power supply and the output terminals limits the voltage across a load. Current limiting circuitry includes barrier resistors which convert current to voltage for input to an operational amplifier comparing a reference voltage with the voltage level representing the load current and providing a control input signal to a transistor for limiting a current applied to the load.

Description

technical field [0001] The present invention relates to power supplies for intrinsically safe loads. More particularly, the present invention relates to circuitry that limits the current delivered to a load in order to comply with intrinsic safety standards. Background technique [0002] Electronic devices are often used in hazardous environments where explosives are present. A common problem is that sparks or heat from electronic devices may ignite explosives. Therefore, those who manufacture electronic devices for use in such hazardous environments must provide some protection against ignition of explosives by such electronic devices. [0003] One such means of protection is to establish intrinsic (or inherent) safety of the circuit. The management coordinating organizations that formulate intrinsic safety standards are, for example, Underwriters Laboratories (UL) in the United States, CENELEC in Europe, the Canadian Standards Association (CSA) in Canada, and the Indust...

Claims

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Application Information

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IPC IPC(8): H02H9/02G05F1/569G05F1/66H02H9/00H02H9/04
CPCG05F1/66H02H9/008H02H9/02
Inventor W·M·曼斯菲尔德
Owner MICRO MOTION INC