CN112930005A - Light source driving method and circuit - Google Patents

Light source driving method and circuit Download PDF

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Publication number
CN112930005A
CN112930005A CN202110137987.1A CN202110137987A CN112930005A CN 112930005 A CN112930005 A CN 112930005A CN 202110137987 A CN202110137987 A CN 202110137987A CN 112930005 A CN112930005 A CN 112930005A
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light source
value
current
voltage
maximum
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CN112930005B (en
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徐建庆
吴海洋
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Suzhou HYC Technology Co Ltd
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Suzhou HYC Technology 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
    • 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
    • H05B47/105—Controlling the light source in response to determined parameters
    • H05B47/11—Controlling the light source in response to determined parameters by determining the brightness or colour temperature of ambient 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
    • 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]
    • 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

Abstract

The invention discloses a light source driving method, which comprises the steps of obtaining the maximum rated current value of a light source, calculating the maximum input voltage value according to the maximum rated current value and the resistance value of a current detection resistor, and setting the maximum input voltage as the output reference voltage, so that the value of the output voltage can be limited below the value of the maximum input voltage; meanwhile, the current received by the light source is the maximum rated current value because the maximum input voltage passes through the current detection resistor before being output to the light source. The maximum rated current value is determined by judging the numerical condition of the feedback voltage when the corresponding test current changes. According to the light source driving method provided by the invention, the maximum input voltage is adjusted according to the value of the maximum rated current, so that the light source driving method can adapt to different light source equipment and can adjust the light source between the off state and the maximum brightness all the time, and can ensure that the maximum input voltage is changed in time according to the property of the light source to prevent the light source from being damaged.

Description

Light source driving method and circuit
Technical Field
The invention relates to the field of electric light source control, in particular to a light source driving method and a light source driving circuit.
Background
At present, various light sources are widely applied to the field of machine vision detection, in the process of correspondingly adjusting different light sources in a machine vision system, due to the fact that rated currents of the different light sources are different, on one hand, under the actual operation environment, a light source driving device needs to drive the different light sources, if the driving current is not properly set, the result that the light sources work abnormally or even are damaged can be caused, and on the other hand, when the aged or damaged light sources are replaced, if the models are not matched, the maximum rated currents are different, the result that the light sources work abnormally can also occur.
In the light source driving method provided in the prior art, in order to make the maximum output current adjustable, two technical schemes are provided, one is a technical scheme of adding a parallel resistor as an identification sensor and equating the resistance value of the detected resistor to the rated current of the light source, and the other is a technical scheme of directly outputting the maximum voltage of 24V, so that most of light sources can be driven; however, the former increases the cost and is difficult to be compatible with other light source interfaces, and the latter cannot drive the electric light source and results in poor adjustment accuracy.
Disclosure of Invention
An objective of the present invention is to provide a light source driving method, which can solve the technical problems of unstable driving current and delayed response of the light source, and can prevent the low light source adjustment efficiency caused by excessive current or poor precision.
An object of the present invention is to provide a light source driving circuit.
To achieve one of the above objects, an embodiment of the present invention provides a light source driving method, including: obtaining the maximum rated current value of the light source by judging the value of the feedback voltage when the corresponding test current changes; calculating the value of the maximum input voltage according to the maximum rated current value and the current detection resistance value; and setting the maximum input voltage as the output reference voltage.
As a further improvement of an embodiment of the present invention, the method further comprises: controlling the brightness of the light source by adjusting the output voltage; wherein the value of the output voltage is 0V to the maximum input voltage value.
As a further improvement of an embodiment of the present invention, the obtaining a maximum rated current value of the light source by determining a value of the feedback voltage when the corresponding test current changes specifically includes: outputting a test current according to a preset current change rate after receiving a starting signal; obtaining the feedback voltage corresponding to the test current; and if the feedback voltage does not change along with the change of the test current or the feedback voltage reaches the maximum working voltage, taking the current value of the test current as the maximum rated current value.
As a further improvement of an embodiment of the present invention, the preset current change rate is configured such that the value of the test current is gradually increased with time.
As a further improvement of an embodiment of the present invention, the start signal is a light source access signal.
In order to achieve one of the above objectives, an embodiment of the present invention provides a light source driving circuit, which includes a main control module, a first parameter setting module, and a second parameter setting module; the main control module is used for obtaining the maximum rated current value of the light source by judging the numerical condition of the feedback voltage when the corresponding test current changes, and calculating the maximum input voltage value according to the maximum rated current value and the current detection resistance value; and the first parameter setting module is used for setting the maximum input voltage value as the output reference voltage.
As a further improvement of an embodiment of the present invention, the light source driving circuit further includes: the second parameter setting module is used for controlling the brightness of the light source by adjusting the output voltage; wherein the value of the output voltage is 0V to the maximum input voltage value.
As a further improvement of an embodiment of the present invention, the light source driving circuit further includes a constant current driving module, configured to receive the maximum input voltage and output the maximum rated current to a rear end.
As a further improvement of the embodiment of the present invention, the main control module is connected to the first parameter setting module and the second parameter setting module through serial buses, respectively, an output end of the first parameter setting module is connected to a reference voltage input end of the second parameter setting module, and an output end of the second parameter setting module is connected to the constant current driving module.
As a further improvement of an embodiment of the present invention, the light source driving circuit further includes a parameter detection module, configured to obtain values of the test current and the feedback voltage and output the values to the main control module.
Compared with the prior art, the maximum input voltage is adjusted according to the value of the maximum rated current, so that the light source control circuit can adapt to different light source devices and can adjust the light source between the off state and the maximum brightness all the time, and can ensure that the maximum input voltage is changed in time according to the property of the light source to prevent the light source from being damaged.
Drawings
FIG. 1 is a schematic diagram of a lighting system in one embodiment of the present invention;
FIG. 2 is a schematic diagram of a light source driving circuit according to an embodiment of the present invention;
fig. 3 is a schematic diagram of the structure and connection of the constant current driving module and the parameter detecting module according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of one embodiment of a method for driving a light source in accordance with one embodiment of the present invention;
FIG. 5 is a schematic diagram of another embodiment of a method of driving a light source in accordance with an embodiment of the present invention;
fig. 6 is a schematic diagram of a light source driving method according to still another embodiment of the present invention.
Detailed Description
The present invention will be described in detail below with reference to specific embodiments shown in the drawings. These embodiments are not intended to limit the present invention, and structural, methodological, or functional changes made by those skilled in the art according to these embodiments are included in the scope of the present invention.
It is to be noted that the term "comprises," "comprising," or any other variation thereof is intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Furthermore, the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In an embodiment of the present invention, as shown in fig. 1, a light source apparatus 100 is provided, which is applied in the field of artificial intelligence, especially in a machine vision system.
The machine vision system mainly operates a machine to perform related actions by detecting and identifying external information, and particularly, the machine vision system combines the technologies of image processing, pattern recognition and the like to replace human eyes to perform various measuring and judging technical effects. The main function of the light source device 100 is to provide suitable lighting conditions under dim light conditions, thereby creating a suitable environment for machine vision systems or other field operations.
The light source device 100 includes a light source 1 and a light source driving device 2. In actual operation, the light source driving device 2 is connected with a power supply and then drives the light source 1 connected with the power supply to emit light, so that a proper light environment is provided for activities such as industrial production and the like.
Specifically, the light source driving device 2 receives electric energy such as commercial power and converts the electric energy into electric energy suitable for the light source 1 to receive, thereby driving the light source 1 to emit light. The light source 1 may be any type of light source that needs to be driven by the light source driving device 2, such as a metal halide lamp, a high-pressure sodium lamp, or an LED lamp. In this embodiment, the light source 1 is an LED lamp, and a plurality of light sources are arranged on the panel, but in other embodiments, the light source 1 may also be a light emitting device with only a single lamp bead, and can also form the light source apparatus 100 provided by the present invention; the light source driving device 2 is connected to at least one light source 1 for controlling the light source 1, so that the light intensity, the off intensity and the brightness of the light source 1 can be adjusted according to the user's requirement.
The light source driving device 2 includes a light source driving circuit 20 and a carrying structure for carrying the light source driving circuit 20. The carrying structure is not limited in the present invention, and may be a single-sided, double-sided, or multi-layer printed circuit board, or other substrate structure capable of carrying the light source driving circuit 20, and the present invention is not limited in the arrangement of other components of the light source driving device 2.
Further, in the embodiment of the present invention, the light source driving circuit 20 mainly obtains the maximum rated current value of the light source 1, and outputs the maximum input voltage after calculating the maximum input voltage value according to the maximum rated current value and the current detection resistor resistance value, because the maximum input voltage passes through the current detection resistor before being output to the light source 1, the current received by the light source is the maximum rated current value, and thus the light source 1 can obtain the maximum driving current to achieve the maximum brightness. To meet the above-mentioned idea, the hardware structure of the light source driving circuit 20 is configured as follows:
as shown in fig. 1 and 2, the light source driving circuit 20 generally includes a main control module 3 and a light source interface 6, wherein the light source interface 6 is electrically connected to the light source 1, so that analog signals such as voltage and current of the light source interface 6 can be controlled by the main control module 3, thereby controlling the light source 1 to perform corresponding actions.
In the present invention, the light source driving circuit 20 is further provided with a first parameter setting module 51. Specifically, the first parameter setting module 51 is electrically connected to the main control module 3, converts and outputs the digital signal fed back by the main control module 3, and sets the maximum input voltage value as the output reference voltage, and accordingly, the main control module 3 obtains the maximum rated current value of the light source by judging the numerical condition of the feedback voltage when the corresponding test current changes, and calculates the maximum input voltage value according to the maximum rated current value and the current detection resistance value.
The light source driving circuit 20 further includes a second parameter setting module 52 electrically connected to the first parameter setting module 51, and configured to control the brightness of the light source by adjusting the output voltage; wherein the value of the output voltage is 0V to the maximum input voltage value. Thus, the above-described design concept of the present invention can be achieved.
Specifically, the main control module 3 outputs parameters to the first parameter setting module 51, the first parameter setting module 51 outputs corresponding analog signals according to the parameters and the conversion to set a reference voltage for the second parameter setting module 52, and the second parameter setting module 52 outputs the analog signals under the limitation of the reference voltage. In this embodiment, the analog signal is a voltage, and the parameter output by the main control module 3 is converted according to the maximum rated current obtained by the analog signal, so that the range of the output voltage of the second parameter setting module 52 is adjustable between 0V and the value of the maximum input voltage.
As shown in fig. 2, the light source driving circuit 20 provided in the present invention further includes a constant current driving module 4 for constantly outputting a current to the light source interface 6, wherein the constant current driving module 4 is configured to receive a maximum input voltage and output a maximum rated current to the rear end according to the maximum input voltage.
It should be understood that the technical solution provided by the present invention aims to enable the light source driving circuit 20 to adjust the output maximum current to be equal to the maximum rated current of the light source 1 according to different light sources 1, and to adjust the brightness of the light source 1 by controlling the constant current driving module 4 to output a current smaller than the maximum rated current, so that the maximum rated current is actually the maximum threshold of the output current of the constant current driving module 4, and the output current of the constant current driving module 4 should be adjustable between 0A and the maximum rated current in the embodiment provided by the present invention. In order to achieve the above technical effects, the second parameter setting module 52 is electrically connected to the main control module 3, so that the magnitude of the output voltage of the parameter setting module 52 is adjusted by the main control module 3, and the driving current output by the constant current driving module 4 is controlled to be adjustable within a range smaller than the maximum rated current.
For the hardware aspect of the above structure, the main control module 3 is connected to the first parameter setting module 51 and the second parameter setting module 52 through the serial bus, so that the main control module 3 can stably transmit synchronization signals or data such as time to the first parameter setting module 51 and the second parameter setting module 52, and the constant current driving module 4 is electrically connected between the output end of the second parameter setting module 52 and the light source interface 6.
It should be noted that the arrangement of the modules is only for the purpose of illustration of functional distinction, and does not mean that the modules are independent from each other in an actual circuit, for example, in an embodiment, the light source interface 6 and the constant current driving module 4 may be integrally arranged. For the specific type of the module, in this embodiment, the main control module 3 is an embedded single chip microcomputer, and the first parameter setting module 51 and the second parameter setting module 52 are both digital-to-analog converters, and are configured to convert digital signals transmitted from the main control module 3 serving as the embedded single chip microcomputer into analog signals, and finally output the analog signals to the back-end device. Of course, the first parameter setting module 51 and the second parameter setting module 52 may also be other parameter setting modules capable of performing digital-to-analog conversion and parameter setting and achieving corresponding functions in the present invention.
Continuing with fig. 2, the light source driving circuit 20 further includes a connection and disconnection module 8 for detecting an external condition of the light source interface 6, and the connection and disconnection module 8 is electrically connected to the main control module 3 and the light source interface 6, respectively. So as to feed back the external connection condition of the light source interface 6 to the main control module 3. Specifically, after the light source 1 is connected to the circuit through the light source interface 6, the connection and disconnection module 8 generates a light source connection signal and sends the signal to the main control module 3, and the main control module 3 correspondingly controls the constant current driving module 4 to act after receiving the light source connection signal. In the present embodiment, the disconnection module 8 always scans the external connection condition of the light source interface 6 by using a low-frequency bandwidth pulse technology, and generates a high-level signal as a light source access signal to be transmitted to the main control module 3 when the light source interface 6 has light source access; when no light source is accessed, a low level signal is generated. Of course, in other embodiments, the disconnection module 8 has other configurations, and the invention is not limited thereto.
It is to be noted that the disconnection module 8 is also provided as a functional distinction only and independently of the other modules, and in terms of physical hardware arrangement, the disconnection module 8 may be integrated with the light source interface 6 in one embodiment, as well as being able to achieve its intended technical effect.
Further, the light source driving circuit 20 further includes a parameter detection module 7 for detecting voltage and current values at two ends of the light source interface 6, and an output end of the parameter detection module 7 is electrically connected to the main control module 3 to feed back an obtained signal to the main control module 3. In this embodiment, the signals are a test current and a feedback voltage.
As for the specific structure of the parameter detection module 7, as shown in fig. 3, the parameter detection module 7 includes a current detection resistor 71 for detecting the current passing through the light source interface 6, wherein the current detection resistor 71 is connected in series with the light source interface 6. With such a configuration, the parameter detection module 7 can output the test voltage to the main control module 3 by detecting the test voltage at the two ends of the current detection resistor 71, and the main control module 3 combines the resistance value of the current detection resistor 71 to calculate and obtain the test current corresponding to the test voltage, thereby obtaining the output current condition of the power interface 6. Since the single resistor has stable properties, it is a good electronic component for detecting circuit current, and certainly, it cannot be regarded as a technical feature that limits the protection scope of the present invention.
Further, in order to reduce the loss of the driving current and the power consumption, in the present embodiment, the resistance value of the current detection resistor 71 is set to be small as in the common practice, but the amplitude of the voltage signal detected correspondingly is also small, and the driving capability is weak; to avoid the following problems: firstly, the error of the current value calculated according to the voltage signal with smaller amplitude is larger, which can cause the whole adjustment failure of the light source driving circuit 20; the parameter detection module 7 is connected with the main control module 3 at a certain distance, and the signal anti-interference capability is weak due to small driving force; the parameter detection module 7 according to the present embodiment is further provided with a differential amplifier circuit 72. The input end of the differential amplifying circuit 72 is connected to both ends of the current detecting resistor 72, and the output end is connected to the main control module 3. Thus, the test voltage is received, differentially amplified and then output to the main control module 3.
Further, as shown in fig. 3, in the present embodiment, the constant current driving module 4 is also provided with a current detection pin 42 connected to two ends of the current detection resistor 71 to detect the current passing through the current detection resistor 71, so that the constant current driving module 4 can obtain a feedback signal of the output driving current, and accordingly perform adaptive adjustment. It is understood that there are various embodiments of the principle that the current detection pin 42 detects the magnitude of the current passing through the current detection resistor 71, and in the present embodiment, the current detection pin 42 detects the voltage across the current detection resistor 71 and then performs an operation to obtain the current value of the current detection resistor 71.
Further, the constant current driving module 4 further includes a voltage reduction circuit 41 connected to the current detection resistor 71, and the voltage reduction circuit 41 is provided to further improve the efficiency of the constant current driving module 4 as compared to a simple linear power supply by using it as a switching power supply.
In addition, in the present embodiment, since the light source 1 is an LED lamp, and a plurality of lamp beads are disposed thereon, as for the light source driving circuit 20, a plurality of light source interfaces 6 corresponding to the lamp beads may be disposed, and the second parameter setting module 52, the constant current driving module 4, and the parameter detecting module 7 are respectively disposed in a group corresponding to each light source interface 6. When the light sources 1 are all set by the same light source model, one first parameter setting module 51 can be configured for the same light source 1, namely, the same first parameter setting module 51 corresponds to a plurality of second parameter setting modules 52 and the like, and the same maximum output current threshold value is set for the same first parameter setting module 51, so that the overall setting of the circuit can be simplified, and simultaneously, a scheme that a user respectively adjusts the light emitting state of one or a group of lamp beads through the plurality of second parameter setting modules 52 can be provided.
Of course, in other embodiments, when the light sources 1 are only arranged in a single or single group, the first parameter setting module 51 and the second parameter setting module 52, the constant current driving module 4, and the light source interface 6 may be controlled in a group corresponding to each other.
Further, in order to achieve the expected technical effects of the present invention, in cooperation with the above hardware structure, the present invention provides a light source driving method, which implements a technical scheme that a maximum rated current value is obtained by the main control module 3 by configuring the main control module 3, the first parameter setting module 51 and the second parameter setting module 52, and after data conversion is performed by the first parameter setting module 51 and the second parameter setting module 52, the second parameter setting module 52 outputs a maximum input voltage corresponding to the maximum rated current value, as shown in fig. 4, the method includes an implementation manner:
and step 91, acquiring the maximum rated current value of the light source by judging the numerical condition of the feedback voltage when the corresponding test current changes.
As for the components in the circuit, because the impedance value is determined by the self type and the property of the components, the circuit property can be observed only through the current and the voltage on the components, and particularly when the components are electrified with the current which is more than or equal to the rated current value, the abnormal condition of the self property and the current-voltage relation can be caused inevitably, so the implementation mode provided by the invention is that the corresponding relation is judged by detecting the test current passing through the components and the feedback voltage at the two ends of the components, thereby obtaining the maximum rated current value.
The maximum rated current value is a maximum current allowed to pass through by the light source under a normal working condition and can emit maximum brightness under the current according to general understanding, and in the prior art, the output driving current cannot be correspondingly adjusted according to different maximum rated currents of different light sources 1 so as to enable the light sources 1 to reach the maximum brightness, so that in the light source driving method provided in the embodiment, before the light sources 1 are driven to emit light, the main control module 3 judges the feedback voltage from the light sources 1 and the numerical conditions when the testing current changes, and performs related operations, so that the maximum rated current value is obtained to adapt to light sources of different models.
And step 92, calculating the value of the maximum input voltage according to the maximum rated current value and the current detection resistance value.
Since in this embodiment, the main control module 3 controls the rear end device to emit current by controlling the first parameter setting module 51 and the second parameter setting module 52 to output voltage, and particularly controls the constant current driving module 4 to constantly output the maximum rated current to the light source interface 6, at this time, the maximum input voltage value output from the second parameter setting module 52 to the constant current driving module 4 corresponding to the maximum rated current should be calculated by the main control module 3 in combination with the resistance value of the electronic device connected to the output terminal of the constant current driving module 4 and used for detecting current, that is, the resistance value of the current detecting resistor 71 set in the parameter detecting module 7 in this embodiment. Of course, in other embodiments, other configurations exist that achieve the above technical effects as well.
In this embodiment, in combination with the above component configuration, when the circuit is in full-load operation, since the voltage input to the constant current driving module 4 is the maximum input voltage, the current output from the output terminal to the light source interface 6 through the current detection resistor 71 after the constant current driving module 4 receives the maximum input voltage is the maximum rated current, in other words, the voltage at two ends of the current detection resistor 71 is the maximum input voltage to be calculated, and the resistance value passing through the current detection resistor 71 is the maximum rated current, according to ohm's law, the value of the maximum input voltage is equal to the product of the maximum rated current value and the resistance value of the current detection resistor, so that the value of the maximum input voltage can be calculated, and in an embodiment where the light source driving circuit 20 has other circuit structures, there are other operational relationships between the maximum input voltage value and the maximum rated current.
Step 93, setting the maximum input voltage as the output reference voltage.
After the maximum input voltage value is calculated, the maximum input voltage is set as a reference voltage to control the values of the subsequent output voltage and the driving current to be respectively not more than the values of the maximum input voltage and the maximum rated current.
In combination with the above arrangement of the components of the light source driving circuit 20, the main control module 3 converts the maximum input voltage value into a first parameter and transmits the first parameter to the first parameter setting module 51, the first parameter setting module 51 converts the first parameter into a second parameter and transmits the second parameter to the second parameter setting module 52, and the second parameter setting module 52 combines the second parameter and outputs a third parameter to the rear end. Further, in the present embodiment, since the first parameter setting module 51 and the second parameter setting module 52 are both digital-to-analog converters, the first parameter is a digital signal, the second parameter and the third parameter are both analog signals, more specifically, the analog signal is a voltage, and after the main control module 3 calculates the maximum input voltage value, since the main control module 3 generally cannot output such a large voltage, after the main control module 3 converts the value and transmits the value to the first parameter setting module 51, the first parameter setting module 51 outputs the maximum input voltage to the second parameter setting module 52.
Of course, in other embodiments, the first parameter setting module 51 may be integrated with the main control module 3, so as to form a situation that the main control module 3 directly outputs the maximum input voltage, but it should be understood that it is essentially no different from the embodiment provided by the present invention, and thus still belongs to the protection scope of the present invention; meanwhile, if the circuit is configured to operate at full load, the first parameter setting module 51 and the second parameter setting module 52 are considered as an integral, and it can also be considered that the main control module 3 finally outputs the maximum input voltage through the second parameter setting module 52.
In one embodiment, as shown in fig. 5, the present invention further comprises:
step 94, controlling the brightness of the light source by adjusting the output voltage; wherein the value of the output voltage is 0V to the maximum input voltage value.
The main control module 3 controls the constant current driving module 4 to output the driving current to the light source 1 by adjusting the output voltage of the second parameter setting module 52, so as to control the brightness of the light source 1; the value of the output voltage is 0V to the maximum input voltage value, and correspondingly, the value of the driving current received by the light source 1 is 0A to the maximum rated current value, namely, the light source 1 can be adjusted in the range from being extinguished to the maximum brightness.
To further explain the above control process, in the configuration of the light source driving circuit 20 provided in this embodiment, let the first parameter be n, the signal transmitted by the main control module 3 connected to the second parameter setting module 52 through the serial bus to adjust the brightness of the light source 1 from being extinguished to the maximum brightness be the fourth parameter m, the number of bits of the first parameter setting module 51 and the second parameter setting module 52 is x, the maximum input voltage is Umax, the preset reference voltage of the first parameter setting module 51 is Uref1, the reference voltage of the second parameter setting module 52 is Uref2, the voltage output by the first parameter setting module 51 is also the second parameter U1, and the voltage output by the second parameter setting module is also the third parameter U2.
Then, atIn the above-mentioned embodiment in which the first parameter setting module 51 and the second parameter setting module 52 are both digital-to-analog converters, according to the property of the digital-to-analog converters: the output analog signal Uout is equal to the received digital signal n and the digital-to-analog converter addressability 2xThe product of the ratio of (d) to the reference voltage Uref, i.e.
Figure BDA0002927495090000111
Therefore, after the main control module 3 obtains the maximum input voltage value, according to the formula:
Figure BDA0002927495090000112
the first parameter n is obtained through calculation, and is output to the first parameter setting module 51 through the serial bus, and then the first parameter setting module 51 outputs the second parameter U1 according to the following formula:
Figure BDA0002927495090000113
that is, the second parameter U1 is practically equivalent to the value of the maximum input voltage Umax, so designed, as mentioned above, because the main control module 3 is usually unable to output the voltage of the maximum input voltage Umax, so as to set the reference voltage Uref2 for the second parameter setting module 52, the first parameter setting module 51, which is required to be fixed by the reference voltage Uref1, is equivalent to a variable reference voltage source that can respond according to the nature of the light source 1, thereby achieving the same effect. Further, after the second parameter setting module 52 receives the reference voltage Uref2 set by the first parameter setting module 51 and the fourth parameter m set by the main control module 3, the third parameter U2 is output as:
Figure BDA0002927495090000114
thus, since the number x of bits and the maximum input voltage Umax are fixed, the main control module 3 can further control the size of the third parameter U2 by adjusting the size of the fourth parameter m. Theoretically, the value of the fourth parameter m should be in the range of 0 to 2xThereby achieving that the light source 1 is adjustable over the whole range. The number of the additional digits x is determined by the specific type of the first parameter setting module 51 or the second parameter setting module 52, the number x is 12 in this embodiment, and may be 16 or other numbers in other embodiments.
As described above, the main control module 3 is configured to fully achieve the purpose of the light source driving method provided by the present invention: on one hand, the value of the maximum input voltage Umax can be adjusted according to the condition of the light source 1; on the other hand, when the fourth parameter m and the bit number x are fixed, the value of the maximum input voltage Umax directly determines the value of the third parameter U2, and since the driving current output by the constant current driving module 4 is determined by the third parameter U2, which is equivalent to the driving current determined by the maximum input voltage Umax, at this time, if the fourth parameter m is adjusted by one unit, the variation Δ U2 of the third parameter U2 is:
Figure BDA0002927495090000121
in order to achieve the maximum variation of the third parameter U2, the reference voltage Uref2 of the second parameter setting module 52 needs to be adjusted to the maximum value without damaging the light source 1, so the corresponding maximum input voltage Umax needs to be converted according to the maximum rated current of the light source 1, so as to achieve the technical effect of the finest precision adjustment range.
Further, as shown in fig. 6, in the present embodiment, the adjustment process of step 91 is refined, and a more specific embodiment is provided as follows:
step 911, after receiving the start signal, outputting the test current according to a preset current change rate.
Specifically, the main control module 3 adjusts the constant current driving module 4 to increase the test current output to the light source interface 6 by sequentially controlling the first parameter setting module 51 and the second parameter setting module 52, or by directly controlling the second parameter setting module 52 according to a certain current change rate. In the embodiment where the main control module 3 regulates the current through the first parameter setting module 51 and the second parameter setting module 52, the fourth parameter m given by the main control module 3 to the second parameter setting module 52 should satisfy:
m＝212；
thus, the third parameter U2 output by the second parameter setting module 52 can be always equal to the reference voltage Uref2, that is, always equal to the second parameter U1, so that the main control module can synchronously adjust the third parameter U2 by adjusting the first parameter n, and of course, the main control module 3 can also directly control the second parameter setting module 52 through the serial bus, and at this time, the first parameter n given by the main control module 3 to the first parameter setting module 51 should also satisfy:
n＝212；
this ensures that the second parameter U1, which is output by the first parameter setting module 51 and sets the reference voltage Uref2 for the second parameter setting module 52, remains maximum, enabling the second parameter setting module 52 to adjust within the full addressability range. Therefore, the present invention is not limited to the control method. Meanwhile, it should be noted that the above calculation formula is given based on the configuration of the first parameter setting module 51 and the second parameter setting module 51 as digital-to-analog converters with 12 bits, in other embodiments, the number of bits of the digital-to-analog converters may be other values, and the number of bits of the first parameter setting module 51 and the second parameter setting module 52 is not necessarily equal, which is not limited in the present invention.
For the start signal, in this embodiment, the connection disconnection module 8 always scans the external connection condition of the light source interface 6, and correspondingly generates a light source access signal to be directly output to the main control module 3, so that the light source access signal is the start signal. However, in other embodiments, if the disconnection module 8 and the light source interface 6 are separately provided, and the disconnection module 8 is not configured to always scan the light source interface 6, such as a low-frequency bandwidth pulse technique, the signal sent by the light source interface 6 to the disconnection module 8 is defined as a light source connection signal, and is distinguished from the start signal.
Step 912, obtaining a feedback voltage corresponding to the test current;
step 913, if the feedback voltage does not change with the change of the test current, or if the feedback voltage reaches the maximum working voltage, the value of the test current at this time is obtained as the maximum rated current value.
Because ohm's law is only strictly suitable for pure resistance circuit, and for the circuit containing light source, under the condition of continuously increasing current, even if the light source 1 has reached the maximum rated current, if the light source continues to output, the voltage at two ends of the light source 1 will still be increased, but the increased amplitude and speed will be decreased, so the invention utilizes the characteristic of the light source, while continuously increasing the magnitude of the test current, correspondingly receives the feedback voltage of the light source 1, and when detecting that the feedback voltage does not correspondingly change along with the change of the test current, obtains the test current at the moment as the maximum rated current.
Further, because the existing light source is in the national standard, no matter what light source has an upper limit of working voltage, namely the maximum working voltage, under the condition that the test current is continuously increased until the voltage on the two sides of the light source 1 reaches the maximum working voltage, but the feedback voltage is still correspondingly increased along with the increase of the test current, the current passing through the light source 1 can be also determined to be the maximum rated current under the state of the maximum working voltage. More specifically, in the present embodiment, the maximum operating voltage is 24V, but in other embodiments, the operating voltage has other values, and the present embodiment provides the value for reference only, and the value is not considered to limit the protection scope of the present invention.
As described above, in the present embodiment, two methods for determining whether the value of the test current has reached the maximum rated current value of the current light source are provided, one is to detect whether the feedback voltage changes synchronously with the change of the test current, and the other is to detect whether the feedback voltage reaches the maximum operating voltage. The two methods are both established on the premise that the preset current change rate is configured to gradually increase the test current with time, but the embodiment provided by the invention is not limited to this configuration method, and any technical scheme capable of achieving the purpose of the invention and utilizing the two embodiments to detect the maximum rated current falls within the protection scope of the invention.
Step 92, calculating the value of the maximum input voltage according to the maximum rated current value and the current detection resistance value;
step 93, set the maximum input voltage as the output reference voltage.
Likewise, this embodiment may also include:
step 94, controlling the brightness of the light source by adjusting the output voltage; wherein the value of the output voltage is 0V to the maximum input voltage value.
In summary, the present invention provides a light source driving method and circuit, wherein the method comprises the following steps:
1. after the light source 1 is connected to the light source interface 6 and the connection and disconnection module 8 detects that the light source is connected, a high level is output to the main control module 3 as a starting signal;
2. the main control module 3 directly or through the first parameter setting module 51 controls the second parameter setting module 52 to continuously increase the third parameter U2 output to the constant current driving module 4, and correspondingly, the constant current driving module 4 outputs the test current to the light source interface 6;
3. the main control module 3 is connected with the current detection resistor 71 and receives the feedback voltage, meanwhile, the voltage at two ends of the current detection resistor 71 is amplified by the differential amplification circuit 72 and then output to the main control module 3, and the main control module 3 calculates the test current passing through the current detection resistor 71 according to the amplified voltage and the resistance value of the current detection resistor 71;
4. when the feedback voltage is not increased along with the increase of the test current value or the feedback voltage reaches 24V, the main control module 3 acquires the test current at the moment as the maximum rated current;
5. the main control module 3 calculates a maximum input voltage value Umax by combining the maximum rated current value and the resistance value of the current detection resistor 71, and calculates a first parameter n correspondingly output to the first parameter setting module 51 according to the maximum input voltage value Umax;
6. the first parameter setting module 51 outputs a second parameter U1 to the reference voltage input terminal of the second parameter setting module 52 according to the first parameter n, and sets a reference voltage for the first parameter n, wherein the second parameter U1, the reference voltage Uref2 of the second parameter setting module 51 and the maximum input voltage Umax are consistent in value;
7. the main control module 3 outputs a fourth parameter m to the second parameter setting module 52, and the second parameter setting module 52 correspondingly outputs a third parameter U2 to the constant current driving module 4 according to the second parameter U1 and the fourth parameter m, wherein the fourth parameter m is within the range of 0-2 of the addressing capability of the second parameter setting module 5212The third parameter U2 corresponding to the fourth parameter m is synchronously changed from zero to the second parameter U2;
8. the constant current driving module 4 outputs a driving current to the light source interface 6 and the light source 1 according to the third parameter U2, and the driving current is also changed synchronously with the fourth parameter m and the third parameter U2, so that the full-range adjustment of the light source brightness degree is realized.
Therefore, the maximum input voltage is adjusted according to the value of the maximum rated current, so that the light source control circuit can adapt to different light source equipment and can adjust the light source between the off state and the maximum brightness all the time, and can ensure that the maximum input voltage is changed in time according to the property of the light source to prevent the light source from being damaged.
It should be understood that although the present description refers to embodiments, not every embodiment contains only a single technical solution, and such description is for clarity only, and those skilled in the art should make the description as a whole, and the technical solutions in the embodiments can also be combined appropriately to form other embodiments understood by those skilled in the art.
The above-listed detailed description is only a specific description of a possible embodiment of the present invention, and they are not intended to limit the scope of the present invention, and equivalent embodiments or modifications made without departing from the technical spirit of the present invention should be included in the scope of the present invention.

Claims (10)

1. A light source driving method, comprising:
obtaining the maximum rated current value of the light source by judging the value of the feedback voltage when the corresponding test current changes;
calculating the value of the maximum input voltage according to the maximum rated current value and the current detection resistance value;
and setting the maximum input voltage as the output reference voltage.
2. The light source driving method according to claim 1, further comprising:
controlling the brightness of the light source by adjusting the output voltage; wherein the value of the output voltage is 0V to the maximum input voltage value.
3. The light source driving method according to claim 1, wherein the obtaining the maximum rated current value of the light source by determining the value of the feedback voltage when the corresponding test current changes comprises:
outputting a test current according to a preset current change rate after receiving a starting signal;
obtaining the feedback voltage corresponding to the test current;
if the feedback voltage does not vary with the test current, or
And when the feedback voltage reaches the maximum working voltage, taking the current value of the test current as the maximum rated current value.
4. The light source driving method according to claim 3, wherein the preset current change rate is configured such that the value of the test current is increased stepwise with time.
5. The light source driving method according to claim 3, wherein the start signal is a light source access signal.
6. A light source driving circuit, characterized in that the light source driving circuit (20) comprises:
the main control module (3) is used for obtaining the maximum rated current value of the light source by judging the numerical condition of the feedback voltage when the corresponding test current changes, and
calculating a maximum input voltage value according to the maximum rated current value and the current detection resistance value;
and the first parameter setting module (51) is used for setting the maximum input voltage value as the output reference voltage.
7. The light source driving circuit according to claim 6, wherein the light source driving circuit (20) further comprises:
the second parameter setting module (51) is used for controlling the brightness of the light source by adjusting the output voltage; wherein the value of the output voltage is 0V to the maximum input voltage value.
8. The light source driving circuit according to claim 7, wherein the light source driving circuit (20) further comprises:
and the constant current driving module (4) is used for receiving the maximum input voltage and outputting the maximum rated current to the rear end.
9. The light source driving circuit according to claim 8, wherein the main control module (3) is respectively connected to the first parameter setting module (51) and the second parameter setting module (52) through a serial bus, an output terminal of the first parameter setting module (51) is connected to a reference voltage input terminal of the second parameter setting module (52), and an output terminal of the second parameter setting module (52) is connected to the constant current driving module (4).
10. The light source driving circuit according to claim 6, wherein the light source driving circuit (20) further comprises:
and the parameter detection module (7) is used for acquiring the values of the test current and the feedback voltage and outputting the values to the main control module (3).
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Publication number Priority date Publication date Assignee Title
JP2005252211A (en) * 2004-03-05 2005-09-15 Nippon Precision Circuits Inc Led luminance adjustment circuit
CN1815542A (en) * 2005-02-02 2006-08-09 三星电子株式会社 Led driver circuit
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