LED constant current circuit

Abstract

The utility model discloses a kind of LED constant current circuit, including input module, load module, PWM output unit, switch tube Q1, current-limiting resistor R3 and triode Q2;Input module, load module and the D pole of switch tube are sequentially electrically connected, PWM output unit and the G pole of switch tube Q1 are electrically connected, the S pole of switch tube Q1 and the one end of current-limiting resistor R3 are electrically connected, the other end of current-limiting resistor R3 is grounded, the C pole of triode Q2 and PWM output unit are electrically connected, the B pole of triode Q2 and the S pole of switch tube Q1 are electrically connected, the E pole of triode Q2 is grounded;Input module is used to output direct current to load module, and load module includes multiple light emitting diodes, PWM output unit is used to output high level signal to the G pole of switch tube Q1, the PN junction between triode Q2 is fixed voltage drop, triode Q2 is used to maintain the voltage of current-limiting resistor R3 unchanged, the function of load module constant current is realized, additional power consumption can be reduced, improve work efficiency.

Description

TECHNICAL FIELD

[0001] The utility model belongs to the technical field of electronic circuit, specifically a kind of LED constant current circuit. BACKGROUND

[0002] With the development of electronic technology, LED lamp is constantly improved and optimized, in LED industry field, the world is changed from halogen lamp to LED lamp lighting, so LED lamp is widely used, and market demand is large.In the application of LED lamp in electronic circuit, most of them need to realize constant current function, and many manufacturers research chips and digital circuits to realize constant current function, but the cost is very high.

[0003] The prior art has the composition mode of the separated constant current circuit, however, the separated prior art uses more components, and cannot be miniaturized, therefore, the patent document "CN110062496A" discloses a "linear LED constant current circuit", which reduces the design difficulty of linear circuit, and the patent maintains the constant current function by turning on the shunt LED drive current when the LED drive voltage is higher than the rated input voltage of LED load through the voltage feedback circuit.

[0004] However, in the voltage feedback circuit, the existence of shunt current can cause additional power consumption, based on this, the utility model provides a kind of LED constant current circuit. UTILITY MODEL CONTENTS

[0005] The utility model aims at providing a kind of LED constant current circuit to solve the problems raised in the above background.

[0006] To achieve the above object, the utility model provides the following technical scheme:

[0007] A kind of LED constant current circuit, including input module, load module, PWM output unit, switch tube Q1, current-limiting resistance R3 and triode Q2;

[0008] The input module, load module and the D pole of switch tube are sequentially electrically connected, the PWM output unit is electrically connected with the G pole of the switch tube Q1, the S pole of the switch tube Q1 is electrically connected with one end of current-limiting resistance R3, the other end of current-limiting resistance R3 is grounded, the C pole of triode Q2 is electrically connected with the PWM output unit, the B pole of triode Q2 is electrically connected with the S pole of the switch tube Q1, and the E pole of triode Q2 is grounded;

[0009] The input module is used to output direct current to load module, the load module includes a plurality of light emitting diodes, the PWM output unit is used to output high level signal to the G pole of the switch tube Q1, the PN junction of the triode Q2 is fixed voltage drop, and the triode Q2 is used to maintain the voltage of the current-limiting resistance R3 unchanged.

[0010] Further technical solutions, the load module includes LED1, LED2 and LED3, the LED1, LED2 and LED3 are in series, the anode end of the LED1 is electrically connected with the output module, the cathode end of the LED3 is electrically connected with the D pole of the switch tube Q1.

[0011] Further technical solutions, the load module is connected with the capacitor C1 in parallel, one end of the capacitor C1 is electrically connected with the anode of the LED1, the other end of the capacitor C1 is electrically connected with the cathode of the LED3.

[0012] Further technical solutions, the PWM output unit is electrically connected with the resistor R1, one end of the resistor R1 is electrically connected with the PWM output unit, the other end of the resistor R1 is connected with the G pole of the switch tube Q1, and the second output end of the resistor R1 is connected with the C pole of the triode Q2.

[0013] Further technical solutions, the C pole of the triode Q2 is electrically connected with the resistor R4, one end of the resistor R4 is electrically connected with the C pole of the triode Q2, and the other end of the resistor R4 is electrically connected with the second output end of the resistor R1.

[0014] Further technical solutions, the switch tube Q1 is electrically connected with the resistor R2, one end of the resistor R2 is electrically connected with the G pole of the switch tube Q1, and the other end of the resistor R2 is electrically connected with the S pole of the switch tube Q1.

[0015] Further technical solutions, the current limiting resistor R3 is electrically connected with the capacitor C2, and the capacitor C2 is connected with the current limiting resistor R3 in parallel.

[0016] The beneficial effects of the utility model are as follows:

[0017] The utility model discloses a fixed voltage drop between the PN junction of triode Q2, makes the voltage between the B pole-E pole of triode Q2 keep invariant, makes the voltage of current limiting resistor R3 keep invariant, that is, the voltage drop of current limiting resistor R3 is clamped on the voltage between the B pole-E pole of triode Q2, and according to I = Vbe / R3, I is the current flowing through current limiting resistor R3, Vbe is the voltage between the B pole-E pole of triode Q2, and the current flowing through resistor R3 is fixed, so that the function of load module constant current is realized, compared with the shunt current using voltage feedback circuit, the additional power consumption can be reduced, and the working efficiency is improved.

[0018] Other features and advantages of the utility model will be described in detail in the subsequent specific embodiment part. DRAWINGS

[0019] Figure 1The circuit diagram of the utility model. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the utility model will be clearly and completely described in connection with the drawings in the embodiments of the utility model.

[0021] Please refer to Figure 1 ;

[0022] Embodiment 1

[0023] The LED constant current circuit comprises an input module, a load module, a PWM output unit, a switching tube Q1, a current-limiting resistor R3 and a triode Q2.

[0024] The D pole of the switching tube is electrically connected with the input module and the load module in sequence, the G pole of the switching tube Q1 is electrically connected with the PWM output unit, the S pole of the switching tube Q1 is electrically connected with one end of the current-limiting resistor R3, the other end of the current-limiting resistor R3 is grounded, the C pole of the triode Q2 is electrically connected with the PWM output unit, the B pole of the triode Q2 is electrically connected with the S pole of the switching tube Q1, and the E pole of the triode Q2 is grounded.

[0025] The input module is used to output direct current to the load module, the load module comprises a plurality of light emitting diodes, the PWM output unit is used to output a high level signal to the G pole of the switching tube Q1, the PN junction of the triode Q2 is a fixed voltage drop, and the triode Q2 is used to maintain the voltage of the current-limiting resistor R3 unchanged.

[0026] Specifically, the input module of the embodiment outputs direct current to the D pole of the switching tube Q1 through the load module, the PWM output unit outputs a high level signal to the G pole of the switching tube Q1, at this time, the G pole of the switching tube Q1 obtains a high level and there is a voltage difference between the S pole of the switching tube Q1, so the switching tube Q1 is turned on; the flow direction of the direct current is from the input module, through the load module, the switching tube Q1 and then through the current-limiting resistor R3; since the C pole of the triode Q2 is electrically connected with the PWM output unit, the B pole of the triode Q2 is electrically connected with the S pole of the switching tube Q1, the E pole of the triode Q2 is grounded, the voltage between the B pole and the E pole of the triode Q2 exceeds the threshold voltage of the triode Q2, at this time, the triode Q2 is turned on, and since there is a fixed voltage drop between the PN junction of the triode Q2, therefore, the voltage between the B pole and the E pole of the triode Q2 remains unchanged, so that the voltage of the current-limiting resistor R3 is maintained unchanged, that is, the voltage drop of the current-limiting resistor R3 is clamped on the voltage between the B pole and the E pole of the triode Q2, and according to I = Vbe / R3, I is the current flowing through the current-limiting resistor R3, Vbe is the voltage between the B pole and the E pole of the triode Q2, and the current flowing through the resistor R3 is fixed, so that the function of constant current of the load module is realized, compared with the shunt current using the voltage feedback circuit, the additional power consumption can be reduced and the working efficiency can be improved.

[0027] In some embodiments, the load module includes LED1, LED2 and LED3, LED1, LED2 and LED3 are connected in series, the anode end of LED1 is electrically connected with the output module, the cathode end of LED3 is electrically connected with the D pole of switch tube Q1, the further load module is electrically connected with capacitor C1 in parallel, one end of capacitor C1 is electrically connected with the anode of LED1, the other end of capacitor C1 is electrically connected with the cathode of LED3; the PWM output unit is electrically connected with resistor R1, one end of resistor R1 is electrically connected with the PWM output unit, the other end of resistor R1 is connected with the G pole of switch tube Q1, resistor R4 is electrically connected between the second output end of resistor R1 and the C pole of triode Q2, one end of resistor R4 is electrically connected with the C pole of triode Q2, the other end of resistor R4 is electrically connected with the second output end of resistor R1, further, switch tube Q1 is electrically connected with resistor R2, one end of resistor R2 is electrically connected with the G pole of switch tube Q1, the other end of resistor R2 is electrically connected with the S pole of switch tube Q1.

[0028] Specifically, capacitor C1 filters for LED1, LED2 and LED3, so that LED1, LED2 and LED3 get more stable voltage; by adjusting the resistance of resistor R1, resistor R3 and resistor R4, triode Q2 and switch tube Q1 can be turned on.

[0029] Further, current-limiting resistor R3 is electrically connected with capacitor C2, and capacitor C2 is connected with current-limiting resistor R3 in parallel.

[0030] Specifically, capacitor C2 filters the peak voltage of the PN junction of triode Q2, so that the reference voltage is more stable, and the constant current accuracy is improved.

[0031] It is apparent for those skilled in the art that the present application is not limited to the details of the foregoing exemplary embodiments, and the present application can be realized in other concrete forms without departing from the spirit or essential characteristics of the present application. Therefore, the embodiments should be considered in all aspects as illustrative and not restrictive, and the scope of the present application is defined by the appended claims rather than the foregoing description, and it is intended to encompass all changes falling within the meaning and range of equivalents of the elements of the claims. Any reference signs in the claims should not be deemed to limit the claims involved.

[0032] In addition, it should be understood that, although the present specification is described in terms of embodiments, not every embodiment contains only one independent technical solution, and the description manner of the specification is only for the sake of clarity, those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that those skilled in the art can understand.

Claims

1. An LED constant current circuit, characterized by, The input module, the load module, the PWM output unit, the switch tube Q1, the current-limiting resistor R3 and the triode Q2 are included. The input module, the load module and the D pole of the switch tube are sequentially electrically connected, the PWM output unit is electrically connected with the G pole of the switch tube Q1, the S pole of the switch tube Q1 is electrically connected with one end of the current-limiting resistor R3, the other end of the current-limiting resistor R3 is grounded, the C pole of the triode Q2 is electrically connected with the PWM output unit, the B pole of the triode Q2 is electrically connected with the S pole of the switch tube Q1, and the E pole of the triode Q2 is grounded. The input module is used to output direct current to the load module, the load module includes a plurality of light emitting diodes, the PWM output unit is used to output a high level signal to the G pole of the switch tube Q1, the PN junction of the triode Q2 is a fixed voltage drop, and the triode Q2 is used to maintain the voltage of the current-limiting resistor R3 unchanged.

2. The LED constant current circuit according to claim 1, wherein, The load module includes LED1, LED2 and LED3, the LED1, LED2 and LED3 are sequentially connected in series, one end of the anode of the LED1 is electrically connected with the output module, and one end of the cathode of the LED3 is electrically connected with the D pole of the switch tube Q1.

3. The LED constant current circuit according to claim 2, wherein, The load module is electrically connected in parallel with a capacitor C1, one end of the capacitor C1 is electrically connected with the anode of the LED1, and the other end of the capacitor C1 is electrically connected with the cathode of the LED3.

4. The LED constant current circuit of claim 1, wherein, The PWM output unit is electrically connected with a resistor R1, one end of the resistor R1 is electrically connected with the PWM output unit, the other end of the resistor R1 is connected with the G pole of the switch tube Q1, and the second output end of the resistor R1 is connected with the C pole of the triode Q2.

5. The LED constant current circuit according to claim 4, wherein, The C pole of the triode Q2 is electrically connected with a resistor R4, one end of the resistor R4 is electrically connected with the C pole of the triode Q2, and the other end of the resistor R4 is electrically connected with the second output end of the resistor R1.

6. The LED constant current circuit according to claim 1, wherein, The switch tube Q1 is electrically connected with a resistor R2, one end of the resistor R2 is electrically connected with the G pole of the switch tube Q1, and the other end of the resistor R2 is electrically connected with the S pole of the switch tube Q1.

7. The LED constant current circuit according to claim 1, wherein, The current-limiting resistor R3 is electrically connected with a capacitor C2, and the capacitor C2 is connected in parallel with the current-limiting resistor R3.

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