CN112399676A - Constant current driving circuit, calibration method thereof and lighting device - Google Patents

Constant current driving circuit, calibration method thereof and lighting device Download PDF

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CN112399676A
CN112399676A CN202011407264.0A CN202011407264A CN112399676A CN 112399676 A CN112399676 A CN 112399676A CN 202011407264 A CN202011407264 A CN 202011407264A CN 112399676 A CN112399676 A CN 112399676A
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voltage
light source
constant current
driving circuit
operational amplifier
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CN112399676B (en
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陈亮
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Opple Lighting Co Ltd
Suzhou Op Lighting Co Ltd
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Opple Lighting Co Ltd
Suzhou Op Lighting 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]
    • H05B45/30—Driver circuits
    • H05B45/345—Current stabilisation; Maintaining constant current
    • 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]
    • H05B45/10—Controlling the intensity of the light
    • 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]
    • H05B45/30—Driver circuits
    • H05B45/32—Pulse-control circuits
    • H05B45/325—Pulse-width modulation [PWM]
    • 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
    • H05B47/00—Circuit arrangements for operating light sources in general, i.e. where the type of light source is not relevant
    • H05B47/10—Controlling the light source
    • H05B47/165—Controlling the light source following a pre-assigned programmed sequence; Logic control [LC]

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Abstract

The application discloses a constant current driving circuit, a calibration method thereof and a lighting device. Compared with the constant current driving circuit, the overturning voltage of the constant current driving circuit is completely changed along with the offset voltage, so that when the light source load works at lower brightness, the problem of obviously incapable fine dimming is solved.

Description

Constant current driving circuit, calibration method thereof and lighting device
Technical Field
The present disclosure relates to the field of lighting technologies, and in particular, to a constant current driving circuit, a calibration method thereof, and a lighting device.
Background
In the lighting device, as shown in fig. 1, the linear constant current driving circuit may include an operational amplifier and a switching tube, one input end of the operational amplifier is connected to a reference voltage source, and the current on a light source Load (LED) is changed by adjusting the reference value of the reference voltage source, so as to achieve the purpose of dimming the LED.
However, the applicant found that in some constant current driving circuits, when the LED is operated at a low brightness, it is obviously impossible to achieve fine dimming of the LED, which was originally an accidental event. After a series of research and analysis, the applicant finds that the offset voltage is caused by the offset voltage in the operational amplifier. Ideally, when the operational amplifier has no offset voltage, the voltage at the two input ends of the operational amplifier is completely equal at the moment when the light source load is turned on, that is, the turning voltage of the constant current driving circuit is zero, and the turning voltage is the reference value of the reference voltage source corresponding to the moment when the light source load is turned on. However, when the offset voltage is present, the independent variable of the switching voltage is the offset voltage, and the smaller the reference value is, the more significant the degree of influence of the offset voltage on the switching voltage is.
Disclosure of Invention
In order to solve the problem that LED dimming is not accurate enough due to the offset voltage of an operational amplifier in a constant current driving circuit, the application provides a constant current driving circuit, a calibration method thereof and a lighting device.
The constant current driving circuit is used for driving a light source load and comprises a control unit, an operational amplifier and a bias circuit;
the operational amplifier comprises a positive input end, a negative input end and an operational amplifier output end;
the control unit is provided with a power supply output end and a sampling end, the power supply output end is used for outputting a reference voltage source and is connected with one of the positive input end or the negative input end, and the sampling end is used for sampling the conduction condition of the light source load; the control unit is used for acquiring a turning voltage, wherein the turning voltage is a reference value of a reference voltage source corresponding to the moment when the light source load is switched on or switched off;
the bias circuit is used for providing a bias voltage and is connected with the other of the positive input end or the negative input end, so that the bias voltage is an independent variable of the turnover voltage.
The constant current driving circuit further comprises a switching tube, a first driving resistor and a current sampling resistor; the current sampling resistor and the switch tube are sequentially connected in series from the grounding end to the light source load, the switch tube comprises a control end, and two ends of the first driving resistor are respectively connected with the operational amplifier output end and the control end.
In the constant current driving circuit, the switching tube is an MOS tube and includes a gate, a source, and a drain, the gate is the control terminal, two ends of the current sampling resistor are respectively connected to the drain and the ground, and the source is connected to the negative electrode of the light source load. .
In the constant current driving circuit, the output end of the voltage source is connected with the positive input end, and the bias circuit is connected with the negative input end; the sampling end is connected with the operational amplifier output end or the source electrode.
In the above constant current driving circuit, the bias circuit includes a bias source, a first voltage dividing resistor and a second voltage dividing resistor; the first voltage-dividing resistor is connected between the negative input terminal and the drain, and the second voltage-dividing resistor is connected between the negative input and the bias source.
In the constant current driving circuit, the absolute value of the bias voltage is greater than the absolute value of the offset voltage of the operational amplifier.
In the above constant current driving circuit, the control unit includes an instruction receiving end, where the instruction receiving end is configured to receive an external signal instruction, and the external signal instruction includes a power-on instruction, a start instruction, or a calibration instruction; and the control unit controls the power supply output end according to the external signal instruction.
The constant current driving circuit further comprises a second driving resistor and a feedback device, wherein the second driving resistor is connected between the power output end and the positive input end, and the feedback device is connected between the negative input end and the operational amplifier output end.
The application provides a lighting device, which comprises a light source load and the constant current driving circuit.
The application provides a calibration method of a constant current driving circuit, which is applied to the constant current driving circuit and comprises the following steps:
receiving a calibration instruction;
outputting a reference voltage source to one of a positive input end or a negative input end of the operational amplifier according to the calibration instruction, wherein the reference value of the reference voltage source is adjustable; the other one of the positive input end or the negative input end of the operational amplifier is connected with a bias circuit for providing bias voltage, and the output end of the operational amplifier is connected with a light source load;
determining the turning voltage of the constant current driving circuit according to the conduction condition of the light source load, wherein the turning voltage is a reference value of a reference voltage source corresponding to the moment of conducting or extinguishing the light source load and is equal to the sum of the offset voltage and the offset voltage of the operational amplifier;
and determining a target value of the reference voltage source according to an external dimming command by taking the turnover voltage as a dimming calibration value, wherein the difference between the target value and the dimming calibration value is in direct proportion to the driving current of the light source load.
In the calibration method of the constant current driving circuit, the calibration instruction includes at least one of the following: a power-on instruction, a start instruction, a restart instruction, or a recalibration instruction.
According to the calibration method of the constant current driving circuit, the reference voltage source is a PWM wave and the duty ratio is adjustable;
the determining the target value of the reference voltage source according to the external dimming command by using the flip-flop voltage as the dimming calibration value comprises: and determining a target duty ratio of the reference voltage source according to the external dimming command by taking the duty ratio corresponding to the dimming calibration value as a reference ratio, wherein the difference between the target duty ratio and the reference ratio is in direct proportion to the driving current of the light source load.
According to the calibration method of the constant current driving circuit, a reference voltage source is output to one of a positive input end or a negative input end of the operational amplifier according to the calibration instruction, and in the reference value adjustable setting of the reference voltage source, the initial duty ratio of the PWM wave of the reference voltage source is zero and gradually increased, or the initial duty ratio of the PWM wave is a non-zero preset value and gradually decreased;
the obtaining of the conduction condition of the light source load and determining the turning voltage of the constant current driving circuit, where the turning voltage is a reference value of a reference voltage source corresponding to the moment when the light source load is conducted or extinguished, includes: the turning voltage is a reference value of a reference voltage source corresponding to the moment when the initial duty ratio of the PWM wave is zero and the light source load is turned on in the process of gradually increasing, or the turning voltage is a reference value of a reference voltage source corresponding to the moment when the initial duty ratio of the PWM wave is a non-zero preset value and the light source load is turned off in the process of gradually decreasing.
The calibration method for the constant current driving circuit, wherein the determining of the switching voltage of the constant current driving circuit according to the conduction condition of the light source load, includes:
sampling voltage change of an output end of the operational amplifier or sampling voltage change on the light source load;
and determining the conduction condition of the light source load according to the voltage change.
The above-mentioned at least one technical scheme that this application adopted can reach following beneficial effect:
compared with the constant current driving circuit, the overturning voltage of the constant current driving circuit is completely changed along with the offset voltage, so that when the light source load works at lower brightness, the problem of obviously incapable fine dimming is solved.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the application and together with the description serve to explain the application and not to limit the application. In the drawings:
fig. 1 shows a schematic structural diagram of a constant current driving circuit;
fig. 2 is a schematic diagram showing a structure of a constant current driving circuit in embodiment 1 of the present application;
fig. 3 is a schematic diagram showing another structure of a constant current drive circuit in embodiment 1 of the present application;
fig. 4 is a flowchart showing a calibration method of a constant current drive circuit in embodiment 3 of the present application.
Description of reference numerals:
100' -constant current drive circuit; 10' -a control unit; 20' -a transporter; 30' -a switching tube; i isO' -a drive current;
100-constant current drive circuit; 10-a control unit; 20-transporting and placing device; 30-bias line; q1-switching tube; r1 — first drive resistor; r2 — second drive resistor; r3 — first divider resistance; r4-feedback resistance; r5-current sampling resistor; r6-second voltage dividing resistor; c1 — feedback capacitance; an AD-sampling end; SGND-ground; i isO-a drive current; vMCU-a reference value of a reference voltage source; voffset-OP-an offset voltage; vMCU-convert-a switching voltage; vDeflection-a bias voltage.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the technical solutions of the present application will be described in detail and completely with reference to the following specific embodiments of the present application and the accompanying drawings. It should be apparent that the described embodiments are only some of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
Before the embodiments of the present application are introduced, the offset voltage V of the operational amplifier 20 'in the present constant current driving circuit 100' is specifically describedoffset-OPInfluence on the dimming accuracy of the light source load. Fig. 1 shows a schematic diagram of a constant current driving circuit 100 ', which includes a control unit 10' for generating a reference voltage source, an op amp 20 ', a switching tube 30', and a current sampling resistor R5. Wherein, the source of the switch tube 30' is connected to the negative pole of the light source load. When the light source load is turned on, the operational amplifier 20 'is in a balanced state, that is, the positive input terminal voltage and the negative input terminal voltage of the operational amplifier 20' are equal, and the offset voltage V between the positive input terminal and the negative input terminal is combinedoffset-OPTo obtain the following formula:
VMCU＝R5·IO+Voffset-OP (1)
in this way, it can be seen that,
Figure BDA0002818962200000061
wherein, VMCUR5 is a current sampling resistor, I is a reference value of a reference voltage source output by the control unit 10O' is the current flowing through the current sampling resistor, i.e. the driving current of the light source load, Voffset-OPThe offset voltage of the operational amplifier can be a positive value or a negative value. The greater the drive current through the light source load, the higher the brightness of the light source load and vice versa. Therefore, the purpose of dimming can be achieved by adjusting the reference value of the reference voltage source to change the driving current of the light source load, wherein the reference voltage source can change the reference value of the PWM wave by modulating the duty ratio of the high level of the PWM wave, and further change the driving current of the light source load.
Ideally, if Voffset-OPIs 0, i.e. no offset voltage exists in the operational amplifier 20', the driving current I flowing through the light source load is adjusted in any wayO' with reference voltage source reference value VMCUProportional relation, whereby the reference value V of the reference voltage source can be adjustedMCUAnd accurate dimming is realized.
However, if Voffset-OPIf the light source load is dimmed in a larger brightness range when the offset voltage is not 0, i.e. the operational amplifier 20' has an offset voltage, the reference value V of the reference voltage sourceMCUSet larger, then the driving current I of the light source loadO' with reference voltage source reference value VMCUApproximately proportional relationship, by adjusting the reference value V of the reference voltage sourceMCUDimming can be achieved, but with poor accuracy. However, if the light source load is dimmed in a small luminance range, the reference value V of the reference voltage source is set at this timeMCUAlso set relatively small, e.g. between 10mv and 20mv, whereas Voffset-OPCan reach 7mv, the drive current I of the light source loadO' not only by reference value V of the reference voltage sourceMCUIs also significantly affected by Voffset-OPSo that the drive current I of the light source loadO' with reference value VMCUThe proportional deviation of (a) greatly increases, i.e., significantly affects the dimming control of the light source load. Therefore, only if the LED is operated with a low brightness, it is found by the applicant that it is obviously difficult to achieve a fine dimming of the LED.
It can be understood that at the moment when the light source load of fig. 1 is turned on, that is, the current flowing through the current sampling resistor R5 is 0, the reference value V of the reference voltage source at this moment can be known from equation (1)MCUAnd offset voltage Voffset-OPThe same, i.e. the reverse voltage of the constant current driving circuit 100' is equal to the offset voltage, i.e. the reverse voltage in fig. 1 is completely offset voltage V of the operational amplifier 20offset-OPAnd (4) determining.
In order to solve the above technical problem, embodiments of the present application provide a constant current driving circuit and a lighting device.
Example 1
The constant current driving circuit 100 provided in the embodiment of the present application, as shown in fig. 2, includes a control unit 10, an operational amplifier 20, and a bias line 30. The operational amplifier 20 includes a positive input terminal, a negative input terminal, and an operational amplifier output terminal, the control unit 10 includes a power output terminal and a sampling terminal AD, the power output terminal is used for outputting a reference voltage source and is connected to one of the positive input terminal or the negative input terminal, and the sampling terminal AD is used for sampling the conduction of the light source loadThe situation is as follows. The control unit 10 obtains the switching voltage V of the constant current driving circuit 100 based on the on condition of the light source load and the reference voltage source output by the light source loadMCU-convertIn particular, the switching voltage VMCU-convertA reference value V of a reference voltage source corresponding to the turn-on transient or turn-off transient of the light source loadMCU. The bias circuit 30 is used for providing a bias voltage VDeflectionAnd connecting the positive input terminal or the negative input terminal to the other terminal, i.e. one of the power output terminal and the bias line 30 is connected to the positive input terminal, the other is connected to the negative input terminal, the bias line 30 provides the bias voltage VDeflectionThe switching voltage V of the constant current driving circuit 100 can be changedMCU-convertSo as to flip the voltage VMCU-convertIncomplete offset voltage Voffset-OPVariation, or bias voltage VDeflectionIs a bias voltage V whose magnitude is controllableDeflectionReducing offset voltage Voffset-OPTo the turning voltage VMCU-convertThe degree of influence of (2) improves the fineness of dimming the light source load. Therefore, compared with fig. 1, the constant current driving circuit 100 provided in fig. 2 of the present application can reduce the offset voltage Voffset-OPTo the turning voltage VMCU-convertIs reduced, the offset voltage V is also reducedoffset-OPDrive current I to light source loadOTo achieve a more accurate dimming objective.
In the embodiment of the present application, the power output terminal of the control unit 10 may be connected to the positive input terminal of the operational amplifier 20, and correspondingly, the bias line 30 is connected to the negative input terminal of the operational amplifier 20, and this connection is taken as an example in the following embodiments of the present application. Of course, as a variation, the power output terminal of the control unit 10 may be connected to the negative input terminal of the operational amplifier 20, the bias line 30 is connected to the positive input terminal, and other electronic devices adaptively adjust the connection relationship, so as to realize the bias voltage V provided by the bias line 30DeflectionOffset voltage Voffset-OPFor the drive current IOThe purpose of accurate dimming is achieved.
It should be appreciated that the bias provided by the bias line 30 of the embodiments of the present applicationSet voltage VDeflectionCan be a constant value, so that more accurate dimming can be realized by the reference value of the reference voltage source in the whole dimming process. Of course, in some special cases, the bias voltage V may be setDeflectionSet to variable values to accommodate dimming requirements or to meet the bias voltage VDeflectionOffset voltage Voffset-OPTo the extent of (c).
The constant current driving circuit 100 in the embodiment of the application further includes a switching tube Q1, a first driving resistor R1, and a current sampling resistor R5. The current sampling resistor R5 and the switching tube Q1 can be sequentially connected in series from the ground terminal SGND to the light source load, the switching tube Q1 comprises a control terminal, and two ends of the first driving resistor R1 are respectively connected to the operational amplifier output terminal and the control terminal. That is, the on-off of the switching tube Q1 is controlled by the output level at the output end of the operational amplifier. The switching tube Q1 may be a MOS tube, and the MOS tube may be an N-type MOS tube. The switch Q1 includes a gate, a source and a drain, the gate is obviously a control terminal and is connected to the first driving resistor R1. In other words, two ends of the first driving resistor R1 are respectively connected to the operational amplifier output terminal and the gate, and two ends of the current sampling resistor R5 are respectively connected to the drain and the ground terminal SGND, for sampling the driving current I flowing through the light source loadOAnd the source electrode is connected with the negative electrode of the light source load. The switching tube Q1 may also be a triode. In fig. 2, when the output of the operational amplifier is at a high level, the gate of the switching transistor Q1 is at a high level, the source and the drain are turned on, the light source load is turned on with the constant current driving circuit 100, and the driving current I of the light source load isOAfter passing through the source and drain, the current flows through the current sampling resistor R5. Before the light source load is turned on, the source voltage is at a high potential, and after the light source load is turned on, the source voltage is decreased.
In order to sample whether the light source load is turned on or not, the sampling terminal AD of the control unit 10 may be connected to the output terminal or the source of the operational amplifier. When the sampling terminal AD is connected to the operational amplifier output terminal, it indicates that the switching transistor Q1 is turned on when a high level is sampled, and the light source load is also turned on, so that the reference value V of the reference voltage source output by the control unit 10 at this momentMCUIs the turning voltage VMCU-convertThe size of (2). As another implementationFor example, as shown in fig. 3, the sampling terminal AD may be connected to the source for sampling a voltage between the source and the drain, and when the voltage sampled to the source exceeds a preset voltage, it indicates that the light source load is turned on.
In the embodiment of the present application, the bias circuit 30 may include a bias source, a first voltage dividing resistor R3 and a second voltage dividing resistor R6, the first voltage dividing resistor R3 is connected between the negative input terminal and the drain, and the second voltage dividing resistor R6 is connected between the negative input terminal and the bias source. The voltage of the bias source may be 3.3V or other voltage values, and the first voltage divider resistor R3 and the second voltage divider may be fixed resistors, such that the bias line 30 provides a constant bias voltage VDeflection(ii) a Of course, the first voltage dividing resistor R3 and the second voltage dividing resistor R6 may be adjustable resistors to adjust the bias voltage V provided by the bias circuit 30Deflection。
In order to more obviously offset the offset voltage Voffset-OPFor the drive current IOOf a bias voltage VDeflectionShould be greater than the offset voltage V of the operational amplifier 20offset-OPAbsolute value of (a). For example, offset voltage V of the op-amp 20offset-OPGenerally within 7mv, the bias voltage VDeflectionCan be 1v or 50mv, etc., according to specific requirements. Bias voltage VDeflectionAbsolute value ratio of offset voltage Voffset-OPThe larger the absolute value of (A), the more the offset voltage Voffset-OPFor the drive current IOThe smaller the deviation that can be caused. However, if the bias voltage V in FIG. 2 isDeflectionToo large a setting results in a reference value V of the reference voltage sourceMCUMuch larger than that of fig. 1, and increases the power consumption of the constant current driving circuit 100. Therefore, in the normal case, the bias voltage VDeflectionAn appropriate intermediate datum may be taken.
In the embodiment of the present application, the control unit 10 includes an instruction receiving end, configured to receive an external signal instruction, where the external signal instruction may include a power-on instruction, a start instruction, or a calibration instruction. The control unit 10 controls the power output terminal according to an external signal instruction. Wherein, the power-on instruction is to drive the control unit 10 to power on the operational amplifier 20, the start instruction is to start the operational amplifier 20, and the calibration instruction is to drive the constant current driving circuit 100And (5) calibrating the rows. Specifically, the reference value V of the reference voltage source is set before the light source load is not conducted every timeMCUThe constant current driving circuit 100 may be calibrated from 0 to the time when the light source load is turned on, so that the driving current I of the light source loadOWill not be caused by offset voltage Voffset-OPAnd cannot precisely adjust the light. In other words, with the constant current driving circuit 100 according to the embodiment of the present application, the constant current driving circuit 100 can be calibrated by itself each time the constant current driving circuit 100 is powered on, or when the constant current driving circuit is started up, or when a calibration instruction is received, that is, the constant current driving circuit 100 is automatically calibrated each time the constant current driving circuit is powered on or powered on during the use process of a user.
In the constant current driving circuit 100 according to the embodiment of the present application, the control unit 10 may be a single chip microcomputer or other controller capable of implementing a control function. The constant current driving circuit 100 further includes a second driving resistor R2 and a feedback device, the second driving resistor R2 is connected between the power output terminal and the positive input terminal, the feedback device includes a feedback resistor R4 and a feedback capacitor C1 which are connected in series, and the feedback device is connected between the negative input terminal and the operational amplifier output terminal.
How the offset voltage V is offset by the bias circuit 30 is described below with reference to FIG. 2offset-OPFor the drive current IOA significant effect of (a).
In FIG. 2, the driving current I is just at the moment when the light source load is turned onOAt 0, the voltage across the current sampling resistor R5 is 0, and the voltages at the positive input and the negative input of the opamp 20 are equal, so that the following equation is obtained:
Vdeflection+Voffset-OP＝VMCU-convert (3)
Wherein, VDeflectionA bias voltage, V, supplied to the negative input for the bias line 30offset-OPFor offset voltage, V, of the op-amp 20MCU-convertI.e. the switching voltage, i.e. the reference value V of the reference voltage source corresponding to the instant of turn-on or turn-off of the light source loadMCU。
In fig. 2, the bias source is 3.3V, and therefore,
Figure BDA0002818962200000101
after the light source load is turned on, at this time, the voltage at the negative input terminal of the operational amplifier 20 is:
Figure BDA0002818962200000102
the voltage of the positive input terminal of the operational amplifier 20 is equal to the voltage of the negative input terminal, and is determined by the reference value V of the reference voltage sourceMCUIt was determined, therefore, that the following formula was obtained:
Figure BDA0002818962200000103
thus, it can be seen that
Figure BDA0002818962200000104
And
Figure BDA0002818962200000105
combining the above equations (2) and (8), it can be seen that in fig. 1, as the reference value of the reference voltage source outputted from the control unit 10' is smaller, the drive current I is smallerOWill cause offset voltage Voffset-OPThe more significant the deviation caused, the worse the dimming accuracy; in fig. 2, the reference value V of the reference voltage source outputted by the control unit 10MCUSmaller, due to the bias voltage VDeflectionIs arranged so as to drive a current IOWill be caused by offset voltage Voffset-OPThe deviation caused by the voltage is limited, thereby reducing the offset voltage Voffset-OPThe impact on dimming accuracy.
Example 2
An embodiment of the utility model provides a lighting device, lighting device include the light source load to and embodiment 1's constant current drive circuit 100, constant current drive circuit 100 provides drive current I for the light source loadOWith the constant current driving circuit 100 of embodiment 1, it is possible to more accurately dim the light source load.
Example 3
The embodiment of the present application provides a calibration method for a constant current driving circuit, which may be applied to the constant current driving circuit in embodiment 1, and may also be applied to other constant current driving circuits, where an execution main body of a specific calibration method may be a control unit in the constant current driving circuit, as shown in fig. 4, and includes the following steps:
receiving an external signaling instruction, wherein the external signaling instruction comprises at least one of a power-on instruction, a starting instruction or a calibration instruction;
s402, acquiring a calibration instruction. The calibration instructions include at least one of: the control unit can acquire the calibration instruction when the constant current driving circuit is powered on or started, and at the moment, the light source load does not start to work. During normal operation of the light source load, calibration may also be performed, for example, the control unit starts to perform the calibration step when a restart instruction or a recalibration instruction is received.
S404, outputting a reference voltage source to one of a positive input end or a negative input end of the operational amplifier according to the calibration instruction, wherein the reference value of the reference voltage source can be set in an adjustable way; the other of the positive input end or the negative input end of the operational amplifier is connected with a bias circuit for providing bias voltage, and the output end of the operational amplifier is connected with a light source load. For example, a reference voltage source is output to the positive input terminal of the operational amplifier, the negative input terminal of the operational amplifier is connected with a bias circuit for providing a bias voltage, and the output terminal of the operational amplifier is connected with a light source load.
And S406, determining the turnover voltage of the constant current driving circuit according to the conduction condition of the light source load, wherein the turnover voltage is the reference value of the reference voltage source corresponding to the conduction moment or the extinguishing moment of the light source load and is equal to the sum of the offset voltage and the offset voltage of the operational amplifier. Specifically, the conduction condition of the light source load may be obtained by sampling by the control unit, and the voltage change at the output end of the operational amplifier or the voltage change on the light source load is used to determine the conduction condition of the light source load.
And S408, determining a target value of the reference voltage source according to an external dimming command by taking the turnover voltage as a dimming calibration value, wherein the difference between the target value and the dimming calibration value is in direct proportion to the driving current of the light source load.
In this embodiment of the application, the reference voltage source may be a PWM wave and may have an adjustable duty ratio, and of course, the output of the reference voltage source may be other waveforms with adjustable reference values, which are not described herein again.
When the reference voltage source can be a PWM wave, S408 includes: acquiring a reference ratio, wherein the reference ratio is a duty ratio corresponding to a dimming calibration value in the PWM wave; and determining a target duty ratio of the reference voltage source according to the external dimming command, wherein the difference between the target duty ratio and the reference ratio is in direct proportion to the driving current of the light source load. That is to say, after the required driving current is determined according to the brightness requirement of the light source load, the target duty ratio corresponding to the PWM wave is determined, so that the difference between the target duty ratio and the reference ratio is in direct proportion to the driving current of the light source load, thereby achieving the purpose of more precise dimming.
In S404, outputting the reference voltage source to one of a positive input terminal or a negative input terminal of the op amp includes: the initial duty ratio of PWM of a reference voltage source output to the positive input end of the operational amplifier is zero and is gradually increased; or the initial duty ratio of the PWM of the reference voltage source output to the positive input end of the operational amplifier is a positive value and is gradually reduced.
Correspondingly, in S406, the obtaining of the conduction condition of the light source load and determining the turning voltage of the constant current driving circuit, where the turning voltage is a reference value of a reference voltage source corresponding to a moment of conducting or extinguishing the light source load includes:
the turning voltage is a reference value of a reference voltage source corresponding to the moment when the initial duty ratio of the PWM wave is zero and the light source load is turned on in the process of gradual increase; or the turning voltage is the reference value of the reference voltage source corresponding to the light source load extinguishing moment in the process that the initial duty ratio of the PWM wave is a positive value and is gradually reduced.
As mentioned above, the calibration instruction includes a power-on instruction, a start instruction, a restart instruction, or a recalibration instruction, and calibration is started under the power-on instruction or the start instruction, and then the initial state of the light source load is extinguished when calibration is started, so that the reference value of the reference voltage source can be gradually increased, and the reference value of the reference voltage source corresponding to the moment when the light source load is turned on is obtained and recorded as the turning voltage; and starting calibration under a restart instruction or a recalibration instruction, wherein the initial state of the light source load is conducted when the calibration is started, so that the reference value of the reference voltage source can be gradually reduced, and the reference value of the reference voltage source corresponding to the moment when the light source load is extinguished is obtained and recorded as the turning voltage. Of course, for the op-amp, as can be seen from the above embodiments, the flipping voltage is equal to the sum of the offset voltage of the op-amp and the bias voltage.
By adopting the calibration method of the embodiment of the application, after the calibration instruction is obtained, the reference value of the constant current driving circuit in the reference voltage source is adjusted, so that the control unit can obtain the turnover voltage in the constant current driving circuit and determine the dimming reference value according to the turnover voltage, in the subsequent dimming process, the control unit combines the dimming reference value according to the dimming instruction and determines the target value of the reference voltage source, and the difference between the target value and the dimming calibration value is in direct proportion to the working current of the light source load so as to achieve the purpose of dimming. For example, if the dimming command indicates that the light source load is to operate at 50% brightness, the control unit calculates a target value of the reference voltage source based on the dimming calibration value in combination with the driving current required by the light source load, such that a difference between the target value and the dimming calibration value is proportional to the driving current of the light source load.
In the embodiments of the present application, the difference between the embodiments is described in detail, and different optimization features between the embodiments can be combined to form a better embodiment as long as the differences are not contradictory, and further description is omitted here in view of brevity of the text.
The above description is only an example of the present application and is not intended to limit the present application. Various modifications and changes may occur to those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

Claims (14)

1. A constant current driving circuit is used for driving a light source load and is characterized by comprising a control unit, an operational amplifier and a bias circuit;
the operational amplifier comprises a positive input end, a negative input end and an operational amplifier output end;
the control unit is provided with a power supply output end and a sampling end, the power supply output end is used for outputting a reference voltage source and is connected with one of the positive input end or the negative input end, and the sampling end is used for sampling the conduction condition of the light source load; the control unit is used for acquiring a turning voltage, wherein the turning voltage is a reference value of a reference voltage source corresponding to the moment when the light source load is switched on or switched off;
the bias circuit is used for providing a bias voltage and is connected with the other of the positive input end or the negative input end, so that the bias voltage is an independent variable of the turnover voltage.
2. The constant current driving circuit according to claim 1, further comprising a switching tube, a first driving resistor and a current sampling resistor; the current sampling resistor and the switch tube are sequentially connected in series between the grounding end and the light source load, the switch tube comprises a control end, and two ends of the first driving resistor are respectively connected with the operational amplifier output end and the control end.
3. The constant current driving circuit according to claim 2, wherein the switching transistor is an MOS transistor and includes a gate, a source, and a drain, the gate is the control terminal, two ends of the current sampling resistor are respectively connected to the drain and a ground, and the source is connected to a negative electrode of the light source load.
4. The constant current driving circuit according to claim 3, wherein the voltage source output terminal is connected to the positive input terminal, and the bias line is connected to the negative input terminal; the sampling end is connected with the operational amplifier output end or the source electrode.
5. The constant current driving circuit according to claim 3, wherein the bias line includes a bias source, a first voltage dividing resistor, and a second voltage dividing resistor; the first voltage-dividing resistor is connected between the negative input terminal and the drain, and the second voltage-dividing resistor is connected between the negative input and the bias source.
6. The constant current driving circuit according to claim 1, wherein an absolute value of the bias voltage is larger than an absolute value of an offset voltage of the op amp.
7. The constant current driving circuit according to claim 1, wherein the control unit includes an instruction receiving terminal configured to receive an external signal instruction, the external signal instruction including a power-on instruction, a start instruction, or a calibration instruction; and the control unit controls the power supply output end according to the external signal instruction.
8. The constant current driving circuit according to claim 1, further comprising a second driving resistor and a feedback device, wherein the second driving resistor is connected between the power output terminal and the positive input terminal, and the feedback device is connected between the negative input terminal and the operational amplifier output terminal.
9. A lighting device comprising a light source load, and the constant current drive circuit according to any one of claims 1 to 8.
10. A calibration method of a constant current driving circuit is applied to the constant current driving circuit, and is characterized by comprising the following steps:
acquiring a calibration instruction;
outputting a reference voltage source to one of a positive input end or a negative input end of the operational amplifier according to the calibration instruction, wherein the reference value of the reference voltage source is adjustable; the other one of the positive input end or the negative input end of the operational amplifier is connected with a bias circuit for providing bias voltage, and the output end of the operational amplifier is connected with a light source load;
determining the turning voltage of the constant current driving circuit according to the conduction condition of the light source load, wherein the turning voltage is a reference value of a reference voltage source corresponding to the moment of conducting or extinguishing the light source load and is equal to the sum of the offset voltage and the offset voltage of the operational amplifier;
and determining a target value of the reference voltage source according to an external dimming command by taking the turnover voltage as a dimming calibration value, wherein the difference between the target value and the dimming calibration value is in direct proportion to the driving current of the light source load.
11. The method according to claim 10, wherein the calibration instruction includes at least one of: a power-on instruction, a start instruction, a restart instruction, or a recalibration instruction.
12. The calibration method of the constant current drive circuit according to claim 10, wherein the reference voltage source is a PWM wave and the duty ratio is adjustable;
the determining the target value of the reference voltage source according to the external dimming command by using the flip-flop voltage as the dimming calibration value comprises:
acquiring a reference ratio, wherein the reference ratio is a duty ratio corresponding to the dimming calibration value in the PWM wave;
and determining a target duty ratio of the reference voltage source according to the external dimming command, wherein the difference between the target duty ratio and the reference ratio is in direct proportion to the driving current of the light source load.
13. The method for calibrating the constant current driver circuit according to claim 12, wherein outputting the reference voltage source to one of a positive input terminal or a negative input terminal of the amplifier comprises:
the initial duty ratio of PWM of a reference voltage source output to the positive input end of the operational amplifier is zero and is gradually increased; or
The initial duty ratio of the PWM of the reference voltage source output to the positive input end of the operational amplifier is a positive value and is gradually reduced;
the obtaining of the conduction condition of the light source load and determining the turning voltage of the constant current driving circuit, where the turning voltage is a reference value of a reference voltage source corresponding to the moment when the light source load is conducted or extinguished, includes:
the turning voltage is a reference value of a reference voltage source corresponding to the moment when the initial duty ratio of the PWM wave is zero and the light source load is turned on in the process of gradual increase; or
The turning voltage is a reference value of a reference voltage source corresponding to the moment when the light source load is extinguished in the process that the initial duty ratio of the PWM wave is a positive value and is gradually reduced.
14. The method for calibrating the constant current driving circuit according to claim 10, wherein the determining the switching voltage of the constant current driving circuit according to the conduction condition of the light source load comprises:
sampling voltage change of an output end of the operational amplifier or sampling voltage change on the light source load;
and determining the conduction condition of the light source load according to the voltage change.
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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114937433A (en) * 2022-01-27 2022-08-23 成都利普芯微电子有限公司 Constant-current driving circuit, driving chip and electronic device for LED display screen
CN117354996A (en) * 2023-02-02 2024-01-05 上海谭慕半导体科技有限公司 Control system and method for LED driver, and readable storage medium

Citations (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH10123184A (en) * 1996-10-17 1998-05-15 Fuji Electric Co Ltd Current detection circuit
JPH1168476A (en) * 1997-08-12 1999-03-09 Sony Corp Offset adjusting circuit of operation amplifier
JP2011018691A (en) * 2009-07-07 2011-01-27 Ccs Inc Led drive
CN202425103U (en) * 2011-11-22 2012-09-05 四川华体照明科技股份有限公司 LED (light-emitting diode) street lamp regulation device based on DC-DC PWM (pulse-width modulation) light adjustment driving
CN103337958A (en) * 2013-05-01 2013-10-02 上海芯地信息科技有限公司 Constant current circuit of DC converter
CN104602418A (en) * 2015-02-02 2015-05-06 常州丰泰机电工程有限公司 Adjustable constant flow source driving circuit for LED
CN105307310A (en) * 2014-06-25 2016-02-03 陈小莉 Low-dropout constant current LED driving method
CN106535390A (en) * 2016-10-09 2017-03-22 深圳创维－Rgb电子有限公司 Constant current driving power supply and display equipment
US20170117861A1 (en) * 2015-10-22 2017-04-27 Futurewei Technologies, Inc. System and Method for Offset Voltage Calibration
US20190243402A1 (en) * 2017-11-28 2019-08-08 Shenzhen GOODIX Technology Co., Ltd. Voltage regulator and power supply
CN110602824A (en) * 2019-09-12 2019-12-20 广州市哈雅光电设备有限公司 LED soft light hybrid control circuit and method thereof
CN111343764A (en) * 2020-03-05 2020-06-26 深圳市晟碟半导体有限公司 LED dimming circuit, device and dimming method thereof
CN211378324U (en) * 2020-02-11 2020-08-28 深圳市明微电子股份有限公司 Constant current drive control circuit and system
CN213818277U (en) * 2020-12-04 2021-07-27 欧普照明股份有限公司 Constant current drive circuit and lighting device

Patent Citations (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH10123184A (en) * 1996-10-17 1998-05-15 Fuji Electric Co Ltd Current detection circuit
JPH1168476A (en) * 1997-08-12 1999-03-09 Sony Corp Offset adjusting circuit of operation amplifier
JP2011018691A (en) * 2009-07-07 2011-01-27 Ccs Inc Led drive
CN202425103U (en) * 2011-11-22 2012-09-05 四川华体照明科技股份有限公司 LED (light-emitting diode) street lamp regulation device based on DC-DC PWM (pulse-width modulation) light adjustment driving
CN103337958A (en) * 2013-05-01 2013-10-02 上海芯地信息科技有限公司 Constant current circuit of DC converter
CN105307310A (en) * 2014-06-25 2016-02-03 陈小莉 Low-dropout constant current LED driving method
CN104602418A (en) * 2015-02-02 2015-05-06 常州丰泰机电工程有限公司 Adjustable constant flow source driving circuit for LED
US20170117861A1 (en) * 2015-10-22 2017-04-27 Futurewei Technologies, Inc. System and Method for Offset Voltage Calibration
CN106535390A (en) * 2016-10-09 2017-03-22 深圳创维－Rgb电子有限公司 Constant current driving power supply and display equipment
US20190243402A1 (en) * 2017-11-28 2019-08-08 Shenzhen GOODIX Technology Co., Ltd. Voltage regulator and power supply
CN110602824A (en) * 2019-09-12 2019-12-20 广州市哈雅光电设备有限公司 LED soft light hybrid control circuit and method thereof
CN211378324U (en) * 2020-02-11 2020-08-28 深圳市明微电子股份有限公司 Constant current drive control circuit and system
CN111343764A (en) * 2020-03-05 2020-06-26 深圳市晟碟半导体有限公司 LED dimming circuit, device and dimming method thereof
CN213818277U (en) * 2020-12-04 2021-07-27 欧普照明股份有限公司 Constant current drive circuit and lighting device

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
MICHAEL HEIDINGER等: "Constant Current Paralleling Controller for Mid-Power LED", 《PCIM EUROPE 2017; INTERNATIONAL EXHIBITION AND CONFERENCE FOR POWER ELECTRONICS, INTELLIGENT MOTION, RENEWABLE ENERGY AND ENERGY MANAGEMENT》 *
徐星: "白光LED驱动器的研究与设计", 《万方数据》 *
段方: "高精度低噪声轨到轨运算放大器设计与实现", 《中国优秀硕士学位论文全文数据库（电子期刊）-信息科技辑》 *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114937433A (en) * 2022-01-27 2022-08-23 成都利普芯微电子有限公司 Constant-current driving circuit, driving chip and electronic device for LED display screen
CN114937433B (en) * 2022-01-27 2023-11-14 成都利普芯微电子有限公司 LED display screen constant current drive circuit, drive chip and electronic equipment
CN117354996A (en) * 2023-02-02 2024-01-05 上海谭慕半导体科技有限公司 Control system and method for LED driver, and readable storage medium
CN117354996B (en) * 2023-02-02 2024-05-14 上海谭慕半导体科技有限公司 Control system and method for LED driver, and readable storage medium

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