CN108055728B - Multi-path light-emitting diode (LED) driving circuit and driving method - Google Patents

Multi-path light-emitting diode (LED) driving circuit and driving method Download PDF

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CN108055728B
CN108055728B CN201711446944.1A CN201711446944A CN108055728B CN 108055728 B CN108055728 B CN 108055728B CN 201711446944 A CN201711446944 A CN 201711446944A CN 108055728 B CN108055728 B CN 108055728B
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led
voltage
led branch
circuit
branch
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CN108055728A (en
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楼俊山
沈锦祥
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Sengled Co Ltd
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Sengled Co Ltd
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]

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Abstract

The invention provides a multipath LED driving circuit and a driving method, wherein the multipath LED driving circuit comprises: the LED lamp comprises a constant voltage power supply, at least one first LED branch, at least one second LED branch and a positive voltage source corresponding to each second LED branch; the voltage drop of the first LED branch is smaller than a preset threshold value; the voltage drop of the second LED branch is larger than a preset threshold value; the positive electrode of the constant voltage power supply is respectively connected with the input end of the first LED branch and the negative electrode of the positive voltage source; the cathode of the constant voltage power supply is grounded; the output end of the first LED branch is grounded; the positive pole of the positive voltage source is connected with the input end of the second LED branch, the output end of the second LED branch is grounded, and the positive voltage source is used for providing compensation voltage for the second LED branch. According to the multi-path light-emitting diode (LED) driving circuit and the driving method, normal operation of the LED branch with smaller pressure drop is realized while power consumption of the LED branch with larger pressure drop is not influenced, and the driving effect of the multi-path LEDs is improved.

Description

Multi-path light-emitting diode (LED) driving circuit and driving method
Technical Field
The invention relates to the technical field of LEDs, in particular to a multi-path light emitting diode LED driving circuit and a driving method.
Background
The light-emitting diode (Light Emitting Diode, LED for short) lamp has the advantages of long service life, high light efficiency, impact resistance, low energy consumption and the like, belongs to green energy-saving and environment-friendly illumination, and is widely applied to the fields of illumination and decoration. For example, multiple LEDs may implement different color temperature beads.
For multiple LEDs, a Direct Current-Direct Current (DC-DC) constant voltage power supply and an equivalent output capacitor are generally used to drive the multiple LEDs. Taking the case that the multi-path LED comprises a first LED branch and a second LED branch, if the voltage of the first LED branch is larger than that of the second LED branch, and the first LED branch and the second LED branch are alternately conducted, when the first LED branch is conducted, the instantaneous voltage of the equivalent output capacitor is the voltage of the first LED branch, and a larger voltage is provided for the first LED branch, when the first LED branch is switched to the second LED branch, because the voltage of the second LED branch is smaller than that of the first LED branch, when the voltage is provided for the second LED branch through the instantaneous voltage of the equivalent output capacitor, the voltage overshoot exists, and the phenomenon of overlarge current in the second LED branch occurs, and in the process, the instantaneous voltage of the equivalent output capacitor becomes the voltage of the second LED branch; when the second LED branch is switched to the first LED branch, the voltage of the first LED branch is larger than that of the second LED branch, so that the voltage is insufficient and the current in the first LED branch rises slowly when the voltage is provided for the first LED branch through the instantaneous voltage of the equivalent output capacitor.
Therefore, the existing multi-path LED driving mode is adopted, so that the driving effect of the multi-path LEDs is poor.
Disclosure of Invention
The invention provides a multi-path light-emitting diode (LED) driving circuit and a driving method, which can realize normal operation of an LED branch with smaller voltage drop while not influencing power consumption of the LED branch with larger voltage drop so as to improve the driving effect of the multi-path LEDs.
The embodiment of the invention provides a multi-path Light Emitting Diode (LED) driving circuit, which comprises:
the LED driving circuit comprises a constant voltage power supply, a driving sub-circuit, an equivalent output capacitor, a first LED branch and a second LED branch, wherein the voltage of the first LED branch is larger than that of the second LED branch, and the second LED branch comprises a first booster circuit;
the first end and the second end of the constant voltage power supply are respectively connected with the first end and the second end of the driving sub-circuit, and the third end of the driving sub-circuit is respectively connected with the first end of the equivalent output capacitor, the first end of the first LED branch circuit and the first end of the second LED branch circuit; the fourth end of the driving sub-circuit is respectively connected with the second end of the equivalent output capacitor, the second end of the first LED branch and the second end of the second LED branch;
the first boost circuit is used for compensating the voltage of the second LED branch so that the voltage of the second LED branch and the voltage of the first LED branch meet a preset threshold.
In an embodiment of the invention, the first LED branch also comprises a second boost circuit, which is not operative.
In an embodiment of the present invention, the boosting circuit is a semiconductor field effect transistor, and the LED driving circuit further includes a sample hold circuit and an error amplifying circuit;
the first LED branch comprises a first LED and a first semiconductor field effect transistor, the second LED branch comprises a second LED and a second semiconductor field effect transistor, the input end of the first LED is connected with the first end of the equivalent output capacitor, the output end of the first LED is connected with the first end of the first semiconductor field effect transistor, the second end of the first semiconductor field effect transistor is connected with the second end of the equivalent output capacitor, and the third end of the first semiconductor field effect transistor is input with a first pulse width modulation PWM signal; the input end of the second LED is connected with the first end of the equivalent output capacitor, the output end of the second LED is connected with the first end of the second semiconductor field effect transistor, the second end of the second semiconductor field effect transistor is connected with the second end of the equivalent output capacitor, the third end of the second semiconductor field effect transistor is connected with the output end of the error amplifying circuit, the first input end of the error amplifying circuit is connected with the sample hold circuit, and the second input end of the error amplifying circuit inputs reference voltage or reference current;
the sampling hold circuit is used for collecting preset current and inputting the preset current to the error amplifying circuit; the error amplifying circuit is used for outputting a second PWM signal according to a preset current so as to control the second semiconductor field effect transistor to compensate the voltage of the second LED branch through the second PWM signal.
In an embodiment of the invention, the first LED branch further comprises a first switch, and the second LED branch further comprises a second switch;
the first end of the first switch is connected with the second end of the first semiconductor field effect transistor, and the second end of the first switch is connected with the second end of the equivalent output capacitor;
the second end of the second switch is connected with the second end of the second semiconductor field effect transistor, and the second end of the second switch is connected with the second end of the equivalent output capacitor.
In an embodiment of the invention, the multi-path light emitting diode LED driving circuit further includes a third switch;
the first end of the third switch is connected with the error amplifying circuit, and the second end of the third switch is connected with the third end of the second semiconductor field effect transistor.
The embodiment of the invention also provides a method for driving the multi-path Light Emitting Diode (LED), which comprises the following steps:
when the voltage of the first LED branch is larger than that of the second LED branch, the voltage of the second LED branch is compensated through a first voltage boosting circuit in the second LED branch, so that the voltage of the second LED branch and the voltage of the first LED branch meet a preset threshold.
In an embodiment of the present invention, before the compensating the voltage of the second LED branch by the first boosting circuit, the method further includes:
determining that the voltage of the first LED branch is greater than the voltage of the second LED branch.
In an embodiment of the present invention, the first LED branch includes a first LED, the second LED branch includes a second LED, and the determining that the voltage of the first LED branch is greater than the voltage of the second LED branch includes:
detecting the current of the first LED when the first LED branch is on and the second LED branch is off;
detecting the current of the second LED when the second LED branch is on and the first LED branch is off;
and if the current of the first LED is smaller than the current of the second LED, determining that the voltage of the first LED branch is larger than the voltage of the second LED branch.
In an embodiment of the present invention, the first LED branch further includes a second boost circuit, and the determining that the voltage of the first LED branch is greater than the voltage of the second LED branch includes:
in a preset time period, the first LED branch circuit and the second LED branch circuit are conducted, and the current of the first LED or the voltage at the second booster circuit and the current of the second LED or the voltage at the first booster circuit in the preset time period are obtained;
and if the current of the first LED is smaller than the current of the second LED or the voltage at the second voltage boosting circuit is smaller than the voltage at the first voltage boosting circuit, determining that the voltage of the first LED branch is larger than the voltage of the second LED branch.
In an embodiment of the present invention, the compensating the voltage of the second LED branch by the first boosting circuit in the second LED branch includes:
detecting peak current of the second LED branch when the second LED branch is conducted; controlling the first booster circuit to compensate the voltage of the second LED branch according to the peak current and the reference current of the second LED branch;
or alternatively;
acquiring average current of the first LED branch in a time period when the first LED branch is conducted and the second LED branch is disconnected; acquiring average current of the second LED branch in a time period when the second LED branch is conducted and the first LED branch is disconnected; and controlling the first booster circuit to compensate the voltage of the second LED branch according to the average current of the first LED branch and the reference current or according to the average current of the second LED branch and the reference current.
The multi-path Light Emitting Diode (LED) driving circuit and the driving method provided by the embodiment of the invention comprise the following steps: the LED driving circuit comprises a constant voltage power supply, a driving sub-circuit, an equivalent output capacitor, a first LED branch and a second LED branch, wherein the voltage of the first LED branch is greater than that of the second LED branch, and the second LED branch comprises a first booster circuit; the first end and the second end of the constant voltage power supply are respectively connected with the first end and the second end of the driving sub-circuit, and the third end of the driving sub-circuit is respectively connected with the first end of the equivalent output capacitor, the first end of the first LED branch circuit and the first end of the second LED branch circuit; the fourth end of the driving sub-circuit is respectively connected with the second end of the equivalent output capacitor, the second end of the first LED branch and the second end of the second LED branch; the first boost circuit is used for compensating the voltage of the second LED branch so that the voltage of the second LED branch and the voltage of the first LED branch meet a preset threshold. Therefore, in the embodiment of the invention, the first voltage boosting circuit is arranged in the second LED branch circuit with lower voltage, so that the voltage of the second LED branch circuit can be supplemented by the first voltage boosting circuit, and the voltage of the second LED branch circuit is equal or approximately equal to the voltage of the first LED branch circuit, thereby avoiding the phenomenon of overlarge current or slow current rising when the first LED branch circuit and the second LED branch circuit are switched, realizing the normal operation of the LED branch circuit with smaller voltage drop while not influencing the power consumption of the LED branch circuit with larger voltage drop, and further improving the driving effect of the multi-path LEDs.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions of the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings may be obtained according to the drawings without inventive effort to a person skilled in the art.
Fig. 1 is a schematic structural diagram of a multi-path LED driving circuit according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of determining that the voltage of the first LED branch is greater than the voltage of the second LED branch according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of another embodiment of the present invention for determining that the voltage of the first LED branch is greater than the voltage of the second LED branch;
fig. 4 is a schematic structural diagram of another LED driving circuit with multiple light emitting diodes according to an embodiment of the present invention;
fig. 5 is a schematic structural diagram of another LED driving circuit with multiple light emitting diodes according to an embodiment of the present invention;
fig. 6 is a schematic structural diagram of another LED driving circuit with multiple light emitting diodes according to an embodiment of the present invention;
fig. 7 is a schematic structural diagram of another LED driving circuit with multiple light emitting diodes according to an embodiment of the present invention;
fig. 8 is a schematic diagram of a method for driving multiple light emitting diodes according to an embodiment of the present invention.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The terms "first," "second," "third," "fourth" and the like in the description and in the claims and in the above drawings, if any, are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged where appropriate such that the embodiments of the invention described herein may be implemented, for example, in sequences other than those illustrated or otherwise described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
It should be noted that the following embodiments may be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments.
Fig. 1 is a schematic structural diagram of a multi-path LED driving circuit according to an embodiment of the present invention, however, the embodiment of the present invention is only illustrated by taking fig. 1 as an example, but the present invention is not limited thereto. Referring to fig. 1, the LED driving circuit may include:
the LED driving circuit comprises a constant voltage power supply, a driving sub-circuit, an equivalent output capacitor, a first LED branch and a second LED branch, wherein the voltage of the first LED branch is larger than that of the second LED branch, and the second LED branch comprises a first booster circuit.
The first end and the second end of the constant voltage power supply are respectively connected with the first end and the second end of the driving sub-circuit, and the third end of the driving sub-circuit is respectively connected with the first end of the equivalent output capacitor, the first end of the first LED branch circuit and the first end of the second LED branch circuit; the fourth end of the driving sub-circuit is respectively connected with the second end of the equivalent output capacitor, the second end of the first LED branch and the second end of the second LED branch.
The first boost circuit is used for compensating the voltage of the second LED branch so that the voltage of the second LED branch and the voltage of the first LED branch meet a preset threshold.
The preset threshold value can be set according to actual needs, so long as the voltage of the second LED branch is equal to or approximately equal to the voltage of the first LED branch.
Therefore, in the embodiment of the invention, the first voltage boosting circuit is arranged in the second LED branch circuit with lower voltage, so that the voltage of the second LED branch circuit can be supplemented by the first voltage boosting circuit, and the voltage of the second LED branch circuit is equal or approximately equal to the voltage of the first LED branch circuit, thereby avoiding the phenomenon of overlarge current or slow current rising when the first LED branch circuit and the second LED branch circuit are switched, realizing the normal operation of the LED branch circuit with smaller voltage drop while not influencing the power consumption of the LED branch circuit with larger voltage drop, and further improving the driving effect of the multi-path LEDs.
The multi-path Light Emitting Diode (LED) driving circuit provided by the embodiment of the invention comprises: the LED driving circuit comprises a constant voltage power supply, a driving sub-circuit, an equivalent output capacitor, a first LED branch and a second LED branch, wherein the voltage of the first LED branch is greater than that of the second LED branch, and the second LED branch comprises a first booster circuit; the first end and the second end of the constant voltage power supply are respectively connected with the first end and the second end of the driving sub-circuit, and the third end of the driving sub-circuit is respectively connected with the first end of the equivalent output capacitor, the first end of the first LED branch circuit and the first end of the second LED branch circuit; the fourth end of the driving sub-circuit is respectively connected with the second end of the equivalent output capacitor, the second end of the first LED branch and the second end of the second LED branch; the first boost circuit is used for compensating the voltage of the second LED branch so that the voltage of the second LED branch and the voltage of the first LED branch meet a preset threshold. Therefore, in the embodiment of the invention, the first voltage boosting circuit is arranged in the second LED branch circuit with lower voltage, so that the voltage of the second LED branch circuit can be supplemented by the first voltage boosting circuit, and the voltage of the second LED branch circuit is equal or approximately equal to the voltage of the first LED branch circuit, thereby avoiding the phenomenon of overlarge current or slow current rising when the first LED branch circuit and the second LED branch circuit are switched, realizing the normal operation of the LED branch circuit with smaller voltage drop while not influencing the power consumption of the LED branch circuit with larger voltage drop, and further improving the driving effect of the multi-path LEDs.
It should be noted that, in the technical solution shown in the foregoing embodiment, it is predetermined that the voltage of the first LED branch is greater than the voltage of the second LED branch, and if the voltage of the first LED branch and the voltage of the second LED branch cannot be determined in advance, a first voltage boosting circuit needs to be set in the second LED branch, and a second voltage boosting circuit needs to be set in the first LED branch, that is, when the voltage values of the branches are not determined, a voltage boosting circuit needs to be set in each branch. After an increasing voltage is set in each branch, the voltage of the first LED branch and the voltage of the second LED branch can be compared to determine the branch with smaller voltage, so that the booster circuit in the branch with smaller voltage works to compensate the branch with smaller voltage, and the booster circuit in the branch with larger voltage does not work. Alternatively, when it is determined that the voltage of the first LED branch is greater than the voltage of the second LED branch, this may be achieved by two possible ways:
in a first possible implementation, when the first LED branch is on and the second LED branch is off, detecting a current of the first LED in the first LED branch; detecting the current of a second LED in the second LED branch when the second LED branch is on and the first LED branch is off; and if the current of the first LED is smaller than that of the second LED, determining that the voltage of the first LED branch is larger than that of the second LED branch.
Specifically, when the LED branches are switched, overshoot current exists in the low-voltage second LED branch at the moment when the first high-voltage LED branch is disconnected and the second low-voltage LED branch is conducted; at the moment when the second LED branch circuit with low voltage is disconnected and the first LED branch circuit with high voltage is conducted, the current in the first LED branch circuit with high voltage can slowly rise, the maximum values of the currents of the two branch circuits are compared, and if the maximum current max1 of the first LED is smaller than the maximum current max2 of the second LED, it can be determined that the voltage of the first LED branch circuit is larger than the voltage of the second LED branch circuit. Referring to fig. 2, fig. 2 is a schematic diagram of determining that the voltage of the first LED branch is greater than the voltage of the second LED branch according to an embodiment of the invention.
In a second possible implementation manner, in a preset time period, the first LED branch and the second LED branch are conducted, and the current of the first LED or the voltage at the second booster circuit and the current of the second LED or the voltage at the first booster circuit in the preset time period are obtained; if the current of the first LED is smaller than the current of the second LED or the voltage at the second boosting circuit is smaller than the voltage at the first boosting circuit, determining that the voltage of the first LED branch is larger than the voltage of the second LED branch.
The preset time period may be any value from 100ms to 200ms, and specifically may be set according to actual needs, so long as the user experience is not affected.
Specifically, when the first LED branch and the second LED branch are turned on in a preset time period, and then enter a normal PWM operation mode, in the preset time period, the first boost circuit and the second boost circuit do not work, and the currents flowing through the first LED branch and the second LED branch are direct currents, so that the current sizes of the first LED branch and the second LED branch can be directly compared, the voltage K1 at the first boost circuit and the voltage K2 at the second boost circuit can be compared, or the voltage K3 at the first boost circuit and the voltage K4 at the second boost circuit can be compared, because the impedance of K1 and K2 to ground is the same, the impedance of K3 and K4 to ground is the same, and if the current of the first LED branch is smaller than the current of the second LED branch, or the voltage K1 at the first boost circuit is smaller than the voltage K2 at the second boost circuit, or the voltage K3 at the first boost circuit is smaller than the voltage K4 at the second boost circuit, then the voltage of the first LED branch can be determined. Referring to fig. 3, fig. 3 is a schematic diagram of another embodiment of determining that the voltage of the first LED branch is greater than the voltage of the second LED branch.
After determining that the voltage of the first LED branch is greater than the voltage of the second LED branch through two possible implementations, the first booster circuit of the second LED branch may be controlled to operate, and the second booster circuit of the first LED branch may operate, for example, as shown in fig. 4, fig. 4 is a schematic structural diagram of another multi-path LED driving circuit according to an embodiment of the present invention.
The boosting circuit is a semiconductor field effect transistor, and the LED driving circuit further comprises a sample hold circuit and an error amplifying circuit.
The first LED branch comprises a first LED and a first semiconductor field effect transistor, the second LED branch comprises a second LED and a second semiconductor field effect transistor, the input end of the first LED is connected with the first end of the equivalent output capacitor, the output end of the first LED is connected with the first end of the first semiconductor field effect transistor, the second end of the first semiconductor field effect transistor is connected with the second end of the equivalent output capacitor, and the third end of the first semiconductor field effect transistor is input with a first pulse width modulation PWM signal; the input end of the second LED is connected with the first end of the equivalent output capacitor, the output end of the second LED is connected with the first end of the second semiconductor field effect transistor, the second end of the second semiconductor field effect transistor is connected with the second end of the equivalent output capacitor, the third end of the second semiconductor field effect transistor is connected with the output end of the error amplifying circuit, the first input end of the error amplifying circuit is connected with the sample hold circuit, and the second input end of the error amplifying circuit inputs the reference current.
The sampling hold circuit is used for collecting preset current and inputting the preset current to the error amplifying circuit; the error amplifying circuit is used for outputting a second PWM signal according to the preset current so as to control the second semiconductor field effect transistor to compensate the voltage of the second LED branch through the second PWM signal.
Optionally, the multi-path light emitting diode LED driving circuit may further include a third switch; the first end of the third switch is connected with the error amplifying circuit, and the second end of the third switch is connected with the third end of the second semiconductor field effect transistor.
For example, when the voltage of the second LED branch is compensated by the second semiconductor field effect transistor, the first semiconductor field effect transistor may also be controlled by the first PWM signal, the second PWM signal at the output end of the error amplifying circuit may control the second semiconductor field effect transistor by the third switch, when the second PWM signal at the output end of the error amplifying circuit is a high current signal, the third switch is turned on, and when the second PWM signal at the output end of the error amplifying circuit is a low current signal, the third switch is turned off, so that the voltage of the second LED branch is compensated by the second semiconductor field effect transistor.
In the embodiment of the present invention, the boost circuit is only described by taking the boost circuit as the semiconductor field effect transistor as an example, and of course, the boost circuit may also be a triode, and may be specifically set according to actual needs.
Further, collecting a preset current through a sample hold circuit and inputting the preset current to an error amplifying circuit; the error amplifying circuit outputs a second PWM signal according to a preset current, so that when the second PWM signal controls the second semiconductor field effect transistor to compensate the voltage of the second LED branch, the preset current may be a peak current of the second LED branch, an average current of the first LED branch or an average current of the second LED branch, the corresponding first LED branch further includes a first switch, the second LED branch further includes a second switch, and fig. 5 is a schematic structural diagram of another multi-path LED driving circuit provided in the embodiment of the present invention.
The first end of the first switch is connected with the second end of the first semiconductor field effect transistor, and the second end of the first switch is connected with the second end of the equivalent output capacitor.
The second end of the second switch is connected with the second end of the second semiconductor field effect transistor, and the second end of the second switch is connected with the second end of the equivalent output capacitor.
In a first possible implementation manner, when the preset current may be the peak current of the second LED branch, as shown in fig. 6, fig. 6 is a schematic structural diagram of another multi-path LED driving circuit according to an embodiment of the present invention. The control electrode of the first semiconductor field effect transistor is arranged to be high, so that the first semiconductor field effect transistor works in a switching area, the second booster circuit of the first LED branch does not work, the control electrode of the second semiconductor field effect transistor is controlled by a second PWM signal and works in a linear area, and the current of the second LED enters an error amplifying circuit together with a reference current through a sample and hold circuit (for example, a peak sample and hold unit) to be compared, so that the voltage of the second LED branch is compensated through the second semiconductor field effect transistor, so that the voltage of the second LED branch is equal to or approximately equal to the voltage of the first LED branch, the phenomenon of overlarge current or slow current rising is avoided when the first LED branch and the second LED branch are switched, the normal work of the LED branch with smaller voltage drop is realized while the power consumption of the LED branch with larger voltage drop is not influenced, and the driving effect of a plurality of LEDs is improved. Wherein the value of the reference current may be a value proportional to the single stage circuit output current.
In a second possible implementation manner, when the preset current may be the average current of the first LED branch or the average current of the second LED branch, please refer to fig. 7, fig. 7 is a schematic diagram of a structure of another multi-path LED driving circuit according to an embodiment of the present invention. The control electrode of the first semiconductor field effect transistor is arranged to be high, the control electrode of the first semiconductor field effect transistor works in a switching area, the second booster circuit of the first LED branch is not operated, the control electrode of the second semiconductor field effect transistor is controlled by the second PWM signal and works in a linear area, the average current value of the first LED branch and the average current value of the second LED branch can be obtained through a sample and hold circuit (an average value sample holder in an example), the average current of any LED branch and the reference current are input into an error amplifying circuit together for comparison, and the voltage of the second LED branch is compensated through the second semiconductor field effect transistor, so that the voltage of the second LED branch is equal to or approximately equal to the voltage of the first LED branch, the phenomenon of overlarge current or slow current rising is avoided when the first LED branch and the second LED branch are switched, the power consumption of the LED branch with larger voltage drop is not influenced, the normal operation of the LED branch with smaller voltage drop is realized, and the driving effect of the multiple LEDs is improved. Wherein the value of the reference current may be a value proportional to the single stage circuit output current.
After describing the multi-path LED driving circuit according to the above embodiment, further, a method of the multi-path LED driving circuit may be described, referring to fig. 8, fig. 8 is a schematic diagram of a multi-path LED driving method according to an embodiment of the present invention, where the multi-path LED driving method may include:
s101, when the voltage of the first LED branch is larger than that of the second LED branch, the voltage of the second LED branch is compensated through a first voltage boosting circuit in the second LED branch, so that the voltage of the second LED branch and the voltage of the first LED branch meet a preset threshold.
Optionally, before the voltage of the second LED branch is compensated by the first boost circuit, the method further includes:
s100, determining that the voltage of the first LED branch is larger than that of the second LED branch.
It should be noted that, in the embodiment of the present invention, the preset determination that the voltage of the first LED branch is greater than the voltage of the second LED branch may be implemented in the following two possible ways:
optionally, in a first possible implementation, the first LED branch includes a first LED, the second LED branch includes a second LED, and determining, in S100, that the voltage of the first LED branch is greater than the voltage of the second LED branch may include:
and detecting the current of the first LED when the first LED branch is on and the second LED branch is off.
And detecting the current of the second LED when the second LED branch is on and the first LED branch is off.
And if the current of the first LED is smaller than that of the second LED, determining that the voltage of the first LED branch is larger than that of the second LED branch.
Optionally, in a second possible implementation manner, the first LED branch further includes a second boost circuit, and S100 determines that the voltage of the first LED branch is greater than the voltage of the second LED branch may include:
and in a preset time period, the first LED branch circuit and the second LED branch circuit are conducted, and the current of the first LED or the voltage at the second voltage boosting circuit and the current of the second LED or the voltage at the first voltage boosting circuit in the preset time period are obtained.
If the current of the first LED is smaller than the current of the second LED or the voltage at the second boosting circuit is smaller than the voltage at the first boosting circuit, determining that the voltage of the first LED branch is larger than the voltage of the second LED branch.
Optionally, compensating the voltage of the second LED branch by the first boost circuit in the second LED branch includes:
detecting peak current of the second LED branch when the second LED branch is conducted; and controlling the first voltage boosting circuit to compensate the voltage of the second LED branch according to the peak current and the reference current of the second LED branch.
Or alternatively;
acquiring average current of the first LED branch in a time period when the first LED branch is on and the second LED branch is off; acquiring average current of the second LED branch in a time period when the second LED branch is conducted and the first LED branch is disconnected; the first boost circuit is controlled to compensate the voltage of the second LED branch according to the average current and the reference current of the first LED branch or according to the average current and the reference current of the second LED branch.
The above method for driving multiple light emitting diodes LEDs is correspondingly applicable to the technical scheme of the multiple light emitting diode LED driving circuit in any embodiment, and its implementation principle and technical effect are similar, and will not be described herein again.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.

Claims (9)

1. A multi-channel light emitting diode, LED, drive circuit comprising:
the LED driving circuit comprises a constant voltage power supply, a driving sub-circuit, an equivalent output capacitor, a first LED branch and a second LED branch, wherein the voltage of the first LED branch is larger than that of the second LED branch, and the second LED branch comprises a first booster circuit;
the first end and the second end of the constant voltage power supply are respectively connected with the first end and the second end of the driving sub-circuit, and the third end of the driving sub-circuit is respectively connected with the first end of the equivalent output capacitor, the first end of the first LED branch circuit and the first end of the second LED branch circuit; the fourth end of the driving sub-circuit is respectively connected with the second end of the equivalent output capacitor, the second end of the first LED branch and the second end of the second LED branch;
the first voltage boosting circuit is used for compensating the voltage of the second LED branch so that the voltage of the second LED branch and the voltage of the first LED branch meet a preset threshold;
the boosting circuit is a semiconductor field effect transistor, and the LED driving circuit further comprises a sample hold circuit and an error amplifying circuit;
the first LED branch comprises a first LED and a first semiconductor field effect transistor, the second LED branch comprises a second LED and a second semiconductor field effect transistor, the input end of the first LED is connected with the first end of the equivalent output capacitor, the output end of the first LED is connected with the first end of the first semiconductor field effect transistor, the second end of the first semiconductor field effect transistor is connected with the second end of the equivalent output capacitor, and the third end of the first semiconductor field effect transistor is input with a first pulse width modulation PWM signal; the input end of the second LED is connected with the first end of the equivalent output capacitor, the output end of the second LED is connected with the first end of the second semiconductor field effect transistor, the second end of the second semiconductor field effect transistor is connected with the second end of the equivalent output capacitor, the third end of the second semiconductor field effect transistor is connected with the output end of the error amplifying circuit, the first input end of the error amplifying circuit is connected with the sample hold circuit, and the second input end of the error amplifying circuit inputs reference voltage or reference current;
the sampling hold circuit is used for collecting preset current and inputting the preset current to the error amplifying circuit; the error amplifying circuit is used for outputting a second PWM signal according to a preset current so as to control the second semiconductor field effect transistor to compensate the voltage of the second LED branch through the second PWM signal.
2. The circuit of claim 1, wherein the circuit comprises a plurality of capacitors,
the first LED branch also includes a second boost circuit, which is inactive.
3. The circuit of claim 2, wherein the first LED leg further comprises a first switch and the second LED leg further comprises a second switch;
the first end of the first switch is connected with the second end of the first semiconductor field effect transistor, and the second end of the first switch is connected with the second end of the equivalent output capacitor;
the second end of the second switch is connected with the second end of the second semiconductor field effect transistor, and the second end of the second switch is connected with the second end of the equivalent output capacitor.
4. The circuit of claim 3, further comprising a third switch;
the first end of the third switch is connected with the error amplifying circuit, and the second end of the third switch is connected with the third end of the second semiconductor field effect transistor.
5. A method for driving a multi-path light emitting diode LED, the method being applied to the multi-path light emitting diode LED driving circuit according to any one of claims 1 to 4, comprising:
when the voltage of the first LED branch is larger than that of the second LED branch, the voltage of the second LED branch is compensated through a first voltage boosting circuit in the second LED branch, so that the voltage of the second LED branch and the voltage of the first LED branch meet a preset threshold.
6. The method of claim 5, further comprising, prior to compensating the voltage of the second LED branch by the first boost circuit:
determining that the voltage of the first LED branch is greater than the voltage of the second LED branch.
7. The method of claim 6, wherein the first LED leg comprises a first LED and the second LED leg comprises a second LED leg, and wherein the determining that the voltage of the first LED leg is greater than the voltage of the second LED leg comprises:
detecting the current of the first LED when the first LED branch is on and the second LED branch is off;
detecting the current of the second LED when the second LED branch is on and the first LED branch is off;
and if the current of the first LED is smaller than the current of the second LED, determining that the voltage of the first LED branch is larger than the voltage of the second LED branch.
8. The method of claim 7, wherein the first LED leg further comprises a second boost circuit, and wherein the determining that the voltage of the first LED leg is greater than the voltage of the second LED leg comprises:
in a preset time period, the first LED branch circuit and the second LED branch circuit are conducted, and the current of the first LED or the voltage at the second booster circuit and the current of the second LED or the voltage at the first booster circuit in the preset time period are obtained;
and if the current of the first LED is smaller than the current of the second LED or the voltage at the second voltage boosting circuit is smaller than the voltage at the first voltage boosting circuit, determining that the voltage of the first LED branch is larger than the voltage of the second LED branch.
9. The method of any of claims 5-8, wherein the compensating the voltage of the second LED branch by the first boost circuit in the second LED branch comprises:
detecting peak current of the second LED branch when the second LED branch is conducted; controlling the first booster circuit to compensate the voltage of the second LED branch according to the peak current and the reference current of the second LED branch;
or alternatively;
acquiring average current of the first LED branch in a time period when the first LED branch is conducted and the second LED branch is disconnected; acquiring average current of the second LED branch in a time period when the second LED branch is conducted and the first LED branch is disconnected; and controlling the first booster circuit to compensate the voltage of the second LED branch according to the average current of the first LED branch and the reference current or according to the average current of the second LED branch and the reference current.
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