A linear drive circuit, method and lighting system applying the same

Abstract

The linear driving circuit, the method and the lighting system provided by the application comprise n power switch tubes and n sub-linear driving modules, each of the sub-linear driving modules comprises an operational amplifier module, the operational amplifier module receives a current sampling signal and a corresponding reference voltage signal, and an output end of the operational amplifier module acts on a control end of a corresponding power switch tube; the sub-linear driving module corresponding to the first n-1 segments of LEDs further comprises a pull-up module, and output ends of the operational amplifier module and the pull-up module corresponding to the first n-1 segments of LEDs are connected together, when an input voltage drops, the pull-up module is used to make the power switch tube corresponding to the segment of LEDs corresponding to the input voltage quickly conductive. In the input voltage drop process, the pull-up module is introduced to realize the quick conduction of the power switch tube corresponding to the segment of LEDs corresponding to the input voltage, so that the problem of the input current overshooting downward caused by the slow opening time of the power switch tube due to the large parasitic capacitance of the power switch tube can be avoided, and the stability of the system is improved.

Description

Technical Field

[0001] This invention relates to the field of LED driving technology, and more specifically to a linear driving circuit, method, and lighting system using the same. Background Technology

[0002] Figure 1 The diagram shows a two-stage LED lighting circuit in the prior art. When the input voltage Vin can only power LED1, the first operational amplifier OP1 and the power switch M1 provide current to LED1. When the input voltage Vin rises to a certain value and can power both LED1 and LED2, the power switch M1 is turned off, and the second operational amplifier OP2 and the power switch M2 provide the operating current for both LED1 and LED2. The input voltage Vin is obtained by rectifying the AC mains power through a rectifier. Its shape is a dome wave. When the input voltage Vin rises to its peak value, it will decrease. As the input voltage Vin decreases, it will be insufficient to power LED2. Therefore, LED2 will turn off. At this time, the first operational amplifier OP1 and the power switch M1 need to work again to provide current to LED1. However, during the conduction process of the power switch M1, due to the large parasitic capacitance on the power switch M1, M1 will conduct relatively slowly. Relying solely on the first operational amplifier OP1 to control the power switch M1 will cause a downward overshoot of the input current, which will affect the stability of the system. Therefore, it is necessary to propose a new driving scheme to solve the problems existing in the prior art. Summary of the Invention

[0003] To address the aforementioned technical problems, the present invention provides a linear driving circuit, a method, and a lighting system using the same.

[0004] According to a first aspect of the present invention, a linear driving circuit is provided for use in a lighting system, the lighting system comprising n LEDs connected in series, wherein the n LEDs are powered by an input voltage obtained by rectifying mains power; n is greater than or equal to 2; characterized in that the linear driving circuit comprises:

[0005] There are n power switching transistors, the first terminals of which respectively receive electrical signals transmitted from the negative terminals of the n LED segments, and the second terminals of the n power switching transistors are connected together and connected to the ground terminal through a current sampling module;

[0006] There are n sub-linear drive modules, the first input terminal of each of the n sub-linear drive modules is connected to n reference voltage signals respectively, the second input terminal of each of the n sub-linear drive modules receives the current sampling signal sampled by the current sampling module, and the output terminal is connected to the control terminal of each of the n power switching transistors respectively.

[0007] Each sub-linear drive module includes an operational amplifier module, which receives the current sampling signal and the corresponding reference voltage signal. The output terminal of the operational amplifier module is the output terminal of the sub-linear drive module. The sub-linear drive module corresponding to the first n-1 LED segments also includes a pull-up module. The output terminals of the operational amplifier module and the pull-up module corresponding to the first n-1 LED segments are connected together.

[0008] When the input voltage drops, the pull-up module enables the power switch corresponding to the LED segment with the input voltage to be quickly turned on.

[0009] Optionally, when the input voltage drops, the pull-up module generates an effective pull-up signal based on the first output signal generated inside the operational amplifier module and applies it to the control terminal of the power switch corresponding to the LED segment.

[0010] Optionally, the operational amplifier module is a two-stage operational amplifier structure, including a first-stage operational amplifier and a second-stage operational amplifier, and the first output signal is generated at the output terminal of the first-stage operational amplifier.

[0011] Optionally, the pull-up module includes a control signal generation module and a pull-up signal generation module. The control signal generation module generates a first control signal based on the first output signal, and the pull-up signal generation module generates the pull-up signal based on the first control signal.

[0012] Optionally, the control signal generation module includes a pull-up current module and a pull-down current module. The control terminal of the pull-down current module receives the first output signal, and the output terminals of the pull-up current module and the pull-down current module are connected together to output the first control signal. When the input voltage decreases, the pull-down capability of the pull-down current module corresponding to the LED segment corresponding to the input voltage decreases, and the pull-up signal generation module corresponding to the LED segment corresponding to the input voltage generates an effective pull-up signal based on the first control signal.

[0013] Optionally, the pull-up current module includes a first transistor that generates a pull-up current by mirroring the bias current of the operational amplifier module.

[0014] Optionally, the pull-down current module includes a second transistor, which is an N-type transistor, and its control terminal receives the first output signal.

[0015] Optionally, the pull-up signal generation module includes a third transistor, which is connected between the power supply voltage and the control terminal of the power switch corresponding to the LED segment, and the power supply voltage supplies power to each sub-linear drive module;

[0016] The third transistor is an N-type transistor, and its control terminal receives the first control signal; or...

[0017] The third transistor is a P-type transistor, and the control terminal of the third transistor receives the inverted signal of the first control signal.

[0018] Optionally, an impedance module is provided at the output terminal of the first-stage operational amplifier to reduce the impedance of the output terminal of the first-stage operational amplifier, and the output terminal of the first-stage operational amplifier is used as the secondary pole.

[0019] Optionally, the impedance module includes a first resistor disposed between the output terminal of the first-stage operational amplifier and the ground terminal;

[0020] The first-stage operational amplifier has a P-type transistor input structure, with the drain of the P-type transistor connected to the reference voltage signal serving as the output terminal of the first-stage operational amplifier; a second resistor is also provided between the drain of another P-type transistor and the ground terminal, and the resistance values ​​of the first resistor and the second resistor are equal.

[0021] Optionally, the operational amplifier module further includes a drive voltage conversion circuit, which is used to boost the drive voltage output by the second-stage operational amplifier and the pull-up signal generation module to a second voltage.

[0022] Optionally, the driving voltage conversion circuit includes a first current mirror module and a second current mirror module. The first operational amplifier and the first current mirror module are powered by a first power supply voltage. The first current mirror module mirrors the bias current of the first operational amplifier.

[0023] The second current mirror module is powered by the second power supply voltage. The second current mirror module mirrors the current of the first current mirror module. The second operational amplifier receives the current output by the second current mirror module. The second power supply voltage is greater than the first power supply voltage.

[0024] Optionally, the second-stage operational amplifier receives the current output from the second current mirror module through a voltage-resistant transistor, and the connection terminal of the voltage-resistant transistor near the second current mirror module is used as the output terminal of the operational amplifier module.

[0025] Optionally, the pull-up signal generation module is connected between the second power supply voltage and the control terminal of the power switch corresponding to the LED segment.

[0026] Optionally, each power switch is set up separately from its corresponding operational amplifier module.

[0027] Optionally, corresponding to n LED segments, the n reference voltage signals increase sequentially.

[0028] This invention also provides a linear driving method applied to a lighting system, the lighting system comprising n LEDs connected in series, the n LEDs being powered by an input voltage obtained by rectifying mains power; n is greater than or equal to 2; the linear driving method is characterized in that, based on the linear driving circuit described above, when the input voltage drops, the pull-up module enables the power switch corresponding to the LED segment corresponding to the input voltage to conduct rapidly.

[0029] The present invention also provides a lighting system comprising n LEDs connected in series, wherein the n LEDs are powered by an input voltage obtained by rectifying the mains power; n is greater than or equal to 2; characterized in that the lighting system comprises the linear drive circuit described above.

[0030] The beneficial effects of the present invention include at least the following:

[0031] The present invention provides a linear driving circuit, method, and lighting system. The lighting system includes n LEDs connected in series. The linear driving circuit includes n power switches and n sub-linear driving modules, each corresponding to one of the n LED segments. Each sub-linear driving module includes an operational amplifier module that receives a current sampling signal and a corresponding reference voltage signal. The output of the operational amplifier module acts on the control terminal of the corresponding power switch. The sub-linear driving module corresponding to the first n-1 LED segments also includes a pull-up module. The outputs of the operational amplifier module and the pull-up module corresponding to the first n-1 LED segments are connected together. When the input voltage decreases, the pull-up module enables the power switch corresponding to the LED segment with the input voltage to quickly turn on. During the decrease of the input voltage Vin, this invention introduces a pull-up module to achieve rapid turn-on of the power switch corresponding to the LED segment with the input voltage Vin. This avoids the problem of downward overshoot of the input current caused by the slow turn-on time of the power switch due to its large parasitic capacitance, thus improving the stability of the system.

[0032] Furthermore, an impedance module is set at the output terminal of the first-stage operational amplifier to reduce its impedance. The output terminal of the first-stage operational amplifier is designated as the secondary pole, and the output terminal of the second-stage operational amplifier is designated as the primary pole. When the power switch and operational amplifier module are separate, the parasitic capacitance at the control terminal of the power switch is relatively large, making this pole closer to the origin than the pole at the output terminal of the first-stage operational amplifier. Therefore, this pole can be designated as the primary pole. Compared to existing technologies that use Miller compensation, which makes loop compensation difficult in applications with large parasitic capacitances, the solution of this invention can effectively achieve system stability.

[0033] Furthermore, a drive voltage conversion circuit is also provided in the operational amplifier module. The drive voltage conversion circuit is used to boost the drive voltage output by the second-stage operational amplifier and the pull-up signal generation module to the second voltage, so as to achieve full conduction of the power switching transistor.

[0034] It should be noted that the above general description and the following detailed description are exemplary and explanatory only, and do not limit the present invention. Attached Figure Description

[0035] Figure 1 A schematic diagram of a two-segment LED lighting circuit in the prior art is shown;

[0036] Figure 2 A schematic diagram of a linear drive circuit provided by the present invention is shown;

[0037] Figure 3 A schematic diagram of sub-linear drive module 1 is shown;

[0038] Figure 4 This invention illustrates one embodiment of the control signal generation module and pull-up signal generation module provided by the present invention;

[0039] Figure 5 This invention illustrates a specific circuit embodiment of the operational amplifier module and pull-up module provided by the present invention;

[0040] Figure 6 This paper illustrates another specific circuit embodiment of the operational amplifier module and pull-up module provided by the present invention;

[0041] Figure 7 This illustrates yet another specific circuit embodiment of the operational amplifier module and pull-up module provided by the present invention. Detailed Implementation

[0042] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in various forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0043] Figure 2 The diagram shows a schematic of a linear drive circuit provided by this invention, applied in a lighting system. The lighting system includes n LEDs connected in series, where n is greater than or equal to 2. These n LEDs are powered by an input voltage Vin, which is obtained by rectifying AC mains power. The linear drive circuit includes n power switches and n sub-linear drive modules. The first terminal of each of the n power switches receives an electrical signal transmitted from the negative terminal of one of the n LEDs. (Example) Figure 2In this configuration, the first terminals of n power switching transistors are connected to the negative terminals of n LED segments respectively. Of course, in other embodiments, other components can be added between the LEDs and power switching transistors according to the actual application. The second terminals of the n power switching transistors are connected together and connected to the ground terminal through a current sampling module. The first input terminals of the n sub-linear drive modules are respectively connected to n reference voltage signals (Vref1-Vrefn), and the second input terminals of each module receive the current sampling signal Vcs sampled by the current sampling module. The output terminals are respectively connected to the control terminals of the n power switching transistors. Each sub-linear drive module includes an operational amplifier module OPi, 1≤i≤n. The operational amplifier module receives the current sampling signal Vcs and the corresponding reference voltage signal Vrefi, and the output terminal of the operational amplifier module is the output terminal of the sub-linear drive module. The sub-linear drive module corresponding to the first n-1 LED segments also includes a pull-up module. The output terminals of the operational amplifier module and the pull-up module corresponding to the first n-1 LED segments are connected together. When the input voltage Vin decreases, the pull-up module quickly turns on the power switching transistor corresponding to the LED segment with that input voltage.

[0044] exist Figure 2 The current sampling module uses a sampling resistor Rcs, and the current flowing through the LED is obtained by sampling the voltage drop Vcs across Rcs. Of course, in other embodiments, current sampling can also be achieved through other methods or by a simple modification of the sampling resistor Rcs. For n LED segments, n reference voltage signals increase sequentially, i.e., Vref1... <Vref2<……<Vrefn。

[0045] Furthermore, when the input voltage Vin decreases, the pull-up module generates an effective pull-up signal based on the first output signal generated internally by the operational amplifier module. This signal is applied to the control terminal of the power switch corresponding to the corresponding LED segment, thereby enabling the rapid turn-on of the power switch corresponding to the LED segment. For example, ... Figure 2As shown, when the input voltage Vin decreases, causing LED3 to switch from the on state to the off state, and Vin can only supply power to the first two LEDs (i.e., LED1 and LED2), the power switch M2 corresponding to LED2 needs to switch from the off state to the on state. As the current sampling signal Vcs decreases, the pull-up module 2 generates a pull-up signal based on the first output signal V2 generated inside the operational amplifier module OP2, which acts on the control terminal of the power switch M2, causing the power switch M2 to quickly turn on. Similarly, when the input voltage Vin continues to decrease, and can only supply power to LED1, LED2 switches from the on state to the off state. At this time, the power switch M1 corresponding to LED1 needs to switch from the off state to the on state. As the current sampling signal Vcs decreases, the pull-up module 1 generates a pull-up signal based on the first output signal V1 generated inside the operational amplifier module OP1, which acts on the control terminal of the power switch M1, causing the power switch M1 to quickly turn on. During the decrease of input voltage Vin, a pull-up module is introduced to enable the rapid turn-on of the power switch corresponding to the LED segment of the input voltage Vin. This avoids the problem of downward overshoot of input current caused by the slow turn-on time of the power switch due to its large parasitic capacitance, thus improving the stability of the system.

[0046] In this invention, the first n-1 sub-linear drive modules n-1 can adopt the same structure, and the operational amplifier module in sub-linear drive module n can have the same structure as the operational amplifier module in the first n-1 sub-linear drive modules. The following description takes sub-linear drive module 1 as an example. Figure 3 The diagram shows a schematic of a sub-linear drive module 1. The operational amplifier module OP1 is a two-stage operational amplifier structure, including a first-stage operational amplifier and a second-stage operational amplifier. A first output signal V1 is generated at the output terminal of the first-stage operational amplifier. The pull-up module includes a control signal generation module 20 and a pull-up signal generation module 10. The control signal generation module 20 generates a first control signal VK1 based on the first output signal V1, and the pull-up signal generation module 10 generates a pull-up signal based on the first control signal VK1. The output terminal of the second-stage operational amplifier, i.e., the output terminal of the operational amplifier module, is connected to the output terminal of the pull-up signal generation module, outputting a signal VG1 to the control terminal of the power switch transistor M1.

[0047] Furthermore, Figure 4The diagram illustrates an embodiment of the control signal generation module 20 and pull-up signal generation module 10 provided by the present invention. The control signal generation module 20 includes a pull-up current module 30 and a pull-down current module 40. The control terminal of the pull-down current module 40 receives a first output signal V1. The output terminals of the pull-up current module 40 and the pull-down current module 30 are connected together to output a first control signal VK1. When the input voltage Vin decreases, the pull-down capability of the pull-down current module 40 corresponding to the LED segment corresponding to the input voltage Vin decreases, and the pull-up signal generation module 10 corresponding to the LED segment corresponding to the input voltage Vin generates an effective pull-up signal based on the first control signal VK1. As an embodiment of the present invention, the pull-up current module 30 includes a first transistor MX1, which generates a pull-up current through the bias current of the mirror operational amplifier module. The bias current can be implemented using existing circuitry, which will not be described in detail here. The pull-down current module 40 includes a second transistor MX2, which is an N-type transistor, and its control terminal receives the first output signal V1. The pull-up signal generation module 10 includes a third transistor MX3, which is connected between the power supply voltage and the control terminal of the power switch corresponding to the LED segment (it should be noted that in this article, A is connected between B and C, but it is not limited to only A between B and C, and also includes the case where other components are provided besides A). The power supply voltage powers each sub-linear drive module. As one embodiment of the present invention, such as... Figure 4 As shown, the power supply voltage is Vcc, the third transistor MX3 is an N-type transistor, and the control terminal of the third transistor MX3 receives the first control signal VK1. In another embodiment of the invention, the third transistor MX3 can also be a P-type transistor; in this case, the control terminal of the third transistor MX3 receives the inverted signal of the first control signal VK1.

[0048] for Figure 4 In the embodiment, as the input voltage Vin decreases, due to the different reference voltage settings, the current sampling signal Vcs will decrease when different power switches switch. The current sampling signal Vcs will decrease from being greater than the reference voltage signal value of the op-amp module corresponding to the LED segment with the current input voltage to being less than the reference voltage signal value of the op-amp module. Therefore, during this process, the first output signal of the first stage op-amp in the op-amp module will decrease. When it decreases to below the threshold of the second transistor MX2, the first control signal VK1 will be pulled high, thereby turning on the third transistor MX3 and realizing the rapid turn-on of the corresponding power switch.

[0049] It should be noted that, Figure 4The pull-up current module, pull-down current module, and pull-up signal generation module described herein are just one embodiment of this paper, and other modifications can be made to achieve the same function as described herein. Furthermore, the transistors mentioned above and below can refer to a single transistor or an equivalent transistor (i.e., an equivalent transistor composed of multiple transistors connected in series and parallel).

[0050] To further understand the present invention, Figure 5 This illustration shows a specific circuit embodiment of the operational amplifier module and pull-up module provided by the present invention (using sub-linear drive module 1 as an example). The first-stage operational amplifier has a P-type transistor input structure, that is, the fourth transistor MX4 and the fifth transistor MX5 are both P-type transistors, forming a P-type transistor pair. The control terminal of the fourth transistor MX4 receives the reference voltage signal Vref1, and the control terminal of the fifth transistor MX5 receives the current sampling signal Vcs. The drain of the fourth transistor MX4 is the output terminal of the first-stage operational amplifier, outputting the first output signal V1. The eighth transistor MX8 constitutes the second-stage operational amplifier, and the drain of the eighth transistor MX8 serves as the output terminal of the operational amplifier module. The ninth transistor MX9 and the tenth transistor MX10 are used to mirror the bias current, providing the corresponding current for the operation of the operational amplifier module. The specific working principle of this circuit is as follows: Taking the input voltage Vin dropping to the point where it only powers LED1 as an example, LED2 switches from the on state to the off state. When LED2 is on, the current sampling signal Vcs is greater than the reference voltage signal Vref1. At this time, the first stage operational amplifier output V1 in the operational amplifier module OP1 is high. This high level turns on the second transistor MX8 and the second transistor MX2 (pull-down current module). Therefore, the operational amplifier module OP1 outputs a low level, and the third transistor MX3 (pull-up signal generation module) is not turned on. At this time, the power switch M1 is off. When LED2 is off, the current sampling signal Vcs will drop. When Vcs drops below Vref1, the first output signal V1 will drop rapidly. When V1 drops to near the threshold of the second transistor MX2, the first control signal VK1 will be pulled high, and the third transistor MX3 will turn on. The control terminal of the power switch M1 will be pulled high through the third transistor MX3, making it turn on quickly. Here, the multiple of the mirror bias current of the ninth transistor M9 can be set to be greater than the multiple of the mirror bias current of the first transistor MX1, that is, the pull-up capability of the ninth transistor M9 is greater than the pull-up capability of the first transistor MX1. The parameters of the eighth transistor MX8 and the second transistor MX2 are the same, that is, they have the same pull-down capability. In this way, when the operational amplifier module OP1 is working normally, the first control signal VK1 is pulled low, thereby turning off the third transistor MX3.

[0051] for Figure 2In the operational amplifier (op-amp) structure, when a two-stage op-amp structure is used and the power switching transistors are integrated with the op-amp module, Miller compensation is typically applied between the drain of the fourth transistor MX4 and the drain of the eighth transistor MX8 (i.e., between the outputs of the first and second op-amp stages). This pushes the pole at the drain of the fourth transistor MX4 towards lower frequencies, making it the dominant pole, and pushes the pole at the drain of the eighth transistor MX8 towards higher frequencies, making it the secondary pole, thus stabilizing the loop. However, this setup is only suitable for scenarios with small parasitic capacitances and stable, controllable capacitance values. If used in scenarios where the power switching transistors are discretely mounted on the external chip and have relatively large parasitic capacitances, since these applications are generally used on aluminum substrates with even larger parasitic capacitances, and the parasitic capacitances vary between different PCBs, it is difficult to achieve loop stability control using the aforementioned Miller compensation. To address this, the present invention reduces the impedance of the first-stage op-amp's output by setting an impedance module at its output terminal. The output terminal of the first-stage op-amp is used as the secondary pole, and the output terminal of the op-amp module (i.e., the output terminal of the second-stage op-amp) is used as the primary pole. When the power switch and the op-amp module are set separately, the pole at the control terminal of the power switch is closer to the origin than the pole at the output terminal of the first-stage op-amp due to the large parasitic capacitance. This allows for the addition of a capacitor at this point to make the system more stable. Of course, if the parasitic capacitance of the power switch itself is sufficient to stabilize the system, it is not necessary to add a separate capacitor.

[0052] Furthermore, such as Figure 6 The image shows an embodiment of the operational amplifier module provided by the present invention. Figure 5 Further improvements were made based on the existing foundation, and with Figure 5 The difference lies in the fact that a first resistor Rz1 (also known as the impedance module mentioned above) is placed between the output terminal of the first-stage op-amp (the drain of the four transistors MX4) and the ground terminal; the location of the secondary point can be determined by selecting different values ​​of the first resistor according to the actual application. In order to match the fourth transistor MX4 and the fifth transistor MX5 and make the current on the two transistors as consistent as possible, a second resistor Rz2 is placed between the drain of the fifth transistor MX5 and the ground terminal, and the resistance values ​​of the first resistor Rz1 and the second resistor Rz2 are equal.

[0053] When the power supply voltage Vcc is relatively low compared to the turn-on threshold of the power switch, it may be insufficient to fully turn on the power switch. For example, assuming the power switch threshold is 4V and the power supply voltage Vcc is 5V, it is generally necessary to pull the voltage at the control terminal of the power switch to above 7V to fully turn it on. Therefore, using Vcc alone will not meet this requirement. To address this, the present invention also includes a drive voltage conversion circuit in the operational amplifier module. This circuit converts the drive voltage output by the second-stage operational amplifier and the pull-up signal generation module relative to the power switch's threshold voltage. Figure 5 and Figure 6The voltage is increased from the first voltage to the second voltage. Specifically, Figure 7 The diagram shows another embodiment of the operational amplifier module and pull-up module including a drive voltage conversion circuit provided by the present invention. The drive voltage conversion circuit includes a first current mirror module and a second current mirror module. The first current mirror module includes an eleventh transistor MX11 and a twelfth transistor MX12. The first-stage operational amplifier and the first current mirror module are powered by a first power supply voltage (Vcc), and the first current mirror module mirrors the bias current of the first-stage operational amplifier. The second current mirror module includes a thirteenth transistor MX13, a fourteenth transistor MX14, and a fifteenth transistor MX15. The second current mirror module is powered by a second power supply voltage Vdd, which is greater than Vcc. The second current mirror module mirrors the current of the first current mirror module, and the second-stage operational amplifier (MX8) receives the current output from the second current mirror module. Because Vdd is greater than Vcc, if the eighth transistor MX8 in the second-stage operational amplifier is a low-voltage transistor and directly receives the current output from the fifteenth transistor MX15, MX8 may be damaged. Therefore, in... Figure 7 The diagram also illustrates the voltage-resistant transistor MX16 (which can also be understood as a high-voltage transistor), meaning that the second-stage operational amplifier receives the current output from the second current mirror module through the voltage-resistant transistor. At this time, the connection terminal of the voltage-resistant transistor near the second current mirror module serves as the output terminal of the operational amplifier module. Figure 7 The diagram also shows that the pull-up signal generation module (MX3) is connected between the second power supply voltage Vdd and the control terminal of the power switch corresponding to the LED segment, so as to increase the drive voltage of the control terminal of the power switch when MX3 is turned on. Figure 7 The functions of the remaining circuits are described above and will not be repeated here. Figure 7 The circuit in the diagram can realize the driving voltage output by the second-stage operational amplifier and the pull-up signal generation module relative to... Figure 5 and Figure 6 The voltage is increased from the first voltage to the second voltage. Ignoring the voltage drop across MX15 and MX3, the first voltage can be approximated as Vcc, and the second voltage can be approximated as Vdd.

[0054] It should be noted that, as mentioned above, a pull-up module was set up in the linear drive module for the first n-1 segments, such as... Figure 2 As shown, a pull-up module can also be set in the nth sub-linear drive module. Alternatively, as described above, in... Figure 7 An appropriate impedance module is set up to use the output of the first-stage op-amp as the secondary pole, thereby increasing the stability of the system.

[0055] The present invention also provides a linear driving method, which has the functions of the linear driving circuit described above. Based on the linear driving circuit described above, it can realize the rapid conduction of the power switch corresponding to the LED segment corresponding to the input voltage by means of a pull-up module when the input voltage drops.

[0056] The present invention also provides a method such as Figure 2 The lighting system shown includes the linear drive circuit described above.

[0057] In summary, the linear driving circuit, method, and lighting system provided by this invention include an lighting system comprising n LED segments connected in series. The linear driving circuit comprises n power switches and n sub-linear driving modules, each corresponding to one of the n LED segments. Each sub-linear driving module includes an operational amplifier module that receives a current sampling signal and a corresponding reference voltage signal. The output of the operational amplifier module acts on the control terminal of the corresponding power switch. The sub-linear driving module corresponding to the first n-1 LED segments also includes a pull-up module. The outputs of the operational amplifier module and the pull-up module corresponding to the first n-1 LED segments are connected together. When the input voltage decreases, the pull-up module enables the power switch corresponding to the LED segment with the input voltage to conduct quickly. During the decrease of the input voltage Vin, this invention introduces a pull-up module to achieve rapid conduction of the power switch corresponding to the LED segment with the input voltage Vin. This avoids the problem of downward overshoot of the input current caused by the slow turn-on time of the power switch due to its large parasitic capacitance, thus improving the stability of the system.

[0058] Furthermore, an impedance module is set at the output terminal of the first-stage operational amplifier to reduce its impedance. The output terminal of the first-stage operational amplifier is designated as the secondary pole, and the output terminal of the second-stage operational amplifier is designated as the primary pole. When the power switch and operational amplifier module are separate, the parasitic capacitance at the control terminal of the power switch is relatively large, making this pole closer to the origin than the pole at the output terminal of the first-stage operational amplifier. Therefore, this pole can be designated as the primary pole. Compared to existing technologies that use Miller compensation, which makes loop compensation difficult in applications with large parasitic capacitances, the solution of this invention can effectively achieve system stability.

[0059] Furthermore, a drive voltage conversion circuit is also provided in the operational amplifier module. The drive voltage conversion circuit is used to boost the drive voltage output by the second-stage operational amplifier and the pull-up signal generation module to the second voltage, so as to achieve full conduction of the power switching transistor.

[0060] Finally, it should be noted that the above embodiments are merely examples for clearly illustrating the present invention and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A linear drive circuit, applied in a lighting system, the lighting system comprising n LEDs connected in series, wherein the n LEDs are powered by an input voltage obtained by rectifying mains power; n is greater than or equal to 2; characterized in that, The linear drive circuit includes: There are n power switching transistors, the first terminals of which respectively receive electrical signals transmitted from the negative terminals of the n LED segments, and the second terminals of the n power switching transistors are connected together and connected to the ground terminal through a current sampling module; There are n sub-linear drive modules, the first input terminal of each of the n sub-linear drive modules is connected to n reference voltage signals respectively, the second input terminal of each of the n sub-linear drive modules receives the current sampling signal sampled by the current sampling module, and the output terminal is connected to the control terminal of each of the n power switching transistors respectively. Each sub-linear drive module includes an operational amplifier module, which receives the current sampling signal and the corresponding reference voltage signal. The output terminal of the operational amplifier module is the output terminal of the sub-linear drive module. The sub-linear drive module corresponding to the first n-1 LED segments also includes a pull-up module. The output terminals of the operational amplifier module and the pull-up module corresponding to the first n-1 LED segments are connected together. When the input voltage drops, the pull-up module enables the power switch corresponding to the LED segment with the input voltage to be quickly turned on.

2. The driving circuit according to claim 1, characterized in that, When the input voltage drops, the pull-up module generates an effective pull-up signal based on the first output signal generated inside the operational amplifier module, which is applied to the control terminal of the power switch corresponding to the LED segment.

3. The driving circuit according to claim 2, characterized in that, The operational amplifier module is a two-stage operational amplifier structure, including a first-stage operational amplifier and a second-stage operational amplifier, and the first output signal is generated at the output terminal of the first-stage operational amplifier.

4. The driving circuit according to claim 3, characterized in that, The pull-up module includes a control signal generation module and a pull-up signal generation module. The control signal generation module generates a first control signal based on the first output signal, and the pull-up signal generation module generates the pull-up signal based on the first control signal.

5. The driving circuit according to claim 4, characterized in that, The control signal generation module includes a pull-up current module and a pull-down current module. The control terminal of the pull-down current module receives the first output signal. The output terminals of the pull-up current module and the pull-down current module are connected together to output the first control signal. When the input voltage decreases, the pull-down capability of the pull-down current module corresponding to the LED segment corresponding to the input voltage decreases, and the pull-up signal generation module corresponding to the LED segment corresponding to the input voltage generates an effective pull-up signal based on the first control signal.

6. The driving circuit according to claim 5, characterized in that, The pull-up current module includes a first transistor, which generates a pull-up current by mirroring the bias current of the operational amplifier module.

7. The driving circuit according to claim 5, characterized in that, The pull-down current module includes a second transistor, which is an N-type transistor, and its control terminal receives the first output signal.

8. The driving circuit according to claim 4, characterized in that, The pull-up signal generation module includes a third transistor, which is connected between the power supply voltage and the control terminal of the power switch corresponding to the LED segment. The power supply voltage supplies power to each sub-linear drive module. The third transistor is an N-type transistor, and its control terminal receives the first control signal; or... The third transistor is a P-type transistor, and the control terminal of the third transistor receives the inverted signal of the first control signal.

9. The driving circuit according to claim 3, characterized in that, Each power switch is set up separately from its corresponding operational amplifier module.

10. The driving circuit according to claim 9, characterized in that, An impedance module is set at the output of the first-stage op-amp to reduce the impedance of the first-stage op-amp output, and the output of the first-stage op-amp is used as the secondary pole.

11. The driving circuit according to claim 10, characterized in that, The impedance module includes a first resistor disposed between the output terminal of the first-stage operational amplifier and the ground terminal; The first stage operational amplifier has a P-type transistor input structure, and the drain of the P-type transistor connected to the reference voltage signal is used as the output terminal of the first stage operational amplifier. A second resistor is provided between the drain of another P-type transistor and the ground terminal, and the resistance values ​​of the first resistor and the second resistor are equal.

12. The driving circuit according to any one of claims 4-11, characterized in that, The operational amplifier module further includes a drive voltage conversion circuit, which is used to boost the drive voltage output by the second-stage operational amplifier and the pull-up signal generation module to a second voltage.

13. The driving circuit according to claim 12, characterized in that, The driving voltage conversion circuit includes a first current mirror module and a second current mirror module. The first stage operational amplifier and the first current mirror module are powered by a first power supply voltage. The first current mirror module mirrors the bias current of the first stage operational amplifier. The second current mirror module is powered by the second power supply voltage. The second current mirror module mirrors the current of the first current mirror module. The second operational amplifier receives the current output by the second current mirror module. The second power supply voltage is greater than the first power supply voltage.

14. The driving circuit according to claim 13, characterized in that, The second-stage operational amplifier receives the current output from the second current mirror module through a voltage-resistant transistor, and the connection terminal of the voltage-resistant transistor close to the second current mirror module is used as the output terminal of the operational amplifier module.

15. The driving circuit according to any one of claims 13-14, characterized in that, The pull-up signal generation module is connected between the second power supply voltage and the control terminal of the power switch corresponding to the LED segment.

16. The driving circuit according to claim 1, characterized in that, For n LED segments, the n reference voltage signals increase sequentially.

17. A linear driving method applied to a lighting system, the lighting system comprising n LEDs connected in series, wherein the n LEDs are powered by an input voltage obtained by rectifying mains power; n is greater than or equal to 2; characterized in that, The linear driving method, based on the linear driving circuit of any one of claims 1-16, enables the power switch corresponding to the LED segment corresponding to the input voltage to be quickly turned on through the pull-up module when the input voltage drops.

18. A lighting system comprising n LEDs connected in series, wherein the n LEDs are powered by an input voltage obtained by rectifying mains power; n is greater than or equal to 2; characterized in that, The lighting system includes the linear drive circuit according to any one of claims 1-16.

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