CN111327187A - Display screen constant voltage power supply circuit with overcurrent detection function - Google Patents

Display screen constant voltage power supply circuit with overcurrent detection function Download PDF

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Publication number
CN111327187A
CN111327187A CN202010328106.XA CN202010328106A CN111327187A CN 111327187 A CN111327187 A CN 111327187A CN 202010328106 A CN202010328106 A CN 202010328106A CN 111327187 A CN111327187 A CN 111327187A
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CN
China
Prior art keywords
electrically connected
unit
display screen
power
diode
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Pending
Application number
CN202010328106.XA
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Chinese (zh)
Inventor
崔小燕
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Shenzhen Huiling Information Technology Co ltd
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Shenzhen Huiling Information Technology Co ltd
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Priority to CN202010328106.XA priority Critical patent/CN111327187A/en
Publication of CN111327187A publication Critical patent/CN111327187A/en
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/44—Circuits or arrangements for compensating for electromagnetic interference in converters or inverters
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/165—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values
    • G01R19/16533—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values characterised by the application
    • G01R19/16538—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values characterised by the application in AC or DC supplies
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/165—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values
    • G01R19/16566—Circuits and arrangements for comparing voltage or current with one or several thresholds and for indicating the result not covered by subgroups G01R19/16504, G01R19/16528, G01R19/16533
    • G01R19/16571—Circuits and arrangements for comparing voltage or current with one or several thresholds and for indicating the result not covered by subgroups G01R19/16504, G01R19/16528, G01R19/16533 comparing AC or DC current with one threshold, e.g. load current, over-current, surge current or fault current
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/22—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
    • G09G3/30—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels
    • G09G3/32—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED]
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/33507—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters
    • H02M3/33523—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters with galvanic isolation between input and output of both the power stage and the feedback loop
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
    • H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
    • H02M7/06—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes without control electrode or semiconductor devices without control electrode
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0048—Circuits or arrangements for reducing losses
    • H02M1/0054—Transistor switching losses
    • H02M1/0058—Transistor switching losses by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/4815—Resonant converters
    • 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
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • Theoretical Computer Science (AREA)
  • Electromagnetism (AREA)
  • Dc-Dc Converters (AREA)

Abstract

The invention discloses a display screen constant voltage power supply circuit with overcurrent detection, which is characterized by comprising a power interface, an EMI filtering unit, a rectifying unit, a pi-type filtering unit, a boosting chopping unit, a resonance module, a transformer, a second rectifying unit, a second pi-type filtering unit, a display screen power interface, a constant voltage control unit and a current limiting unit; the invention has the advantages of strong stability, high safety, low power consumption, good adaptability and good market application value.

Description

Display screen constant voltage power supply circuit with overcurrent detection function
Technical Field
The invention relates to the field of display screen circuits, in particular to a display screen constant-voltage power supply circuit with overcurrent detection function.
Background
The led display screen is a new type of information display medium which is rapidly developed. With the continuous development of economy in China, the method is widely applied to public places such as stations, hotels, banks, hospitals and the like. The display screen power supply is an important component of the display screen power supply and is mainly used for providing necessary working current for the display screen light-emitting diode and ensuring normal display of a screen body; meanwhile, the power supply overload capacity is poor, the utilization rate of the display screen body is low, the power consumption of the display screen body changes along with the content, color and brightness of a picture when the display screen body works, and therefore, the voltage and the current fluctuate greatly, a constant-voltage display screen power supply circuit with overcurrent detection is needed, although part of constant-voltage power supply circuits appear in the market at present, because a switching tube of a topological circuit of the constant-voltage display screen power supply circuit is a hard switch, the Vds voltage and the current of an MOS tube can be overlapped when the display screen body is switched on and switched off, and the area where the voltage and the current are overlapped, namely the switching-on loss and the switching-off loss.
The prior art has defects and needs to be improved.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention provides a display screen constant-voltage power supply circuit with overcurrent detection.
The invention provides a constant-voltage power supply circuit with an overcurrent detection function for a display screen, which comprises a power supply interface, a constant-voltage power supply circuit and a control circuit, wherein the power supply interface is electrically connected to commercial power and is used for inputting power to the constant-voltage power supply circuit;
the input end of the EMI filtering unit is electrically connected with the power interface, and the EMI filtering unit is used for inhibiting high-frequency interference and equipment interference;
the input end of the rectifying unit is electrically connected with the output end of the EMI filtering unit, and the rectifying unit is used for carrying out bridge rectification on the alternating current output by the EMI filtering unit and converting the alternating current into direct current;
the input end of the pi-type filtering unit is electrically connected with the output end of the rectifying unit, and the pi-type filtering unit is used for carrying out filtering operation on direct current;
the input end of the boost chopper unit is electrically connected with the output end of the pi-type filter unit, and the boost chopper unit is used for boosting the direct current;
the input end of the resonance module is electrically connected with the output end of the boost chopper unit, and the resonance module is used for converting direct current into alternating current;
the first coil on the primary side of the transformer is electrically connected with the output end of the resonance module, the first coil on the secondary side of the transformer is provided with a coil with a tap, the first coil on the secondary side of the transformer is electrically connected with the input end of the second rectifying unit, and the second coil of the transformer is electrically connected with the voltage stabilizing unit;
the second rectifying unit is used for rectifying alternating current generated by the first coil on the secondary side of the transformer, and the output end of the second rectifying unit is electrically connected with the second pi-type filtering unit;
the second pi-type filtering unit is used for filtering the direct current rectified by the second rectifying unit, the output end of the second pi-type filtering unit is electrically connected with a display screen power interface, and the display screen power interface is electrically connected with at least one display screen;
the constant voltage control unit is used for outputting constant voltage to the power interface of the display screen, the input end of the constant voltage control unit is electrically connected to the positive electrode of the power interface of the display screen, and the output end of the constant voltage control unit is electrically connected to the control end of the resonance module;
the current limiting unit is used for limiting current at the power interface of the display screen, the input end of the current limiting unit is electrically connected to the negative electrode of the power interface of the display screen, and the output end of the current limiting unit is electrically connected to the control end of the resonance module.
Preferably, the starting circuit is further provided, and is electrically connected to the second coil on the primary side of the transformer, the second coil on the primary side of the transformer supplies power to the starting circuit, the starting circuit is electrically connected to the output end of the pi filter unit, the output end of the starting circuit is electrically connected to the power management chip U4 of the boost chopper unit and the switching power chip U6 of the resonant module, respectively, and the starting circuit is configured to supply power to the power management chip U4 of the boost chopper unit and the switching power chip U6 of the resonant module.
Preferably, the second coil on the primary side of the transformer is electrically connected to the starting circuit through a voltage stabilizing circuit, an input end of the voltage stabilizing circuit is electrically connected to the second coil on the primary side of the transformer, the power management chip U4 of the boost chopper unit and the switching power chip U6 of the resonant module are both electrically connected to an output end of the voltage stabilizing circuit, and the voltage stabilizing circuit supplies power to the power management chip U4 of the boost chopper unit and the switching power chip U6 of the resonant module.
Preferably, the constant voltage control unit and the current limiting unit are electrically connected to the control end of the resonance module through a photoelectric coupler, the constant voltage control unit and the current limiting unit are electrically connected to the photoelectric coupler through a reverse-connection switching diode, the anode of the switching diode is electrically connected to the cathode of the light source of the photoelectric coupler, and the anode of the light source of the photoelectric coupler is electrically connected to the 12V power supply through a resistor.
Preferably, the constant voltage control unit is provided with a voltage reference chip U7, the control end of the voltage reference chip U7 is electrically connected to the middle end of the series voltage-dividing resistor, one end of the series voltage-dividing resistor is electrically connected to the anode of the display screen power interface, the other end of the series voltage-dividing resistor is grounded, the anode of the voltage reference chip U7 is connected to one cathode of the switching diode, and the cathode of the voltage reference chip U7 is grounded.
Preferably, the current limiting unit includes a current limiting detection resistor R60 and a dual operational amplifier, the detection resistor R60 is connected in series between the negative electrode of the display screen power interface and the ground, the dual operational amplifier includes an amplifier AR1B and a comparator AR1A, the non-inverting input terminal of the amplifier AR1B is electrically connected to the negative electrode of the display screen power interface, the inverting input terminal of the amplifier AR1B is grounded through a resistor R58, the inverting input terminal of the amplifier AR1B is electrically connected to the output terminal of the amplifier AR1B through a resistor R66, the inverting input terminal of the amplifier AR1B is further electrically connected to the output terminal of the amplifier AR1B through a series resistor R65 and a capacitor C37, so as to perform a filtering operation, the output terminal of the amplifier AR1B is electrically connected to the inverting input terminal of the comparator AR1A, the non-inverting input terminal of the comparator AR1A is electrically connected to a reference voltage, and the output terminal of the.
Preferably, the switch diode is a double switch diode with the model number of BAS21A, and the constant voltage control unit and the current limiting unit are electrically connected to two cathodes of the double switch diode respectively.
Preferably, the voltage stabilizing circuit comprises a rectifier diode D8, a zener diode D7, a transistor Q5, a filter capacitor C15 and a capacitor C16, the anode of the rectifier diode D8 is electrically connected to the second coil on the primary side of the transformer, the rectifier diode D8 is electrically connected to the collector of the transistor Q5 through a resistor R39, the collector of the transistor Q5 is electrically connected to the base of the transistor Q5 through a resistor R38, the base of the transistor Q5 is grounded through a zener diode D7, the base of the transistor Q5 is grounded through a capacitor C15 for filtering, and the power management chip U4 of the boost chopper unit and the switching power chip U6 of the resonant module are both electrically connected to the emitter of the transistor Q5.
Preferably, the starting circuit comprises an NMOS transistor Q3, a triode Q2, a diode D2, a diode D6 and a zener diode D1, the drain of the NMOS tube Q3 is electrically connected with the output end of the pi-type filter unit, the source of the drain of the NMOS tube Q3 is electrically connected with the power management chip U4 of the boost chopper unit and the switching power chip U6 of the resonance module through series resistors R9 and R10, the gate of the NMOS tube Q3 is electrically connected with the collector of the triode Q2, the gate and the drain of the NMOS tube Q3 are electrically connected with the drain of the NMOS tube Q3 through series resistors R1, R2, R7 and R8, a zener diode D1 and a reverse diode D2 are electrically connected between the source and the gate of the NMOS tube Q3, the emitter of the triode Q2 is grounded, the base of the triode Q2 is connected with the emitter of the triode Q5 through a resistor R6, and the emitter of the triode Q5 is electrically connected to the power management chip U4 of the boost chopper unit and the switching power chip U6 of the resonant module through the forward diode D6.
Preferably, the cathode of the diode D6 is grounded through parallel capacitors C7 and C8 for filtering.
Compared with the prior art, the constant voltage control unit has the advantages that the constant voltage output of the power interface of the display screen is realized by arranging the constant voltage control unit, and the stability of output voltage is ensured; by arranging the current limiting unit, the overcurrent limitation of the power interface of the display screen is realized, and the stability is improved; by arranging the resonance module, the soft switching of the constant-voltage power supply topological circuit is realized, the judgment loss of conduction loss is reduced, the power consumption is reduced, and the energy is saved; the boost chopper unit is arranged to boost the direct current and is matched with the resonance module to realize stable voltage output; by arranging the EMI filtering unit, the rectifying unit and the pi-shaped filtering unit, the conversion from commercial power to power supply of a display screen is realized, and the adaptability is enhanced; the invention has the advantages of strong stability, high safety, low power consumption, good adaptability and good market application value.
Drawings
FIG. 1 is a block diagram of the overall structure of the present invention;
FIG. 2 is a circuit diagram of the power interface, EMI filter, rectifier unit and pi-filter unit of the present invention;
FIG. 3 is a circuit diagram of a boost chopper unit according to the present invention;
FIG. 4 is a circuit diagram of a resonant module of the present invention;
FIG. 5 is a circuit diagram of a transformer, a second rectifying unit, a second pi-type filtering unit, a constant voltage control unit, and a current limiting unit according to the present invention;
FIG. 6 is a diagram of a voltage regulator circuit according to the present invention;
FIG. 7 is a diagram of a start-up circuit according to the present invention.
Detailed Description
The technical features mentioned above are combined with each other to form various embodiments which are not listed above, and all of them are regarded as the scope of the present invention described in the specification; also, modifications and variations may be suggested to those skilled in the art in light of the above teachings, and it is intended to cover all such modifications and variations as fall within the true spirit and scope of the invention as defined by the appended claims.
In order to facilitate an understanding of the invention, the invention is described in more detail below with reference to the accompanying drawings and specific examples. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
It will be understood that when an element is referred to as being "secured to" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "electrically connected" to another element, it can be directly electrically connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "left," "right," and the like as used herein are for descriptive purposes only.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
The present invention will be described in detail with reference to the accompanying drawings.
As shown in fig. 1, a constant voltage power supply circuit with an overcurrent detection function for a display screen includes a power interface, where the power interface is electrically connected to a commercial power and inputs power to the constant voltage power supply circuit;
the input end of the EMI filtering unit is electrically connected with the power interface, and the EMI filtering unit is used for inhibiting high-frequency interference and equipment interference;
the input end of the rectifying unit is electrically connected with the output end of the EMI filtering unit, and the rectifying unit is used for carrying out bridge rectification on the alternating current output by the EMI filtering unit and converting the alternating current into direct current;
the input end of the pi-type filtering unit is electrically connected with the output end of the rectifying unit, and the pi-type filtering unit is used for carrying out filtering operation on direct current;
the input end of the boost chopper unit is electrically connected with the output end of the pi-type filter unit, and the boost chopper unit is used for boosting the direct current;
the input end of the resonance module is electrically connected with the output end of the boost chopper unit, and the resonance module is used for converting direct current into alternating current;
the first coil on the primary side of the transformer is electrically connected with the output end of the resonance module, the first coil on the secondary side of the transformer is provided with a coil with a tap, the first coil on the secondary side of the transformer is electrically connected with the input end of the second rectifying unit, and the second coil of the transformer is electrically connected with the voltage stabilizing unit;
the second rectifying unit is used for rectifying alternating current generated by the first coil on the secondary side of the transformer, and the output end of the second rectifying unit is electrically connected with the second pi-type filtering unit;
the second pi-type filtering unit is used for filtering the direct current rectified by the second rectifying unit, the output end of the second pi-type filtering unit is electrically connected with a display screen power interface, and the display screen power interface is electrically connected with at least one display screen;
the constant voltage control unit is used for outputting constant voltage to the power interface of the display screen, the input end of the constant voltage control unit is electrically connected to the positive electrode of the power interface of the display screen, and the output end of the constant voltage control unit is electrically connected to the control end of the resonance module;
the current limiting unit is used for limiting current at the power interface of the display screen, the input end of the current limiting unit is electrically connected to the negative electrode of the power interface of the display screen, and the output end of the current limiting unit is electrically connected to the control end of the resonance module.
Preferably, the starting circuit is further provided, and is electrically connected to the second coil on the primary side of the transformer, the second coil on the primary side of the transformer supplies power to the starting circuit, the starting circuit is electrically connected to the output end of the pi filter unit, the output end of the starting circuit is electrically connected to the power management chip U4 of the boost chopper unit and the switching power chip U6 of the resonant module, respectively, and the starting circuit is configured to supply power to the power management chip U4 of the boost chopper unit and the switching power chip U6 of the resonant module.
Preferably, the second coil on the primary side of the transformer is electrically connected to the starting circuit through a voltage stabilizing circuit, an input end of the voltage stabilizing circuit is electrically connected to the second coil on the primary side of the transformer, the power management chip U4 of the boost chopper unit and the switching power chip U6 of the resonant module are both electrically connected to an output end of the voltage stabilizing circuit, and the voltage stabilizing circuit supplies power to the power management chip U4 of the boost chopper unit and the switching power chip U6 of the resonant module.
As shown in fig. 5, preferably, the constant voltage control unit and the current limiting unit are both electrically connected to the control end of the resonance module through a photocoupler, and the constant voltage control unit and the current limiting unit are both electrically connected to the photocoupler through a reverse-connection switching diode, an anode of the switching diode is electrically connected to a cathode of a light source of the photocoupler, and an anode of the light source of the photocoupler is electrically connected to the 12V power supply through a resistor.
Preferably, the constant voltage control unit is provided with a voltage reference chip U7, the control end of the voltage reference chip U7 is electrically connected to the middle end of the series voltage-dividing resistor, one end of the series voltage-dividing resistor is electrically connected to the anode of the display screen power interface, the other end of the series voltage-dividing resistor is grounded, the anode of the voltage reference chip U7 is connected to one cathode of the switching diode, and the cathode of the voltage reference chip U7 is grounded.
Preferably, the current limiting unit includes a current limiting detection resistor R60 and a dual operational amplifier, the detection resistor R60 is connected in series between the negative electrode of the display screen power interface and the ground, the dual operational amplifier includes an amplifier AR1B and a comparator AR1A, the non-inverting input terminal of the amplifier AR1B is electrically connected to the negative electrode of the display screen power interface, the inverting input terminal of the amplifier AR1B is grounded through a resistor R58, the inverting input terminal of the amplifier AR1B is electrically connected to the output terminal of the amplifier AR1B through a resistor R66, the inverting input terminal of the amplifier AR1B is further electrically connected to the output terminal of the amplifier AR1B through a series resistor R65 and a capacitor C37, so as to perform a filtering operation, the output terminal of the amplifier AR1B is electrically connected to the inverting input terminal of the comparator AR1A, the non-inverting input terminal of the comparator AR1A is electrically connected to a reference voltage, and the output terminal of the.
Preferably, the switch diode is a double switch diode with the model number of BAS21A, and the constant voltage control unit and the current limiting unit are electrically connected to two cathodes of the double switch diode respectively.
As shown in fig. 6, preferably, the voltage stabilizing circuit includes a rectifier diode D8, a zener diode D7, a transistor Q5, and filter capacitors C15 and C16, the anode of the rectifier diode D8 is electrically connected to the second coil of the primary side of the transformer, the rectifier diode D8 is electrically connected to the collector of the transistor Q5 through a resistor R39, the collector of the transistor Q5 is electrically connected to the base of the transistor Q5 through a resistor R38, the base of the transistor Q5 is grounded through a zener diode D7, the base of the transistor Q5 is grounded through a capacitor C15 for filtering, and the power management chip U4 of the boost chopper unit and the switching power chip U6 of the resonance module are both electrically connected to the emitter of the transistor Q5.
As shown in fig. 7, the start-up circuit preferably includes an NMOS transistor Q3, a transistor Q2, a diode D2, a diode D6, and a zener diode D1, the drain of the NMOS tube Q3 is electrically connected with the output end of the pi-type filter unit, the source of the drain of the NMOS tube Q3 is electrically connected with the power management chip U4 of the boost chopper unit and the switching power chip U6 of the resonance module through series resistors R9 and R10, the gate of the NMOS tube Q3 is electrically connected with the collector of the triode Q2, the gate and the drain of the NMOS tube Q3 are electrically connected with the drain of the NMOS tube Q3 through series resistors R1, R2, R7 and R8, a zener diode D1 and a reverse diode D2 are electrically connected between the source and the gate of the NMOS tube Q3, the emitter of the triode Q2 is grounded, the base of the triode Q2 is connected with the emitter of the triode Q5 through a resistor R6, and the emitter of the triode Q5 is electrically connected to the power management chip U4 of the boost chopper unit and the switching power chip U6 of the resonant module through the forward diode D6.
Preferably, the cathode of the diode D6 is grounded through parallel capacitors C7 and C8 for filtering.
The working principle of the invention is as follows: the power supply interface is electrically connected to the mains supply, the mains supply is filtered by the EMI filter, the influence of the fluctuation of a mains supply power grid on the constant-voltage power supply circuit of the display screen is prevented, and the influence of the fluctuation of the constant-voltage power supply circuit of the display screen on the mains supply power grid is also prevented by the EMI filter; the commercial power is rectified by the rectifying unit and converted into direct current, then the direct current is filtered by the pi-type filtering unit and converted into smoother direct current, meanwhile, the output end of the pi-type filtering unit supplies power to a power management chip U4 of the boost chopping unit and a switch power chip U6 of the resonance module through an NMOS (N-channel metal oxide semiconductor) tube Q3, at the moment, the voltage of the direct current is about 310V, the boost chopping unit performs boost operation, namely, boost is performed through a boost circuit formed in the boost chopping unit, and the specific boost voltage value is determined by the voltage value of the input end of a multiplier of the power management chip U4 of the boost chopping unit; the boosted direct current is converted into alternating current through the resonance module, soft switching of a topological circuit is achieved, Vds voltage and current of the MOS tube cannot be overlapped when the MOS tube is conducted and judged, the switching tube is switched on and off when the voltage and the current are zero by means of oscillation, and switching loss is greatly reduced; the alternating current carries out voltage conversion through a transformer, a second coil on the primary side of the transformer is electrically connected with a starting circuit through a voltage stabilizing circuit to supply power to a power supply management chip U4 of the boost chopper unit and a switch power supply chip U6 of the resonance module, and meanwhile, the side, supplied with power by the output end of the pi-type filter unit, of the starting circuit is disconnected due to judgment of an NMOS (N-channel metal oxide semiconductor) tube Q3, so that high loss caused by power supply of the output end of the pi-type filter unit is reduced; the second rectifying unit rectifies a first coil on the secondary side of the transformer, and meanwhile, the second pi-shaped filtering unit filters and supplies power to a display screen electrically connected to a power interface of the display screen; the constant voltage control unit monitors the power of display screen power source kneck simultaneously and feeds back to the resonance module through optoelectronic coupler and adjusts, and the current-limiting unit monitors the electric current on the display screen power source kneck to feed back through optoelectronic coupler and adjust to the resonance module, realize constant voltage's output, overflow the restriction simultaneously, guarantee security and stability.
The working principle of the constant voltage control unit is that the control end of the voltage reference chip U7 receives the voltage value of the middle end of the series voltage-dividing resistor, when the voltage at the power interface of the display screen rises, the voltage value received by the voltage reference chip U7 also rises and exceeds the internal reference voltage value, the voltage reference chip U7 is conducted, the photoelectric coupler, the switch diode Q8 and the voltage reference chip U7 form a loop, the light emitting source of the photoelectric coupler emits light, the light receiver of the photoelectric coupler is conducted, the voltage of the receiving end of the switch power chip U6 of the resonance module is pulled low, the switch power chip U6 adjusts the switching frequency of the resonance module, the switching frequency of the resonance module is reduced, the output voltage is reduced, and the constant output of the voltage is maintained.
The working principle of the current limiting unit is as follows: in the return circuit that the display screen power source interface constitutes, through monitoring the voltage value of detection resistance R60, after amplifier AR1B enlargies, get into comparator AR1A, when the voltage value after amplifier AR1B enlargies is high with the reference voltage of comparing AR 1A's normal phase input end electric connection, comparator AR1A outputs low level, switch diode Q8 switches on, the light emitting source of optoelectronic coupler is luminous, the light receiver of optoelectronic coupler switches on, the receiving terminal voltage of the switching power supply chip U6 of resonance module is pulled low, then switching power supply chip U6 adjusts the switching frequency of resonance module, reduce output voltage, realize the reduction of electric current.
In the second embodiment, as shown in fig. 2, a fuse is disposed between the EMI filter unit and the mains interface, and the fuse is connected in series to the loop of the mains.
Third, the EMI filter unit includes a varistor MOV1, a common mode inductor T1 and T2, the varistor MOV1 is electrically connected between the lines of the utility power L, N, and the capacitor CX1 is electrically connected between the lines of the utility power L, N, both ends of the capacitor CX1 are electrically connected to both ends of the input end of the common mode inductor T1, the capacitor CX2 is electrically connected between both ends of the output side of the common mode inductor T1, and both ends of the output side of the common mode inductor T1 are connected to the resistors R3 and R4 in series, both ends of the output side of the common mode inductor T1 are grounded through the capacitors CY1 and CY2, both ends of the output side of the common mode inductor T1 are electrically connected to both ends of the input side of the common mode inductor T2, and both ends of the output side of the common mode inductor.
In a fourth embodiment, two ends of the output side of the common mode inductor T2 are electrically connected to the input end of the rectifying unit, and the rectifying unit is configured to perform full-bridge rectification.
In a fifth embodiment, the pi filter unit includes an inductor L2, capacitors C1 and C2, and two ends of the inductor L2 are grounded through the capacitors C1 and C2, respectively, for filtering.
Sixth embodiment, as shown in fig. 3, the boost chopper unit includes a power management chip U4, a transformer T3, a diode D4, and an NMOS tube Q4, the power management chip is set to be L6562A, an output terminal of the pi filter unit is electrically connected to an anode of the diode D5, an anode of the diode D5 is electrically connected to one end of a primary side of the transformer T3, the other end of the primary side of the transformer T3 is electrically connected to a drain of the NMOS tube Q4, one end of a secondary side of the transformer T3 is electrically connected to a 5 pin of the power management chip U4 for performing zero crossing detection, the other end of the secondary side of the transformer T3 is grounded, the other end of the primary side of the transformer T3 is electrically connected to a cathode of the diode D5 through a forward diode D4, a cathode of the diode D5 is electrically connected to one end of the thermistor RT1, one end pin of the power management chip U4 is electrically connected to the other end of the thermistor 686, the 1 pin of the power management chip U4 is electrically connected to the 2 pin of the power management chip U4 through a capacitor C5, the 1 pin of the power management chip U4 is electrically connected to the 2 pin of the power management chip U4 through a series capacitor C6 and a resistor R16, the 1 pin of the power management chip U4 is grounded through a resistor R13, the 3 pin of the power management chip U4 is electrically connected to the anode of a diode D4 through a series resistor R4, the 3 pin of the power management chip U4 is grounded through a series resistor R4, the 6 pin of the power management chip U4 is grounded, the 7 pin of the power management chip U4 is connected to the gate of an NMOS tube Q4 through a resistor R4, the 7 pin of the power management chip U4 is connected to the gate of the NMOS tube Q4 through a resistor R4, the 7 pin of the power management chip U4 is electrically connected to the cathode of the diode D4, and the source of the NMOS tube Q4 are connected to the ground through a resistor R4 and the NMOS tube 4 in parallel connection resistor R4 of the power management chip U4. The gate and the source of the NMOS transistor Q4 are electrically connected through a resistor R14, the source of the NMOS transistor Q4 is electrically connected through a resistor R12 to the 4-pin of the power management chip U4, and the power management chip U4, the NMOS transistor Q4, the transformer T3, and the diode D4 form a boost circuit.
Seventh embodiment, the resonant module includes a switching power chip U6, NMOS transistors Q6 and Q7, the model of the switching power chip U6 is set to L6599, pin 1 of the switching power chip U6 is connected to the high-potential end of the photo-electric coupler through series resistors R34, R33, R31 and R28, pin 1 and pin 3 of the switching power chip U6 are respectively connected to ground through a capacitor C6 and a capacitor C6, pin 2 of the switching power chip U6 is connected to ground through a resistor R6, pin 4 and pin 5 of the switching power chip U6 are connected to ground through a resistor R6, pin 5 of the switching power chip U6 is electrically connected to the middle ends of the resistors R6 and R6, pin 7 of the switching power chip U6 is connected to ground through a capacitor C6, pin 7 of the switching power chip U6 is electrically connected to the middle ends of the resistors R6 and R6, and the capacitor C6 is connected to ground through the capacitor C6, a 12 pin of the switching power chip U6 is electrically connected to a negative electrode of the diode D6, a 6 pin of the switching power chip U6 is electrically connected to one end of the primary side first coil of the transformer through the inverse diode D10, an anode of the diode D10 is electrically connected to one end of the primary side first coil of the transformer through the series capacitor C20 and the resistor R41, the 6 pin of the switching power chip U6 is grounded through the parallel capacitor C19 and the resistor R40, an anode of the diode D10 is grounded through the inverse diode D9, an 8 pin and a 10 pin of the switching power chip U6 are electrically connected through the resistor R42, a 10 pin of the switching power chip U6 is grounded, an 11 pin of the switching power chip U6 is electrically connected to a gate of the NMOS tube Q6 through the resistor R44, an 11 pin of the switching power chip U6 is electrically connected to a gate of the inverse diode D11 of the NMOS tube Q6, a source of the NMOS tube Q6 is grounded, a gate of the NMOS tube Q53 is electrically connected to the resistor R43, the drain of the NMOS transistor Q6 is electrically connected to the source of the NMOS transistor Q7, the 15 th pin of the switching power supply chip U6 is electrically connected to the gate of the NMOS transistor Q7 through a resistor R46, the 15 th pin of the switching power supply chip U6 is electrically connected to the gate of the NMOS transistor Q7 through a reverse diode D12, a resistor R45 is electrically connected between the gate and the source of the NMOS transistor Q7, the 14 th pin of the switching power supply chip U6 is electrically connected to the source of the NMOS transistor Q7, the 16 th pin and the 14 th pin of the switching power supply chip U6 are electrically connected through a capacitor C12, the source of the NMOS transistor Q7 is electrically connected to the other end of the primary side of the transformer, the drain of the NMOS transistor Q7 is electrically connected to the other end of the piezoresistor RT1, and the other end of the piezoresistor RT1 is grounded through series resistors R37, R35, R32.
In an eighth embodiment, the second rectifying unit is configured as a full-bridge rectifier, the first coil on the secondary side of the transformer is configured as a tapped coil, the second pi-type filtering unit includes capacitors C30, C31, C38 and an inductor L3, an output end of the second rectifying unit is grounded through capacitors C30 and C31, an output end of the second rectifying unit is electrically connected to one end of an inductor L3, the other end of the inductor L3 is electrically connected to a detection resistor R60 through a capacitor C38 and grounded, and the other end of the inductor L3 is grounded through a series resistor R61 and a detection resistor R60.
In the ninth embodiment, the reference voltage is provided by a reference voltage chip U3, the model of the reference voltage chip U3 is TL431, the control terminal of the reference voltage chip U3 is electrically connected to the high potential terminal, the low potential terminal of the reference voltage chip U3 is grounded, the high potential terminal of the reference voltage chip U3 is the reference voltage, the high potential terminal of the reference voltage chip U3 is connected to a 12V power supply through a resistor R59, the 12V power supply is provided by a second coil on the secondary side of the transformer, and the second coil on the secondary side of the transformer outputs the 12V power supply through a second voltage stabilizing unit.
The second voltage stabilizing unit comprises a diode D14A, a diode D14B, a triode Q9 and a voltage stabilizing diode D13, wherein one end of a second coil on the secondary side of the transformer is electrically connected with a tap of a first coil on the primary side of the transformer, the other end of the second coil on the secondary side of the transformer is connected with the anode of the diode D14A, the cathode of the diode D14A is connected with the ground through a resistor C25, the cathode of the diode D14A is connected with the collector of the triode Q9 through a resistor R53, the collector and the base of the triode Q9 are electrically connected through a resistor R52, the base of the triode Q9 is grounded through a voltage stabilizing diode D13, the base of the triode Q9 is grounded through a capacitor C26, the emitter of the triode Q9 is electrically connected with the positive pole of the diode D14B, the cathode of the diode D14B outputs 12V power, and the cathode of the diode D14B performs filtering through a capacitor C58.
And a capacitor C23 is arranged between the ground and the earth for filtering.
The technical features mentioned above are combined with each other to form various embodiments which are not listed above, and all of them are regarded as the scope of the present invention described in the specification; also, modifications and variations may be suggested to those skilled in the art in light of the above teachings, and it is intended to cover all such modifications and variations as fall within the true spirit and scope of the invention as defined by the appended claims.

Claims (10)

1. A display screen constant voltage power supply circuit with overcurrent detection is characterized by comprising a power interface, wherein the power interface is electrically connected to commercial power and is used for inputting power to the constant voltage power supply circuit;
the input end of the EMI filtering unit is electrically connected with the power interface, and the EMI filtering unit is used for inhibiting high-frequency interference and equipment interference;
the input end of the rectifying unit is electrically connected with the output end of the EMI filtering unit, and the rectifying unit is used for carrying out bridge rectification on the alternating current output by the EMI filtering unit and converting the alternating current into direct current;
the input end of the pi-type filtering unit is electrically connected with the output end of the rectifying unit, and the pi-type filtering unit is used for carrying out filtering operation on direct current;
the input end of the boost chopper unit is electrically connected with the output end of the pi-type filter unit, and the boost chopper unit is used for boosting the direct current;
the input end of the resonance module is electrically connected with the output end of the boost chopper unit, and the resonance module is used for converting direct current into alternating current;
the first coil on the primary side of the transformer is electrically connected with the output end of the resonance module, the first coil on the secondary side of the transformer is provided with a coil with a tap, the first coil on the secondary side of the transformer is electrically connected with the input end of the second rectifying unit, and the second coil of the transformer is electrically connected with the voltage stabilizing unit;
the second rectifying unit is used for rectifying alternating current generated by the first coil on the secondary side of the transformer, and the output end of the second rectifying unit is electrically connected with the second pi-type filtering unit;
the second pi-type filtering unit is used for filtering the direct current rectified by the second rectifying unit, the output end of the second pi-type filtering unit is electrically connected with a display screen power interface, and the display screen power interface is electrically connected with at least one display screen;
the constant voltage control unit is used for outputting constant voltage to the power interface of the display screen, the input end of the constant voltage control unit is electrically connected to the positive electrode of the power interface of the display screen, and the output end of the constant voltage control unit is electrically connected to the control end of the resonance module;
the current limiting unit is used for limiting current at the power interface of the display screen, the input end of the current limiting unit is electrically connected to the negative electrode of the power interface of the display screen, and the output end of the current limiting unit is electrically connected to the control end of the resonance module.
2. The display panel constant voltage power supply circuit with over-current detection as claimed in claim 1, further comprising a start circuit, wherein the start circuit is electrically connected to the second coil on the primary side of the transformer, the second coil on the primary side of the transformer supplies power to the start circuit, the start circuit is electrically connected to the output terminal of the pi filter unit, the output terminal of the start circuit is electrically connected to the power management chip U4 of the boost chopper unit and the switching power chip U6 of the resonant module, respectively, and the start circuit is configured to supply power to the power management chip U4 of the boost chopper unit and the switching power chip U6 of the resonant module.
3. The display screen constant voltage power supply circuit with the over-current detection function as claimed in claim 2, wherein the second coil on the primary side of the transformer is electrically connected to the start circuit through a voltage stabilizing circuit, the input end of the voltage stabilizing circuit is electrically connected to the second coil on the primary side of the transformer, the power management chip U4 of the boost chopper unit and the switching power chip U6 of the resonant module are both electrically connected to the output end of the voltage stabilizing circuit, and the voltage stabilizing circuit supplies power to the power management chip U4 of the boost chopper unit and the switching power chip U6 of the resonant module.
4. The constant voltage power supply circuit with the function of detecting the overcurrent of the display screen of claim 1, wherein the constant voltage control unit and the current limiting unit are electrically connected to the control end of the resonance module through a photoelectric coupler, the constant voltage control unit and the current limiting unit are electrically connected to the photoelectric coupler through a reverse-coupled switching diode, an anode of the switching diode is electrically connected to a cathode of a light source of the photoelectric coupler, and an anode of the light source of the photoelectric coupler is electrically connected to a 12V power supply through a resistor.
5. The constant voltage power supply circuit for display screen with over-current detection as claimed in claim 4, wherein the constant voltage control unit has a voltage reference chip U7, the control terminal of the voltage reference chip U7 is electrically connected to the middle terminal of a series voltage-dividing resistor, one terminal of the series voltage-dividing resistor is electrically connected to the positive terminal of the power interface of the display screen, the other terminal is grounded, the positive terminal of the voltage reference chip U7 is connected to a negative terminal of the switch diode, and the negative terminal of the voltage reference chip U7 is grounded.
6. The constant voltage power supply circuit as claimed in claim 4, wherein the current limiting unit comprises a current limiting detection resistor R60 and a dual operational amplifier, the detection resistor R60 is connected in series between the negative terminal of the power interface of the display screen and ground, the dual operational amplifier comprises an amplifier AR1B and a comparator AR1A, the non-inverting input terminal of the amplifier AR1B is electrically connected to the negative terminal of the power interface of the display screen, the inverting input terminal of the amplifier AR1B is connected to ground through a resistor R58, the inverting input terminal of the amplifier AR1B is electrically connected to the output terminal of the amplifier AR1B through a resistor R66, the inverting input terminal of the amplifier AR1B is further electrically connected to the output terminal of the amplifier AR1B through a series resistor R65 and a capacitor C37 for performing a filtering operation, the output terminal of the amplifier AR1B is electrically connected to the inverting input terminal of the comparator AR1A, and the non-inverting input terminal of the comparator AR1A is electrically connected, the output terminal of the comparator AR1A is electrically connected to the other cathode of the switching diode.
7. The constant voltage power supply circuit for display screen with over-current detection as claimed in claim 5 or 6, wherein the switch diode is configured as a dual switch diode with model number BAS21A, and the constant voltage control unit and the current limiting unit are electrically connected to two cathodes of the dual switch diode respectively.
8. The constant voltage power supply circuit with the function of over-current detection for the display screen of claim 3, wherein the voltage regulator circuit comprises a rectifier diode D8, a zener diode D7, a transistor Q5, and filter capacitors C15 and C16, the positive electrode of the rectifier diode D8 is electrically connected to the second coil of the primary side of the transformer, the rectifier diode D8 is electrically connected to the collector of the transistor Q5 through a resistor R39, the collector of the transistor Q5 is electrically connected to the base of the transistor Q5 through a resistor R38, the base of the transistor Q5 is grounded through a zener diode D7, the base of the transistor Q5 is grounded through a capacitor C15 for filtering, and the power management chip U4 of the boost chopper unit and the switching power supply chip U6 of the resonant module are both electrically connected to the emitter of the transistor Q5.
9. The constant voltage power supply circuit with the function of over-current detection for the display screen of claim 8, wherein the start-up circuit comprises an NMOS transistor Q3, a transistor Q2, a diode D2, a diode D6 and a Zener diode D1, the drain of the NMOS transistor Q3 is electrically connected to the output terminal of the pi-type filter unit, the source of the drain of the NMOS transistor Q3 is electrically connected to the power management chip U4 of the boost chopper unit and the switching power chip U6 of the resonator module through series resistors R9 and R10, the gate of the NMOS transistor Q3 is electrically connected to the collector of the transistor Q2, the gate and the drain of the NMOS transistor Q3 are electrically connected to the drain of the NMOS transistor Q3 through series resistors R2, R2, R7 and R8, the Zener diode D1 and the inverted diode D2 are electrically connected between the source and the gate of the NMOS transistor Q3, the emitter of the transistor Q2 is grounded, the base of the transistor Q2 is connected to the emitter of the transistor Q2 through the resistor R2, and the emitter of the triode Q5 is electrically connected to the power management chip U4 of the boost chopper unit and the switching power chip U6 of the resonant module through the forward diode D6.
10. The constant-voltage power supply circuit with the over-current detection function for the display screen of claim 9, wherein the cathode of the diode D6 is grounded through parallel capacitors C7 and C8 for filtering.
CN202010328106.XA 2020-04-23 2020-04-23 Display screen constant voltage power supply circuit with overcurrent detection function Pending CN111327187A (en)

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