CN112004292B - LED overvoltage protection circuit, power module and electronic equipment - Google Patents

LED overvoltage protection circuit, power module and electronic equipment Download PDF

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Publication number
CN112004292B
CN112004292B CN202010769973.7A CN202010769973A CN112004292B CN 112004292 B CN112004292 B CN 112004292B CN 202010769973 A CN202010769973 A CN 202010769973A CN 112004292 B CN112004292 B CN 112004292B
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voltage
circuit
resistor
led
negative
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CN112004292A (en
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开秋月
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Guangzhou Shiyuan Electronics Thecnology Co Ltd
Guangzhou Shikun Electronic Technology Co Ltd
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Guangzhou Shiyuan Electronics Thecnology Co Ltd
Guangzhou Shikun Electronic 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]
    • H05B45/50—Circuit arrangements for operating light-emitting diodes [LED] responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/20—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess voltage
    • 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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Abstract

The application discloses LED overvoltage protection circuit, power module and electronic equipment relates to the electronic circuit design field, and LED overvoltage protection circuit includes: the device comprises a positive voltage overvoltage detection circuit, a negative voltage overvoltage detection circuit, a comparison self-locking circuit and a reference circuit; the comparison self-locking circuit is respectively connected with the reference circuit, the positive voltage overvoltage detection circuit and the negative voltage overvoltage detection circuit. Because the first LED works under the positive voltage input by the positive voltage output end, and the second LED works under the negative voltage input by the negative voltage output end, when the positive voltage input by the positive voltage output end is too high, or when the negative voltage input by the negative voltage output end is too low, the voltage of the positive input end of the first voltage comparator of the comparison self-locking circuit is larger than the first reference voltage of the negative input end, the first voltage comparator outputs a high-level signal, so that the comparison self-locking circuit is always in a self-locking state, and the protection of the power module is triggered.

Description

LED overvoltage protection circuit, power module and electronic equipment
Technical Field
The application relates to the field of electronic circuit design, in particular to an LED overvoltage protection circuit, a power supply module and electronic equipment.
Background
With the development of science and technology, people often use Light Emitting components in life, and Light Emitting Diodes (LEDs) are widely applied to various electronic devices due to the advantages of energy saving, capability of working in a high-speed on-off state, high response speed and the like, so that an overvoltage protection circuit for LEDs becomes one of the important points of research of those in the field.
The backlight scheme at least comprises two paths of LEDs, wherein one path of LEDs is driven by positive voltage, and the other path of LEDs is driven by negative voltage. However, the conventional LED overvoltage protection circuit can only protect the positive voltage driven LED or the negative voltage driven LED, and therefore, an LED overvoltage protection circuit for the above backlight scheme needs to be designed.
Disclosure of Invention
The application provides a LED overvoltage protection circuit, a power supply module and an electronic device, which can solve the technical problems in the related art.
In a first aspect, an embodiment of the present application provides an LED overvoltage protection circuit, where the LED overvoltage protection circuit includes: the device comprises a positive voltage overvoltage detection circuit, a negative voltage overvoltage detection circuit, a comparison self-locking circuit and a reference circuit;
the comparison self-locking circuit is respectively connected with the reference circuit, the positive voltage overvoltage detection circuit and the negative voltage overvoltage detection circuit;
the reference circuit is used for generating a first reference voltage;
the positive voltage overvoltage detection circuit is used for detecting a positive voltage for driving the LED, and inputting a first comparison voltage to the comparison self-locking circuit after voltage division;
the negative voltage overvoltage detection circuit is used for detecting the negative voltage of the driving LED and inputting a second comparison voltage to the comparison self-locking circuit after voltage division;
the comparison self-locking circuit compares a first comparison voltage with the first reference voltage or compares a second comparison voltage with the first reference voltage, and controls the self-locking state of the self-locking circuit according to the comparison result.
In a second aspect, an embodiment of the present application provides a power module of an LED overvoltage protection circuit as in the foregoing embodiments, which includes a control chip, a second voltage comparator, and an optical coupler element, where the overvoltage protection circuit is connected to the control chip through the second voltage comparator and the optical coupler element.
In a third aspect, an electronic device in an embodiment of the present application includes a power module as in any one of the above embodiments.
The beneficial effects brought by the technical scheme provided by some embodiments of the application at least comprise:
the application provides a LED overvoltage crowbar, power module and electronic equipment, LED overvoltage crowbar includes: the device comprises a positive voltage overvoltage detection circuit, a negative voltage overvoltage detection circuit, a comparison self-locking circuit and a reference circuit; the comparison self-locking circuit is respectively connected with the reference circuit, the positive voltage overvoltage detection circuit and the negative voltage overvoltage detection circuit. Because the first LED works under the positive voltage input by the positive voltage output end, and the second LED works under the negative voltage input by the negative voltage output end, when the positive voltage input by the positive voltage output end is too high, or when the negative voltage input by the negative voltage output end is too low, the voltage of the positive input end of the first voltage comparator of the comparison self-locking circuit is larger than the first reference voltage of the negative input end, the first voltage comparator outputs a high-level signal, so that the comparison self-locking circuit is always in a self-locking state, and the protection of the power module is triggered.
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 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 some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative efforts.
Fig. 1 is a schematic structural diagram of an LED circuit according to an embodiment of the present disclosure;
fig. 2 is a schematic structural diagram of an LED overvoltage protection circuit according to an embodiment of the present disclosure;
fig. 3 is a schematic structural diagram of an LED overvoltage protection circuit according to an embodiment of the present disclosure;
FIG. 4 is an enlarged schematic diagram of the circuit structure at A in FIG. 3;
FIG. 5 is a schematic diagram of a power module circuit according to an embodiment of the present application;
fig. 6 shows a schematic structural diagram of a power module circuit according to another embodiment of the present application.
Detailed Description
In order to make the features and advantages of the present application more obvious and understandable, the technical solutions in 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 a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
When the following description refers to the accompanying drawings, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present application. Rather, they are merely examples of circuits and methods consistent with certain aspects of the present application, as detailed in the appended claims.
In the description of the embodiments of the present application, it is to be understood that, in the description of the present application, "a plurality" means two or more unless otherwise specified. "and/or" describes the association relationship of the associated objects, meaning that there may be three relationships, e.g., a and/or B, which may mean: a exists alone, A and B exist simultaneously, and B exists alone. The character "/" generally indicates that the former and latter associated objects are in an "or" relationship.
Fig. 1 shows a schematic structural diagram of an LED circuit according to an embodiment of the present application.
In the LLC backlight scheme shown in fig. 1, the LLC backlight scheme at least includes two paths of LEDs and a rectifying and filtering circuit 150, where one path of LEDs includes the first LED110, and the other path of LEDs includes the second LED130, and the specific number of the first LED110 and the second LED130 can be set according to the actual application, where the positive voltage output terminal 151 of the rectifying and filtering circuit 150 is connected to the first LED110, and the negative voltage output terminal 152 of the rectifying and filtering circuit 150 is connected to the second LED 130. The positive voltage output by the secondary winding of the transformer T in the power module or the power panel is used for driving the first LED110, and the first LED110 works under the driving of the positive voltage; the negative voltage output from the secondary winding of the transformer T is used to drive the second LED130, and the second LED130 is driven by the negative voltage, it can be understood that the positive voltage is a positive value relative to the voltage value of the reference ground, and the negative voltage is a negative value relative to the voltage value of the reference ground.
When an excessively high positive voltage is input to the first LED110 or an excessively low negative voltage is input to the second LED130, a malfunction or damage of the power supply module may be caused, for example, when the LED load is short-circuited, an excessively high voltage is generated across the LED load to cause a damage of the power supply module. In order to avoid the situation, an overvoltage protection circuit is introduced, so that when the power supply module outputs an excessively high positive voltage or an excessively low negative voltage, the power supply module is triggered to be protected, and the power supply module is prevented from being damaged.
Fig. 2 shows a schematic structural diagram of an LED overvoltage protection circuit according to an embodiment of the present application. The LED overvoltage protection circuit 200 includes: a positive voltage overvoltage detection circuit 210, a negative voltage overvoltage detection circuit 220, a comparison self-locking circuit 230 and a reference circuit 240. The comparison self-locking circuit 230 is respectively connected to the positive voltage overvoltage detection circuit 210, the negative voltage overvoltage detection circuit 220 and the reference circuit 240, wherein the connections among the circuits are electrical connections, and the electrical connection manner is not limited herein and may be welding, flat cable connection, and the like.
As shown in fig. 3, the input terminal of the positive voltage overvoltage detection circuit 210 is connected to the positive voltage output terminal 151 of the rectifying and filtering circuit 150, and when the positive voltage overvoltage detection circuit 210 detects the voltage at the positive voltage output terminal 151, a voltage, i.e., a first comparison voltage, is input to the positive input terminal of the first voltage comparator 231 of the comparison self-locking circuit 230 after being divided by the resistors, and if the voltage is greater than the first reference voltage VREF output by the reference circuit 240, a first voltage signal is generated. On one hand, the first voltage signal makes the comparison self-locking circuit 230 always in a self-locking state; on the other hand, the first voltage signal feeds back a backlight overvoltage protection signal, i.e. an LED-OVP signal, which is input to the control chip of the power module, the control chip sends out a control signal to turn off the main control circuit, the rectifying and filtering circuit 150 no longer receives the positive voltage output by the T secondary winding of the main transformer, so that the rectifying and filtering circuit 150 cannot output the positive voltage to the first LED110 through the positive voltage output terminal 151, at this time, the first LED110 does not work, and the power module is protected from being damaged when the positive voltage output by the positive voltage output terminal 151 of the rectifying and filtering circuit 150 is too high.
The input terminal of the negative voltage overvoltage detection circuit 220 is connected to the negative voltage output terminal 152 of the rectifying filter circuit 150, and when the negative voltage overvoltage detection circuit 220 detects the voltage at the negative voltage output terminal 152, a voltage, i.e., a second comparison voltage, is input to the positive input terminal of the first voltage comparator 231 of the comparison self-locking circuit 230 through the negative detection circuit 222 and the negative reference circuit 221 of the negative voltage overvoltage detection module 220, and if the voltage is greater than the first reference voltage VREF output by the reference circuit 240, a second voltage signal is generated. On one hand, the second voltage signal makes the comparison self-locking circuit 230 always in a self-locking state; on the other hand, the second voltage signal feeds back a backlight overvoltage protection signal, i.e. an LED-OVP signal, which is input to the control chip of the power module, the control chip sends a control signal to turn off the main control circuit, so that the rectifying and filtering circuit 150 cannot output a negative voltage to the second LED130 through the negative voltage output terminal 152, at this time, the second LED130 does not work, and thus, when the negative voltage output from the negative voltage output terminal 152 of the rectifying and filtering circuit 150 is too low, the power module is protected from being damaged.
Since the first LED110 operates at the positive voltage input by the positive voltage output terminal 151, and the second LED130 operates at the negative voltage input by the negative voltage output terminal 152, when the positive voltage input by the positive voltage output terminal is too high, or when the negative voltage input by the negative voltage output terminal is too low, the voltage at the positive input terminal of the first voltage comparator 231 of the comparison self-locking circuit 230 is greater than the first reference voltage VREF at the negative input terminal, and the first voltage comparator 231 outputs a high level signal, so that the comparison self-locking circuit is always in a self-locking state, and protection of the power module is triggered. The positive voltage overvoltage detection circuit 210, the negative voltage overvoltage detection circuit 220 and the comparison self-locking circuit 230 may be formed by chips and/or electronic components to achieve the above functions.
Fig. 3 shows a schematic structural diagram of an LED overvoltage protection circuit according to an embodiment of the present application.
The reference circuit 240 of the LED over-voltage protection circuit 200 is connected to the negative input terminal of the first voltage comparator 231 of the comparison self-locking circuit 230, and provides a first reference voltage VREF for the negative input terminal of the first voltage comparator 231. Specifically, the reference circuit 240 includes: a first resistor 241, a first capacitor 242, and a first regulator 243; one end of the first resistor 241 is connected to the external power VCC, the other end of the first resistor 241 is connected to the first end of the first voltage stabilizer 243, the second end of the first voltage stabilizer 243 is connected to the ground, the third end of the first voltage stabilizer 243 is connected to the first end of the first voltage stabilizer 243 and the first end of the first capacitor 242, and the second end of the first capacitor 242 is connected to the ground. The external power source VCC supplies power to the reference circuit 240, the negative voltage overvoltage detection circuit 220, and the comparison self-locking circuit 230, and the voltage of the external power source VCC is greater than the first reference voltage.
The first voltage regulator 243 may be a linear voltage regulator or a voltage regulation chip, for example, the first voltage regulator 243 may be a 431 chip having a reference voltage VREF of 2.5V, and the first voltage regulator 243 can stably output the first reference voltage VREF according to the above circuit connection, where the first reference voltage VREF is 2.5V. The first reference voltage VREF provides a stable reference voltage for the negative input terminal of the first voltage comparator 231 of the comparison self-locking circuit 230, and provides an input voltage for the negative reference circuit 221 of the negative voltage over-voltage detection module 220.
Further, the comparison self-locking circuit 230 includes: a first voltage comparator 231, a first diode 232, a second diode 233, and a second resistor 234. Specifically, the cathode of the first diode 232 is connected to the power module, and can feed back the backlight overvoltage protection signal LED-OVP to the control chip of the power module. The positive electrode of the first diode 232 is connected to the output end of the first voltage comparator 231, the positive electrode of the second diode 233 is connected to the output end of the first voltage comparator 231, the negative electrode of the second diode 233 is connected to one end of the second resistor 234, the other end of the second resistor 234 is connected to the positive input end of the first voltage comparator 231, the first comparison voltage or the second comparison voltage is input to the positive input end of the first voltage comparator 231, the negative input end of the first voltage comparator 231 is connected to the third end of the first voltage regulator 243, and the first reference voltage is input to the negative input end of the first voltage comparator 231. Optionally, a rectifying and filtering unit is disposed between the negative input terminal of the first voltage comparator 231 and the third terminal of the first voltage regulator 243 to eliminate interference of external signals, and when there is a sudden change in voltage or current from the outside, the negative input terminal of the first voltage comparator 231 receives the stable first reference voltage VREF through the filtering circuit. Specifically, the negative input terminal of the first voltage comparator 231 is connected to one end of the third resistor 235 and one end of the second capacitor 236, the other end of the second capacitor 236 is connected to the ground, and the other end of the third resistor 235 is connected to the third end of the first regulator 243.
Further, the positive voltage overvoltage detection circuit 210 includes: a fourth resistor 211, a fifth resistor 212, and a third capacitor 213; one end of the fourth resistor 211 is connected to the positive voltage output terminal 151, the voltage of the positive voltage output terminal 151 is divided and then input to the positive input terminal of the first voltage comparator 231, the other end of the fourth resistor 211 is connected to the positive input terminal of the first voltage comparator 231, one end of the fifth resistor 212, the cathode of the third diode 223, and one end of the third capacitor 213, and the other end of the fifth resistor 212 and the other end of the third capacitor 213 are connected to the ground.
The protection principle of the positive voltage over-voltage detection circuit 210 and the comparison self-locking circuit 230 is that, when the first LED110 is in a normal working state, the voltage of the positive voltage output terminal 151 is divided by the resistance value of the fourth resistor 211 and the fifth resistor 212, so that the voltage of the positive input terminal of the first voltage comparator 231 is smaller than the first reference voltage VREF of the negative input terminal. The ratio or the magnitude of the resistance of the fourth resistor 211 and the resistance of the fifth resistor 212 may be set, so that the voltage divided and input to the positive input terminal of the first voltage comparator 231 is smaller than the first reference voltage VREF of the negative input terminal, and at this time, the output terminal of the first voltage comparator 231 outputs a low level, which may be a control signal or a voltage signal, so that the first LED110 normally operates and the overvoltage protection circuit is not triggered.
When the first LED110 is in an abnormal operating state, for example, the voltage of the positive voltage output terminal 151 is too high, at this time, the fourth resistor 211 and the fifth resistor 212 divide the output voltage of the positive voltage output terminal 151, so that the voltage of the positive input terminal of the first voltage comparator 231 is greater than the first reference voltage VREF of the negative input terminal, and at this time, the output terminal of the first voltage comparator 231 outputs a first high-level signal, that is, the external power VCC. On one hand, the first high level signal passes through the second diode 233, the second resistor 234 and the fifth resistor 212, and by setting the ratio or the magnitude between the resistance values of the second resistor 234 and the fifth resistor 212, the voltage on the fifth resistor 212, that is, the voltage input to the positive input end of the first voltage comparator 231 is greater than the first reference voltage VREF, it is ensured that the output end of the first voltage comparator 231 always outputs a high level signal, so that the comparison self-locking circuit 230 is always in a self-locking state, and the first voltage comparator 231 releases self-locking until the first voltage comparator 231 is powered off; on the other hand, the first high level signal feeds back a backlight overvoltage protection signal, that is, an LED-OVP signal, the LED-OVP signal is input to a control chip of the power module, the control chip sends out a control signal to turn off the main control circuit, the rectifying and filtering circuit 150 does not receive the positive voltage output by the secondary winding of the main transformer T any more, at this time, the first LED110 does not work, and thus, when the positive voltage output by the positive voltage output terminal 151 of the driving rectifying and filtering circuit 150 is too high, the power module is protected from being damaged.
Further, the negative voltage overvoltage detection circuit 220 includes: a negative reference circuit 221 and a negative detection circuit 222. The negative reference circuit 221 includes: a third diode 223, a sixth resistor 224, a seventh resistor 225, a second regulator 226, a fourth capacitor 227, a fifth capacitor 228, an eighth resistor 229, a ninth resistor 2210 and a tenth resistor 2211; the second regulator 226 may be a triode or a chip, in this embodiment, the second regulator 226 may be a 431 chip having a reference voltage of 1.25V, and optionally, the second regulator 226 may be an NPN-type triode, a cathode of the third diode 223 is connected to a positive input terminal of the first voltage comparator 231, an anode of the third diode 223 is connected to one end of the sixth resistor 224, a first end of the second regulator 226, and one end of the seventh resistor 225, another end of the sixth resistor 224 is connected to the ground, another end of the seventh resistor 225 is connected to the external power source VCC and one end of the fourth capacitor 227, another end of the fourth capacitor 227 is connected to the ground, a second end of the second regulator 226 is connected to the ground, a third end of the second regulator 226 is connected to one end of the fifth capacitor 228, one end of the eighth resistor 229, one end of the ninth resistor 243, and one end of the tenth resistor 2211, another end of the fifth capacitor 228 is connected to the ground, another end of the eighth resistor 229 is connected to the third end of the first VREF 2210, an output of the first terminal of the first regulator 221, and another end of the first reference voltage regulator 2210 is connected to the ground, and the reference voltage is connected to the negative reference circuit.
When the second voltage regulator 226 is a 431 chip with a reference voltage of 1.25V, the third terminal of the second voltage regulator provides a stable reference voltage of 1.25V, when the first reference voltage VREF is divided by the eighth resistor 229 and the ninth resistor 2210, so that the voltage at point C shown in fig. 4 is greater than or equal to 1.25V, according to the characteristics of the 431 chip, the voltage at the first terminal of the second voltage regulator 226 is limited to 1.25V, the second voltage regulator 226 is in a conducting state, that is, the first terminal of the second voltage regulator is in a low-resistance state, the external power VCC is connected to the ground through the seventh resistor 225 and the second voltage regulator 226, the voltage input to the forward input terminal of the first voltage comparator 231 is the voltage of the first terminal of the second voltage regulator 226 minus the voltage drop across the third diode 223, the voltage input to the forward input terminal of the first voltage comparator 231 is less than the first reference voltage VREF, and the overvoltage protection circuit is not triggered; when the first reference voltage VREF is divided by the eighth resistor 229 and the ninth resistor 2210, so that the voltage at the point C shown in fig. 4 is less than 1.25V, according to the characteristics of the 431 chip, the second voltage regulator 226 is in an off state at this time, that is, the first terminal of the second voltage regulator is in a high-impedance state, the voltage of the external power source VCC is connected to the ground through the sixth resistor 224 and the seventh resistor 225, and the voltage input to the positive input terminal of the first voltage comparator 231 is greater than the first reference voltage VREF by setting the ratio and the magnitude of the resistances of the sixth resistor 224 and the seventh resistor 225, so that the overvoltage protection circuit is triggered.
Further, the negative-going detection circuit 222 includes: an eleventh resistor 2212 and a twelfth resistor 2213; the other end of the tenth resistor 2211 is connected to one end of the eleventh resistor 2212 and one end of the twelfth resistor 2213, the other end of the eleventh resistor 2212 is connected to the negative voltage output terminal 152, and the other end of the twelfth resistor 2213 is connected to ground.
The protection principle of the negative voltage overvoltage detection circuit 220 and the comparison self-locking circuit 230 is that when the second LED130 normally works, the voltage of the negative voltage output end 152 is divided by the eleventh resistor 2212 and the twelfth resistor 2213, so that the voltage of the third end of the second voltage regulator 226 is greater than or equal to the reference voltage 1.25V of the second voltage regulator 226, at this time, the first end of the second voltage regulator 226 is in a low-resistance state, the external power source VCC is connected to the ground through the seventh resistor 225 and the second voltage regulator tube 226, the overvoltage protection circuit is not triggered, the comparison self-locking circuit cannot trigger self-locking, and the second LED130 normally works under the voltage output by the negative voltage output end 152.
When the LED130 is in the abnormal operating state, if the voltage of the negative voltage output terminal 152 is-200V, which is smaller than the normal voltage-150V when the LED130 is in the normal operating state, the voltage of the node between the eleventh resistor 2212 and the twelfth resistor 2213 is pulled down, that is, the voltage at the point B of fig. 4 is pulled down, which further causes the voltage of the node between the eighth resistor 229 and the ninth resistor 2210 to be pulled down, that is, the voltage at the point C of fig. 4 is pulled down, so that the voltage at the third end of the second voltage stabilizer 226 is smaller than the reference voltage 1.25V of the second voltage stabilizer 226, the first output terminal of the second voltage stabilizer 226 is in the high-impedance state, the external power source VCC is connected to the ground through the sixth resistor 224 and the seventh resistor 225, and the ratio or magnitude of the resistances of the sixth resistor 224 and the seventh resistor 225 is set, that is, so that the voltage at the node between the sixth resistor 224 and the seventh resistor 225 passes through the third diode 223, the positive voltage input terminal of the first voltage comparator 231 is larger than the first negative voltage VREF of the input terminal of the first voltage comparator 231, and the first reference voltage output level of the second voltage comparator 231 is high. On one hand, the second voltage signal makes the comparison self-locking circuit 230 always in a self-locking state; on the other hand, the second voltage signal feeds back a backlight overvoltage protection signal, i.e. an LED-OVP signal, which is input to the control chip of the power module, the control chip sends out a control signal to turn off the main control circuit, at this time, the second LED130 does not work, so that when the negative voltage output by the negative voltage output terminal 152 of the rectifying and filtering circuit 150 is too low, the power module is protected from being damaged.
Fig. 4 is an enlarged schematic diagram of the circuit structure at a in fig. 3. When the voltage at the negative voltage output terminal 152 is too low, the voltage at the third terminal of the second regulator 226 in the negative voltage over voltage detection circuit 220 changes, i.e., the voltage at the node C between the eighth resistor 229 and the ninth resistor 2210 in fig. 4 changes. As shown in FIG. 4, the eighth resistor 229 has a resistance R8, the ninth resistor 2210 has a resistance R9, the tenth resistor 2211 has a resistance R10, and the current flowing through the eighth resistor 229 is I 1 The current flowing through the ninth resistor 2210 is I 2 The current flowing through the tenth resistor 2211 is I 3 When the second LED130 operates in a normal state, the third terminal of the second voltage regulator 226 outputs a stable voltage of 1.25V, and then the current flowing through the tenth resistor 2211 is:
Figure BDA0002614896770000091
the voltage reference value at the point B between the eleventh resistor 2212 and the twelfth resistor 2213 is:
V B ＝1.25-I 3 *R10；
r8 is not greater than R9, when the second LED130 is in a normal operating state, according to the characteristics of the second regulator 226, the voltage of the node C is limited to 1.25V, and it is ensured that the voltage of the point C is equal to 1.25V under a normal condition, so as to ensure that the voltage of the third terminal of the second regulator 226 is 1.25V, at this time, the second regulator 226 is in a conducting state, that is, the first terminal of the second regulator 226 is in a low-resistance state.
When the second LED130 is operated in an abnormal state, for example, when the voltage at the negative voltage output terminal 152 is too low, the voltage at the point B between the eleventh resistor 2212 and the twelfth resistor 2213 is pulled down, and in a transient state, the voltage at the point C is unchanged, and the voltage difference between the point B and the point C is increased, so that the current I3 flowing through the tenth resistor 2211 is increased, so that the current I2 flowing through the ninth resistor 2210 is decreased, and the voltage at the point C is decreased, and when the voltage at the point C is less than 1.25V, the second regulator 226 is in an off state, that is, the first end of the second regulator 226 is in a high impedance state, so as to trigger the overvoltage protection circuit.
In the embodiment of the application, the LED voltage protection circuit successfully realizes the overvoltage protection function of the negative voltage drive LED circuit. The circuit design is flexible, different voltage values can be set according to the actual circuit, and the design is simple, accurate and high in reliability; meanwhile, the positive and negative voltage overvoltage protection circuit is realized in the same circuit, the circuit is not only applied to an LED rectification filter circuit, but also can be extended to a scheme that the positive and negative working circuit needs to be added with overvoltage protection, and the application is wide.
Fig. 5 is a schematic structural diagram of a power module circuit according to an embodiment of the present application. In the circuit of the power module 250 shown in fig. 5, a second voltage comparator 251, an optical coupling element 252 and a control chip 253 are further included. The negative electrode of the first diode 232 is connected to the positive input terminal of the second voltage comparator 251, the negative input terminal of the second voltage comparator 251 is connected to the reference circuit 240, the reference circuit 240 provides the first reference voltage VREF for the negative input terminal of the second voltage comparator 251, the output terminal of the second voltage comparator 251 is connected to the optical coupler element 252, and the optical coupler element 252 is connected to a negative feedback pin of the control chip 253, that is, the FB pin of the control chip 253 shown in fig. 5. When the control chip 253 is in a normal operating state, the normal operating voltage of the FB pin is between 1.9V and 4.3V (including 1.9V and 4.3V). Triggering backlight overvoltage protection, and the specific generation process of generating the LED-OVP signal is as follows: when the voltage at the positive voltage output end 151 is too high, the first voltage comparator 231 outputs an external power VCC, the external power VCC inputs a voltage to the positive input end of the second voltage comparator 251 through the first diode 232, and the voltage is greater than the first reference voltage VREF at this time, the second voltage comparator 251 outputs an external power voltage VCC, the external power voltage VCC enables the primary side light emitting diode 2521 of the optical coupling element 252 to be in a cut-off state, the light emitting diode 2521 does not emit light, the secondary side triode 2522 of the optical coupling element 252 does not receive light and is in the cut-off state, the fourth pin of the optical coupling element 252 outputs a high level, that is, the voltage FB of the fourth pin of the optical coupling element 252 is greater than the normal operating voltage 4.3V of the pin, so that the FB pin in the control chip 253 is in a non-operating state, at this time, the control chip 253 triggers protection, the first driving signal HO for driving the first MOS transistor 254 and the second driving signal LO for driving the second MOS transistor 255 are turned off, the first MOS transistor 254 and the primary side circuit is turned off, so that the primary side protection circuit T does not operate. When the voltage at the negative voltage output terminal 152 is too low, the backlight overvoltage protection is triggered, and an LED-OVP signal is generated: similarly, the first voltage comparator 231 outputs an external power VCC, and the external power VCC inputs a voltage to the positive input terminal of the second voltage comparator 251 through the first diode 232, and the subsequent generation of the LED-OVP signal is consistent with the generation of the LED-OVP signal due to the excessively high voltage at the positive voltage output terminal 151, which is not described herein again.
Fig. 6 shows a schematic structural diagram of a power module circuit according to another embodiment of the present application. Unlike the power module 250 circuit shown in fig. 5, the cathode of the first diode 232 is connected to the negative input terminal of the second voltage comparator 251, the positive input terminal of the second voltage comparator 251 is connected to the reference circuit 240, and the reference circuit 240 provides the first reference voltage VREF for the positive input terminal of the second voltage comparator 251. In the power module 250 of this embodiment, the specific generation process of triggering the backlight overvoltage protection and generating the LED-OVP signal is as follows: when the voltage at the positive voltage output terminal 151 is too high, the first voltage comparator 231 outputs an external power VCC, the external power VCC inputs a voltage to the negative input terminal of the second voltage comparator 251 through the first diode 232, and at this time, the voltage is greater than the first reference voltage VREF, the second voltage comparator 251 outputs a low level, at this time, the primary side light emitting diode 2521 of the optical coupling element 252 is in a saturation conducting state, which can be understood as that the external power VCC is directly grounded after passing through the thirteenth resistor 256 and the primary side light emitting diode 2521 of the optical coupling element 252, at this time, the light emitting diode 2521 emits light, the secondary side triode 2522 of the optical coupling element 252 receives light and is in a saturation conducting state, at this time, the voltage of the fourth pin of the optical coupling element 252 is a voltage drop across the secondary side triode 2522 of the optical coupling element 252, the voltage drop is generally 0.7V, and is less than the normal operating voltage of the FB pin 1.9V, so that the FB pin is in a non-operating state, at this time, the control chip 253 triggers protection, turns off the first driving signal HO for driving the first MOS tube 254 and the second MOS tube LO, and the MOS tube LO drive circuit is turned off, and the MOS tube 250, so that the MOS tube does not operate. When the voltage at the negative voltage output terminal 152 is too low, the backlight overvoltage protection is triggered, and an LED-OVP signal is generated: similarly, the first voltage comparator 231 outputs an external power VCC, the external power VCC inputs a voltage to the negative input terminal of the second voltage comparator 251 through the first diode 232, and a mechanism for subsequently generating the LED-OVP signal is consistent with a mechanism for generating the LED-OVP signal when the voltage of the positive voltage output terminal 151 is too high, which is not described herein again.
The embodiment of the application also provides an electronic device, which comprises the power supply module in the embodiment.
In the embodiments provided in the present application, it should be understood that the disclosed apparatus may be implemented in other manners. For example, the above-described apparatus embodiments are merely illustrative, and for example, a division of modules is merely a logical division, and other divisions may be realized in practice, for example, a plurality of modules or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed coupling or direct coupling or communication connection between each other may be through some interfaces, indirect coupling or communication connection between devices or modules, and may be in an electrical, mechanical or other form.
Modules described as separate parts may or may not be physically separate, and parts displayed as modules may or may not be physical modules, may be located in one place, or may be distributed on a plurality of network modules. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment.
In the above embodiments, the descriptions of the respective embodiments have respective emphasis, and for parts that are not described in detail in a certain embodiment, reference may be made to related descriptions of other embodiments.
In view of the above description of the LED overvoltage protection circuit, the power module and the electronic device provided in the present application, those skilled in the art will recognize that there are variations to the embodiments and the application scope according to the concepts of the present application.

Claims (19)

1. The utility model provides a LED overvoltage crowbar which characterized in that is applied to the LED circuit, the LED circuit includes LED and the second way LED all the way at least, the first way LED is the positive voltage drive, the second way LED is the negative voltage drive, LED overvoltage crowbar includes: the device comprises a positive voltage overvoltage detection circuit, a negative voltage overvoltage detection circuit, a comparison self-locking circuit and a reference circuit;
the comparison self-locking circuit is respectively connected with the reference circuit, the positive voltage overvoltage detection circuit and the negative voltage overvoltage detection circuit;
the reference circuit is used for generating a first reference voltage;
the positive voltage overvoltage detection circuit is used for detecting a positive voltage for driving the first path of LED, and inputting a first comparison voltage to the comparison self-locking circuit after voltage division;
the negative voltage overvoltage detection circuit is used for detecting the negative voltage for driving the second path of LED, and inputting a second comparison voltage to the comparison self-locking circuit after voltage division;
the comparison self-locking circuit compares a first comparison voltage with the first reference voltage or compares a second comparison voltage with the first reference voltage, and controls the self-locking state of the self-locking circuit according to the comparison result.
2. The LED overvoltage protection circuit of claim 1, wherein when the first comparison voltage is greater than the first reference voltage, the comparison self-locking circuit is controlled to be in a self-locking state;
or when the second comparison voltage is greater than the first reference voltage, controlling the comparison self-locking circuit to be in a self-locking state.
3. The LED overvoltage protection circuit of claim 1 or 2, further comprising an external power supply VCC, wherein the external power supply VCC is used for supplying power to the reference circuit, the negative voltage overvoltage detection circuit and the comparison self-locking circuit respectively.
4. The LED overvoltage protection circuit of claim 3, wherein the voltage of the external power supply VCC is greater than the first reference voltage.
5. The LED overvoltage protection circuit of claim 4, wherein said reference circuit comprises: the first resistor, the first capacitor and the first voltage stabilizer;
the one end of first resistance with external power source VCC connects, the other end of first resistance with the first end of first stabiliser is connected, the second end of first stabiliser is connected with the ground wire, the third end of first stabiliser with the first end of stabiliser and the first end of first electric capacity is connected, the second end of first electric capacity with the ground wire is connected.
6. The LED overvoltage protection circuit of claim 5, wherein the first voltage regulator is any one of a linear voltage regulator and a voltage regulator chip, and is capable of generating the stabilized first reference voltage.
7. The LED overvoltage protection circuit of claim 5, wherein the comparison self-locking circuit comprises a first voltage comparator, the first comparison voltage or the second comparison voltage is input to a positive input terminal of the first voltage comparator, and the first reference voltage is input to a negative input terminal of the first voltage comparator.
8. The LED overvoltage protection circuit of claim 7, wherein the comparison self-locking circuit further comprises a first diode, a second diode, and a second resistor;
the anode of the first diode is connected with the output end of the first voltage comparator, and the cathode of the first diode is connected with the power supply module;
the positive pole of the second diode is connected with the output end of the first voltage comparator, the negative pole of the second diode is connected with one end of the second resistor, the other end of the second resistor is connected with the positive input end of the first voltage comparator, and the negative input end of the first voltage comparator is connected with the reference circuit.
9. The LED overvoltage protection circuit of claim 7, wherein a rectifying and filtering unit is disposed between the negative input of the first voltage comparator and the reference circuit.
10. The LED overvoltage protection circuit of claim 8, wherein the positive voltage overvoltage detection circuit comprises: a fourth resistor, a fifth resistor and a third capacitor;
one end of the fourth resistor is connected with a positive voltage output end of the driving LED, the other end of the fourth resistor is connected with a positive input end of the first voltage comparator, one end of the fifth resistor and one end of the third capacitor, and the other end of the fifth resistor and the other end of the third capacitor are connected with the ground wire.
11. The LED overvoltage protection circuit of claim 10, wherein the negative voltage overvoltage detection circuit comprises: the external power source VCC provides a voltage input for the negative reference circuit, and the first reference voltage provides another voltage input for the negative reference circuit.
12. The LED overvoltage protection circuit of claim 11, wherein the negative reference circuit comprises: the third diode, the sixth resistor, the seventh resistor, the second voltage stabilizer, the fourth capacitor, the fifth capacitor, the eighth resistor, the ninth resistor and the tenth resistor;
the negative pole of third diode with the positive input end of first voltage comparator is connected, the positive pole of third diode with the one end of sixth resistance, the first end of second stabiliser and the one end of seventh resistance is connected, the other end of sixth resistance with the ground wire is connected, the other end of seventh resistance with external power source VCC and the one end of fourth capacitance is connected, the other end of fourth capacitance with the ground wire is connected, the second end of second stabiliser with the ground wire is connected, the third end of second stabiliser with the one end of fifth capacitance, the one end of eighth resistance, the one end of ninth resistance and the one end of tenth resistance are connected, the other end of fifth capacitance with the ground wire is connected, the other end of eighth resistance with the third end of first stabiliser is connected, the other end of ninth resistance with the ground wire is connected.
13. The LED overvoltage protection circuit of claim 12, wherein the ninth resistor has a resistance greater than or equal to the eighth resistor.
14. The LED overvoltage protection circuit of claim 12, wherein the second voltage regulator is a regulated chip or NPN transistor having a second reference voltage.
15. The LED overvoltage protection circuit of claim 12, wherein the negative sense circuit comprises: an eleventh resistor and a twelfth resistor;
the other end of the tenth resistor is connected with one end of the eleventh resistor and one end of the twelfth resistor, the other end of the eleventh resistor is connected with a negative voltage output end of the driving LED, and the other end of the twelfth resistor is connected with the ground wire.
16. A power supply module of the LED overvoltage protection circuit according to any one of claims 1 to 15, comprising a control chip, a second voltage comparator, and an optical coupling element, wherein the overvoltage protection circuit is connected to the control chip through the second voltage comparator and the optical coupling element.
17. The power module of claim 16, wherein when the first comparison voltage is greater than the first reference voltage, an over-voltage protection signal is fed back, and the control chip turns off the power module;
or when the second comparison voltage is greater than the first reference voltage, feeding back an overvoltage protection signal and closing the power module.
18. The power supply module according to claim 17, wherein an output terminal of the comparison self-locking circuit is connected to a positive input terminal of the second voltage comparator, the reference circuit is connected to a negative input terminal of the second voltage comparator, and an output terminal of the second voltage comparator is connected to the control chip through the optical coupling element, or;
the output end of the comparison self-locking circuit is connected with the negative input end of the second voltage comparator, the reference circuit is connected with the positive input end of the second voltage comparator, and the output end of the second voltage comparator is connected with the control chip through the optocoupler element.
19. An electronic device, characterized in that it comprises a power supply module according to any one of claims 16 to 18.
CN202010769973.7A 2020-08-03 2020-08-03 LED overvoltage protection circuit, power module and electronic equipment Active CN112004292B (en)

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CN205283092U (en) * 2015-12-31 2016-06-01 浙江朗威微系统有限公司 Integrated circuit dedicated for A -type time -delay low -voltage leakage protector

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