CN108174488B - LED protection circuit - Google Patents
LED protection circuit Download PDFInfo
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- CN108174488B CN108174488B CN201810048095.2A CN201810048095A CN108174488B CN 108174488 B CN108174488 B CN 108174488B CN 201810048095 A CN201810048095 A CN 201810048095A CN 108174488 B CN108174488 B CN 108174488B
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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]
- H05B45/50—Circuit arrangements for operating light-emitting diodes [LED] responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits
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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
- 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
- Y02B20/30—Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]
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- Circuit Arrangement For Electric Light Sources In General (AREA)
Abstract
The invention discloses an LED protection circuit, comprising: the LED driving circuit, the comparison circuit, the filtering delay circuit, the protection state detection circuit and the reference circuit; the LED driving circuit is used for providing driving current for the LED; the reference circuit is used for providing a reference voltage; the comparison circuit is used for comparing the reference voltage with the cathode voltage of the LED; the filtering delay circuit is used for filtering the level signal output by the comparison circuit; the protection state detection circuit is used for detecting the working state of the LED. The LED protection circuit has the advantages of simple circuit structure, reliable performance, low cost, capability of detecting the circuit state after triggering, automatic recovery after short-circuit fault removal and the like.
Description
Technical Field
The invention relates to the technical field of power protection circuits, in particular to an LED protection circuit.
Background
With the continuous development of science and technology, various electronic devices have been widely applied to daily life and work of people, and great convenience is brought to life and work of people.
Because the LED constant current source (leakage) driving circuit has the advantages of simple structure, few peripheral devices, low cost and the like, the LED constant current source (leakage) driving circuit is widely used, based on the portable equipment camera, as the requirement of the user on the portable equipment camera is continuously increased, the driving current of the LED driving chip is also increased, and it is necessary to add a short-circuit protection circuit in the chip in order to prevent the chip from being burnt due to the short circuit of the LED lamp bead.
However, the conventional protection circuit has a complicated circuit structure, a large number of components and high cost.
Therefore, how to provide an LED protection circuit structure with a simple circuit and low cost is an urgent problem to be solved by those skilled in the art.
Disclosure of Invention
In order to solve the problems, the invention provides the LED protection circuit which has the advantages of simple circuit structure, reliable performance, low cost, capability of detecting the circuit state after triggering, automatic recovery after short-circuit fault removal and the like.
In order to achieve the purpose, the invention provides the following technical scheme:
an LED protection circuit, comprising: the LED driving circuit, the comparison circuit, the filtering delay circuit, the protection state detection circuit and the reference circuit;
the LED driving circuit is used for providing driving current for the LED; the reference circuit is used for providing a reference voltage; the comparison circuit is used for comparing the reference voltage with the cathode voltage of the LED; the filtering delay circuit is used for filtering the level signal output by the comparison circuit; the protection state detection circuit is used for detecting the working state of the LED.
Preferably, in the LED protection circuit, the LED driving circuit includes: the LED comprises a first controllable current source, an LED, a first field effect transistor and a second field effect transistor;
one end of the first controllable current source is connected with a voltage input end of the LED protection circuit, the other end of the first controllable current source is connected with a drain electrode of the first field effect tube, a source electrode of the first field effect tube is connected with the ground, a grid electrode of the first field effect tube is connected with a grid electrode of the second field effect tube, the grid electrode of the first field effect tube is connected with the drain electrode of the first field effect tube, the source electrode of the second field effect tube is connected with the ground, the drain electrode of the second field effect tube is connected with a cathode of the LED, and an anode of the LED is connected with the voltage input end.
Preferably, in the LED protection circuit, the LED driving circuit further includes: a third field effect transistor;
the source electrode of the third field effect tube is connected with the ground, the drain electrode of the third field effect tube is connected with the connection node of the grid electrode of the first field effect tube and the grid electrode of the second field effect tube, and the grid electrode of the third field effect tube is connected with the voltage output end of the LED protection circuit.
Preferably, in the LED protection circuit, the reference circuit includes: the first resistor, the second controllable current source, the fourth field effect transistor and the third controllable current source;
one end of the first resistor is connected with the voltage input end, the other end of the first resistor is connected with one end of the second controllable current source, the other end of the second controllable current source is connected with the ground, the drain electrode of the fourth field effect transistor is connected with the connection node of the first resistor and the second controllable current source, the source electrode of the fourth field effect transistor is connected with the ground through the third controllable current source, and the grid electrode of the fourth field effect transistor is connected with the voltage output end of the LED protection circuit.
Preferably, in the LED protection circuit, the comparison circuit includes: a comparator;
the negative phase input end of the comparator is connected with the connection node of the cathode of the LED and the drain electrode of the second field effect transistor, the positive phase input end of the comparator is connected with the connection node of the first resistor and the second controllable current source, and the output end of the comparator is connected with the filtering delay circuit.
Preferably, in the above LED protection circuit, the filter delay circuit includes: the device comprises a fifth field effect transistor, a sixth field effect transistor, a fourth controllable current source, a fifth controllable current source, a capacitor, a Schmitt device and a phase inverter;
wherein a source electrode of the fifth field effect transistor is connected with the voltage input end through the fourth controllable current source, a gate electrode of the fifth field effect transistor is connected with a gate electrode of the sixth field effect transistor, an output end of the comparator is connected with a connection node of the gate electrode of the fifth field effect transistor and the gate electrode of the sixth field effect transistor, a drain electrode of the fifth field effect transistor is connected with a drain electrode of the sixth field effect transistor, a source electrode of the sixth field effect transistor is grounded through the fifth controllable current source, one end of the capacitor is connected with a connection node of the drain electrode of the fifth field effect transistor and the drain electrode of the sixth field effect transistor, the other end of the capacitor is grounded, one end of the schmitt device is connected with a connection node of the drain electrode of the fifth field effect transistor and the drain electrode of the sixth field effect transistor, and the other end of the schmitt device is connected with one end of the phase inverter, the other end of the phase inverter is connected with the voltage output end.
Preferably, in the LED protection circuit, the protection state detection circuit includes: a seventh field effect transistor and a sixth controllable current source;
the drain electrode of the seventh field effect transistor is connected with the connection node of the cathode of the LED and the drain electrode of the second field effect transistor, the source electrode of the seventh field effect transistor is connected with the ground through the sixth controllable current source, and the grid electrode of the seventh field effect transistor is connected with the voltage output end of the LED protection circuit.
As can be seen from the above description, the present invention provides an LED protection circuit, including: the LED driving circuit, the comparison circuit, the filtering delay circuit, the protection state detection circuit and the reference circuit; the LED driving circuit is used for providing driving current for the LED; the reference circuit is used for providing a reference voltage; the comparison circuit is used for comparing the reference voltage with the cathode voltage of the LED; the filtering delay circuit is used for filtering the level signal output by the comparison circuit; the protection state detection circuit is used for detecting the working state of the LED.
The LED protection circuit has the advantages of simple circuit structure, reliable performance, low cost, capability of detecting the circuit state after triggering, automatic recovery after short-circuit fault removal and the like.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
Fig. 1 is a schematic structural diagram of an LED protection circuit according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of another LED protection circuit according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
Referring to fig. 1, fig. 1 is a schematic structural diagram of an LED protection circuit according to an embodiment of the present invention.
The LED protection circuit includes: the circuit comprises an LED drive circuit 1, a comparison circuit 4, a filtering delay circuit 5, a protection state detection circuit 2 and a reference circuit 3.
The LED driving circuit 1 is used for providing driving current for an LED; the reference circuit 3 is used for providing a reference voltage; the comparison circuit 4 is used for comparing the reference voltage with the cathode voltage of the LED; the filtering delay circuit 5 is used for filtering the level signal output by the comparison circuit 4; the protection state detection circuit 2 is used for detecting the working state of the LED.
Specifically, whether the short circuit phenomenon occurs in the LED is judged by directly detecting the magnitude relation between the LED cathode voltage and the reference voltage, and the circuit state of the LED driving circuit, namely the working state of the LED, can be detected in real time by arranging the protection state detection circuit, so that the scale of the LED protection circuit is greatly reduced, and the reliability of the LED protection circuit is also improved.
Further, as shown in fig. 1, the LED driving circuit 1 includes: a first controllable current source I1, an LED, a first fet NM1, and a second fet NM 2.
Wherein, one end of the first controllable current source I1 is connected with a voltage input terminal VDD of the LED protection circuit, the other end of the first controllable current source I1 is connected with the drain of the first fet NM1, the source of the first fet NM1 is connected to ground GND, the gate of the first fet NM1 is connected with the gate of the second fet NM2, the gate of the first fet NM1 is connected with the drain of the first fet NM1, the source of the second fet NM2 is connected to ground GND, the drain of the second fet NM2 is connected with the cathode of the LED, and the anode of the LED is connected with the voltage input terminal VDD.
Specifically, the first controllable current source I1 may be any form of controllable current source, and is not limited in the embodiment of the present invention, the first fet NM1 and the second fet NM2 are N-type fets, the first fet NM1 and the second fet NM2 constitute a current mirror circuit, and the current circuit formed by the first controllable current source I1, the first fet NM1, and the second fet NM2 is a constant current driving circuit, and is configured to drive the LED light emitting diode.
Further, as shown in fig. 2, the LED driving circuit 1 further includes: and a third field effect transistor NM 3.
Wherein, the source of the third fet NM3 is connected to the GND, the drain of the third fet NM3 is connected to the connection node between the gate of the first fet NM1 and the gate of the second fet NM2, and the gate of the third fet NM3 is connected to the voltage output terminal VSP of the LED protection circuit.
Specifically, the third fet NM3 is an N-type fet, and is an enable control circuit of the LED driving circuit, and is configured to turn on or off the LED driving circuit. When the third fet NM3 is turned on, the gate voltage of the first fet NM1 and the gate voltage of the second fet NM2 are both pulled low, and the first fet NM1 and the second fet NM2 are both in an off state; when the third fet NM3 is turned off, the first fet NM1 and the second fet NM2 are in a conductive state; that is, when the LED is short-circuited, the third fet NM3 is controlled to be turned on, so that the first fet NM1 and the second fet NM2 are turned off, thereby protecting other circuit structures in case of short-circuit of the LED.
Further, as shown in fig. 1, the reference circuit 3 includes: a first resistor R1, a second controllable current source I2, a fourth FET NM4 and a third controllable current source I3.
One end of the first resistor R1 is connected to the voltage input terminal VDD, the other end of the first resistor R1 is connected to one end of the second controllable current source I2, the other end of the second controllable current source I2 is connected to ground GND, the drain of the fourth fet NM4 is connected to the connection node between the first resistor R1 and the second controllable current source I2, the source of the fourth fet NM4 is connected to ground GND through the third controllable current source I3, and the gate of the fourth fet NM4 is connected to the voltage output terminal VSP of the LED protection circuit.
Specifically, the second controllable current source I2 and the third controllable current source I3 may be any type of controllable current source, and in this embodiment of the invention, the fourth fet NM4 is an N-type fet, the first resistor R1 and the second controllable current source I2 are configured to generate a fixed voltage drop, and the fourth fet NM4 and the third controllable current source I3 are configured to generate a hysteresis window voltage, and are configured to provide a reference voltage for the comparison circuit 4.
Further, as shown in fig. 1, the comparison circuit 4 includes: a comparator COMP.
An inverting input end of the comparator COMP is connected with a connection node between the cathode of the LED and the drain of the second field effect transistor NM2, a non-inverting input end of the comparator COMP is connected with a connection node between the first resistor R1 and the second controllable current source I2, and an COMP output end of the comparator COMP is connected with the filtering delay circuit 5.
Specifically, whether the short circuit phenomenon occurs in the LED is judged by detecting the magnitude relation between the cathode voltage of the LED and the reference voltage, when the whole protection circuit is not turned on, the comparator COMP is turned off by the enable signal EN _ SP, all the controllable current sources are turned off, so that false triggering is prevented, and meanwhile, the electrostatic power consumption is reduced.
Further, as shown in fig. 1, the filtering delay circuit 5 includes: a fifth field effect transistor PM1, a sixth field effect transistor NM5, a fourth controllable current source I4, a fifth controllable current source I5, a capacitor C, a Schmitt and an inverter INV 1.
Wherein a source of the fifth fet PM1 is connected to the voltage input terminal VDD via the fourth controllable current source I4, a gate of the fifth fet PM1 is connected to a gate of the sixth fet NM5, an output terminal of the comparator COMP is connected to a connection node between the gate of the fifth fet PM1 and the gate of the sixth fet NM5, a drain of the fifth fet PM1 is connected to a drain of the sixth fet NM5, a source of the sixth fet NM5 is connected to the ground GND via the fifth controllable current source I5, one end of the capacitor C is connected to a connection node between the drain of the fifth fet PM1 and the drain of the sixth fet NM5, the other end of the capacitor C is connected to the ground GND, and one end of the Schmitt is connected to a connection node between the drain of the fifth fet PM1 and the drain of the sixth fet NM5, the other end of the Schmitt is connected to one end of the inverter INV1, and the other end of the inverter INV1 is connected to the voltage output terminal VSP.
Specifically, the fourth controllable current source I4 and the fifth controllable current source I5 may be controllable current sources of any form, and in this embodiment of the present invention, without limitation, the fifth fet PM1 is a P-type fet, the sixth fet NM5 is an N-type fet, and the filtering delay circuit 5 is mainly configured to filter a "glitch" signal output by the comparing circuit 4, so as to prevent the problem that the LED cathode voltage is instantaneously increased due to an external factor, so as to trigger the protection circuit.
Further, as shown in fig. 1, the protection state detection circuit 2 includes: a seventh fet NM6 and a sixth controllable current source I6.
Wherein, the drain of the seventh fet NM6 is connected to the connection node of the cathode of the LED and the drain of the second fet NM2, the source of the seventh fet NM6 is connected to the ground through the sixth controllable current source I6, and the gate of the seventh fet NM6 is connected to the voltage output terminal VSP of the LED protection circuit.
Specifically, the sixth controllable current source I6 may be a controllable current source in any form, which is not limited in the embodiment of the present invention, the seventh fet NM6 is an N-type fet, and the protection state detection circuit detects a circuit state of the LED driving circuit, that is, an operating state of the LED in real time, and after the short-circuit fault of the LED is eliminated, the current generates a large enough voltage drop on the LED, so as to provide a basis for exiting the short-circuit protection in the next step.
The specific principle of the LED protection circuit is explained below.
As shown in fig. 2, when the LED has a current flowing through it, the LED itself generates a voltage drop, whose magnitude is denoted as VLED, so that the voltage VN at the inverting input terminal of the comparator is VDD-VLED, the reference voltage generated by the reference circuit is VDD-I2 × R1, that is, the voltage VP at the non-inverting input terminal of the comparator is VDD-I2 × R1, when the LED is shorted, VLED is 0, that is, VN is VDD > VP is VDD-I2 × R1, the comparator is inverted, and after the filtering delay circuit processes the comparator, the comparator outputs a high level, and at this time, the fourth fet NM4 is turned on, so that the reference voltage is VDD- (I2+ I3) × R1.
That is, after the LED protection circuit is triggered, since the reference voltages VDD-I2 × R1 and VDD are relatively close to each other, the reference voltage is reduced to VDD- (I2+ I3) × R1 again by providing the fourth fet 4 and the third controllable current source I3, so as to prevent the protection circuit from oscillating due to external factors.
As shown in fig. 2, when the LED protection circuit is triggered, the voltage output terminal VSP of the LED protection voltage outputs a high level, the seventh fet NM6 is turned on, the sixth controllable current source I6 is turned on for monitoring the state of the LED in real time, and if the short-circuit fault is removed, the voltage VN at the inverting input terminal of the comparator is lowered to be lower than the voltage VP at the non-inverting input terminal of the comparator, and at this time, the seventh fet NM6 is turned off, and the sixth controllable current source I6 is automatically turned off.
As shown in fig. 2, when the LED protection circuit is triggered, the third fet NM3 is turned on, and then the first fet NM1 and the second fet NM2 are turned off, so as to protect other circuit structures in case of short circuit of the LED.
Therefore, the protection circuit judges whether the LED has a short circuit phenomenon by directly detecting the magnitude relation between the LED cathode voltage and the reference voltage, and can detect the circuit state of the LED driving circuit, namely the working state of the LED in real time by arranging the protection state detection circuit, so that the scale of the LED protection circuit is greatly reduced, the reliability of the LED protection circuit is improved, and the LED protection state can be automatically released after the fault is released.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (5)
1. An LED protection circuit, comprising: the LED driving circuit, the comparison circuit, the filtering delay circuit, the protection state detection circuit and the reference circuit;
the LED driving circuit is used for providing driving current for the LED; the reference circuit is used for providing a reference voltage; the comparison circuit is used for comparing the reference voltage with the cathode voltage of the LED; the filtering delay circuit is used for filtering the level signal output by the comparison circuit; the protection state detection circuit is used for detecting the working state of the LED;
wherein the LED drive circuit comprises: the LED comprises a first controllable current source, an LED, a first field effect transistor and a second field effect transistor;
one end of the first controllable current source is connected with a voltage input end of the LED protection circuit, the other end of the first controllable current source is connected with a drain electrode of the first field effect transistor, a source electrode of the first field effect transistor is connected with the ground, a grid electrode of the first field effect transistor is connected with a grid electrode of the second field effect transistor, the grid electrode of the first field effect transistor is connected with the drain electrode of the first field effect transistor, the source electrode of the second field effect transistor is connected with the ground, the drain electrode of the second field effect transistor is connected with a cathode of the LED, and an anode of the LED is connected with the voltage input end;
wherein the protection state detection circuit includes: a seventh field effect transistor and a sixth controllable current source;
the drain electrode of the seventh field effect transistor is connected with the connection node of the cathode of the LED and the drain electrode of the second field effect transistor, the source electrode of the seventh field effect transistor is connected with the ground through the sixth controllable current source, and the grid electrode of the seventh field effect transistor is connected with the voltage output end of the LED protection circuit.
2. The LED protection circuit of claim 1, wherein the LED driver circuit further comprises: a third field effect transistor;
the source electrode of the third field effect tube is connected with the ground, the drain electrode of the third field effect tube is connected with the connection node of the grid electrode of the first field effect tube and the grid electrode of the second field effect tube, and the grid electrode of the third field effect tube is connected with the voltage output end of the LED protection circuit.
3. The LED protection circuit of claim 1, wherein the reference circuit comprises: the first resistor, the second controllable current source, the fourth field effect transistor and the third controllable current source;
one end of the first resistor is connected with the voltage input end, the other end of the first resistor is connected with one end of the second controllable current source, the other end of the second controllable current source is connected with the ground, the drain electrode of the fourth field effect transistor is connected with the connection node of the first resistor and the second controllable current source, the source electrode of the fourth field effect transistor is connected with the ground through the third controllable current source, and the grid electrode of the fourth field effect transistor is connected with the voltage output end of the LED protection circuit.
4. The LED protection circuit of claim 3, wherein the comparison circuit comprises: a comparator;
the negative phase input end of the comparator is connected with the connection node of the cathode of the LED and the drain electrode of the second field effect transistor, the positive phase input end of the comparator is connected with the connection node of the first resistor and the second controllable current source, and the output end of the comparator is connected with the filtering delay circuit.
5. The LED protection circuit of claim 4, wherein the filtering delay circuit comprises: the device comprises a fifth field effect transistor, a sixth field effect transistor, a fourth controllable current source, a fifth controllable current source, a capacitor, a Schmitt device and a phase inverter;
wherein a source electrode of the fifth field effect transistor is connected with the voltage input end through the fourth controllable current source, a gate electrode of the fifth field effect transistor is connected with a gate electrode of the sixth field effect transistor, an output end of the comparator is connected with a connection node of the gate electrode of the fifth field effect transistor and the gate electrode of the sixth field effect transistor, a drain electrode of the fifth field effect transistor is connected with a drain electrode of the sixth field effect transistor, a source electrode of the sixth field effect transistor is grounded through the fifth controllable current source, one end of the capacitor is connected with a connection node of the drain electrode of the fifth field effect transistor and the drain electrode of the sixth field effect transistor, the other end of the capacitor is grounded, one end of the schmitt device is connected with a connection node of the drain electrode of the fifth field effect transistor and the drain electrode of the sixth field effect transistor, and the other end of the schmitt device is connected with one end of the phase inverter, the other end of the phase inverter is connected with the voltage output end.
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| CN109152156B (en) * | 2018-10-23 | 2024-02-02 | 上海艾为电子技术股份有限公司 | Constant current source driving circuit |
| CN111641187B (en) * | 2020-06-12 | 2022-08-19 | 上海艾为电子技术股份有限公司 | Overcurrent protection circuit, overcurrent protection method and electronic equipment |
| CN112498272B (en) * | 2020-11-26 | 2022-05-20 | 惠州市德赛西威汽车电子股份有限公司 | Alarm lamp diagnostic circuit and motormeter |
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