CN114825939A - High-precision switching power supply circuit based on double-group output of single transformer - Google Patents

High-precision switching power supply circuit based on double-group output of single transformer Download PDF

Info

Publication number
CN114825939A
CN114825939A CN202210223770.7A CN202210223770A CN114825939A CN 114825939 A CN114825939 A CN 114825939A CN 202210223770 A CN202210223770 A CN 202210223770A CN 114825939 A CN114825939 A CN 114825939A
Authority
CN
China
Prior art keywords
circuit
voltage
power supply
transistor
output
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
CN202210223770.7A
Other languages
Chinese (zh)
Inventor
余祚尚
曾维禄
肖荣军
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
TPV Electronic Technology Fujian Co Ltd
Original Assignee
TPV Electronic Technology Fujian Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by TPV Electronic Technology Fujian Co Ltd filed Critical TPV Electronic Technology Fujian Co Ltd
Priority to CN202210223770.7A priority Critical patent/CN114825939A/en
Publication of CN114825939A publication Critical patent/CN114825939A/en
Pending legal-status Critical Current

Links

Images

Classifications

    • 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
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/10—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers
    • H02H7/12—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers
    • 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
    • H02M1/12—Arrangements for reducing harmonics from ac input or output
    • 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
    • H02M1/14—Arrangements for reducing ripples from dc input or output
    • 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
    • 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
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/06—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using resistors or capacitors, e.g. potential divider
    • 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

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Dc-Dc Converters (AREA)

Abstract

The invention discloses a high-precision switching power supply circuit based on double-group output of a single transformer, wherein a direct current source circuit is connected with a wiring end of a primary side winding of the transformer through an isolation type DC-DC voltage reduction circuit, the direct current source circuit is connected with an LED lamp tube driving circuit, a secondary side winding of the transformer is provided with at least two winding voltage output ends, one winding voltage output end outputs a first direct current, the other winding voltage output end outputs a second direct current, the first direct current supplies power to a main circuit board circuit, a liquid crystal panel T-CON circuit and a USB circuit, and the second direct current supplies power to open type pluggable OPS-C equipment and an AMP audio power amplifier circuit through a voltage stabilizing and standby control circuit; the first direct current is connected to the input end of the sampling feedback circuit, and the output end of the sampling feedback circuit is connected to the isolated DC-DC voltage reduction circuit so as to regulate output electric energy together with the transformer. On the premise of high voltage precision, the invention still has better material cost of electronic parts, so that the product has more market competitiveness.

Description

High-precision switching power supply circuit based on double-group output of single transformer
Technical Field
The invention relates to the technical field of switching power supplies of liquid crystal display products, in particular to a double-output high-precision switching power supply circuit based on a single transformer.
Background
As shown in fig. 1, a functional block diagram of an internal power board circuit of a large-sized high-power lcd product, wherein after the isolated DC-DC voltage-reducing circuit is reduced by a transformer, a first secondary winding of the transformer generates a 12V DC power to supply power to a back-end main substrate circuit, a liquid crystal panel T-CON circuit and a USB circuit after being rectified and filtered by a first set of output rectifying and filtering circuits, and a second secondary winding of the transformer generates an 18V DC power to the back-end after being rectified and filtered by a second set of output rectifying and filtering circuits, as follows: the AMP loudspeaker power amplifier circuit supplies power, because when a transformer outputs two sets of voltages, only one set of output voltage can be selected as follows: the 12V output acts as the main feedback, while the other set of output voltages is: the 18V output serves as secondary feedback, and the voltage of the primary feedback output can be basically controlled in the following steps: within 12V + -5% precision, and the sub-feedback is insufficient, when the 12V output belt is heavily loaded and the 18V output belt is lightly loaded, the 18V output will drift upwards as follows: around 19.8V, i.e.: the accuracy of the set of voltages with 18V output can only be controlled in the following steps: 18V 10%, even worse.
If the 18V output is required to be supplied to the equipment such as an open pluggable operating system OPS-C and the like to work, because the lower limit voltage of the operation of the OPS-C equipment is 12V and the upper limit voltage thereof is 19V, the output specification of 18V +/-10% exceeds the upper limit value of the input voltage of the OPS-C equipment and cannot meet the design requirement, the framework circuit shown in figure 2 needs to adopt two groups of isolation type DC-DC voltage reduction circuits, and each group of output is respectively and independently fed back to the corresponding isolation type DC-DC voltage reduction circuit. Aiming at the requirement that the output voltage is two groups of outputs, and because a rear-end power supply circuit or equipment requires that the precision of the output voltage is controlled within 5 percent, even products with higher precision requirements of the output voltage are adopted, the power architecture scheme shown in the figure 2 is adopted, so that the design cost of BOM materials is increased, and the market competitiveness of liquid crystal display products in the aspect of price is reduced.
Disclosure of Invention
The technical scheme adopted by the invention is as follows:
the double-group output high-precision switching power supply circuit based on the single transformer comprises a direct current source circuit, an isolation type DC-DC voltage reduction circuit, a transformer and an LED lamp tube driving circuit, wherein the direct current source circuit is connected with a wiring terminal of a primary side winding of the transformer through the isolation type DC-DC voltage reduction circuit, the direct current source circuit is connected with the LED lamp tube driving circuit, and the output end of the LED lamp tube driving circuit is connected with and drives an LED lamp tube to work;
the secondary side winding of the transformer is provided with two windings for outputting different direct current voltages, one winding voltage output end is connected with the first rectifying and filtering circuit and generates a first direct current after being rectified and filtered by the first rectifying and filtering circuit, the other winding voltage output end is connected with the second rectifying and filtering circuit and generates a second direct current after being rectified and filtered by the second rectifying and filtering circuit, the first direct current supplies power to the main substrate circuit, the T-CON circuit and the USB circuit of the liquid crystal panel, and the second direct current supplies power to the open type pluggable OPS-C equipment and the AMP audio power amplifier circuit through the voltage stabilizing and standby control circuit; the first direct current is connected to the input end of the sampling feedback circuit, and the output end of the sampling feedback circuit is connected to the isolated DC-DC voltage reduction circuit, so that the isolated DC-DC voltage reduction circuit and the transformer can regulate output electric energy;
the voltage stabilizing and standby control circuit comprises a bias power supply circuit and a voltage stabilizing circuit, wherein the bias power supply circuit provides a bias working voltage for the voltage stabilizing circuit through a resistor R3; the voltage stabilizing circuit comprises an MOS tube Q1, an operational amplifier OP and a transistor Q2, wherein the drain electrode of the MOS tube Q1 is connected with second direct current, and the source electrode of the MOS tube Q1 is respectively connected with the power supply input end of the open pluggable OPS-C device and the power supply input end of the AMP audio power amplifier circuit; the grid of the MOS tube Q1 is respectively connected with the output end of the bias power supply circuit, the collector of the transistor Q2 and the Vcc power supply end of the operational amplifier OP, the base of the transistor Q2 is electrically connected with the output end of the operational amplifier OP, the positive input end of the operational amplifier OP is respectively connected with one end of the pull-down resistor R1 and one end of the pull-up resistor R2, the other end of the pull-up resistor R2 is electrically connected with the source of the MOS tube Q1, the negative input end of the operational amplifier OP is electrically connected with a reference voltage source Vref, and the emitter of the transistor Q2, the grounding end of the operational amplifier OP, the grounding end of the reference voltage source Vref and the other end of the pull-down R1 are connected with the secondary side ground.
Further, the dc source circuit outputs a dc voltage of about 400V.
Furthermore, the bias power supply circuit comprises a transistor Q4 and a voltage regulator tube ZD1, wherein the collector of the transistor Q4 is electrically connected with one end of a resistor R7, the base of the transistor Q4 is electrically connected with one end of a resistor R6 and the cathode of the voltage regulator tube ZD1 respectively, the emitter of the transistor Q4 is electrically connected with one end of a capacitor C1 and one end of a resistor R3 respectively, the other end of the resistor R3 is connected with the grid of a Mos tube Q1, and the other ends of the resistor R6 and the resistor R7 are electrically connected with the output end of the LED lamp tube driving circuit
Specifically, the bias power supply circuit gets power from the output terminal of the LED tube driving circuit 6 through resistors R6 and R7, and generates a bias power supply voltage Ve (Q4) = VZD1-0.7V =27V-0.7V =26.3V through the emitter of an NPN transistor Q4 in the circuit, and if ZD1 selects a 27V zener diode, the 26.3V voltage provides a bias working voltage to the gate terminal of the MOS transistor Q1 through the bias resistor R3.
Further, the MOS transistor Q1 can be selected as: the transistor Q2 is an NPN transistor, the value of the pull-down resistor R1 is 10K omega, the value of the pull-up resistor R2 is 64.8K omega, and the 27V voltage stabilizing diode is selected from ZD 1.
Further, the following steps: the secondary side winding of the transformer is also provided with a bias power supply winding, the bias power supply circuit comprises a MOS tube Q3, a transistor Q5 and a Vbias output rectifying and filtering circuit, the output end of the secondary side bias power supply winding of the transformer is electrically connected with the input end of the Vbias output rectifying and filtering circuit, the output end of the Vbias output rectifying and filtering circuit is electrically connected with one end of a resistor R3, the other end of the resistor R3 is electrically connected with one end of a resistor R4 and the emitter of a transistor Q5, the base of the transistor Q5 is electrically connected with the other end of the resistor R4 and one end of the resistor R5, the collector of the transistor Q5 is electrically connected with the grid of a MOS tube Q1, the other end of the resistor R5 is electrically connected with the drain of the MOS tube Q3, the grid of the MOS tube Q3 is electrically connected with a standby control signal PS _ ON output by the main substrate, and the source of the MOS tube Q3 is electrically connected with the secondary side ground.
Further, the MOS transistor Q3 is an N-channel MOS transistor, and the transistor Q5 is a PNP transistor. The Vbias output rectifying and filtering circuit is an existing conventional circuit.
Further, the OP, the transistor Q2 and the reference voltage source Vref adopt integrated devices with corresponding functions, and the integrator is TL431 or AZ 431.
Further, the direct current power supply circuit is electrically connected with the primary side winding of the transformer through an isolated DC-DC voltage reduction circuit
Further, the direct current source circuit comprises an EMI filter circuit, a bridge rectifier circuit, a PFC booster circuit and a power frequency large-capacitance filter circuit which are electrically connected in sequence, commercial alternating current is connected with the EMI filter circuit and is subjected to EMI filtering by the EMI filter circuit, full-wave rectification is carried out by the bridge rectifier circuit to form unidirectional pulsating direct current voltage, boosting is carried out by the PFC booster circuit, and filtering is carried out by the power frequency large-capacitance filter circuit to generate direct current voltage of about 400V.
Further, commercial alternating current is as follows: 110V/60HZ and 220V/50HZ power frequency alternating current.
Furthermore, the main substrate circuit respectively outputs a standby control signal PS _ ON and an LED lamp switch signal ON/OFF and an LED lamp dimming signal DIM, wherein the PS _ ON signal is used for controlling the liquid crystal display product to enter a normal working mode or a standby working mode, the ON/OFF signal is used for controlling whether the LED lamp driving circuit works, and the DIM signal is used for controlling the brightness and darkness of the liquid crystal display picture.
By adopting the technical scheme, when the LED lamp tube driving circuit works normally, the main substrate circuit outputs a PS _ ON signal and an ON/OFF signal as high-level signals respectively, so that the LED lamp tube driving circuit works normally. When the liquid crystal display product enters the standby mode, the main substrate circuit respectively outputs a PS _ ON signal and an ON/OFF signal which are low level signals, so that the LED lamp tube driving circuit stops working and the bias power supply circuit outputs zero voltage, namely when the liquid crystal display product enters the standby mode, the grid electrode of the MOS tube Q1 cannot obtain the bias voltage and the bias voltage is changed into a cut-OFF state from conduction between the drain electrode and the source electrode, namely: in the standby state, the second output voltage is cut off by the MOS transistor Q1 and cannot be provided to the back-end open pluggable OPS-C device and the AMP audio power amplifier circuit to operate, so that the second output voltage is in a more energy-saving and power-saving state.
Drawings
The invention is described in further detail below with reference to the accompanying drawings and the detailed description;
FIG. 1 is a schematic diagram of a power board circuit function block inside a large-sized high-power LCD product in the prior art;
FIG. 2 is a schematic diagram of a high-precision switching power supply circuit based on two isolated DC-DC voltage reduction circuits in the prior art;
FIG. 3 is a schematic structural diagram of a first embodiment of a dual-output high-precision switching power supply circuit based on a single transformer according to the present invention;
fig. 4 is a schematic diagram of a working state relationship according to a first embodiment of the present invention.
Fig. 5 is a schematic structural diagram of a second embodiment of the high-precision switching power supply circuit based on a double-output of a single transformer.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application.
As shown in one of fig. 3 to 5, the present invention discloses a high-precision switching power supply circuit based on double outputs of a single transformer,
the double-group output high-precision switching power supply circuit based on the single transformer comprises a direct current source circuit, an isolation type DC-DC voltage reduction circuit, a transformer and an LED lamp tube driving circuit, wherein the direct current source circuit is connected with a wiring terminal of a primary side winding of the transformer through the isolation type DC-DC voltage reduction circuit, the direct current source circuit is connected with the LED lamp tube driving circuit, and the output end of the LED lamp tube driving circuit is connected with and drives an LED lamp tube to work;
the secondary side winding of the transformer is provided with two windings for outputting different direct current voltages, one winding voltage output end is connected with the first rectifying and filtering circuit and generates a first direct current after being rectified and filtered by the first rectifying and filtering circuit, the other winding voltage output end is connected with the second rectifying and filtering circuit and generates a second direct current after being rectified and filtered by the second rectifying and filtering circuit, the first direct current supplies power to the main substrate circuit, the T-CON circuit and the USB circuit of the liquid crystal panel, and the second direct current supplies power to the open type pluggable OPS-C equipment and the AMP audio power amplifier circuit through the voltage stabilizing and standby control circuit; the first direct current is connected to the input end of the sampling feedback circuit, and the output end of the sampling feedback circuit is connected to the isolated DC-DC voltage reduction circuit, so that the isolated DC-DC voltage reduction circuit and the transformer can regulate output electric energy;
the voltage stabilizing and standby control circuit comprises a bias power supply circuit and a voltage stabilizing circuit, wherein the bias power supply circuit provides a bias working voltage for the voltage stabilizing circuit through a resistor R3; the voltage stabilizing circuit comprises an MOS tube Q1, an operational amplifier OP and a transistor Q2, wherein the drain electrode of the MOS tube Q1 is connected with second direct current, and the source electrode of the MOS tube Q1 is respectively connected with the power supply input end of the open pluggable OPS-C device and the power supply input end of the AMP audio power amplifier circuit; the grid of the MOS tube Q1 is respectively connected with the output end of the bias power supply circuit, the collector of the transistor Q2 and the Vcc power supply end of the operational amplifier OP, the base of the transistor Q2 is electrically connected with the output end of the operational amplifier OP, the positive input end of the operational amplifier OP is respectively connected with one end of the pull-down resistor R1 and one end of the pull-up resistor R2, the other end of the pull-up resistor R2 is electrically connected with the source of the MOS tube Q1, the negative input end of the operational amplifier OP is electrically connected with a reference voltage source Vref, and the emitter of the transistor Q2, the grounding end of the operational amplifier OP, the grounding end of the reference voltage source Vref and the other end of the pull-down R1 are connected with the secondary side ground.
Further, the dc source circuit outputs a dc voltage of about 400V.
Furthermore, the bias power supply circuit comprises a transistor Q4 and a voltage regulator tube ZD1, wherein the collector of the transistor Q4 is electrically connected with one end of a resistor R7, the base of the transistor Q4 is electrically connected with one end of a resistor R6 and the cathode of the voltage regulator tube ZD1 respectively, the emitter of the transistor Q4 is electrically connected with one end of a capacitor C1 and one end of a resistor R3 respectively, the other end of the resistor R3 is connected with the grid of a Mos tube Q1, and the other ends of the resistor R6 and the resistor R7 are electrically connected with the output end of the LED lamp tube driving circuit
Specifically, the bias power supply circuit obtains power from the output terminal of the LED tube driving circuit 6 through the resistors R6 and R7, and generates a bias power supply voltage Ve (Q4) = VZD1-0.7V =27V-0.7V =26.3V through the emitter of the NPN transistor Q4 in the circuit, and if ZD1 selects a 27V zener diode, the 26.3V voltage provides a bias working voltage to the gate terminal of the MOS transistor Q1 through the bias resistor R3.
Further, the MOS transistor Q1 can be selected as: the transistor Q2 is an NPN transistor, the value of the pull-down resistor R1 is 10K omega, the value of the pull-up resistor R2 is 64K omega, and the ZD1 is a 27V voltage stabilizing diode.
Further, as shown in fig. 5, as another embodiment, the secondary side winding of the transformer further has a bias power supply winding, the bias power supply circuit includes a MOS transistor Q3, a transistor Q5 and a Vbias output rectifying and filtering circuit, an output terminal of the secondary side bias power supply winding of the transformer is electrically connected to an input terminal of the Vbias output rectifying and filtering circuit, an output terminal of the Vbias output rectifying and filtering circuit is electrically connected to one end of a resistor R3, the other end of the resistor R3 is electrically connected to one end of a resistor R4 and an emitter of a transistor Q5, a base of the transistor Q5 is electrically connected to the other end of the resistor R4 and one end of the resistor R5, a collector of the transistor Q5 is electrically connected to a gate of the MOS transistor Q1, the other end of the resistor R5 is electrically connected to a drain of the MOS transistor Q3, the MOS transistor Q3 is electrically connected to a standby control signal PS _ ON output from the gate main board, and a source of the transistor Q3 is electrically connected to the secondary side.
Further, the MOS transistor Q3 is an N-channel MOS transistor, and the transistor Q5 is a PNP transistor. The Vbias output rectifying and filtering circuit is an existing conventional circuit.
Further, the OP, the transistor Q2 and the reference voltage source Vref adopt integrated devices with corresponding functions, and the integrator is TL431 or AZ 431.
Further, the direct current power supply circuit is electrically connected with the primary side winding of the transformer through an isolated DC-DC voltage reduction circuit
Further, the direct current source circuit comprises an EMI filter circuit, a bridge rectifier circuit, a PFC booster circuit and a power frequency large-capacitance filter circuit which are electrically connected in sequence, commercial alternating current is connected with the EMI filter circuit and is subjected to EMI filtering by the EMI filter circuit, full-wave rectification is carried out by the bridge rectifier circuit to form unidirectional pulsating direct current voltage, boosting is carried out by the PFC booster circuit, and filtering is carried out by the power frequency large-capacitance filter circuit to generate direct current voltage of about 400V.
Further, commercial alternating current is as follows: 110V/60HZ and 220V/50HZ power frequency alternating current.
Furthermore, the main substrate circuit respectively outputs a standby control signal PS _ ON and an LED lamp switch signal ON/OFF and an LED lamp dimming signal DIM, wherein the PS _ ON signal is used for controlling the liquid crystal display product to enter a normal working mode or a standby working mode, the ON/OFF signal is used for controlling whether the LED lamp driving circuit works, and the DIM signal is used for controlling the brightness and darkness of the liquid crystal display picture.
By adopting the technical scheme, when the LED lamp tube driving circuit works normally, the main substrate circuit outputs a PS _ ON signal and an ON/OFF signal as high-level signals respectively, so that the LED lamp tube driving circuit works normally. When the liquid crystal display product enters the standby mode, the main substrate circuit respectively outputs a PS _ ON signal and an ON/OFF signal which are low level signals, so that the LED lamp tube driving circuit stops working and the bias power supply circuit outputs zero voltage, namely when the liquid crystal display product enters the standby mode, the grid electrode of the MOS tube Q1 cannot obtain the bias voltage and the bias voltage is changed into a cut-OFF state from conduction between the drain electrode and the source electrode, namely: in the standby state, the second output voltage is cut off by the MOS transistor Q1 and cannot be provided to the back-end open pluggable OPS-C device and the AMP audio power amplifier circuit to operate, so that the second output voltage is in a more energy-saving and power-saving state.
The following detailed description of the specific principles of the present invention is provided by way of example in fig. 3:
commercial alternating currents are as follows: 110V/60HZ or 220V/50HZ power frequency alternating current is subjected to EMI filtering by an EMI filter circuit 1, then is subjected to full-wave rectification by a bridge rectifier circuit 2 to generate a unidirectional pulsating direct current voltage, then is subjected to boosting by a PFC boosting circuit 3 and is subjected to filtering by a power frequency large-capacitance filter circuit 4 to generate a direct current of about 400V, the direct current of about 400V is used as the power supply input voltage of an isolation type DC-DC step-down circuit 5, the output end of the isolation type DC-DC step-down circuit 5 is electrically connected with a primary side winding of a transformer 7, after voltage conversion is carried out by the transformer 7, the output voltage of a primary side winding of the transformer 7 is subjected to rectification filtering by a first group of output rectification filter circuits 8 to generate a 12V direct current, and a sampling feedback circuit 12 carries out 100% sampling on the 12V output direct current to be fed back to the isolation type DC-DC step-down circuit 5, output electric energy adjustment is timely carried out through the isolated DC-DC voltage reduction circuit 5 and the transformer 7, and the accuracy control of 12V output direct current voltage is ensured to be within 5 percent, namely: the lower limit value of the working voltage is as follows: 11.4V, the upper limit value of the working voltage is 12.6V, and the rear end comprises the following components: and the main substrate circuit, the T-CON circuit of the liquid crystal panel, the USB and other circuit equipment supply power. The output voltage of the secondary side second winding of the transformer 7 generates direct current of about 17.3V-19.8V after being rectified and filtered by the second group of output rectifying and filtering circuits 9, and then generates 18V +/-5% after being stabilized by the voltage stabilizing circuit 13, namely: the lower limit value of the working voltage is as follows: 17.1V, the working voltage upper limit is 18.9V direct current and gives the rear end as follows: the open pluggable OPS-C device supplies power and the AMP audio amplification circuit 11.
The direct current of about 400V output by the power frequency large capacitance filter circuit 4 is also provided for the LED lamp tube driving circuit 6 to supply power, after the power conversion is carried out by the LED lamp tube driving circuit 6, a constant current is output to the LED lamp tube 14 to supply power under the condition that the DIM dimming signal is not changed, and the LED lamp tube driving circuit 6 is turned OFF to stop working when the PS _ ON standby signal and the ON/OFF signal are in the standby mode from the High level High to the Low level Low, so that the energy and power of the liquid crystal display product are more saved under the standby mode condition.
The voltage stabilizing circuit of the voltage stabilizing and standby control circuit 13 comprises a precise voltage stabilizing circuit consisting of a Q1N-channel MOS tube, an operational amplifier OP, a Q2 NPN transistor, a reference voltage source Vref, a sampling pull-down resistor R1, a sampling pull-up resistor R2 and a voltage stabilizing circuit bias power supply resistor R3, the drain of the Q1N-channel MOS tube is electrically connected with the output end of the second rectifying and filtering circuit 9, the source of the Q1N-channel MOS tube is electrically connected with the power supply input ends of the open pluggable OPS-C device and the AMP audio power amplifier circuit, the grid of the Q1N-channel MOS tube is electrically connected with one end of the power supply bias resistor R3, the collector of the NPN transistor Q2 and the operational amplifier Vcc power supply end, the base of the Q2 OP is electrically connected with the operational amplifier OP output end, the positive input end of the operational amplifier OP is electrically connected with one ends of the R1 and R2 resistors, the other end of the R2 resistor is electrically connected with the Q1N-channel MOS tube power supply source, and the negative input end of the operational amplifier OP is electrically connected with the reference voltage source Vref, the emitter of the Q2 NPN transistor, the grounding end of the operational amplifier OP, the grounding end of the reference power supply electrode Vref and the other end of the R1 resistor are connected with the secondary side grounding. The OP, Q2 NPN transistors, reference voltage source Vref can be integrated devices such as: TL431 or AZ431 is substituted, and the Source terminal voltage of a Q1N channel MOS transistor Source electrode is Vs (Q1) =2.5V (R1+ R2)/R1=2.5V (10K Ω +64.8K Ω)/10K Ω =18.7V, wherein R1=10K Ω, and R2=64.8K Ω;
when 18V output is overloaded such as: when I21=7.5A, the output voltage of the second group of output rectifying and filtering circuits is 17.3V ≤ V21 ≤ 18.7V, and at this time, the drain and source of the Q1N-channel MOS transistor are in a complete conduction region (also referred to as a variable resistance region) Q1 MOS transistor loss P21 (Q1) = I21 × I21 × rds (on) =7.5A × 3m Ω =0.168W, and assuming that when I21=7.5A, the Q1N-channel MOS transistor has a conduction impedance rds (on) =3m Ω;
when 18V outputs light load as follows: when I22=0.1A, the second group of output rectifying and filtering circuit outputs V22>18.7V, such as: v22=19.8V when the Q1N channel MOS transistor works in the amplification region, Δ V = V22-Vs (Q1) =19.8V-18.7V =1.1V voltage falls between the drain and the source of the MOS transistor, Q1 MOS transistor loss P22 (Q1) = I22 Δ V =0.1A 1.1V =0.11W, with the voltage regulator, since the accuracy of the AS431 reference voltage source Vref itself is within 1%, the accuracy of the 18V output voltage output by the Q1 MOS transistor source terminal is very high, it is easy to control the voltage accuracy within 5%, Q1N channel MOS transistor can be selected AS a MOS transistor with a withstand voltage of about 30V-40V, and the MOS transistor manufacturer in this withstand voltage region can design the impedance rds (on) at full conduction AS about 3m relatively easily, so that the conduction loss is very low, for example: the 18V heavy-load output current is 7.5A, the output power is 135W, and the conduction loss of the Q1N-channel MOS tube is only: about 0.11W.
A resistor R6, a resistor R7, an NPN transistor Q4, a zener diode ZD1 and a capacitor C1 form a bias supply voltage circuit of the voltage regulation and standby control circuit 13, one end of the resistors R6 and R7 is electrically connected to the output end of the LED tube driving circuit 6, the other end of the resistor R6 is electrically connected to the negative end of the zener diode ZD1 and the base of the Q4 NPN transistor, the other end of the resistor R7 is electrically connected to the collector of the Q4 NPN transistor, the emitter of the Q4 NPN transistor is electrically connected to one end of the capacitor C1 and the other end of the resistor R3, the positive end of the zener diode ZD1 and the other end of the capacitor C1 are connected to the secondary side, the circuit takes power from the output end of the LED tube driving circuit 6 through the resistors R6 and R7, and generates a bias supply voltage Ve (Q4) = VZD1-0.7V =27V-0.7V =26.3V = 26V through the emitter of the NPN transistor Q4 in the circuit, and provides a bias supply voltage to the MOS channel Q6474 through the bias supply voltage channel of the zener diode z 6852.
FIG. 4 is a diagram of: PS _ ON is a standby control signal, and when PS _ ON is at a low level, the LED lamp driving circuit 6 enters a standby operation mode, and stops operating because Vcc supply voltage is not obtained, i.e., Vled = 0V. The ON/OFF is a switch control signal of the LED lamp tube driving circuit 6, and when the ON/OFF is a low level, the control chip in the LED lamp tube driving circuit 6 stops working.
V2 is the output terminal voltage of the second group of rectifying output filter circuit; VS (Q1) is the source terminal voltage of the Q1N channel MOS transistor, namely: an 18V output terminal voltage; IDS (Q1) is the current between the drain and the source of the Q1N channel MOS tube;
when the time T is between T0 and T1, the PS _ ON and ON/OFF signals are high level, the LED lamp tube driving circuit 6 outputs Vled voltage to the LED lamp tube 14 to work, the 12V output is heavy-load, the 18V output is light-load, the V2 is more than 18.7V, the Q1N channel MOS tube works in an amplifying region, the power loss P1 ON the Q1N channel MOS tube is not less than (V2-18V) IDS (Q1) = (19.8V-18.7V) × 0.1A =0.11W, and if the 18V output is 0.1A, the V2=19.8V;
when the PS _ ON and ON/OFF signals are at high level between T1 and T2, the LED lamp driving circuit 6 outputs Vled voltage to the LED lamp 14 to work, the 12V output is heavily loaded, and the 18V output load is heavy, at this time, 17.3V is not less than V21 is not less than 18.7V, the Q1N-channel MOS transistor works in a complete conduction region (also called variable resistance region), at this time, the power loss P2= IDS (Q1) IDS (Q1) IDS 1) rds ON (3535353575) =7.5A 3 a Ω =0.168W, and if IDS (Q1) 7.5A Q1N-channel MOS impedance rds ON (3 m Ω);
when the time T > T2, the PS _ ON and ON/OFF signals are low, the liquid crystal display enters the standby mode, and the LED tube driving circuit 6 stops outputting Vled voltage to the LED tube 14, that is: and Vled =0V, the 12V output is changed from heavy load to light load during standby, and the 18V output stops working because the Gate end of the Q1N-channel MOS tube can not obtain bias voltage from the R3 resistor, namely, the 18V output is cut off by the Q1 MOS tube during standby, so that the system is more energy-saving and power-saving during standby.
The invention only adopts one isolated DC-DC voltage reduction circuit 5 to output two groups of different direct currents of V1 and V2 through a transformer 7, such as: the voltage of V1 is 12V DC, and the voltage of V2 outputs 18V DC after passing through a voltage stabilization and standby control circuit 13, wherein the sampling feedback circuit 12 performs 100% feedback on the group of outputs of the output voltage V1, and the sampling feedback circuit 12 does not perform any sampling feedback on the output voltage of the output voltage V2, so as to ensure that the precision of the output voltage of V1 can be controlled within 5% at least to supply power to the circuits such as a back-end main circuit, a liquid crystal panel T-CON circuit and a USB.
Set up a steady voltage and standby control circuit 13 between the power supply input end of second group output rectification filter circuit 9 output and rear end open pluggable OPS-C equipment and AMP audio power amplifier circuit to ensure: the method comprises the steps of firstly, controlling the voltage precision of a power supply input end of 18V output to rear-end open pluggable OPS-C equipment and an AMP audio power amplifier circuit within 5 percent or even lower, and secondly, cutting off the 18V output in standby, wherein the product stops working due to cutting off the power supply voltage of the rear-end OPS-C equipment and the AMP audio power amplifier circuit in standby, so that the liquid crystal display product is more energy-saving and power-saving in standby state.
The invention makes technical innovation improvement on the prior art circuit architecture of fig. 1, solves the problem that the second group of output rectifying and filtering circuits in the prior art of fig. 1 output 18V direct current voltage with poor precision (only 18V +/-10%) and cannot meet the requirement of an OPS-C power supply upper limit of 19V, and one group of isolated DC-DC voltage reduction circuits simultaneously output two groups of 12V +/-5% and 18V +/-5% voltages, while the circuit architecture of fig. 2 needs to adopt two groups of isolated DC-DC voltage reduction circuits to respectively output two groups of 12V +/-5% and 18V +/-5% voltages, so that the novel switching power supply circuit is more excellent in BOM material cost compared with the prior power supply architecture circuit and can further improve the market competitiveness of products.
By adopting the technical scheme, when the LED lamp tube driving circuit works normally, the main substrate circuit outputs a PS _ ON signal and an ON/OFF signal as high-level signals respectively, so that the LED lamp tube driving circuit works normally. When the liquid crystal display product enters the standby mode, the main substrate circuit respectively outputs a PS _ ON signal and an ON/OFF signal which are low level signals, so that the LED lamp tube driving circuit stops working and the bias power supply circuit outputs zero voltage, namely when the liquid crystal display product enters the standby mode, the grid electrode of the MOS tube Q1 cannot obtain the bias voltage and the bias voltage is changed into a cut-OFF state from conduction between the drain electrode and the source electrode, namely: in the standby state, the second output voltage is cut off by the MOS transistor Q1 and cannot be provided to the back-end open pluggable OPS-C device and the AMP audio power amplifier circuit to operate, so that the second output voltage is in a more energy-saving and power-saving state.
It is to be understood that the embodiments described are only a few embodiments of the present application and not all embodiments. The embodiments and features of the embodiments in the present application may be combined with each other without conflict. The components of the embodiments of the present application, generally described and illustrated in the figures herein, can be arranged and designed in a wide variety of different configurations. Thus, the detailed description of the embodiments of the present application is not intended to limit the scope of the claimed application, but is merely representative of selected embodiments of the application. 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.

Claims (10)

1. High accuracy switching power supply circuit of two group's outputs based on single transformer, its characterized in that: the LED lamp tube driving circuit comprises a direct current source circuit, an isolation type DC-DC voltage reduction circuit, a transformer and an LED lamp tube driving circuit, wherein the direct current source circuit is connected with a wiring terminal of a primary side winding of the transformer through the isolation type DC-DC voltage reduction circuit;
the secondary side winding of the transformer is provided with two windings for outputting different direct current voltages, one winding voltage output end is connected with the first rectifying and filtering circuit and generates a first direct current after being rectified and filtered by the first rectifying and filtering circuit, the other winding voltage output end is connected with the second rectifying and filtering circuit and generates a second direct current after being rectified and filtered by the second rectifying and filtering circuit, the first direct current supplies power to the main substrate circuit, the T-CON circuit and the USB circuit of the liquid crystal panel, and the second direct current supplies power to the open type pluggable OPS-C equipment and the AMP audio power amplifier circuit through the voltage stabilizing and standby control circuit; the first direct current is connected to the input end of the sampling feedback circuit, and the output end of the sampling feedback circuit is connected to the isolated DC-DC voltage reduction circuit, so that the isolated DC-DC voltage reduction circuit and the transformer can regulate output electric energy;
the voltage stabilizing and standby control circuit comprises a bias power supply circuit and a voltage stabilizing circuit, wherein the bias power supply circuit provides a bias working voltage for the voltage stabilizing circuit through a resistor R3; the voltage stabilizing circuit comprises a MOS tube Q1, an operational amplifier OP and a transistor Q2, wherein the drain electrode of the MOS tube Q1 is connected with a second direct current, and the source electrode of the MOS tube Q1 is respectively connected with the power supply input end of the open pluggable OPS-C device and the power supply input end of the AMP audio power amplifier circuit; the grid of the MOS tube Q1 is respectively connected with the output end of the bias power supply circuit, the collector of the transistor Q2 and the Vcc power supply end of the operational amplifier OP, the base of the transistor Q2 is electrically connected with the output end of the operational amplifier OP, the positive input end of the operational amplifier OP is respectively connected with one end of the pull-down resistor R1 and one end of the pull-up resistor R2, the other end of the pull-up resistor R2 is electrically connected with the source of the MOS tube Q1, the negative input end of the operational amplifier OP is electrically connected with a reference voltage source Vref, and the emitter of the transistor Q2, the grounding end of the operational amplifier OP, the grounding end of the reference voltage source Vref and the other end of the pull-down R1 are connected with the secondary side ground.
2. The single-transformer based dual-output high-precision switching power supply circuit according to claim 1, wherein: the dc source circuit outputs a dc voltage of about 400V.
3. The single-transformer based dual-output high-precision switching power supply circuit according to claim 1, wherein: the bias power supply circuit comprises a transistor Q4 and a voltage regulator tube ZD1, wherein the collector of the transistor Q4 is electrically connected with one end of a resistor R7, the base of the transistor Q4 is electrically connected with one end of a resistor R6 and the cathode of the voltage regulator tube ZD1 respectively, the emitter of the transistor Q4 is electrically connected with one end of a capacitor C1 and one end of a resistor R3 respectively, the other end of the resistor R3 is connected with the grid of a Mos tube Q1, and the other ends of the resistor R6 and the resistor R7 are electrically connected with the output end of the LED lamp tube driving circuit.
4. The single-transformer based dual-output high-precision switching power supply circuit according to claim 3, wherein: MOS pipe Q1 can be selected as follows: the transistor Q2 is an NPN transistor, the value of the pull-down resistor R1 is 10K omega, the value of the pull-up resistor R2 is 64.8K omega, and the 27V voltage stabilizing diode is selected from ZD 1.
5. The single-transformer based dual-output high-precision switching power supply circuit according to claim 1, wherein: the secondary side winding of the transformer is also provided with a bias power supply winding, the bias power supply circuit comprises a MOS tube Q3, a transistor Q5 and a Vbias output rectifying and filtering circuit, the output end of the secondary side bias power supply winding of the transformer is electrically connected with the input end of the Vbias output rectifying and filtering circuit, the output end of the Vbias output rectifying and filtering circuit is electrically connected with one end of a resistor R3, the other end of the resistor R3 is electrically connected with one end of a resistor R4 and the emitter of a transistor Q5, the base of the transistor Q5 is electrically connected with the other end of the resistor R4 and one end of the resistor R5, the collector of the transistor Q5 is electrically connected with the grid of a MOS tube Q1, the other end of the resistor R5 is electrically connected with the drain of the MOS tube Q3, the grid of the MOS tube Q3 is electrically connected with a standby control signal PS _ ON output by the main substrate, and the source of the MOS tube Q3 is electrically connected with the secondary side ground.
6. The single-transformer based dual-output high-precision switching power supply circuit according to claim 5, wherein: the MOS transistor Q3 is an N-channel MOS transistor, and the transistor Q5 is a PNP transistor.
7. The single-transformer based dual-output high-precision switching power supply circuit according to claim 1, wherein: the commercial alternating current is 110V/60HZ or 220V/50HZ power frequency alternating current.
8. The single-transformer based dual-output high-precision switching power supply circuit according to claim 1, wherein: the direct current source circuit comprises an EMI filter circuit, a bridge rectifier circuit, a PFC booster circuit and a power frequency large-capacitance filter circuit which are sequentially and electrically connected, commercial alternating current is connected with the EMI filter circuit and is subjected to EMI filtering by the EMI filter circuit, full-wave rectification is carried out by the bridge rectifier circuit to form unidirectional pulsating direct current voltage, boosting is carried out by the PFC booster circuit, and filtering is carried out by the power frequency large-capacitance filter circuit to generate direct current voltage of about 400V.
9. The single-transformer based dual-output high-precision switching power supply circuit according to claim 1, wherein: the operational amplifier OP, the transistor Q2 and the reference voltage source Vref adopt integrated devices with corresponding functions, and the integrator is TL431 or AZ 431.
10. The single-transformer based dual-output high-precision switching power supply circuit according to claim 1, wherein: the main substrate circuit respectively outputs a standby control signal PS _ ON and an LED lamp tube switching signal ON/OFF and an LED lamp tube dimming signal DIM, wherein the PS _ ON signal is used for controlling the liquid crystal display product to enter a normal working mode or a standby working mode, the ON/OFF signal is used for controlling whether the LED lamp tube driving circuit works, and the DIM signal is used for controlling the brightness and darkness of a liquid crystal display picture.
CN202210223770.7A 2022-03-09 2022-03-09 High-precision switching power supply circuit based on double-group output of single transformer Pending CN114825939A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202210223770.7A CN114825939A (en) 2022-03-09 2022-03-09 High-precision switching power supply circuit based on double-group output of single transformer

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202210223770.7A CN114825939A (en) 2022-03-09 2022-03-09 High-precision switching power supply circuit based on double-group output of single transformer

Publications (1)

Publication Number Publication Date
CN114825939A true CN114825939A (en) 2022-07-29

Family

ID=82528825

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202210223770.7A Pending CN114825939A (en) 2022-03-09 2022-03-09 High-precision switching power supply circuit based on double-group output of single transformer

Country Status (1)

Country Link
CN (1) CN114825939A (en)

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1262551A (en) * 2000-01-13 2000-08-09 深圳市华为电气股份有限公司 Dual-output power supply with high voltage stability and high precision
US20030142513A1 (en) * 2002-01-31 2003-07-31 Patrizio Vinciarelli Factorized power architecture with point of load sine amplitude converters
CN101668369A (en) * 2009-10-01 2010-03-10 英飞特电子（杭州）有限公司 High-efficiency constant-current LED driver
US20100109561A1 (en) * 2008-10-30 2010-05-06 Wen-Sheng Chen Power supply apparatus
CN105960070A (en) * 2016-07-13 2016-09-21 福建捷联电子有限公司 Single-feedback direct-push type DC light-dimming LED tube driving circuit

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1262551A (en) * 2000-01-13 2000-08-09 深圳市华为电气股份有限公司 Dual-output power supply with high voltage stability and high precision
US20030142513A1 (en) * 2002-01-31 2003-07-31 Patrizio Vinciarelli Factorized power architecture with point of load sine amplitude converters
US20100109561A1 (en) * 2008-10-30 2010-05-06 Wen-Sheng Chen Power supply apparatus
CN101668369A (en) * 2009-10-01 2010-03-10 英飞特电子（杭州）有限公司 High-efficiency constant-current LED driver
CN105960070A (en) * 2016-07-13 2016-09-21 福建捷联电子有限公司 Single-feedback direct-push type DC light-dimming LED tube driving circuit

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
廖吾清: "新型LED背光源液晶彩色显示器电源与背光电路", 科技传播, no. 20, 30 June 2010 (2010-06-30), pages 47 - 48 *

Similar Documents

Publication Publication Date Title
EP3471512B1 (en) Switching power supply and television
CN102243850B (en) Backlight source driving circuit, driving method thereof as well as liquid crystal television
CN102065600B (en) LED dimming driving system
US8824172B2 (en) Apparatus and method for standby power reduction of a flyback power converter
US6297976B1 (en) Thin, cascade-connected direct current source circuit
US20210210008A1 (en) Oled drive power supply and oled television
US10015434B2 (en) Switched-mode power supply for outputting a steady voltage and current and television including the same
DE102012104072A1 (en) converter
CN105960070A (en) Single-feedback direct-push type DC light-dimming LED tube driving circuit
AU2016310330A1 (en) Switched-mode power supply and associated television
US20230419916A1 (en) Display apparatus and display control method
CN109362157B (en) Constant current control circuit and television
US11825577B2 (en) Display apparatus and step power circuit
CN104377971A (en) Flyback direct-drive LED power circuit on basis of voltage feedback and television set
CN205912292U (en) Straight pushing -type DC of single feedback LED fluorescent tube drive circuit that adjusts luminance
KR102215378B1 (en) Protection circuit and LED driving circuit
CN105307305A (en) LED power supply control device and TV set
US20230387793A1 (en) Control circuit, power factor correction circuit, and electric appliance
CN211087888U (en) Backlight driving circuit and electronic equipment
CN109862292B (en) Constant current control circuit and television
CN114825939A (en) High-precision switching power supply circuit based on double-group output of single transformer
CN216122216U (en) Power supply circuit, switching power supply and display device
CN106455209B (en) Dimming interface circuit and AC driving circuit
CN220570463U (en) Load adjustable circuit, power supply circuit, circuit board and electronic equipment
CN217388544U (en) Power supply circuit and electronic equipment

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination