Optical response semiconductor switch with short circuit load protection

A load protection, semiconductor technology, applied in the field of light-responsive semiconductor switches, can solve problems such as unsatisfactory

Inactive Publication Date: 2004-04-28
MATSUSHITA ELECTRIC WORKS LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Therefore, such known switches impose restrictions on the design of the circuit and are also unsatisfactory in terms of interrupting overload independently of the current-generating capacitance of the optoelectronic element

Method used

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  • Optical response semiconductor switch with short circuit load protection
  • Optical response semiconductor switch with short circuit load protection
  • Optical response semiconductor switch with short circuit load protection

Examples

Experimental program
Comparison scheme
Effect test

no. 1 example

[0044] First embodiment (Fig. 1)

[0045] Referring to FIG. 1, it shows a photoresponsive semiconductor switch according to a first embodiment of the present invention. The switch is used in combination with the light emitting diode 1 to form a photorelay for connecting and disconnecting the load 2 with the power source 3 . The switch comprises photoelectric elements 10 in the form of an array of photodiodes, which generate electricity when light is absorbed from light emitting diodes 1 . This electrical energy gives an operating voltage that decreases as the current to the photodiode array 10 increases. The operating voltage is applied to activate an output switching transistor 20 in the form of an n-channel enhancement metal oxide field effect transistor (MOSFET) whose gate-source is connected across the photodiode array 10 . The drain and source of the output MOSFET 20 are respectively connected to an output terminal 21 suitable for connection to a load circuit consisting...

no. 2 example

[0052] Second embodiment (Fig. 4)

[0053] Referring to FIG. 4, it shows a photoresponsive semiconductor switch according to a second embodiment of the present invention. The switch of this embodiment is designed for a load circuit powered by an AC source 3A to a load 2, and is identical to the first embodiment except for the use of an additional output MOSFET 22, and an additional current sensing resistor 33 and an additional sensor MOSFET 34 in the overload sensor 30A. Example is the same. Like elements are designated by like reference numerals with an "A" suffix. The additional output MOSFET 22 is connected in series with the output MOSFET 20A between the output terminals 21A, the sources of the MOSFETs 20A and 22 are connected to each other, and the gates of the MOSFETs 20A and 22 are connected together to receive the operating voltage of the photodiode array 10A. An additional resistor 33 is connected in series with terminal 31A between output terminals 21A, providing a...

no. 3 example

[0057] The third embodiment (Fig. 7)

[0058] Referring to FIG. 7, there is shown a third embodiment of an optically responsive semiconductor switch of the present invention which is identical to the first embodiment except that a bypass MOSFET 35 is included in the overload sensor 30D. Like elements are designated by like reference numerals with a "D" suffix. The source-drain of the bypass MOSFET 35 is connected in series with the current response resistor 31D, connected to both ends of the drain-source of the output MOSFET 20D, and its gate is connected to the gate of the output MOSFET 20D to jointly receive the operating voltage from the photodiode array 10D . Bypass MOSFET 35 and resistor 31D form a high resistance path across output MOSFET 20D so that only a small portion flows through resistor 31D for overload detection, while most of the load current flows through output MOSFET 20D. When overload sensor 30D detects an overload, latch circuit 40D is responsive to keepi...

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PUM

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Abstract

The present invention relates to an improved light responsive semiconductor switch with shorted load protection capable of successfully interrupting a load overcurrent. The switch includes an output transistor which is triggered by a photovoltaic element to connect a load to a power source thereof, and an overcurrent sensor which provides an overcurrent signal upon seeing an overcurrent condition in the load. A shunt transistor is connected in series with a current limiting resistive element across the photovoltaic element to define a shunt path of current flowing from the photovoltaic element through the current limiting resistive element away from the output transistor.

Description

technical field [0001] The invention relates to a light-responsive semiconductor switch with short-circuit load protection for optical propagation. Background technique [0002] Japanese Patent Publication Hei 11-163706 discloses a photoresponsive semiconductor switch used in optical transmission. Such a switch includes a photoelectric element that gives an operating voltage based on light absorbed from a light source, and an output transistor that is triggered by said operating voltage to become conductive for connecting a load to a source. To prevent the output transistor from being overloaded by accidental short-circuiting of the load, the switch includes an overload sensor to detect the overload condition and a shunt transistor that becomes conductive in response to the overload condition, allowing the current from the optoelectronic element leave the output transistor to turn off to interrupt the overload current. In addition, the switch includes a latch circuit respo...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H03K17/78H03K3/356H03K17/082H03K17/785
CPCH03K3/356H03K17/0822H03K17/785
Inventor 富井和志长浜英雄萩原洋右
Owner MATSUSHITA ELECTRIC WORKS LTD
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