CN210840142U

CN210840142U - Low-power-consumption linear constant current circuit

Info

Publication number: CN210840142U
Application number: CN201921307787.0U
Authority: CN
Inventors: 李域
Original assignee: Jiangsu Deyi Xiangyu Optoelectronics Technology Co ltd
Current assignee: Jiangsu Deyi Xiangyu Optoelectronics Technology Co ltd
Priority date: 2019-08-13
Filing date: 2019-08-13
Publication date: 2020-06-23
Anticipated expiration: 2029-08-13

Abstract

The utility model discloses a linear constant current circuit of low-power consumption, the LED light source is through first zener diode, the constant current adjusting tube, first emitter resistance, first zener tube current-limiting resistance, the one-level constant current circuit that external current-limiting resistance constitutes is connected on power supply, the control end of first zener diode is connected with the bias voltage stabilizing circuit who comprises second zener diode, second emitter resistance, second zener tube current-limiting resistance, second external current-limiting resistance simultaneously, set up stable bias voltage for voltage reference TL 431's control end, the bias voltage value is less than 2.5V, under the operating condition of equal output current, the circuit loss when having reduced the constant current state work, calorific capacity is little, the temperature rise is low, and is stable and reliable, factor of safety is high, can use in the great constant current circuit of output current, adapt to the application demand that vehicle multichannel circuit is constant current respectively; simple structure and low product cost.

Description

Low-power-consumption linear constant current circuit

Technical Field

The utility model relates to a can realize the linear constant current circuit's of low-power consumption improvement circuit.

Background

The basic structure of a traditional linear constant current circuit is generally formed by combining a voltage reference TL431 and a triode or a MOSFET, the working principle is that the voltage on R3 is fed back to the control end of the TL431, when the current is large, the voltage on R3 is increased, the b pole of Q1 is lowered, and therefore the current on R3 is reduced; on the contrary, when the voltage on R3 is reduced when the current is reduced, the b pole of Q1 is increased, so that the current on R3 is increased, and the function of constant current is realized; although the circuit is widely applied due to simple and reliable circuit structure and high constant current precision, the reference voltage value of the TL431 in the circuit is 2.5V, so that the voltage of the Q1c-e pole must satisfy the following formula in order to ensure that the circuit can reliably realize the constant current function: c-e is more than or equal to 2.5+0.6 (V), namely c-e is more than or equal to 3.1V. Introducing a power formula Q = UI, obtaining Q = 3.1I, wherein Q is the consumed power of the circuit, and I is the output current, according to the formula, the C-E pole of the circuit must meet the voltage difference of more than 3.1V to achieve the constant current function, and in the application with small output current, the value of 'Q' (heat loss) can be controlled within an acceptable range because the value of 'I' in the formula is small; however, when the output current is large, the value of 'Q' is increased by 3.1 times, which causes circuit loss, large heat productivity, temperature rise and unstable operation, and limits the application of the linear constant current circuit in a large output current circuit, especially in a respective constant current structure of a multi-circuit for a vehicle.

Disclosure of Invention

The utility model aims to solve the technical problem that a simple structure is provided, and the circuit loss is few, and the good reliability can use the linear constant current circuit of low-power consumption in the great constant current circuit of output current.

The utility model discloses a linear constant current circuit of low-power consumption, including the LED light source that is connected to power supply, its characterized in that: the LED light source is connected with a first voltage-stabilizing diode, a constant current triode, a sampling resistor and a first voltage-stabilizing tube current-limiting resistor, the basic linear constant current circuit is composed of a first external current limiting resistor, a bias voltage stabilizing circuit is connected between a sampling resistor of the basic linear constant current circuit and an emitter of a constant current triode, the bias voltage stabilizing circuit comprises a first bias resistor, a second bias resistor and a third bias resistor which are sequentially connected in series and then connected in parallel between the emitter of the constant current triode and the sampling resistor, a connection point between the first bias resistor and the second bias resistor is directly connected to a first voltage stabilizing diode through an electric circuit, a second voltage stabilizing diode is further connected between the second bias resistor and the third bias resistor, one end of the second voltage stabilizing diode is connected to a connection point between the second bias resistor and the third bias resistor, and the other end of the second voltage stabilizing diode is connected to the input end of the first voltage stabilizing diode.

The bias voltage value of the bias voltage stabilizing circuit is less than 2.5V;

the bias voltage value of the bias voltage stabilizing circuit is 2.0V;

the constant current triode is a metal-oxide-semiconductor field effect transistor (MOSFET);

the LED light source is two light emitting diodes connected in series;

the constant current triode is an NPN type triode;

and anodes of the first voltage stabilizing diode and the second voltage stabilizing diode are connected to the grounding point in parallel.

The utility model discloses a linear constant current circuit of low-power consumption sets up stable bias voltage through biasing voltage stabilizing circuit at voltage reference TL 431's control end, and the bias voltage value is less than 2.5V, under the operating condition of equal output current, has reduced the circuit loss when the constant current state is worked, and calorific capacity is little, and the temperature rise is low, and is reliable and stable, and factor of safety is high, can use in the great constant current circuit of output current, adapts to the application demand that the multichannel circuit for the vehicle is constant current respectively; simple structure and low product cost.

Drawings

FIG. 1 is a schematic diagram of a prior art linear constant current circuit;

fig. 2 is a schematic diagram of a low-power linear constant current circuit according to an embodiment of the present invention.

Detailed Description

As shown in the figure, the low-power-consumption linear constant current circuit comprises an LED light source connected to a power supply VCC, wherein the LED light source is two light emitting diodes LED1 and LE2 connected in series to form a load resistor; the LED light source is connected with a basic linear constant current circuit consisting of a first voltage-stabilizing diode TL431, a constant current triode Q1, a sampling resistor R3, a first voltage-stabilizing tube current-limiting resistor R2 and a first external current-limiting resistor R1, and the LED light source is connected between the drain electrode of the constant current triode Q1 and a power supply;

a bias voltage stabilizing circuit is connected between the sampling resistor of the basic linear constant current circuit and the emitter of the constant current triode, the bias voltage stabilizing circuit comprises a first bias resistor R4, a second bias resistor R5 and a third bias resistor R6 which are sequentially connected in series and then connected in parallel between the emitter of the constant current triode and the sampling resistor, a connection point between the first bias resistor R4 and the second bias resistor R5 is directly connected to a first voltage-stabilizing diode TL431 through an electric circuit, a second voltage-stabilizing diode ZD1 is also connected between the second bias resistor R5 and the third bias resistor R6, one end of the second voltage-stabilizing diode ZD1 is connected to a connection point between the second bias resistor and the third bias resistor, and the other end of the second voltage-stabilizing diode ZD1 is connected to the input end of the first voltage; the third bias resistor R6 is connected with the LED light source in parallel to a power supply VCC;

the bias voltage value of the bias voltage stabilizing circuit can be set to any value less than 2.5V, and particularly, the bias voltage value of the bias voltage stabilizing circuit can be set to 2.0V, so that the circuit loss is greatly reduced.

The first zener diode TL431 and the second zener diode ZD1 may be selected from conventional zener diodes with the same performance parameters, or may be changed according to different usage requirements.

The constant current adjusting tube can be an NPN type triode or an MOSFET metal-oxide-semiconductor field effect transistor, and has the advantages of simple structure, convenience in installation, connection and operation and low cost.

The anodes of the first voltage stabilizing diode and the second voltage stabilizing diode are connected to the grounding point in parallel, so that the device is safe and reliable.

The specific design concept is as follows:

the basic structure of a linear constant current circuit in the prior art is as follows: voltage reference TL431+ transistor (or MOSFET). The working principle is as follows: the voltage on R3 is fed back to the TL431 control end, when the current is large, the voltage on R3 is increased, the b pole of Q1 is lowered, and therefore the current on R3 is reduced; conversely, when the voltage at R3 decreases and the b-pole of Q1 increases when the current decreases, the current at R3 increases, and the function of constant current is realized. The circuit has simple and reliable structure and high constant current precision, so the circuit can be widely applied. However, since the reference voltage value of TL431 in this circuit is 2.5V, to ensure that such a circuit reliably realizes the constant current function, the voltage of Q1c-e pole must satisfy the following formula: c-e is more than or equal to 2.5+0.6 (V), namely c-e is more than or equal to 3.1V. Introducing the power formula Q = UI, Q =3.1 × I (where Q consumes power for this circuit and I is the current of the output) can be derived. According to the formula, the C-E pole of the circuit can achieve the constant current function only by meeting the voltage difference of more than 3.1V. This is because the value of 'I' is relatively small in the formula in applications where the output current is small, the value of 'Q' (heat loss) can be controlled within an acceptable range. However, when the output current is larger, the value of 'Q' is increased by 3.1 times, and therefore, the application of the circuit in larger output current is limited by the great loss (heat generation) of the circuit.

If the loss of the linear constant current circuit in the constant current state can be reduced, namely the heat generated by the circuit is reduced, the application of the linear constant current circuit in the case of larger output current can be correspondingly expanded.

From the formula Q =3.1 × I listed above (where Q is the consumed power and I is the current of the output), we can see that to achieve 'Q' unchanged (or decreased), the output current 'I' increases, only decreasing by the constant of '3.1'. To achieve this, the circuit of fig. 2 is designed.

The circuit in fig. 2 is added with R4, R5, R6 and ZD1 on the basis of the original circuit, and the circuit provides a stable bias voltage for the control terminal of TL431, and can arbitrarily set a fixed bias voltage value (if the value is less than 2.5V) for the control terminal of TL431, for example, set the bias voltage for the control terminal of TL431 to 2.0V. At this time, the reference voltage of the TL431 control terminal is 2.0+ V (R3) ═ 2.5V, so that the voltage at R3 needs to be greater than 0.5V to reach the control point of 2.5V (i.e., 2.0+ V (R3) ═ 2.0+0.5, and V (R3) ═ 0.5V). According to the formula Q = UI, the loss of the constant current circuit at this time is: q = (0.5+0.3) × I =0.8 × I. It can be clearly seen that the original constant is 3.1, which is changed into 0.8 after improvement, under the working condition of the same output current, the minimum loss value of the circuit in the constant current state is greatly reduced, the problem that the circuit generates heat when working at a large current is solved to a great extent, and the application of the circuit in a large constant current is greatly expanded.

The invention skillfully utilizes the working characteristics of the voltage reference TL431+ triode (or MOSFET) through a plurality of simple devices, reduces the power consumption of the circuit, and realizes the application in a larger constant current circuit by flexibly designing the bias voltage of the circuit under the condition of not changing the advantages of simplicity and reliability of the original circuit. In the application of multiple paths of respective constant currents for vehicles, the cost and the reliability of original products are greatly reduced.

Claims

1. A low-power consumption linear constant current circuit, including being connected to the LED light source of power supply, its characterized in that: the LED light source is connected with a first voltage-stabilizing diode, a constant current triode, a sampling resistor and a first voltage-stabilizing tube current-limiting resistor, the basic linear constant current circuit is composed of a first external current limiting resistor, a bias voltage stabilizing circuit is connected between a sampling resistor of the basic linear constant current circuit and an emitter of a constant current triode, the bias voltage stabilizing circuit comprises a first bias resistor, a second bias resistor and a third bias resistor which are sequentially connected in series and then connected in parallel between the emitter of the constant current triode and the sampling resistor, a connection point between the first bias resistor and the second bias resistor is directly connected to a first voltage stabilizing diode through an electric circuit, a second voltage stabilizing diode is further connected between the second bias resistor and the third bias resistor, one end of the second voltage stabilizing diode is connected to a connection point between the second bias resistor and the third bias resistor, and the other end of the second voltage stabilizing diode is connected to the input end of the first voltage stabilizing diode.

2. The low power consumption linear constant current circuit according to claim 1, wherein: and the bias voltage value of the bias voltage stabilizing circuit is less than 2.5V.

3. The low power consumption linear constant current circuit according to claim 1, wherein: the bias voltage value of the bias voltage stabilizing circuit is 2.0V.

4. The low power consumption linear constant current circuit according to claim 1, wherein: the constant current triode is an MOSFET metal-oxide-semiconductor field effect transistor.

5. The low power consumption linear constant current circuit according to claim 1, wherein: the LED light source is two light emitting diodes connected in series.

6. The low power consumption linear constant current circuit according to claim 1, wherein: the constant current triode is an NPN type triode.

7. The low power consumption linear constant current circuit according to claim 1, wherein: and anodes of the first voltage stabilizing diode and the second voltage stabilizing diode are connected to the grounding point in parallel.