CN211429584U - Power supply control circuit and LED drive circuit - Google Patents

Abstract

The utility model discloses a power control circuit and LED drive circuit, the power control circuit includes the transistor, the input and the output of the transistor are the power input and the output of the power control circuit, the grid of the transistor receives the conduction control voltage; the utility model also discloses a LED drive circuit, this LED drive circuit include above-mentioned power control circuit and LED driver chip, and power control circuit's output is connected to LED driver chip's feeder ear. The utility model discloses a power control circuit and LED drive circuit utilize the output voltage of transistor to receive the characteristic of grid voltage restriction, make the transistor for normal open state and establish ties between power and LED driver chip's feed end, simple structure has restricted LED driver chip's input voltage effectively, has avoided LED driver chip's input voltage to be higher than output voltage and the situation of unusual work, provides convenience for the regulation and control that is shaded of LED.

Description

Power supply control circuit and LED drive circuit

Technical Field

The utility model relates to an electronic circuit technical field, in particular to power control circuit and LED drive circuit.

Background

IN view of the fact that the backlight control of the lcd of the mobile terminal uses an LED (Light Emitting Diode) as the backlight source, the voltage specification of the input voltage VLED _ IN of the LED driving chip driving the LED is 5-21V, and the input voltage is not a stable value under different conditions IN actual use. In the BL (back light) design, the serial-parallel mode of the LED lamps is not fixed, the number of LEDs in the lamp string varies depending on the model, the LED lamp string is connected between the output terminal and the feedback input terminal of the LED driving chip, and the voltage at the feedback input terminal of the LED driving chip is constant. When the number of the LED lamp strings is less than or equal to 8, the total voltage drop of the LED lamp strings is reduced, so that the voltage at the input end of the LED driving chip is reduced, the input voltage of the LED driving chip still is IN the specification of 5-21V, the input voltage of the LED driving chip is easier to be higher than the output voltage, when the voltage of VLED _ IN is higher, the condition that VLED _ IN is larger than output VLED _ OUT exists, and the LED driving chip VLED _ IN is larger than output VLED _ OUT and works abnormally.

IN practical designs, LED Driver requires a certain voltage difference between VLED _ IN and VLED _ OUT, and VLED _ IN cannot be larger than VLED _ OUT. If VLED _ IN is too large, the LED driving chip will operate abnormally, and BL will be abnormal.

SUMMERY OF THE UTILITY MODEL

In view of the above, an object of the present invention is to provide a power control circuit and an LED driving circuit, so as to reduce the input voltage of the LED driving chip and facilitate the backlight control of the LED.

According to an aspect of the present invention, there is provided a power control circuit, comprising:

a first input terminal connected to a power supply, a second input terminal connected to a gate control voltage source, and an output terminal;

a transistor including an input terminal connected to the first input terminal, an output terminal connected to an output terminal of the power control circuit, and a gate connected to the second input terminal,

a first resistor connected between the second input terminal and the gate of the transistor;

a second resistor connected between the gate of the transistor and ground;

when the power supply control circuit works, the transistor is in a normally open state.

Optionally, the method further comprises:

and the first capacitor is connected between the input end of the transistor and the ground.

Optionally, the method further comprises:

and the second capacitor is connected between the output end of the transistor and the ground.

Optionally, the method further comprises:

and the fuse is connected between the first input end of the power supply control circuit and the input end of the transistor.

Optionally, the method further comprises:

and the magnetic bead is connected between the first input end of the power supply control circuit and the input end of the transistor.

According to the utility model discloses an on the other hand provides a LED drive circuit, include:

according to the utility model provides a power supply control circuit;

the LED driving chip comprises a power supply end connected with the output end of the power supply control circuit, a power switch end and a feedback input end connected with the negative input end of the LED string;

an output end connected with the positive input end of the LED string;

the inductor is connected between the output end of the power supply control circuit and the power supply switch end of the LED driving chip;

and the anode of the Schottky diode is connected with the power switch end of the LED driving chip, and the cathode of the Schottky diode is connected with the output end of the LED driving circuit.

Optionally, the method further comprises:

and the third capacitor is connected between the feedback input end of the LED driving chip and the ground.

Optionally, the LED driving chip further includes an overvoltage protection terminal, and the overvoltage protection terminal is connected to the output terminal of the LED driving circuit.

Optionally, the method further comprises:

the third resistor is connected between the output end of the LED driving circuit and the overvoltage protection end of the LED driving chip in series;

and the fourth resistor is connected between the overvoltage protection end of the LED driving chip and the ground in series.

The utility model provides a power control circuit includes the transistor, and this transistor is connected between power and output, and for normally open state at power control circuit during operation, its output voltage receives grid voltage restriction to have the upper limit, utilizes the upper limit restriction output voltage value of the output voltage of transistor, can convert the output voltage of low upper limit into with the mains voltage of high upper limit simply effectively.

The utility model provides a LED drive circuit utilizes above-mentioned power control circuit to restrict power output to LED driver chip's voltage including above-mentioned power control circuit, restricts LED driver chip's input voltage's maximum value below output voltage, and guarantee LED driver chip's output voltage is greater than input voltage, ensures LED drive circuit's continuous stable work, and regulation and control in a poor light for LED facilitates.

Drawings

The above and other objects, features and advantages of the present invention will become more apparent from the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

fig. 1 shows a specific circuit diagram of a power control circuit according to an embodiment of the present invention;

fig. 2 is a specific circuit diagram of an LED driving circuit to which the power control circuit shown in fig. 1 is applied;

fig. 3 illustrates a test voltage waveform diagram of VLED _ IN and VLED _ IN1 according to the LED driving circuit shown IN fig. 2.

Detailed Description

Various embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Like elements in the various figures are denoted by the same or similar reference numerals. For purposes of clarity, the various features in the drawings are not necessarily drawn to scale.

The following detailed description of the embodiments of the present invention is provided with reference to the accompanying drawings and examples.

Fig. 1 shows a schematic structural diagram of a power control circuit according to an embodiment of the present invention. The power control circuit 10 of the embodiment of the present invention includes a transistor Q1, a capacitor C1, a capacitor C2, a resistor R1 and a resistor R2, and a first input end connected to a power supply for providing a voltage VLED _ IN, a second input end for providing a gate control voltage VGH, and an output end for outputting VLED _ IN 1.

The resistor R1 and the resistor R2 are connected in series between the second input end and the ground, the middle node of the resistor R1 and the resistor R2 is connected to the gate of the transistor Q1, when the circuit works, the transistor Q1 is normally open, the gate control voltage VGH is constant, the gate voltage of the transistor Q1 is constant, the resistance values of the resistor R1 and the resistor R2 are adjusted, the gate control voltage value of the transistor Q1 is properly adjusted, and the voltage of the output end of the transistor Q1 is limited by the gate voltage, and the gate voltage is stable, so that the voltage of the output end has a limit value, and the maximum output voltage of the output end.

The capacitor C1 is connected between the output end of the transistor Q1 and the ground, the capacitor C2 is connected between the input end of the transistor Q1 and the ground, and the capacitor C1 and the capacitor C2 respectively shape and filter the output voltage VLED _ IN1 of the transistor Q1 and the input voltage VLED _ IN of the transistor Q1, so that the influence of parasitic capacitance of the transistors is reduced, the waveform changes of the voltage VLED _ IN1 and the voltage VLED _ IN are steeper, and the jump between adjacent levels is quicker.

Fig. 2 shows a specific circuit diagram of an LED driving circuit to which the power control circuit shown in fig. 1 is applied. The LED driving circuit 100 includes a power control module 110, an LED driving chip 101, an inductor L2, a schottky diode D1, a resistor R3, a resistor R4, a light emitting diode string 120, and a capacitor C3.

The inductor L2 is connected in series between the output terminal of the power control module 110 and the anode of the schottky diode D1, the power switch terminal of the LED driver chip 101 is connected to the middle node between the inductor L2 and the schottky diode D1, and the inductor L2 is a boost inductor; the power supply terminal of the LED driving chip 101 is connected to the output terminal of the power control module 110 to receive the voltage VLED _ IN 1; the cathode of the schottky diode D1 outputs the voltage VOUT to the positive input of the led string 120; the resistor R3 and the resistor R4 are connected between the cathode of the Schottky diode D1 and the ground in series, and the sampling voltage VOUT of the middle node of the resistor R3 and the resistor R4 is connected to the overvoltage protection end of the LED driving chip 101; the negative input terminal of the LED string 120 is connected to the feedback input terminal FB of the LED driving chip 101; the capacitor C3 is connected between the negative input terminal of the led string 120 and ground, and can stabilize the voltage at the negative input terminal of the led string 120.

The main circuit structure of the power control module 110 is the same as the structure of the power control circuit 10 of the embodiment of the present invention, wherein the difference is that a fuse F1 and a magnetic bead L1 are included between the first input end and the input end of the transistor Q1. The fuse F1 can be used as an overcurrent protection component of the circuit, and the magnetic bead L1 plays a role in filtering in the circuit and can filter out high-frequency noise signals input into the power supply.

The LED driving circuit generally works under the condition of direct current, and includes a large amount of transistors in the actual electronic equipment, is provided with the high level power supply VGH as the gate control power supply of transistor in the equipment, and the VGH voltage is higher, can regard as the utility model discloses a required constant voltage source of power control circuit's transistor Q1 gate control power supply.

The utility model discloses power control circuit 10's resistance R1 and resistance R2 can suitably be adjusted, and node voltage in the middle of the adjustment makes transistor Q1's grid voltage can adjust, and system output voltage upper limit can suitably be adjusted promptly, can make the utility model discloses power control circuit 10 can be applicable to multiple LED driver chip and require. Or only a small amount of light-emitting diode particles are contained in the light-emitting diode string, the total voltage of the light-emitting diode string is reduced, so that the output end voltage of the LED driving chip is low, the resistance values of the resistor R1 and the resistor R2 can be adjusted, the grid voltage of the transistor Q1 is reduced, and the upper limit of the output voltage of the transistor Q1 is reduced, so that the upper limit of the power supply end voltage of the LED driving chip is reduced, and the condition that the input of the LED driving chip is larger than the output of.

Fig. 3 illustrates a test voltage waveform diagram of VLED _ IN and VLED _ IN1 according to the LED driving circuit shown IN fig. 2. When the input power voltage VLED _ IN is lower than 16V, the voltage value of VLED _ IN1 follows the voltage of VLED _ IN, wherein the voltage difference is 0.263V, the voltage difference mainly comes from the conduction voltage drops of the transistor Q1 and the Schottky diode D1, when the input power voltage VLED _ IN is higher than 16V, the voltage value of VLED _ IN1 is kept at 15.67V, and as the power voltage continues to rise, VLED _ IN1 only slightly rises and is lower than 16V, and the voltage level is step-type, and the jump between adjacent levels is rapid. The utility model discloses the LED drive circuit who implements converts 5-21V's mains voltage into 5-16V's output voltage and exports to LED driver chip's feed end, has effectively reduced LED driver chip's feed end voltage upper limit, has avoided LED driver chip's output voltage to be less than the production of input voltage's the situation, has ensured LED drive circuit's normal work.

To the heating factor of system, will the utility model discloses LED drive circuit 100 inserts the finished product circuit board, and its operating temperature of actual measurement when inputing 21V mains voltage, the temperature of actual measurement is 49 ℃, is less than 65 ℃, and it is lower to generate heat, possesses the practicality.

The utility model discloses a power control circuit connects between power and LED driver chip's input, can restrict power output to LED driver chip's voltage maximum value, restricts LED driver chip's input voltage's maximum value, makes it be less than LED driver chip's output terminal voltage to stop LED driver chip input voltage and be greater than output voltage's phenomenon, avoid LED driver chip's abnormal work, avoid liquid crystal display to be shaded unusually.

In accordance with the embodiments of the present invention as set forth above, these embodiments are not exhaustive and do not limit the invention to the precise embodiments described. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, to thereby enable others skilled in the art to best utilize the invention and its various embodiments with various modifications as are suited to the particular use contemplated. The present invention is limited only by the claims and their full scope and equivalents.

Claims (9)

1. A power control circuit, comprising:

a first input terminal connected to a power supply, a second input terminal connected to a gate control voltage source, and an output terminal;

a transistor including an input terminal connected to the first input terminal, an output terminal connected to an output terminal of the power control circuit, and a gate connected to the second input terminal,

a first resistor connected between the second input terminal and the gate of the transistor;

a second resistor connected between the gate of the transistor and ground;

when the power supply control circuit works, the transistor is in a normally open state.

2. The power control circuit of claim 1, further comprising:

and the first capacitor is connected between the input end of the transistor and the ground.

3. The power control circuit of claim 1, further comprising:

and the second capacitor is connected between the output end of the transistor and the ground.

4. The power control circuit of claim 1, further comprising:

and the fuse is connected between the first input end of the power supply control circuit and the input end of the transistor.

5. The power control circuit of claim 1, further comprising:

and the magnetic bead is connected between the first input end of the power supply control circuit and the input end of the transistor.

6. An LED driving circuit, comprising:

the power supply control circuit according to any one of claims 1 to 5;

the LED driving chip comprises a power supply end connected with the output end of the power supply control circuit, a power switch end and a feedback input end connected with the negative input end of the LED string;

an output end connected with the positive input end of the LED string;

the inductor is connected between the output end of the power supply control circuit and the power supply switch end of the LED driving chip;

and the anode of the Schottky diode is connected with the power switch end of the LED driving chip, and the cathode of the Schottky diode is connected with the output end of the LED driving circuit.

7. The LED driving circuit according to claim 6, further comprising:

and the third capacitor is connected between the feedback input end of the LED driving chip and the ground.

8. The LED driver circuit according to claim 6,

the LED driving chip further comprises an overvoltage protection end, and the overvoltage protection end is connected with the output end of the LED driving circuit.

9. The LED driving circuit according to claim 8, further comprising:

the third resistor is connected between the output end of the LED driving circuit and the overvoltage protection end of the LED driving chip in series;

and the fourth resistor is connected between the overvoltage protection end of the LED driving chip and the ground in series.

Images