CN108112129B - LED constant current driving circuit - Google Patents
LED constant current driving circuit Download PDFInfo
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- CN108112129B CN108112129B CN201810022284.2A CN201810022284A CN108112129B CN 108112129 B CN108112129 B CN 108112129B CN 201810022284 A CN201810022284 A CN 201810022284A CN 108112129 B CN108112129 B CN 108112129B
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
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- 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
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- 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
- Y02B20/30—Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]
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Abstract
The application provides an LED constant current driving circuit, comprising: the LED lamp comprises a constant current control module, a constant voltage control module, a first current limiting circuit, a triode switch and an LED module; the output end of the constant voltage control module is connected with the constant current control end of the constant current control module, the input end of the constant current control module is connected with the input end of the constant current control module, and the output end of the constant current control module is connected with a low-voltage point; the LED module comprises a first current limiting circuit, a triode switch and an LED module, wherein the first current limiting circuit, the triode switch and the LED module are sequentially connected in series, the collector of the triode switch is connected with the anode of the LED module, the emitter of the triode switch is connected with the output end of the first current limiting circuit, the base of the triode switch is connected with the constant current control end of the constant current control module, the input end of the first current limiting circuit is connected with the input end of the constant current control module, and the cathode of the LED module is connected with a low-voltage point; the triode switch works in a saturation region or an amplifying region, the LED module is lightened, and the constant voltage module clamps the pressure difference between two ends of the first current limiting circuit to enable the current of the first current limiting circuit to be stable, so that the constant driving current of the LED is kept.
Description
Technical Field
The application relates to the technical field of LEDs, in particular to an LED constant current driving circuit.
Background
Light emitting diodes (Light Emitting Diode, simply LED) are widely used in the field of new energy-saving light sources with high efficiency, high integration and long lifetime. When the forward voltage is smaller than the threshold value, the current is extremely small, and the LED does not emit light; when the voltage exceeds the threshold, the forward current increases rapidly with the voltage and the LED emits light.
Common LED assemblies include current limiting resistors, triode switches, and LEDs. Since LEDs are constant current devices, in existing LED driving schemes, a constant current source is typically used to supply power to the LED assembly, and the driving voltage of the constant current source is typically required to be greater than the sum of the transistor switch base-emitter voltage threshold (e.g., 0.7V) and the LED voltage threshold (e.g., 1.8V).
However, since the output of the power supply is not usually a fixed voltage value, but an output voltage range (e.g., 2-5V) having a highest output voltage value and a lowest output voltage value, in the conventional driving process, there is a problem that the lowest voltage supplied by the power supply is close to or less than the required voltage (0.7+1.8=2.5V) of the LED assembly, and the current of the LED is very sensitive to the voltage variation, thereby easily causing unstable or reduced brightness of the LED.
Disclosure of Invention
The application provides an LED constant-current driving circuit which provides constant-current and constant-voltage power supply for an LED so as to enable the LED to stably emit light.
According to a first aspect of the present application, there is provided an LED constant current drive circuit comprising: the constant current control module, the constant voltage control module, the first current limiting circuit, the triode switch and the Light Emitting Diode (LED) module;
the output end of the constant voltage control module is connected with the constant current control end of the constant current control module, the input end of the constant current control module is connected with the input end of the constant current control module, the input end of the constant current control module is also connected with a power supply, the output end of the constant current control module is connected with a low potential point, and the constant voltage control module is used for keeping the voltage values of two ends constant when the current of the two ends is unchanged;
the first current limiting circuit, the triode switch and the LED module are sequentially connected in series, the collector electrode of the triode switch is connected with the positive electrode of the LED module, the emitter electrode of the triode switch is connected with the output end of the first current limiting circuit, the base electrode of the triode switch is connected with the constant current control end of the constant current control module, the input end of the first current limiting circuit is connected with the input end of the constant current control module, and the negative electrode of the LED module is connected with a low-voltage point; the first current limiting circuit is used for keeping the current at two ends constant when the voltage at the two ends is unchanged; the triode switch works in a saturation region or an amplification region to enable the LED module to be lighted.
As one implementation, the constant current control module includes: the load circuit, the first voltage limiting triode, the second voltage limiting triode and the second current limiting circuit;
the emitter of the first voltage limiting triode is the output end of the constant current control module, the collector is connected with the output end of the load circuit, and the base is connected with the input end of the second current limiting circuit;
the input end of the load circuit is the input end of the constant current control module, the output end of the load circuit is also connected with the base electrode of the second voltage limiting triode, the emitter electrode of the second voltage limiting triode is connected with the base electrode of the first voltage limiting triode, and the collector electrode of the second voltage limiting triode is the constant current control end of the constant current control module;
the output end of the second current limiting circuit is connected with the emitter of the first voltage limiting triode, and the second current limiting circuit is used for keeping constant current at two ends when the voltage at the two ends is unchanged;
the first voltage limiting triode works in an amplifying region, and the second voltage limiting triode works in a saturation region or an amplifying region, so that the current of the constant current control end is constant.
As an implementation manner, the first voltage limiting triode and the second voltage limiting triode are NPN type triodes.
As one implementation, the triode switch is a PNP triode.
As one implementation, the load circuit is a resistor circuit composed of at least one resistor.
As one implementation, the second current limiting circuit is a resistor circuit formed by at least one resistor.
As one implementation manner, the first current limiting circuit is a resistor circuit formed by at least one resistor; the constant voltage control module is a resistor circuit formed by at least one resistor.
As one implementation manner, the constant voltage control module is a voltage stabilizing tube.
As an implementation, the LED module includes one LED, or at least 2 LEDs connected in series in sequence.
The application provides an LED constant current driving circuit, comprising: the constant current control module, the constant voltage control module, the first current limiting circuit, the triode switch and the Light Emitting Diode (LED) module; the output end of the constant-voltage control module is connected with the constant-current control end of the constant-current control module, the input end of the constant-current control module is connected with the input end of the constant-current control module, the input end of the constant-current control module is also connected with a power supply, the output end of the constant-current control module is connected with a low-potential point, and the constant-voltage control module is used for keeping the voltage values of two ends constant when the currents of the two ends are unchanged; the LED module comprises a first current limiting circuit, a triode switch and an LED module, wherein the first current limiting circuit, the triode switch and the LED module are sequentially connected in series, the collector of the triode switch is connected with the anode of the LED module, the emitter of the triode switch is connected with the output end of the first current limiting circuit, the base of the triode switch is connected with the constant current control end of the constant current control module, the input end of the first current limiting circuit is connected with the input end of the constant current control module, and the cathode of the LED module is connected with a low-voltage point; the first current limiting circuit is used for keeping the current at two ends constant when the voltage at the two ends is unchanged; the triode switch works in a saturation region or an amplification region, and the LED module is lightened so as to keep the driving current of the LED constant when the power supply voltage changes.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings used in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are some embodiments of the present application, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic diagram of a structure of an LED constant current driving circuit according to an embodiment of the present application;
fig. 2 is a schematic structural diagram of a constant current control module according to an embodiment of the present application;
fig. 3 is a schematic structural diagram of an LED constant current driving circuit including the constant current control module shown in fig. 2 according to an embodiment of the present application;
fig. 4 is a schematic diagram of a structure of another LED constant current driving circuit according to an embodiment of the present application;
fig. 5 is a schematic diagram of another LED constant current driving circuit according to an embodiment of the present application;
fig. 6 is a schematic diagram of another LED constant current driving circuit according to an embodiment of the present application.
In the figure:
1-a constant current control module;
2-a constant voltage control module;
3-a first current limiting circuit;
a 4-LED module;
11-a load circuit;
12-a second current limiting circuit;
q1-a first voltage limiting triode;
q2-a second voltage limiting triode;
q3-triode switch.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present application more apparent, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application, and it is apparent that the described embodiments are only some embodiments of the present application, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
The terms "first," "second," "third," "fourth" and the like in the description and in the claims and in the above drawings, if any, are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged where appropriate such that the embodiments of the application described herein may be implemented in sequences other than those illustrated or otherwise described herein.
It should be understood that in the present application, "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements that are expressly listed or inherent to such process, method, article, or apparatus.
It should be understood that in the present application, "plurality" means two or more. "and/or" is merely an association relationship describing an association object, and means that three relationships may exist, for example, and/or B may mean: a exists alone, A and B exist together, and B exists alone. The character "/" generally indicates that the context-dependent object is an "or" relationship.
It should be understood that in the present application, the voltage drop at the AB pole or the voltage at the AB pole of the transistor refers to the voltage drop between the a pole and the B pole of the transistor. For example, the base emitter voltage drop or base emitter voltage refers to the voltage drop between the base and emitter of a transistor; collector-emitter voltage drop or collector-emitter voltage, which refers to the voltage drop between the collector and emitter of a triode; collector-base voltage drop or collector-base voltage refers to the voltage drop between the collector and base of a transistor.
As used herein, "if" may be interpreted as "at … …" or "at … …" or "in response to a determination" or "in response to detection" depending on the context.
The technical scheme of the application is described in detail below by specific examples. The following embodiments may be combined with each other, and some embodiments may not be repeated for the same or similar concepts or processes.
It should be noted that, the illustrations provided in the embodiments of the application are merely schematic illustrations of the basic concepts of the application, in which only the components related to the application are shown, not according to the number, shape and size of the components in actual implementation, and the form, number and proportion of the components in actual implementation may be arbitrarily changed, and the layout of the components may be more complex.
The LED has the characteristics of small driving voltage, good shock resistance and shock resistance, high reliability, long service life and the like, so the application field of the LED is continuously expanded. From low luminous flux indicator lamps to display screens, from outdoor display screens to medium luminous flux power signal lamps and specially illuminated white light sources, and finally to high luminous flux general illumination sources. In many application fields of LEDs, constant-current and constant-voltage driving of the LEDs cannot be ensured at the same time, and when the voltage and current are unstable, the LEDs are likely to emit light unstably or to be extinguished. The embodiment of the application provides an LED constant current driving circuit, which provides constant current on a circuit where an LED module is located through the combined action of a constant current control module and a constant voltage control module.
Fig. 1 is a schematic diagram of an LED constant current driving circuit according to an embodiment of the present application.
The circuit configuration shown in fig. 1 may be a separate circuit or may be a built-in module integrated into an electronic display device or a lighting device. The electronic display device may be, for example, a device with a display screen, or a device with a signal indicator, or may be a light-emitting end device in a photodetection apparatus.
The LED constant current driving circuit as shown in fig. 1 may include at least: the constant current control module 1, the constant voltage control module 2, the first current limiting circuit 3, the triode switch Q3 and the light emitting diode LED module 4. In fig. 1, a constant current control module 1 is provided with an input terminal, a constant current control terminal, and an output terminal. The input end of the constant current control module 1 is connected with high potential, the constant current control module 1 is used for controlling the constant current of the constant current control end or slowing down the current change of the constant current control end, and the output end of the constant current control module 1 is used for being connected with low potential.
With continued reference to the LED constant current driving circuit shown in fig. 1, the output end of the constant voltage control module 2 is connected to the constant current control end of the constant current control module 1, the input end is connected to the input end of the constant current control module 1, and the constant voltage control module 2 is used for keeping the voltage values of the two ends constant when the current of the two ends is unchanged. The current on the circuit of the constant current control end of the constant current control module 1 connected with the constant voltage control module 2 is constant. The input end of the constant current control module 1 is also connected with a power supply, and the output end of the constant current control module 1 is connected with a low-voltage point. The low potential point can be understood as a ground terminal, and the output terminal of the constant current control module 1 can be directly grounded. The power supply directly connected to the input of the constant current control module 1 is understood to be a direct current power supply, for example a dry cell power supply, a lithium manganese button cell (minimum 2V) or a battery power supply.
With continued reference to the LED constant current driving circuit shown in fig. 1, the first current limiting circuit 3, the triode switch Q3 and the LED module 4 are sequentially connected in series, the collector of the triode switch Q3 is connected with the positive electrode of the LED module 4, the emitter is connected with the output end of the first current limiting circuit 3, the base is connected with the constant current control end of the constant current control module 1, the input end of the first current limiting circuit 3 is connected with the input end of the constant current control module 1, the negative electrode of the LED module 4 is connected with a low potential point, and the first current limiting circuit 3 is used for keeping the current at two ends constant when the voltage at two ends is unchanged; the transistor switch Q3 operates in a saturation region or an amplification region to turn on the LED module 4.
In the LED constant current driving circuit shown in FIG. 1, I 3 ＝I 1 +I 2 ，I 1 For the output current of the constant voltage control module 2, I 2 Base current of transistor switch Q3, I 3 Is the current of the constant current control end of the constant current control module 1. Since the constant current control module 1 is used for making I 3 Constant, but very weak, the base current of the transistor is negligible in this embodiment, and therefore can be understood as the base current I of transistor switch Q3 2 Is 0. From this, it can be seen that when the power supply voltage changes, I 3 ＝I 1 The current of the branch where the constant voltage control module 2 is located is constant. The constant voltage control module 2 is used for keeping the voltage values of the two ends constant when the current of the two ends is unchanged, so that the voltage values of the two ends of the constant voltage control module 2 are constant when the power supply voltage is changed.
As can be seen from fig. 1, the input end of the constant voltage control module 2 and the input end of the first current limiting circuit 3 are both at the same potential as the point a, and the output end of the constant voltage control module 2 and the base electrode of the triode switch Q3 are both at the same potential as the point B. Therefore, the sum of the voltage drop across the first current limiting circuit 3 and the voltage drop across the base of the transistor switch Q3 is equal to the voltage drop across the constant voltage control module 2, which is equal to the potential difference from point a to point B. Thus, when the supply voltage changes, the sum of the voltage drop across the first current limiting circuit 3 and the voltage drop across the base of the transistor switch Q3 is constant.
Due to the characteristics of the transistor, the voltage across the base-emitter is substantially constant, i.e. the voltage drop across the base-emitter of the transistor switch Q3 is constant when the supply voltage is changed. It is furthermore determined that the voltage drop over the first current limiting circuit 3 is constant when the supply voltage changes.
The first current limiting circuit 3 is used for keeping the current at two ends constant when the voltage at two ends is unchanged. The current of the first current limiting circuit 3 is thus constant, thereby determining that the emitter current of the transistor switch Q3 is constant. As can be seen from the characteristics of the transistor, when the transistor is operated in the saturation region or the amplification region, the emitter current of the transistor is approximately equal to the collector current when the initial bias current is set. Thus, the collector of the transistor switch Q3 operates at a constant current to drive the LED module 4 connected in series therewith. The driving current is constant so that the LED module 4 can maintain stable brightness during light emission.
Referring to fig. 1 and 2, the threshold of the on-voltage drop between the base emitters of the first and second voltage limiting transistors Q1, Q2 and Q3 is Vbe1, vbe2 and Veb3, respectively (Veb 3= -Vbe3>0 for the transistor Q3). The first voltage limiting triode Q1 works in an amplifying region, and then the voltage at the point C is larger than Vbe1; the second voltage limiting triode Q2 works in a saturation region or an amplifying region, the voltage at the point D is greater than Vb1+Vbe2, and the voltage at the point B is greater than Vbe1 (namely greater than the voltage at the point C and can be smaller than the voltage at the point D in the saturation region); when the triode switch Q3 operates in the saturation region or the amplification region, the emitter voltage of the triode switch Q3 is greater than Vbe1 (i.e., greater than the point B voltage). For example, the conventional Vbe1 is generally about 0.7V, so that each triode requires the Q3 emitter voltage to be greater than 0.7V when in operation; the voltage drop of a conventional single LED is larger than 1.8V, so that the emitter voltage of the triode switch Q3 is required to be larger than 1.8V in operation, and the requirement of being larger than 0.7V is simultaneously met under the condition, so that each triode can enter a state capable of normally working. In summary, the emitter voltage of the triode switch Q3 is greater than the voltage drop of the LED module (e.g. 1.8V), and the voltage drop at both ends of the first current limiting circuit 3 can be set to V1 (e.g. 0.2V), so that the power supply voltage is only required to be greater than the voltage drop of the LED module by V1 (e.g. 1.8v+0.2v), and the whole circuit can enter constant current driving. When the power supply voltage is 2V at the minimum, the collector voltage of the triode switch Q3 is negligible, and as the voltage increases, for example, the power supply voltage increases to 3V, the collector voltage of the triode switch Q3 increases to 1V. In the process that the power supply voltage is gradually increased from the lowest voltage (for example, 2V), the driving current of the LED module is unchanged, and constant current driving can be kept in the power supply voltage range. It is noted that the larger V1 initially set by the choice of the respective device parameters, the more stable the LED current.
The current is limited to be constant on the branch of the first current limiting circuit 3, the triode switch Q3 and the LED module 4 which are sequentially connected in series, and the sum of the voltage drop on the first current limiting circuit 3 and the voltage drop on the base electrode of the triode switch Q3 is limited to be constant. When the supply voltage changes, the voltage drop across the collector of the transistor switch Q3 is changed. The voltage drop variation of the collector emitter of the triode switch Q3 is equal to the voltage variation of the power supply, and the current is unchanged, so that the voltage drop of the LED module 4 is kept unchanged.
The application provides an LED constant current driving circuit, comprising: the constant current control module, the constant voltage control module, the first current limiting circuit, the triode switch and the Light Emitting Diode (LED) module; the output end of the constant-voltage control module is connected with the constant-current control end of the constant-current control module, the input end of the constant-current control module is connected with the input end of the constant-current control module, the input end of the constant-current control module is also connected with a power supply, the output end of the constant-current control module is connected with a low-potential point, and the constant-voltage control module is used for keeping the voltage values of two ends constant when the currents of the two ends are unchanged; the LED module comprises a first current limiting circuit, a triode switch and an LED module, wherein the first current limiting circuit, the triode switch and the LED module are sequentially connected in series, the collector of the triode switch is connected with the anode of the LED module, the emitter of the triode switch is connected with the output end of the first current limiting circuit, the base of the triode switch is connected with the constant current control end of the constant current control module, the input end of the first current limiting circuit is connected with the input end of the constant current control module, and the cathode of the LED module is connected with a low-voltage point; the first current limiting circuit is used for keeping the current at two ends constant when the voltage at the two ends is unchanged; the triode switch works in a saturation region or an amplification region, and the LED module is lightened so as to keep the driving current of the LED constant when the power supply voltage changes.
Fig. 2 is a schematic structural diagram of a constant current control module according to an embodiment of the present application.
Fig. 3 is a schematic structural diagram of an LED constant current driving circuit including the constant current control module shown in fig. 2 according to an embodiment of the present application.
On the basis of the embodiment shown in fig. 1, the constant current control module 1 shown in fig. 2 includes: the load circuit 11, the first voltage limiting triode Q1, the second voltage limiting triode Q2 and the second current limiting circuit 12.
The emitter of the first voltage limiting triode Q1 is the output end of the constant current control module 1, the collector is connected with the output end of the load circuit 11, and the base is connected with the input end of the second current limiting circuit 12. The load circuit 11 is used as a load of the first voltage limiting triode Q1, and the voltage drop variation of the load circuit 11 is equal to the power supply voltage variation, so that the maximum current limiting function is achieved on the branch circuit where the load circuit 11 and the first voltage limiting triode Q1 are located.
With continued reference to the constant current control module 1 shown in fig. 2, the input end of the load circuit 11 is the input end of the constant current control module 1, the output end of the load circuit 11 is also connected with the base electrode of the second voltage limiting triode Q2, the emitter electrode of the second voltage limiting triode Q2 is connected with the base electrode of the first voltage limiting triode Q1, and the collector electrode of the second voltage limiting triode Q2 is the constant current control end of the constant current control module 1. The output end of the second current limiting circuit 12 is connected with the emitter of the first voltage limiting triode Q1, and the second current limiting circuit 12 is used for keeping the current at two ends constant when the voltage at the two ends is unchanged. The first voltage limiting triode Q1 works in an amplifying region, and the second voltage limiting triode Q2 works in a saturation region or an amplifying region, so that the current of the constant current control end is constant.
According to the characteristic that the base emitter voltage of the triode is basically unchanged, it can be known that the voltage at the two ends of the second current limiting circuit 12 is clamped by the base emitter voltage of the first voltage limiting triode Q1. For example, the emitter voltage drop of the first voltage limiting transistor Q1 is constant at 0.7V, and the voltage drop of the second current limiting circuit 12 is also constant at 0.7V. Since the second current limiting circuit 12 is used for keeping the current at two ends constant when the voltage at two ends is unchanged, and meanwhile, the base current of the first voltage limiting triode Q1 is extremely small when the first voltage limiting triode Q1 works in an amplifying region, and the current of the second current limiting circuit 12 is constant.
Since the base current of the transistor is almost negligible, the current of the second current limiting circuit 12 in this embodiment is equal to the emitter current of the second voltage limiting transistor Q2. The collector current of the second voltage limiting triode Q2 forms negative feedback to the base emitter voltage drop of the second voltage limiting triode Q2, so that the collector current of the second voltage limiting triode Q2 is stable. According to the fact that the triode works in the circuit, the emitter current is approximately equal to the collector current, in the embodiment, the collector current of the second voltage limiting triode Q2 is equal to the current of the second current limiting circuit 12 and is constant, and therefore constant control of the current of the control end of the constant current control module 1 is achieved.
Referring to fig. 2 and 3, the base emitter voltage drop of the first voltage limiting transistor Q1 and the voltage drop of the second current limiting circuit 12 are equal to the voltage drop from the output terminal to the point C. The voltage drop of the collector base of the first voltage limiting triode Q1 and the voltage drop of the base emitter of the second voltage limiting triode Q2 are equal to the voltage drop from the point D to the point C. The first voltage limiting triode Q1 and the second voltage limiting triode Q2 of the circuit have basically unchanged base emitter voltage drop. Therefore, if the low potential connected to the output terminal of the constant current control module 1 is ground, the voltage at the point D is 2 times the voltage drop of the base emitter of the first voltage limiting triode Q1. For example, the base emitter voltage drops of the first voltage limiting transistor Q1 and the second voltage limiting transistor Q2 are both 0.7V, and the voltage at the point D is 1.4V. When the power supply voltage changes, the voltage at the point D does not change.
With continued reference to fig. 3, on the branch where the load circuit 11 and the first voltage limiting transistor Q1 are located, the voltage drop variation of the load circuit 11 is equal to the voltage variation of the power supply. On the branch where the constant voltage control module 2, the second voltage limiting triode Q2 and the second current limiting circuit 12 are located, the emitter voltage drop variation of the second voltage limiting triode Q2 is equal to the voltage variation of the power supply.
The embodiment of the application provides a constant current control module, which mainly comprises: the device comprises a load circuit, a first voltage limiting triode, a second voltage limiting triode and a second current limiting circuit. The emitter of the first voltage limiting triode is the output end of the constant current control module, the collector is connected with the output end of the load circuit, and the base is connected with the input end of the second current limiting circuit. The input end of the load circuit is the input end of the constant current control module, the output end of the load circuit is also connected with the base electrode of the second voltage limiting triode, the emitter electrode of the second voltage limiting triode is connected with the base electrode of the first voltage limiting triode, and the collector electrode of the second voltage limiting triode is the constant current control end of the constant current control module. The output end of the second current limiting circuit is connected with the emitter of the first voltage limiting triode, and the second current limiting circuit is used for keeping the current at two ends constant when the voltage at two ends is unchanged. The first voltage limiting triode works in the amplifying region, and the second voltage limiting triode works in the saturation region or the amplifying region, so that the current of the constant current control end is constant. According to the embodiment, the voltage of the second current limiting circuit is clamped through the base emitter voltage of the first voltage limiting triode, so that the current of the second current limiting circuit is constant, the collector current of the second voltage limiting triode is equal to the current of the second current limiting circuit and is constant, and constant control of the current of the constant current control end of the constant current control module is achieved. In the embodiment, constant current control end current is obtained through the connection relation of the first voltage limiting triode, the second voltage limiting triode and the second current limiting circuit.
With continued reference to fig. 2 and 3, the first voltage limiting transistor Q1 and the second voltage limiting transistor Q2 may be NPN transistors. With continued reference to fig. 3, the transistor switch Q3 may be a PNP transistor based on the above embodiments. Fig. 4 is a schematic diagram of another LED constant current driving circuit according to an embodiment of the present application.
As shown in fig. 4, the load circuit 11 is a resistor circuit composed of at least one resistor.
The load circuit 11 may be a resistor as shown in fig. 4, or may be a plurality of resistors connected in series or parallel to form a preset load resistance value, so as to limit the collector current and the emitter current on the first voltage limiting transistor Q1.
Fig. 5 is a schematic diagram of another LED constant current driving circuit according to an embodiment of the present application.
As shown in fig. 5, the second current limiting circuit 12 is a resistor circuit composed of at least one resistor.
The second current limiting circuit 12 may be a resistor as shown in fig. 5, or may be a plurality of resistors connected in series or parallel to form a preset second current limiting resistance value, so as to determine the collector current and the constant current of the emitter on the second voltage limiting triode Q2.
Fig. 6 is a schematic diagram of another LED constant current driving circuit according to an embodiment of the present application.
As shown in fig. 6, the first current limiting circuit 3 is a resistor circuit constituted by at least one resistor. The constant voltage control module 2 is a resistor circuit composed of at least one resistor. The first current limiting circuit 3 and the constant voltage control module 2 may be one resistor as shown in fig. 6, or may be a plurality of resistors connected in series or parallel.
In an alternative implementation manner, the constant voltage control module 2 may be a voltage stabilizing tube. The voltage between the point A and the point B is stabilized by arranging the voltage stabilizing tube, so that the constant current of the collector electrode of the triode switch is obtained, and the constant current driving of the LED is realized.
In an alternative implementation manner based on the above embodiment, the LED module may be one LED, or may be at least 2 LEDs connected in series sequentially. The at least 2 LEDs connected in series in turn may be, for example, a plurality of indicator lights or a display unit.
The embodiments of the application described above may meet lower voltage inputs. On the premise of constant current driving, the driving voltage can be as low as approximately the voltage drop of the LED (for example, only 200mV larger than the voltage drop of the LED), so that the constant current driving of the LED can be realized under the lowest working voltage by the voltage source, and the LED driving device is suitable for driving the indicator lamp of a conventional lithium manganese button cell (minimum 2.0V). The embodiments of the application have simple structure and principle, do not need to use too many components (such as MCU and PWM control circuit, etc.), and reduce cost and complexity.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present application, and not for limiting the same; although the application has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the application.
Claims (10)
1. An LED constant current driving circuit, comprising: the constant current control module, the constant voltage control module, the first current limiting circuit, the triode switch and the Light Emitting Diode (LED) module;
the output end of the constant voltage control module is connected with the constant current control end of the constant current control module, the input end of the constant current control module is connected with the input end of the constant current control module, the input end of the constant current control module is also connected with a power supply, and the output end of the constant current control module is connected with a low potential point;
the first current limiting circuit, the triode switch and the LED module are sequentially connected in series, the collector electrode of the triode switch is connected with the positive electrode of the LED module, the emitter electrode of the triode switch is connected with the output end of the first current limiting circuit, the base electrode of the triode switch is connected with the constant current control end of the constant current control module, the input end of the first current limiting circuit is connected with the input end of the constant current control module, and the negative electrode of the LED module is connected with the low-voltage point;
the constant voltage control module is used for keeping the voltage values of the two ends constant when the current of the two ends is unchanged; the first current limiting circuit is used for keeping the current at two ends constant when the voltage at the two ends is unchanged; the triode switch works in a saturation region or an amplification region, so that the LED module is lightened.
2. The circuit of claim 1, wherein the constant current control module comprises: the load circuit, the first voltage limiting triode, the second voltage limiting triode and the second current limiting circuit;
the emitter of the first voltage limiting triode is the output end of the constant current control module, the collector is connected with the output end of the load circuit, and the base is connected with the input end of the second current limiting circuit;
the input end of the load circuit is the input end of the constant current control module, the output end of the load circuit is also connected with the base electrode of the second voltage limiting triode, the emitter electrode of the second voltage limiting triode is connected with the base electrode of the first voltage limiting triode, and the collector electrode of the second voltage limiting triode is the constant current control end of the constant current control module;
the output end of the second current limiting circuit is connected with the emitter of the first voltage limiting triode, and the second current limiting circuit is used for keeping constant current at two ends when the voltage at the two ends is unchanged;
the first voltage limiting triode works in an amplifying region, and the second voltage limiting triode works in a saturation region or an amplifying region, so that the current of the constant current control end is constant.
3. The circuit of claim 2, wherein the first voltage limiting transistor and the second voltage limiting transistor are NPN transistors.
4. A circuit according to any one of claims 1 to 3, wherein the transistor switch is a PNP transistor.
5. The circuit of claim 2, wherein the load circuit is a resistive circuit comprised of at least one resistor.
6. The circuit of claim 2 or 5, wherein the second current limiting circuit is a resistive circuit comprised of at least one resistor.
7. The circuit of claim 1, wherein the first current limiting circuit is a resistive circuit comprised of at least one resistor.
8. The circuit of claim 1, wherein the constant voltage control module is a resistive circuit comprised of at least one resistor.
9. The circuit of claim 1, wherein the constant voltage control module is a regulator tube.
10. The circuit of claim 1, wherein the LED module comprises one LED, or at least 2 LEDs in series in sequence.
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| CN110767152B (en) * | 2019-11-08 | 2020-10-30 | 四川遂宁市利普芯微电子有限公司 | Constant current source generating method of LED display screen driving chip |
| CN110827747B (en) * | 2019-11-08 | 2020-10-30 | 四川遂宁市利普芯微电子有限公司 | Constant current source generating circuit of common-cathode LED display screen driving chip |
| CN111654944B (en) * | 2020-06-22 | 2023-04-18 | 大峡谷照明系统（苏州）股份有限公司 | Current amplification circuit and method and LED drive circuit |
| CN113939059A (en) * | 2021-09-30 | 2022-01-14 | 马瑞利汽车零部件(芜湖)有限公司 | Shunting type LED current type sectional dimming circuit, lamp and automobile |
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