Optical coupler and manufacturing method thereof

Abstract

The present invention discloses an optocoupler comprising a light detection circuit composed of a light-emitting diode and a phototransistor, and an output control circuit configured to control the output of the optocoupler based on the detection result of the light detection circuit. The output control circuit comprises an on-branch comprising a first NPN transistor and a off-branch comprising a second NPN transistor. When the light detection circuit does not output a detection current, the output of the optocoupler is set to a low level via the on-branch; when the light detection circuit outputs a detection current, the output of the optocoupler is set to a high level via the off-branch. The present invention also discloses a method for manufacturing the optocoupler.

Description

Technical Field

[0001] The present invention relates to the field of optoelectronic devices, and more particularly to an optical coupler and a method for manufacturing the same. Background Art

[0002] Optocouplers, also known as photoelectric couplers, are devices that use light as a medium to transmit electrical signals. Optocouplers are used in applications where isolation is required during electrical signal transmission. This isolation technology has long been widely used for signal isolation and transmission due to its high breakdown voltage, strong anti-interference capabilities, and high reliability.

[0003] Optocouplers can be divided into ordinary optocouplers and high-speed optocouplers based on their signal transmission speed. Ordinary optocouplers have the best performance when the signal frequency is less than 100KHZ, and high-speed couplers are generally used in circuits with frequencies greater than 1MHZ.

[0004] Ordinary optocouplers are generally composed of light-emitting diodes and phototransistors. Figure 1 This is an equivalent circuit diagram of a common optocoupler application circuit, with the phototransistor directly connected to the load. Due to the distributed capacitance inherent in this common optocoupler, including the internal capacitances Cbe and Cce of the phototransistor, the load resistor value significantly affects the optocoupler. If the load resistor is too small, the output voltage swing is limited. If the load resistor is too large, the capacitance deteriorates the frequency characteristics of the optocoupler and increases the propagation delay. When the phototransistor transitions from cutoff to saturation, the photocurrent is amplified, resulting in a relatively high current in the saturated phototransistor. After the optical signal disappears, the phototransistor gradually transitions from saturation to cutoff. Because the saturated state stores a large number of minority carriers, the stored charge is extracted more slowly, resulting in a longer transition from saturation to cutoff. As the frequency increases, if the signal pulse width is less than the time required to extract the stored charge in the transistor, the output signal becomes distorted.

[0005] At present, ordinary high-speed optocoupler devices are composed of light-emitting diodes and light-receiving chips. Figure 2 The figure shows the equivalent schematic diagram of the high-speed optocoupler's application circuit. Conventional photoelectric receiver chips typically include a photodiode and a transistor. The photodiode's output terminal is formed by connecting a photosensitive diode to the base of a transistor. The generated photocurrent is amplified by the transistor and then drives the load. This connection structure utilizes the device characteristic that the switching speed of the photodiode and transistor is two orders of magnitude faster than that of the phototransistor, enabling the optocoupler to transmit a 1MHz input signal.

[0006] However, the common implementation method of this high-speed optocoupler is to integrate the photodiode and output transistor onto the same substrate material. Generally speaking, the cost of this manufacturing process is much higher than that of phototransistor manufacturing. Due to manufacturing cost constraints, the area of ​​the photodiode in this structure should not be too large, resulting in a weak output current capability of the photodiode. Affected by this factor, under the same load conditions, the input current of this high-speed optocoupler input end is greater than that of ordinary optocouplers, which will cause the input power consumption of this optocoupler to increase compared with ordinary optocouplers.

[0007] Therefore, it is necessary to provide an optical coupler and a manufacturing method thereof that can ensure that the output signal is not distorted under high transmission signal conditions while having low input power consumption and cost advantages. Summary of the Invention

[0008] An object of the present invention is to provide an optocoupler comprising a light detection circuit formed of a light emitting diode and a phototransistor, and further comprising: an output control circuit configured to control the output of the optocoupler based on a detection result of the light detection circuit, wherein the output control circuit comprises an on-branch having a first NPN transistor and a off-branch having a second NPN transistor. When the light detection circuit does not output a detection current, the output of the optocoupler is set to a low level via the on-branch; when the light detection circuit outputs a detection current, the output of the optocoupler is set to a high level via the off-branch.

[0009] Preferably, the output control circuit includes a first end, a second end, a third end and a fourth end, the first end is connected to the light detection circuit to receive the detection current, the second end is a bias potential connection end for providing bias for the opening branch and the closing branch, the third end is the output end of the optocoupler, and the fourth end is the ground end for the opening branch and the closing branch.

[0010] Preferably, the open branch further includes a first resistor and a second resistor, and the closed branch further includes a third resistor and a fourth resistor, wherein

[0011] The base of the first NPN transistor is connected to the base of the second NPN transistor, and a common terminal of the two is connected to the first end of the first resistor; the collector of the second NPN transistor is connected to the first end of the third resistor, and the common terminal of the two serves as the third terminal of the output control circuit;

[0012] The second end of the first resistor and the second end of the third resistor are connected to the bias potential as the second end of the output control circuit; the emitter of the first NPN transistor is connected to the first end of the second resistor; the emitter of the second NPN transistor is connected to the first end of the fourth resistor, and the common end of the two serves as the first end of the output control circuit; the second end of the second resistor is connected to the second end of the fourth resistor, and the common end of the two serves as the fourth end of the output control circuit; and the collector of the first NPN transistor is left floating.

[0013] Preferably, the first NPN transistor and the second NPN transistor have the same parameters.

[0014] Preferably, the resistance of the fourth resistor is less than 100Ω.

[0015] Preferably, the light detection circuit and the output control circuit are formed and connected by a dual chip packaging technology.

[0016] Another aspect of the present invention provides a method for preparing the above-mentioned optical coupler, comprising: manufacturing a light detection circuit and an output control circuit formed on the same substrate into two chips and electrically connecting them through a dual-chip packaging technology.

[0017] The beneficial effects of the present invention are as follows:

[0018] Provided are an optical coupler and a preparation method thereof, which can ensure that an output signal is not distorted under a high transmission signal and has low input power consumption and cost advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0020] Figure 1 This is an equivalent circuit diagram of the application circuit of a conventional optical coupler in the prior art;

[0021] Figure 2 The equivalent schematic diagram of the application circuit of the prior art high-speed optocoupler is shown;

[0022] Figure 3 is a schematic circuit diagram of an optical coupler 10 according to an embodiment of the present application; and

[0023] Figure 4 Schematic diagram showing various ports of the optical coupler 10 according to an embodiment of the present application. DETAILED DESCRIPTION

[0024] In order to more clearly illustrate the present invention, the present invention is further described below in conjunction with preferred embodiments and accompanying drawings. Similar components in the accompanying drawings are represented by the same reference numerals. It should be understood by those skilled in the art that the following detailed description is illustrative rather than restrictive and should not be used to limit the scope of protection of the present invention.

[0025] The following combination Figure 3 and Figure 4 The structural principle of the optical coupler 10 according to the embodiment of the present application is described, wherein: Figure 3 is a schematic circuit diagram of an optical coupler 10 according to an embodiment of the present application; Figure 4 Schematic diagram showing various ports of the optical coupler 10 according to an embodiment of the present application.

[0026] First combine Figure 3 According to an embodiment of the present application, the optical coupler 10 includes a light detection circuit 101 and an output control circuit 103 .

[0027] The light detection circuit includes a light-emitting diode D and a phototransistor T. Preferably, the light-emitting diode can be an infrared light-emitting diode as the signal input terminal of the entire optical coupler 10. When the optical coupler 10 receives an appropriate input signal Input, the light-emitting diode D emits light, and the base region of the phototransistor T senses the light emitted by the light-emitting diode D and generates an output current as the detection result of the light detection circuit 101 at this time. When the optical coupler 10 does not receive the appropriate input signal Input, the light-emitting diode D does not emit light, and the phototransistor T does not generate an output current. The no output current state is the detection result of the light detection circuit 101 at this time.

[0028] The output control circuit 103 controls the output of the optocoupler 10 based on the detection results of the light detection circuit 101. According to an embodiment of the present application, the output control circuit 103 may include an on-branch 103-1 and a off-branch 103-2. The on-branch 103-1 includes a first NPN transistor Q1, and the off-branch 103-2 includes a second NPN transistor Q2. Based on the detection results of the light detection circuit 101, the on-branch 103-1 utilizes the structure of the first NPN transistor Q1 to control the on-state of the second NPN transistor Q2, thereby setting the output of the optocoupler 10 to a low level. The off-branch 103-2 utilizes the structure of the second NPN transistor Q2 to control the off-state of the second NPN transistor Q2, thereby setting the output of the optocoupler 10 to a high level, thereby achieving control over the output of the optocoupler 10.

[0029] Specifically, according to an embodiment of the present application, the output control circuit 103 includes a first terminal 1, a second terminal 2, a third terminal 3 and a fourth terminal 4. The first terminal 1 is connected to the light detection circuit 101 to receive the detection current of the light detection circuit 101, the second terminal 2 is a bias potential connection terminal used to provide a bias Vcc for the opening branch 103-1 and the closing branch 103-2, the third terminal 3 is the output terminal Output of the optical coupler 10, and the fourth terminal 4 is the ground terminal for the opening branch 103-1 and the closing branch 103-2.

[0030] According to an embodiment of the present application, the enabling branch 103 - 1 may further include a first resistor R1 and a second resistor R2 in addition to the first NPN transistor Q1 , and the disabling branch 103 - 2 may further include a third resistor R3 and a fourth resistor R4 in addition to the second NPN transistor Q2 .

[0031] like Figure 3As shown, the base of the first NPN transistor Q1 is connected to the base of the second NPN transistor Q2, and the common terminal of the two is connected to the first end of the first resistor R1; the collector of the second NPN transistor Q2 is connected to the first end of the third resistor R3, and the common terminal of the two serves as the third terminal 3 of the output control circuit 103-1; the second end of the first resistor R1 and the second end of the third resistor R3 are connected to the bias potential to serve as the second terminal 2 of the output control circuit 103; the emitter of the first NPN transistor Q1 is connected to the first end of the second resistor R2; the emitter of the second NPN transistor Q2 is connected to the first end of the fourth resistor R4, and the common terminal of the two serves as the first end of the output control circuit 103; the second end of the second resistor R2 is connected to the second end of the fourth resistor R4, and the common terminal of the two serves as the fourth terminal 4 of the output control circuit 103; and the collector of the first NPN transistor Q1 is left floating.

[0032] When the light detection circuit 101 detects that the phototransistor T is not outputting current, the activation branch 103-1 stably biases the second NPN transistor Q2 in a saturated conduction state via the junction of the first resistor R1 and the emitter of the first NPN transistor Q1, and the second resistor R2, which serves as an emitter-series resistor. That is, the activation branch 103-1 turns on the second NPN transistor Q2, and the optocoupler 10 outputs a low level. When the light detection circuit 101 detects that the phototransistor T is outputting current, the output current of the phototransistor T raises the emitter potential of the second NPN transistor Q2, turning it off. That is, the shutdown branch 103-2 turns off the second NPN transistor Q2, and the optocoupler 10 outputs a high level. As can be seen from the above, the output control circuit 103 controls the output of the optocoupler 10 based on the detection result of the light detection circuit 101.

[0033] Refer again Figure 3 According to an embodiment of the present application, the fourth resistor R4 also serves as a pull-down resistor of the phototransistor T. Preferably, according to an embodiment of the present application, the resistance of the fourth resistor R4 can be set to be less than 100Ω. Compared with the prior art where the pull-down resistor of the phototransistor is usually set to be greater than 1KΩ, the circuit structure of the application reduces the pull-down resistor of the phototransistor T by providing the turn-on branch 103-1 and the turn-off branch 103-2, each including an NPN transistor, thereby effectively shortening the switching time of the phototransistor T. Secondly, by utilizing the characteristic that the switching time of a bipolar transistor is superior to that of a phototransistor, the switching time of the optocoupler 10 is further increased.

[0034] Optionally, the optical coupler 10 can meet the requirement of transmitting 1KHz to 200KHz signals.

[0035] According to the output control circuit composed of the opening branch 103-1 and the closing branch 103-2 of the embodiment of the present application, while ensuring that the output signal is not distorted under high transmission signals, the manufacturing cost of this structure is lower than the cost of integrating photodiodes and transistors. At the same time, the current output capability of the light detection circuit 101 under the same lighting conditions is 100-200 times that of the photodiode integrated in the transistor output high-speed optocoupler. Therefore, when the output control circuit 103 of the present application is packaged and connected with the light detection circuit 101 at the input end, the area of ​​the light detection circuit 101 and the parameters of the control circuit 103 are reasonably optimized. This can enable the optical coupler 10 of the embodiment of the present application to have low input power consumption and cost advantages while ensuring that the output signal is not distorted under high transmission signals.

[0036] Further preferably, according to an embodiment of the present application, the specifications of the first NPN transistor Q1 and the second NPN transistor Q2 are identical. By utilizing the fact that the emitter junction IV characteristics of the first NPN transistor Q1 and the second NPN transistor Q2 vary similarly with temperature, the current ratio of the on branch 103-1 to the off branch 103-2 in the optocoupler 10 can be kept relatively small over temperature, thereby improving the circuit's stability over temperature.

[0037] like Figure 3 As can be seen from the schematic diagram, the optocoupler 10 according to the embodiment of the present application is a six-pin optocoupler. Specifically, the light detection circuit 101 and the output control circuit 103 are made into two chips using semiconductor manufacturing technology, and then the two chips are connected to form an optocoupler device by using double-chip packaging technology as shown in the circuit schematic diagram, and then packaged as shown in FIG. Figure 4 The six-pin optocoupler shown.

[0038] For example, Figure 4 As can be seen, pins 1 and 2 correspond to the input side of the light detection circuit 101, where pin 1 can be the input terminal; pin 6 corresponds to the second terminal of the output control circuit 103, which is the bias pin; pin 4 corresponds to the fourth terminal of the output control circuit 103, which is grounded; and pin 5 can correspond to the third terminal of the output control circuit 103 and can serve as the output terminal of the optocoupler 10. Those skilled in the art will appreciate that the above examples are merely illustrative and the embodiments of the present application are not limited thereto. The specific positions of the above functional pins in the package can be changed according to specific design requirements.

[0039] In existing technology, integrating a photodiode and output transistor on the same substrate material results in high process costs. Furthermore, to control costs and maintain parameter uniformity and effective area utilization, the photodiode area is relatively small, resulting in weak photocurrent generation. However, the circuit structure of this application allows the output control circuit 103 to be integrated into a single chip, significantly reducing the integrated area and process costs. Furthermore, when the light detection circuit 101 is fabricated separately, the phototransistor's characteristic of high output current under the same illumination conditions allows control of the acceleration circuit with relatively low input current, thus achieving the low input current characteristic of this application.

[0040] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. An optical coupler comprising a light detection circuit consisting of a light emitting diode and a phototransistor, characterized in that: Also includes: an output control circuit configured to control the output of the optical coupler according to the detection result of the light detection circuit, The output control circuit includes an on-branch having a first NPN transistor and an off-branch having a second NPN transistor. When the light detection circuit does not output a detection current, the output of the optocoupler controls the second NPN transistor to be turned on through the on-branch and is set to a low level. When the light detection circuit outputs a detection current, the output of the optocoupler controls the second NPN transistor to be turned off through the detection current and is set to a high level.

2. The optical coupler according to claim 1, wherein The output control circuit includes a first end, a second end, a third end and a fourth end. The first end is connected to the light detection circuit to receive a detection current. The second end is a bias potential connection end for providing a bias for the turn-on branch and the turn-off branch. The third end is the output end of the optocoupler. The fourth end is the ground end of the turn-on branch and the turn-off branch.

3. The optical coupler according to claim 2, wherein The open branch further includes a first resistor and a second resistor, and the closed branch further includes a third resistor and a fourth resistor, wherein The base of the first NPN transistor is connected to the base of the second NPN transistor, and a common terminal of the two is connected to the first end of the first resistor; The collector of the second NPN transistor is connected to the first end of the third resistor, and a common end of the two serves as the third end of the output control circuit; The second end of the first resistor and the second end of the third resistor are connected to the bias potential connection end as the second end of the output control circuit; The emitter of the first NPN transistor is connected to the first end of the second resistor; The emitter of the second NPN transistor is connected to the first end of the fourth resistor, and a common end of the two serves as the first end of the output control circuit; The second end of the second resistor is connected to the second end of the fourth resistor, and a common end of the two serves as the fourth end of the output control circuit; and The collector of the first NPN transistor is suspended.

4. The optical coupler according to claim 3, wherein The parameters of the first NPN transistor and the second NPN transistor are the same.

5. The optical coupler according to claim 3, wherein: The resistance of the fourth resistor is less than 100Ω.

6. The optical coupler according to claim 4, wherein: The resistance of the fourth resistor is less than 100Ω.

7. The optical coupler according to claim 1, wherein The light detection circuit and the output control circuit are formed and connected by a dual chip packaging technology.

8. A method for manufacturing the optical coupler according to any one of claims 1 to 7, comprising: The light detection circuit and the output control circuit formed on the same substrate are made into two chips and electrically connected through dual-chip packaging technology.

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