CN210725411U

CN210725411U - LED drive circuit

Info

Publication number: CN210725411U
Application number: CN201920386028.1U
Authority: CN
Inventors: 林星宇; 张腾; 蔡拥军; 姚云龙
Original assignee: Hangzhou Silan Microelectronics Co Ltd
Current assignee: Hangzhou Silan Microelectronics Co Ltd
Priority date: 2019-03-25
Filing date: 2019-03-25
Publication date: 2020-06-09
Anticipated expiration: 2029-03-25

Abstract

The embodiment of the utility model discloses LED drive circuit for according to input voltage drive LED lamp, LED drive circuit includes: the control circuit is used for generating a control signal according to the input voltage; and the constant current circuit is connected with the LED lamp in series and used for adjusting the driving current flowing through the LED lamp according to the control signal, so that the constant current circuit is applicable to different input voltage ranges, ensures that the input power is in a rated power range, and improves the reliability and the safety of a system.

Description

LED drive circuit

Technical Field

The utility model relates to a LED lighting technology field, concretely relates to LED drive circuit.

Background

Compared with the traditional Light source, the Light Emitting Diode (LED) has the advantages of small volume, energy saving, long service life, high brightness, environmental protection and the like, and is widely used for indoor and outdoor illumination.

The brightness of the LED lamp is related to the driving current, and the corresponding driving schemes are a linear driving scheme and a switching driving scheme. The two respectively adopt the modes of a linear regulating transistor and a switch control transistor to regulate the driving current.

Fig. 1 shows a schematic circuit diagram of an LED driving circuit according to the prior art. As shown in fig. 1, the LED driving circuit 100 includes an ac current source 101, a rectifier bridge 102, an input capacitor Cin, a current sampling resistor Rs, and a linear constant current module 110. An input voltage Vin is provided between two output terminals of the rectifier bridge 102. The LED lamp 103 is connected in series with the linear constant current module 110 and the current sampling resistor Rs between two output terminals of the rectifier bridge 103.

The linear constant current module 110 includes a power tube 112 and an amplifier 111. The amplifier 111 compares a current sampling signal obtained by the current sampling resistor Rs with a reference voltage Vref, and generates a driving signal according to a difference between the two signals to control a driving current flowing through the power transistor 112. After the circuit is stabilized, the driving current controlled by the linear constant current module 110 has a value of Vref/Rs.

In the LED driving circuit, the input voltage Vin is required to be greater than the load voltage of the LED lamp, otherwise, the rated current cannot be output. Meanwhile, because the voltage drop on the linear constant current chip is the difference value between the input voltage and the output load voltage, the power consumption on the linear constant current system chip is directly related to the input voltage, and the higher the input voltage is, the lower the efficiency is. In order to ensure sufficient luminous efficiency, the input voltage range of the conventional LED driving circuit is generally 220Vac to 240Vac or 110Vac to 130Vac, and when the input voltage exceeds the upper limit of the input voltage range, the input power is greater than the rated power, which further affects the service life of the LED lamp and the driving circuit, and the reliability and safety of the system.

SUMMERY OF THE UTILITY MODEL

In view of this, the utility model is used for provide a LED drive circuit, applicable in the input voltage scope of difference, ensure that input power is in the rated power scope, improve the reliability and the security of system.

According to the utility model discloses a first aspect provides a LED drive circuit for according to input voltage drive LED lamp, LED drive circuit includes: the control circuit is used for generating a control signal according to the input voltage; and the constant current circuit is connected with the LED lamp in series and used for regulating the driving current flowing through the LED lamp according to the control signal so as to stabilize the output power of the LED lamp within a rated power range.

Preferably, the control signal is a voltage signal, and the constant current circuit includes: the first power tube is used for controlling the driving current flowing through the LED lamp; the first current sampling resistor is connected with the first power tube in series and used for providing a first current sampling signal; and a first amplifier for adjusting the driving current according to the control signal and the first current sampling signal.

Preferably, the control signal is a current signal, and the constant current circuit includes: the second power tube is used for controlling the driving current flowing through the LED lamp; the second current sampling resistor is connected with the second power tube in series and used for providing a second current sampling signal; a second amplifier for comparing a reference voltage with a voltage feedback signal to adjust the drive current; and the first feedback resistor is connected between the inverting input end of the second amplifier and the source electrode of the second power tube, wherein the first feedback resistor is used for superposing the control signal and the second current sampling signal to obtain the voltage feedback signal.

Preferably, the control circuit includes: the voltage detection module is used for sampling the input voltage to obtain a voltage sampling signal; and the reference control module is used for obtaining the control signal according to the voltage sampling signal.

Preferably, the reference control module includes: the current generation unit is used for generating a regulating current according to the voltage sampling signal; and the output unit is connected with the current generation unit and an output node and used for providing the control signal according to the regulating current.

Preferably, the current generating unit includes n current subunits, n being a natural number greater than zero, each current subunit being configured to convert a voltage difference between the voltage sampling signal and a corresponding threshold voltage into a current signal, wherein the threshold voltage is used to characterize a maximum value or a minimum value of a corresponding voltage interval.

Preferably, when the voltage sampling signal is in a first voltage interval, the control signal controls the driving current to decrease with an increase of the voltage sampling signal, and when the voltage sampling signal is in a second voltage interval, the control signal controls the driving current to increase with an increase of the voltage sampling signal, and a minimum value of the second voltage interval is equal to a maximum value of the first voltage interval.

Preferably, the LED driving circuit further includes: when the voltage sampling signal is located in a third voltage interval, the control signal controls the driving current to be reduced along with the increase of the voltage sampling signal, and the minimum value of the third voltage interval is equal to/larger than the maximum value of the second voltage interval.

Preferably, the first voltage interval and the second voltage interval are located in a transition interval between the first rated voltage interval and the second rated voltage interval.

Preferably, the current generating unit includes: and the first current subunit is positioned on the first current path and used for obtaining a first current according to the voltage difference between the voltage sampling signal and a first threshold voltage representing the minimum value of the first voltage interval, wherein the first current subunit is connected to the output node and used for outputting the first current as the regulating current.

Preferably, the current generation unit further includes: and the second current subunit is positioned on a second current path, is connected with the first current subunit, and is used for obtaining a second current according to a voltage difference between the voltage sampling signal and a second threshold voltage representing a minimum value of the second voltage interval, wherein the second current subunit is used for compensating the first current according to the second current.

Preferably, the current generation unit further includes: and the third current subunit is positioned on a third current path and used for obtaining a third current according to a voltage difference between the voltage sampling signal and a third threshold voltage representing a minimum value of the third voltage interval, wherein the third current subunit is connected to the output node and is used for outputting the third current as the regulating current.

Preferably, the first current subunit, the second current subunit, and the third current subunit respectively include: a first transistor and a second feedback resistor located on respective current paths; and a voltage division module for comparing the voltage sampling signal with the threshold voltage to control the turning on and off of the first transistor.

Preferably, the voltage dividing module includes a plurality of voltage dividing resistors, and the threshold voltage is adjusted by adjusting resistance values of the plurality of voltage dividing resistors.

Preferably, the first transistor is an NPN type bipolar transistor.

Preferably, the output unit includes: and the first output resistor is connected between the reference voltage and the output node in series, and the first output resistor obtains the control signal in a voltage form according to the regulating current.

Preferably, the output unit includes a second transistor and a third transistor, wherein the second transistor and the third transistor constitute a first current mirror for converting the adjustment current into the control signal in a current form.

Preferably, the first current sub-unit, the second current sub-unit, and the third current sub-unit respectively include: a fourth transistor, a third feedback resistor, and a fifth transistor located on respective current paths; a third amplifier for driving the fourth transistor according to the voltage sampling signal and a potential of an intermediate node between the fourth transistor and the third feedback resistor; and a fourth amplifier for driving the third transistor in accordance with the threshold voltage and a potential of an intermediate node of the fifth transistor and the third feedback resistor.

Preferably, the current generation unit further includes: a sixth transistor connected in series on the first current path; and a fifth amplifier, wherein a positive input terminal of the fifth amplifier is configured to receive the second threshold voltage, an negative input terminal of the fifth amplifier is connected to the first terminal of the sixth transistor, and an output terminal of the fifth amplifier is connected to the control terminal of the sixth transistor, and the fifth amplifier is configured to drive the sixth transistor according to the second threshold voltage to limit the current value of the first current.

Preferably, the current generation unit further includes a seventh transistor and an eighth transistor, wherein the seventh transistor and the eighth transistor constitute a second current mirror so as to mirror the second current to the first current path to compensate for the first current.

Preferably, the fourth transistor, the fifth transistor and the sixth transistor are N-type metal oxide semiconductor field effect transistors, respectively, and the seventh transistor and the eighth transistor are P-type metal oxide semiconductor field effect transistors, respectively.

Preferably, the output unit includes ninth to twelfth transistors and a second output resistor, wherein the ninth transistor, the tenth transistor, the eleventh transistor and the twelfth transistor constitute a third current mirror, a power supply terminal of the third current mirror is connected to a power supply voltage, an input terminal of the third current mirror is connected to the output node, the second output resistor is connected in series between a reference voltage and an output terminal of the third current mirror, the third current mirror is configured to mirror the adjustment current to the second output resistor, and the second output resistor obtains the control signal in the form of a voltage according to the adjustment current.

Preferably, the ninth transistor and the tenth transistor are P-type metal oxide semiconductor field effect transistors, respectively, and the eleventh transistor and the twelfth transistor are N-type metal oxide semiconductor field effect transistors, respectively.

Preferably, the output unit includes a thirteenth transistor and a fourteenth transistor, wherein the thirteenth transistor and the fourteenth transistor constitute a fourth current mirror, a supply terminal of the fourth current mirror is connected to a power supply voltage, and an input terminal is connected to the output node to convert the regulated current into the control signal in the form of a current.

To sum up, the utility model discloses LED drive circuit controls drive current and reduces along with input voltage's increase in the first voltage interval that input voltage is greater than rated voltage interval, guarantees that input power is located the rated power within range all the time, improves circuit reliability and life to improve the utilization ratio of lamp pearl, reduce the complete machine cost, raise the efficiency.

Furthermore, the utility model discloses LED drive circuit increases along with input voltage's increase in the second voltage interval after input voltage increases to first voltage interval to the work that the system can be stable when guaranteeing that input voltage increases to next rated voltage interval can make LED drive circuit be applicable to the input voltage of various voltage ranges, make being applicable to of the linear drive scheme of LED more wideer or more complicated electric wire netting, practice thrift the cost.

Drawings

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

fig. 1 shows a schematic circuit diagram of an LED driving circuit according to the prior art;

fig. 2 shows a schematic block diagram of an LED drive circuit according to an embodiment of the present invention;

fig. 3 shows a schematic circuit diagram of an LED driving circuit according to a first embodiment of the present invention;

fig. 4 shows a schematic circuit diagram of an LED driving circuit according to a second embodiment of the present invention;

fig. 5 shows a schematic circuit diagram of a reference control module according to a first embodiment of the invention;

fig. 6 shows another schematic circuit diagram of a reference control module according to a first embodiment of the invention;

fig. 7 shows a schematic circuit diagram of a reference control module according to a second embodiment of the invention;

fig. 8 shows another schematic circuit diagram of a reference control module according to a second embodiment of the invention;

fig. 9 shows a schematic waveform diagram between a voltage sampling signal and a control signal according to the first embodiment of the present invention;

fig. 10 shows another schematic waveform diagram between the voltage sampling signal and the control signal according to the first embodiment of the present invention;

fig. 11 shows a schematic waveform diagram between a voltage sampling signal and a control signal according to a second embodiment of the present invention;

fig. 12 shows another schematic waveform diagram between the voltage sampling signal and the control signal according to the second embodiment of the present invention.

Detailed Description

The present invention will be described below based on examples, but the present invention is not limited to only these examples. In the following detailed description of the present invention, certain specific details are set forth in detail. It will be apparent to those skilled in the art that the present invention may be practiced without these specific details. Well-known methods, procedures, and procedures have not been described in detail so as not to obscure the present invention. The figures are not necessarily drawn to scale.

In this application, the term "LED lamp" is, for example, an LED lamp string formed by connecting a plurality of LEDs in series. If multiple LEDs are formed into a string of LEDs, the cathode of the previous LED in the string is connected to the anode of the next LED. The anode of the LED lamp refers to the anode of the first LED lamp in the LED lamp string, and the cathode of the LED lamp refers to the cathode of the last LED lamp in the LED lamp string.

The present invention may be presented in a variety of forms, some of which are described below.

Fig. 2 shows a schematic block diagram of an LED driving circuit according to an embodiment of the present invention. As shown in fig. 2, the LED driving circuit 200 includes an ac current source 201, a rectifier bridge 202, an input capacitor Cin, a constant current circuit 230, and a control circuit 240. The rectifier bridge 202 is used for rectifying the ac power into dc power, and an input voltage Vin is provided between two output terminals of the rectifier bridge 202, and the input voltage Vin supplies power to the LED lamp 203. The input capacitor Cin smoothly filters the input voltage Vin.

The utility model discloses a basic implementation scheme as follows: when the input voltage Vin is in the first rated voltage interval and the second rated voltage interval, controlling the driving current flowing through the LED lamp 203 to be constant; when the input voltage Vin is in a first voltage interval, controlling the driving current flowing through the LED lamp 203 to decrease with the increase of the input voltage Vin; when the input voltage Vin is in a second voltage interval, the driving current flowing through the LED lamp 203 is controlled to increase with the increase of the input voltage Vin, the first voltage interval and the second voltage interval are in a transition interval of the first rated voltage interval and the second rated voltage interval, and the minimum value of the second voltage interval is equal to the maximum value of the first voltage interval.

Specifically, as shown in fig. 2, the control circuit 240 is configured to provide a control signal to the constant current circuit 230 according to the input voltage Vin, and the constant current circuit 230 is connected in series with the LED lamp 203 and configured to adjust the driving current flowing through the LED lamp 203 according to the control signal.

The control circuit 240 includes a voltage detection module 210 and a reference control module 220, the voltage detection module 210 is connected to the first output terminal of the rectifier bridge 202 to receive the input voltage Vin, and the voltage detection module 210 is configured to detect the input voltage Vin to obtain a voltage sampling signal. The reference control module 220 is connected to the voltage detection module 210, and is configured to obtain a control signal according to the voltage sampling signal.

Fig. 3 and 4 show circuit configuration diagrams of a first embodiment and a second embodiment, respectively, based on the basic implementation of the present invention, the main difference between which lies in the form of the control signal. If the control signal is a voltage signal, the reference voltage of the constant current circuit 230 is adjusted according to the control signal, and then the driving current is adjusted; if the control signal is a current signal, the current sampling signal of the constant current circuit 230 is adjusted according to the control signal, and then the driving current is adjusted. It should be noted that these two embodiments are only two specific circuit implementations based on the concept of the present invention, and do not limit the basic implementation scheme of the present invention.

As shown in fig. 3, the LED driving circuit 300 includes an ac current source 301, a rectifier bridge 302, an LED lamp 303, an input capacitor Cin, a voltage detection module 310, a reference control module 320, and a constant current circuit 330. The ac current source 301, the rectifier bridge 302, the LED lamp 303, and the input capacitor Cin are the same as the ac current source 201, the rectifier bridge 202, the LED lamp 203, and the input capacitor Cin shown in fig. 2 in structure and function, and are not described herein again.

The voltage detection module 310 includes voltage dividing resistors R1 and R2, and an amplifier U1. The non-inverting input of the amplifier U1 is connected to the middle node of the resistor R1 and the resistor R2, the inverting input of the amplifier U1 is connected to the output, and the output of the amplifier U1 is connected to the reference control block 320 to provide the voltage sampling signal V1.

The reference control module 320 is used for obtaining a control signal Vref1 in the form of voltage according to the voltage sampling signal V1. The constant current circuit 330 includes an amplifier U2, a power tube M1, and a current sampling resistor Rs 1. The power tube M1 and the current sampling resistor Rs1 are connected in series between the LED lamp 303 and ground, and an intermediate node between the power tube M1 and the current sampling resistor Rs1 is used to provide a first current sampling signal. The amplifier U2 has a non-inverting input terminal for receiving the control signal Vref1, an inverting input terminal for receiving the first current sampling signal, and the amplifier U2 is configured to drive the power transistor M1 according to the control signal Vref1 and the first current sampling signal to adjust the driving current, for example, the constant current value Iout of the driving current is Vref1/Rs 1.

As can be seen from the above equation, the constant current value of the driving current Iout can be adjusted by adjusting the magnitude of the control signal Vref 1. As shown in FIG. 9, when V1 ≦ Va, the control signal Vref1 is unchanged and the driving current is kept constant; when Va < V1 ≦ Vb, the control signal Vref1 decreases with an increase in the voltage sampling signal V1; when Vb < V1 ≦ Vc, the control signal Vref1 increases with an increase in the voltage sampling signal V1, and when the control signal Vref1 increases to the preset voltage value Vref, the control signal Vref1 is held constant; when V1> Vc, the control signal Vref1 decreases with an increase in the voltage sampling signal V1.

Fig. 10 shows another schematic waveform diagram between the voltage sampling signal and the control signal according to the first embodiment of the present invention. As shown in fig. 10, in another embodiment, the voltage sampling signal V1 has increased to the third threshold voltage Vc before the control signal Vref1 is not increased to the preset voltage value Vref, and the control signal Vref1 is decreased with the increase of the voltage sampling signal V1.

Wherein Va is a first threshold voltage for characterizing a minimum value of the first voltage interval; vb is a second threshold voltage and is used for representing the minimum value of a second voltage interval; vc is a third threshold voltage, which is used to represent the minimum value of the third voltage interval. Wherein the minimum value of the second voltage interval is equal to the maximum value of the first voltage interval, and the minimum value of the third voltage interval is greater than/equal to the maximum value of the second voltage interval.

The threshold voltage may be preset, for example, a rated voltage range of an existing LED driving circuit generally includes a first rated voltage interval (e.g., 110Vac to 130Vac) and a second rated voltage interval (e.g., 220Vac to 240Vac), the first threshold voltage and the second threshold voltage are located in a transition interval between the first rated voltage interval and the second rated voltage interval, and the second threshold voltage is greater than the first threshold voltage. Of course, in a preferred embodiment, a third nominal voltage interval is also included, the third threshold voltage being located in a transition interval between the second nominal voltage interval and the third nominal voltage interval.

When the voltage sampling signal V1 is greater than the first threshold voltage Va (i.e. the input voltage is greater than the maximum voltage in the first rated voltage interval), the control signal Vref1 decreases with an increase in the voltage sampling signal V1, so as to reduce the driving current flowing through the LED lamp, reduce the input power, ensure that the input power is always within the range of the rated power in this interval, and improve the reliability and safety of the system. When the voltage sampling signal V1 is greater than the second threshold voltage Vb, in order to ensure that the system can operate stably when the input voltage increases to the second rated voltage interval, the control signal Vref1 increases with the increase of the voltage sampling signal V1 during the period when the voltage sampling signal V1 is greater than the second threshold voltage and less than the third threshold voltage Vc, the control signal Vref1 is kept constant when the control signal Vref1 increases to the preset voltage value Vref to ensure that the system can operate stably when the input voltage is in the second rated voltage interval, and when the voltage sampling signal V1 is greater than the third threshold voltage Vc, the control signal Vref1 decreases with the increase of the voltage sampling signal V1 to reduce the driving current flowing through the LED lamp and reduce the input power. Or the voltage sampling signal V1 has increased to the third threshold voltage Vc before the control signal Vref1 is not increased to the preset voltage value Vref, when the control signal Vref1 is decreased as the voltage sampling signal V1 is increased. When the input voltage is larger than the maximum voltage of the second rated voltage interval, the input power is always within the range of the rated power, and the reliability and the safety of the system are improved.

As shown in fig. 4, the LED driving circuit 400 includes an ac current source 401, a rectifier bridge 402, an LED lamp 403, an input capacitor Cin, a voltage detection module 410, a reference control module 420, and a constant current circuit 430. The ac current source 401, the rectifier bridge 402, the LED lamp 403, the voltage detection module 410, and the input capacitor Cin are the same as the ac current source 301, the rectifier bridge 302, the LED lamp 303, the voltage detection module 310, and the input capacitor Cin shown in fig. 3 in structure and function, and are not described herein again.

The reference control module 420 is configured to obtain the control signal Io according to the voltage sampling signal V1. The constant current circuit 430 includes a power tube M2, a current sampling resistor Rs2, an amplifier U3, and a feedback resistor R3. The power tube M2 and the current sampling resistor Rs2 are connected in series between the LED lamp 403 and ground, and the intermediate node of the power tube M2 and the current sampling resistor Rs2 is used to provide a second current sampling signal. The amplifier U3 has a non-inverting input for receiving a reference voltage Vref2 and an inverting input for receiving a voltage feedback signal. A feedback resistor R3 is connected between the inverting input and the output of amplifier U3. In the present embodiment, the amplifier U3 superimposes the control signal Io on the second current sampling signal to obtain a voltage feedback signal, and drives the power transistor M2 according to the reference voltage Vref2 and the voltage feedback signal to adjust the driving current, for example, the constant current value of the driving current Iout is (Vref2-Io × R3)/Rs 2.

As can be seen from the above equation, the constant current value of the driving current Iout can be adjusted by adjusting the magnitude of the control signal Io. As shown in FIG. 11, when V1 is less than or equal to Va, the control signal Io is 0, and the driving current is kept constant; when Va < V1 ≦ Vb, the control signal Io increases with the increase of the voltage sampling signal V1, and the driving current Iout decreases with the increase of the voltage sampling signal V1; when Vb < V1 ≦ Vc, the control signal Io decreases with the increase of the voltage sampling signal V1, and when the control signal Io decreases to 0, the control signal Io is kept unchanged; when V1> Vc, the control signal Io increases with an increase in the voltage sampling signal V1.

Similarly, Va is a first threshold voltage, which is used to characterize the minimum value of the first voltage interval; vb is a second threshold voltage and is used for representing the minimum value of a second voltage interval; vc is a third threshold voltage, which is used to represent the minimum value of the third voltage interval. Wherein the minimum value of the second voltage interval is equal to the maximum value of the first voltage interval, and the minimum value of the third voltage interval is greater than/equal to the maximum value of the second voltage interval.

Fig. 12 shows another schematic waveform diagram between the voltage sampling signal and the control signal according to the second embodiment of the present invention. As shown in fig. 12, in another embodiment, the voltage sampling signal V1 has increased to the third threshold voltage Vc before the control signal Io is not decreased to 0, at which time the control signal Io increases with the increase of the voltage sampling signal V1.

The utility model discloses LED drive circuit controls drive current and reduces along with input voltage's increase in the first voltage interval that input voltage is greater than rated voltage interval, guarantees that input power is located the rated power within range all the time, improves circuit reliability and life to improve the utilization ratio of lamp pearl, reduce the complete machine cost, raise the efficiency.

Furthermore, the utility model discloses LED drive circuit increases along with input voltage's increase in the second voltage interval after input voltage increases to the first voltage interval to the work that the system can be stable when guaranteeing that input voltage increases to the next rated voltage interval can make LED drive circuit be applicable to the input voltage of various voltage ranges, practices thrift manufacturing cost.

Fig. 5 shows a circuit structure diagram of a reference control module according to a first embodiment of the present invention, and as shown in fig. 5, the reference control module 520 includes a current generating unit 501 and an output unit 502. The current generating unit 501 is configured to generate a regulating current Ig according to the voltage sampling signal V1, an intermediate node between the output unit 502 and the current generating unit 501 is an output node, and is configured to provide the regulating current Ig, and the output unit 502 is configured to provide the control signal Vref1 according to the regulating current Ig.

Further, the current generating unit 501 includes n current sub-units connected in parallel, where n is a natural number greater than zero. Each current subunit is configured to convert a difference between the voltage sampling signal and the corresponding threshold voltage into a current signal, and obtain the adjustment current Ig according to the current signal.

As a non-limiting example, the current generating unit 501 includes a current subunit 511 located on a first current path, and a current subunit 512 located on a second current path. The current subunit 511 is configured to obtain a first current I1 according to a voltage difference between the voltage sampling signal V1 and the first threshold voltage Va, and the current subunit 512 is configured to obtain a second current I2 according to a voltage difference between the voltage sampling signal V1 and the second threshold voltage Vb. The current subunit 511 is connected to the output node for outputting the first current I1 as a regulated current Ig.

The current subunit 511 includes a transistor Q1 and a feedback resistor R21 connected in series on the first current path, and a voltage dividing module composed of voltage dividing resistors R13 and R14 connected between the voltage sampling signal V1 and ground, and an intermediate node between the voltage dividing resistor R13 and the voltage dividing resistor R14 is used for providing a turn-on signal to the transistor Q1. The voltage dividing module is configured to turn on the transistor Q1 when the voltage sampling signal V1 is greater than the first threshold voltage Va, and a current I1 flowing through the transistor Q1 is equal to (Vbq1-Vbeq1)/R21, where Vbq1 is a base voltage of the transistor Q1, and Vbeq1 is a be junction voltage of the transistor Q1, so that the adjustment current Ig is equal to I1 (Vbq1-Vbeq 1)/R21.

The output unit 502 includes an output resistor R31 connected between a reference voltage Vref and an output node, and the output resistor R31 provides a control signal Vref1 at the output node according to a regulation current, for example, Vref 1-Vref-Ig R31-Vref- (Vbq1-Vbeq1) (R31/R21). From the above equation, the larger the voltage difference between the voltage sampling signal V1 and the first threshold voltage Va, the larger the base voltage of the transistor Q1, and thus the smaller the control signal Vref 1.

The current subunit 512 includes a transistor Q2 and a feedback resistor R22 connected in series on the second current path, a first terminal of the transistor Q2 is connected to the control terminal of the transistor Q1 for providing a compensation signal to the transistor Q1 when turned on.

The current subunit 512 further includes a voltage dividing module composed of a voltage dividing resistor R11 and a voltage dividing resistor R12 connected in series between the voltage sampling signal V1 and ground, and an intermediate node between the voltage dividing resistor R11 and the voltage dividing resistor R12 is used to provide a turn-on signal to the transistor Q2. The voltage dividing module is configured to turn on the transistor Q2 when the voltage sampling signal V1 is greater than the second threshold voltage Vb, and a current I2 flowing through the transistor Q2 is (Vbq2-Vbeq2)/R22, where Vbq2 is a base voltage of the transistor Q2, and Vbeq2 is a be junction voltage of the transistor Q2. The larger the voltage difference between the voltage sampling signal V1 and the second threshold voltage Vb, the larger the base voltage of the transistor Q2, and then the larger the second current I2, the larger the compensation effect of the second current I2 on the transistor Q1, so that the control signal Vref1 ═ Vref- [ V1-I2 × R13-V1R 13/(R13+ R14) -Vbeq1] × R31/R21 when the voltage sampling signal V1 is greater than the second threshold voltage Vb can be obtained, and it can be seen from the above formula that the larger the second current I2, the larger the control signal Vref1, and therefore the control signal Vref1 increases with the increase of the voltage sampling signal V1.

As shown in fig. 9, as the voltage difference between the voltage sampling signal V1 and the second threshold voltage Vb increases, the base voltage of the transistor Q1 gradually decreases, and when the base voltage of the transistor Q1 is smaller than the on threshold of the transistor Q1, the transistor Q1 is turned off, and at this time, the control signal Vref1 is equal to the reference voltage Vref, and the control signal Vref1 is kept constant.

In some embodiments, the current generating unit 501 further comprises a current sub-unit 513 in the third current path, the current sub-unit 513 is configured to provide a third current I3 according to a voltage difference between the voltage sampling signal V1 and a third threshold voltage Vc.

As shown in fig. 5, the current subunit 513 includes a transistor Q3, a feedback resistor R23, and a voltage dividing module composed of a voltage dividing resistor R15 and a voltage dividing resistor R16 connected in series between the voltage sampling signal V1 and ground, and an intermediate node between the voltage dividing resistor R15 and the voltage dividing resistor R16 is used for providing a turn-on signal to the transistor Q3. The voltage dividing module is configured to turn on the transistor Q3 when the voltage sampling signal V1 is greater than the third threshold voltage Vc, and a current I3 flowing through the transistor Q3 is (Vbq3-Vbeq3)/R23, where Vbq3 is a base voltage of the transistor Q3, and Vbeq3 is a be junction voltage of the transistor Q3.

Since the transistor Q3 is also connected to the output node, the control signal Vref 1-Vref-Ig R31-Vref- (Vbq3-Vbeq3) (R31/R23) can be obtained at this time. From the above equation, the larger the voltage difference between the voltage sampling signal V1 and the third threshold voltage Vc, the larger the base voltage of the transistor Q3, and thus the smaller the control signal Vref 1.

As shown in fig. 10, in another embodiment, the transistor Q1 and the transistor Q3 are both in the on state, so the adjusting current Ig is the combined current of the first current I1 and the third current I3, and the control signal Vref1 is decreased before the reference voltage Vref is increased due to the third current I3, i.e., as the voltage sampling signal V1 is increased.

As shown in fig. 5, the first threshold voltage Va is Vbeq1 (R13+ R14)/R14, the second threshold voltage Vb is Vbeq2 (R11+ R12)/R12, and the third threshold voltage Vc is Vbeq3 (R15+ R16)/R16, so that the values of the first threshold voltage Va and the third threshold voltage Vc can be changed by changing the resistance values of the voltage dividing resistors R11 to R16, and the magnitude of the threshold voltage is actually changed, so that the magnitude of the threshold voltage can be changed by preset conditions.

Fig. 6 shows another circuit configuration diagram of the reference control module according to the first embodiment of the present invention. As shown in fig. 6, the reference control module 620 includes a current generating unit 601 and an output unit 602. The current generating unit 601 is configured to generate a regulating current Ig according to the voltage sampling signal V1, a first connection point between the output unit 602 and the current generating unit 601 is an output node, and is configured to provide the regulating current Ig, and the output unit 602 is configured to provide the control signal Vref1 according to the regulating current Ig.

Further, the current generating unit 601 includes n current sub-units connected in parallel, where n is a natural number greater than zero. Each current subunit is configured to convert a difference between the voltage sampling signal and the corresponding threshold voltage into a current signal, and obtain the adjustment current Ig according to the current signal.

As a non-limiting example, the current generating unit 601 includes a current sub-unit 611 located on the fourth current path, and a current sub-unit 612 located on the fifth current path. The current subunit 611 is configured to obtain a fourth current I4 according to a difference between the voltage sampling signal V1 and the first threshold voltage Va, and the current subunit 612 is configured to obtain a fifth current I5 according to a difference between the voltage sampling signal V1 and the second threshold voltage Vb. The current subunit 611 is connected to the output node for outputting a fourth current I4 as the regulated current Ig.

The current sub-unit 611 includes a transistor N4, a resistor R52 and a transistor N5, and amplifiers U14 and U15, which are connected in series in the fourth current path.

The amplifier U14 has a non-inverting input terminal for receiving the voltage sampling signal V1, an inverting input terminal connected to the intermediate node of the transistor N4 and the resistor R52, and an amplifier U14 for driving the transistor N4 according to a voltage difference between the voltage sampling signal V1 and the intermediate node of the transistor N4 and the resistor R52. The amplifier U15 has a non-inverting input coupled to the intermediate node of the transistor N5 and the resistor R52, an inverting input for receiving the first threshold voltage Va, and an amplifier U15 for driving the transistor N5 according to a voltage difference between the first threshold voltage Va and the intermediate node of the transistor N5 and the resistor R52.

When the voltage sampling signal V1 is less than the first threshold voltage Va, the transistor N5 is turned off and the fourth current path is opened; when the voltage sampling signal V1 is greater than the first threshold voltage Va and less than the second threshold voltage Vb, the transistors N4 and N5 are turned on, the voltage at the intermediate node between the transistor N4 and the resistor R52 is equal to V1, the voltage at the intermediate node between the transistor N5 and the resistor R52 is equal to Va, and the fourth current I4 on the fourth current path is equal to (V1-Va)/R52, as can be seen from the above equation, the larger the difference between the voltage sampling signal V1 and the first threshold voltage Va is, the larger the fourth current I4 is. The control current Ig is I4. The output unit 602 includes transistors P3 and P4, transistors N8 and N9, and an output resistor R41. The transistor P3 and the transistor P4, and the transistor N8 and the transistor N9 form a current mirror structure for mirroring the adjustment current Ig to the output resistor R41 to obtain the control signal Vref 1-Vref-Ig × R41. From the above equation, the control signal Vref1 decreases as the fourth current I4 increases.

In a preferred embodiment, the current generating unit 601 further includes a transistor N3 and an amplifier U13, a non-inverting input terminal of the amplifier U13 is configured to receive the second threshold voltage Vb, an inverting input terminal is connected to the second pass terminal of the transistor N3, and an output terminal is connected to the control terminal of the transistor N3. The amplifier U13 is configured to control a maximum current value of the fourth current I4 on the fourth current path according to the second threshold voltage Vb, for example, the current I4max is (Vb-Va)/R52.

The current subunit 612 includes a transistor N1, a transistor N2, and a resistor R51 connected in series in the fifth current path, and an amplifier U11 and an amplifier U12. The amplifier U11 has a non-inverting input terminal for receiving the voltage sampling signal V1, an inverting input terminal connected to the intermediate node of the transistor N1 and the resistor R51, and an amplifier U11 for driving the transistor N1 according to a voltage difference between the voltage sampling signal V1 and the intermediate node of the transistor N1 and the resistor R51. The amplifier U12 has a non-inverting input terminal connected to the intermediate node of the transistor N2 and the resistor R51, an inverting input terminal for receiving the second threshold voltage Vb, and an amplifier U12 for driving the transistor N2 according to a voltage difference between the second threshold voltage Vb and the intermediate node of the transistor N2 and the resistor R51.

When the voltage sampling signal V1 is less than the second threshold voltage Vb, the transistor N2 is turned off and the fifth current path is opened. When the voltage sampling signal V1 is greater than the second threshold voltage Vb, the transistors N1 and N2 are turned on, the voltage at the intermediate node between the transistor N1 and the resistor R51 is equal to V1, the potential at the intermediate node between the transistor N2 and the resistor R51 is equal to Vb, and the fifth current I5 on the fifth current path is equal to (V1-Vb)/R51. As can be seen from the above equation, the larger the difference between the voltage sampling signal V1 and the second threshold voltage Vb, the larger the fifth current I5.

The current generating unit 601 further includes a current mirror 614, wherein the current mirror 614 includes a transistor P1 and a transistor P2, and is configured to mirror the fifth current I5 of the fifth current path onto the fourth current path to compensate for the fourth current I4, and then the fourth current I4 is I4 max-I5. As can be seen from the above equation, the larger the fifth current I5, the smaller the fourth current I4 will be, and in turn the larger the control signal Vref 1.

In some embodiments, the current generating unit 601 further includes a current sub-unit 613 located on the sixth current path for obtaining a sixth current I6 according to a difference between the voltage sampling signal V1 and the third threshold voltage Vc.

As shown in fig. 6, the current sub-unit 613 includes a transistor N6, a transistor N7, and a resistor R53, and an amplifier U16 and an amplifier U17 connected in series in the sixth current path. The amplifier U16 has a non-inverting input terminal for receiving the voltage sampling signal V1, an inverting input terminal connected to the intermediate node of the transistor N6 and the resistor R53, and an amplifier U16 for driving the transistor N6 according to a voltage difference between the voltage sampling signal V1 and the intermediate node of the transistor N6 and the resistor R53. The amplifier U17 has a non-inverting input terminal connected to the intermediate node of the transistor N7 and the resistor R53, an inverting input terminal for receiving the third threshold voltage Vc, and an amplifier U17 for driving the transistor N7 according to a voltage difference between the third threshold voltage Vb and the intermediate node of the transistor N7 and the resistor R53.

When the voltage sampling signal V1 is less than the third threshold voltage Vc, the transistor N7 is turned off and the sixth current path is opened. When the voltage sampling signal V1 is greater than the third threshold voltage Vc, the transistors N6 and N7 are turned on, the voltage at the intermediate node between the transistor N6 and the resistor R53 is equal to V1, the voltage at the intermediate node between the transistor N7 and the resistor R53 is equal to Vc, and the sixth current I6 on the sixth current path is equal to (V1-Vc)/R53. As can be seen from the above equation, the larger the difference between the voltage sampling signal V1 and the third threshold voltage Vc, the larger the sixth current I6. At this time, the larger the regulating current Ig is I6, the larger the sixth current I6 is, the larger the regulating current Ig is, and the smaller the control signal Vref1 is.

In this embodiment, the current generating unit 601 is implemented by a semiconductor field effect transistor, the threshold voltage can be adjusted without changing the circuit structure, the circuit stability is higher, and compared with a bipolar transistor, the threshold voltage is less affected by the process and has higher precision.

Fig. 7 shows a circuit structure diagram of a reference control module according to a second embodiment of the present invention, and as shown in fig. 7, the reference control module 720 includes a current generating unit 701 and an output unit 702. The current generating unit 701 is configured to generate a regulating current Ig according to the voltage sampling signal V1, an intermediate node between the output unit 702 and the current generating unit 701 is an output node, the output node is configured to provide the regulating current Ig, and the output unit 702 is configured to provide the control signal Io according to the regulating current Ig. The current generating unit 701 has the same structure and principle as the current generating unit 501 shown in fig. 5, and is not described herein again.

The output unit 702 includes a transistor P5 and a transistor P6, and the transistor P5 and the transistor P6 constitute a current mirror structure for mirroring the regulation current Ig to the control signal Io in the form of a current.

Fig. 8 shows another circuit configuration diagram of a reference control module according to a second embodiment of the present invention, and as shown in fig. 8, a reference control module 820 includes a current generating unit 801 and an output unit 802. The current generating unit 801 is configured to generate a regulating current Ig according to the voltage sampling signal V1, a middle connection point between the output unit 802 and the current generating unit 801 is an output node, the output node is configured to provide the regulating current Ig, and the output unit 802 is configured to provide the control signal Io according to the regulating current Ig. The current generating unit 801 has the same structure and principle as the current generating unit 601 shown in fig. 6, and is not described herein again.

The output unit 802 includes a transistor P7 and a transistor P8, and the transistor P7 and the transistor P8 constitute a current mirror structure for mirroring the regulation current Ig to the control signal Io in the form of a current.

In addition, in the above embodiments, the transistor Q1, the transistor Q2, and the transistor Q3 are NPN-type bipolar transistors, the transistors N1 to N9 are N-type oxide semiconductor field effect transistors, and the transistors P1 to P8 are P-type oxide semiconductor field effect transistors, respectively.

According to the utility model discloses another aspect provides a control method of LED drive circuit for control above-mentioned LED drive circuit. When the input voltage is in a first voltage interval, the driving current is controlled to be reduced along with the increase of the input voltage, when the input voltage is in a second voltage interval, the driving current is controlled to be increased along with the increase of the input voltage, the minimum value of the second voltage interval is equal to the maximum value of the first voltage interval, when the input voltage is in a third voltage interval, the driving current is controlled to be reduced along with the increase of the input voltage, and the minimum value of the third voltage interval is equal to/larger than the maximum value of the second voltage interval, so that the output power of the LED lamp is stabilized within a rated power range.

To sum up, the utility model discloses LED drive circuit and control method control drive current and reduce along with input voltage's increase in the first voltage interval after input voltage is located rated voltage interval, guarantee that input power is located the rated power within range all the time, improve circuit reliability and life to improve the utilization ratio of lamp pearl, reduce the complete machine cost, raise the efficiency.

And the utility model discloses LED drive circuit increases along with input voltage's increase in the second voltage interval after input voltage increases to first voltage interval to the work that the system can be stable when guaranteeing that input voltage increases to next rated voltage interval can make LED drive circuit be applicable to the input voltage of various voltage ranges, make being applicable to of the linear drive scheme of LED the electric wire netting that is wideer or more complicated, practice thrift the cost.

In accordance with the present invention, as set forth above, these embodiments do not set forth all of the details nor limit the invention to the specific 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 protection scope of the present invention should be subject to the scope defined by the claims of the present invention.

Claims

1. An LED driving circuit for driving an LED lamp according to an input voltage, the LED driving circuit comprising:

the control circuit is used for generating a control signal according to the input voltage; and

and the constant current circuit is connected with the LED lamp in series and used for regulating the driving current flowing through the LED lamp according to the control signal so as to stabilize the output power of the LED lamp within a rated power range.

2. The LED driving circuit according to claim 1, wherein the control signal is a voltage signal, and the constant current circuit includes:

the first power tube is used for controlling the driving current flowing through the LED lamp;

the first current sampling resistor is connected with the first power tube in series and used for providing a first current sampling signal; and

a first amplifier for adjusting the driving current according to the control signal and the first current sampling signal.

3. The LED driving circuit according to claim 1, wherein the control signal is a current signal, and the constant current circuit includes:

the second power tube is used for controlling the driving current flowing through the LED lamp;

the second current sampling resistor is connected with the second power tube in series and used for providing a second current sampling signal;

a second amplifier for comparing a reference voltage with a voltage feedback signal to adjust the drive current; and

a first feedback resistor connected between the inverting input terminal of the second amplifier and the source of the second power transistor,

the first feedback resistor is used for superposing the control signal and the second current sampling signal to obtain the voltage feedback signal.

4. The LED driving circuit according to claim 1, wherein the control circuit comprises:

the voltage detection module is used for sampling the input voltage to obtain a voltage sampling signal; and

and the reference control module is used for obtaining the control signal according to the voltage sampling signal.

5. The LED driving circuit according to claim 4, wherein the reference control module comprises:

the current generation unit is used for generating a regulating current according to the voltage sampling signal; and

and the output unit and the current generation unit are connected to an output node and used for providing the control signal according to the regulating current.

6. The LED driving circuit according to claim 5, wherein the current generating unit comprises n current sub-units, n being a natural number greater than zero,

each current subunit is configured to convert a voltage difference between the voltage sampling signal and a corresponding threshold voltage into a current signal, where the threshold voltage is used to represent a maximum value or a minimum value of a corresponding voltage interval.

7. The LED driving circuit according to claim 6, wherein the control signal controls the driving current to decrease with an increase of the voltage sampling signal when the voltage sampling signal is in a first voltage interval,

when the voltage sampling signal is in a second voltage interval, the control signal controls the driving current to increase along with the increase of the voltage sampling signal, and the minimum value of the second voltage interval is equal to the maximum value of the first voltage interval.

8. The LED driving circuit according to claim 7, further comprising: when the voltage sampling signal is located in a third voltage interval, the control signal controls the driving current to be reduced along with the increase of the voltage sampling signal, and the minimum value of the third voltage interval is equal to/larger than the maximum value of the second voltage interval.

9. The LED driving circuit according to claim 7, wherein the first voltage interval and the second voltage interval are located in a transition interval between a first rated voltage interval and a second rated voltage interval.

10. The LED driving circuit according to claim 8, wherein the current generating unit comprises:

a first current subunit located on the first current path, configured to obtain a first current according to a voltage difference between the voltage sampling signal and a first threshold voltage representing a minimum value of the first voltage interval,

the first current subunit is connected to the output node, and is configured to output the first current as the regulated current.

11. The LED driving circuit according to claim 10, wherein the current generating unit further comprises:

a second current subunit located on a second current path, connected to the first current subunit, for obtaining a second current according to a voltage difference between the voltage sampling signal and a second threshold voltage representing a minimum value of the second voltage interval,

wherein the second current subunit is configured to compensate the first current according to the second current.

12. The LED driving circuit according to claim 11, wherein the current generating unit further comprises:

a third current subunit located on the third current path, configured to obtain a third current according to a voltage difference between the voltage sampling signal and a third threshold voltage representing a minimum value of the third voltage interval,

wherein the third current subunit is connected to the output node, and is configured to output the third current as the adjustment current.

13. The LED driving circuit of claim 12, wherein the first current subunit, the second current subunit, and the third current subunit each comprise:

a first transistor and a second feedback resistor located on respective current paths; and

a voltage division module for comparing the voltage sampling signal with the threshold voltage to control the turning on and off of the first transistor.

14. The LED driving circuit according to claim 13, wherein the voltage dividing module comprises a plurality of voltage dividing resistors, and the threshold voltage is adjusted by adjusting resistance values of the plurality of voltage dividing resistors.

15. The LED driving circuit according to claim 13, wherein the first transistor is an NPN bipolar transistor.

16. The LED driving circuit according to claim 13, wherein the output unit includes:

and the first output resistor is connected between the reference voltage and the output node in series, and the first output resistor obtains the control signal in a voltage form according to the regulating current.

17. The LED driving circuit according to claim 13, wherein the output unit includes a second transistor and a third transistor,

wherein the second transistor and the third transistor constitute a first current mirror for converting the adjustment current into the control signal in the form of a current.

18. The LED driving circuit of claim 12, wherein the first current subunit, the second current subunit, and the third current subunit each comprise:

a fourth transistor, a third feedback resistor, and a fifth transistor located on respective current paths;

a third amplifier for driving the fourth transistor according to the voltage sampling signal and a potential of an intermediate node between the fourth transistor and the third feedback resistor; and

a fourth amplifier for driving the third transistor in accordance with the threshold voltage and a potential of an intermediate node of the fifth transistor and the third feedback resistor.

19. The LED driving circuit according to claim 18, wherein the current generating unit further comprises:

a sixth transistor connected in series on the first current path; and

a fifth amplifier having a positive input terminal for receiving the second threshold voltage, an inverted input terminal connected to the first terminal of the sixth transistor, and an output terminal connected to the control terminal of the sixth transistor,

the fifth amplifier is used for driving the sixth transistor according to the second threshold voltage so as to limit the current value of the first current.

20. The LED driving circuit according to claim 19, wherein the current generating unit further comprises a seventh transistor and an eighth transistor,

wherein the seventh transistor and the eighth transistor constitute a second current mirror to mirror the second current to the first current path to compensate for the first current.

21. The LED driving circuit according to claim 20, wherein the fourth transistor, the fifth transistor and the sixth transistor are N-type metal oxide semiconductor field effect transistors,

the seventh transistor and the eighth transistor are respectively P-type metal oxide semiconductor field effect transistors.

22. The LED driving circuit according to claim 18, wherein the output unit includes ninth to twelfth transistors and a second output resistor,

wherein the ninth transistor, the tenth transistor, the eleventh transistor and the twelfth transistor constitute a third current mirror, a power supply terminal of the third current mirror is connected to a power supply voltage, an input terminal is connected to the output node,

the second output resistor is connected in series between a reference voltage and an output terminal of the third current mirror,

the third current mirror is used for mirroring the adjusting current to the second output resistor, and the second output resistor obtains the control signal in a voltage form according to the adjusting current.

23. The LED driving circuit according to claim 22, wherein the ninth transistor and the tenth transistor are P-type metal oxide semiconductor field effect transistors, respectively,

the eleventh transistor and the twelfth transistor are N-type metal oxide semiconductor field effect transistors, respectively.

24. The LED driving circuit according to claim 18, wherein the output unit includes a thirteenth transistor and a fourteenth transistor,

wherein the thirteenth transistor and the fourteenth transistor constitute a fourth current mirror, a supply terminal of the fourth current mirror is connected to a supply voltage, and an input terminal is connected to the output node to convert the regulated current into the control signal in the form of a current.