CN110149747B - Driving circuit for directly supplying power to LED lamp tube by power adapter and design method - Google Patents
Driving circuit for directly supplying power to LED lamp tube by power adapter and design method Download PDFInfo
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Abstract
The invention relates to a driving circuit for directly supplying power to an LED lamp tube by adopting a power adapter, wherein the power adapter is respectively and electrically connected with: the LED lamp tube is electrically connected with the drain terminal of an N-channel MOS tube Q1, the source terminal of an N-channel MOS tube Q1 is grounded through a current sampling resistor R1, the gate terminal of the N-channel MOS tube Q1 is electrically connected with the output terminal of an operational amplifier OP through a resistor R2, two ends of a parasitic capacitor Cgd in the N-channel MOS tube Q1 are respectively electrically connected with one end of a current sampling resistor R1 and one end of a resistor R2, the grounding terminal of the operational amplifier OP is grounded, the power supply terminal of the operational amplifier OP is electrically connected with the output terminal of a power adapter through a Vcc power supply control circuit, the Vcc power supply control circuit receives an On/off switching signal of a mainboard, the negative input terminal of the operational amplifier OP is electrically connected with one end of the current sampling resistor R1, the positive input terminal of the operational amplifier OP is electrically connected with one end of a resistor R3 and one end of the resistor R4, the other end of the resistor R3 is grounded, the other end of the resistor R4 is electrically connected with a reference voltage Vref, and the positive input terminal of the operational amplifier OP receives a PWM dimming signal of the mainboard.
Description
Technical Field
The invention relates to the technical field of liquid crystal display equipment, in particular to a driving circuit for directly supplying power to an LED lamp tube by adopting a power adapter and a design method of the LED lamp tube.
Background
At present, in a liquid crystal display product powered by an external power adapter, an internal LED lamp driving circuit generally adopts a traditional Boost LED lamp driving circuit shown in fig. 1, and the output of the power adapter is as follows: after the 19V direct current voltage is boosted by the Boost LED lamp tube driving circuit, the boosted voltage is provided for the LED lamp tube to work, and 1, if the traditional Boost LED lamp tube driving circuit adopts PWM dimming and the dimming frequency is too high, such as the dimming frequency is more than 20KHZ, the following problems can be caused: firstly, when the liquid crystal display picture is high in brightness, the PWM dimming Duty ratio (Duty) is larger, the whole Boost LED lamp tube driving circuit system is easy to generate an unstable problem because the PWM working frequency is too high, secondly, when the liquid crystal display picture is low in brightness, the PWM dimming Duty ratio (Duty) is smaller, when the working period of the Boost MOS transistor Q1 in each PWM dimming period of the Boost LED lamp driving circuit is shorter than the delay time (delay time) of the internal protection circuit of the LED lamp driving control chip, the abnormal short circuit or open circuit may occur in the LED lamp, the LED lamp tube driving control chip can not perform normal protection action, so the PWM dimming frequency of the traditional Boost LED lamp tube driving circuit adopting PWM dimming is usually set to be about 180HZ-300HZ, however, the conventional Boost LED lamp driving method using low-frequency PWM dimming has the following disadvantages: firstly, the Boost inductor L1 is easy to generate abnormal sound (the audio frequency range received by human ears is 20HZ-20 KHZ), and secondly, the low-frequency PWM dimming is easy to generate the picture ripple interference or the picture flash problem.
2. In a traditional Boost LED lamp tube driving circuit, high-frequency di/dt and dv/dt of a Q1 MOS tube, an L1 Boost inductor and a D1 Boost diode are easy to generate high-frequency EMI electromagnetic radiation when working, so that when part of new liquid crystal display models test EMI, the EMI radiation margin is insufficient or exceeds the regulation standard, a large amount of manpower and time are needed to solve the problem, the problem that the product design cost is increased, a small part of products cannot be put into the market for sale in time and the like is possibly caused finally
Disclosure of Invention
The invention aims to provide a driving circuit for a power adapter to directly supply power to an LED lamp tube and an LED lamp tube design method, wherein the driving circuit is reasonable in design, simple in structure, low in price, free from water ripple interference, picture flashing or abnormal sound and lower in EMI electromagnetic radiation.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention provides a driving circuit for directly supplying power to an LED lamp tube by using a power adapter, which comprises the power adapter, the LED lamp tube, an N-channel MOS tube Q1 and a mainboard, wherein the input end of the power adapter is electrically connected as follows: the 220V commercial alternating current outputs direct current after voltage conversion, the LED lamp also comprises a Vcc power supply control circuit, an operational amplifier OP, a current sampling resistor R1 and reference voltage Vref, the input end of the LED lamp is electrically connected with the output end of a power adapter, the output end of the LED lamp is electrically connected with the drain end of an N-channel MOS tube Q1, the source end of the N-channel MOS tube Q1 is electrically connected with one end of a current sampling resistor R1, the other end of the current sampling resistor R1 is grounded, the grid end of the N-channel MOS tube Q1 is electrically connected with one end of a resistor R2, the two ends of a parasitic capacitor Cgd in the N-channel MOS tube Q1 are respectively electrically connected with one end of a current sampling resistor R1 and one end of a resistor R2, the other end of the resistor R2 is electrically connected with the output end of the operational amplifier OP, the grounding end of the operational amplifier OP is electrically connected with the output end of the Vcc power supply control circuit, one input end of the Vcc power supply control circuit is electrically connected with the output end of the power adapter, the other input end of the Vcc power supply control circuit receives an On/off switch signal output by a GPIO port of an image processor in the mainboard, the negative input end of the operational amplifier OP is electrically connected with the source end of an N-channel MOS tube Q1 and one end of a current sampling resistor R1, the positive input end of the operational amplifier OP is electrically connected with one end of a resistor R3 and one end of a resistor R4, the other end of the resistor R3 is grounded, the other end of the resistor R4 is electrically connected with a reference voltage Vref, and the positive input end of the operational amplifier OP receives a PWM dimming signal output by the other GPIO port of the image processor in the mainboard to adjust and control the average current of the LED lamp tube.
Preferably, the Vcc power supply control circuit includes a zener diode Z1, a resistor R5, a transistor Q2 and a transistor Q3, wherein a power supply terminal of the operational amplifier OP is electrically connected to a collector of the transistor Q3 through the zener diode Z1 and a resistor R7 in sequence, an emitter of the transistor Q3 is electrically connected to an output terminal of the power adapter, a base of the transistor Q3 is electrically connected to one end of a resistor R6, two ends of the resistor R5 are electrically connected to the output terminal of the power adapter and one end of a resistor R6, the other end of the resistor R6 is electrically connected to a collector of the transistor Q2, an emitter of the transistor Q2 is grounded, and a base of the transistor Q2 receives an On/off switching signal through a resistor R8.
Preferably, the reference voltage Vref is a DC voltage output by a DC-DC circuit in the main board.
Preferably, the input end of the power adapter is electrically connected as follows: 220V commercial alternating current is output after voltage conversion is carried out, such as: 19V direct current.
Preferably, the frequency of the PWM dimming signal may be greater than 20 KHZ.
The invention relates to a design method of an LED lamp tube for directly supplying power to the LED lamp tube by using a power adapter, wherein each LED lamp tube is formed by connecting P1 light-emitting diodes in a design mode of first series connection and then parallel connection, each LED lamp tube comprises M1 LED lamp strings arranged in parallel, each LED lamp string is formed by sequentially connecting N1 light-emitting diodes in series, N1 is 4, 5, 6 or 7, P1= N1M 1, and the forward conducting voltage of the P1 light-emitting diodes of each LED lamp tube is VF.
Preferably, the voltage VF is divided into a gear A with a voltage range of 2.9V-3.0V, a gear B with a voltage range of 3.0V-3.1V and a gear C with a voltage range of 3.1V-3.2V; when N1 is 5 or 7 odd number, N1 LEDs of each LED string are all connected in series by A gear or B gear in sequence, when N1 is 4 or 6 even number, N1 LEDs of each LED string are all connected in series by A gear or B gear, or N1/2 LEDs of each LED string are connected in series by A gear and the rest N1/2 LEDs are mixed and connected in series by C gear in sequence
The invention relates to a design method of an LED lamp tube for directly supplying power to the LED lamp tube by using a power adapter, wherein each LED lamp tube is formed by connecting P2 light-emitting diodes in a design mode of parallel connection and serial connection, each LED lamp tube comprises N2 parallel-connected groups which are arranged in series, each parallel-connected group of the LEDs is formed by connecting M2 light-emitting diodes in parallel, N2 is 4, 5, 6 or 7, P2= N2M 2, and the forward conducting voltage of the P2 light-emitting diodes of each LED lamp tube is VF.
Preferably, the voltage VF is divided into a gear A with a voltage range of 2.9V-3.0V, a gear B with a voltage range of 3.0V-3.1V and a gear C with a voltage range of 3.1V-3.2V; m2 LEDs of each LED parallel group are all connected with an A gear, a B gear or a C gear, when N2 is 5 or 7 odd numbers, N2 parallel groups are designed in a serial connection mode that each parallel group is the A gear or the B gear in sequence, when N2 is 4 or 6 even numbers, N2 parallel groups are designed in a serial connection mode that each parallel group is the A gear or the B gear or N2/2A gear parallel groups and N2/2C gear parallel groups are mixed and overlapped in sequence.
The invention adopts the technical proposal that the power adapter outputs as follows: the 19V direct current directly supplies power to the LED lamp tube, the OP operational amplifier controls the current of the LED lamp tube, and the problems that the traditional power adapter scheme is adopted to output the current as follows are overcome: the 19V voltage is boosted by the Boost LED lamp tube driving circuit and then is supplied to the LED lamp tube for working, and the novel LED lamp tube driving circuit has the characteristics of low cost and few parts; the LED lamp tube voltage is controlled at a low voltage such as: within 19V, an N-channel MOS tube Q1 connected with the output end of the LED lamp tube can adopt a large-sealed MOS tube with low voltage and large current (such as an N-channel MOS tube packaged by 30V/24A TO-252), the DIM PWM dimming frequency can be set above 20KHZ, the problem of interference such as water ripple and the like or picture flash of a liquid crystal display picture can not be generated, meanwhile, the novel LED lamp tube is driven by directly adopting a power adapter TO output direct current TO directly supply power TO the LED lamp tube, and the problems that high-frequency EMI electromagnetic radiation is easily generated by the Q1 MOS tube, the L1 Boost inductor and a D1 Boost diode in the traditional Boost LED lamp tube driving circuit when working and high-frequency di/dt and dv/dt easily generate high-frequency EMI electromagnetic radiation and abnormal sound is easily generated by the traditional Boost inductor when the traditional Boost inductor works in low-frequency PWM dimming are solved.
The invention has the following beneficial effects:
1. the power adapter will be as follows: direct current (such as 19V direct current) output after voltage conversion is carried out on alternating current in 220V city can be directly supplied to an LED lamp tube for working, and the defects that the traditional LED lamp tube driving adopts a power adapter such as: the LED lamp tube driving circuit has the characteristics of simple structure, less parts and low material cost of electronic parts;
2. the LED lamp tube driving circuit can receive a PWM dimming signal with the frequency of more than 20KHZ to perform PWM dimming, and adopts the PWM dimming signal with the frequency of more than 20KHZ to perform dimming, so that the problems of water ripple interference, picture flash and abnormal sound generated by the conventional Boost circuit adopting 180HZ-300HZ low-frequency PWM dimming are solved;
3. the LED lamp tube driving circuit adopts an on/off signal to control the Vcc power supply control circuit to directly cut off the power supply voltage of the operational amplifier OP in a standby state, so that the LED lamp tube driving circuit basically does not consume electric energy in the standby state.
4. The LED lamp tube driving device directly adopts the power adapter to output direct current to directly supply power to the LED lamp tube, and overcomes the problem that high-frequency di/dt and dv/dt are easy to generate high-frequency EMI electromagnetic radiation when a Q1 MOS tube, an L1 Boost inductor and a D1 Boost diode in the traditional Boost LED lamp tube driving circuit work.
Drawings
The invention will now be further elucidated with reference to the accompanying drawings:
fig. 1 is a schematic diagram of a conventional Boost LED lamp driving circuit;
FIG. 2 is a schematic diagram of a driving circuit for directly supplying power to an LED lamp tube by a power adapter according to the present invention;
FIG. 3 is a timing diagram of waveforms for a driving circuit of the present invention using a power adapter to directly supply power to an LED lamp;
FIG. 4 is a schematic diagram of a Vcc power supply control circuit of the present invention;
FIG. 5 is a schematic diagram of a design method of an LED lamp tube for directly supplying power to the LED lamp tube by using a power adapter according to the present invention;
FIG. 6 is a schematic diagram of another LED lamp design method for directly supplying power to an LED lamp by using a power adapter according to the present invention.
Detailed Description
As shown in one of fig. 1 to 6, the driving circuit of the present invention directly supplies power to an LED lamp by a power Adapter, which includes a power Adapter (Adapter), an LED lamp, an N-channel MOS transistor Q1, a motherboard (not shown in the drawings), a Vcc power supply control circuit, an operational amplifier OP, and a current sampling resistor R1, wherein an input terminal of the power Adapter is electrically connected to: the 220V commercial alternating current is used for outputting direct current (such as 19V direct current) after voltage conversion and directly used as the input voltage of the LED lamp tube, the input end of the LED lamp tube is electrically connected with the output end of the power Adapter, the output end of the LED lamp tube is electrically connected with the drain end of an N-channel MOS tube Q1, the source end of the N-channel MOS tube Q1 is electrically connected with one end of a current sampling resistor R1, the other end of the current sampling resistor R1 is grounded, the grid end of the N-channel MOS tube Q1 is electrically connected with one end of a resistor R2, two ends of a parasitic capacitor Cgd in the N-channel MOS tube Q1 are respectively electrically connected with one end of the current sampling resistor R1 and one end of the resistor R2, the other end of the resistor R2 is electrically connected with the output end of the operational amplifier OP, the grounding end of the operational amplifier OP is electrically connected with the output end of the Vcc power supply control circuit, one input end of the power supply control circuit is electrically connected with the output end of the power Adapter, the other input end of the Vcc power supply control circuit receives an On/off switch signal output by a GPIO port of an image processor (Scaler) in the mainboard, the negative input end of the operational amplifier OP is electrically connected with the source end of an N-channel MOS tube Q1 and one end of a current sampling resistor R1, the positive input end of the operational amplifier OP is electrically connected with one end of a resistor R3 and one end of a resistor R4, the other end of the resistor R3 is grounded, the other end of the resistor R4 receives a direct current voltage (such as a 3.3V direct current voltage) output by a DC-DC circuit in the mainboard as a reference voltage Vref, and the positive input end of the operational amplifier OP receives a dimming signal with a frequency greater than 20KHZ output by the other GPIO port of the image processor (Scaler) in the mainboard for adjusting and controlling the average current of the LED lamp tube, thereby controlling the brightness and darkness of the whole liquid crystal display screen.
As shown in fig. 4, the Vcc power supply control circuit includes a zener diode Z1, a resistor R5, a transistor Q2, and a transistor Q3, wherein a power supply terminal of the operational amplifier OP is electrically connected to a collector of the transistor Q3 through the zener diode Z1 and a resistor R7 in sequence, an emitter of the transistor Q3 is electrically connected to an output terminal of the power Adapter, a base of the transistor Q3 is electrically connected to one end of the resistor R6, two ends of the resistor R5 are electrically connected to an output terminal of the power Adapter and one end of the resistor R6, the other end of the resistor R6 is electrically connected to a collector of the transistor Q2, an emitter of the transistor Q2 is grounded, and a base of the transistor Q2 receives an On/off switching signal through a resistor R8.
By adopting the technical scheme, when the liquid crystal display product normally works, the On/off signal is at a high level, the Vcc power supply control circuit provides Vcc voltage to the operational amplifier OP to work, when the liquid crystal display product enters a standby state, the On/off signal is at a low level, and the Vcc power supply control circuit stops providing power supply voltage to the operational amplifier OP, so that the LED lamp tube driving circuit is more energy-saving in the standby state.
The LED lamp tube current control principle of the invention is as follows: the drive circuit of the invention utilizes parasitic capacitance Cgd and resistance R2 in N-channel MOS tube Q1 to make up a negative feedback circuit to the operational amplifier OP, according to the virtual short characteristic of the operational amplifier OP negative feedback circuit: v + = V- = Vsen = Ilamp R1, i.e.: the LED lamp current Ilamp = V +/R1, that is, the magnitude of the positive input terminal voltage V + of the operational amplifier OP determines the magnitude of the LED lamp current. Referring to fig. 3, at time T1, an image processor (Scaler) in the motherboard sends an On/off signal to a GPIO port to be a Low level Low signal, the Vcc power supply control circuit stops providing Vcc power supply voltage to the OP-amp, and the LED lamp does not operate; at time T2, an image processor (Scaler) in the motherboard sends an On/off signal as a High level High signal through a GPIO port, and simultaneously another GPIO port of the image processor (Scaler) in the motherboard sends a PWM DIM dimming signal with a frequency above 20KHZ as an idle signal, where the positive input terminal voltage of the operational amplifier OP is V + = Vref × R3/(R4+ R3), and if Vref =3.3V, R4=10K, and R3=1K, V + =0.3V, the LED tube current Ilamp = V +/R1, and if R1=1 Ω, Ilamp =300 mA; at time T3, an image processor (Scaler) in the motherboard sends an On/off signal as a High level High signal through a GPIO port, and simultaneously another GPIO port of the image processor (Scaler) in the motherboard sends a PWM DIM dimming signal with a frequency above 20KHZ as a low level signal (0V), at this time, the positive input terminal V + =0V of the operational amplifier OP, the LED tube current Ilamp = V +/R1=0V, and the LED tube current is 0 mA. When the DIM dimming signal output PWM Duty ratio Duty = null signal/PWM period = T2/(T2+ T3), the LED tube average current magnitude Iavg = Ilamp Duty = Ilamp T2/(T2+ T3), and if DIM dimming frequency f =25KHZ, T2= T3=20uS, the LED tube average current magnitude Iavg =300mA 0.5=150 mA. The larger the PWM Duty sent by the DIM dimming signal is, the larger the average current of the LED lamp tube is, and the brighter the liquid crystal display picture is, on the contrary, the smaller the PWM Duty sent by the DIM dimming signal is, the smaller the average current of the LED lamp tube is, and the darker the liquid crystal display picture is, namely, the size of the DIM dimming signal determines the brightness and the darkness of the liquid crystal display picture. The voltage of the LED lamp tube is controlled to be low as follows: within 19V, an N-channel MOS tube Q1 connected with the output end of the LED lamp tube can adopt a large-sealed MOS tube with low voltage and large current (such as an N-channel MOS tube packaged by 30V/24A TO-252), the DIM PWM dimming frequency can be set above 20KHZ, the problem of interference such as water ripple and the like or picture flash of a liquid crystal display picture can not be generated, meanwhile, the novel LED lamp tube is driven by directly adopting a power adapter TO output direct current TO directly supply power TO the LED lamp tube, and the problems that high-frequency EMI electromagnetic radiation is easily generated by the Q1 MOS tube, the L1 Boost inductor and a D1 Boost diode in the traditional Boost LED lamp tube driving circuit when working and high-frequency di/dt and dv/dt easily generate high-frequency EMI electromagnetic radiation and abnormal sound is easily generated by the traditional Boost inductor when the traditional Boost inductor works in low-frequency PWM dimming are solved.
As shown in fig. 5, in the LED lamp design method of the present invention, a power adapter is used to directly supply power to LED lamps, each LED lamp is formed by connecting P1 light emitting diodes in a serial-to-parallel design manner, each LED lamp includes M1 LED strings arranged in parallel, each LED string is formed by connecting N1 light emitting diodes in series in sequence, wherein N1 is 4, 5, 6, or 7, P1= N1 × M1, and the forward conduction voltage of P1 light emitting diodes of each LED lamp is VF. Preferably, the voltage VF is divided into a gear A with a voltage range of 2.9V-3.0V, a gear B with a voltage range of 3.0V-3.1V and a gear C with a voltage range of 3.1V-3.2V; when N1 is 5 or 7 odd number, N1 LEDs of each LED string are all connected in series by A gear or B gear in sequence, when N1 is 4 or 6 even number, N1 LEDs of each LED string are all connected in series by A gear or B gear, or N1/2 LEDs of each LED string are connected in series by A gear and the rest N1/2 LEDs are mixed and connected in series by C gear in sequence
For example, the total number of LEDs of an LED lamp (refer to fig. 5) in a 21.5 inch lcd of PHP V5 series designed by TPV corporation is 48, and the design requirement of the LED lamp is as follows by using a 6-string and 8-parallel design method: the forward conduction voltage of the LED lamp tube is VF, and the classification is selected as A grade: 2.9V-3.0V, B gear: 3.0V-3.1V, C gear: 3.1V-3.2V; secondly, each LED lamp string in each LED lamp tube (such as the 1 st LED lamp string D11, D21.. D61, the 2 nd LED lamp string D12, D22.. D62,. 8 th LED lamp string D18 and D28.. D68) uses the same grade, namely 6 LEDs in series in each LED lamp string are all in A grade or B grade, or each LED lamp string adopts 3A grade materials and 3C grade materials to carry out mixed application (the specification of the LED lamp tube parameters in a PHP V5 series 21.5 inch liquid crystal display is that the typical value of the working total current of 6 strings of 8 LED lamp tubes is defined as 480mA, the upper limit value and the lower limit value of the working voltage of the LED lamp tube are defined as 17.4V-18.6 V. LEDs, the VF value of the LED lamp tube particles in the LED lamp tube is designed in B grade according to the requirement of the LED lamp tube of manufacturers, namely, the forward conduction voltage of most LED products is basically between 3.0V 3.3-3.0V, due to product process problems, the forward conduction voltage of a few led products falls in class a: 2.9V-3.0V, and C gear: 3.1V-3.2V, when each LED lamp string adopts A-grade or B-grade light-emitting diode material, the actual working voltage of the LED lamp tube can meet the specification upper and lower limits of the LED lamp tube: 17.4V-18.6V, when each LED string completely adopts C-grade LED material, the actual working voltage of the LED lamp tube falls: between 18.6V-19.2V, can't satisfy LED fluorescent tube specification requirement, if all adopt 3A shelves material spare + 3C shelves material spare to carry out the application of mixing and taking with each LED lamp cluster, then LED fluorescent tube actual operating voltage still can satisfy LED fluorescent tube specification upper and lower limit: 17.4V-18.6V, so that the LED particles produced by manufacturers can be basically applied without waste).
As shown in fig. 6, in the LED lamp design method of the present invention, a power adapter is used to directly supply power to LED lamps, each LED lamp is formed by connecting P2 light emitting diodes in a parallel-to-serial design, each LED lamp includes N2 parallel-connected groups of LEDs arranged in series, each parallel-connected group of LEDs is formed by connecting M2 light emitting diodes in parallel, where N2 is 4, 5, 6, or 7, P2= N2M 2, and the forward conduction voltage of P2 light emitting diodes of each LED lamp is VF.
Preferably, the voltage VF is divided into a gear A with a voltage range of 2.9V-3.0V, a gear B with a voltage range of 3.0V-3.1V and a gear C with a voltage range of 3.1V-3.2V; m2 LEDs of each LED parallel group are all connected with an A gear, a B gear or a C gear, when N2 is 5 or 7 odd numbers, N2 parallel groups are designed in a serial connection mode that each parallel group is the A gear or the B gear in sequence, when N2 is 4 or 6 even numbers, N2 parallel groups are designed in a serial connection mode that each parallel group is the A gear or the B gear or N2/2A gear parallel groups and N2/2C gear parallel groups are mixed and overlapped in sequence.
For example, the total number of the LEDs of the LED tube (refer to fig. 6) in the 21.5 inch lcd of AOC B2 series designed by TPV company is 48, and a design method that 6 parallel groups are connected in series in sequence, and each parallel group is formed by 8 LEDs connected in parallel is adopted), the design requirements of the LED tube are as follows: the forward conducting voltage VF of the light emitting diode in the LED lamp tube is selected and classified as A grade: 2.9V-3.0V, B gear: 3.0V-3.1V, C gear: 3.1V-3.2V; each parallel group (such as the 1 st parallel group D11, D12.. D18.. 6 th parallel group D61, D62.. D68) can only use the same gear (A gear, B gear or C gear material pieces); connecting the parallel groups in series according to the sequence, and connecting the parallel groups with the parallel groups: all the A-grade material parts, all the B-grade material parts, or 3 parallel groups of the A-grade material parts and 3 parallel groups of the C-grade material parts are mixed (the specification of the parameters of the LED lamp tube in 21.5 inch liquid crystal displays of AOC B2 series is that the typical value of the total working current of 8 parallel 6 strings of LED lamp tubes is defined as 480mA, the upper and lower limits of the working voltage of the LED lamp tube are defined as 17.4V-18.6V, the VF value of the LED particles in the LED lamp tube is designed in the B grade by the LED manufacturer according to the specification requirement of the LED lamp tube, namely, the forward conducting voltage of most LED products is basically between 3.0V-3.1V, due to the product process problem, the forward conducting voltage of a few LED products is between the A grade of 2.9V-3.0V, and the C grade of 3.1V-3.2V, when the parallel groups of each LED lamp tube adopt the A-grade material parts or the B-grade material parts, the actual working voltage of the LED lamp tube can meet the specification upper and lower limits of the LED lamp tube: 17.4V-18.6V, when the parallel group of each LED lamp tube all adopts C-grade LED material, the actual working voltage of the LED lamp tube will fall: between 18.6V and 19.2V, the specification requirement of the LED lamp tube cannot be met, if the parallel group of each LED lamp tube adopts 3 parallel groups as an A material level part and 3 parallel groups as a C material level part for mixed application, the actual working voltage of the LED lamp tube still meets the upper and lower limits of the specification of the LED lamp tube: 17.4V-18.6V, so that the LED particles produced by manufacturers can be basically applied without waste).
Claims (9)
1. With the drive circuit of power adapter direct power supply for LED fluorescent tube, including power adapter, LED fluorescent tube, N channel MOS pipe Q1 and mainboard, 220V city alternating current is used for carrying out the output direct current behind the voltage conversion, its characterized in that is connected to power adapter's input electricity: the power supply circuit also comprises a Vcc power supply control circuit, an operational amplifier OP, a current sampling resistor R1 and a reference voltage Vref, wherein the input end of the LED lamp tube is electrically connected with the output end of the power adapter, the output end of the LED lamp tube is electrically connected with the drain end of an N-channel MOS tube Q1, the source end of an N-channel MOS tube Q1 is electrically connected with one end of a current sampling resistor R1, the other end of the current sampling resistor R1 is grounded, the grid end of an N-channel MOS tube Q1 is electrically connected with one end of a resistor R2, the two ends of a parasitic capacitor Cgd in the N-channel MOS tube Q1 are respectively electrically connected with one end of the current sampling resistor R1 and one end of a resistor R2, the other end of the resistor R2 is electrically connected with the output end of the operational amplifier OP, the grounding end of the operational amplifier OP is electrically connected with the output end of the Vcc power supply control circuit, one input end of the Vcc power supply control circuit is electrically connected with the output end of the power adapter, the other input end of the Vcc power supply control circuit receives an On off/On switch signal output from a GPIO port of an image processor in the mainboard, the negative input end of the operational amplifier OP is electrically connected with the source end of the N-channel MOS tube Q1 and one end of the current sampling resistor R1, the positive input end of the operational amplifier OP is electrically connected with one end of a resistor R3 and one end of a resistor R4, the other end of the resistor R3 is grounded, the other end of the resistor R4 is electrically connected with the reference voltage Vref, and the positive input end of the operational amplifier OP receives a PWM dimming signal output by the other GPIO port of the image processor in the mainboard to adjust and control the average current of the LED lamp tube.
2. The driving circuit for directly supplying power to an LED tube using a power adapter as claimed in claim 1, wherein: the Vcc power supply control circuit comprises a voltage stabilizing diode Z1, a resistor R5, a triode Q2 and a triode Q3, wherein the power supply end of the operational amplifier OP is electrically connected with the collector of the triode Q3 through a voltage stabilizing diode Z1 and a resistor R7 in sequence, the emitter of the triode Q3 is electrically connected with the output end of the power adapter, the base of the triode Q3 is electrically connected with one end of a resistor R6, two ends of the resistor R5 are respectively electrically connected with the output end of the power adapter and one end of a resistor R6, the other end of the resistor R6 is electrically connected with the collector of the triode Q2, the emitter of the triode Q2 is grounded, and the base of the triode Q2 receives an On/off switching signal through a resistor R8.
3. The driving circuit for directly supplying power to an LED tube using a power adapter as claimed in claim 1, wherein: the reference voltage Vref is a DC voltage output by a DC-DC circuit in the main board.
4. The driving circuit for directly supplying power to an LED tube using a power adapter as claimed in claim 1, wherein: the input end of the power adapter is electrically connected with 220V commercial alternating current to carry out voltage conversion and then output 19V direct current voltage.
5. The driving circuit for directly supplying power to an LED tube using a power adapter as claimed in claim 1, wherein: the frequency of the PWM dimming signal is greater than 20 KHZ.
6. The driving circuit for directly supplying power to an LED tube using a power adapter as claimed in claim 1, wherein: each LED lamp tube is formed by connecting P1 light emitting diodes in a serial-to-parallel design mode, each LED lamp tube comprises M1 LED lamp strings which are arranged in parallel, each LED lamp string is formed by sequentially connecting N1 light emitting diodes in series, wherein N1 is 4, 5, 6 or 7, P1= N1M 1, and the forward conducting voltage of the P1 light emitting diodes of each LED lamp tube is VF.
7. The driving circuit for directly supplying power to an LED tube using a power adapter as claimed in claim 6, wherein: the voltage VF is divided into a gear A with the voltage range of 2.9V-3.0V, a gear B with the voltage range of 3.0V-3.1V and a gear C with the voltage range of 3.1V-3.2V; when N1 is 5 or 7 odd numbers, N1 light emitting diodes of each LED string are all connected in series by adopting an A gear or a B gear in sequence, when N1 is 4 or 6 even numbers, N1 light emitting diodes of each LED string are all connected in series by adopting an A gear or a B gear, or N1/2 light emitting diodes of each LED string are connected in series by adopting an A gear and the rest N1/2 light emitting diodes are mixed and matched by adopting a C gear in sequence.
8. The driving circuit for directly supplying power to an LED tube using a power adapter as claimed in claim 1, wherein: each LED lamp tube is formed by connecting P2 light emitting diodes in a parallel-series design mode, each LED lamp tube comprises N2 LED parallel groups which are arranged in series, each LED parallel group is formed by connecting M2 light emitting diodes in parallel, wherein N2 is 4 or 5 or 6 or 7, P2= N2M 2, and the forward conducting voltage of the P2 light emitting diodes of each LED lamp tube is VF.
9. The driving circuit for directly powering an LED tube with a power adapter as claimed in claim 8, wherein: the voltage VF is divided into a gear A with the voltage range of 2.9V-3.0V, a gear B with the voltage range of 3.0V-3.1V and a gear C with the voltage range of 3.1V-3.2V; m2 LEDs of each LED parallel group are all connected with an A gear, a B gear or a C gear, when N2 is 5 or 7 odd numbers, N2 parallel groups are designed in a serial connection mode that each parallel group is the A gear or the B gear in sequence, when N2 is 4 or 6 even numbers, N2 parallel groups are designed in a serial connection mode that each parallel group is the A gear or the B gear or N2/2A gear parallel groups and N2/2C gear parallel groups are mixed and overlapped in sequence.
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| CN112839406B (en) * | 2019-11-07 | 2023-05-30 | 华润微集成电路(无锡)有限公司 | Linear LED driving system and driving method |
| CN110798934A (en) * | 2019-11-08 | 2020-02-14 | 湖南烁光照明工程有限公司 | Centralized power supply brightening system |
| EP4080696B1 (en) * | 2019-12-20 | 2023-12-13 | Suteng Innovation Technology Co., Ltd. | Laser emission circuit and lidar |
| CN111693841B (en) * | 2020-06-22 | 2022-12-02 | 沃尔特电子（苏州）有限公司 | MOSFET (Metal-oxide-semiconductor field Effect transistor) endurance capability test method |
| CN112512178B (en) * | 2020-11-12 | 2023-08-29 | 深圳智芯半导体科技有限公司 | Control circuit for linear constant current driving PWM dimming quick response |
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| CN102833916A (en) * | 2012-08-23 | 2012-12-19 | 冠捷显示科技（厦门）有限公司 | DC (direct current) dimming type LED (Light Emitting Diode) drive circuit |
| CN105960070A (en) * | 2016-07-13 | 2016-09-21 | 福建捷联电子有限公司 | Single-feedback direct-push type DC light-dimming LED tube driving circuit |
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| CN103165084B (en) * | 2013-03-11 | 2015-08-19 | 深圳市华星光电技术有限公司 | Liquid crystal display and LED backlight thereof |
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| CN102833916A (en) * | 2012-08-23 | 2012-12-19 | 冠捷显示科技（厦门）有限公司 | DC (direct current) dimming type LED (Light Emitting Diode) drive circuit |
| CN105960070A (en) * | 2016-07-13 | 2016-09-21 | 福建捷联电子有限公司 | Single-feedback direct-push type DC light-dimming LED tube driving circuit |
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