CN108494255B - Program-controlled LLC series resonant converter and control method thereof - Google Patents

Program-controlled LLC series resonant converter and control method thereof Download PDF

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CN108494255B
CN108494255B CN201810199244.5A CN201810199244A CN108494255B CN 108494255 B CN108494255 B CN 108494255B CN 201810199244 A CN201810199244 A CN 201810199244A CN 108494255 B CN108494255 B CN 108494255B
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llc
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CN108494255A (en
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马凯宁
苏亮
尹馥玫
王立金
吴发龙
张志国
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Beijing Sifang Automation Co Ltd
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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
    • 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
    • H02M3/33569—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 having several active switching elements
    • 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
    • H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
    • H02M1/088—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters for the simultaneous control of series or parallel connected semiconductor devices
    • H02M1/092—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters for the simultaneous control of series or parallel connected semiconductor devices the control signals being transmitted optically
    • 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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Abstract

The invention provides a program control LLC series resonance converter and a control method thereof, which is characterized in that: the program-controlled LLC series resonant converter is composed of a primary side bridge circuit, a primary side auxiliary power supply circuit, an LLC resonant drive circuit, a secondary side output rectifying circuit, a secondary side output adjusting circuit, a single-chip microcomputer control circuit, a single-chip microcomputer output PWM (pulse width modulation) conversion circuit and a power supply feedback circuit. Through the combined design of the single chip microcomputer and the LLC series resonant converter, the output voltage control of the power supply under different load conditions is completed, the communication with an upper computer is solved, and the function of controlling the converter by the upper computer is completed.

Description

Program-controlled LLC series resonant converter and control method thereof
Technical Field
The invention belongs to the technical field of switching power supplies, and particularly relates to a series resonance switching power supply and a control method for wide-range output of the series resonance switching power supply.
Background
With the rapid development of electronic and electrical technologies, high power and high efficiency are becoming development trends. In recent years, with the development of semiconductor device manufacturing technology, the reduction of on-resistance, parasitic capacitance and reverse recovery time of the switching tube creates conditions for the realization of the resonant converter. The LLC resonant half-bridge converter is one type of converter, keeps the conduction duty ratio of switching tubes of an upper bridge arm and a lower bridge arm unchanged, and adjusts output voltage by adjusting switching frequency to realize soft switching conversion. Compared with other soft switching technologies, the LLC resonant half-bridge converter not only has the zero-voltage switching-on characteristic of a primary side switching tube, but also has better power-down maintaining time characteristic, can realize the zero-current conduction and low voltage resistance requirements of a secondary side rectifier diode, can reduce the loss and improve the power supply efficiency. The LLC resonance half-bridge converter forms a half-bridge circuit by two power switching tubes and is used for driving an LLC resonance network of a later stage. The resonance network is composed of a series resonance capacitor Cr, a series resonance inductor Lr and a transformer excitation inductor Lm, wherein Lr is an independent inductor. Two powersThe switching tube half-bridge is driven by a preceding controller, and the rectifying circuit is connected to an output capacitor C by a pair0Two rectifier diodes, the cathodes of the two rectifier diodes are connected with C0Respectively connected to the secondary winding n of the transformers1Positive homonym terminal, ns2The reverse homonymous end of (1); n iss1Reverse homonym and ns2Are connected together and simultaneously to the output ground.
Two resonance frequencies f of the LLC resonant networkrAnd fmRespectively as follows:
Figure GDA0002516252630000011
Figure GDA0002516252630000012
when the power supply works, the two power switching tubes are conducted in a staggered mode, the power supply works at a constant duty ratio (the duty ratio is less than 50%), and the controller realizes output voltage stabilization by adjusting the driving working frequency. In general, to improve efficiency, the LLC resonant half-bridge converter implements zero-voltage switching of the primary half-bridge circuit power switching transistor by appropriate parameter and frequency control, while enabling zero-current switching of the secondary rectifier diode. To achieve the above object, the controller can operate in the following three frequency bands:
(1)fSW＝fr
(2)fsw＞fr
(3)fr＞fsw＞fm
when the operating frequency fswGreater than the resonance frequency frIn this case, the magnetizing inductance Lm does not participate in resonance as a load, and the operation mode at this time is similar to that of a general Series Resonant Converter (SRC). When the LLC series resonant converter works in no load or light load, the working frequency is increased or the resonant frequency is reduced, so that the voltage gain is reduced, and when f issw＞frWhen the current is in a low-load state, a small change in gain can cause a large change in efficiency, so that the output voltage of the LLC series resonant converter is difficult to output under no-load or light-load conditionsAnd (4) stabilizing. When the circuit works in a low-voltage light-load state, a gain characteristic curve tends to be flat, if the voltage is stabilized, a very high working frequency is needed, but the very high working frequency can bring a series of problems, such as difficulty in optimizing a magnetic device, increase of switching loss, reduction of reliability and the like; further, when the load is near idle, the range of the output voltage increases as the frequency or duty ratio increases, and the feedback loop control cannot be performed.
To achieve the highest efficiency, the LLC resonant half-bridge converter is usually controlled to operate at a frequency greater than f at nominal input voltage, full load conditionrFrequency point, such that f is entered when the load changes dynamically or the voltage is interrupted for a short timer＞fsw＞fmA work area.
The following methods are commonly used in the industry to overcome the above problems: the first method is that under the no-load or light-load state, a small dummy load is added to realize the output voltage regulation; the second method is that under the no-load or light-load state, the width adjusting control is added, namely the duty ratio of the switching tube is adjusted; the third method is that under the no-load or light-load state, the mixed control of width modulation and frequency modulation is added, namely the duty ratio and the working frequency of the switching tube are adjusted simultaneously. Although the above three methods can overcome the above problems, there are the following problems: the first method can realize the stability in the no-load or light-load state, but sacrifices the conversion efficiency of the converter in the no-load or light-load state; although the second method greatly improves the stability in the no-load or light-load state and realizes the voltage stabilization in the no-load or light-load state, due to the nonlinearity of a gain characteristic curve during width modulation, the situation that the output voltage is rather reduced along with the increase of the duty ratio can occur, so that the loop design is difficult, the stability and the non-oscillation of a feedback loop in the width modulation range are difficult to ensure all the time, and in addition, when the converter works near a switching load point, two control strategies can be switched back and forth, so that the loop is unstable, and the integral output characteristic of the converter is influenced; the third method is to add frequency modulation control on the basis of the second method, so as to ensure the linear relation of the output gain characteristic curve and solve the problem of difficult loop design to a certain extent. However, in practical engineering, for a converter with a wide output range, it is difficult to ensure that the output gain characteristic curve still presents a linear relationship with the change of the duty ratio when the output limit is low voltage, so that the method also has practical engineering problems that the loop is difficult to control, the frequency modulation and width modulation curve is difficult to optimize, and the like. In addition, when the converter works near a switching load point, two control strategies are switched back and forth, so that a loop is unstable, and the overall output characteristic of the converter is influenced.
The problems and defects of the converter working under low-voltage light load or no load are illustrated by taking half-bridge LLC series resonance as an example, and the same problems exist in full-bridge series resonance. In theory, all series resonant circuits using frequency modulation control suffer from the above problems.
Disclosure of Invention
The invention aims to provide a program-controlled LLC series resonant converter and a control method thereof, which complete the output voltage control of a power supply under different load conditions through the combined design of a single chip microcomputer and the LLC series resonant converter, realize the communication with an upper computer and complete the function of the upper computer for controlling the converter.
In order to achieve the purpose, the invention discloses a control method of an LLC series resonant converter, which is summarized as that the stable output of the voltage and the current of the LLC series resonant converter can be effectively controlled according to the output voltage through a singlechip control circuit, a singlechip output PWM conversion circuit and a power supply feedback circuit. The specific implementation steps are as follows:
firstly, an external input power supply is filtered and rectified by a primary side bridge circuit to obtain a direct current voltage;
secondly, the primary side auxiliary power supply circuit isolates the direct-current voltage and outputs a plurality of paths of voltages for the LLC resonance drive circuit, the secondary side output rectification circuit, the secondary side output adjustment circuit, the single chip microcomputer control circuit, the single chip microcomputer output PWM conversion circuit and the power supply feedback circuit;
and thirdly, outputting two continuous voltage pulses and current pulses with fixed frequency and adjustable width by the singlechip control circuit according to the voltage and current values output by the LLC series resonant converter. Converting the voltage pulse and the current pulse into voltage and current signals through the single chip microcomputer output PWM conversion circuit, sampling the secondary side output voltage adjustment circuit and the secondary side output current adjustment circuit to obtain the voltage and the current of a secondary side output port, and comparing the converted voltage and current signals with the port voltage and the port current;
and fourthly, controlling the grid electrode of the MOSFET switching tube in the secondary side output control circuit in the secondary side output adjusting circuit according to the comparison result, so that the MOSFET switching tube works in an amplification area. The dynamic intermittent control of the output voltage and current is completed, and the output voltage and current values meeting the requirements can be obtained after subsequent rectification and filtration;
and fifthly, the power supply feedback circuit compares the driving voltage value of the grid electrode of the MOSFET switching tube in the secondary side output control circuit in the secondary side output adjusting circuit with the voltage value of the source electrode of the MOSFET switching tube to judge whether the voltage state in the secondary side rectifying circuit is overvoltage or undervoltage, so that the frequency of the output upper and lower push tube signals in the LLC resonant driving circuit is adjusted, and the switching speeds of the upper and lower bridge arm switching tubes in the LLC resonant circuit are driven through the upper half-bridge switching tube totem pole circuit and the lower half-bridge switching tube totem pole circuit.
The invention also provides a program-controlled LLC series resonant converter using the control method, which is characterized in that: the program-controlled LLC series resonant converter is composed of a primary side bridge circuit, a primary side auxiliary power supply circuit, an LLC resonant drive circuit, a secondary side output rectifying circuit, a secondary side output adjusting circuit, a single-chip microcomputer control circuit, a single-chip microcomputer output PWM (pulse width modulation) conversion circuit and a power supply feedback circuit.
The invention further comprises the following preferred embodiments:
the primary side bridge circuit is mainly characterized in that: the circuit comprises a fuse, an X safety capacitor, a Y safety capacitor, a rectifier bridge and an energy storage capacitor. And after the external input power supply is filtered and rectified by the primary side bridge circuit, a direct current voltage is obtained to be used by the primary side auxiliary power circuit and the LLC resonant circuit.
The primary side auxiliary power supply circuit of the invention is mainly characterized in that: the PWM power supply consists of a PWM chip circuit, an auxiliary power supply transformer and an output rectifying circuit. After the direct-current voltage output by the primary side bridge circuit is isolated, a plurality of paths of voltage output are output and are supplied to the LLC resonant circuit, the LLC resonant driving circuit, the secondary side output adjusting circuit, the single chip microcomputer control circuit, the single chip microcomputer output PWM conversion circuit and the power supply feedback circuit.
The LLC resonant circuit is mainly characterized in that: the high-voltage power supply comprises an upper bridge arm and a lower bridge arm which are formed by two switching tubes, a high-voltage resonant capacitor, a resonant inductor and an LLC transformer. The upper and lower switch tubes are sequentially switched on and off under the drive of the LLC resonant drive circuit. And the resonant cavity is resonated with a resonant inductor and an LLC transformer to finish the zero crossing point output of the primary voltage of the transformer.
The LLC resonance driving circuit is mainly characterized in that: the half-bridge circuit consists of a self-vibration half-bridge driver, a switching tube totem-pole circuit on the half-bridge and a switching tube totem-pole circuit under the half-bridge. The resonance control end of the self-vibrating half-bridge driver outputs variable-frequency up-down push tube signals under the control of the power supply feedback circuit, and the control of the upper and lower bridge arm switching tubes in the LLC resonance circuit is completed through the upper half-bridge switching tube totem pole circuit and the lower half-bridge switching tube totem pole circuit.
The secondary side output rectifying circuit is mainly characterized in that: the common-mode inductor is composed of a common-mode inductor, a rectifier diode and a filter capacitor.
The invention is characterized in that the secondary side output adjusting circuit is characterized in that: the secondary side output voltage regulating circuit is composed of a secondary side output voltage regulating circuit, a secondary side output current regulating circuit and a secondary side output control circuit.
The secondary side output voltage adjusting circuit is mainly characterized in that: the device consists of a secondary side output voltage measuring resistor and a voltage acquisition filter circuit. And the voltage acquired by the secondary side output voltage measuring resistor is subjected to voltage division and filtering and then is sent to a secondary side output control circuit.
The secondary side output current adjusting circuit is mainly characterized in that: the device consists of a secondary side output current measuring resistor, a current collecting filter circuit and an operational amplifier which are connected in series in a main loop. And the current acquired by the secondary side output current measuring resistor is filtered and amplified and then is sent to the secondary side output control circuit.
The secondary side output control circuit is mainly characterized in that: the comparator circuit is composed of a MOSFET switching tube and an LF353, wherein the MOSFET switching tube is connected in series behind the secondary side output rectifying circuit. And the LF353 compares the output voltage and the output current value measured by the secondary side output voltage adjusting circuit and the secondary side output current adjusting circuit with the voltage and current calibration values output by the single-chip microcomputer PWM conversion circuit, and quickly adjusts the working state of the MOSFET switch tube in a linear working area according to the comparison result for adjusting the output calibration voltage and current values.
The singlechip control circuit is mainly characterized in that: the device consists of a PCB, a singlechip peripheral circuit, a control interface circuit and a communication interface circuit. And the communication work with the notebook computer is completed through the USB interface. And executing a command issued by the notebook computer, controlling the output of the LLC resonant converter, and uploading the real-time state output by the LLC resonant converter to the notebook computer.
The output PWM conversion circuit of the singlechip is mainly characterized in that: the device consists of a bus driving controller, an analog switch chip and an integral amplifying circuit. The main function is to convert the voltage and current frequency signals output by the singlechip control circuit into analog voltage signals through an analog switch chip and an integral amplifying circuit, compare the analog voltage signals with the voltage and current signals in the secondary side output control circuit, and control the numerical values of the output current and voltage of the power supply through the secondary side output adjusting circuit.
The power supply feedback circuit is mainly characterized in that: the circuit mainly comprises a comparator circuit formed by LF353, a linear optocoupler and a bidirectional circuit formed by diodes. The voltage signal after the MOSFET switch tube source electrode and the MOSFET switch tube grid-deletion control voltage interval value of the secondary side output control circuit are amplified is compared, and the comparison result is used for explaining the voltage condition of the point behind the secondary side output rectification circuit and in front of the MOSFET switch tube source electrode of the secondary side output control circuit, namely reflecting the relation between the calibrated voltage current in the PWM conversion circuit output by the singlechip and the voltage current behind the secondary side output rectification circuit of the front stage. The conduction degree of the linear optocoupler is determined by a result obtained by a comparator circuit formed by the LF353, and a bidirectional circuit formed by the diode and a self-oscillation type half-bridge driver in the LLC resonance driving circuit realize frequency adjustment to complete feedback control.
The invention has the following beneficial effects:
(1) the problem of fixed output calibration value and difficult control of voltage in the output process in traditional switching power supply design is solved.
(2) And the control of increasing, decreasing, keeping time and the like of the output voltage of the power supply in advance is realized.
(3) And the remote control of the switching power supply is realized.
Drawings
FIG. 1 is a block diagram of a programmable LLC series resonant converter of the invention; FIG. 2 is a block diagram of a primary side auxiliary power supply circuit;
FIG. 3 is a block diagram of an LLC resonant drive circuit;
FIG. 4 is a block diagram of a control circuit of the single chip microcomputer;
FIG. 5 is a block diagram of a single-chip output PWM conversion circuit;
FIG. 6 is a block diagram of a secondary side output adjustment circuit;
fig. 7 is a block diagram of a power supply feedback circuit.
Detailed Description
The present invention will be described in further detail with reference to the following drawings and specific examples. Example 1: the embodiment is a program control LLC series resonance converter which combines the control technology of a single chip microcomputer on the basis of an LLC series resonance switching power supply. The basic indexes are as follows: input DC/AC220V, output DC 0-300V.
As shown in fig. 1, the programmable LLC series resonant converter mainly comprises a primary side bridge circuit, a primary side auxiliary power supply circuit, an LLC resonant drive circuit, an LLC resonant circuit, a secondary side output rectification circuit, a secondary side output regulation circuit, a single-chip microcomputer control circuit, a single-chip microcomputer output PWM conversion circuit, and a power supply feedback circuit. The primary side bridge circuit introduces an external output voltage through a terminal J7, an X capacitor CX1 is placed between two voltage input leads, two input line pairs are safely connected with Y capacitors CY1 and CY2 and are connected in series with a common mode inductor L5 to a rectifier bridge BG1, and two energy storage capacitors CC1 and CC2 are placed behind the rectifier bridge. The LLC resonant circuit consists of two MOSFET switching tubes 47N06C3, a resonant inductor L3(50.7uh), a resonant capacitor C9 and a switching transformer T1(26 (64, 64)) which are Q1 and Q4. The drain of the Q1 is connected with the anode of the CC2 in the primary side bridge circuit, and the source is connected with the drain of the Q4 and is also connected with the resonant inductor L3. The resonant inductor L3 is connected in series with the resonant capacitor C9 and then connected to the input end of the primary coil of the switch transformer T1. The output end of the primary coil in the T1 is connected with the source of Q4 and with the negative end of CC2, thus forming a closed loop of resonance. The secondary side output rectifying circuit consists of a common anode fast recovery rectifying diode D4, an output filter capacitor C4, an output post-stage common mode inductor L1(744_825_510) and an output filter capacitor C1.
As shown in fig. 2, the primary side auxiliary power circuit is composed of a PWM chip U2(THX208) and a transformer T2(115 (16, 15, 14, 18)) to form a low power switching power circuit of a main topology. The output of the transformer is rectified and stabilized by the LDO, and then the power supplies of +/-8V, 5V, 10V and 9V can be provided. Wherein, the output voltage loop is increased by +/-5V after the +/-8V is stabilized by the LDO chip. And +/-8V and +/-5V provide power for the secondary side output rectifying circuit, the secondary side output adjusting circuit, the power supply feedback circuit and the single chip microcomputer output PWM conversion circuit. 5V provides power supply for the singlechip control circuit. 9V is the working power supply of the PWM chip U2(THX 208). And 10V provides power supply for the LLC resonant drive circuit.
As shown in fig. 3, the LLC resonant driving circuit consists of a self-oscillating half-bridge driving chip U8(IR21531S) and two groups of totem-pole driving circuits at the output end. Wherein the IR21521S frequency resonant circuit C28, R34 sets the initial resonant frequency at 20 KHz. And R35 is connected in parallel with the C28 through a power supply feedback circuit.
As shown in FIG. 4, the MCU control circuit uses MK10DX256LQ10 as the main control chip, and the periphery is configured with EEPROM _ AT24C512, reset chip TPS3705, 50MHZ crystal oscillator and power supply chip SPX 1117-3.3. A CAN network transceiver element SN65HVD232DR and a USB external interface circuit with FT232AM as a main topology are configured for the external communication circuit. And is also provided with a 3.3V to 5V multi-channel power supply control signal consisting of an 8-bit bus transceiver SN74LV245ATPWR and a PWM signal of a calibration voltage and a calibration current.
As shown in fig. 5, the single chip output PWM conversion circuit is composed of an analog switch chip U14, a chip U15(MC14051B), and a chip U16(OPA4277) of 4 operational amplifiers. The output port of the singlechip is connected with a connection control 11 pin (A) of U14 and U15(MC14051B), a reference source U13-TL431 is connected with 13 pins (X0) of U14 and U15, the output 2.5V voltage is output to two groups of integrating circuits consisting of U16 through the pins U14 and U15, the 2.5V PWM signal is converted into a voltage calibration value voltage signal and a current calibration value current signal which are respectively output in a calibration mode, and the signals are amplified.
As shown in fig. 6, the front-end sampling voltage signal is connected to U21 to form a secondary output voltage regulator circuit. The sampled current signal is transmitted to an operational amplifier U20-OP0, amplified and then sent to U21 to form a secondary output current adjusting circuit. And the U21 in the secondary side output control circuit compares the sampling current signal and the sampling voltage signal with a calibration current signal and a calibration voltage signal provided by the single chip microcomputer output PWM conversion circuit. U21-LF353 are double-operational-amplifier structures, each of which is connected in a comparator topology mode, and the output comparison results of the 1 st pin and the 2 nd pin are connected to R60 and then connected to the grid of Q3 in the power supply feedback circuit of FIG. 7. In order to protect the grid of the Q3, a voltage division circuit formed by connecting R21, D28, D27 and R20 in series is connected between +/-8V in parallel.
As shown in fig. 7, the power supply feedback circuit mainly comprises a dual operational amplifier chip U7(LF353) and a bidirectional circuit formed by diodes in the stage of a linear optocoupler U9(EL 817). The 5 th pin of the operational amplifier at one side of the double operational amplifier chip U7(LF353) is connected with the source electrode of a switching tube MOSFET (metal-oxide-semiconductor field effect transistor) Q3 through R19 and D11, and is connected with GND through D11 and R18, the topological mode is a following amplification mode, the output voltage of the secondary side rectifying circuit is collected, amplified, and then output to the 2 nd pin at the other side of the double operational amplifier chip U7(LF353) through the 7 th pin. And a source grid alternating current signal of a MOSFET Q3 of the switching tube is superposed on a reference voltage signal obtained by connecting two diodes in series and is connected to the 3 rd pin. The 2 nd pin signal is compared to the 3 rd pin signal. The output result is connected with the primary side of a linear optocoupler U9(EL817), and the other side of the linear optocoupler U9(EL817) is connected with a bidirectional circuit formed by diodes D14, D15, D16 and D17 in the LLC resonant driving circuit and is connected with the LLC resonant driving circuit.
The control method of the program-controlled LLC series resonant converter in the embodiment comprises the following steps:
firstly, an external power supply AC220V is connected, a primary side bridge circuit starts to work, and AC220V obtains DC voltage of about 300V after filtering and rectifying.
And secondly, the primary side auxiliary power supply circuit starts to work and provides isolated power supply outputs of +/-8V, 5V, 10V, 9V and the like, wherein +/-8V is regulated by the LDO chip, and an output voltage loop is increased by +/-5V. The +/-8V and +/-5V provide power for the secondary side output rectifying circuit, the secondary side output adjusting circuit, the power supply feedback circuit and the single chip microcomputer output PWM conversion circuit, the 5V provides power for the single chip microcomputer control circuit, the 9V provides power for the PWM chip THX208 working power supply, and the 10V provides power for the LLC resonant driving circuit.
And thirdly, when the single chip microcomputer control circuit obtains the working voltage and finishes electrifying initialization configuration, waiting for an output command issued by an external communication port (a USB interface or a CAN network interface). And after an external command is obtained, a voltage PWM value and a current PWM value of corresponding values prestored in the EEPROM _ AT24C512 are called according to the required output voltage and current values and are output. The two PWM values are sent to the control pins of two analog switch chips U14 and U15(MC 14051B). U14 is the nominal voltage output and U15 is the nominal current output. The voltage PWM signal and the current PWM signal respectively control the control pins of the analog switch chips, and the 2.5V voltage generated by the TL431 is subjected to voltage chopping processing. Two paths of 2.5V PWM signals pass through respective integrating circuits and amplifying circuits to form two continuous calibration voltage signals.
And fourthly, comparing the two calibration voltage values with the voltage and the current measured at the secondary side output end and the calibration voltage and the calibration current, and controlling the grid electrode of the MOSFET switching tube Q3 by the control voltage obtained after comparison. Meanwhile, the control voltage is superposed with 2V voltage and compared with the voltage signal amplified by the source electrode of the MOSFET switching tube Q3.
And fifthly, controlling the voltage to be superposed with a comparison result obtained by the 2V voltage and the voltage signal amplified by the source electrode of the MOSFET switching tube Q3. The value of a resonant resistor R62 on a self-oscillation type half-bridge driving chip IR21531S is adjusted through a bidirectional circuit formed by diodes through a linear optical coupler U9, and a feedback closed loop is completed through dynamic adjustment.
The above is only one embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the invention, and these modifications and variations should also be regarded as the protection scope of the present invention.

Claims (14)

1. A control method of a program-controlled LLC series resonant converter is characterized by comprising the following steps:
firstly, an external input power supply is filtered and rectified by a primary side bridge circuit to obtain a direct current voltage;
secondly, the primary side auxiliary power supply circuit isolates the direct-current voltage and outputs a plurality of paths of voltages for the LLC resonant circuit, the LLC resonant driving circuit, the secondary side output rectifying circuit, the secondary side output adjusting circuit, the single chip microcomputer control circuit, the single chip microcomputer output PWM conversion circuit and the power supply feedback circuit;
thirdly, the singlechip control circuit outputs two continuous voltage pulses and current pulses with fixed frequency and adjustable width according to the voltage and current values output by the LLC series resonant converter, the voltage pulses and the current pulses are converted into voltage and current signals through the singlechip output PWM conversion circuit, the secondary side output adjustment circuit samples and obtains the voltage and the current of a secondary side output port, and the converted voltage and current signals are compared with the port voltage and the port current;
fourthly, controlling the grid electrode of an MOSFET switching tube in the secondary side output adjusting circuit according to the comparison result, enabling the MOSFET switching tube to work in an amplification area, completing dynamic intermittent control on output voltage and current, and obtaining the output voltage and current values meeting the requirements after subsequent rectification and filtering;
and fifthly, comparing a driving voltage value of a grid electrode of a MOSFET (metal oxide semiconductor field effect transistor) switching tube in the secondary side output regulating circuit with a voltage value of a source electrode of the MOSFET switching tube by a power supply feedback circuit to judge whether the voltage state in the secondary side output rectifying circuit is overvoltage or undervoltage, further regulating the frequency of an output upper and lower push tube signal in the LLC resonant driving circuit, and regulating the switching speed of driving upper and lower bridge arm switching tubes in the LLC resonant circuit through a half-bridge upper switching tube totem pole circuit and a half-bridge lower switching tube totem pole circuit.
2. A programmed LLC series resonant converter using the control method of claim 1, characterized in that:
the device comprises a primary side bridge circuit, a primary side auxiliary power circuit, an LLC resonance driving circuit, a secondary side output rectifying circuit, a secondary side output adjusting circuit, a single chip microcomputer control circuit, a single chip microcomputer output PWM (pulse width modulation) conversion circuit and a power supply feedback circuit.
3. The programmable LLC series resonant converter of claim 2, wherein:
the primary side bridge circuit is composed of a fuse, an X safety capacitor, a Y safety capacitor, a rectifier bridge and an energy storage capacitor, and the primary side bridge circuit is used for filtering and rectifying an external input power supply through the primary side bridge circuit to obtain a direct current voltage for the primary side auxiliary power circuit and the LLC resonant circuit.
4. The programmable LLC series resonant converter of claim 2, wherein:
the primary side auxiliary power supply circuit consists of a PWM chip circuit, an auxiliary power supply transformer and an output rectifying circuit, and is used for isolating the voltage after primary side bridge type external filtering rectification and outputting a plurality of paths of voltage output for the LLC resonant circuit, the LLC resonant circuit driving circuit, the secondary side output rectifying circuit, the secondary side output adjusting circuit, the single chip microcomputer control circuit, the single chip microcomputer output PWM conversion circuit and the power supply feedback circuit.
5. The programmable LLC series resonant converter of claim 2, wherein:
the LLC resonant circuit consists of an upper bridge arm, a lower bridge arm, a high-voltage resonant capacitor, a resonant inductor and an LLC transformer, wherein the upper bridge arm and the lower bridge arm are formed by two switching tubes, the upper switching tube and the lower switching tube are sequentially switched on and off under the drive of the LLC resonant driving circuit and are resonant with the resonant cavity formed by the high-voltage resonant capacitor, the resonant inductor and the LLC transformer, and the zero-crossing-point output of the primary voltage of the transformer is.
6. The programmable LLC series resonant converter of claim 2, wherein:
the LLC resonance driving circuit consists of a self-vibration type half-bridge driver, a totem pole circuit of a switching tube on the half-bridge and a totem pole circuit of a switching tube under the half-bridge, wherein a resonance control end of the self-vibration type half-bridge driver outputs a variable-frequency up-down push tube signal under the control of a power supply feedback circuit, and the control of the switching tubes of an upper bridge arm and a lower bridge arm in the LLC resonance circuit is completed through the totem pole circuit of the switching tube on the half-bridge and the totem pole circuit of the switching tube under the half-bridge.
7. The programmable LLC series resonant converter of claim 2, wherein:
the secondary side output rectifying circuit consists of a common mode inductor, a rectifying diode and a filter capacitor.
8. The programmable LLC series resonant converter of claim 2, wherein:
the secondary side output adjusting circuit consists of a secondary side output voltage adjusting circuit, a secondary side output current adjusting circuit and a secondary side output control circuit.
9. The programmable LLC series resonant converter of claim 8, wherein:
the secondary side output voltage adjusting circuit consists of a secondary side output voltage measuring resistor and a voltage acquisition filter circuit, and the voltage acquired by the secondary side output voltage measuring resistor is transmitted to the secondary side output control circuit after voltage division filtering.
10. The programmable LLC series resonant converter of claim 8, wherein:
the secondary side output current adjusting circuit consists of a secondary side output current measuring resistor, a current collecting filter circuit and an operational amplifier which are connected in series in the main loop, and the current collected by the secondary side output current measuring resistor is filtered and amplified and then is sent to the secondary side output control circuit.
11. The programmable LLC series resonant converter of claim 8, wherein:
the secondary side output control circuit is composed of a MOSFET switch tube and a comparator circuit, wherein the MOSFET switch tube is connected in series behind the secondary side output rectifying circuit, the comparator circuit is composed of the LF353, the LF353 compares the measured values of the output voltage and the current measured by the secondary side output voltage detection circuit and the secondary side output current detection circuit with the calibrated values of the voltage and the current output by the single chip microcomputer output PWM conversion circuit, and the working state of the MOSFET switch tube in a linear working area is quickly adjusted according to the comparison result for adjusting the output calibrated voltage and the current value.
12. The programmable LLC series resonant converter of claim 2, wherein:
the single chip microcomputer control circuit consists of a PCB, a single chip microcomputer peripheral circuit, a control interface circuit and a communication interface circuit, and is communicated with the notebook computer through a USB interface, executes a command issued by the notebook computer, controls the output of the LLC resonant converter, and uploads the real-time state of the output of the LLC resonant converter to the notebook computer.
13. The programmable LLC series resonant converter of claim 8, wherein:
the single chip microcomputer output PWM conversion circuit is composed of a bus drive controller, an analog switch chip and an integral amplifying circuit, and has the main functions that voltage and current frequency signals output by the single chip microcomputer control circuit are converted into analog voltage signals through the analog switch chip and the integral amplifying circuit and are compared with voltage and current signals in the secondary side output control circuit, and the values of the power supply output current and voltage are controlled through the secondary side output adjusting circuit.
14. The programmable LLC series resonant converter of claim 8, wherein:
the power supply feedback circuit mainly comprises a comparator circuit, a linear optocoupler and a bidirectional circuit, wherein the comparator circuit is composed of LF353, the linear optocoupler is composed of a diode, the bidirectional circuit is composed of a diode, the comparator circuit is mainly used for comparing a voltage signal obtained by amplifying a voltage interval value between a MOSFET switching tube source electrode of the secondary side output control circuit and a MOSFET switching tube electrode deletion control circuit, a comparison result represents the voltage condition of the point before the secondary side output control circuit and the MOSFET switching tube source electrode, namely the relation between a calibration voltage current in the single chip microcomputer output PWM conversion circuit and a voltage current after a front-stage secondary side output rectification circuit, the result obtained by the comparator circuit is used for determining the conduction degree of the linear optocoupler, and the bidirectional circuit is composed of the diode and a self-vibration type half-bridge driver frequency control end in the LLC resonance drive circuit to complete.
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CN110855153A (en) * 2019-11-28 2020-02-28 南京汇凯顺电子科技有限公司 Half-bridge topology high-voltage electrostatic power supply
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CN205123373U (en) * 2015-11-25 2016-03-30 广州市江科电子有限公司 Dual -purpose charger of soft switch speed of high efficiency
CN106787781A (en) * 2017-01-16 2017-05-31 昆明理工大学 A kind of microwave applications system of remote monitoring LCC resonant cavity enhanced photodetectors
CN206379880U (en) * 2017-01-18 2017-08-04 天津市海日电子有限公司 BOOST boosts and half-bridge LLC two-stage combination vibration controlling power circuits

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN205123373U (en) * 2015-11-25 2016-03-30 广州市江科电子有限公司 Dual -purpose charger of soft switch speed of high efficiency
CN106787781A (en) * 2017-01-16 2017-05-31 昆明理工大学 A kind of microwave applications system of remote monitoring LCC resonant cavity enhanced photodetectors
CN206379880U (en) * 2017-01-18 2017-08-04 天津市海日电子有限公司 BOOST boosts and half-bridge LLC two-stage combination vibration controlling power circuits

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