CN113811043A

CN113811043A - LED lamp string driving circuit and method compatible with silicon controlled rectifier

Info

Publication number: CN113811043A
Application number: CN202111105720.0A
Authority: CN
Inventors: 麦炎全; 邓迅升; 陈博
Original assignee: Shenzhen Sendis Semiconductor Co Ltd
Current assignee: Shenzhen Sendis Semiconductor Co Ltd
Priority date: 2021-09-22
Filing date: 2021-09-22
Publication date: 2021-12-17
Anticipated expiration: 2041-09-22
Also published as: CN113811043B

Abstract

The invention discloses a LED lamp string driving circuit and method compatible with silicon controlled rectifier, the driving circuit includes: the rectifier module is connected with the LED lamp string and used for converting the input alternating current into power supply voltage and outputting the power supply voltage to the LED lamp string; the voltage sampling module is connected with the rectifying module and used for collecting the power supply voltage output by the rectifying module and obtaining a detection voltage; the detection module is connected with the voltage sampling module and used for comparing the detection voltage with a preset voltage, detecting whether the controlled silicon is connected according to a comparison result and outputting a judgment result; the reference voltage selection module is connected with the detection module and used for outputting reference voltage or reference current according to the judgment result; and the control current source module is respectively connected with the LED lamp string and the reference voltage selection module and is used for controlling the current of the LED lamp string according to the reference voltage or the reference current. The invention realizes the control of the consistent power of the LED lamp strings in the environment with or without the controllable silicon.

Description

LED lamp string driving circuit and method compatible with silicon controlled rectifier

Technical Field

The invention relates to the technical field of LED lighting, in particular to a LED lamp string driving circuit and method compatible with silicon controlled rectifier.

Background

In the LED lamp string driving, the effective value of the alternating voltage can be changed by cutting the alternating current phase through the silicon controlled rectifier, so that the dimming effect is achieved. However, for a general thyristor, even if the maximum output power is obtained by regulation, the effective voltage is about 10% smaller than that without the thyristor. Therefore, if the LED string current remains unchanged, the power with the thyristor is 10% less than that without the thyristor.

In many cases, in order to satisfy dimming effect and compatibility, the current of the LED lamp string varies with the controllable phase change, i.e. the effective voltage value is 90%, the effective current value is also adjusted to 90%, and the final output power is only 81%. That is, the maximum power of the LED string in the environment with the scr is about 20% less than that in the environment without the scr, which results in performance loss.

Accordingly, the prior art is yet to be improved and developed.

Disclosure of Invention

In view of the above-mentioned deficiencies of the prior art, an object of the present invention is to provide a LED string driving circuit and method compatible with thyristors, so as to solve the problem of performance loss caused by the fact that the maximum power of the LED string is about 20% lower than that of the LED string in the environment without thyristors in the environment with thyristors.

The technical scheme of the invention is as follows:

a LED lamp string driving circuit compatible with silicon controlled rectifier comprises:

the rectifier module is connected with the LED lamp string and used for converting input alternating current into power supply voltage and outputting the power supply voltage to the LED lamp string;

the voltage sampling module is connected with the rectifying module and used for collecting the power supply voltage output by the rectifying module and obtaining a detection voltage;

the detection module is connected with the voltage sampling module and used for comparing the detection voltage with a preset voltage, judging whether a silicon controlled rectifier is connected according to a comparison result and outputting a judgment result; if the detection voltage is smaller than the preset voltage, judging that the controlled silicon is accessed, otherwise, judging that no controlled silicon is accessed;

the reference voltage selection module is connected with the detection module and used for outputting reference voltage or reference current according to the judgment result; if the thyristor is detected to be connected, outputting a first reference voltage or a first reference current, and if no thyristor is detected to be input, outputting a second reference voltage or a second reference current; wherein the first reference voltage is greater than the second reference voltage, and the first reference current is greater than the second reference current;

and the control current source module is respectively connected with the LED lamp string and the reference voltage selection module and is used for controlling the current of the LED lamp string according to the reference voltage or the reference current.

In a further aspect of the present invention, the voltage sampling module comprises:

the sampling unit is connected with the rectifying module and is used for collecting the detection voltage;

and the filtering unit is connected with the sampling unit and used for filtering the detection voltage.

According to a further arrangement of the present invention, the sampling unit includes a first resistor and a second resistor; one end of the first resistor is connected with the rectifying module, the other end of the first resistor is connected with one end of the second resistor, and the other end of the second resistor is grounded;

the filtering unit includes: one end of the first capacitor is connected with the common connection end of the first resistor and the second resistor, and the other end of the first capacitor is grounded.

In a further aspect of the present invention, the detection module comprises: the non-inverting input end of the first analog comparator is connected with the voltage sampling module, the inverting input end of the first analog comparator is connected with a first preset voltage source used for providing a first preset voltage, and the output end of the first analog comparator is connected with the reference voltage selection module; if the detection voltage is larger than the first preset voltage, the first analog comparator outputs a high level, otherwise, the first analog comparator outputs a low level.

In a further aspect of the present invention, the detection module comprises: a second analog comparator, a third analog comparator, a timer and a comparator; the non-inverting input ends of the second analog comparator and the third analog comparator are connected with the voltage sampling module, the second analog comparator is connected with a second preset voltage source used for providing a second preset voltage, and the inverting input end of the third analog comparator is connected with a third preset voltage source used for providing a third preset voltage; the output end of the second analog comparator is connected with the first input end of the timer, the output end of the third analog comparator is connected with the second input end of the timer, the first output end of the timer is connected with the first input end of the comparator, the second input end of the timer is connected with the second input end of the comparator, and the output end of the comparator is connected with the reference voltage selection module.

In a further aspect of the present invention, the reference voltage selection module comprises: the MOS transistor comprises a first MOS transistor, a second MOS transistor and an inverter; the gate of the first MOS transistor is connected to the detection module 300, the drain of the first MOS transistor is connected to the control current source module, and the source of the first MOS transistor is connected to a first reference voltage source for providing a first reference voltage or a first reference current source for providing a first reference current; the grid electrode of the second MOS tube is connected with the output end of the inverter, the source electrode of the second MOS tube is connected with the control current source module, and the drain electrode of the second MOS tube is connected with a second reference voltage source for providing a second reference voltage or a second reference current source for providing a second reference current; the input end of the reverser is connected with the detection module; .

In a further aspect of the present invention, the reference voltage selection module comprises: the MOS transistor comprises a first MOS transistor, a second MOS transistor and an inverter; the grid electrode of the first MOS transistor is connected with the detection module 300, the drain electrode of the first MOS transistor is connected with the control current source module, and the source electrode of the first MOS transistor is connected with the voltage sampling module; the grid electrode of the second MOS tube is connected with the output end of the inverter, the source electrode of the second MOS tube is connected with the control current source module, and the drain electrode of the second MOS tube is connected with the second reference voltage source for providing second reference voltage; and the input end of the reverser is connected with the detection module.

In a further aspect of the present invention, the control current source module includes: the first operational amplifier, the third MOS tube and the third resistor;

the non-inverting input end of the first operational amplifier is connected with the reference voltage selection module, the inverting output end of the first operational amplifier is connected with one end of the third resistor, the output end of the first operational amplifier is connected with the grid electrode of the third MOS tube, the drain electrode of the third MOS tube is connected with the LED lamp string, the source electrode of the third MOS tube is connected with one end of the third resistor, and the other end of the third resistor is grounded.

In a further aspect of the present invention, the control current source module includes: a fourth MOS transistor and a fifth MOS transistor; the grid electrode of the fourth MOS tube is connected with the grid electrode of the fifth MOS tube, the drain electrode of the fourth MOS tube is connected with the reference voltage selection module, the drain electrode of the fifth MOS tube is connected with the LED lamp string, and the source electrode of the fifth MOS tube is grounded.

Based on the same inventive concept, the invention also provides a method for driving the LED lamp string compatible with the controllable silicon, which comprises the following steps:

collecting power supply voltage of the LED lamp string and obtaining detection voltage;

comparing the detection voltage with a preset voltage, judging whether a silicon controlled rectifier is connected according to a comparison result, and outputting a judgment result;

outputting a reference voltage or a reference current according to the judgment result;

and controlling the current of the LED lamp string according to the reference voltage or the reference current.

The invention provides a LED lamp string driving circuit and method compatible with silicon controlled rectifier, wherein the LED lamp string driving circuit compatible with silicon controlled rectifier comprises: the rectifier module is connected with the LED lamp string and used for converting input alternating current into power supply voltage and outputting the power supply voltage to the LED lamp string; the voltage sampling module is connected with the rectifying module and used for collecting the power supply voltage output by the rectifying module and obtaining a detection voltage; the detection module is connected with the voltage sampling module and used for comparing the detection voltage with a preset voltage, judging whether a silicon controlled rectifier is connected according to a comparison result and outputting a judgment result; if the detection voltage is smaller than the preset voltage, judging that the controlled silicon is accessed, otherwise, judging that no controlled silicon is accessed; the reference voltage selection module is connected with the detection module and used for outputting reference voltage or reference current according to the judgment result; if the thyristor is detected to be connected, outputting a first reference voltage or a first reference current, otherwise, outputting a second reference voltage or a second reference current; wherein the first reference voltage is greater than the second reference voltage, and the first reference current is greater than the second reference current; and the control current source module is respectively connected with the LED lamp string and the reference voltage selection module and is used for controlling the current of the LED lamp string according to the reference voltage or the reference current. The power supply voltage of the LED lamp string is collected to obtain the detection voltage, then the detection voltage is compared with the preset voltage, whether the silicon controlled rectifier is connected is judged according to the comparison result, the corresponding reference voltage or reference current is output to the control current source module according to the judgment result, the current source module can control the power of the LED lamp string to be consistent under the environment with or without the silicon controlled rectifier according to the output reference voltage or reference current, the loss of the performance of the LED lamp string is reduced, and the LED lamp string can play the best performance under the condition with or without the silicon controlled rectifier.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.

FIG. 1 is a functional block diagram of a thyristor-compatible LED string driving circuit according to the present invention.

FIG. 2 is a schematic diagram of a thyristor-compatible LED string driving circuit according to the present invention.

Fig. 3 is a circuit schematic diagram of a thyristor-compatible LED string driving circuit according to an embodiment of the present invention.

FIG. 4 is a schematic circuit diagram of a thyristor-compatible LED string driver circuit according to another embodiment of the present invention.

Fig. 5 is a circuit schematic diagram of a thyristor-compatible LED string driving circuit according to yet another embodiment of the present invention.

FIG. 6 is a flow chart of a method for driving a LED string light compatible with silicon controlled rectifier according to the present invention.

The various symbols in the drawings: 100. a rectification module; 200. a voltage sampling module; 300. a detection module; 400. a reference voltage selection module; 500. controlling the current source module; 600. an LED light string.

Detailed Description

The invention provides a LED lamp string driving circuit compatible with silicon controlled rectifier and a method thereof, and in order to make the purpose, technical scheme and effect of the invention clearer and clearer, the invention is further described in detail by referring to the attached drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

In the embodiments and claims, the articles "a", "an", "the" and "the" may include plural forms as well, unless the context specifically dictates otherwise. If there is a description of "first", "second", etc. in an embodiment of the present invention, the description of "first", "second", etc. is for descriptive purposes only and is not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature.

It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may also be present. Further, "connected" or "coupled" as used herein may include wirelessly connected or wirelessly coupled. As used herein, the term "and/or" includes all or any element and all combinations of one or more of the associated listed items.

It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

In addition, technical solutions between various embodiments may be combined with each other, but must be realized by a person skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination should not be considered to exist, and is not within the protection scope of the present invention.

Referring to fig. 1 to 5, the present invention provides a preferred embodiment of a thyristor-compatible LED string driving circuit.

As shown in fig. 1 and fig. 2, the present invention provides a driving circuit of a thyristor-compatible LED string 600, which includes: the circuit comprises a rectification module 100, a voltage sampling module 200, a detection module 300, a reference voltage selection module 400 and a control current source module 500. The rectifier module 100 is connected to the LED light string 600, and is configured to convert an input ac power into a supply voltage and output the supply voltage to the LED light string 600; the voltage sampling module 200 is connected to the rectifying module 100, and is configured to collect a power supply voltage output by the rectifying module 100 and obtain a detection voltage; the detection module 300 is connected to the voltage sampling module 200, and is configured to compare the detection voltage with a preset voltage, determine whether a thyristor is connected according to a comparison result, and output a determination result; the reference voltage selection module 400 is connected to the detection module 300, and configured to output a reference voltage or a reference current according to the determination result; the current source control module 500 is respectively connected to the LED light string 600 and the reference voltage selection module 400, and is configured to control the current of the LED light string 600 according to the reference voltage or the reference current.

Specifically, referring to fig. 2, the rectifier module 100 is a rectifier bridge, alternating current input by a power grid is rectified by the rectifier bridge and then outputs a direct current net voltage Vbus as a power supply voltage of the LED light string 600, the voltage sampling module 200 samples the power supply voltage output by the rectifier bridge to obtain a detection voltage Vsen1, the detection voltage is compared with a preset voltage by the detection module 300 and a judgment result is made as to whether a thyristor is connected, the judgment result is output to the reference voltage selection module 400, the reference voltage selection module 400 outputs a reference voltage or a reference current to the power control module according to the judgment result, and the power control module controls the current of the LED light string 600 according to the reference voltage or the reference current. If the detection module 300 detects that the thyristor is connected, that is, the detection voltage is less than the preset voltage, a first reference voltage Vref1 or a first reference current is output to the current source control module, and if the detection module 300 does not detect that the thyristor is connected, that is, the detection voltage is greater than the preset voltage, a second reference voltage Vref2 or a second reference current is output to the current source control module, wherein the first reference voltage Vref1 is greater than the second reference voltage Vref2, and the first reference current is greater than the second reference current.

Through the technical scheme, when no thyristor is detected to be connected, the second reference voltage Vref2 (or the second reference current) is output to the current source module, and when the thyristor is detected to be connected, the first reference voltage Vref1 (or the first reference current) which is larger than the second reference voltage Vref2 (or the second reference current) is output to the control current source module 500, that is, the output current of the LED lamp string 600 is increased, so that the product of the output voltage and the current of the LED lamp string 600 in the state of the maximum output of the thyristor is equal to the product of the output voltage and the current of the LED lamp string 600 in the state of no thyristor, that is, the output power of the LED lamp string 600 is consistent in the state of the connection of the thyristor or not, the loss of the LED lamp string 600 is reduced, and the LED lamp string 600 can play the best performance under the condition of the connection of the thyristor or not.

Referring to fig. 3, in a further implementation of an embodiment, the voltage sampling module 200 includes: the sampling unit is connected with the rectifying module 100 and used for collecting the detection voltage, and the filtering unit is connected with the sampling unit and used for filtering the detection voltage.

Specifically, the sampling unit comprises a first resistor R1 and a second resistor R2; one end of the first resistor R1 is connected to the rectifier module 100, the other end of the first resistor R1 is connected to one end of the second resistor R2, and the other end of the second resistor R2 is grounded. The filtering unit includes: one end of the first capacitor C1 is connected to a common terminal of the first resistor R1 and the second resistor R2, and the other end of the first capacitor C1 is grounded. The net voltage Vbus output by the rectifying module 100 is divided and sampled by the first resistor R1 and the second resistor R2, and filtered by the first capacitor C1 to output a detection voltage Vsen1 to the detection module 300.

Referring to fig. 3, in some embodiments, the detection module 300 includes: a first analog comparator CMP1, a non-inverting input terminal of the first analog comparator CMP1 being connected to the voltage sampling module 200, an inverting input terminal of the first analog comparator CMP1 being connected to a first preset voltage source for providing a first preset voltage, an output terminal of the first analog comparator CMP1 being connected to the reference voltage selection module 400; wherein the first analog comparator CMP1 outputs a high level if the sensing voltage Vsen1 is greater than the first preset voltage Vcmp1, and otherwise, the first analog comparator CMP1 outputs a low level.

Specifically, the first analog comparator CMP1 is disposed between the voltage sampling module 200 and the reference voltage selection module 400, wherein an inverting input terminal of the first analog comparator CMP1 is connected to a first preset voltage Vcmp1, the detection voltage Vsen1 output by the voltage sampling module 200 is compared with the first preset voltage Vcmp1, if the detection voltage Vsen1 is greater than the first preset voltage Vcmp1, it indicates that no thyristor is connected, the first analog comparator CMP1 outputs a high level, and if the detection voltage Vsen1 is less than the first preset voltage Vcmp1, it indicates that the thyristor is connected, the first analog comparator CMP1 outputs a low level.

After being filtered by the first capacitor C1, the detection voltage Vsen1 is an average rectified voltage, and when no thyristor is connected, an input sine wave is complete, the average voltage is high, and when a thyristor is connected, the input sine wave is absent, and the average voltage is low. Therefore, the first preset voltage Vcmp1 is a middle value of two average voltages when the thyristor is switched on and when the thyristor is not switched on, and therefore, the detection voltage Vsen1 is greater than the first preset voltage Vcmp1, which indicates that no thyristor is switched on, and if the detection voltage Vsen1 is less than the first preset voltage Vcmp1, which indicates that the thyristor is switched on.

Referring to fig. 3, in a further implementation of an embodiment, the reference voltage selection module 400 includes: a first MOS transistor P1, a second MOS transistor P2 and an inverter RE; the gate of the first MOS transistor P1 is connected to the detection module 300, the drain of the first MOS transistor is connected to the control current source module 500, and the source of the first MOS transistor P1 is connected to a first reference voltage source or a first reference current source; the gate of the second MOS transistor P2 is connected to the output terminal of the inverter RE, the source of the second MOS transistor P2 is connected to the control current source module 500, and the drain of the second MOS transistor P2 is connected to a second reference voltage source or a second reference current source; the input of the inverter RE is connected to the detection module 300.

Specifically, the first MOS transistor P1 and the second MOS transistor P2 are both P-type MOS transistors, and in some embodiments, the first MOS transistor P1 is connected to a first reference voltage source for providing a first reference voltage Vref1, and the second MOS transistor P2 is connected to a second reference voltage source for providing a second reference voltage source. When the first analog comparator CMP1 outputs a high level, i.e. the detection module 300 detects that no thyristor is connected, the first MOS transistor P1 is turned off, the inverter RE outputs low level, so that the second MOS transistor P2 is turned on, the reference voltage selection module 400 outputs a second reference voltage Vref2 to the control current source module 500, and when the first simulator CMP1 outputs a low level, that is, when the detection module 300 detects the thyristor access, the first MOS transistor P1 is turned on, the inverter RE outputs a high level, so that the second MOS transistor P2 is turned off, so that the reference voltage selection module 400 outputs the first reference voltage Vref1 to the control current source module 500, the output current of the LED lamp string 600 is increased, so that the product of the output voltage and the current of the LED lamp string 600 in the state of the maximum output of the controllable silicon is equal to the product of the output voltage and the current of the LED lamp string 600 in the state of no controllable silicon.

It should be noted that, in some embodiments, the first MOS transistor and the second MOS transistor may also be N-type MOS transistors, and only the gate connections of the first MOS transistor and the second MOS transistor need to be exchanged correspondingly, that is, only the first reference voltage can be output when the input of the thyristor is detected, and the second reference voltage can be output when no thyristor is detected, and the implementation principle of the method is consistent with the above embodiments, and therefore, the method is not described herein again.

In a further implementation of an embodiment, with reference to fig. 3, the control current source module 500 includes: the first operational amplifier OP, the third MOS transistor P3 and the third resistor R3; the non-inverting input end of the first operational amplifier OP is connected to the reference voltage selection module 400, the inverting output end of the first operational amplifier OP is connected to one end of the third resistor R3, the output end of the first operational amplifier OP is connected to the gate of the third MOS transistor P3, the drain of the third MOS transistor P3 is connected to the LED light string 600, the source of the third MOS transistor P3 is connected to one end of the third resistor R3, and the other end of the third resistor R3 is grounded.

Specifically, when the first operational amplifier OP receives the first reference voltage Vref1 or the second reference voltage Vref2 outputted by the reference voltage selection module 400, the third MOS transistor P3 is turned on to control the current of the LED string 600. When the reference voltage selection module 400 outputs the first reference voltage Vref1, the current of the LED string 600 is the ratio between the first reference voltage Vref1 and the third resistor R3, that is, Iled is Vref1/R3, and when the reference voltage selection module 400 outputs the 2 nd reference voltage, the current of the LED string 600 is controlled to be the ratio between the second reference voltage Vref2 and the third resistor R3, that is, Iled is Vref2/R3, so that the output currents of the LED string 600 are consistent when the thyristor is connected, and the purpose of consistent output power of the LED string 600 when the thyristor is connected is achieved.

Referring to fig. 4, in the above embodiment, the reference voltage selection module 400 may further include: a first MOS transistor P1, a second MOS transistor P2 and an inverter RE; the gate of the first MOS transistor P1 is connected to the detection module 300, the drain of the first MOS transistor P1 is connected to the control current source module 500, and the source of the first MOS transistor P1 is connected to the voltage sampling module 200; the gate of the second MOS transistor P2 is connected to the output terminal of the inverter RE, the source of the second MOS transistor P2 is connected to the control current source module 500, and the drain of the second MOS transistor P2 is connected to the second reference current source; the input of the inverter RE is connected to the detection module 300.

Specifically, in the above technical solution, the source of the first MOS transistor P1 is connected to the voltage sampling module 200, that is, the detection voltage Vsen1 is directly used as the reference voltage when the thyristor is connected, that is, the detection voltage Vsen1 is used to replace the first reference voltage Vref1, wherein the second reference voltage Vref2 is smaller than the maximum value of the detection voltage (the detection voltage when the thyristor is adjusted to the maximum output power), so that the current of the LED light string 600 can change with the change of the adjustment phase of the thyristor when the thyristor is detected to be connected, that is, the current of the LED light string 600 can be reduced when the thyristor is connected, the output voltage required by the control current source module 500 can also be reduced, thereby the problem of flicker when the output phase of the thyristor is relatively small can be suppressed, and the dimming effect can be improved.

As shown in fig. 5, the present invention further provides another embodiment of a thyristor-compatible LED string 600 driving circuit. In the scr-compatible LED string 600 driving circuit, the detection module 300 includes: a second analog comparator CMP2, a third analog comparator CMP3, a timer T, and a comparator U; the non-inverting input terminals of the second analog comparator CMP2 and the third analog comparator CMP3 are both connected to the voltage sampling module 200, the second analog comparator is connected to a second preset voltage source for providing a second preset voltage, and the inverting input terminal of the third analog comparator is connected to a third preset voltage source for providing a third preset voltage; the output terminal of the second analog comparator CMP2 is connected to the first input terminal of the timer T, the output terminal of the third analog comparator CMP3 is connected to the second input terminal of the timer T, the first output terminal of the timer T is connected to the first input terminal of the comparator U, the second input terminal of the timer T is connected to the second input terminal of the comparator U, and the output terminal of the comparator U is connected to the reference voltage selection module 400.

Specifically, in the above embodiment, the second analog comparator CMP2 is connected to a second preset voltage Vcmp2, and the third analog comparator CMP3 is connected to a third preset voltage Vcmp3, where the second preset voltage Vcmp2 is smaller than the third preset voltage Vcmp 3. The detection module 300 includes a first resistor R1 and a second resistor R2, and no capacitance is connected, so that the acquired detection voltage is rectified instantaneous voltage, that is, the rising and falling waveforms of a complete sine wave are symmetrical. The detection module 300 compares the detection voltage Vsen1 output by the voltage sampling module 200 with the second preset voltage Vcmp2 and the third preset voltage Vcmp3, and outputs a time T1 from a rising edge of an output value of the second analog comparator CMP2 to a rising edge of an output value of the third analog comparator CMP3 and a time T2 from a falling edge of an output value of the third analog comparator CMP3 to a falling edge of an output value of the second analog comparator Vcmp2 through the timer T and the comparator U, wherein when T1 is T2, the comparator U outputs a high level 1, which represents no thyristor access, otherwise, the sine wave is cut, which represents that a thyristor access exists, and the comparator U outputs a low level 0, and then the reference voltage selection module 400 selects one of the first reference current Iref1 or the second reference current Iref2 as an output current according to the input signal. When the output signal of the comparator U is high level 1, the first MOS transistor P1 is turned off, the inverter RE outputs low level, so that the second MOS transistor P2 is turned on, at this time, the reference voltage selection module 400 outputs the second reference current Iref2 to the control current source module 500, when the output signal of the comparator U is low level 0, that is, when the detection module 300 detects that the thyristor is connected, the first MOS transistor P1 is turned on, and the inverter RE outputs high level, so that the second MOS transistor P2 is turned off, so that the reference voltage selection module 400 outputs the first reference current Iref1 to the control current source module 500, wherein the first reference current Iref1 is greater than the second reference current Iref 2.

In the above embodiment, the control current source module 500 includes: a fourth MOS transistor P4 and a fifth MOS transistor P5; the gate of the fourth MOS transistor P4 is connected to the gate of the fifth MOS transistor P5, the drain of the fourth MOS transistor P4 is connected to the reference voltage selection module 400, the drain of the fifth MOS transistor P5 is connected to the LED light string 600, and the source of the fifth MOS transistor P5 is grounded.

Specifically, the fourth MOS transistor P4 and the fifth MOS transistor P5 are both NMOS transistors, and when the reference voltage selection module 400 outputs the first reference current Iref1 or the second reference current Iref2, the current source control module 500 controls the output current of the LED string 600 according to the input reference current, that is, when the reference voltage selection module 400 outputs the first reference current Iref1, the current Iled of the LED string 600 is controlled to be a · Iref1, and when the reference voltage selection module 400 outputs the second reference current Iref2, the current Iled of the LED string 600 is controlled to be a · Iref 2; and A is the ratio of the width to the length of the fourth MOS tube to the width to the length of the fifth MOS tube.

Referring to fig. 6, in some embodiments, the present invention further provides a method for driving a silicon controlled compatible LED string, which includes the steps of:

s100, collecting power supply voltage of the LED lamp string and obtaining detection voltage; specifically, as for an LED light string driving circuit compatible with silicon controlled rectifier, it is not described herein again.

S200, comparing the detection voltage with a preset voltage, judging whether a silicon controlled rectifier is connected according to a comparison result, and outputting a judgment result; if the detection voltage is smaller than the preset voltage, judging that the controlled silicon is accessed, otherwise, judging that no controlled silicon is accessed; specifically, as for an LED light string driving circuit compatible with silicon controlled rectifier, it is not described herein again.

S300, outputting a reference voltage or a reference current according to the judgment result; if the thyristor is detected to be connected, outputting a first reference voltage or a first reference current, otherwise, outputting a second reference voltage or a second reference current; wherein the first reference voltage is greater than the second reference voltage, and the first reference current is greater than the second reference current; specifically, as for an LED light string driving circuit compatible with silicon controlled rectifier, it is not described herein again.

And S400, controlling the current of the LED lamp string according to the reference voltage or the reference current. Specifically, as for an LED light string driving circuit compatible with silicon controlled rectifier, it is not described herein again.

In summary, the present invention provides a silicon controlled rectifier compatible LED light string driving circuit and method, wherein the silicon controlled rectifier compatible LED light string driving circuit includes: the rectifier module is connected with the LED lamp string and used for converting input alternating current into power supply voltage and outputting the power supply voltage to the LED lamp string; the voltage sampling module is connected with the rectifying module and used for collecting the power supply voltage output by the rectifying module and obtaining a detection voltage; the detection module is connected with the voltage sampling module and used for comparing the detection voltage with a preset voltage, judging whether a silicon controlled rectifier is connected according to a comparison result and outputting a judgment result; if the detection voltage is smaller than the preset voltage, judging that the controlled silicon is accessed, otherwise, judging that no controlled silicon is accessed; the reference voltage selection module is connected with the detection module and used for outputting reference voltage or reference current according to the judgment result; if the thyristor is detected to be connected, outputting a first reference voltage or a first reference current, otherwise, outputting a second reference voltage or a second reference current; wherein the first reference voltage is greater than the second reference voltage, and the first reference current is greater than the second reference current; and the control current source module is respectively connected with the LED lamp string and the reference voltage selection module and is used for controlling the current of the LED lamp string according to the reference voltage or the reference current. The power supply voltage of the LED lamp string is collected to obtain the detection voltage, then the detection voltage is compared with the preset voltage, whether the silicon controlled rectifier is connected is judged according to the comparison result, the corresponding reference voltage or reference current is output to the control current source module according to the judgment result, the current source module can control the power of the LED lamp string to be consistent under the environment with or without the silicon controlled rectifier according to the output reference voltage or reference current, the loss of the performance of the LED lamp string is reduced, and the LED lamp string can play the best performance under the condition with or without the silicon controlled rectifier.

It is to be understood that the invention is not limited to the examples described above, but that modifications and variations may be effected thereto by those of ordinary skill in the art in light of the foregoing description, and that all such modifications and variations are intended to be within the scope of the invention as defined by the appended claims.

Claims

1. An LED lamp string driving circuit compatible with silicon controlled rectifier is characterized by comprising:

the reference voltage selection module is connected with the detection module and used for outputting reference voltage or reference current according to the judgment result, if the thyristor is detected to be connected, first reference voltage or first reference current is output, and if the thyristor is not connected, second reference voltage or second reference current is output; wherein the first reference voltage is greater than the second reference voltage, and the first reference current is greater than the second reference current;

2. The silicon controlled compatible LED light string driving circuit according to claim 1, wherein the voltage sampling module comprises:

3. The LED lamp string driving circuit compatible with silicon controlled rectifier according to claim 2, wherein the sampling unit comprises a first resistor and a second resistor; one end of the first resistor is connected with the rectifying module, the other end of the first resistor is connected with one end of the second resistor, and the other end of the second resistor is grounded;

4. The silicon controlled compatible LED light string driving circuit according to claim 1, wherein the detection module comprises: the non-inverting input end of the first analog comparator is connected with the voltage sampling module, the inverting input end of the first analog comparator is connected with a first preset voltage source used for providing a first preset voltage, and the output end of the first analog comparator is connected with the reference voltage selection module; if the detection voltage is greater than the first preset voltage, the first analog comparator outputs a high level, otherwise, the first analog comparator outputs a low level.

5. The silicon controlled compatible LED light string driving circuit according to claim 1, wherein the detection module comprises: a second analog comparator, a third analog comparator, a timer and a comparator; the non-inverting input ends of the second analog comparator and the third analog comparator are connected with the voltage sampling module, the inverting input end of the second analog comparator is connected with a second preset voltage source used for providing a second preset voltage, and the inverting input end of the third analog comparator is connected with a third preset voltage source used for providing a third preset voltage; the output of second analog comparator with the first input of time-recorder is connected, the output of third analog comparator with the second input of time-recorder is connected, the first output of time-recorder with the first input of comparator is connected, the second input of time-recorder with the second input of comparator is connected, the output of comparator with reference voltage selects the module to connect.

6. The SCR-compatible LED string drive circuit of claim 4, wherein the reference voltage selection module comprises: the MOS transistor comprises a first MOS transistor, a second MOS transistor and an inverter; the grid electrode of the first MOS tube is connected with the detection module, the drain electrode of the first MOS tube is connected with the control current source module, and the source electrode of the first MOS tube is connected with a first reference voltage source for providing a first reference voltage or a first reference current source for providing a first reference current; the grid electrode of the second MOS tube is connected with the output end of the inverter, the source electrode of the second MOS tube is connected with the control current source module, and the drain electrode of the second MOS tube is connected with a second reference voltage source for providing a second reference voltage or a second reference current source for providing a second reference current; and the input end of the reverser is connected with the detection module.

7. The SCR-compatible LED string drive circuit of claim 4, wherein the reference voltage selection module comprises: the MOS transistor comprises a first MOS transistor, a second MOS transistor and an inverter; the grid electrode of the first MOS tube is connected with the detection module, the drain electrode of the first MOS tube is connected with the control current source module, and the source electrode of the first MOS tube is connected with the voltage sampling module; the grid electrode of the second MOS tube is connected with the output end of the inverter, the source electrode of the second MOS tube is connected with the control current source module, and the drain electrode of the second MOS tube is connected with a second reference voltage source for providing a second reference voltage; the input end of the reverser is connected with the detection module; wherein the second reference voltage is less than a maximum value of the detection voltage.

8. The SCR-compatible LED string drive circuit according to claim 6 or 7, wherein the control current source module comprises: the first operational amplifier, the third MOS tube and the third resistor;

9. The SCR-compatible LED string drive circuit of claim 5 or 6, wherein the control current source module comprises: a fourth MOS transistor and a fifth MOS transistor; the grid electrode of the fourth MOS tube is connected with the grid electrode of the fifth MOS tube, the drain electrode of the fourth MOS tube is connected with the reference voltage selection module, the drain electrode of the fifth MOS tube is connected with the LED lamp string, and the source electrode of the fifth MOS tube is grounded.

10. An LED string driving method of the scr-compatible LED string driving circuit according to any one of claims 1 to 9, comprising: