This application claims priority to Taiwan Patent Application No. 098106353 filed on Feb. 27, 2009, the disclosure of which is incorporated by reference herein in their entirety.
1. Field of the Invention
The present invention relates to a photo-coupler, and particularly, to a photo-coupler having a high operating voltage.
2. Descriptions of the Related Art
Photo-couplers are circuit safety devices which, when combined with a light emitting chip and a photo sensing chip, convert an electric signal into a light signal and then convert the light signal back into an electric signal. Photo-couplers can obviate bursts and other instable conditions from the source end and prevent consequent burning-out or failure of circuits at the receiving end when the electrical connection is made simply via a circuit.
As shown in
To block light from both inside and outside of the outer package 16, a large amount of filler must be filled in the plastic matrix to give it a black color. However, use of the filler changes the thermal expansion coefficient of the outer package 16 to a great extent. Therefore, an appropriate amount of filler must also be filled in the inner package 15 to make the thermal expansion coefficient of the inner package 15 approximately that of the outer package 16, so that an undue temperature rise and consequent deformation or damage of the inner package 15 and the outer package 16 due to a large difference in the thermal expansion coefficients therebetween can be avoided. Because of this, the inner package 15 is generally white colored and forced to have a low light transmittance. However, the low light transmittance of the inner package 15 further prevents the distance between the light emitting chip 12 and the light-sensing chip 13 from increasing, otherwise the light beam 14a from the light emitting chip 12 would experience an excessive loss when transmitting through the inner package 15 and the light-sensing chip 13 would fail to receive sufficient light that is necessary for converting the light signal into an electric signal.
Furthermore, the conventional photo-coupler 1 has an insulation voltage (VISO) substantially less than or equal to 5000 V, so the light emitting chip 12 and the light-sensing chip 13 must have a minimum distance at least ranging substantially from 0.4 mm to 0.6 mm to avoid point discharge. However, in case the operating voltage needs to be substantially higher than 8000 V, the minimum distance between the light emitting chip 12 and the light-sensing chip 13 must be substantially greater than 3.0 mm and the creepage distance must be substantially greater than 8.0 mm according to the safety regulations. Under such operating conditions, due to the extremely low light transmittance of the inner package 15, the light beam 14a emitted from the light emitting chip 12 would experience such an excessive loss that the light-sensing chip 13 might fail to convert the light signal into the electric signal normally, causing failure of the photo-coupler 1 to operate under such conditions.
It is important in the art to provide a photo-coupler capable of operating at a high voltage.
One objective of the present invention is to provide a photo-coupler capable of operating at a high voltage and obviating an excessive light loss that would cause operational failure of the photo-coupler.
The photo-coupler of the present invention comprises a light emitting chip, a light-sensing chip, a light-transmissive inner encapsulant package and an outer package. Both the light emitting chip and the light-sensing chip face towards a same direction, and are adapted to emit and receive a light beam respectively. The light-transmissive inner encapsulant package encloses the light emitting chip and the light-sensing chip, while the outer package encloses the light-transmissive inner encapsulant package and forms an interface with the light-transmissive inner encapsulant package for reflecting the light beam. The light-transmissive inner encapsulant package is formed with a reflective curved surface adjacent to the light emitting chip which, as enclosed by the outer package, is adapted to reflect and converge a first portion of the light beam to the light-sensing chip.
The detailed technology and preferred embodiments implemented for the subject invention are described in the following paragraphs accompanying the appended drawings for people skilled in this field to well appreciate the features of the claimed invention.
In references to both
The light emitting chip 22, after receiving an input electric signal, is adapted to generate and emit a first portion 24c, a second portion 24b and a third portion 24a of a light beam. After receiving the first portion 24c, the second portion 24b and the third portion 24a of the light beam, the light-sensing chip 23 converts them into an output electric signal and transmits the signals. The light-transmissive inner encapsulant package 25 encloses the light emitting chip 22 and the light-sensing chip 23, while the outer package 26 encloses the light-transmissive inner encapsulant package 25. With an interface 28 formed between the light-transmissive inner encapsulant package 25 and the white outer package 26, the outer package 26 reflects the first portion 24c, the second portion 24b and the third portion 24a of the light beam to the light-sensing chip 23 through the light-transmissive inner encapsulant package 25.
In the present invention, the light emitting chip 22 should be an infrared light emitting diode (IR LED), while the light-sensing chip 23 is a photo transistor. The material of the light-transmissive inner encapsulant package 25 preferably comprises epoxy resin, and to enhance the reflectivity, the material of the outer package 26 should preferably comprise an epoxy resin matrix and white TiO2 filler. Hence, with the above arrangement, the light-transmissive inner encapsulant package 25 encloses the light emitting chip 22 and the light-sensing chip 23, while the outer package 26 in turn encloses the light-transmissive inner encapsulant package 25. The white outer package 26 can effectively reflect the first portion 24c, the second portion 24b and the third portion 24a of the light beam from the light emitting chip 22 to the light-sensing chip 23. As compared to the light beam 14a in the conventional photo-coupler 1 which is transmitted through the white inner package 15, the first portion 24c, the second portion 24b and the third portion 24a of the light beam in the present invention are transmitted through the light-transmissive inner encapsulant package 25 with little loss between the light emitting chip 22 and the light-sensing chip 23. As a result, the distance D between the light emitting chip 22 and the light-sensing chip 23 is permitted to be enlarged to reinforce the insulation capability of the light-transmissive inner encapsulant package 25, thereby allowing the photo-coupler 2 of the present invention to withstand a higher operating voltage.
As shown in
In addition to the first portion 24c of the light beam being reflected and converged by the reflective curved surface 251 to the light-sensing chip 23, as shown in
In the most preferred embodiment of the present invention, the photo-coupler 2 is mounted with the direction 211 facing towards a circuit board 3 (i.e., both the light emitting chip 22 and the light-sensing chip 23 face towards the underside of the photo-coupler 2) to completely eliminate the effect of environmental light transmitted through the white outer package 26 on the light-sensing chip 23. Additionally, at least two lead frames 27a, 27b of the photo-coupler 2 of the present invention extend outward away from each other, with a plurality of pins 271 thereof extending also downwards to electrically connect with the circuit board 3. The light emitting chip 22 and the light-sensing chip 23 are disposed on the first lead frame 27a and the second lead frame 27b respectively to allow the light emitting chip 22 to receive the input electric signal and the light-sensing chip 23 to transmit the output electric signal. As will be readily appreciated by those of ordinary skill in the art, the first lead frame 27a and the second lead frame 27b may also extend towards a same direction instead.
In reference to
The above disclosure is related to the detailed technical contents and inventive features thereof. People skilled in this field may proceed with a variety of modifications and replacements based on the disclosures and suggestions of the invention as described without departing from the characteristics thereof Nevertheless, although such modifications and replacements are not fully disclosed in the above descriptions, they have substantially been covered in the following claims as appended.
Number | Date | Country | Kind |
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098106353 | Feb 2009 | TW | national |