CN114585127A - Control circuit for LED lighting device - Google Patents

Control circuit for LED lighting device Download PDF

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Publication number
CN114585127A
CN114585127A CN202011376075.1A CN202011376075A CN114585127A CN 114585127 A CN114585127 A CN 114585127A CN 202011376075 A CN202011376075 A CN 202011376075A CN 114585127 A CN114585127 A CN 114585127A
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led load
shunt resistor
value
max
circuit
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CN114585127B (en
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李世春
赵震宇
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Panasonic Manufacturing Beijing Co Ltd
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Panasonic Manufacturing Beijing 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
    • H05B45/32—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
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/50—Circuit arrangements for operating light-emitting diodes [LED] responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits
    • H05B45/52—Circuit arrangements for operating light-emitting diodes [LED] responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits in a parallel array of LEDs
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B20/00—Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
    • Y02B20/40—Control techniques providing energy savings, e.g. smart controller or presence detection

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  • Circuit Arrangement For Electric Light Sources In General (AREA)

Abstract

The invention provides a control circuit for an LED lighting device, comprising: an LED load; the output end of the driving circuit including the chip is connected with the LED load, and the driving circuit outputs driving current to drive the LED load to adjust light; the signal generating circuit outputs dimming signals, the output end of the signal generating circuit is connected with the driving circuit, and the signal generating circuit is further provided with a shunt resistor connected with the LED load in parallel. The control circuit for the LED lighting device provided by the invention can meet the requirement of low brightness of an LED load, makes up for the deficiency of the current brightness regulation, enlarges the range of minimum brightness regulation and effectively improves the substitution feeling and experience feeling.

Description

Control circuit for LED lighting device
Technical Field
The invention relates to the technical field of control circuits, in particular to a control circuit for an LED lighting device, which can provide extremely low LED brightness for the LED lighting device.
Background
With the continuous expansion of LED (Light Emitting Diode) lighting applications, more and more LED lighting applications need a dimming function, and there are two main schemes for achieving the LED dimming function, one is analog dimming, and the other is PWM (Pulse Width modulation) dimming. The dimming mode is also called chopping, the brightness of the light of the LED is adjusted by controlling the output current, namely the driving current, of the LED driving circuit by adopting the PWM, and the larger the driving current is, the higher the brightness is.
The prior art usually pursues how to improve the driving current to improve the brightness of the LED, but as people have higher requirements for the brightness range of the LED lighting device, especially for the increase of the low brightness requirement, for example, a breathing lamp designed for improving the sleep quality of a user, there is a certain requirement for the low brightness, because people can enter a sleep state faster in an environment with lower brightness, and the guidance substitution feeling of sleep is stronger in the low brightness atmosphere. Fig. 1 is a schematic diagram of a related circuit of a lighting device in the prior art, and as shown in fig. 1, according to a PWM dimming manner, in order to adjust the brightness of an LED load 1, after a chip 5 processes and calculates according to a duty ratio of a PWM dimming signal output by a signal generating circuit 3, a driving circuit 2 correspondingly outputs a driving current to adjust the brightness of the LED load 1. However, when the PWM signal duty ratio is reduced to a certain value, for example, to 2% in the prior art, the driving current for dimming the LED load 1 output by the driving circuit 2 cannot be further reduced due to the processing capability of the chip 5, the light emitting brightness of the LED load 1 cannot be further reduced, and even if the user wants to obtain a lower brightness, the user cannot adjust the brightness in the dark, and only enters the off state. Fig. 2 and 3 show a current waveform and a brightness waveform of the LED load 1 in the related art, respectively. When the current flowing through the LED load 1 reaches the adjustable minimum current value during the decreasing process, the current cannot continue to decrease along the waveform curve, and accordingly, the brightness of the LED load 1 reaches the minimum adjustable brightness, and the dimming cannot continue.
Therefore, in a scene needing to be adjusted to be darker, the problem of high brightness still exists, the requirement of a user for lower brightness cannot be met, better sleep guidance substitution feeling cannot be provided for the user, and user experience is reduced.
Therefore, a control circuit for an LED lighting device is needed to expand the minimum brightness range of PWM adjustment and meet the user's requirement for lower brightness of the LED.
Disclosure of Invention
In view of the defects in the prior art, an object of the present invention is to provide a control circuit for an LED lighting device, which can expand the minimum brightness range of PWM adjustment and meet the user's requirement for lower brightness.
According to the present invention, there is provided a control circuit for an LED lighting device, comprising:
an LED load;
the output end of the driving circuit including the chip is connected with the LED load, and the driving circuit outputs driving current to drive the LED load to adjust light;
the signal generating circuit outputs a dimming signal, and the output end of the signal generating circuit is connected with the driving circuit;
and a shunt resistor connected in parallel with the LED load.
According to the above technical solution, by providing the shunt resistor in parallel with the LED load, that is, by connecting an appropriate resistance value in parallel to the output terminal, the shunt resistor in parallel bears a certain current component, so that the current value passing through the LED load is further reduced, and therefore the current passing through the LED load is further reduced due to the existence of the current component borne by the shunt resistor, and the brightness of the LED load is further dimmed. Therefore, can be through setting up this simple components and parts of shunt resistance, can be under the condition that does not change circuit design to the user has been satisfied with the demand of lower luminance with lower cost, has effectively promoted the guide substitution sense of helping dormancy.
Preferably, the resistance value R of the shunt resistor is at least equal to the second predetermined operating voltage V of the LED load2And the maximum driving current value I _ofthe driving circuit outputmaxIs set in a correlated manner, wherein the maximum drive current value I _maxIs corresponding to the second specified operating voltage V2The drive current value output by the drive circuit.
Preferably, the resistance value R of the shunt resistor satisfies the conditions of the following numerical expressions (1), (2) and (3),
R＞V2/Imaxformula (1)
IR_max＝V2R, formula (2)
IR_max/Imax< Y, formula (3)
In the formula, V2A second predetermined operating voltage for the LED load, IR_maxFor the LED load to be at the second specified working voltage V2The current value I (u) flowing through the shunt resistormaxFor the LED load at a second predetermined operating voltage V2The maximum drive current value output by the time drive circuit is Y set to a predetermined value.
More preferably, the value of Y in the numerical formula (3) is not less than 0.972.
According to the technical scheme, when the shunt resistor is selected and configured for the LED load, the resistance value R of the shunt resistor is at least equal to the second specified working voltage V of the LED load2The LED load is at a second specified working voltage V2Maximum driving current value I _oftime-lapse driving circuit outputmaxIn this case, the resistance value of the shunt resistor may be determined so that the current component of the shunt resistor is excessively large at a high operating voltage and the current component of the LED load is excessively small so that the LED load cannot be turned on. Thus, according to the second prescribed operating voltage V of the LED load2The LED load is at a second specified working voltage V2Maximum driving current value I _oftime-lapse driving circuit outputmaxThe resistance value of the shunt resistor is configured and set in a correlated manner, the lower limit value of the shunt resistor can be effectively selected and configured for the LED load, and the circuit design is simplified on the premise of ensuring lower illumination brightness.
Preferably, the resistance value R of the shunt resistor is at least equal to the first predetermined operating voltage V of the LED load1And the LED load is at a second specified operating voltage V2Maximum driving current value I _oftime-lapse driving circuit outputmaxAre set in a correlated manner, wherein the maximum drive current value I _maxIs a second specified operating voltage V corresponding to said LED load2The drive current value output by the drive circuit.
Preferably, the resistance value R of the shunt resistor satisfies the conditions of the following numerical expressions (4) and (5),
IR_min＝V1r, formula (4)
IR_min/I_max> X, formula (5)
In the formula, V1A first predetermined operating voltage for the LED load, IR_minIn order to maintain the LED load at a first specified operating voltage V1The value of current flowing through the shunt resistor, I \umaxX is a predetermined value for the maximum driving current value output from the driving circuit.
More preferably, the value of X in the formula (5) is not more than 0.0091.
According to the technical scheme, when the shunt resistor is configured and set for the LED load, the resistance value R of the shunt resistor is specified to be at least equal to the first specified working voltage V of the LED load1And the maximum driving current value I _, which is outputted by the driving circuitmaxIn this case, the resistance value of the shunt resistor may be determined under the condition that the LED load is at a predetermined operating voltage, for example, a lower operating voltage, so that the current component of the shunt resistor at the lower operating voltage is too small due to the excessively large resistance value of the shunt resistor, which may not effectively act as a shunt for the LED load, and unnecessary circuit loss due to the excessively large resistance value of the shunt resistor may be avoided.
Thus, according to the first prescribed operating voltage V of the LED load1The LED load is at a second specified working voltage V2Maximum driving current value I _oftime-lapse driving circuit outputmaxThe resistance value of the shunt resistor is configured and set in a correlated manner, the upper limit value of the shunt resistor can be effectively set for the LED load configuration, the circuit design is simplified on the premise of ensuring that the illumination brightness is lower, and unnecessary circuit loss is avoided.
Preferably, the signal generating circuit is a PWM signal generating circuit, and the resistance value R of the shunt resistor is set in association with the duty ratio DR of the PWM dimming signal output from the PWM signal generating circuit.
Preferably, the resistance R of the shunt resistor is set under the condition that the duty ratio DR of the PWM dimming signal output from the PWM signal generation circuit is less than 2%.
Preferably, the resistance R of the shunt resistor is set under the condition that the duty ratio DR of the PWM dimming signal output from the PWM signal generation circuit is less than 1%.
According to the above technical solution, when the shunt resistor is configured for the LED load, the shunt resistor is set in association with the duty ratio DR of the PWM dimming signal output by the PWM signal generation circuit, and in order to solve the problem that, in the prior art, when the duty ratio DR of the PWM dimming signal output by the PWM signal generation circuit is lower than a specific value, for example, 2% or 1%, the luminance of the LED load cannot be further reduced, the shunt resistor is set in association with the ground, so that the current component borne by the shunt resistor is adapted and matched with the driving current when the duty ratio DR of the PWM dimming signal is lower than the specific value, for example, 2% or 1%, the adjustment of the LED load with lower luminance is realized, and the guiding substitution experience of the user for assisting sleep is improved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
FIG. 1 is a schematic circuit diagram of a lighting device in the prior art;
FIG. 2 is a schematic current waveform diagram of a prior art LED load;
FIG. 3 is a diagram illustrating a brightness adjustment waveform of an LED load according to the prior art;
FIG. 4 is a schematic diagram of a control circuit for an LED lighting device according to the present invention;
FIG. 5 is a schematic diagram of a current waveform of an LED load of the control circuit of the present invention;
fig. 6 is a waveform diagram illustrating the brightness adjustment of the LED load of the control circuit according to the present invention.
Description of reference numerals:
an LED load 1; a drive circuit 2; a signal generation circuit 3; a shunt resistor 4; and a chip 5.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, 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 invention.
Fig. 4 is a schematic structural diagram of a control circuit for an LED lighting device according to this embodiment, and as shown in fig. 4, the control circuit includes: an LED load 1; the output end of the driving circuit 2 including the chip 5 is connected with the LED load 1, and the driving circuit outputs driving current to drive the LED load 1 to adjust light; the signal generating circuit 3 outputs a PWM dimming signal, an output end of the signal generating circuit is connected to the driving circuit 2, and a shunt resistor 4 connected in parallel to the LED load 1 is further provided.
Specifically, the number, arrangement order, LED emission color, model, and the like of the LEDs of the LED load 1 are not limited; preferably, the light-emitting diode also comprises an organic light-emitting diode OLED; the light emission luminance of the LED load 1 depends on the magnitude of the current flowing through the LED load 1, and at a certain rated voltage, the light emission intensity of the LED load 1 increases (within a certain range) as the current flowing through the LED load 1 increases, and the light emission intensity of the LED load 1 decreases (within a certain range) as the current flowing through the LED load 1 decreases. The signal generating circuit 3 is used for generating a PWM dimming signal and outputting the generated PWM dimming signal to the driving circuit 2 including the chip 5; after receiving the PWM dimming signal, the driving circuit 2 generates a driving current through internal processing and outputs the driving current to the LED load 1, thereby driving the LED load 1 to perform dimming. When the duty ratio of the PWM dimming signal is large, the output driving current is large, and the corresponding LED load 1 is bright, whereas when the duty ratio of the PWM dimming signal is small, the output driving current is small, and the corresponding LED load is dark.
It should be noted that the chip 5 is a chip used for LED dimming control in the prior art, and the specific model of the chip 5 is not limited as long as the chip can process the PWM dimming signal and output the driving current to the LED load 1.
The shunt resistor 4 is arranged in parallel with the LED load 1, and it should be noted that the arrangement number and arrangement form of the resistors of the shunt resistor 4 are not limited as long as the equivalent resistor of the shunt resistor 4 is connected in parallel with the LED load 1 and can generate a certain shunt function for the LED load 1. Specifically, according to the related circuit theory, under the normal operation of the circuit, since the shunt resistor 4 is connected in parallel with the LED load 1, the shunt resistor 4 and the LED load 1 share the total driving current output from the driving circuit 2 according to the corresponding circuit relationship.
The chip 5 has a limited duty ratio adjusting range for the PWM dimming signal due to the limitation of the processing capability of the chip 5; specifically, when the duty ratio of the PWM dimming signal is lower than a certain limit, for example, 2%, the driving circuit 2 cannot further lower the output value of the driving current in accordance with the duty ratio because of the processing capability of the chip 5, and therefore, when the duty ratio of the PWM dimming signal is adjusted down to a certain limit, for example, 2%, the brightness of the LED load 1 cannot be adjusted lower even if the duty ratio of the PWM dimming signal is adjusted down again.
Since the shunt resistor 4 is provided in this embodiment, the shunt resistor 4 is connected in parallel with the LED load 1, and the driving current generated by the driving circuit 2 flows to the LED load 1 and the shunt resistor 4 connected in parallel with the LED load 1, according to the theory related to parallel shunt, the shunt resistor 4 and the LED load 1 share the total driving current output by the driving circuit 2, so that the current passing through the LED load 1 is necessarily smaller than the total driving current output by the driving circuit 2, in other words, the driving current output by the driving circuit 2 is equal to the sum of the current component passing through the LED load 1 and the current component passing through the shunt resistor 4.
In this case, compared to the technical limitation that the brightness of the LED load 1 cannot be adjusted to be continuously darker after the duty ratio of the PWM dimming signal is lower than a certain limit, in the embodiment of the present invention, because the shunt resistor 4 is provided, if a darker brightness requirement is required at this time, the current flowing through the LED load 1 is smaller than the driving current output by the driving circuit 2 due to the parallel arrangement of the shunt resistor 4 and the LED load 1, and compared to the case that the parallel shunt resistor 4 is not provided, the current flowing through the LED load 1 is smaller than the driving current output by the driving circuit 2, therefore, even if the output of the PWM dimming signal is lower than the duty ratio limit and the driving current output by the driving circuit 2 cannot be reduced any more, the current component flowing through the LED load 1 can be further reduced due to the arrangement of the shunt resistor 4, so that the LED load 1 can achieve a darker luminance, the requirement of the user for lower brightness is met.
Fig. 5 is a schematic diagram of a waveform of a current flowing through the LED load 1 in the control circuit of the present invention, and fig. 6 is a schematic diagram of a waveform of brightness adjustment of the LED load 1 in the control circuit of the present invention. As can be seen from fig. 5 and fig. 6, during the PWM dimming control, since the driving current from the driving circuit 2 is partially shunted by the shunt resistor 4, the current flowing through the LED load 1 can continue to decrease along the waveform curve, so as to obtain more reduction space, and thus the lowest adjustable brightness of the LED load 1 is further reduced, that is, the LED load 1 can be adjusted to emit darker light compared with the prior art.
The waveforms of fig. 2 and 3 relating to the prior art and fig. 5 and 6 relating to the embodiment of the present invention are schematic diagrams, and are not absolute values. The effect is that in the control circuit of the present invention, the current value flowing through the LED load 1 can be reduced to be lower than that in the prior art, so that the light emitting brightness of the LED load 1 can be adjusted to be darker.
In the above-described embodiment, the shunt resistor 4 is connected in parallel to the output terminal of the drive circuit 2, and the shunt resistor 4 connected in parallel is caused to bear a part of the current component of the drive current, and the value of the current component passing through the LED load 1 is further reduced, so that the luminance of the LED load 1 is also reduced in accordance with the reduction of the value of the current flowing through the LED load, and the luminance of the LED load 1 can be reduced at low cost with a simple circuit configuration without being limited to the influence of the processing capability of the chip 5. Thereby satisfying the requirement of the user on lower brightness and effectively improving the sense of introduction of sleep-aid guidance.
The guidance substitution feeling is an evaluation index for helping a user to fall asleep as soon as possible, and specifically means the action degree that the brightness change cycle of the LED load 1 is matched with the change cycle of the physiological index of the user, and the user is guided to fall asleep by the brightness change rhythm of the LED load 1. The stronger the induction substitution feeling is, the easier the sleep state is to be entered, the better the sleep-assisting effect is, and otherwise, the sleep-assisting effect is not good. Experiments prove that in the brightness change period of the LED load 1, if the LED load 1 is dimmed to the lowest possible brightness and the brightness is maintained for a fixed time, better sleep-assisting guidance substitution feeling can be obtained.
Hereinafter, how the resistance values of the shunt resistors 4 are arranged in the embodiment of the present invention will be described.
[ configuration of shunt resistance 4 resistance value ]
The technical idea of the control circuit for the LED lighting device provided by the present invention is specifically set forth above: in order to meet the requirement of lower brightness, the shunt resistor 4 is arranged in parallel with the LED load 1, and due to the shunt function of the shunt resistor 4, the current flowing through the LED load 1 is smaller than the driving current output by the driving circuit 2, so that the light emitting effect of lower brightness is achieved.
Therefore, it is one of the technical points of the control circuit for the LED lighting device provided by the present invention to configure the specific resistance value of the shunt resistor 4, and then, based on the above technical ideas, the selection and setting range of the resistance value of the shunt resistor 4 will be described in detail.
Specifically, when configuring the appropriate resistance value R of the shunt resistor 4 for the control circuit, not only the factor that the shunt resistor 4 bears part of the current component of the driving current at the lower operating voltage (at this time, the driving current is also smaller) so as to reduce the current component flowing through the LED load 1 is considered, but also whether the shunt resistor 4 bears part of the current component of the driving current at the higher operating voltage (at this time, the driving current is also larger) after the resistance value R is once selected, so as to affect the normal light emission of the LED load 1 is considered. Therefore, it is necessary to consider both the case where the operating voltage is high (the driving current is large) and the case where the operating voltage is low (the driving current is small), and on the basis of this, the resistance value R of the shunt resistance 4 is determined with reference to other factors.
< lower limit selection regarding resistance value of shunt resistor 4 >
In the above embodiment, the resistance R of the shunt resistor 4 of the control circuit for the LED lighting device according to the present invention is at least equal to the second predetermined operating voltage V of the LED load 12And the maximum driving current value I _, which is outputted from the driving circuit 2maxSet in association with the maximum drive current value I _maxIs that the LED load 1 is at a second prescribed operating voltage V2The drive current value outputted from the drive circuit 2.
Specifically, in order to determine the lower limit of the resistance value R of the shunt resistor 4, i.e., the minimum resistance value that can be selected for the resistance value R of the shunt resistor 4 under the condition of ensuring that the lower brightness requirement is satisfied and the entire circuit structure stably operates.
According to the related theorem formula, the resistance value R of the shunt resistor 4 and the current component I flowing through the shunt resistor 4RAnd the magnitude of the voltage applied to the shunt resistance 4. Therefore, in the first aspect, since the shunt resistor 4 and the LED load 1 are in a parallel relationship, and the voltage of the shunt resistor 4 is the operating voltage of the LED load 1, the magnitude of the resistance value R of the shunt resistor 4 is also related to the operating voltage of the LED load 1, that is, the second predetermined operating voltage V of the LED load 12There is a relationship. It should be noted that the second predetermined operating voltage V of the LED load 1 defined in the embodiment of the present invention2Not limited to the maximum predetermined operating voltage of the LED load 1, the second predetermined operating voltage V2It is also possible to provide the LED load 1 with a predetermined operating voltage under normal bright lighting conditions, i.e. a higher operating voltage in the nominal range. In the second aspect, since the shunt resistor 4 and the LED load 1 are in a parallel relationship, the drive current value output from the drive circuit 2 is theoretically equal to the sum of the current component value flowing through the LED load 1 and the current component value flowing through the shunt resistor 4That is, the resistance value of the shunt resistor 4 is also related to the magnitude of the drive current output by the drive circuit 2.
Furthermore, the limit value of the resistance value R of the shunt resistor 4 is determined under the condition that the LED load 1 is at a predetermined operating voltage, for example, a high operating voltage, and it is possible to avoid a situation in which the current component of the shunt resistor 4 is excessively large at a high operating voltage and the current component of the LED load 1 is excessively small to turn on the LED load 1 when the resistance value R of the shunt resistor 4 is excessively small. Thus, according to the second prescribed operating voltage V of the LED load 12The LED load 1 is at a second specified operating voltage V2Maximum drive current value I _, output by time drive circuit 2maxThe resistance value R of the shunt resistor 4 is configured and set in a correlated manner, so that the lower limit value of the shunt resistor 4 can be effectively selected and configured for the LED load 1, and on the premise of ensuring lower illumination brightness, the circuit design is simplified, and the safe and stable operation of the control circuit is ensured.
It should be further noted that the resistance value R of the shunt resistance 4 preferably satisfies the conditions of the following numerical expressions (1), (2) and (3),
R＞V2/I_maxformula (1)
IR_max＝V2R, formula (2)
IR_max/I_max< Y, formula (3)
In the formula, V2A second predetermined operating voltage, I, for the LED load 1R_maxTo maintain the LED load 1 at a second predetermined operating voltage V2A current value I _, of the time-current shunt resistor 4maxFor the LED load 1 to be at a second predetermined operating voltage V2The maximum drive current value Y output by the time drive circuit 2 is a predetermined value.
From the above equation (1), it can be found that the lower limit of the resistance value R of the shunt resistor 4 is arranged in relation to the second predetermined operating voltage V of the LED load 12And the second prescribed operating voltage V2Maximum drive current value I _, output by time drive circuit 2maxAssociating, specifically with the condition R > V2/I_max. As can be understood from the above equation (2), the LED load1 at a second defined operating voltage V2The current value I flowing through the shunt resistor 4R_max＝V2and/R. As is clear from the above equation (3), since the shunt resistor 4 is connected in parallel with the LED load 1, in order to make the LED load 1 meet the actual requirement of lower luminance, the shunt resistor 4 divides a part of the current component of the driving current, and the current value I flowing through the shunt resistor 4R_maxLess than the maximum driving current value I _, output by the driving circuit 2maxThat is, the value of the current flowing through the shunt resistor 4 accounts for the maximum driving current value I _, which is outputted from the driving circuit 2maxAt a certain ratio, the smaller the resistance value of the shunt resistor 4 is, the smaller the value of the current I flowing through the shunt resistor 4R_maxThe larger the current component is, the larger the value of the maximum driving current I _, which is output by the driving circuit 2maxThe higher.
Therefore, the higher operating voltage of the LED load 1 is taken as the second predetermined operating voltage V2And with reference to a second predetermined operating voltage V2And a maximum driving current value I _, which is outputted from the driving circuit 2maxBy setting the resistance value R of the shunt resistor 4 in a correlated manner, it is possible to avoid a situation that the current component of the shunt resistor 4 is too large at a higher operating voltage due to too small configuration of the resistance value R of the shunt resistor 4, and the LED load 1 cannot be turned on due to too small current component of the LED load 1.
In the above embodiment, the resistance value R of the shunt resistor 4 is limited to be equal to at least the second predetermined operating voltage V of the LED load 12And the maximum driving current value I _ofthe driving circuit outputmaxThe satisfied condition relation is set in a correlated manner and further defined, and the lower limit of the resistance value R of the shunt resistor 4 is determined, so that the requirement of a user for adjusting the illumination brightness is met, and the experience of the user is further improved.
< selection of the upper limit of the resistance value of shunt resistor 4 >
Based on the above embodiment, the resistance value R of the shunt resistor 4 of the control circuit for the LED lighting device according to the present invention is at least equal to the first predetermined operating voltage V of the LED load 11And the maximum driving current value I _, which is outputted by the driving circuitmaxAre set in association with one another, wherein maximumDrive current value I _maxIs a second specified operating voltage V corresponding to said LED load2The drive current value outputted from the drive circuit.
Specifically, in order to determine the upper limit of the resistance value R of the shunt resistance 4, that is, the maximum resistance value of the resistance value R of the shunt resistance 4 under the condition that the lower luminance requirement is ensured to be satisfied.
According to the related theorem formula, the resistance value R of the shunt resistor 4 is equal to the current I flowing through the shunt resistor 4RAnd the magnitude of the voltage across the shunt resistor 4. And the above<Lower limit selection of resistance value of shunt resistor 4>Part of the related analysis processes are similar, in the first aspect, since the shunt resistor 4 and the LED load 1 are in parallel relation, the magnitude of the resistance value R of the shunt resistor 4 is related to the operating voltage of the LED load 1, that is, the first specified operating voltage V of the LED load 11There is a relationship. It should be noted that the first predetermined operating voltage V of the LED load 1 defined in the embodiment of the present invention1And is not limited to the minimum prescribed operating voltage of the LED load 1, the first prescribed operating voltage V1The predetermined operating voltage of the LED load 1 under the normal dark lighting condition, that is, the lower operating voltage within the rated range, may also be the minimum predetermined operating voltage of the LED load 1. In the second aspect, since the value of the drive current output from the drive circuit 2 is theoretically equal to the sum of the value of the current component flowing through the LED load 1 and the value of the current component flowing through the shunt resistor 4, the resistance value of the shunt resistor 4 also has a relationship with the magnitude of the drive current output from the drive circuit 2.
It should be noted that, when the LED load 1 is under a condition of a predetermined operating voltage, for example, a lower operating voltage, if the resistance value R of the shunt resistor 4 is configured to be too large, the current component of the shunt resistor 4 at the lower operating voltage is too small, so that the shunt resistor 4 cannot effectively perform the function of shunting the LED load, and the current component of the LED load 1 is too large, so that the LED load 1 cannot meet the requirement of lower brightness, and unnecessary circuit loss is also caused. Thus, according to the first prescribed operating voltage V of the LED load 11 LED load 1 is in the second specificationOperating voltage V2Maximum drive current value I _, output by time drive circuit 2maxThe resistance value R of the shunt resistor 4 is configured and set in a correlated manner, so that the upper limit value of the shunt resistor 4 can be effectively selected and configured for the LED load 1, the circuit design is simplified on the premise of ensuring that the illumination brightness is lower, and unnecessary circuit loss is avoided.
It should be further noted that the resistance value R of the shunt resistor 4 satisfies the conditions of the following numerical expression (4) and numerical expression (5),
IR_min＝V1r, formula (4)
IR_min/I_max> X, formula (5)
In the formula, V1A first specified operating voltage, I, for the LED loadR_minTo maintain the LED load 1 at a first specified operating voltage V1The value of current flowing through the shunt resistor, I \umaxX is a specified value for the maximum driving current value output by the driving circuit.
From the above equation (4), it can be derived that when the LED load 1 is at the first predetermined operating voltage V1The current value I flowing through the shunt resistor 4R_min＝V1R; as is clear from the above equation (5), since the shunt resistor 4 is connected in parallel with the LED load 1, in order to make the LED load 1 meet the actual requirement of lower luminance, the shunt resistor 4 divides a part of the current component of the drive current, and the current value I \ "flowing through the shunt resistor 4RminLess than the maximum driving current value I _ofthe driving circuit 2maxThat is, the value of the current flowing through the shunt resistor 4 accounts for the maximum driving current value I _, which is outputted from the driving circuit 2maxIn a certain proportion. The larger the resistance value of the shunt resistor 4 is, the larger the value of the current I flowing through the shunt resistor 4R_minThe smaller the current component is, the smaller the value of the maximum drive current I _, which is output by the drive circuit 2maxThe smaller.
Therefore, the lower operating voltage of the LED load 1 is set as the first predetermined operating voltage V1And with reference to a first prescribed operating voltage V1And a maximum driving current value I _, which is outputted from the driving circuit 2maxThe resistance value of the shunt resistance 4 is set in association withR, the condition that the LED load 1 cannot meet the requirement of lower brightness due to the fact that the shunt resistor 4 cannot effectively play a role of shunting the LED load 1 because the shunt resistor 4 is too small in current component caused by too large configuration of the resistance value R of the shunt resistor 4 under the lower working voltage can be avoided. Meanwhile, the resistance R is configured too large, which also causes unnecessary circuit loss.
In the above embodiment, the resistance value R of the shunt resistor 4 is limited to be equal to at least the first predetermined operating voltage V of the LED load 11And the maximum driving current value I _ofthe driving circuit outputmaxThe satisfied condition relation is set in a correlated manner and further defined, and the upper limit of the resistance value R of the shunt resistor 4 is determined, so that the requirement of a user for adjusting the illumination brightness is met, and the experience of the user is further improved.
< other reference factors regarding the resistance value R of the shunt resistance 4 >
Based on the above-described embodiment, in the present embodiment, the signal generation circuit 3 is a PWM signal generation circuit, and the resistance value R of the shunt resistor 4 used in the control circuit of the LED lighting device according to the present invention is set in association with the duty ratio DR of the PWM dimming signal output from the signal generation circuit.
Specifically, in the prior art, when the duty ratio DR of the PWM dimming signal output by the signal generation circuit 3 is lower than a certain value, the light emission luminance of the LED load 1 cannot be further reduced due to the problem of the chip processing capability.
In the embodiment of the present invention, since the current flowing through the shunt resistor 4 is related to the driving current output by the driving circuit 2, and the driving current is related to the duty ratio DR of the PWM dimming signal output by the signal generating circuit 3, according to the above embodiment, the resistance value R of the shunt resistor 4 is set in association with the duty ratio DR of the PWM dimming signal output by the signal generating circuit 3, so that the current component borne by the shunt resistor 4 is adapted and matched to the driving current whose duty ratio DR of the PWM dimming signal is lower than a certain value, and thus, the LED load 1 can be adjusted to have lower brightness, and the experience of guiding and substituting for sleep aid of a user is improved.
In a preferred embodiment, the resistance R of the shunt resistor 4 is set under the condition that the duty ratio DR of the PWM dimming signal output from the signal generation circuit 3 is less than 2%; specifically, when the duty ratio DR of the PWM dimming signal output by the signal generating circuit 3 is less than 2% and the driving current of the driving circuit 2 cannot be further reduced, the resistance value R of the shunt resistor 4 is set in a correlated manner, so as to obtain the driving current transmitted by the driving circuit 2, and further make the current flowing through the two ends of the LED load 1 less than the driving current, thereby satisfying the requirement of the user for lower adjustment of the illumination brightness and further improving the experience of the user.
In a preferred embodiment, the resistance R of the shunt resistor is set under the condition that the duty ratio DR of the PWM dimming signal output from the signal generation circuit is less than 1%. Specifically, when the duty ratio DR of the PWM dimming signal output by the signal generating circuit 3 is less than 1% and the driving current of the driving circuit 2 cannot be further reduced, the resistance value R of the shunt resistor 4 is set in a related manner, so that the shunt resistor 4 divides the driving current supplied by the driving circuit 2, and the current flowing through the two ends of the LED load 1 is smaller than the driving current, thereby satisfying the requirement of the user for lower adjustment of the illumination brightness and further improving the experience of the user.
< specific determination regarding the above X, Y value >
According to the above embodiments, in one aspect, when determining the relevant parameters, the method comprises: lower limit of resistance value R of shunt resistor 4 and maximum drive current value I _ outputted from drive circuit 2maxA second predetermined operating voltage V of the LED load 12And a second predetermined operating voltage V at the LED load 12Current value I flowing through the shunt resistorR_maxThen, the value of the current flowing through the shunt resistor 4 can be determined to account for the maximum drive current value I _, which is outputted from the drive circuit 2maxThe ratio of (a) to (b) is less than a predetermined value, and the predetermined value is set to Y; in another aspect, where relevant parameters are determined, including: maximum drive current value I _, which is output from drive circuit 2maxFirst predetermined operating voltage V of LED load 11And a first predetermined operating voltage V at the LED load 11Current value I flowing through the shunt resistorR_minThen, the value of the current flowing through the shunt resistor 4 can be determined to account for the maximum drive current value I _, which is output from the drive circuit 2maxIf the ratio of (A) is greater than a predetermined value, the predetermined value is X.
The following is a specific example.
In one specific embodiment, a first defined operating voltage V of the LED load 112.4V, a second predetermined operating voltage V of the LED load 12The current value I _ \ "of the maximum drive current that the drive circuit 2 can output is 2.8VmaxWas 0.12A.
According to the formula (1), the resistance R selected by the shunt resistor 4 is larger than V2And I \ umaxThe ratio of the two is larger than (2.8/0.12) omega, and the integer is 24 omega;
according to the formula (2), the LED load 1 is at a second predetermined operating voltage V2Current value I flowing through the shunt resistor 4R_maxIs equal to V2(ii)/R, since R is greater than 24 Ω, is less than about 0.11667A;
according to the formula (3), Y has a value greater than IR_maxAnd I \ umaxDue to the ratio of IR_maxLess than 0.11667a, i.e., Y has a value greater than about 0.972, i.e., Y has a value no less than 0.972.
Therefore, as a preferred embodiment, the value of Y in the equation (3) is not less than 0.972.
According to equation (4), in order to achieve the low-luminance light-emitting effect, the driving circuit 2 adjusts the duty ratio of the PWM signal according to the PWM dimming signal to adjust the output driving current to 0.00119A, and the LED load 1 is set to the first predetermined operating voltage V1Under the condition of 2.4V, since the current flowing through the LED load 1 needs to be smaller than 0.0001A, the current value I flowing across the shunt resistor 4 is set to be the value of current IR_minIt needs to be greater than (0.00119-0.0001) A, i.e., 0.00109A.
According to the formula (5), when the LED load 1 is at the first predetermined operating voltage V1When the voltage is 2.4V, then IR_minAnd the maximum driving current value I _outputtedby the driving circuit 2maxThe ratio is greater than (0.00109/0.12), and is approximately equal to 0.0091, i.e., the value of X is not less than 0.0091.
Therefore, as a preferred embodiment, the value of X in expression (5) is not less than 0.0091.
The method of determining the upper limit and the lower limit of the resistance value of the shunt resistor 4 has been described above by way of example, and the resistance value R of the shunt resistor 4 may be appropriately selected between the upper limit and the lower limit, and is not particularly limited. The resistance value of the shunt resistor 4 actually arranged may be closer to the upper limit value or closer to the lower limit value.
In addition, it should be noted that the values of the above parameters are only used as an example; the example is only used for explaining the technical idea of the invention, and any parameter value adopted according to the technical idea of the invention and achieving the corresponding technical effect are within the protection scope of the invention and belong to the protection scope of the invention.
The foregoing description has described specific embodiments of the present invention. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes or modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention. The embodiments and features of the embodiments of the present application may be combined with each other arbitrarily without conflict.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.
The above description is only for the specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive various changes or substitutions within the technical scope of the present invention, and these should be covered by the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.

Claims (10)

1. A control circuit for an LED lighting device, having:
an LED load;
the output end of the driving circuit including the chip is connected with the LED load, and the driving circuit outputs driving current to drive the LED load to adjust light;
a signal generating circuit for outputting a dimming signal, the output terminal of which is connected to the driving circuit,
the LED driving circuit is characterized in that a shunt resistor connected with the LED load in parallel is further arranged.
2. The control circuit for an LED lighting device of claim 1, wherein:
the resistance value R of the shunt resistor is at least equal to a second specified operating voltage V of the LED load2The maximum driving current value I _, outputted by the driving circuitmaxAre set in a correlated manner, wherein the maximum drive current value I _maxIs corresponding to the second specified operating voltage V2The drive current value output by the drive circuit.
3. The control circuit for an LED lighting device of claim 2, wherein:
the resistance value R of the shunt resistor satisfies the conditions of the following numerical expressions (1), (2) and (3),
R＞V2/I_maxformula (1)
IR_max＝V2R, formula (2)
IR_max/I_max< Y, formula (3)
In the formula, V2A second predetermined operating voltage, I, for the LED loadR_maxFor the LED load to be at a second specified working voltage V2The value of current flowing through the shunt resistor, I \umaxTo correspond to said second specified operating voltage V2Y is a predetermined value.
4. The control circuit for an LED lighting device of claim 3, wherein:
the value of Y in the equation (3) is not less than 0.972.
5. The control circuit for an LED lighting device of claim 1, wherein:
the resistance value R of the shunt resistor is at least equal to the first specified operating voltage V of the LED load1And a maximum driving current value I _ \ output by the driving circuitmaxIs set in an associated manner, wherein the maximum drive current value I _maxIs a second specified operating voltage V corresponding to said LED load2The drive current value output by the drive circuit.
6. The control circuit for an LED lighting device of claim 5, wherein:
the resistance value R of the shunt resistor satisfies the following conditions of a numerical expression (4) and a numerical expression (5),
IR_min＝V1r, formula (4)
IR_min/I_max> X, formula (5)
In the formula, V1A first specified operating voltage, I, for the LED loadR_minTo be in the LED load is at a first specified operating voltage V1The value of current flowing through the shunt resistor, I \umaxFor a second prescribed operating voltage V corresponding to said LED load2When the maximum driving current value output by the driving circuit is X, the value is a specified value.
7. The control circuit for an LED lighting device according to claim 5,
the value of X in the formula (5) is not more than 0.0091.
8. The control circuit for an LED lighting device according to any one of claims 5 to 7,
the signal generating circuit is a PWM signal generating circuit, and the resistance value R of the shunt resistor is set in association with the duty ratio DR of the PWM dimming signal output from the PWM signal generating circuit.
9. The control circuit for an LED lighting device according to claim 8,
and the resistance value R of the shunt resistor is set under the condition that the duty ratio DR of the PWM dimming signal output by the PWM signal generating circuit is less than 2%.
10. The control circuit for an LED lighting device according to claim 9,
and the resistance value R of the shunt resistor is set under the condition that the duty ratio DR of the PWM dimming signal output by the PWM signal generating circuit is less than 1%.
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