Constant current source driving circuit

Abstract

The utility model relates to a constant current source driving circuit, the constant current source driving circuit comprises a first resistor, a second resistor, an operational amplifier, a third resistor, a fourth resistor and a switching device, the first end of the first resistor is connected with an input voltage, and the second end of the first resistor is connected with the in-phase input end of the operational amplifier; the first end of the second resistor is connected with the second end of the first resistor, and the second end of the second resistor is grounded; the output end of the operational amplifier is connected to the first terminal of the switching device through the third resistor; the second terminal of the switching device is connected with the first end of the fourth resistor, and the second end of the fourth resistor is grounded; the reverse input end of the operational amplifier is connected to the second terminal of the switching device; and a third terminal of the switching device is used for connecting a load.

Description

Technical Field

[0001] The present disclosure generally relates to the field of LED light source driving technology, and more specifically, to a constant current source driving circuit. Background Art

[0002] The light source of the point-type light source LED signal mechanism is divided into a main LED group and a sub-LED group, each of which is composed of a single or several high-power and high-brightness LEDs, and the driving current reaches several hundred mA. When it is normally lit, the main LED group is lit. In the case of a failure of the main LED group, the sub-LED group is lit, and the signal machine sends an alarm to the room. In order to make the LED work reliably and stably, the LED uses a constant current drive. Utility Model Content

[0003] A brief overview of the present invention is given below in order to provide a basic understanding of certain aspects of the present invention. It should be understood that this overview is not an exhaustive overview of the present invention. It is not intended to identify key or important parts of the present invention, nor is it intended to limit the scope of the present invention. Its purpose is merely to present certain concepts in a simplified form as a prelude to a more detailed description discussed later.

[0004] In view of this, a constant current source driving circuit is provided, which can provide constant current control for a high-power point-type LED light source.

[0005] According to one aspect of the present disclosure, a constant current source driving circuit is provided, comprising a first resistor, a second resistor, an operational amplifier, a third resistor, a fourth resistor and a switching device, wherein:

[0006] A first end of the first resistor is connected to an input voltage, and a second end of the first resistor is connected to a non-inverting input end of the operational amplifier;

[0007] The first end of the second resistor is connected to the second end of the first resistor, and the second end of the second resistor is grounded;

[0008] The output terminal of the operational amplifier is connected to the first terminal of the switching device via the third resistor;

[0009] The second terminal of the switch device is connected to the first end of the fourth resistor, and the second end of the fourth resistor is grounded;

[0010] The inverting input terminal of the operational amplifier is connected to the second terminal of the switching device;

[0011] The third terminal of the switch device is used to connect a load.

[0012] In this way, the basic constant current driving function can be realized through a simple circuit structure, which is very suitable for driving high-power LEDs.

[0013] Optionally, in an example of the above aspect, the switching device is an N-channel field effect transistor, the first terminal of the switching device is a gate, the second terminal is a source, and the third terminal is a drain.

[0014] In this way, an N-channel field effect transistor is selected as a switching device, which has a small on-resistance and reduces power loss.

[0015] Optionally, in an example of the above aspect, the constant current source driving circuit further includes: a low-pass filter circuit connected between the output end of the operational amplifier and the third terminal of the switching device.

[0016] Optionally, in an example of the above aspect, the low-pass filter circuit includes a capacitor and a fifth resistor.

[0017] In this way, high-frequency AC signals can be filtered out and anti-interference performance can be enhanced.

[0018] Optionally, in an example of the above aspect, the load is a light emitting diode.

[0019] Optionally, in an example of the above aspect, the voltage of the third terminal is measured in real time to monitor the working state of the load.

[0020] In this way, the working status of the load can be monitored. When the load is disconnected or short-circuited, the main control unit can perform corresponding operations and issue an alarm. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The above and other purposes, features and advantages of the present invention will be more easily understood by referring to the following description of the embodiments of the present invention in combination with the accompanying drawings. The components in the accompanying drawings are only for illustrating the principles of the present invention. In the accompanying drawings, the same or similar technical features or components will be represented by the same or similar reference numerals. In the accompanying drawings:

[0022] Figure 1 is a schematic topological diagram of a constant current source driving circuit 100 according to an embodiment of the present disclosure.

[0023] Figure 2 is a schematic topological diagram of a constant current source driving circuit 200 according to another embodiment of the present disclosure.

[0024] The reference numerals are as follows:

[0025] 100, 200: Constant current source drive circuit R1: First resistor

[0026] R2: Second resistor U1: Operational Amplifier

[0027] R3: The third resistor R4: The fourth resistor

[0028] Q1: Switching device V1: Input voltage

[0029] O: Output terminal of operational amplifier U1 G: First terminal of switching device Q1

[0030] S: Second terminal of the switching device Q1 D: The third terminal of the switching device Q1

[0031] Vin+: non-inverting input terminal Vin-: Reverse input terminal

[0032] L: Load LP: Low pass filter circuit

[0033] C1: Capacitor R5: The fifth resistor DETAILED DESCRIPTION

[0034] The subject matter described herein will now be discussed with reference to example embodiments. It should be understood that the discussion of these embodiments is only to enable those skilled in the art to better understand and implement the subject matter described herein, and is not a limitation of the scope of protection, applicability or examples set forth in the claims. The function and arrangement of the elements discussed can be changed without departing from the scope of protection of the present disclosure. Various examples can omit, replace or add various processes or components as needed. For example, the described method can be performed in an order different from the described order, and various steps can be added, omitted or combined. In addition, the features described relative to some examples can also be combined in other examples.

[0035] As used herein, the term "including" and its variations represent open terms, meaning "including but not limited to". The term "based on" means "based at least in part on". The terms "one embodiment" and "an embodiment" mean "at least one embodiment". The term "another embodiment" means "at least one other embodiment". The terms "first", "second", etc. may refer to different or the same objects. Other definitions may be included below, whether explicit or implicit. Unless the context clearly indicates otherwise, the definition of a term is consistent throughout the specification.

[0036] According to the embodiment of the present disclosure, a constant current source driving circuit is provided that can provide constant current control for a high-power point-type LED light source, and in addition, the working state of the LED can be monitored in real time. When the LED fails due to a short circuit or an open circuit, the circuit can monitor the change in the working state of the LED and switch to other working modes.

[0037] The constant current source driving circuit can provide a constant current to the load, and can keep the output current constant even if the load resistance changes. In the constant current source according to the embodiment of the present disclosure, an operational amplifier (operational amplifier, referred to as an op amp) is used, by providing a stable reference voltage at the in-phase input terminal of the op amp, and connecting the current limiting resistor and the load at the inverting input terminal. When the load resistance changes, due to the negative feedback of the op amp, it will adjust the output voltage to keep the current through the current limiting resistor constant.

[0038] The constant current source driving circuit according to the embodiment of the present disclosure is described below with reference to the accompanying drawings.

[0039] Figure 1 is a schematic topological diagram of a constant current source driving circuit 100 according to an embodiment of the present disclosure.

[0040] like Figure 1 As shown, the constant current source driving circuit 100 includes a first resistor R1, a second resistor R2, an operational amplifier U1, a third resistor R3, a fourth resistor R4 and a switch device Q1.

[0041] The first end of the first resistor R1 is connected to the input voltage V1 , and the second end of the first resistor R1 is connected to the non-inverting input terminal Vin+ of the operational amplifier U1 .

[0042] A first end of the second resistor R2 is connected to the second end of the first resistor R1 , and a second end of the second resistor R2 is grounded.

[0043] The output terminal O of the operational amplifier U1 is connected to the first terminal G of the switching device Q1 via the third resistor R3.

[0044] The second terminal S of the switch device Q1 is connected to a first end of a fourth resistor R4, and a second end of the fourth resistor R4 is grounded.

[0045] The inverting input terminal Vin- of the operational amplifier U1 is connected to the second terminal S of the switching device Q1.

[0046] The third terminal D of the switching device Q1 is used to connect a load L.

[0047] like Figure 1As shown, operational amplifier U1 constitutes a voltage follower. According to the "virtual disconnection" principle of the operational amplifier, the input impedance of the operational amplifier is infinite, and there is no current flowing in or out between the inverting input terminal Vin- and the non-inverting input terminal Vin+ of the operational amplifier. It can be obtained that the voltage Vin+ at the non-inverting input terminal of the operational amplifier U1 is equal to the input voltage V1 multiplied by Right now

[0048] According to the "virtual short" principle of the operational amplifier, the voltages at the inverting input terminal Vin- and the non-inverting input terminal Vin+ of the operational amplifier are equal, that is, Vin-=Vin+, and the voltage at the first terminal of the fourth resistor R4 can be deduced to be

[0049] The fourth resistor is used as a sampling resistor, and the constant current IL flowing through the load is determined by the sampling resistor R4 and Vs, that is,

[0050]

[0051] It can be seen that by adjusting the resistance values ​​of the first resistor R1 and the second resistor R2, the level of the input voltage Vin+ can be adjusted. By adjusting the resistance value of R4, the working current flowing through the load L can be adjusted.

[0052] Therefore, by changing the resistance values ​​of R1, R2, and R4, a wide range of input voltage is achieved, and the input voltage and LED drive current can be flexibly adjusted.

[0053] exist Figure 1 In the figure, the switch device Q1 is an N-channel field effect transistor, whose first terminal G is a gate, the second terminal S is a source, and the third terminal D is a drain. It can be understood that other switch devices, such as a triode, can also be used in the constant current source drive circuit according to the present disclosure. The present disclosure does not limit the type of switch device.

[0054] exist Figure 1 In the figure, the load connected to the constant current source driving circuit is a light emitting diode (LED). It can be understood that other types of loads can also be connected, which will not be described in detail here.

[0055] In the following, an example is given in which the switch device is an N-channel field effect transistor and the load is an LED.

[0056] When the LED is working, the voltage drop across the two ends is VL. When the LED is working normally, the drain voltage Vd of the N-channel field effect tube is Vcc-VL. When the constant current source driving circuit according to the embodiment of the present disclosure is used, the drain voltage Vd is monitored in real time. When the LED has an open circuit fault, Vd drops to 0V. When the LED has a short circuit fault, the Vd voltage rises to Vcc. By monitoring the Vd voltage, the working state of the load LED can be monitored.

[0057] In a system using two groups of LED light sources, the main and auxiliary LED groups use the same constant current source drive circuit according to the embodiment of the present disclosure. When an LED in the main LED group fails (short circuit or open circuit), an abnormal Vd level (Vd equals Vcc or 0V) will be detected, and the auxiliary LED group working mode can be switched; when an LED in the auxiliary LED group fails, an abnormal Vd level in the auxiliary LED group will also be detected, and the external load resistor will be cut off at this time to enter the light-off mode.

[0058] Figure 2 is a schematic topological diagram of a constant current source driving circuit 200 according to another embodiment of the present disclosure.

[0059] like Figure 2 As shown, the constant current source driving circuit 200 includes a first resistor R1, a second resistor R2, an operational amplifier U1, a third resistor R3, a fourth resistor R4 and a switch device Q1. The connection mode and function of these components are similar to Figure 1 The constant current source driving circuit 100 shown is similar and will not be described in detail here.

[0060] Figure 2 The constant current source driving circuit 200 shown further includes a low pass filter circuit LP connected between the output terminal O of the operational amplifier U1 and the third terminal S of the switching device Q1.

[0061] exist Figure 2 In the embodiment, the low-pass filter circuit LP includes a capacitor C1 and a fifth resistor R5. It is understood that other forms of low-pass filter circuits may also be used, not limited to Figure 2 as shown in .

[0062] The inverting input terminal Vin- of the operational amplifier Q1 is connected to the second terminal S of the switching device Q1 via the low-pass filter circuit LP.

[0063] By adjusting the values ​​of the capacitor C1 and the fifth resistor R5, high-frequency interference on site can be filtered out and the anti-interference performance can be enhanced.

[0064] In summary, the constant current source driving circuit according to the embodiment of the present disclosure has at least one or more of the following technical advantages.

[0065] Low cost, simple structure and good portability. Figure 1 As shown, only 1 operational amplifier + 4 resistors + 1 N-channel field effect transistor are needed to realize the basic constant current driving function, which is very suitable for driving high-power LEDs.

[0066] By changing the resistance values ​​of R1, R2, and R4, a wide range of input voltage is achieved, and the input voltage and LED drive current can be flexibly adjusted.

[0067] Capacitor C1 and resistor R5 form a low-pass filter circuit to filter out high-frequency AC signals and enhance anti-interference performance.

[0068] By measuring the level Vd of the drain of the field effect tube Q1 in real time, the working state of the load is monitored. When the load is disconnected or short-circuited, the main control unit can perform corresponding operations and issue an alarm.

[0069] Not all units in the above structural diagrams are necessary, and some units may be omitted according to actual needs. The device structure described in the above embodiments may be a physical structure or a logical structure, that is, some units may be implemented by the same physical entity, or some units may be implemented by multiple physical entities, or may be implemented by some components in multiple independent devices.

[0070] The above description of the present disclosure is provided to enable any person of ordinary skill in the art to implement or use the present disclosure. Various modifications to the present disclosure will be apparent to those of ordinary skill in the art, and the general principles defined herein may be applied to other variations without departing from the scope of protection of the present disclosure. Therefore, the present disclosure is not limited to the examples and designs described herein, but is consistent with the widest range of principles and novel features disclosed herein.

[0071] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

[0072] Nouns and pronouns relating to persons in this patent application are not limited to a specific gender.

Claims

1. A constant current source driving circuit, characterized in that: The invention comprises a first resistor (R1), a second resistor (R2), an operational amplifier (U1), a third resistor (R3), a fourth resistor (R4) and a switch device (Q1), wherein: A first end of the first resistor (R1) is connected to an input voltage, and a second end of the first resistor (R1) is connected to a non-inverting input terminal (Vin+) of the operational amplifier (U1); A first end of the second resistor (R2) is connected to a second end of the first resistor (R1), and a second end of the second resistor (R2) is grounded; The output terminal (O) of the operational amplifier (U1) is connected to the first terminal (G) of the switching device (Q1) via the third resistor (R3); The second terminal (S) of the switch device (Q1) is connected to the first end of the fourth resistor (R4), and the second end of the fourth resistor (R4) is grounded; The inverting input terminal (Vin-) of the operational amplifier (U1) is connected to the second terminal (S) of the switching device (Q1); The third terminal (D) of the switching device (Q1) is used to connect a load.

2. The constant current source driving circuit according to claim 1, characterized in that: The switch device (Q1) is an N-channel field effect transistor, the first terminal (G) of the switch device is a gate, the second terminal (S) is a source, and the third terminal (D) is a drain.

3. The constant current source driving circuit according to claim 1 or 2, characterized in that: Also includes: A low-pass filter circuit is connected between the output terminal (O) of the operational amplifier (U1) and the third terminal (D) of the switching device (Q1).

4. The constant current source driving circuit according to claim 3, characterized in that: The low-pass filter circuit (LP) comprises a capacitor (C1) and a fifth resistor (R5).

5. The constant current source driving circuit according to claim 1 or 2, characterized in that: The load (L) is a light emitting diode.

6. The constant current source driving circuit according to claim 1 or 2, characterized in that: The voltage of the third terminal (D) is measured in real time to monitor the working state of the load (L).

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