CN111711367A - Bidirectional magnetic isolation feedback circuit containing synchronous rectification time sequence transmission - Google Patents

Bidirectional magnetic isolation feedback circuit containing synchronous rectification time sequence transmission Download PDF

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Publication number
CN111711367A
CN111711367A CN202010717494.0A CN202010717494A CN111711367A CN 111711367 A CN111711367 A CN 111711367A CN 202010717494 A CN202010717494 A CN 202010717494A CN 111711367 A CN111711367 A CN 111711367A
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transformer
synchronous rectification
capacitor
circuit
signal
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Inventor
朱伟龙
赵隆冬
王毅
刘林
金阳
高东辉
丁瀚
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CETC 43 Research Institute
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CETC 43 Research Institute
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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
    • H02M3/33576—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 having at least one active switching element at the secondary side of an isolation transformer
    • H02M3/33592—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 having at least one active switching element at the secondary side of an isolation transformer having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer
    • 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
    • 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
    • H02M1/0003—Details of control, feedback or regulation circuits
    • H02M1/0006—Arrangements for supplying an adequate voltage to the control circuit of converters
    • 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
    • H02M1/0003—Details of control, feedback or regulation circuits
    • H02M1/0025—Arrangements for modifying reference values, feedback values or error values in the control loop of a converter
    • 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
    • H02M1/38—Means for preventing simultaneous conduction of switches
    • H02M1/385—Means for preventing simultaneous conduction of switches with means for correcting output voltage deviations introduced by the dead time
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

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

Abstract

The invention discloses a bidirectional magnetic isolation feedback circuit containing synchronous rectification time sequence transmission, and belongs to the field of isolation feedback circuits and synchronous rectification driving. The pulse adjusting unit generates a rectangular pulse signal for driving the transformer T, modulates the duty ratio and the time sequence of the driving pulse, and controls and configures a dead zone between the driving pulse signal and a driving signal of the switching tube Q2; the synchronous rectification time sequence transmission unit is used for conditioning a synchronous rectification driving time sequence transmitted to the secondary side of the transformer T; the bidirectional magnetic isolation feedback unit is used for transmitting the primary synchronous rectification timing signal to the secondary and transmitting the secondary error amplification signal to the primary. The invention can accurately realize the isolated transmission of error signals, realizes high-performance feedback and closed-loop control, has the advantages of high portability and low design difficulty, and is suitable for high-reliability and high-efficiency application occasions under various powers.

Description

Bidirectional magnetic isolation feedback circuit containing synchronous rectification time sequence transmission
Technical Field
The invention relates to the field of isolation feedback circuits and synchronous rectification driving, in particular to a bidirectional magnetic isolation feedback circuit comprising synchronous rectification time sequence transmission.
Background
The optical coupling isolation feedback is the most extensive in industrial application, and has the advantages of simplicity and few devices. But limited by the inherent defects of the optical coupler, the aging problem of the light emitting diode and the photosensitive device, the CTR (current transfer ratio) changes along with the temperature and the service time, and the service life and the reliability of the current transfer ratio are far inferior to those of the magnetic isolation feedback. In the application occasions (such as aerospace and aviation power supplies) with high reliability and high quality level, a magnetic feedback technology must be adopted, and magnetic isolation feedback is not influenced by temperature and time drift and is stable and reliable.
The magnetic isolation feedback is to drive a feedback magnetic transformer by using high-frequency switching value, and to convert the sampling value of the secondary side to the primary side by the transformer for closed-loop control. The currently commonly used magnetic feedback technology mainly focuses on chips of UC1901 series of IR, VPT and TI, and each of the technologies has advantages and disadvantages: the IR series of magnetic feedback technology devices are more, a current source needs to be generated on the primary side, and the occupied power supply space is larger; the VPT series magnetic feedback technology needs two magnetic rings and has larger volume; the TI series of magnetic feedback technology needs a special control chip, and high-quality chips are expensive and difficult to obtain.
As shown in fig. 1, a bidirectional magnetic isolation feedback circuit (publication No. CN206850674U) disclosed in chinese patent discloses a magnetic feedback technique capable of bidirectional transmission, in which a carrier signal is taken from an oscillation signal of a DC/DC converter PWM, so as to avoid mutual interference generated by different operating frequencies, and when the DC/DC converter is in operating states with different input voltages and different loads, the oscillation signal is stable without increasing a "dead load". The above patent does not have synchronous rectification timing adjustment and transfer functions.
The synchronous rectification technology is a technology which adopts a power MOSFET with extremely low on-state resistance as a diode for rectification to replace the traditional rectifier diode so as to reduce the loss of a rectification circuit and improve the efficiency of a converter. The synchronous rectification technology is an important means for improving the efficiency of the DC-DC converter, and how to properly design a synchronous rectification driving circuit and control a timing sequence is the core of the synchronous rectification technology.
The current common synchronous rectification driving technology mainly comprises three main categories, namely transformer winding self-driving, primary signal transmission to secondary driving and secondary special driving IC. The driving voltage of the winding self-driving technology is not fixed, is limited by input and output voltages, and has narrow application range, poor expansibility and poor reliability; the transmission of the primary signal to the secondary driving scheme requires a special isolation transformer for signal isolation transmission, and the driving dead zone is difficult to adjust and occupies more components; the secondary special drive IC has lower working frequency, needs the assistance of a peripheral circuit, and has expensive and difficult purchase of a high-quality grade chip.
The traditional magnetic isolation feedback circuit uses 1 isolation transformer, and the synchronous rectification time sequence transmission also uses 1 isolation transformer, namely two isolation transformers are adopted to respectively complete magnetic isolation feedback and synchronous rectification time sequence control, specifically, the magnetic isolation feedback control is firstly carried out, then other dead zone generating circuits are utilized to generate PWM2 signals with dead zones with PWM1, and then the isolation transformers are utilized to carry out isolation transmission and drive secondary synchronous rectification tubes. Namely, the magnetic isolation feedback circuit and the synchronous rectification time sequence transmission circuit are independent and irrelevant, and most of components used for realizing the functions are not overlapped and not shared.
Disclosure of Invention
It is therefore an object of the present invention to provide a bidirectional magnetic isolation feedback circuit including synchronous rectification timing transmission to solve the above problems.
In order to achieve the purpose, the invention provides the following technical scheme:
a bidirectional magnetic isolation feedback circuit containing synchronous rectification time sequence transmission comprises a bidirectional magnetic isolation feedback unit, wherein the bidirectional magnetic isolation feedback unit comprises a transformer T, an error sampling amplifying circuit and a triode Q4, the input end of the error sampling amplifying circuit is connected with a voltage dividing circuit of output voltage of a DC-DC conversion unit, the base electrode of the triode Q4 is connected with the output end of the error sampling amplifying circuit, the emitter electrode of the triode is connected with the synonym end of a secondary winding of the transformer T after being connected with the cathode of a diode D4, the collector electrode of the triode is connected with secondary ground, and the synonym end of the secondary winding of the transformer T is connected with the cathode of a diode D3 and then connected with secondary ground; the primary winding of the transformer is connected with a level conversion circuit,
the pulse adjusting unit and the synchronous rectification time sequence transmission unit are also included;
the pulse adjusting unit is configured to be connected with a voltage dividing circuit of the oscillation signal generated by the PWM controller N2 and a reference voltage Vref through two input ends of a comparator U1 respectively, and output a narrow pulse ahead of the PWM1 signal to a primary winding of the transformer T so as to be transferred to a secondary winding through the transformer T to generate a PWM2 signal;
the PWM1 signal is generated by a PWM controller N2, a PWM controller N2 generates the dead time between the PWM1 signal and the PWM2 signal by varying peripheral parameters;
the synchronous rectification timing transfer unit is configured to turn off the synchronous rectification transistor SR2 in the DC-DC conversion unit by a high level of the PWM2 signal and turn on the synchronous rectification transistor SR2 by a low level of the PWM2 signal.
As a modification of the invention, in order to provide a stable secondary auxiliary power supply on the secondary side of the transformer T, the synonym terminal of the secondary winding of the transformer T is connected with the cathode of the diode D6, the cathode of the diode D5 after the capacitor C3 and the secondary auxiliary power supply V in sequenceCCSThe anode of the diode D5 is connected with the dotted terminal of the secondary winding of the transformer T; a resistor Ron is connected between the cathode of the diode D5 and the base of the triode Q4, and a capacitor C2 is connected between the base and the secondary ground.
As a development of the invention, the level conversion circuit comprises a diode S for converting the level transferred from the secondary side to the primary side of the transformer T to a positive levelDCapacitor CS/HResistance RIB、RIAThe homonymous ends of the primary winding of the transformer T are sequentially connected with a diode S in seriesDResistance RIB、RIAA reference voltage Vref, a diode SDThe cathode of the transformer is connected with a transformer T, and the anode of the transformer T passes through a capacitor CS/HAnd (4) grounding.
As an improved scheme of the invention, the synchronous rectification timing sequence transmission unit comprises a triode Q1 and a field effect transistor Q3, wherein the base electrode of the triode Q1 is connected with the same-name end of a secondary winding of a transformer T, the collector electrode of the triode Q1 is connected with the secondary ground, one path of the emitter electrode is connected with the cathode of a diode D2 and then connected with the same-name end of the secondary winding of the transformer T, the other path of the emitter electrode is connected with the grid electrode of a field effect transistor Q3, and the source electrode of the field effect transistor Q3. A resistor R8 is connected between the source and the gate of the field effect transistor Q3, and a resistor R7 is connected between the base and the collector of the triode Q1.
As an improved scheme of the present invention, in order to facilitate adjustment of the duty ratio of the PWM1 signal input to the primary side of the transformer T, the pulse adjusting unit further includes a duty ratio limiting circuit, the duty ratio limiting circuit includes a transistor Q2, one end of an emitter of the transistor Q2 is connected to a primary auxiliary power VCC, the other end of the emitter is connected to an output end of a comparator U1 through series resistors R4 and R5, a base is connected to a common end of the resistors R4 and R5, and a collector is connected to a dotted end of the primary winding of the transformer T through a resistor R9.
As an improvement of the present invention, in order to facilitate the adjustment of the duty ratio of the PWM1 signal inputted to the primary side of the transformer T, a capacitor C1 and a resistor R6 are connected in sequence between the output terminal of the comparator U1 and the base of the transistor Q2.
As an improved scheme of the present invention, the error sampling amplifying circuit includes an operational amplifier U2, a capacitor CHS, a CFS and a resistor RF, an output terminal of the operational amplifier U2 is connected to a base of the transistor Q4, the capacitor CHS is connected between a negative input terminal and an output terminal of the operational amplifier U2, two ends of the capacitor CHS are connected in parallel to the capacitor CFS and the resistor RF which are connected in series, a positive input terminal of the operational amplifier U2 is connected to a secondary ground through a capacitor C0, and a negative input terminal is connected to an output terminal of the DC-DC conversion unit through a voltage dividing circuit.
As an improved scheme of the invention, the error sampling amplifying circuit comprises a voltage stabilizing source N1 and a capacitor CHS、CFSThe positive electrode of a resistor RF and a voltage regulator N1 is connected with the secondary ground, and the reference end is connected with a DC-DC converter through a second voltage division circuitOutput terminal of the switch unit, capacitor CHSA capacitor C connected between the negative electrode of the regulator N1 and the reference terminalHSBoth ends of the capacitor C are connected in parallel and in seriesFSAnd a resistor RF, the negative electrode of the voltage regulator N1 is also connected to the base electrode of a triode Q4, and the other path is connected to a secondary auxiliary power supply V through a resistor R5CCS。
Has the advantages that: the invention drives a small transformer T by a configurable narrow pulse signal with fixed duty ratio and amplitude, and enables the transformer T to work in different working modes by a shunt circuit of a diode, thereby achieving the purpose of isolating and transmitting a synchronous rectification driving time sequence signal and a loop feedback signal.
Drawings
FIG. 1 is a circuit diagram of a bi-directional transmission magnetic isolation feedback circuit disclosed in the prior art;
FIG. 2 is a circuit block diagram of the present invention;
FIG. 3 is another circuit block diagram of the present invention;
FIG. 4 is a circuit diagram of the pulse adjustment unit, the synchronous rectification timing transmission unit and the bidirectional magnetic isolation feedback unit according to the first embodiment of the present invention;
FIG. 5 is a circuit diagram of a pulse adjustment unit, a synchronous rectification timing transmission unit and a bidirectional magnetic isolation feedback unit according to a second embodiment of the present invention;
FIG. 6 is a circuit diagram of a third embodiment of the pulse adjusting unit, the synchronous rectification timing sequence transmission unit and the bidirectional magnetic isolation feedback unit according to the present invention;
FIG. 7 is a circuit diagram of a fourth embodiment of the pulse adjustment unit, the synchronous rectification timing transmission unit and the bidirectional magnetic isolation feedback unit according to the present invention;
FIG. 8 is a circuit diagram of the transformer T of the present invention operating in a quasi-forward mode;
FIG. 9 is a circuit diagram of the transformer T of the present invention operating in a flyback-like DCM mode (core reset);
FIG. 10 is a circuit diagram of the transformer T of the present invention operating in a flyback-like DCM mode (after core reset);
fig. 11 is a waveform diagram of the transformer T of the present invention in the operating mode of fig. 8-10;
FIG. 12 is a schematic diagram of the PWM controller N2 according to the present invention and the waveform of the output oscillating signal;
fig. 13 is a dead-zone control waveform diagram of the PWM1 signal and the PWM2 signal under the oscillation signal output by the PWM controller N2 according to the present invention.
In the figure: 1-a pulse adjusting unit; 2-a synchronous rectification timing sequence transmission unit; 3-a bidirectional magnetic isolation feedback unit; and a 4-DC-DC conversion unit.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention is applied to a DC-DC conversion unit, referring to fig. 2-3, the DC-DC conversion unit comprises a PWM controller N2, a transformer T1, a field effect transistor S1 and a field effect transistor SR2, the PWM controller N2 outputs a PWM1 signal to a grid electrode of a field effect transistor S1, the field effect transistor S1 transmits the PWM1 signal to a field effect transistor SR2 through a magnetic isolation transformer, and a drain electrode of the field effect transistor Q3 is connected with the grid electrode of the field effect transistor S2. The model of the control chip of the PWM controller N2 may be selected as UC1843 or UC 1803.
As shown in fig. 2, one implementation structure of the DC-DC conversion unit is: the transformer T1 secondary winding further comprises a field effect transistor SR1, the grid electrode of the field effect transistor SR1 and the drain electrode of the field effect transistor SR2 are both connected with the homonymous end of the transformer T1 secondary winding, one path of the drain electrode of the field effect transistor SR1 is connected with the synonym end of the transformer T1 secondary winding, the other path of the drain electrode of the field effect transistor SR1 is connected with the grid electrode of the field effect transistor SR2 through a diode, and the source electrodes of the field effect transistors SR1 and SR2 are. The implementation structure is a forward winding self-driven synchronous rectification topology, and the application can also be applied to flyback synchronous rectification topology control.
As shown in fig. 3, another implementation structure of the DC-DC conversion unit is as follows: the drain of the field effect transistor SR2 is connected to the dotted terminal of the secondary winding of transformer T1, the gate is connected to the dotted terminal of the secondary winding of transformer T1, and the drain is connected to the secondary ground.
The structure of the DC-DC conversion unit is not improved in the present application, and is not described in detail herein.
Embodiment 1, the bidirectional magnetic isolation feedback circuit including synchronous rectification timing sequence transfer provided by the present invention includes a bidirectional magnetic isolation feedback unit, the bidirectional magnetic isolation feedback unit includes a transformer T, an error sampling amplifying circuit and a transistor Q4, an input end of the error sampling amplifying circuit is connected to a voltage dividing circuit of an output voltage of a DC-DC conversion unit, a base of the transistor Q4 is connected to an output end of the error sampling amplifying circuit, an emitter is connected to a different name end of a secondary winding of the transformer T after being connected to a cathode of a diode D4, a collector is connected to a secondary ground, a same name end of the secondary winding of the transformer T is connected to a cathode of a diode D3 and then to a secondary ground; and the primary winding of the transformer is connected with the level conversion circuit.
Preferably, the level shift circuit includes a diode SDCapacitor CS/HResistance RIB、RIAThe homonymous ends of the primary winding of the transformer T are sequentially connected with a diode S in seriesDResistance RIB、RIAA reference voltage Vref, a diode SDThe cathode of the transformer is connected with a transformer T, and the anode of the transformer T passes through a capacitor CS/HAnd (4) grounding.
Specifically, the reference voltage Vref is provided by PWM controller N2, resistor RIB、RIAIs a voltage-dividing resistor, a capacitor CS/HIs the sampling capacitance. The level conversion circuit is mainly used for converting VS/H (negative level) transmitted from the secondary side of the transformer T to the primary side into VFB (positive level about 2.5V), then the VFB is sent to the inverting input end of an operational amplifier in the PWM controller N2 to be compared with an internal reference (non-inverting input end), and then the duty ratio of a PWM1 signal output by the PWM controller N2 is controlled, so that closed-loop feedback of a power supply is realized, and a loop feedback circuit is formed.
The circuit also comprises a pulse adjusting unit and a synchronous rectification time sequence transmission unit.
The pulse adjusting unit is configured to be connected with a voltage dividing circuit of the oscillation signal generated by the PWM controller N2 and the reference voltage Vref through two input terminals of the comparator U1, respectively, and output a narrow pulse ahead of the PWM1 signal to the primary winding of the transformer T to be transferred to the secondary winding through the transformer T to generate the PWM2 signal.
The PWM1 signal is generated by a PWM controller N2, and a PWM controller N2 generates the dead time between the PWM1 signal and the PWM2 signal by varying peripheral parameters.
The synchronous rectification timing transfer unit is configured to turn off the synchronous rectification transistor SR2 in the DC-DC conversion unit by a high level of the PWM2 signal and turn on the synchronous rectification transistor SR2 by a low level of the PWM2 signal.
In example 2, preferably, an implementation manner of the synchronous rectification timing transfer unit includes a transistor Q1 and a field-effect transistor Q3, the transistor Q1 is a PNP transistor, a base of the transistor Q1 is connected to a dotted terminal of a secondary winding of the transformer T, a collector is connected to a secondary ground, one path of an emitter is connected to a cathode of the diode D2 and then to the dotted terminal of the secondary winding of the transformer T, the other path is connected to a gate of the field-effect transistor Q3, and a source of the field-effect transistor Q3 is connected to the secondary ground. A resistor R8 is connected between the source and the gate of the field effect transistor Q3, and a resistor R7 is connected between the base and the collector of the triode Q1.
The synchronous rectification timing conditioning unit is used for logic conversion (switching on or switching off the synchronous rectification tube SR2) and driving capability improvement of a PWM2 signal transmitted to the secondary side of the transformer T. The high level of the PWM2 signal at the anode of the diode D2 (and on the secondary side of the transformer T) is used for turning on the field effect transistor Q3, and is converted into a low level signal of the PWM2 through the field effect transistor Q3, and is used for turning off the synchronous rectifier SR 2; the low level of the PWM2 signal at the anode of the diode D2 is used for turning on the triode Q1, further turning off the field effect transistor Q3, releasing the grid pull-down state of the synchronous rectifier SR2 and enabling the grid of the synchronous rectifier SR2 to be high-impedance.
Specifically, the pulse adjusting unit includes a comparator U1, a positive input terminal of the comparator U1 is connected to an oscillation signal generated by the PWM controller N2, a negative input terminal is connected to a reference voltage Vref through a voltage dividing circuit, an output terminal is connected to a dotted terminal of the primary winding of the transformer T, and a dotted terminal of the primary winding of the transformer T is grounded.
Embodiment 3, preferably, as shown in fig. 4, the pulse adjusting unit further includes a duty cycle limiting circuit, the duty cycle limiting circuit includes a transistor Q2, one end of an emitter of the transistor Q2 is connected to the primary auxiliary power VCC, the other end of the emitter is connected to the output terminal of the comparator U1 through series resistors R4 and R5, a base is connected to a common terminal of the resistors R4 and R5, and a collector is connected to the same-name terminal of the primary winding of the transformer T through the resistor R9.
By configuring the peripheral parameters of the positive and negative inputs of the comparator U1, the duty cycle of the pulse generated by the comparator U1 can be adjusted, and the duty cycle of the output signal of the comparator U1 can be controlled and limited. In this embodiment, the duty ratio of the switching tube Q2 is consistent with the duty ratio of the comparator U1, so that the duty ratio of the switching tube Q2 can be adjusted by the duty ratio limiting circuit, and further the duty ratio of the transformer T can be adjusted.
Embodiment 4, preferably, as shown in fig. 5, on the basis of embodiment 3, a capacitor C1 and a resistor R6 are connected in sequence between the output terminal of the comparator U1 and the base of the transistor Q2. The capacitor C1 and the resistor R6 additionally add a duty cycle limiting circuit for limiting the on-time (duty cycle) of the transistor Q2.
In embodiment 3, when the RC oscillating signal input to the comparator U1 is abnormal, the duty ratio of the comparator U1 is large, and the duty ratio of the transistor Q2 is also large, which may cause the transformer T to be saturated and is not easily adjusted. However, in this embodiment, the duty ratio of the transistor Q2 can be directly limited by adding the capacitor C1 and the resistor R6, so as to limit the duty ratio of the transformer T, prevent the transformer T from being saturated due to a wide duty ratio pulse generated by malfunction of the comparator U1, and improve reliability.
Embodiment 5, as shown in fig. 6, optionally, an implementation structure of the error sampling amplifying circuit includes an operational amplifier U2 and a capacitor CHS、CFSThe output end of the operational amplifier U2 is connected with the base electrode of a triode Q4 and a capacitor CHSConnected between the negative input terminal and the output terminal of the operational amplifier U2, and a capacitor CHSBoth ends of the capacitor C are connected in parallel and in seriesFSAnd a resistor RF, the positive input terminal of the amplifier U2The capacitor C0 is connected with the secondary ground, and the negative input end is connected with the output end of the DC-DC conversion unit through a voltage division circuit.
The error sampling amplifying circuit divides and samples the output voltage Vo of the DC-DC conversion unit, outputs a sampled voltage signal to a negative input end of an operational amplifier U2, sets a reference at a positive input end of an operational amplifier U2, and outputs an error amplifying signal to a base electrode of a triode Q4 after comparison and error amplification. Capacitor CHS、CFSAnd the loop compensation circuit and the resistor RF form a loop compensation circuit which is used for adjusting the stability of the power loop of the bidirectional magnetic isolation feedback circuit and optimizing the dynamic performance.
Embodiment 6, as shown in fig. 7, optionally, another implementation structure of the error sampling amplifying circuit includes a voltage regulator N1, a capacitor CHS、CFSThe positive electrode of a resistor RF and a voltage-stabilizing source N1 is connected with the secondary ground, the reference end is connected with the output end of the DC-DC conversion unit through a second voltage-dividing circuit, and a capacitor CHSA capacitor C connected between the negative electrode of the regulator N1 and the reference terminalHSBoth ends of the capacitor C are connected in parallel and in seriesFSAnd a resistor RF, the negative electrode of the voltage regulator N1 is also connected to the base electrode of a triode Q4, and the other path is connected to a secondary auxiliary power supply V through a resistor R5CCS。
Embodiment 7, optionally, the synonym terminal of the secondary winding of the transformer T is connected to the cathode of the diode D6, the cathode of the diode D5 after the capacitor C3, and the secondary auxiliary power source V in sequenceCCSThe anode of the diode D5 is connected with the dotted terminal of the secondary winding of the transformer T; a resistor Ron is connected between the cathode of the diode D5 and the base of the triode Q4, and a capacitor C2 is connected between the base and the secondary ground.
The capacitor C3 is provided with a secondary auxiliary voltage source, which is supplied by the comparator U1 and transmitted through the isolation transformer T. Base electrode connecting resistors Ron to V of triode Q4CCSThe operational amplifier U2 is used for pulling up the output end of the operational amplifier U2, and the capacitor C2 is connected to the output end of the operational amplifier U2 and plays a role in stabilizing the error amplification signal VEA and improving the dynamic response speed. The output of the op-amp U2 is pulled up to provide an initial error amplified signal, which is sent to the primary of the transformer T, and the PWM controller N2 starts the PWM output, if the error signal is initially low,the control loop controls the PWM controller N2 not to output the PWM1 signal, and the whole circuit cannot open the closed-loop work.
In this embodiment, the pulse adjusting unit generates a rectangular pulse signal for driving the transformer T, modulates the duty ratio and the timing sequence of the driving pulse, and simultaneously controls and configures a dead zone between the driving pulse signal and a driving signal of the switching tube Q2 on the primary side of the transformer T; the synchronous rectification timing sequence transmission unit is used for conditioning a synchronous rectification driving timing sequence transmitted to the secondary side of the transformer T and controlling the turn-off of a synchronous rectification tube SR2 on the secondary side winding side of the transformer T1; the bidirectional magnetic isolation feedback unit is used for transferring the primary energy of the transformer T to the secondary and generating a stable secondary auxiliary power supply VCCSAnd the primary synchronous rectification timing signal is transmitted to the secondary, and meanwhile, a secondary error amplification signal acquired by the error sampling amplification circuit is transmitted to the primary.
The bidirectional magnetic isolation feedback unit enables the unit circuit to work in different working modes through a diode shunt circuit formed by transformers T, D3, D4, D5 and D6, a synchronous rectification driving time sequence and auxiliary power supply are transmitted from a primary side to a secondary side, and then a secondary error amplification signal is transmitted to the primary side, so that bidirectional transmission of signals is achieved.
In this embodiment, the comparator U1Being a high-speed comparator, a triode Q1、Q2、Q4Are all PNP triodes, and the transformer T is a small-volume signal isolation transformer; the oscillation signal is a triangular wave output by a clock control circuit inside the PWM controller N2, and the divided voltage V of the reference voltage VrefsetFor controlling the comparator U1The output flip threshold and duty cycle of; the PWM controller N2 outputs a PWM1 signal, and the PWM1 signal is a field effect transistor S1The field effect transistor Q3 outputs a PWM2 signal to the gate of the field effect transistor SR2, the PWM2 signal is a synchronous rectification timing control signal transmitted to the secondary side, and the PWM signal is transmitted to the field effect transistor S1Before turning on, turn off field effect transistor SR in advance2。
The specific principle of this embodiment is as follows:
1. establishment of secondary auxiliary power supply and magnetically isolated transmission of error signal
In the pulse adjusting unit, the oscillation signal (RC signal) is compared with the Vset level, the comparator U1 generates a rectangular wave for controlling the on/off of the transistor Q2 (the frequency is the switching frequency, the duty ratio is controlled by the Vset level), according to the on/off condition of the transistor Q2, the magnetic isolation feedback process of the transformer T in one period can be divided into 3 working states, and fig. 11 is a waveform diagram of the transformer T in the following three working states.
1) Class forward mode: as shown in fig. 8, when the transistor Q2 is turned on, the primary side of the transformer T receives a forward voltage and starts to be excited, the exciting current increases from 0, and the diodes D5 and D6 are turned on, so that the transformer T charges the capacitor C3. The diodes D3 and D4 are turned off, and the transistor Q4 is turned off. The primary auxiliary power supply VCC creates a stable secondary auxiliary power supply V for the secondary winding through the transformer TCCS，VCCS＝VCC-VD5-VD6-VQ1(CE)The sampling switch diode SD is off.
2) Flyback-like CCM mode (core reset): as shown in fig. 9, the transistor Q2Turning off, inverting the polarity of primary and secondary windings of transformer T to generate back electromotive force, and diode D5，D6Cut-off, switching of the path of the secondary winding, diode D3，D4Conducting, triode Q4And conducting. VD—VBThe intermediate voltage being clamped and the current being supplied by winding VDVia diode D4Triode Q4EB junction (PN junction), capacitor C2, diode D3 return winding VB. Diode S of transformer T primary sideDOn, the capacitance CS/HSampling the error amplified signal V transmitted from the secondary of the transformer TEAAnd maintained.
VD-VB＝VD4+VQ4(EB)+VEA+VD3
VA＝VB-VD＝-(VD4+VQ4(EB)+VEA+VD3)
VS/H＝VA+VSD＝-(VD4+VQ4(EB)+VEA+VD3)+VSD
Sample and holdSignal VS/HAnd the negative value is converted into about 2.5V level through the level shift circuit and is sent to an internal error amplifier of the PWM controller N2, and the feedback closed loop is completed. Reference voltage VrefProviding positive voltage bias to the shift circuit, and dividing the voltage by a voltage dividing resistor RIAAnd RIBObtaining the appropriate VFBA level.
3) Flyback-like DCM mode (after core reset): as shown in fig. 10, after the magnetic reset of the transformer T is completed, the energy is completely transferred. The diodes D5, D6, D3 and D4 are all cut off, and the transistor Q2 is cut off. The residual leakage inductance L of the transformer T and the CE junction capacitance and the line resistance of the triode Q2 form LRC damped oscillation, and the energy of the leakage inductance is dissipated.
2. Synchronous rectification timing sequence dead zone control
With the RC signal generated by PWM controller N2, a dead band is created between the PWM1 signal and the PWM2 signal, ensuring that fet SR2 turns off before the primary switching fet S1 turns on. The specific implementation process analysis is as follows:
as shown in fig. 12-13, the resistor RT and the capacitor CT are resistance-capacitance arranged at the periphery of the PWM controller N2 for controlling the frequency of the PWM controller N2 and the RC triangular wave generated by the PWM controller N2. The product of the resistor RT and the capacitor CT determines the frequency of the triangular wave, and under the condition of the same frequency, if the capacity of the configured capacitor CT is large, the slope of the falling edge of the triangular wave is small, and the falling time is long; if the capacity of the capacitor CT is small, the slope of the falling edge of the triangular wave is large, and the falling time is short. When the capacitor CT signal starts to rise, the PWM controller N2 turns on the PWM output (i.e., PWM1), the PWM1 starts to drive the power transformer T1, energy is transferred to the secondary, and the PWM1 turns off to end energy transfer in the period, and the PWM1 duty cycle is determined by the loop feedback circuit.
By configuring different RT and CT parameters, the slope of the falling edge of the triangle wave is controlled, and the time of the falling edge determines the maximum dead time for which PWM2 can be designed to advance PWM 1.
By utilizing the falling edge of an RC signal output by a PWM controller N2, before a PWM1 signal is started, a PWM2 signal is established in advance, the PWM2 signal is transmitted to the secondary side of a transformer T through a magnetic isolation transformer T1, a field effect transistor SR2 is turned off, and dead zone control is formed; when the level of the falling edge of the RC signal is lower than the divided voltage Vsef sampled by the comparator U1, the comparator U1 outputs a low level, the transistor Q2 is turned on, and the transformer T operates. When the RC signal goes to a rising edge and the voltage is greater than the divided voltage Vsef, the comparator U1 outputs a high level and the transformer T does not operate. Thus, a synchronous rectification timing control signal that advances the PWM1 signal is obtained by the pulse adjustment unit. The dead time Δ t is determined by the resistor RT, the capacitor CT, and the reference voltage Vref set by the PWM controller N2.
Besides the duty ratio d of the PWM2 signal is controlled by the Vset level at the negative input terminal of the comparator U1 and the RC signal configured at the positive input terminal, at the output terminal of the comparator U1, the capacitor C1, the resistors R6, R4 and R5 in the duty ratio limiting circuit play a role of limiting the maximum duty ratio, so as to limit the on-time of the transistor Q2; therefore, not only is the dead band between the PWM1 signal and the PWM2 signal controllable, but the maximum duty cycle of the PWM2 control signal is also controllable.
The synchronous rectification control signal PWM2 is transmitted to the secondary side, and the synchronous rectification timing sequence transmission unit turns off the field effect transistor SR2 in advance before the field effect transistor S1 is turned on, so that the primary side and the secondary side of the transformer T1 are prevented from being shared. When the PWM2 signal advances the PWM1 signal and goes high, the fet Q3 is driven to turn on through the diode D2, the gate of the fet SR2 is pulled low, and the fet SR2 is turned off. When the PWM2 signal is converted into low level, the triode Q1 is conducted, the grid electrode of the field effect transistor Q3 is pulled low, the field effect transistor Q3 is turned off, the synchronous rectification time sequence transmission unit does not work on the field effect transistor SR2, and the conduction of the field effect transistor SR2 can be controlled by self-driving.
The invention drives a small-sized isolation transformer by a configurable narrow pulse signal with fixed duty ratio and amplitude, and enables the transformer T to work in different working modes by a shunt circuit of a diode, thereby completing the establishment of a secondary auxiliary power supply and achieving the purposes of isolating and transmitting a synchronous rectification driving time sequence signal and a loop feedback signal.
The invention has the beneficial effects that:
1. the invention adopts the bidirectional magnetic isolation feedback circuit to replace optical coupler isolation feedback, avoids the influence of the service life of the optical coupler, performance degradation and batch inconsistency on product design, can accurately realize the isolation transmission of error signals, and realizes high-performance feedback and closed-loop control.
2. The invention provides a stable auxiliary power supply for the secondary side of the transformer T before the output voltage is established, and the secondary auxiliary power supply is decoupled with the DC/DC output voltage, thereby reducing the complexity of loop feedback design and reducing the difficulty of soft start design; meanwhile, the output constant current control can be designed by using the auxiliary power supply independent of the output voltage, and more accurate overcurrent protection is provided for the secondary side.
3. The coupling degree of the bidirectional magnetic isolation feedback unit, the pulse adjusting unit, the synchronous rectification time sequence transmission unit and the DC-DC conversion unit is low, the portability of the bidirectional magnetic isolation feedback unit is high, the bidirectional magnetic isolation feedback unit is not influenced by factors such as input voltage, output voltage and power, and the bidirectional magnetic isolation feedback unit is suitable for high-reliability and high-efficiency application occasions under various powers.
4. The transformer T is used for simultaneously transmitting the primary driving time sequence to the secondary driving time sequence, and the transformer used for the switching time sequence control of the synchronous rectifying tube (field effect tube SR2) is reduced compared with the traditional scheme.
5. The voltage value and the duty ratio of the narrow pulse transmitted by the transformer T are fixed, the narrow pulse is not influenced by the DC-DC conversion unit, the design difficulty of the transformer T is simplified, and a small-size magnetic ring can be adopted.
Although the present description is described in terms of embodiments, not every embodiment includes only a single embodiment, and such description is for clarity only, and those skilled in the art should be able to integrate the description as a whole, and the embodiments can be appropriately combined to form other embodiments as will be understood by those skilled in the art.
In the description of the present invention, it should be noted that relational terms such as first and second, and the like, may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
In the description of the present invention, it should be further noted that the terms "upper", "lower", "inside", "outside", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings or orientations or positional relationships conventionally put in use of products of the present invention, which are merely for convenience of description and simplification of description, but do not indicate or imply that the referred devices or elements must have specific orientations, be constructed in specific orientations, and be operated, and thus, should not be construed as limiting the present invention.
In the description of the present invention, it should also be noted that, unless otherwise explicitly specified or limited, the terms "disposed" and "connected" are to be interpreted broadly, e.g., as being either fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
Therefore, the above description is only a preferred embodiment of the present application, and is not intended to limit the scope of the present application; all changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.

Claims (8)

1. A bidirectional magnetic isolation feedback circuit containing synchronous rectification time sequence transmission comprises a bidirectional magnetic isolation feedback unit, wherein the bidirectional magnetic isolation feedback unit comprises a transformer T, an error sampling amplifying circuit and a triode Q4, the input end of the error sampling amplifying circuit is connected with a voltage dividing circuit of output voltage of a DC-DC conversion unit, the base electrode of the triode Q4 is connected with the output end of the error sampling amplifying circuit, the emitter electrode of the triode is connected with the synonym end of a secondary winding of the transformer T after being connected with the cathode of a diode D4, the collector electrode of the triode is connected with secondary ground, and the synonym end of the secondary winding of the transformer T is connected with the cathode of a diode D3 and then connected with secondary ground; the primary winding of the transformer is connected with a level switching circuit, which is characterized in that,
the pulse adjusting unit and the synchronous rectification time sequence transmission unit are also included;
the pulse adjusting unit is configured to be connected with a voltage dividing circuit of the oscillation signal generated by the PWM controller N2 and a reference voltage Vref through two input ends of a comparator U1 respectively, and output a narrow pulse ahead of the PWM1 signal to a primary winding of the transformer T so as to be transferred to a secondary winding through the transformer T to generate a PWM2 signal;
the PWM1 signal is generated by a PWM controller N2, a PWM controller N2 generates the dead time between the PWM1 signal and the PWM2 signal by varying peripheral parameters;
the synchronous rectification timing transfer unit is configured to turn off the synchronous rectification transistor SR2 in the DC-DC conversion unit by a high level of the PWM2 signal and turn on the synchronous rectification transistor SR2 by a low level of the PWM2 signal.
2. The circuit of claim 1, wherein the synonym terminal of the secondary winding of the transformer T is connected to the cathode of a diode D6, the cathode of a diode D5 after the capacitor C3 and the secondary auxiliary power supply V in sequenceCCSThe anode of the diode D5 is connected with the dotted terminal of the secondary winding of the transformer T; a resistor Ron is connected between the cathode of the diode D5 and the base of the triode Q4, and a capacitor C2 is connected between the base and the secondary ground.
3. A bi-directional magnetic isolation feedback circuit including synchronous rectification timing transfer as claimed in claim 1 or 2, wherein said level shift circuit includes a diode SDCapacitor CS/HResistance RIB、RIASaid transformation of voltageDiodes S are sequentially connected in series at the same-name end of primary winding of the TDResistance RIB、RIAA reference voltage Vref, a diode SDThe cathode of the transformer is connected with a transformer T, and the anode of the transformer T passes through a capacitor CS/HAnd (4) grounding.
4. The bidirectional magnetic isolation feedback circuit containing synchronous rectification timing transmission of claim 1 or 2, wherein the synchronous rectification timing transmission unit comprises a transistor Q1 and a field effect transistor Q3, wherein the base of the transistor Q1 is connected with the same-name end of the secondary winding of the transformer T, the collector is connected with the secondary ground, the emitter is connected with the same-name end of the secondary winding of the transformer T after being connected with the cathode of a diode D2, the other emitter is connected with the gate of a field effect transistor Q3, and the source of the field effect transistor Q3 is connected with the secondary ground. A resistor R8 is connected between the source and the gate of the field effect transistor Q3, and a resistor R7 is connected between the base and the collector of the triode Q1.
5. The bidirectional magnetic isolation feedback circuit with synchronous rectification timing transmission as claimed in claim 1 or 2, wherein the pulse adjusting unit further comprises a duty cycle limiting circuit, the duty cycle limiting circuit comprises a transistor Q2, one end of an emitter of a transistor Q2 is connected with a primary auxiliary power source VCC, the other end of the emitter is connected with an output end of a comparator U1 through series resistors R4 and R5, a base is connected with a common end of resistors R4 and R5, and a collector is connected with a same-name end of a primary winding of the transformer T through a resistor R9.
6. The bi-directional magnetic isolation feedback circuit with synchronous rectification timing transmission as claimed in claim 5, wherein a capacitor C1 and a resistor R6 are connected between the output terminal of the comparator U1 and the base of the transistor Q2 in sequence.
7. The circuit of claim 2, wherein the error sampling and amplifying circuit comprises an operational amplifier U2 and a capacitor CHS、CFSThe output end of the amplifier U2 is connected with a triodeBase of Q4, capacitor CHSConnected between the negative input terminal and the output terminal of the operational amplifier U2, and a capacitor CHSBoth ends of the capacitor C are connected in parallel and in seriesFSWith the resistor RF, the operational amplifier U2 has a positive input terminal connected to the secondary ground through the capacitor C0, and a negative input terminal connected to the output terminal of the DC-DC conversion unit through the voltage divider circuit.
8. The bidirectional magnetic isolation feedback circuit with synchronous rectification timing transmission as claimed in claim 2, wherein the error sampling amplifying circuit comprises a voltage regulator N1, a capacitor CHS、CFSThe positive electrode of a resistor RF and a voltage-stabilizing source N1 is connected with the secondary ground, the reference end is connected with the output end of the DC-DC conversion unit through a second voltage-dividing circuit, and a capacitor CHSA capacitor C connected between the negative electrode of the regulator N1 and the reference terminalHSBoth ends of the capacitor C are connected in parallel and in seriesFSAnd a resistor RF, the negative electrode of the voltage regulator N1 is also connected to the base electrode of a triode Q4, and the other path is connected to a secondary auxiliary power supply V through a resistor R5CCS。
CN202010717494.0A 2020-07-23 2020-07-23 Bidirectional magnetic isolation feedback circuit containing synchronous rectification time sequence transmission Pending CN111711367A (en)

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112532026A (en) * 2020-12-25 2021-03-19 西北工业大学 Magnetic isolation feedback circuit of space power supply
CN113114042A (en) * 2021-04-30 2021-07-13 重庆斯微奇电子技术有限公司 Pulse signal duty ratio isolation transmission circuit
CN113397550A (en) * 2021-06-19 2021-09-17 华北理工大学 Wrist strap self-locking type mobile electrocardiograph
CN113938036A (en) * 2021-10-19 2022-01-14 西安微电子技术研究所 Magnetic isolation complementary signal generating circuit for single-ended flyback synchronous rectification drive

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112532026A (en) * 2020-12-25 2021-03-19 西北工业大学 Magnetic isolation feedback circuit of space power supply
CN113114042A (en) * 2021-04-30 2021-07-13 重庆斯微奇电子技术有限公司 Pulse signal duty ratio isolation transmission circuit
CN113114042B (en) * 2021-04-30 2023-05-02 重庆斯微奇电子技术有限公司 Pulse signal duty ratio isolation transfer circuit
CN113397550A (en) * 2021-06-19 2021-09-17 华北理工大学 Wrist strap self-locking type mobile electrocardiograph
CN113938036A (en) * 2021-10-19 2022-01-14 西安微电子技术研究所 Magnetic isolation complementary signal generating circuit for single-ended flyback synchronous rectification drive
CN113938036B (en) * 2021-10-19 2023-06-16 西安微电子技术研究所 Magnetically isolated complementary signal generating circuit for single-ended flyback synchronous rectification driving

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