阅读说明：本技术 线性led驱动电路、系统及其驱动方法 (Linear LED driving circuit, system and driving method thereof ) 是由 刘军 吴泉清 于 2019-03-01 设计创作，主要内容包括：本发明提供一种线性LED驱动电路、系统及其驱动方法,包括：连接于LED灯串负极与采样电阻之间的功率开关管；连接于LED灯串负极的工作电压产生模块,提供工作电压；连接LED灯串负极及工作电压的去纹波控制模块,产生去纹波控制信号；连接去纹波控制模块的基准电压产生模块,调整基准电压以实现去纹波控制；连接基准电压及采样电阻的运算放大器,控制功率开关管调整输出电流。当输入电压低于LED灯串的导通电压时,电解电容供电,减小LED灯串的输出电流的恒流值,进而消除工频纹波。本发明无论输入如何变化输出均可实现去纹波；去纹波功能不影响原有高功率因数应用的正常工作；无需增加外部元件,整个系统集成度高,外围电路简化。(The invention provides a linear LED driving circuit, a system and a driving method thereof, wherein the linear LED driving circuit comprises the following steps: the power switch tube is connected between the cathode of the LED lamp string and the sampling resistor; the working voltage generation module is connected with the cathode of the LED lamp string and provides working voltage; the ripple removing control module is connected with the cathode of the LED lamp string and the working voltage to generate a ripple removing control signal; the reference voltage generation module is connected with the ripple wave removal control module and is used for adjusting the reference voltage to realize ripple wave removal control; and the operational amplifier is connected with the reference voltage and the sampling resistor and controls the power switch tube to adjust the output current. When the input voltage is lower than the conduction voltage of the LED lamp string, the electrolytic capacitor supplies power, the constant current value of the output current of the LED lamp string is reduced, and then power frequency ripples are eliminated. The invention can realize the ripple wave removal no matter how the input changes the output; the normal work of the original high power factor application is not influenced by the ripple removing function; no need of external elements, high integration level of the whole system and simplified peripheral circuit.)

1. A linear LED driving circuit, characterized in that the linear LED driving circuit comprises at least:

the device comprises a power switch tube, a working voltage generating module, a ripple removing control module, a reference voltage generating module and an operational amplifier;

the power switch tube is connected between the negative electrode of the LED lamp string and the sampling resistor, and the output current of the LED lamp string is adjusted based on the power switch tube;

the working voltage generation module is connected to the negative electrode of the LED lamp string and provides working voltage for each module of the linear LED driving circuit based on the negative electrode voltage of the LED lamp string;

the ripple removing control module is connected to the negative electrode of the LED lamp string and the output end of the working voltage generating module, and generates a ripple removing control signal based on the negative electrode voltage of the LED lamp string and the working voltage;

the reference voltage generation module is connected with the output end of the ripple removal control module and adjusts reference voltage based on the ripple removal control signal so as to perform ripple removal control on the output current;

the input end of the operational amplifier is respectively connected with the output end of the reference voltage generation module and the sampling resistor, and the power switch tube is controlled to adjust the output current based on the reference voltage and the sampling voltage.

2. The linear LED driving circuit of claim 1, wherein: the linear LED driving circuit further comprises a timing module, the timing module is connected with the output end of the working voltage generation module, times that the cathode voltage of the LED lamp string is higher than the working voltage are conducted, and the ripple removal control module is controlled to work based on a timing result.

3. A linear LED driving system, characterized in that the linear LED driving system comprises at least:

a voltage input circuit, an electrolytic capacitor, an LED lamp string, a linear LED drive circuit according to any one of claims 1-2 and a sampling resistor;

the voltage input circuit provides an input voltage;

the electrolytic capacitor is connected in parallel with two ends of the voltage input circuit and is used for filtering output current ripples of the LED lamp string;

the anode of the LED lamp string is connected with the output end of the voltage input circuit, and the cathode of the LED lamp string is connected with the linear LED drive circuit;

one end of the sampling resistor is connected with the linear LED driving circuit, and the other end of the sampling resistor is grounded.

4. A driving method of the linear LED driving system according to claim 3, wherein the driving method of the linear LED driving system at least comprises:

when the input voltage is lower than the conduction voltage of the LED lamp string, the LED lamp string is powered on based on the electrolytic capacitor, the constant current value of the output current of the LED lamp string is reduced, the discharging time of the electrolytic capacitor is prolonged, and then power frequency ripples are eliminated.

5. The driving method of a linear LED driving system according to claim 4, wherein: setting the reference voltage to be zero when the voltage of the cathode of the LED lamp string is less than the working voltage of the linear LED driving circuit; when the voltage of the cathode of the LED lamp string is greater than the working voltage and less than a set voltage, gradually increasing the reference voltage from zero to a maximum value; and when the voltage of the cathode of the LED lamp string is greater than the set voltage, maintaining the reference voltage at the maximum value.

6. The driving method of a linear LED driving system according to claim 5, wherein: the reference voltage increases linearly from zero to a maximum value.

7. The method of any one of claims 4 to 6, wherein: and when the linear LED driving system is applied with a high power factor, the ripple removal control module is closed.

8. The driving method of a linear LED driving system according to claim 7, wherein: when the time that the cathode voltage of the LED lamp string is higher than the working voltage is less than the set time, judging that the linear LED driving system is applied with high power factor; and when the time that the cathode voltage of the LED lamp string is higher than the working voltage is longer than the set time, determining that the LED driving system does not carry out high power factor application.

9. The driving method of a linear LED driving system according to claim 8, wherein: the set time is not less than a power frequency period.

Technical Field

The invention relates to the field of integrated circuit design, in particular to a linear LED driving circuit, a linear LED driving system and a linear LED driving method.

Background

An LED is a semiconductor electronic component capable of emitting light, which can emit only low-intensity red light at an early stage, and with the continuous progress of technology, the light intensity has been improved to such an extent that visible light, infrared light and ultraviolet light are emitted. LEDs have the advantages of high efficiency, long life, low susceptibility to damage, high switching speed, high reliability, and the like, which are beyond the reach of conventional light sources, and have been widely used in indicator lights, displays, and lighting applications.

In general, in order to filter the ripple of the LED output current, an electrolytic capacitor is added to the linear LED driving circuit, as shown in fig. 1, a conventional ripple-removed linear LED driving circuit 1 includes: the alternating voltage Vin _ ac is converted into an input voltage Vin through the rectifier bridge 11, and supplies power to the LED lamp section, wherein the LED lamp section is formed by connecting n LED lamps in series; the output end of the LED lamp section is connected with a constant current control chip 12, constant current control is realized through a switch of a constant current control tube in the constant current control chip 12, an electrolytic capacitor Cin 'is connected in parallel with two ends of the rectifier bridge 11, and the electrolytic capacitor Cin' is an adjustable device.

As shown in fig. 2, when the voltage of the electrolytic capacitor Cin' is higher than the forward conducting voltage of the LED lamp segment (at the time t 0-t 1 and t 2-t 3 in a period), the constant current control chip 12 can control the LED lamp segment to realize constant current output. However, when the input voltage Vin is relatively low or the capacity of the electrolytic capacitor Cin ' is relatively small, the electrolytic capacitor Cin ' discharges through the LED lamp segment, and the electrolytic capacitor Cin ' discharges to a voltage lower than the forward conduction voltage of the LED lamp segment within a certain period of time (at time t 1-t 2 in a period), so that the current flowing through the LED lamp segment drops temporarily, and thus, a power frequency ripple occurs.

Therefore, the ripple removing effect is not ideal, and further removal of the power frequency ripple is required. When the capacity of the electrolytic capacitor is insufficient, the capacity can be increased, but there are problems in that the system cost, the volume increase, and the efficiency decrease. When the input voltage is low, the forward voltage of the LED segment can be reduced to improve the efficiency, but when the input voltage is high, the efficiency is reduced, and the luminous flux is reduced.

How to remove the ripple without affecting the cost, volume, efficiency, luminous flux, etc. has become one of the problems to be solved urgently by those skilled in the art.

Disclosure of Invention

In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a linear LED driving circuit, a system and a driving method thereof, which are used to solve the problems of high cost, large volume, low efficiency and low luminous flux of the ripple removing scheme in the prior art.

To achieve the above and other related objects, the present invention provides a linear LED driving circuit, comprising:

the device comprises a power switch tube, a working voltage generating module, a ripple removing control module, a reference voltage generating module and an operational amplifier;

the power switch tube is connected between the negative electrode of the LED lamp string and the sampling resistor, and the output current of the LED lamp string is adjusted based on the power switch tube;

the working voltage generation module is connected to the negative electrode of the LED lamp string and provides working voltage for each module of the linear LED driving circuit based on the negative electrode voltage of the LED lamp string;

the ripple removing control module is connected to the negative electrode of the LED lamp string and the output end of the working voltage generating module, and generates a ripple removing control signal based on the negative electrode voltage of the LED lamp string and the working voltage;

the reference voltage generation module is connected with the output end of the ripple removal control module and adjusts reference voltage based on the ripple removal control signal so as to perform ripple removal control on the output current;

the input end of the operational amplifier is respectively connected with the output end of the reference voltage generation module and the sampling resistor, and the power switch tube is controlled to adjust the output current based on the reference voltage and the sampling voltage.

Optionally, the linear LED driving circuit further includes a timing module, the timing module is connected to the output end of the working voltage generation module, and is configured to time the time that the cathode voltage of the LED light string is higher than the working voltage, and control the ripple removal control module to operate based on a timing result.

To achieve the above and other related objects, the present invention provides a linear LED driving system, comprising at least:

the LED lamp comprises a voltage input circuit, an electrolytic capacitor, an LED lamp string, the linear LED drive circuit and a sampling resistor;

the voltage input circuit provides an input voltage;

the electrolytic capacitor is connected in parallel with two ends of the voltage input circuit and is used for filtering output current ripples of the LED lamp string;

the anode of the LED lamp string is connected with the output end of the voltage input circuit, and the cathode of the LED lamp string is connected with the linear LED drive circuit;

one end of the sampling resistor is connected with the linear LED driving circuit, and the other end of the sampling resistor is grounded.

To achieve the above and other related objects, the present invention provides a driving method of the above linear LED driving system, the driving method of the linear LED driving system at least including:

when the input voltage is lower than the conduction voltage of the LED lamp string, the electrolytic capacitor supplies power to the LED lamp string, the constant current value of the output current of the LED lamp string is reduced, the discharge time of the electrolytic capacitor is prolonged, and then power frequency ripples are eliminated.

Optionally, the reference voltage is set to zero when the voltage of the cathode of the LED light string is less than the operating voltage of the linear LED driving circuit; when the voltage of the cathode of the LED lamp string is greater than the working voltage and less than a set voltage, gradually increasing the reference voltage from zero to a maximum value; and when the voltage of the cathode of the LED lamp string is greater than the set voltage, maintaining the reference voltage at the maximum value.

More optionally, the reference voltage increases linearly from zero to a maximum.

More optionally, when the linear LED driving system is applied with a high power factor, the ripple removal control module is turned off.

More optionally, when the time that the cathode voltage of the LED light string is higher than the working voltage is less than a set time, determining that the linear LED driving system performs high power factor application; and when the time that the cathode voltage of the LED lamp string is higher than the working voltage is longer than the set time, determining that the LED driving system does not carry out high power factor application.

More optionally, the set time is not less than one power frequency period.

As described above, the linear LED driving circuit, system and driving method thereof according to the present invention have the following advantages:

1. the linear LED driving circuit, the linear LED driving system and the driving method thereof realize the ripple removing application while realizing the linear LED driving, and can remove ripples no matter how the input changes the output.

2. The ripple removing function of the linear LED driving circuit, the system and the driving method thereof is not started under the application of high power factor, and the normal work of the original high power factor application is not influenced.

3. The linear LED driving circuit, the system and the driving method thereof do not need to increase external elements, the integration level of the whole system is high, and the peripheral circuit is simplified.

Drawings

Fig. 1 is a schematic diagram of a linear LED driving circuit in the prior art.

Fig. 2 is a schematic diagram illustrating the principle of power frequency ripple of a linear LED driving circuit in the prior art.

Fig. 3 is a schematic diagram of a linear LED driving circuit according to the present invention.

Fig. 4 is a schematic diagram of the ripple reduction control module according to the present invention.

Fig. 5 is a schematic diagram of another structure of the linear LED driving circuit according to the present invention.

Fig. 6 is a schematic structural diagram of a linear LED driving system according to the present invention.

Description of the element reference numerals

1 Linear LED drive circuit

11 rectifier bridge

12 constant current control chip

2 linear LED driving circuit

21 working voltage generating module

22 ripple-removing control module

23 reference voltage generating module

24 operational amplifier

25 timing module

3 voltage input circuit

Detailed Description

The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.

Please refer to fig. 3 to 6. It should be noted that the drawings provided in the present embodiment are only for illustrating the basic idea of the present invention, and the components related to the present invention are only shown in the drawings rather than drawn according to the number, shape and size of the components in actual implementation, and the type, quantity and proportion of the components in actual implementation may be changed freely, and the layout of the components may be more complicated.