LED linear driving circuit, LED linear driving chip and LED device

Abstract

The utility model provides an LED linear driving circuit, an LED linear driving chip and an LED device. The LED linear driving circuit comprises a series-parallel connection conversion circuit module and a series-parallel connection control module. The series-parallel conversion circuit module and the series-parallel control module are both connected to an external power supply and are powered by an external power supply incoming line; the series-parallel connection conversion circuit module comprises a first LED load and a second LED load; the series-parallel connection control module is used for switching the series-parallel connection state between the first LED load and the second LED load in the series-parallel connection conversion circuit module, and in the series-parallel connection state switching process, the current of the first LED load and the current of the second LED load are both larger than or equal to Is; wherein Is is the defined minimum working current, so that the phenomenon of light flashing when the connection modes between the LED loads are switched is avoided.

Description

Technical Field

[0001] This application relates to the field of LED driving technology, and more specifically, to an LED linear driving circuit, an LED linear driving chip, and an LED device. Background Technology

[0002] With the global application of LED lighting, linear LED driving solutions currently offer the advantage of low cost, and most light sources and luminaires below 10 watts use linear drivers. This is because linear drivers only illuminate the LED when the bus voltage is greater than the LED voltage.

[0003] For market requirements necessitating a full voltage input of 85-264Vac, the LED connection method can be automatically adjusted based on the bus voltage. When the bus voltage is higher than the set voltage, the first and second constant current modules are disconnected, and the first and second LED loads are connected in series, receiving constant current power through the third constant current module. When the bus voltage is lower than the set voltage, the third constant current module operates in switch-on mode, with the first constant current module supplying constant current power to the second LED load, and vice versa. However, existing technology, in order to achieve this process, reduces the current of the first and second constant current modules to 0 before the bus voltage reaches the set voltage. In this case, the third constant current module also cannot supply power to the first and second LED loads, resulting in flickering. Utility Model Content

[0004] The purpose of this application is to provide an LED linear driving circuit, an LED linear driving chip, and an LED device to solve the problem of flashing during the switching of LED connection modes in the prior art, where the LED connection mode is automatically adjusted according to the bus voltage.

[0005] This application provides an LED linear driving circuit, comprising:

[0006] Series-to-parallel conversion circuit module and series-to-parallel control module;

[0007] Both the series-parallel conversion circuit module and the series-parallel control module are connected to an external power supply and are powered by the external power supply line.

[0008] The series-parallel conversion circuit module includes a first LED load and a second LED load;

[0009] The series-parallel control module is used to switch the series-parallel connection state between the first LED load and the second LED load in the series-parallel conversion circuit module. During the series-parallel connection state switching process, the current of both the first LED load and the second LED load is greater than or equal to Is; where Is is the defined minimum operating current.

[0010] In some optional implementations, the first terminal of the series-parallel control module is connected to the positive terminal of the external power supply, the second terminal of the series-parallel control module is connected to the input terminal of the second LED load, the third terminal of the series-parallel control module is connected to the output terminal of the first LED load, the fourth terminal of the series-parallel control module is connected to the negative terminal of the external power supply, the fifth terminal of the series-parallel control module is connected to the output terminal of the second LED load, the sixth terminal of the series-parallel control module is connected to the negative terminal of the external power supply, and the input terminal of the first LED load is connected to the positive terminal of the external power supply.

[0011] In some alternative implementations, when the bus voltage reaches the switching threshold, the series-parallel control module switches the series-parallel connection state between the first LED load and the second LED load.

[0012] Specifically, when the bus voltage is greater than the load voltage VLED but less than the switching threshold, the first LED load and the second LED load are connected in parallel; when the bus voltage is greater than the switching threshold, the first LED load and the second LED load are connected in series; during the period when the bus voltage is greater than VLED, the current of both the first LED load and the second LED load is greater than or equal to Is. Here, VLED is the load voltage of the LED load.

[0013] In some optional implementations, the series-parallel control module includes a first linear constant current module, a second linear constant current module, and a third linear constant current module;

[0014] The positive terminal of the external power supply, the first LED load, the first diode, the second LED load, the third linear constant current module, and the negative terminal of the external power supply are connected in sequence; one end of the first linear constant current module is connected to the positive terminal of the first LED load, and the other end is connected to the positive terminal of the second LED load; one end of the second linear constant current module is connected to the negative terminal of the first LED load, and the other end is connected to the negative terminal of the external power supply.

[0015] In some optional implementations, the first linear constant current module is used to provide current I1 to the second LED load, and the second linear constant current module is used to provide current I2 to the first LED load; when the bus voltage is higher than the load voltage and the bus voltage is lower than the switching threshold, the first LED load and the second LED load are connected in parallel, and both I1 and I2 are greater than or equal to Is;

[0016] The third linear constant current module is used to provide power to I3 when the bus voltage is higher than the switching threshold. At this time, the first LED load and the second LED load are connected in series, (I1+I3)≥Is and (I2+I3)≥Is; when the bus voltage is lower than the switching threshold, it operates in the switch-on mode.

[0017] In the above technical solution, when the bus voltage is higher than the switching threshold, the connection mode of the first LED load and the second LED load is switched to series connection, with the third linear constant current module providing I3 power. At this time, the current flowing through the second LED load is (I1+I3), and the current flowing through the first LED load is (I2+I3). Both the current flowing through the first LED load and the current flowing through the second LED load are greater than Is. When the bus voltage is higher than the load voltage VLED and the bus voltage is lower than the switching threshold, the third constant current module operates in switch-on mode. The first constant current module provides current I1 to the second LED load, and the second constant current module provides current I2 to the first LED load. The connection mode of the first LED load and the second LED load is switched to parallel connection. At this time, both I1 and I2 are greater than Is. This embodiment avoids flickering during the switching process of the connection mode of the first LED load and the second LED load by controlling the current flowing through the first LED load and the second LED load to always be greater than Is during the period when the bus voltage is sufficient to turn on the LED. The switching threshold is greater than the load voltage VLED and is a value near 2VLED.

[0018] In some optional implementations, the first linear constant current module includes a first linear compensation module and a first constant current source, and the second linear constant current module includes a second linear compensation module and a second constant current source;

[0019] When the bus voltage is higher than the load voltage VLED and lower than the line compensation threshold VR, the first constant current source and the second constant current source provide constant current power supply.

[0020] When the bus voltage is greater than the line compensation intervention threshold VR, the first linear compensation module intervenes, causing the output current I1 of the first constant current source to decrease as the bus voltage increases; the second linear compensation module intervenes, causing the output current I2 of the second constant current source to decrease as the bus voltage increases.

[0021] In this process, by controlling the intervention timing and linear compensation slope of the first linear compensation module and the second linear compensation module, I1 and I2 are both controlled to be greater than or equal to Is; where VR is the bus voltage corresponding to the intervention timing of the first linear compensation module and the second linear compensation module, and the bus voltage at this timing is greater than the load voltage VLED.

[0022] In the above technical solution, the first linear constant current module and the second linear constant current module have built-in linear compensation. When the bus voltage reaches the linear compensation intervention threshold VR, the linear compensation starts to intervene, and I1 and I2 start to decrease. By controlling the timing of the linear compensation intervention and the linear compensation slope, I1 and I2 are greater than or equal to Is when the bus voltage reaches the switching threshold, so as to avoid I1 and I2 dropping too low and causing the LED to flash.

[0023] In some optional implementations, both the first linear compensation module and the second linear compensation module include: an input AC voltage sampling module, a line compensation starting point design module, and a line compensation slope design module connected in sequence.

[0024] The input AC voltage sampling module is used to obtain the sampled voltage of the bus voltage;

[0025] The line compensation starting point design module is used to obtain the intervention timing;

[0026] The line compensation slope design module is used to obtain the line compensation slope based on the bus voltage and intervention timing, and to determine the constant current source compensation amount based on the line compensation slope.

[0027] In the above technical solution, the linear compensation module's linear compensation process may include one or more linear compensation segments. The start and end points of each linear compensation segment are related to the bus voltage, which is obtained by inputting an AC voltage sampling module to acquire the sampled bus voltage. The linear compensation start point design module is used to determine the start and end points of each linear compensation segment, and the linear compensation slope design module is used to determine the linear compensation slope of each linear compensation segment, thereby determining the current constant current source compensation amount. In this embodiment, the sampling method of the bus voltage is not limited; the bus voltage information can be obtained directly or indirectly. There are no restrictions on the start and end points of each linear compensation segment and the corresponding linear compensation slope; it is only necessary to ensure that after one or more linear compensation segments, when the bus voltage reaches the switching threshold, I1 and I2 are greater than or equal to Is.

[0028] In some alternative implementations, a comparator is also included;

[0029] The comparator's output is connected to the third terminal of the third linear constant current module; the comparator's first input is connected to the second linear compensation module; and the comparator's second input is connected to the reference voltage.

[0030] The comparator outputs a high-level signal to the third linear constant current module when the bus voltage is higher than the switching threshold, and outputs a low-level signal to the third linear constant current module when the bus voltage is lower than the switching threshold.

[0031] In the above technical solution, the linear compensation signal is related to the bus voltage. Therefore, a comparator is used to compare the linear compensation signal with the corresponding reference voltage. When the bus voltage is higher than the switching threshold, a high-level signal is output to the third linear constant current module to control the third linear constant current module to provide constant current power. When the bus voltage is lower than the switching threshold, a low-level signal is output to the third linear constant current module to control the third linear constant current module to operate in the on mode.

[0032] In some alternative implementations, the third linear constant current module includes: a switch, a third operational amplifier, and a third MOSFET;

[0033] The control terminal of the switch is connected to the output terminal of the comparator, the fixed terminal of the switch is connected to the positive input terminal of the third operational amplifier, the negative input terminal of the third operational amplifier is connected to the source of the third MOSFET, the output terminal of the third operational amplifier is connected to the gate of the third MOSFET, the drain of the third MOSFET is connected to the second terminal of the second LED load, and the source of the third MOSFET is connected to the negative terminal of the external power supply through the third resistor; the first contact terminal of the switch is connected to the first power supply, and the second contact terminal of the switch is connected to the second power supply.

[0034] The switch is used to: connect the positive input terminal of the third operational amplifier to the first power supply according to the high-level signal received at its control terminal; and connect the positive input terminal of the third operational amplifier to the second power supply according to the low-level signal received at its control terminal; wherein the voltage VREF2 of the second power supply is greater than the voltage VREF1 of the first power supply.

[0035] In the above technical solution, when the bus voltage is lower than the switching threshold, the current I2 of the second linear constant current module is VREF1 / R, the current flowing through the first LED load is VREF1 / R, the current I1 of the first linear constant current module is VREF1 / R, the current of the third linear constant current module (VREF2 / R) is greater than the current of the first linear constant current module, the third linear constant current module works in the switch-on mode, and the current flowing through the first LED load is VREF1 / R; when the bus voltage is higher than the set voltage, the current of the third linear constant current module is VREF1 / R.

[0036] In some alternative implementations, the second constant current source includes a second operational amplifier and a second MOSFET;

[0037] The first terminal of the second linear compensation module is connected to the first input terminal of the comparator; the second terminal of the second linear compensation module is connected to the drain of the second MOSFET; the third terminal of the second linear compensation module is connected to the positive input terminal of the second operational amplifier, which is also connected to the first power supply; the negative input terminal of the second operational amplifier is connected to the source of the second MOSFET, which is connected to the negative terminal of the external power supply through a second resistor; and the drain of the second MOSFET is also connected to the second terminal of the first LED load.

[0038] In some alternative implementations, the first constant current source includes a first operational amplifier and a first MOSFET;

[0039] The first terminal of the first linear compensation module is connected to the drain of the first MOSFET, and the second terminal of the first linear compensation module is connected to the positive input terminal of the first operational amplifier. The positive input terminal of the first operational amplifier is also connected to the first power supply. The negative input terminal of the first operational amplifier is connected to the source of the first MOSFET, and the drain of the first MOSFET is also connected to the first terminal of the first LED load. The source of the first MOSFET is also connected to the first terminal of the second LED load through the first resistor.

[0040] In some alternative implementations, a diode is also included;

[0041] The drain of the first LED load and the second operational amplifier is connected to point A. Point A is connected to the input terminal of the diode, the output terminal of the diode is connected to point B, and point B is connected to the first terminal of the second LED load and the first resistor.

[0042] In some alternative implementations, a rectifier is also included;

[0043] The positive terminal of the external AC power supply is connected to the positive input terminal of the rectifier, and the negative terminal of the external AC power supply is connected to the negative input terminal of the rectifier; the positive output terminal of the rectifier is connected to the first terminal of the first LED load, and the negative output terminal of the rectifier is connected to the second and third linear constant current modules.

[0044] This application provides an LED linear driver chip, comprising: an LED linear driver circuit as described in any of the above claims, a lead frame, and a molding compound; the LED linear driver circuit is disposed on the lead frame, and the molding compound is used to seal the LED linear driver circuit.

[0045] An LED device provided in this application includes a first LED load, a second LED load, and an LED linear drive circuit as described in any of the above embodiments. Attached Figure Description

[0046] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0047] Figure 1 A functional block diagram of an LED linear driving circuit provided in this application embodiment;

[0048] Figure 2 This is a schematic diagram of an LED linear driving circuit structure provided in an embodiment of this application;

[0049] Figure 3 Current waveforms of three constant current sources provided in one embodiment of this application;

[0050] Figure 4 Current waveform diagram of three constant current sources provided in another embodiment of this application;

[0051] Figure 5 Current waveform diagrams of a first LED load and a second LED load provided in another embodiment of this application;

[0052] Figure 6 The current-voltage characteristic curve of an LED light-emitting diode;

[0053] Figure 7 This is a functional block diagram of the linear compensation module provided in the embodiments of this application. Detailed Implementation

[0054] The technical solutions in the embodiments of this application will now be described with reference to the accompanying drawings.

[0055] This application provides an LED linear driving circuit, comprising:

[0056] Series-to-parallel conversion circuit module and series-to-parallel control module;

[0057] Both the series-parallel conversion circuit module and the series-parallel control module are connected to an external power supply and are powered by the external power supply line.

[0058] The series-parallel conversion circuit module includes a first LED load and a second LED load;

[0059] The series-parallel control module is used to switch the series-parallel connection state between the first LED load and the second LED load in the series-parallel conversion circuit module. During the series-parallel connection state switching process, the current of both the first LED load and the second LED load is greater than or equal to Is; where Is is the defined minimum operating current.

[0060] Where Is is the defined minimum operating current for the LED load; please refer to [reference needed]. Figure 6 , Figure 6 The current-voltage characteristic curve of an LED shows that the current and voltage satisfy the following relationship:

[0061]

[0062] Among them, V T I is the thermal voltage constant, and I0 is the reverse saturation current of the LED.

[0063] For system efficiency, the value of Is should be as small as possible. Ideally, the value of Is should satisfy ΔI / ΔV being much greater than 1. The larger the value of ΔI / ΔV, the better the effect of suppressing system flashing.

[0064] The value of Is can be defined based on the IV characteristic curve of the LED bead. The specific value is based on system efficiency considerations and is not restricted here.

[0065] In some optional implementations, the first terminal of the series-parallel control module is connected to the positive terminal of the external power supply, the second terminal of the series-parallel control module is connected to the input terminal of the second LED load, the third terminal of the series-parallel control module is connected to the output terminal of the first LED load, the fourth terminal of the series-parallel control module is connected to the negative terminal of the external power supply, the fifth terminal of the series-parallel control module is connected to the output terminal of the second LED load, the sixth terminal of the series-parallel control module is connected to the negative terminal of the external power supply, and the input terminal of the first LED load is connected to the positive terminal of the external power supply.

[0066] In some alternative implementations, when the bus voltage reaches the switching threshold, the series-parallel control module switches the series-parallel connection state between the first LED load and the second LED load.

[0067] Specifically, when the bus voltage is greater than the load voltage VLED but less than the switching threshold, the first LED load and the second LED load are connected in parallel; when the bus voltage is greater than the switching threshold, the first LED load and the second LED load are connected in series; during the period when the bus voltage is greater than the load voltage VLED, the current of both the first LED load and the second LED load is greater than or equal to Is. Here, VLED is the load voltage of the LED load.

[0068] Please refer to Figure 1 , Figure 1 The present application provides a functional block diagram of an LED linear driving circuit. The series-parallel control module of this embodiment includes a first linear constant current module SOURCE1, a second linear constant current module SOURCE2, and a third linear constant current module SOURCE3.

[0069] Specifically, the positive terminal of the external power supply, the first LED load LED1s, the first diode D1, the second LED load LED2s, the third linear constant current module SOURCE3, and the negative terminal of the external power supply are connected in sequence; one end of the first linear constant current module SOURCE1 is connected to the positive terminal of the first LED load LED1s, and the other end is connected to the positive terminal of the second LED load LED2s; one end of the second linear constant current module SOURCE2 is connected to the negative terminal of the first LED load LED1s, and the other end is connected to the negative terminal of the external power supply.

[0070] The first linear constant current module is used to provide current I1 to the second LED load, and the second linear constant current module is used to provide current I2 to the first LED load. When the bus voltage is higher than the load voltage and the bus voltage is lower than the switching threshold, the first LED load and the second LED load are connected in parallel, and I1 and I2 are both greater than or equal to Is.

[0071] The third linear constant current module is used to provide power to I3 when the bus voltage is higher than the switching threshold. At this time, the first LED load and the second LED load are connected in series, (I1+I3)≥Is and (I2+I3)≥Is; when the bus voltage is lower than the switching threshold, it operates in the switch-on mode.

[0072] Where Is is the defined minimum operating current, which keeps the first LED load and the second LED load lit without flickering, and VLED is the load voltage of the first LED load and the second LED load.

[0073] In the above technical solution, when the bus voltage is higher than the switching threshold, the connection mode of the first LED load and the second LED load is switched to series connection, with the third linear constant current module providing I3 power. At this time, the current flowing through the second LED load is (I1+I3), and the current flowing through the first LED load is (I2+I3). Both the current flowing through the first LED load and the current flowing through the second LED load are greater than Is. When the bus voltage is higher than the load voltage VLED and the bus voltage is lower than the switching threshold, the third constant current module operates in switch-on mode. The first constant current module provides current I1 to the second LED load, and the second constant current module provides current I2 to the first LED load. The connection mode of the first LED load and the second LED load is switched to parallel connection. At this time, both I1 and I2 are greater than Is. This embodiment avoids flashing during the switching process of the connection mode of the first LED load and the second LED load by controlling the current flowing through the first LED load and the second LED load to always be greater than Is during the period when the bus voltage is sufficient to turn on the LED. Specifically, the switching threshold is greater than the load voltage VLED, and the switching threshold is a value near 2VLED. In particular, the setting of the switching threshold only needs to ensure that the current of I1 or I2 is less than the current when the third linear constant current module outputs constant current.

[0074] Please refer to Figure 2 , Figure 2 This is a schematic diagram of an LED linear driving circuit structure provided in an embodiment of this application.

[0075] In some optional implementations, the first linear constant current module SOURCE1 includes a first linear compensation module LN1 and a first constant current source, and the second linear constant current module SOURCE2 includes a second linear compensation module LN2 and a second constant current source.

[0076] When the bus voltage is higher than the load voltage VLED and lower than the line compensation threshold VR, the first constant current source and the second constant current source provide constant current power supply.

[0077] When the bus voltage is greater than the line compensation intervention threshold VR, the first linear compensation module LN1 intervenes, causing the output current I1 of the first constant current source to decrease as the bus voltage increases; the second linear compensation module LN2 intervenes, causing the output current I2 of the second constant current source to decrease as the bus voltage increases.

[0078] In this process, by controlling the intervention timing and line compensation slope of the first linear compensation module LN1 and the second linear compensation module LN2, I1 and I2 are both controlled to be greater than or equal to Is; where VR is the intervention timing of the first linear compensation module LN1 and the second linear compensation module LN2.

[0079] In the above technical solution, the first linear constant current module SOURCE1 and the second linear constant current module SOURCE2 are equipped with linear compensation. When the bus voltage reaches the linear compensation intervention threshold VR, the linear compensation starts to intervene, and I1 and I2 start to decrease. By controlling the timing of the linear compensation intervention and the linear compensation slope, I1 and I2 are greater than or equal to Is when the bus voltage reaches the switching threshold, so as to avoid I1 and I2 dropping too low and causing the LED to flash.

[0080] Please refer to Figure 7 , Figure 7 The functional block diagram of the linear compensation module provided in the embodiment of this application; the first linear compensation module LN1 and the second linear compensation module LN2 both include: an input AC voltage sampling module, a line compensation starting point design module and a line compensation slope design module connected in sequence;

[0081] The input AC voltage sampling module is used to obtain the sampling voltage of the bus voltage; the line compensation starting point design module is used to obtain the intervention timing; and the line compensation slope design module is used to obtain the line compensation slope based on the bus voltage and the intervention timing, and to determine the constant current source compensation amount based on the line compensation slope.

[0082] In the above technical solution, the linear compensation module's linear compensation process may include one or more linear compensation segments. The start and end points of each linear compensation segment are related to the bus voltage, and the sampled bus voltage is obtained by inputting an AC voltage sampling module. The linear compensation start point design module is used to determine the start and end points of each linear compensation segment, and the linear compensation slope design module is used to determine the linear compensation slope of each linear compensation segment, thereby determining the current constant current source compensation amount. In this embodiment, there are no restrictions on the start and end points of each linear compensation segment and the corresponding linear compensation slope; it is only necessary to ensure that after one or more linear compensation segments, when the bus voltage reaches the switching threshold, I1 and I2 are greater than or equal to Is.

[0083] This solution ensures that during a half-cycle of AC operation, when the bus voltage is sufficient to conduct the LEDs, the LED current remains greater than a set current I when the first LED load (LED1s) and the second LED load (LED2s) switch from parallel to series connection. S This ensures that the range of load voltage variation for the LED always falls within the region where changes in LED current are less sensitive to changes in LED voltage, thus keeping the LED driver system in a stable state and resolving the flickering problem.

[0084] Specifically, the setting of the current line compensation starting point and current line compensation slope K of the first linear constant current module SOURCE1 and the second linear constant current module SOURCE2 will ensure that the line compensation current is not zero before the bus voltage is greater than the voltage of the two strings of LEDs.

[0085] The current flowing through the second LED load is: Vcs3 / R3 + {Vcs1 - [VCOMP1 - VR1] × k1....... - [VCOMPn × (VM - VLEDn) - VRn] × kn} / Rcs1

[0086] The current flowing through the first LED load is: Vcs3 / R3 + {Vcs2 - [VCOMP1 - VR1] × k1....... - [VCOMPn × (VM - VLEDn) - VRn] × kn} / Rcs2

[0087] The output current of the third linear constant current module SOURCE3 is Vcs3 / R3. This current will only be activated when the bus voltage VM is greater than 2VLED+VD1.

[0088] Wherein, the starting point of the line compensation is VCOMPn = MIN[Mn×(VM-VLED1), VXn] or VCOMPn = MIN[Mn×(VM-VLED2), VXn]. The MIN function in the definition of VCOMPn is used to define the maximum value of each line compensation segment. If the line compensation current is already 0 before Mn×(VM-VLED1)>VXn, then the line compensation current is not controlled by VXn. VXn is the starting point of the nth line compensation segment in the design.

[0089] The bus voltage VM is the output voltage of the rectifier bridge, and VD1 is the voltage drop across diode D1. VRn is the system-defined start and end point of the nth line compensation point. Mn represents the voltage division ratio of the sampling resistor at the defined nth line compensation point, and Kn represents the line compensation slope at the nth line compensation point.

[0090] Within one AC half-cycle of any AC load voltage, as the LED transitions from on to off, the parameters defined in the system mathematical equations regarding the variation of the first and second load currents with the VM voltage always satisfy the condition that the first and second load currents are greater than or equal to I. S, ensuring that there is no problem of flashing lights in the system.

[0091] Please refer to Figure 3 , Figure 4 and Figure 5 , Figure 3 , Figure 4 and Figure 5 which are the waveform diagrams of the bus voltage and current provided for this application.

[0092] Taking a system with first-order (n = 1) line compensation and the line compensation current already being 0 when Mn×(VM - VLEDn)>VX as an example:

[0093] In the first half-wave, the peak value of the bus voltage is greater than the VLED voltage but less than the line compensation intervention threshold. At this time, I1 = ILED1, I2 = ILED2, and the first load and the second load are in parallel.

[0094] In the second and third half-waves, the peak value of the bus voltage is greater than the line compensation intervention threshold but less than 2×VLED voltage. At this time, the first load and the second load are still in a parallel relationship, I1 = ILED1, I2 = ILED2. When the bus voltage is greater than the line compensation intervention threshold, the first and second constant current sources decrease with the increase of the bus voltage. At the peak voltage, the constant current source current reaches the minimum value.

[0095] In the fourth half-wave, the peak value of the bus voltage is greater than 2×VLED voltage. At this time, during the conduction period of the two LED loads in the system, there are both parallel moments and series moments.

[0096] During the conduction period when VLED < VM < 2×VLED, the LED loads are in parallel, and the parallel currents generated by the first and second constant current sources flow through the first load and the second load respectively. When VM is greater than the line compensation starting point, the first and second constant current sources decrease with the increase of the bus voltage.

[0097] During the conduction period when VM > 2×VLED, the third constant current source starts to work, and the series current gradually builds up, and the two LED loads form a series relationship. During the establishment process of the series current, the first and second constant current sources will gradually decrease to 0 under the action of the line compensation mechanism. At this time, only the series current I3 flows through the two strings of LED loads in the system.

[0098] Specifically, in the fourth half-wave, when VM is greater than the line compensation starting point, the first and second constant current sources decrease with the increase of the bus voltage. However, before the series current is established, the current values I1 and I2 generated by the first and second constant current sources under the action of the line compensation mechanism are both greater than Is.

[0099] In particular, in the fourth half-wave, when VM is greater than the starting point of line compensation, the first and second constant current sources decrease as the bus voltage increases. However, after the series current begins to build up, the current values ​​I1 and I2 generated by the first and second constant current sources under the line compensation mechanism, together with the gradually built-up I3, satisfy the following relationship: I1 + I3 = ILED1 > Is, I2 + I3 = ILED2 > Is.

[0100] It should be clarified that the changes in the output current of the first linear constant current module / second linear constant current module in the above embodiments are merely examples; in other embodiments, the output current of the first linear constant current module / second linear constant current module may also be a value greater than Is when switching from parallel to series connection.

[0101] In some alternative implementations, a comparator COMP is also included;

[0102] The output of comparator COMP is connected to the third terminal of the third linear constant current module SOURCE3; the first input of comparator COMP is connected to the second linear compensation module LN2; the second input of comparator COMP is connected to the reference voltage.

[0103] The comparator COMP outputs a high-level signal to the third linear constant current module SOURCE3 when the bus voltage is higher than the switching threshold, and outputs a low-level signal to the third linear constant current module SOURCE3 when the bus voltage is lower than the switching threshold.

[0104] In the above technical solution, the linear compensation signal is related to the bus voltage. Therefore, the comparator COMP is used to compare the linear compensation signal with the corresponding reference voltage. When the bus voltage is higher than the switching threshold, a high-level signal is output to the third linear constant current module SOURCE3 to control the third linear constant current module SOURCE3 to provide constant current power. When the bus voltage is lower than the switching threshold, a low-level signal is output to the third linear constant current module SOURCE3 to control the third linear constant current module SOURCE3 to operate in the on mode.

[0105] In some alternative implementations, the third linear constant current module SOURCE3 includes: a switch, a third operational amplifier OP3, and a third MOSFET;

[0106] The control terminal of the switch is connected to the output terminal of the comparator COMP. The fixed terminal of the switch is connected to the positive input terminal of the third operational amplifier OP3. The negative input terminal of the third operational amplifier OP3 is connected to the source of the third MOSFET. The output terminal of the third operational amplifier OP3 is connected to the gate of the third MOSFET. The drain of the third MOSFET is connected to the second terminal of the second LED load LED2s. The source of the third MOSFET is connected to the negative terminal of the external power supply through the third resistor RCS3. The first contact terminal of the switch is connected to the first power supply VREF1, and the second contact terminal of the switch is connected to the second power supply VREF2.

[0107] The switch SW is used to: connect the positive input terminal of the third operational amplifier OP3 to the first power supply VREF1 according to the high-level signal received by its control terminal; and connect the positive input terminal of the third operational amplifier OP3 to the second power supply VREF2 according to the low-level signal received by its control terminal; wherein the voltage of the second power supply VREF2 is greater than the voltage of the first power supply VREF1.

[0108] In the above technical solution, when the bus voltage is lower than the switching threshold, the current I2 of the second linear constant current module SOURCE2 is VREF1 / R, the current flowing through the first LED load LED1s is VREF1 / R, the current I1 of the first linear constant current module SOURCE1 is VREF1 / R, the current (VREF2 / R) of the third linear constant current module SOURCE3 is greater than the current of the first linear constant current module SOURCE1, the third linear constant current module SOURCE3 operates in the switch-on mode, and the current flowing through the first LED load LED1s is VREF1 / R; when the bus voltage is higher than the set voltage, the current of the third linear constant current module SOURCE3 is VREF1 / R.

[0109] In some alternative implementations, the second constant current source includes a second operational amplifier OP2 and a second MOSFET;

[0110] The first terminal of the second linear compensation module LN2 is connected to the first input terminal of the comparator COMP. The second terminal of the second linear compensation module LN2 is connected to the drain of the second MOSFET. The third terminal of the second linear compensation module LN2 is connected to the positive input terminal of the second operational amplifier OP2. The positive input terminal of the second operational amplifier OP2 is also connected to the first power supply VREF1. The negative input terminal of the second operational amplifier OP2 is connected to the source of the second MOSFET. The source of the second MOSFET is connected to the negative terminal of the external power supply through the second resistor RCS2. The drain of the second MOSFET is also connected to the second terminal of the first LED load LED1s.

[0111] In some alternative implementations, the first constant current source includes a first operational amplifier OP1 and a first MOSFET;

[0112] The first terminal of the first linear compensation module LN1 is connected to the drain of the first MOSFET. The second terminal of the first linear compensation module LN1 is connected to the positive input terminal of the first operational amplifier OP1. The positive input terminal of the first operational amplifier OP1 is also connected to the first power supply VREF1. The negative input terminal of the first operational amplifier OP1 is connected to the source of the first MOSFET. The drain of the first MOSFET is also connected to the first terminal of the first LED load LED1s. The source of the first MOSFET is also connected to the first terminal of the second LED load LED2s through the first resistor RCS1.

[0113] In some optional implementations, a diode D1 is also included;

[0114] The drain of the first LED load LED1s and the second operational amplifier OP2 is connected to point A. Point A is connected to the input terminal of diode D1. The output terminal of diode D1 is connected to point B. Point B is connected to the first terminal of the second LED load LED2s and the first resistor RCS1.

[0115] The resistance values ​​of the first resistor RCS1, the second resistor RCS2, and the third resistor RCS3 are all R.

[0116] In some alternative implementations, a rectifier DB is also included;

[0117] The positive terminal of the external AC power supply is connected to the positive input terminal of the rectifier DB, and the negative terminal of the external AC power supply is connected to the negative input terminal of the rectifier DB. The positive output terminal of the rectifier DB is connected to the first terminal of the first LED load LED1s, and the negative output terminal of the rectifier DB is connected to the second linear constant current module SOURCE2 and the third linear constant current module SOURCE3.

[0118] This application provides an LED linear driver chip, comprising: an LED linear driver circuit as described in any of the above claims, a lead frame, and a molding compound; the LED linear driver circuit is disposed on the lead frame, and the molding compound is used to seal the LED linear driver circuit.

[0119] An LED device provided in this application includes a first LED load LED1s, a second LED load LED2s, and an LED linear driving circuit as described in any of the above.

[0120] In the embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. The apparatus embodiments described above are merely illustrative. For example, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. Furthermore, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Additionally, the displayed or discussed mutual couplings, direct couplings, or communication connections may be through some communication interfaces; indirect couplings or communication connections between devices or units may be electrical, mechanical, or other forms.

[0121] Furthermore, the units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0122] Furthermore, the functional modules in the various embodiments of this application can be integrated together to form an independent part, or each module can exist independently, or two or more modules can be integrated to form an independent part.

[0123] In this document, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, without necessarily requiring or implying any such actual relationship or order between these entities or operations.

[0124] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. An LED linear driving circuit, characterized in that, include: Series-to-parallel conversion circuit module and series-to-parallel control module; Both the series-parallel conversion circuit module and the series-parallel control module are connected to an external power source and are powered by the external power input line. The series-parallel conversion circuit module includes a first LED load and a second LED load; The series-parallel control module is used to switch the series-parallel connection state between the first LED load and the second LED load in the series-parallel conversion circuit module, and during the series-parallel connection state switching process, the current of the first LED load and the second LED load is greater than or equal to Is; where Is is the defined minimum operating current.

2. The LED linear driving circuit of claim 1, wherein, When the bus voltage reaches the switching threshold, the series-parallel control module switches the series-parallel connection state between the first LED load and the second LED load. When the bus voltage is greater than the load voltage but less than the switching threshold, the first LED load and the second LED load are connected in parallel; when the bus voltage is greater than the switching threshold, the first LED load and the second LED load are connected in series; during the period when the bus voltage is greater than the load voltage, the current of both the first LED load and the second LED load is greater than or equal to Is.

3. The LED linear driving circuit of claim 1, wherein, The series-parallel control module includes a first linear constant current module, a second linear constant current module, and a third linear constant current module; The external power supply positive terminal, the first LED load, the first diode, the second LED load, the third linear constant current module, and the external power supply negative terminal are connected in sequence; one end of the first linear constant current module is connected to the positive terminal of the first LED load, and the other end is connected to the positive terminal of the second LED load; one end of the second linear constant current module is connected to the negative terminal of the first LED load, and the other end is connected to the negative terminal of the external power supply.

4. The LED linear driving circuit as described in claim 3, characterized in that, The first linear constant current module is used to provide current I1 to the second LED load, and the second linear constant current module is used to provide current I2 to the first LED load; when the bus voltage is higher than the load voltage and the bus voltage is lower than the switching threshold, the first LED load and the second LED load are connected in parallel, and I1 and I2 are both greater than or equal to Is; The third linear constant current module is used to provide I3 power supply when the bus voltage is higher than the switching threshold. At this time, the first LED load and the second LED load are connected in series, (I1+I3)≥Is and (I2+I3)≥Is; when the bus voltage is lower than the switching threshold, it operates in the switch-on mode.

5. The LED linear driving circuit of claim 3, wherein, The first linear constant current module includes a first linear compensation module and a first constant current source, and the second linear constant current module includes a second linear compensation module and a second constant current source; When the bus voltage is greater than the line compensation intervention threshold, the first linear compensation module intervenes, causing the output current I1 of the first constant current source to decrease as the bus voltage increases; the second linear compensation module intervenes, causing the output current I2 of the second constant current source to decrease as the bus voltage increases. During this process, by controlling the intervention timing and line compensation slope of the first and second linear compensation modules, I1 and I2 are both controlled to be greater than or equal to Is; wherein, the line compensation intervention threshold is greater than the load voltage.

6. The LED linear driving circuit of claim 5, wherein, Both the first linear compensation module and the second linear compensation module include: an input AC voltage sampling module, a line compensation starting point design module, and a line compensation slope design module connected in sequence; The input AC voltage sampling module is used to obtain the sampled voltage of the bus voltage; The line compensation starting point design module is used to obtain the intervention timing; The line compensation slope design module is used to obtain the line compensation slope based on the bus voltage and the timing of intervention.

7. The LED linear driving circuit as described in claim 5, characterized in that, It also includes a comparator; wherein the output terminal of the comparator is connected to the third terminal of the third linear constant current module; the first input terminal of the comparator is connected to the second linear compensation module; and the second input terminal of the comparator is connected to a reference voltage. The comparator outputs a high-level signal to the third linear constant current module when the bus voltage is higher than the switching threshold, and outputs a low-level signal to the third linear constant current module when the bus voltage is lower than the switching threshold.

8. The LED linear driving circuit of claim 7, wherein, The third linear constant current module includes: a switch, a third operational amplifier, and a third MOSFET; wherein, the control terminal of the switch is connected to the output terminal of the comparator, the fixed terminal of the switch is connected to the positive input terminal of the third operational amplifier, the negative input terminal of the third operational amplifier is connected to the source of the third MOSFET, the output terminal of the third operational amplifier is connected to the gate of the third MOSFET, the drain of the third MOSFET is connected to the second terminal of the second LED load, and the source of the third MOSFET is connected to the negative terminal of an external power supply through a third resistor; the first contact terminal of the switch is connected to a first power supply, and the second contact terminal of the switch is connected to a second power supply; The switch is used to: connect the positive input terminal of the third operational amplifier to a first power supply according to a high-level signal received at its control terminal; and connect the positive input terminal of the third operational amplifier to a second power supply according to a low-level signal received at its control terminal; wherein the voltage VREF2 of the second power supply is greater than the voltage VREF1 of the first power supply.

9. The LED linear driving circuit of claim 8, wherein, The second constant current source includes a second operational amplifier and a second MOSFET; wherein, the first terminal of the second linear compensation module is connected to the first input terminal of the comparator, the second terminal of the second linear compensation module is connected to the drain of the second MOSFET, the third terminal of the second linear compensation module is connected to the positive input terminal of the second operational amplifier, the positive input terminal of the second operational amplifier is also connected to a first power supply; the negative input terminal of the second operational amplifier is connected to the source of the second MOSFET, the source of the second MOSFET is connected to the negative terminal of an external power supply through a second resistor; the drain of the second MOSFET is also connected to the second terminal of the first LED load.

10. The LED linear driving circuit of claim 9, wherein, The first constant current source includes a first operational amplifier and a first MOSFET; wherein, the first terminal of the first linear compensation module is connected to the drain of the first MOSFET, the second terminal of the first linear compensation module is connected to the positive input terminal of the first operational amplifier, the positive input terminal of the first operational amplifier is also connected to a first power supply; the negative input terminal of the first operational amplifier is connected to the source of the first MOSFET, the drain of the first MOSFET is also connected to the first terminal of the first LED load, and the source of the first MOSFET is also connected to the first terminal of the second LED load through a first resistor.

11. An LED linear driving chip, characterized in that, include: An LED linear driving circuit, a lead frame, and a molding compound as described in any one of claims 1-10; The LED linear driving circuit is disposed on the lead frame, and the molding compound is used to seal the LED linear driving circuit.

12. An LED device, comprising: It includes a first LED load, a second LED load, and an LED linear drive circuit as described in any one of claims 1-10.

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