CN108880266B - Synchronous rectification circuit, chip and isolated synchronous rectification control circuit - Google Patents
Synchronous rectification circuit, chip and isolated synchronous rectification control circuit Download PDFInfo
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- CN108880266B CN108880266B CN201810785019.XA CN201810785019A CN108880266B CN 108880266 B CN108880266 B CN 108880266B CN 201810785019 A CN201810785019 A CN 201810785019A CN 108880266 B CN108880266 B CN 108880266B
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- 230000007306 turnover Effects 0.000 claims description 7
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- 230000006698 induction Effects 0.000 claims description 2
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Classifications
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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
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
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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
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
- H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
- H02M7/06—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes without control electrode or semiconductor devices without control electrode
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- 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)
- Rectifiers (AREA)
Abstract
Synchronous rectification circuit, chip and isolated synchronous rectification control circuit, synchronous rectification circuit includes: the device comprises a rectification switch tube, a driving module, a power module, a reference module, a charging module, an on comparator, an off comparison module, a minimum on time module and a logic control module. The charging voltage of the charging module reaches a certain threshold value, and the output end is turned on below a certain threshold value, wherein the charging voltage reaches the certain threshold value to prevent false starting when resonance occurs; the rectifying switch tube is turned off after the minimum on time, so that voltage oscillation at the output end is prevented from being turned off by mistake after the synchronous rectifying tube is turned on, the on-off control of the rectifying switch tube is accurate, and the switch tube can be turned on or turned off at the right moment.
Description
Technical Field
The invention belongs to the technical field of electronic power supplies, and particularly relates to a synchronous rectification circuit, a chip and an isolated synchronous rectification control circuit.
Background
At present, in a typical AC-DC power converter, a schottky diode is used for freewheeling at the secondary side of a transformer, and because the schottky diode has an unavoidable forward voltage drop, the voltage drop has a value of about 0.2V to 0.3V, so when the output power is relatively large, the power loss of the schottky diode is very large, in order to reduce unnecessary power loss, a rectifier switching tube is gradually used to replace the schottky diode, the on-resistance of the rectifier switching tube is only about 10-20mΩ, the voltage drop is only about 20 mV to 40mV even when the current passes through 2A, and the power loss is reduced by about 90%.
However, at present, even if a rectifier switching tube is adopted to replace a schottky diode, the control precision of a synchronous rectifier chip is not high, the rectifier switching tube cannot be accurately turned on or off, the phenomenon of explosion frequently occurs due to the influence of a primary side MOS switch, and meanwhile, the efficiency is still to be improved.
Disclosure of Invention
In view of the above, the embodiment of the invention provides a synchronous rectification circuit, a chip and an isolated synchronous rectification control circuit, which aim to solve the problem that the control precision of the traditional synchronous rectification chip is not high and a rectification switch tube cannot be accurately turned on and off.
A first aspect of an embodiment of the present invention provides a synchronous rectification circuit applied to an isolated AC-DC power supply circuit, including:
the rectification switch tube is used for being connected in series to the secondary side output loop of the transformer and is configured to rectify the induction voltage generated by the secondary side of the transformer;
the driving module is connected with the control end of the rectifying switch tube and is configured to be connected with a control signal to drive the rectifying switch tube to be switched on and off;
a power module configured to generate an operating voltage from the induced voltage;
a reference module connected to the power module and configured to generate a reference voltage;
the charging module is connected with the reference module, is configured to generate a charging voltage according to the induced voltage, and outputs a turnover signal when the charging voltage reaches a first reference voltage;
the turn-on comparator is connected with the reference module and the rectifying switch tube and is configured to output a turn-on indication signal when the voltage of the output end of the rectifying switch tube is lower than a second reference voltage;
the switching-off comparison module is connected with the input end and the output end of the rectifying switch tube and is configured to generate a first switching-off driving signal according to the voltage of the input end and the voltage of the output end of the rectifying switch tube;
the minimum on time module is connected with the power supply module and is configured to be connected with the control signal, charges by utilizing the working voltage and outputs a second off driving signal, wherein the second off driving signal is in a first state before the charging preset time is reached and is in a second state after the charging preset time is reached;
the logic control module is connected with the driving module, the charging module, the turn-on comparator, the turn-off comparison module and the minimum turn-on time module, and is configured to control the driving module to drive the rectifier switching tube to be turned on when receiving the overturning signal and the turn-on indication signal, and control the driving module to drive the rectifier switching tube to be turned off when receiving the first turn-off driving signal and the second turn-off driving signal in the second state.
The second aspect of the embodiment of the invention provides a synchronous rectification chip, which comprises the synchronous rectification circuit, wherein the synchronous rectification chip is provided with a power supply pin, a ground pin, a judging setting pin and an output pin, wherein the input end of the rectification switch tube is connected with the ground pin, the output end of the rectification switch tube is connected with the output pin, the power supply pin is connected with the power supply module, and the judging setting pin is connected with the charging module.
The third aspect of the embodiment of the invention provides an isolated synchronous rectification control circuit, which comprises a rectification filter unit connected with an alternating current power supply, a transformer for voltage conversion, a primary side MOS tube connected with a primary side of the transformer in series, and the synchronous rectification control circuit connected with a secondary side of the transformer.
The fourth aspect of the embodiment of the invention provides another isolated synchronous rectification control circuit, which comprises a rectification filter unit connected with an alternating current power supply, a transformer for voltage conversion, a primary side MOS tube connected with a primary side of the transformer in series, and the synchronous rectification control circuit further comprises the synchronous rectification chip connected with a secondary side of the transformer.
The rectification switch tube of the synchronous rectification circuit is turned on when the charging voltage of the charging module reaches a certain threshold value and the output end is lower than a certain threshold value, wherein the charging voltage reaches the certain threshold value to prevent false starting when resonance occurs; the rectifying switch tube is turned off after the minimum on time, so that voltage oscillation at the output end is prevented from being turned off by mistake after the synchronous rectifying tube is turned on, the on-off control of the rectifying switch tube is accurate, and the switch tube can be turned on or turned off at the right moment.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments or the description of the prior art will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic diagram of a synchronous rectification circuit according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of an exemplary circuit for use in the isolated AC-DC power circuit of the synchronous rectification circuit of FIG. 1;
FIG. 3 is a schematic diagram of an exemplary circuit of a charging module in the synchronous rectification circuit shown in FIG. 1;
FIG. 4 is a schematic diagram of an exemplary circuit for turning on a comparator in the synchronous rectification circuit shown in FIG. 1;
FIG. 5 is a schematic diagram of the internal circuits of the comparator and turn-on comparator in the charging module of the synchronous rectification circuit shown in FIGS. 3 and 4;
FIG. 6 is a schematic diagram of an exemplary circuit of a minimum on-time module in the synchronous rectification circuit shown in FIG. 1;
FIG. 7 is a schematic diagram of an exemplary circuit of a shutdown comparison module in the synchronous rectification circuit of FIG. 1;
FIG. 8 is a schematic diagram of the internal circuit of the comparator of the shutdown comparison module in the synchronous rectification circuit shown in FIG. 7;
fig. 9 is a schematic circuit diagram of an example of a shutdown logic control module in the synchronous rectification circuit shown in fig. 1.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
Referring to fig. 1, a schematic diagram of a synchronous rectification circuit according to an embodiment of the present invention is shown, for convenience of explanation, only the portions related to the embodiment are shown in detail as follows:
the synchronous rectification circuit can be used as a discrete circuit or can be manufactured into an integrated circuit to form a synchronous rectification chip so as to be applied to an isolated AC-DC power circuit. The synchronous rectification circuit includes a rectification switch tube 110, a driving module 120, a power module 130, a reference module 140, a charging module 150, an on comparator 160, a minimum on time module 170, an off comparison module 180 and a logic control module 190.
The rectifying switch tube 110 is used for being connected in series to an output loop of the secondary side of the transformer and is configured to rectify an induced voltage generated by the secondary side of the transformer, and when the transformer is connected to the AC-DC power circuit, an input end of the rectifying switch tube 110 is used for being connected with one end of the secondary side of the transformer, and an output end of the rectifying switch tube 110 is used for being connected with an output end of the synchronous rectifying circuit. For example, when the rectifying switch tube 110 is an N-type MOS tube, the source electrode of the N-type MOS tube is used as the output end, the drain electrode is used as the output end, and when the rectifying switch tube 110 is a P-type MOS tube, the reverse is true.
The driving module 120 is connected with the control end of the rectifying switch tube 110 and is configured to be connected with a control signal generated by the logic control module 190 to drive the rectifying switch tube 110 to be switched on and off; the power module 130 is configured to generate an operating voltage according to the induced voltage; the reference module 140 is connected to the power module 130 and configured to generate a reference voltage; the charging module 150 is connected to the reference module 140, and is configured to generate a charging voltage according to the induced voltage, and output a flipping signal when the charging voltage reaches a first reference voltage; the turn-on comparator 160 is connected to the reference module 140 and the rectifying switch tube 110, and is configured to output a turn-on indication signal at the output end of the rectifying switch tube 110 with a voltage lower than the second reference voltage of the parameter of the reference module 140; the turn-off comparison module 180 is connected to the input terminal and the output terminal of the rectifying switch tube 110, and is configured to generate a first turn-off driving signal according to the voltage of the input terminal and the voltage of the output terminal of the rectifying switch tube 110; the minimum on time module 170 is connected to the power module 130, and is configured to access a control signal, charge with an operating voltage, and output a second off driving signal, where the second off driving signal is in a first state before a charging preset time arrives, and is in a second state after the charging preset time arrives; the logic control module 190 is connected to the driving module 120, the charging module 150, the on comparator 160, the off comparing module 180, and the minimum on time module 170, and is configured to control the driving module 120 to drive the rectifying switch tube 110 to be turned on when receiving the flipping signal and the on indication signal, and control the driving module 120 to drive the rectifying switch tube 110 to be turned off when receiving the first off driving signal and the second off driving signal in the second state.
Referring to fig. 2, when the synchronous rectification circuit is manufactured into the synchronous rectification chip 101, the synchronous rectification chip has a power supply pin VCC, a ground pin GND, a determination setting pin AE, and an output pin draw in, wherein an input end of the rectification switch tube 110 is connected to the ground pin GND, an output end of the rectification switch tube 110 is connected to the output pin draw in, the power supply pin VCC is connected to the power supply module 130, and the determination setting pin AE is connected to the charging module 150. When the AC-DC power supply circuit is connected, the ground pin GND is connected with the non-homonymous end of the secondary side inductor LS of the transformer, the power supply pin VCC is also connected with the non-homonymous end of the secondary side inductor LS of the transformer through a filter capacitor C3 to be connected with the induced voltage, the judging setting pin AE is connected with the homonymous end of the secondary side inductor LS of the transformer through a voltage dividing/current limiting module R1 to be connected with the induced voltage, and the output pin DRAIN is connected to the output end of an output loop of the AC-DC power supply circuit.
Specifically, the application circuit diagram is divided into a primary side and a secondary side by a transformer for voltage conversion, the primary side part comprises a rectifying and filtering unit formed by diodes (D1, D2, D3 and D4) and a capacitor C1, the primary side inductor LP and a primary side MOS tube M1 connected in series with the primary side inductor LP, and the secondary side part comprises a synchronous rectifying chip 101, filtering capacitors C2 and C3, resistors R1, R2 and RL and a secondary side inductor LS.
When the primary MOS transistor M1 is turned on, the current of the primary inductor LP increases, energy is stored in the primary inductor, and at this time, the secondary inductor LS generates an induced voltage, which is connected to the determination setting pin AE of the synchronous rectification chip 101 through the resistor R1, and the induced voltage generates a charging current in the chip to charge the capacitor of the charging module 150. When the charging voltage reaches a certain threshold, a flip signal (on indication signal) is generated, and at this time, the output pin (i.e. the source electrode of the built-in rectifier tube) of the synchronous rectification chip 101 is at a high voltage level.
When the primary side MOS tube M1 is turned off, the current path of the primary side inductance LP is cut off, energy is transferred to the secondary side inductance LS through the transformer, the voltage of the secondary side inductance LS is reversed, the voltage of the ground pin GND is reduced, the voltage of the output pin DRAIN is reduced to be lower than that of the ground pin GND, the voltage of the output pin DRAIN is negative voltage relative to the ground pin GND, at this time, the synchronous rectification chip 101 detects that the voltage of the output pin DRAIN is reduced, when the voltage is lower than a certain threshold value, a turn-over signal (i.e. an on indication signal) is generated, and the turn-over signal of the charging module 150 act simultaneously, so that the rectification switch tube 110 can be turned on to provide a freewheel path.
In the process of freewheeling of the rectifying switch tube 110, the current of the secondary inductor LS gradually decreases, the voltage of the output pin DRAIN gradually rises from a negative voltage, and when the voltage of the output pin DRAIN approaches zero, the turn-off comparison module 180 generates a turn-over signal to turn off the rectifying switch tube 110, so that the rectifying switch tube 110 is turned on and off.
As described above, the conditions for the synchronous rectification switching tube 110 to open are two: 1. the charging voltage of the charging module 150 reaches a certain threshold value, which is used for preventing false start when resonance occurs; 2. the turn-on comparator 160 detects that the voltage at the output pin DRAIN is below a certain threshold. The above 2 conditions are simultaneously satisfied, and the rectifying switch tube 110 is turned on.
Specifically, as shown in fig. 3, the charging module 150 includes a current mirror unit 151, a capacitor C4, a discharging switch tube M0, and a comparator CMP1, wherein: the input end of the current mirror unit 151 is used as the input end (the judging setting pin AE) of the charging module 150 to be connected with the induced voltage, the output end is connected with one end of the capacitor C4, the other end of the capacitor C4 is connected with the ground, and the discharging switch tube M0 is connected with the capacitor C4 in parallel; the non-inverting input terminal of the comparator CMP1 is connected to one terminal of the second capacitor, the inverting input terminal is connected to the first reference voltage, and the output terminal is used as the output terminal of the charging module 150.
The AE terminal generates an induced voltage when the primary MOS transistor M1 is turned on, and the induced voltage generates a current, which is mirrored by the current mirror unit 151, to charge the capacitor C4. When the charging voltage reaches the first reference voltage VREF1, the output ON1 of the comparator CMP1 generates a high level, which is output to the logic control module 190 for processing.
As shown in fig. 4, the non-inverting input terminal of the turn-ON comparator 160 is connected to the second reference voltage VREF2, the inverting input terminal is connected to the output pin draw, when the primary side MOS transistor M1 is turned off, the voltage of the output pin draw decreases, and when the voltage of the output pin draw is lower than the second reference voltage VREF2, the output turn-ON indication signal ON2 of the turn-ON comparator 160 is at a high level, and the high level is output to the logic control module 190 for processing.
As shown in fig. 5, the circuits of the comparator CMP1 and the turn-on comparator 160 are typical 2-stage comparators.
In addition, the conditions for turning off the rectifying switch tube 110 are 2:
1. the delay reaches the minimum on time, which is that after the rectifying switch tube 110 is turned on, the delay Tmin receives the turn-off signal of the turn-off comparison module 180, and the purpose of setting the minimum on time is to prevent the voltage oscillation of the output pin DRAINDRAIN from being turned off by mistake after the synchronous rectifying tube is turned on; 2. the turn-off comparison module 180 outputs an effective signal, after the synchronous rectifier is turned on, the voltage of the output pin DRAIN starts to rise from a negative voltage, and when the voltage rises to a certain threshold VT1, the turn-off comparison module 180 outputs a turnover signal. The above 2 conditions are simultaneously satisfied, and the rectifying switch tube 110 is turned off.
In one embodiment, referring to fig. 6, the minimum on time module 170 includes a first PMOS transistor P1, a second PMOS transistor P2, a third PMOS transistor P3, a first NMOS transistor N1, a second NMOS transistor N2, a third NMOS transistor N3, a resistor R3, and a capacitor C5.
The grid electrode of the first PMOS tube P1 and the grid electrode of the first NMOS tube N1 are connected with access control signals, the source electrode of the first PMOS tube P1, the source electrode of the second PMOS tube P2 and the source electrode of the third PMOS tube P3 are connected with the output end of the power module 130 in a sharing mode, the drain electrode of the first PMOS tube P1, the drain electrode of the first NMOS tube N1, the grid electrode of the second PMOS tube P2 and the grid electrode of the second NMOS tube N2 are connected with each other in a sharing mode, the drain electrode of the second NMOS tube P2 is connected with the drain electrode of the second NMOS through a resistor R3, the grid electrode of the third PMOS tube P3, the grid electrode of the third NMOS tube N3, the drain electrode of the second NMOS and one end of the capacitor C5 are connected with each other in a sharing mode, and then the drain electrode of the third PMOS tube P3 and the drain electrode of the third NMOS tube N3 are used as the output end of the minimum on time module 170, and the other end of the capacitor C5, the source electrode of the first NMOS tube N1, the source electrode of the second NMOS tube N2 and the source electrode of the third NMOS tube N3 are grounded.
When the control signal pre_drv is at a high level, the synchronous rectification switch tube 110 is turned ON, and at this time, the working voltage VCC charges the capacitor C5 through the second PMOS tube P2 and the resistor R3, until the voltage of the capacitor C5 exceeds the inversion voltage of the third NMOS tube N3, the second off driving signal min_on output by the output terminal of the minimum ON time module 170 is pulled to a low level (the first state of the second off driving signal min_on is at a high level, and the second state is at a low level), and the low level is output to the logic control module 190 for processing. From the output of the control signal pre_drv high to the pull-down of the second off-drive signal min_on, there is a delay that is immediately the minimum ON-time. During the minimum on time, the rectifier switching tube 110 is always on. The toggling signal of the first off driving signal of the off comparing module 180 is accepted only after the on state duration exceeds the minimum on time.
In one embodiment, the turn-off comparison module 180 includes a turn-off comparator, where a non-inverting input terminal and an inverting input terminal of the turn-off comparator are sequentially connected to the output terminal and the input terminal of the rectifier switch 110; the output of the first shutdown comparator is the output of the shutdown comparison module 180. In this embodiment, the circuit for turning off the comparator is shown in fig. 6.
In another embodiment, referring to fig. 7, the turn-off comparison module 180 includes a first turn-off comparator CMP3, a second turn-off comparator CMP4, and a logic gate G1, wherein the logic gate G1 is an and gate or an or gate, and a non-inverting input terminal and an inverting input terminal of the first turn-off comparator CMP3 are sequentially connected to an output terminal and an input terminal of the rectifying switch tube 110; the non-inverting input end and the inverting input end of the second turn-off comparator CMP4 are sequentially connected with the output end and the input end of the rectifying switch tube 110, the output end of the first turn-off comparator CMP3 and the output end of the second turn-off comparator CMP4 are sequentially connected with the first input end and the second input end of the logic gate G1, the output end of the logic gate G1 serves as the output end of the turn-off comparison module 180, and the turning-over threshold value of the output signal of the first turn-off comparator CMP3 is different from the turning-over threshold value of the output signal of the second turn-off comparator CMP 4. The inputs of both are connected to the same potential, except that the output, the first OFF comparator CMP3 generates an output signal OFF1 and the second OFF comparator CMP4 generates an output signal OFF2. The logic gate G1 outputs the output signal OFF1 and the output signal OFF2 in the form of and or to the logic control block 190 as a first OFF driving signal OFF.
Specifically, referring to fig. 8, the first turn-off comparator CMP3 and the second turn-off comparator CMP4 each include a fourth PMOS transistor P4, a fifth PMOS transistor P5, a sixth POMS transistor P6, a seventh PMOS transistor P7, a fourth NOMS transistor N4, a fifth NMOS transistor N5, a sixth NMOS transistor N6, and a resistor R4, wherein: the source electrode of the fourth PMOS pipe P4 and the source electrode of the fifth PMOS pipe P5 are connected with working voltage, the grid electrode of the fourth PMOS pipe P4 and the grid electrode of the fifth PMOS pipe P5 are connected with bias voltage, the drain electrode of the fourth PMOS pipe P4, the source electrode of the sixth NMOS pipe P6 and one end of a resistor R4 are connected together, the grid electrode of the sixth PMOS pipe P6 is used as a positive input end of a comparator, the source electrode of the seventh PMOS pipe P7 is connected with the other end of the resistor R4, the grid electrode of the seventh PMOS pipe P7 is used as a reverse input end of the comparator, the drain electrode of the sixth PMOS pipe P6, the drain electrode of the fourth NOMS pipe N4, the grid electrode of the fourth NOMS pipe N4 and the grid electrode of the fifth NMOS pipe N5 are connected together, the drain electrode of the seventh PMOS pipe P7, the source electrode of the fifth NMOS pipe N5 and the source electrode of the sixth NMOS pipe N6 are connected together, and the drain electrode of the fifth NMOS pipe N6 are connected together as output ends of the comparator; the resistance of the resistor R4 on the first shutdown comparator CMP3 is different from the resistance of the resistor R4 on the second shutdown comparator CMP 4.
It should be noted that, the first turn-off comparator CMP3 and the second turn-off comparator CMP4 are also classical 2-stage comparators, unlike the turn-on comparator 160, the first turn-off comparator CMP3 and the second turn-off comparator CMP4 increase the resistor R4, and the resistor R4 is for generating the threshold voltages VT1 and VT2. Theoretically, the rectifier switch 110 is turned off only when the output pin DRAINDRAIN reaches 0V, but there is a delay from the output pin DRAINDRAIN reaching 0V to the turning off of the rectifier switch 110, so in order to avoid the situation that the rectifier switch 110 is not turned off in time to cause the explosion, the rectifier switch 110 needs to be turned off in advance when the output pin DRAINDRAIN has not reached 0V, so that the resistor R4 is added in the classical 2-stage comparator, VT1 and VT2 are generated, the absolute value of VT2 is smaller than VT1, and the resistor R4 of the second turn-off comparator CMP4 is smaller than the resistor R3 of the first turn-off comparator CMP 3.
Referring to fig. 9, the logic control module 190 includes a DFF flip-flop, a first and gate, and an RS flip-flop, wherein:
the D end, the VCC end, the CLK end and the RST end of the DFF trigger are respectively connected with the output end of the power module 130, the output end of the charging module 150 and the output end of the minimum on time module 170; the first input end of the first AND gate is connected with the Q end of the DFF trigger, and the second input end of the first AND gate is connected with the output end of the turn-on comparator 160; the R end of the RS trigger is connected with the output end of the turn-off comparison module 180, the S end of the RS trigger is connected with the output end of the first AND gate, and the Q end of the RS trigger is connected with the driving module 120.
Referring to fig. 1 to 9, the logic control module 190 receives the flipping signal ON1, the second OFF driving signal min_on, the ON indication signal ON2 and the first OFF driving signal OFF, generates the control signal pre_drv, and turns ON the rectifying switch tube 110 when the control signal pre_drv is at a high level, and turns OFF the rectifying switch tube 110 when the control signal prev_drv is at a low level. When the inversion signal ON1 and the ON indication signal ON2 are at a high level and the second off driving signal min_on is at a high level, the S terminal of the RS flip-flop is at a high level, and the pre_drv outputs a high level, and the rectifying switch tube 110 is turned ON. When the ON time of the rectifying switch tube 110 exceeds the minimum ON time, the second off driving signal min_on is pulled down, the DFF flip-flop is reset (the DFF flip-flop is reset at a low level), and the S terminal of the RS flip-flop is at a low level, and the state of the RS flip-flop is maintained. In one embodiment, when the output signal OFF1 and the output signal OFF2 are in the relationship, when the voltage of the output pin DRAINDRAIN continuously rises and is sequentially greater than VT1 and VT2, when the output signal OFF1 and the output signal OFF2 are both at a high level, the R terminal of the RS flip-flop is at a high level, at this time, the RS flip-flop is reset, the control signal pre_drv outputs a low level, and the rectifying switch tube 110 is turned OFF. In another embodiment, when the voltage of the output pin DRAINDRAIN continuously rises and is sequentially greater than VT1 and VT2, as long as any one of the output signal OFF1 and the output signal OFF2 becomes high, the R terminal of the RS flip-flop is high, at this time, the RS flip-flop is reset, the control signal pre_drv outputs low, and the rectifying switch 110 is turned OFF.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, and alternatives falling within the spirit and principles of the invention.
Claims (10)
1. A synchronous rectification circuit for use in an isolated AC-DC power circuit, comprising:
the rectification switch tube is used for being connected in series to the secondary side output loop of the transformer and is configured to rectify the induction voltage generated by the secondary side of the transformer, and the rectification switch tube comprises an N-type MOS tube or a P-type MOS tube;
the driving module is connected with the control end of the rectifying switch tube and is configured to be connected with a control signal to drive the rectifying switch tube to be switched on and off;
a power module configured to generate an operating voltage from the induced voltage;
a reference module connected to the power module and configured to generate a reference voltage;
the charging module is connected with the reference module, is configured to generate a charging voltage according to the induced voltage, and outputs a turnover signal when the charging voltage reaches a first reference voltage;
the turn-on comparator is connected with the reference module and the rectifying switch tube and is configured to output a turn-on indication signal when the voltage of the output end of the rectifying switch tube is lower than a second reference voltage;
the switching-off comparison module is connected with the input end and the output end of the rectifying switch tube and is configured to generate a first switching-off driving signal according to the voltage of the input end and the voltage of the output end of the rectifying switch tube;
the minimum on time module is connected with the power supply module and is configured to be connected with the control signal, charges by utilizing the working voltage and outputs a second off driving signal, wherein the second off driving signal is in a first state before the charging preset time is reached and is in a second state after the charging preset time is reached;
the logic control module is connected with the driving module, the charging module, the turn-on comparator, the turn-off comparison module and the minimum turn-on time module, and is configured to control the driving module to drive the rectifier switching tube to be turned on when receiving the overturning signal and the turn-on indication signal, and control the driving module to drive the rectifier switching tube to be turned off when receiving the first turn-off driving signal and the second turn-off driving signal in the second state.
2. The synchronous rectification circuit of claim 1, wherein said logic control module comprises a DFF flip-flop, a first and gate, and an RS flip-flop, wherein:
the D end, the VCC end, the CLK end and the RST end of the DFF trigger are respectively connected with the output end of the power supply module, the output end of the charging module and the output end of the minimum on time module;
the first input end of the first AND gate is connected with the Q end of the DFF trigger, and the second input end of the first AND gate is connected with the output end of the turn-on comparator;
and the R end of the RS trigger is connected with the output end of the turn-off comparison module, the S end of the RS trigger is connected with the output end of the first AND gate, and the Q end of the RS trigger is connected with the driving module.
3. The synchronous rectification circuit of claim 1 or 2, wherein said minimum on-time module comprises a first PMOS transistor, a second PMOS transistor, a third PMOS transistor, a first NMOS transistor, a second NMOS transistor, a third NMOS transistor, a first resistor, and a first capacitor, wherein:
the grid electrode of the first PMOS tube and the grid electrode of the first NMOS tube are connected with the control signal in a sharing mode, the source electrode of the first PMOS tube, the source electrode of the second PMOS tube and the source electrode of the third PMOS tube are connected with the output end of the power module in a sharing mode, the drain electrode of the first PMOS tube, the drain electrode of the first NMOS tube, the grid electrode of the second PMOS tube and the grid electrode of the second NMOS tube are connected in a sharing mode, the drain electrode of the second PMOS tube is connected with the drain electrode of the second NMOS tube through the first resistor, the grid electrode of the third PMOS tube, the drain electrode of the second NMOS tube and one end of the first capacitor are connected in a sharing mode, the drain electrode of the third PMOS tube, the drain electrode of the third NMOS tube are used as the output end of the minimum on time module in a sharing mode, and the other end of the first capacitor, the source electrode of the first NMOS tube, the source electrode of the second NMOS tube and the source electrode of the third NMOS tube are grounded in a sharing mode.
4. The synchronous rectification circuit as claimed in claim 1 or 2, wherein the turn-off comparison module comprises a first turn-off comparator, and a non-inverting input end and an inverting input end of the first turn-off comparator are sequentially connected with an output end and an input end of the rectification switch tube; the output end of the first turn-off comparator is used as the output end of the turn-off comparison module.
5. The synchronous rectification circuit as claimed in claim 1 or 2, wherein the turn-off comparison module comprises a first turn-off comparator, a second turn-off comparator and a logic gate, the logic gate is an and gate or an or gate, and a non-inverting input terminal and an inverting input terminal of the first turn-off comparator are sequentially connected with an output terminal and an input terminal of the rectification switch tube; the positive phase input end and the negative phase input end of the second turn-off comparator are sequentially connected with the output end and the input end of the rectifying switch tube, the output end of the first turn-off comparator and the output end of the second turn-off comparator are sequentially connected with the first input end and the second input end of the logic gate, the output end of the logic gate is used as the output end of the turn-off comparison module, and the turnover threshold value of the output signal of the first turn-off comparator is different from that of the output signal of the second turn-off comparator.
6. The synchronous rectification circuit of claim 5, wherein said first shutdown comparator and said second shutdown comparator each comprise a fourth PMOS transistor, a fifth PMOS transistor, a sixth POMS transistor, a seventh PMOS transistor, a fourth NOMS transistor, a fifth NMOS transistor, a sixth NMOS transistor, and a second resistor, wherein:
the source electrode of the fourth PMOS tube and the source electrode of the fifth PMOS tube are connected with the working voltage, the grid electrode of the fourth PMOS tube and the grid electrode of the fifth PMOS tube are connected with bias voltage, the drain electrode of the fourth PMOS tube, the source electrode of the sixth NMOS tube and one end of the second resistor are connected together, the grid electrode of the sixth PMOS tube is used as a positive input end of the comparator, the source electrode of the seventh PMOS tube is connected with the other end of the second resistor, the grid electrode of the seventh PMOS tube is used as a reverse input end of the comparator, the drain electrode of the sixth PMOS tube, the drain electrode of the fourth NOMS tube, the grid electrode of the fourth NOMS tube and the grid electrode of the fifth NMOS tube are connected together, the drain electrode of the seventh PMOS tube, the drain electrode of the fifth NMOS tube and the grid electrode of the sixth NMOS tube are connected together, the source electrode of the fourth NOMS tube, the source electrode of the fifth NMOS tube and the source electrode of the sixth NMOS tube are grounded together, and the drain electrode of the sixth NMOS tube and the drain electrode of the fifth NMOS tube are connected together as a common output end of the comparator;
the resistance value of the second resistor on the first turn-off comparator is different from the resistance value of the second resistor on the second turn-off comparator.
7. The synchronous rectification circuit as claimed in claim 1 or 2, wherein said charging module comprises a current mirror unit, a second capacitor, a discharge switch tube and a comparator, wherein:
the input end of the current mirror unit is connected with the induced voltage, the output end of the current mirror unit is connected with one end of the second capacitor, the other end of the second capacitor is grounded, and the discharge switch tube is connected with the second capacitor in parallel; the non-inverting input end of the comparator is connected with one end of the second capacitor, the inverting input end of the comparator is connected with the first reference voltage, and the output end of the comparator is used as the output end of the charging module.
8. The synchronous rectification chip is characterized by comprising the synchronous rectification circuit as claimed in any one of claims 1 to 7, wherein the synchronous rectification chip is provided with a power supply pin, a ground pin, a judging setting pin and an output pin, the input end of the rectification switch tube is connected with the ground pin, the output end of the rectification switch tube is connected with the output pin, the power supply pin is connected with the power supply module, and the judging setting pin is connected with the charging module.
9. An isolated synchronous rectification control circuit comprising a rectification filter unit connected with an alternating current power supply, a transformer for voltage conversion and a primary side MOS tube connected in series with the primary side of the transformer, and further comprising the synchronous rectification circuit as claimed in any one of claims 1 to 7 connected with the secondary side of the transformer.
10. An isolated synchronous rectification control circuit comprising a rectification filter unit connected with an alternating current power supply, a transformer for voltage conversion, a primary side MOS tube connected in series with the primary side of the transformer, and a synchronous rectification chip as claimed in claim 8 connected with the secondary side of the transformer.
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| CN110429833A (en) * | 2019-08-13 | 2019-11-08 | 纽福克斯光电科技（上海）有限公司 | A kind of circuit of synchronous rectification of charger |
| CN112865541B (en) * | 2021-01-22 | 2022-03-29 | 成都启臣微电子股份有限公司 | Synchronous rectification controller, synchronous rectification system and synchronous rectification control method |
| CN113852279B (en) * | 2021-09-09 | 2023-12-01 | 无锡博通微电子技术有限公司 | Control system and control method for high-voltage power supply |
| CN114204809B (en) * | 2021-11-18 | 2023-10-20 | 华人运通(江苏)技术有限公司 | Control device of power output circuit and power supply system |
| CN115377939B (en) * | 2022-07-18 | 2023-05-23 | 北京炎黄国芯科技有限公司 | Adjustable undervoltage protection circuit and electronic equipment |
| CN115987266B (en) * | 2023-01-16 | 2023-11-28 | 深圳市思远半导体有限公司 | Switching circuit, control method and chip of NMOS switching tube |
| CN116087582B (en) * | 2023-04-07 | 2023-07-07 | 成都芯翼科技有限公司 | Voltage input side protection circuit, current detection amplifier and voltage detection amplifier |
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