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CN109149968B - Synchronous rectifier diode and synchronous rectification control circuit - Google Patents

Synchronous rectifier diode and synchronous rectification control circuit Download PDF

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Publication number
CN109149968B
CN109149968B CN201810983557.XA CN201810983557A CN109149968B CN 109149968 B CN109149968 B CN 109149968B CN 201810983557 A CN201810983557 A CN 201810983557A CN 109149968 B CN109149968 B CN 109149968B
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voltage
module
pull
energy storage
storage capacitor
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CN109149968A (en
Inventor
邓亚旭
范麟
余晋川
万天才
刘永光
徐骅
李明剑
贺旭东
陈勇屹
谭棋心
王皓嶙
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Chongqing Southwest Integrated Circuit Design Co ltd
CETC 24 Research Institute
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Chongqing Southwest Integrated Circuit Design Co ltd
CETC 24 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
    • 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
    • H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/21—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/217—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only

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

Abstract

The invention discloses a synchronous rectifier diode and a synchronous rectifier control circuit; the utility model provides a synchronous rectifier diode, includes synchronous rectification control circuit, power MOSFET pipe and energy storage capacitor, its characterized in that: the upper polar plate of the energy storage capacitor is connected with the power output end of the synchronous rectification control circuit, the lower polar plate of the energy storage capacitor is connected with the anode of the synchronous rectification diode, and the source electrode, the drain electrode and the grid electrode of the power MOSFET are respectively connected with the anode and the cathode of the synchronous rectification diode and the signal output end of the synchronous rectification control circuit; the synchronous rectification control circuit comprises a reference circuit, a power supply generation circuit, an under-voltage protection circuit, a logic module, an AK voltage stabilizing module, a pull-up module and a pull-down module; the reference circuit provides reference voltage for the undervoltage protection circuit; the synchronous rectification control circuit can directly replace the traditional rectifier diode, does not need external power supply, is simple to apply, can be widely applied to the field of power management, and has good application prospect.

Description

Synchronous rectifier diode and synchronous rectification control circuit
Technical Field
The invention relates to a rectifier diode, in particular to a synchronous rectifier diode and a synchronous rectification control circuit.
Background
The synchronous rectification technology is a new technology which adopts a power MOSFET with lower on-resistance to match with a special synchronous rectification control circuit to replace the traditional rectifier diode, can reduce the rectification loss, improve the efficiency of a DC/DC converter and an AC/DC converter, and avoids the problem of dead zone voltage caused by Schottky barrier voltage of a common diode. Based on these advantages, the synchronous rectification technology is widely applied in the field of power management. With the gradual improvement of performance requirements of DC/DC and AC/DC converters on cost, efficiency, application complexity and the like, the traditional synchronous rectification technical scheme has some problems, firstly, the synchronous rectification control circuit of the type needs to be matched with a power MOSFET to realize the synchronous rectification function and can not directly replace a rectifier diode from the aspect of application; the synchronous rectification control circuit is switched off when the drain-source voltage becomes positive or the current starts to flow from the drain end to the source end, the principle is that the source-drain voltage of the power MOSFET is judged, if the voltage difference is lower than a threshold value, the power MOSFET is switched off, and if the voltage difference is higher than the threshold value, the power MOSFET is switched on, but due to the fact that the on-resistance of the MOSFET is lower, and the continuous change of the source-drain current and the maladjustment of the judgment circuit, the judgment circuit cannot accurately judge when the power MOSFET is switched off; in addition, factors such as the time delay of the decision circuit and the gate drive delay of the MOSFET can cause problems such as early turn-off or late turn-off of the MOSFET. If the MOSFET is turned off in advance, the efficiency is lost, and the source-drain voltage difference is increased after the MOSFET is turned off, so that the MOSFET is turned on again due to logic errors; if the MOSFET is turned off after the delay, a large back-sink current from the drain terminal to the source terminal may be caused, which may cause a reduction in efficiency of the synchronous rectification circuit and may also cause a large ringing to cause the MOSFET to be turned back on during the ringing.
Fig. 1 shows a conventional synchronous rectification control circuit architecture, which comprises a reference module, a determination module, a logic module and a driving module, and the basic idea is to detect a voltage difference between two ends of a source (a) and a drain (K) of a MOSFET through the determination module, output a signal to the logic module if the voltage difference is a positive voltage, and control the driving module to turn on the MOSFET through logic operation; if the voltage difference between the source end and the drain end is detected to be zero, namely the current passing through the MOSFET from the source end to the drain end is reduced to zero, the judgment module outputs an opposite signal to the logic module, and the drive module is controlled to close the MOSFET through logic operation. The module for judging in the framework is usually a comparator, logic errors are easily caused due to the fact that the comparator has factors such as offset error, process deviation and circuit delay, and the comparator can work only by being matched with an external MOSFET when being applied, so that the application is complex.
Disclosure of Invention
In order to solve the problems that the existing synchronous rectification control circuit is inaccurate in closing control of the MOSFET and needs an external power supply, the invention provides a synchronous rectification diode and a synchronous rectification control circuit.
The first technical scheme of the invention is that the synchronous rectification diode comprises a synchronous rectification control circuit, a power MOSFET tube and an energy storage capacitor, and is characterized in that: the upper electrode plate of the energy storage capacitor is connected with the power output end of the synchronous rectification control circuit, the lower electrode plate of the energy storage capacitor is connected with the anode of the synchronous rectification diode, and the source electrode, the drain electrode and the grid electrode of the power MOSFET are respectively connected with the anode and the cathode of the synchronous rectification diode and the signal output end of the synchronous rectification control circuit.
The synchronous rectification control circuit detects the voltage difference between the two ends of the source electrode and the drain electrode of the power MOSFET, outputs a signal to the grid electrode of the power MOSFET if the voltage difference is positive, opens the power MOSFET, and outputs a signal to the grid electrode of the power MOSFET if the voltage difference between the two ends of the source electrode and the drain electrode of the power MOSFET is zero or negative, and closes the power MOSFET.
The synchronous rectification control circuit comprises a reference circuit, a power supply generation circuit, an under-voltage protection circuit, a logic module, an AK voltage stabilizing module, a pull-up module and a pull-down module; the reference circuit provides a reference voltage for the undervoltage protection circuit.
The power generation circuit is used for converting pulse voltage between the anode and the cathode of the synchronous rectifier diode into stable direct-current voltage to charge the energy storage capacitor.
The under-voltage protection circuit is used for detecting the positive voltage of the energy storage capacitor and outputting a control signal to the logic module.
The logic module receives a control signal output by the under-voltage protection circuit and outputs the control logic signal to the AK voltage stabilizing module, the pull-up module and the pull-down module.
The AK voltage stabilizing module, the pull-up module and the pull-down module are controlled by control logic signals output by the logic module, respectively detect pulse voltage between the anode and the cathode of the synchronous rectifier diode, output signals to the grid of the power MOSFET, and feed back the grid voltage of the power MOSFET to the logic module.
Further, when the voltage of the positive electrode of the energy storage capacitor is charged from 0V to the undervoltage protection threshold stage, the power supply generation circuit charges the energy storage capacitor; when the voltage of the positive electrode of the energy storage capacitor is lower than the undervoltage protection threshold, the logic module outputs a control logic signal to close the AK voltage stabilizing module, the pull-up module, the pull-down module and the external power MOSFET.
When the voltage of the positive electrode of the energy storage capacitor reaches the undervoltage locking threshold, the undervoltage protection circuit opens the pull-up module, the AK voltage stabilizing module and the pull-down module.
Further, the AK voltage stabilizing module comprises a first comparator, a second comparator and a clamping MOS tube; the non-inverting input end of the first comparator is connected with the inverting input end of the second comparator, the inverting input end of the first comparator is connected with the non-inverting input end of the second comparator, the first comparator and the second comparator detect pulse voltage between the anode and the cathode of the synchronous rectifier diode at the same time, the first comparator and the second comparator output voltage to the drain electrode and the source electrode of the clamp voltage MOS tube respectively, and the second comparator also outputs voltage to the grid electrode of the power MOSFET tube; and the grid electrode of the clamping MOS tube receives a reference voltage.
Furthermore, the power generation circuit comprises a diode I, a diode V, a fourth adjusting tube and an error amplifier; one input end of the error amplifier is connected with the anode of the synchronous rectifier diode through a second resistor, and is connected with the upper polar plate of the energy storage capacitor through a first resistor; the other input end of the error amplifier receives a second reference voltage signal, and the output end of the error amplifier is connected with the grid electrode of the fourth adjusting tube through a switch circuit; the drain end of the fourth adjusting tube receives a pulse signal output by the synchronous rectifier diode through the first diode, the pulse signal charges the energy storage capacitor through the fourth adjusting tube and the fifth diode, when the charging voltage of the energy storage capacitor reaches a set value, the error amplifier outputs a signal to close the fourth adjusting tube, the pulse signal stops charging the energy storage capacitor, when the voltage on the energy storage capacitor is consumed by other circuit units to be lower than the set value, the error amplifier outputs a signal to open the fourth adjusting tube, and the pulse signal charges the energy storage capacitor.
The second technical scheme of the invention is that the synchronous rectification control circuit for the synchronous rectification diode comprises a reference circuit, a power supply generating circuit, an under-voltage protection circuit, a logic module, an AK voltage stabilizing module, a pull-up module and a pull-down module; the reference circuit provides a reference/reference voltage for the undervoltage protection circuit; the method is characterized in that:
the power generation circuit is used for converting pulse voltage between the anode and the cathode of the synchronous rectifier diode into stable direct-current voltage to charge the energy storage capacitor.
The under-voltage protection circuit is used for detecting the positive voltage of the energy storage capacitor and outputting a control signal to the logic module.
The logic module receives a control signal output by the under-voltage protection circuit and outputs the control logic signal to the AK voltage stabilizing module, the pull-up module and the pull-down module.
The AK voltage stabilizing module, the pull-up module and the pull-down module are controlled by control logic signals output by the logic module, respectively detect pulse voltage between an anode and a cathode of the synchronous rectifier diode, output the voltage to a grid of the power MOSFET, and feed back the grid voltage of the power MOSFET to the logic module.
The synchronous rectification control circuit provided by the invention can effectively pre-turn off the grid voltage of an external power MOSFET to be close to the threshold voltage when the MOSFET current is close to zero, so that the AK voltage difference is clamped in a certain voltage range, and the MOSFET is completely turned off when the MOSFET current is reduced to zero, thereby improving the accuracy and efficiency of turning off the MOSFET. Meanwhile, when the pull-down module closes the MOSFET, the grid voltage of an external power MOSFET is reduced to be close to the threshold voltage, the time delay of the pull-down module for closing the MOSFET is reduced, and the purpose of rapidly closing the MOSFET when the current of the power MOSFET is reduced to zero is achieved.
The synchronous rectification control circuit and the power generation circuit have the beneficial effects that: the power MOSFET switching circuit can directly replace the traditional rectifier diode, the synchronous rectifier control circuit does not need external power supply, the AK voltage difference is accurately detected, when the current passing through the power MOSFET is zero, the power MOSFET is accurately switched off, the accuracy and the efficiency of switching off the MOSFET are improved, and the purpose of rapidly switching off the MOSFET when the current of the power MOSFET is reduced to zero is achieved.
Drawings
Fig. 1 is a block diagram of a conventional synchronous rectification control circuit system.
Fig. 2 is a schematic diagram of a synchronous rectifier diode package according to the present invention.
Fig. 3 is a system block diagram of a synchronous rectification control circuit according to the present invention.
Fig. 4 is a schematic circuit diagram of an AK voltage stabilizing module in the synchronous rectification control circuit module according to the present invention.
Fig. 5 is a schematic circuit diagram of a power generating circuit according to the present invention.
Fig. 6 is a simulated waveform diagram of one working cycle of the synchronous rectification control circuit according to the invention.
Fig. 7 is a partially enlarged simulation diagram of the synchronous rectification control circuit according to the present invention when the power MOSFET is turned on.
Fig. 8 is a partially enlarged simulation diagram of the synchronous rectification control circuit according to the present invention when the power MOSFET is turned off.
Fig. 9 is a waveform diagram of a simulation of the operation of a power generation circuit according to the present invention.
FIG. 10 is a partial enlarged simulation waveform diagram of a power generation circuit according to the present invention during power-up.
FIG. 11 is a partial enlarged simulation waveform diagram of a power supply generating circuit in the voltage holding process according to the present invention.
Detailed Description
Example 1: referring to fig. 2 to 5, a synchronous rectification diode includes a synchronous rectification control circuit, a power MOSFET tube and an energy storage capacitor C, an upper plate of the energy storage capacitor C is connected to a power output terminal of the synchronous rectification control circuit, a lower plate of the energy storage capacitor C is connected to an anode a of the synchronous rectification diode, and a source, a drain and a gate of the power MOSFET are respectively connected to the anode a and the cathode K of the synchronous rectification diode and a signal output terminal of the synchronous rectification control circuit.
The synchronous rectification control circuit detects the voltage difference between the two ends of the source electrode and the drain electrode of the power MOSFET tube M, if the voltage difference is positive voltage, a signal is output to the grid electrode of the power MOSFET tube M, the power MOSFET tube M is opened, and if the voltage difference between the two ends of the source electrode and the drain electrode of the power MOSFET tube M is zero or negative voltage, the signal is output to the grid electrode of the power MOSFET tube M, and the power MOSFET tube M is closed.
The synchronous rectification control circuit comprises a reference circuit 1, a power supply generation circuit 2, an under-voltage protection circuit 3, a logic module 4, an AK voltage stabilizing module 6, an up-pulling module 5 and a down-pulling module 7; the reference circuit 1 provides a reference voltage for the undervoltage protection circuit 3.
The power generation circuit 2 is used for converting the pulse voltage between the anode A and the cathode K of the synchronous rectifier diode into stable direct-current voltage to charge the energy storage capacitor C.
The undervoltage protection circuit 3 is used for detecting the positive voltage of the energy storage capacitor C and outputting a control signal to the logic module 4.
The logic module 4 receives the control signal output by the under-voltage protection circuit 3, and outputs the control logic signal to the AK voltage stabilization module 6, the pull-up module 5, and the pull-down module 7.
The AK voltage stabilizing module 6, the pull-up module 5 and the pull-down module 7 are all controlled by the control logic signal output by the logic module 4, respectively detect the pulse voltage between the anode a and the cathode K of the synchronous rectifier diode, output a signal to the gate G of the power MOSFET tube M, and feed back the voltage of the gate G of the power MOSFET tube M to the logic module 4.
The SIP schematic diagram of the synchronous rectification control circuit, the power MOSFET and the energy storage capacitor for multi-chip packaging is shown in FIG. 2, only two leading-out ends, namely an A end and a K end, are arranged after packaging, the A end and the K end are completely corresponding to the A end and the K end of a traditional rectifier diode, the synchronous rectification control circuit can be directly replaced in application, and the rectification efficiency is improved by 3% -5% compared with the traditional rectifier diode.
The working process of the invention is divided into five stages: the first stage is as follows: the preparation stage is a stage of charging the CAP terminal voltage from 0V to the undervoltage protection threshold voltage in the system power-on process. In the power-on process, the power generation circuit charges the energy storage capacitor continuously by the periodic pulse voltage at the end A, at the moment, due to the existence of the undervoltage protection circuit, when the CAP voltage is lower than the undervoltage protection threshold voltage, the pull-up module, the AK voltage stabilizing module and the pull-down module are closed, the power MOSFET is ensured to be closed, at the moment, the whole system works through a parasitic diode of the power MOSFET, and the forward voltage difference between AKs is 700 mV. When the power generation circuit charges the energy storage capacitor C to be higher than the undervoltage locking threshold voltage, the undervoltage protection circuit opens the pull-up module, the AK voltage stabilizing module and the pull-down module, so that the logic module can normally control the power MOSFET tube M to be turned on or turned off. In order to avoid overlarge voltage on the energy storage capacitor C, the power supply generation circuit is provided with clamp voltage protection, and the power supply voltage is stable during normal work.
And a second stage: in the stage of pulling up the grid electrode voltage of the power MOSFET, when the current starts to flow from the end A to the end K, because the power MOSFET is not started, the current flows from the end A to the end K through a parasitic diode of the power MOSFET, the voltage difference is 700mV, the logic module 4 closes the pull-down module 7 and the AK voltage stabilizing module 6, the pull-up module 5 is opened, the pull-up module 5 detects that 700mV voltage difference exists between AKs, the grid electrode voltage of the power MOSFET is pulled up to the power supply voltage immediately, the power MOSFET is opened, and the voltage difference between the AKs is the product of the conduction resistance and the conduction current of the power MOSFET.
And a third stage: in the stage of holding the grid voltage of the power MOSFET, the logic module 4 closes the AK voltage stabilizing module 6 and the pull-down module 7 to keep the grid voltage of the power MOSFET at a power voltage for a period of time, namely, the minimum opening time MIN _ ON, so as to avoid the problem that when the power MOSFET is suddenly opened, the AK voltage difference is suddenly changed from 700mV to the product of ON-resistance and ON-current, the produced ringing makes the AK voltage difference negative to trigger the pull-down module 7 to work, so that the power MOSFET is mistakenly closed, and after the minimum opening time is over, the logic module 4 opens the pull-down module 7 and the AK voltage stabilizing module 6.
A fourth stage: in an AK voltage holding stage, after the power MOSFET is turned on in the forward direction, as the on-current from the a terminal to the K terminal is decreased, the AK voltage difference is decreased, and when the AK voltage difference is decreased to a pre-pull-down threshold V2 of the AK voltage stabilizing module 6, the AK voltage stabilizing module starts to operate, as shown in fig. 4, the AK voltage stabilizing module 6 includes a first comparator AMP1, a second comparator AMP2, and a clamp voltage MOS transistor M1; the non-inverting input terminal of the first comparator AMP1 is connected to the inverting input terminal of the second comparator AMP2, the inverting input terminal of the first comparator AMP1 is connected to the non-inverting input terminal of the second comparator AMP2, the first comparator AMP1 and the second comparator AMP2 simultaneously detect a pulse voltage between the anode a and the cathode K of the synchronous rectifier diode, the first comparator AMP1 and the second comparator AMP2 output voltages to the drain and the source of the clamping MOS transistor M1, respectively, and the second comparator AMP2 also outputs a voltage to the gate G of the power MOSFET transistor; the gate of the clamping MOS transistor M1 receives the reference voltage VP. When the forward voltage difference between the anode A and the cathode K of the synchronous rectifier diode exceeds the threshold voltage V1 of the first comparator AMP1, the grid G of the power MOSFET is charged, and when the forward voltage difference between the anode A and the cathode K of the synchronous rectifier diode is smaller than the threshold voltage V2 of the second comparator AMP2, the grid G of the power MOSFET is discharged.
The fifth stage: in order to completely turn off the grid G of the power MOSFET, under the condition that the conduction current is continuously reduced, in order to keep the AK voltage difference unchanged, the grid G voltage of the power MOSFET is continuously reduced to the threshold voltage of the power MOSFET, at the moment, the conduction resistance of the power MOSFET is larger, under the balance of the AK voltage stabilizing module, the conduction current is extremely small, when the conduction current is close to zero, the AK voltage stabilizing module cannot stabilize the AK voltage, the voltage of the AK voltage is reduced to be below V1 and is close to a zero voltage state, at the moment, the pull-down module detects the state of the AK voltage, and the grid G voltage of the power MOSFET reaching the threshold voltage is quickly pulled to the A end potential to turn off the power MOSFET.
The method can effectively pre-turn off the grid voltage of the power MOSFET to be close to the threshold voltage when the current of the power MOSFET is close to zero, so that the AK voltage difference is clamped between V1 and V2, and the power MOSFET is completely turned off when the current of the power MOSFET is reduced to zero, thereby improving the accuracy and efficiency of turning off the power MOSFET. Meanwhile, when the power MOSFET is closed by the pull-down module, the grid voltage of the power MOSFET is reduced to be close to the threshold voltage, the delay of the pull-down module for closing the power MOSFET is reduced, and the purpose of rapidly closing the power MOSFET when the current of the power MOSFET is reduced to zero is achieved.
Example 2: a synchronous rectification control circuit for a synchronous rectification diode comprises a reference circuit 1, a power generation circuit 2, an under-voltage protection circuit 3, a logic module 4, an AK voltage stabilizing module 6, an up-pull module 5 and a down-pull module 7; the reference circuit 1 provides a reference voltage for the undervoltage protection circuit 3.
The power generation circuit 2 is used for converting the pulse voltage between the anode A and the cathode K of the synchronous rectifier diode into stable direct-current voltage to charge the energy storage capacitor C.
The undervoltage protection circuit 3 is used for detecting the positive voltage of the energy storage capacitor C and outputting a control signal to the logic module 4.
The logic module 4 receives the control signal output by the under-voltage protection circuit 3, and outputs the control logic signal to the AK voltage stabilization module 6, the pull-up module 5, and the pull-down module 7.
The AK voltage stabilizing module 6, the pull-up module 5 and the pull-down module 7 are all controlled by the control logic signal output by the logic module 4, respectively detect the pulse voltage between the anode a and the cathode K of the synchronous rectifier diode, output the voltage to the gate G of the power MOSFET tube, and feed back the voltage of the gate G of the power MOSFET tube to the logic module 4.
The AK voltage stabilizing module 6 comprises a first comparator AMP1, a second comparator AMP2 and a clamping MOS tube M1; the non-inverting input terminal of the first comparator AMP1 is connected with the inverting input terminal of the second comparator AMP2, the inverting input terminal of the first comparator AMP1 is connected with the non-inverting input terminal of the second comparator AMP2, the first comparator AMP1 and the second comparator AMP2 output voltages to the drain and the source of the clamp MOS transistor M1, respectively, and the second comparator AMP2 also outputs a voltage to the gate G of the power MOSFET; the gate of the clamp MOS transistor M1 receives a reference voltage.
The power supply generating circuit 2 comprises a diode I D1, a diode V D5, a fourth adjusting tube M4 and an error amplifier AMP 3; one input end of the error amplifier AMP3 is connected with the anode A of the synchronous rectifier diode through a second resistor R2, and is connected with the upper plate of the energy storage capacitor C through a first resistor R1; the other input end of the error amplifier AMP3 receives the second reference voltage signal, and the output end of the error amplifier AMP3 is connected with the grid electrode of the fourth adjusting tube M4 through the switching circuit 11; the drain terminal of the fourth adjusting tube M4 receives a pulse signal output by the synchronous rectifying diode through the diode I D1, the pulse signal charges the energy storage capacitor C through the fourth adjusting tube M4 and the diode I D5, when the charging voltage of the energy storage capacitor C reaches a set value, the error amplifier AMP3 outputs a signal to close the fourth adjusting tube M4, the pulse signal stops charging the energy storage capacitor C, when the voltage on the energy storage capacitor C is consumed by other circuit units to be lower than the set value, the error amplifier AMP3 outputs a signal to open the fourth adjusting tube M4, and the pulse signal charges the energy storage capacitor C.
Referring to fig. 9, 10 and 11, the power generating circuit of the present invention can convert the pulse voltage between AK into a stable dc voltage source. The basic principle is as follows: the circuit structure can continuously charge the energy storage capacitor, when the charging voltage of the energy storage capacitor reaches a set value, the error amplifier closes the adjusting tube to forbid charging, and when the voltage of the energy storage capacitor is consumed by other units in the synchronous rectification control circuit to be lower than the set value, the error amplifier opens the adjusting tube to recover the unidirectional conduction charging process. Therefore, a stable power supply voltage is obtained on the energy storage capacitor to supply power for other modules in the synchronous rectification control circuit. The power supply generating circuit provided by the invention can automatically generate a stable power supply voltage relative to the A end, so that the synchronous rectification control circuit does not need external power supply. The power generation circuit has low power consumption and can improve the system efficiency.
Referring to fig. 6, 7 and 8, simulation graphs show minimum turn-on time signals for controlling whether the AK voltage stabilizing module and the pull-down module are turned on or not, and the turn-on current passing through the power MOSFET, the source-drain voltage of the power MOSFET, the gate-source voltage of the power MOSFET.
Referring to fig. 7, the simulation diagram is a simulation diagram of the synchronous rectification control circuit when the power MOSFET is turned on. Before time t1, the power MOSFET M is in an off state, and at this stage, the pull-up module is turned off, the minimum on-time signal is high, and the AK voltage stabilizing module and the pull-down module are turned off. At time t1, current starts to flow from terminal a to terminal K, and since the power MOSFET M is not yet turned on, the current generates a voltage difference of 700mV between the source and drain through its parasitic diode, and the pull-up module is turned on, and detects this voltage difference, the power MOSFET M is turned on through the pull-up module. At time t2, the power MOSFET M is turned on, the differential pressure between the source and drain decreases to the product of the on-current and the on-resistance, and the pull-up module is turned off. And the time from t1 to t2 is the starting delay time of the control circuit. The logic module starts timing at the time t2, after timing t3-t2, the minimum on time signal changes from high to low, and in the timing stage, because the minimum on time signal keeps high, the AK voltage stabilizing module and the pull-down module keep closed, the problem that the source-drain voltage changes from 700mV to the product of the conducting current and the conducting resistance to generate ringing to cause the power MOSFET M to be turned off by mistake is avoided. During the period from t1 to t3, the on current is always in a reduced state, so the source drain voltage is always reduced after the time t 2. After time t3, that is, after the minimum on-time is timed out, the minimum on-time signal changes from high to low, the AK voltage stabilizing module and the pull-down module are turned on, and the pull-up module is turned off.
Referring to FIG. 8, this simulation showsThe waveform of the power MOSFET M in the closing stage is that before the time t4, the grid-source voltage of the power MOSFET M is kept high, the conduction current is in a reduced state, and therefore the source-drain voltage is in a reduced state. When the source-drain voltage is reduced to the threshold voltage V2 at which the AK voltage stabilizing module starts to work, the AK voltage stabilizing module starts to discharge to the gate of the power MOSFET tube M, because the AK voltage stabilizing module adopts two linear comparators, the smaller the source-drain voltage is, the larger the discharge current is, see FIG. 7, and when the gate-source voltage discharge is lower than the VP-V dischargethAt the time, that is, at the time t5 in fig. 11, M1 is turned from off to on, and at this time, both linear comparators operate to start adjusting the voltage between the AK source and the AK drain to clamp the voltage at a fixed voltage difference. Because the on-current is always reduced and is constant source-drain voltage, the grid-source voltage is in a reduced state so as to ensure that the on-resistance is increased. When the time t6 is reached, the conduction current is reduced to be close to zero, the AK voltage adjusting module cannot stabilize the AK voltage, the AK voltage is smaller than V2, the gate-source voltage reaches below the threshold voltage of the power MOSFET, and the power MOSFET is turned off. Between the time t6 and the time t7, the conduction current is reduced to zero, the source-drain voltage difference is reduced to zero, the pull-down module starts to work, and the grid voltage of the power MOSFET M is quickly pulled to the ground. After the logic module detects that the grid reaches the ground, the minimum opening time signal is reset to high level. Returning to the state before time t1, the operation of one cycle is completed.
While embodiments of the invention have been shown and described, it will be understood by those of ordinary skill in the art that: various changes, modifications, substitutions and alterations can be made to the embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims (6)

1. A synchronous rectifier diode comprises a synchronous rectifier control circuit, a power MOSFET tube (M) and an energy storage capacitor (C), and is characterized in that: the upper polar plate of the energy storage capacitor (C) is connected with the power output end of the synchronous rectification control circuit, the lower polar plate of the energy storage capacitor (C) is connected with the anode (A) of the synchronous rectification diode, and the source electrode, the drain electrode and the grid electrode of the power MOSFET are respectively connected with the anode (A) and the cathode (K) of the synchronous rectification diode and the signal output end of the synchronous rectification control circuit;
the synchronous rectification control circuit detects the voltage difference between two ends of a source electrode and a drain electrode of the power MOSFET tube (M), if the voltage difference is positive voltage, a signal is output to a grid electrode of the power MOSFET tube (M), the power MOSFET tube (M) is opened, if the voltage difference between two ends of the source electrode and the drain electrode of the power MOSFET tube (M) is zero or negative voltage, the signal is output to the grid electrode of the power MOSFET (M), and the power MOSFET tube (M) is closed;
the synchronous rectification control circuit comprises a reference circuit (1), a power supply generating circuit (2), an under-voltage protection circuit (3), a logic module (4), an anode of a synchronous rectification diode, a cathode voltage stabilizing module (6), a pull-up module (5) and a pull-down module (7); the reference circuit (1) provides reference voltage for the undervoltage protection circuit (3);
the power supply generating circuit (2) is used for converting pulse voltage between the anode (A) and the cathode (K) of the synchronous rectifier diode into stable direct-current voltage to charge the energy storage capacitor (C);
the under-voltage protection circuit (3) is used for detecting the positive voltage of the energy storage capacitor (C) and outputting a control signal to the logic module (4);
the logic module (4) receives a control signal output by the undervoltage protection circuit (3) and outputs the control logic signal to the anode and cathode voltage stabilizing module (6), the pull-up module (5) and the pull-down module (7) of the synchronous rectifier diode;
the anode and cathode voltage stabilizing module (6), the pull-up module (5) and the pull-down module (7) of the synchronous rectifier diode are controlled by a control logic signal output by the logic module (4), respectively detect pulse voltage between the anode (A) and the cathode (K) of the synchronous rectifier diode, output a signal to the grid (G) of the power MOSFET (M), and feed back the grid (G) voltage of the power MOSFET (M) to the logic module (4);
when the positive voltage of the energy storage capacitor (C) is charged to the undervoltage protection threshold voltage stage from 0V, the power supply generation circuit (2) charges the energy storage capacitor (C); when the positive voltage of the energy storage capacitor (C) is lower than the undervoltage protection threshold voltage, the logic module (4) outputs a control logic signal to close the anode of the synchronous rectifier diode, the cathode voltage stabilizing module (6), the pull-up module (5), the pull-down module (7) and the power MOSFET (metal oxide semiconductor field effect transistor);
when the voltage of the positive electrode of the energy storage capacitor (C) reaches the undervoltage locking threshold voltage, the undervoltage protection circuit (3) opens the pull-up module (5), the anode of the synchronous rectifier diode, the cathode voltage stabilizing module (6) and the pull-down module (7);
when the power MOSFET (M) is not started and current starts to flow from the anode to the cathode of the synchronous rectifier diode, the logic module (4) closes the pull-down module (7) and the anode and cathode voltage stabilizing module (6) of the synchronous rectifier diode, and opens the pull-up module (5); the pull-up module pulls up the grid (G) voltage of the power MOSFET (M) to the power supply voltage, and the power MOSFET (M) is opened;
when the turn-on time of the power MOSFET (M) reaches the minimum turn-on time, the logic module (4) turns on the pull-down module (7) and the anode and cathode voltage stabilizing module (6) of the synchronous rectifier diode.
2. A synchronous rectifier diode as claimed in claim 1, wherein: the anode and cathode voltage stabilizing module (6) of the synchronous rectifying diode comprises a first comparator (AMP1), a second comparator (AMP2) and a clamping voltage MOS tube (M1); a non-inverting input terminal of a first comparator (AMP1) is connected with an inverting input terminal of a second comparator (AMP2), an inverting input terminal of the first comparator (AMP1) is connected with a non-inverting input terminal of the second comparator (AMP2), the first comparator (AMP1) and the second comparator (AMP2) simultaneously detect a pulse voltage between an anode (A) and a cathode (K) of the synchronous rectifier diode, the first comparator (AMP1) and the second comparator (AMP2) output voltages to a drain and a source of the clamp MOS transistor (M1), respectively, and the second comparator (AMP2) also outputs a voltage to a gate (G) of the power MOSFET; the gate of the clamp MOS transistor (M1) receives a reference Voltage (VP).
3. A synchronous rectifier diode as claimed in claim 1, wherein: the power supply generation circuit (2) comprises a diode I (D1), a diode V (D5), a fourth adjusting tube (M4) and an error amplifier (AMP 3); one input end of the error amplifier (AMP3) is connected with the anode (A) of the synchronous rectifier diode through a second resistor (R2), and is connected with the upper plate of the energy storage capacitor (C) through a first resistor (R1); the other input end of the error amplifier (AMP3) receives a second reference voltage signal, and the output end of the error amplifier (AMP3) is connected with the grid electrode of the fourth adjusting tube (M4) through a switching circuit (11); the drain terminal of the fourth adjusting tube (M4) receives a pulse signal output by the synchronous rectifying diode through the diode I (D1), the pulse signal charges the energy storage capacitor (C) through the fourth adjusting tube (M4) and the diode V (D5), when the charging voltage of the energy storage capacitor (C) reaches a set value, the error amplifier (AMP3) outputs a signal to close the fourth adjusting tube (M4), the pulse signal stops charging the energy storage capacitor (C), when the voltage on the energy storage capacitor (C) is consumed by other circuit units to be lower than the set value, the error amplifier (AMP3) outputs a signal to open the fourth adjusting tube (M4), and the pulse signal charges the energy storage capacitor (C).
4. A synchronous rectification control circuit for a synchronous rectification diode comprises a reference circuit (1), a power generation circuit (2), an under-voltage protection circuit (3), a logic module (4), an anode and cathode voltage stabilizing module (6) of the synchronous rectification diode, a pull-up module (5) and a pull-down module (7); the reference circuit (1) provides reference voltage for the undervoltage protection circuit (3); the method is characterized in that:
the power supply generating circuit (2) is used for converting pulse voltage between the anode (A) and the cathode (K) of the synchronous rectifier diode into stable direct-current voltage to charge the energy storage capacitor (C);
the under-voltage protection circuit (3) is used for detecting the positive voltage of the energy storage capacitor (C) and outputting a control signal to the logic module (4);
the logic module (4) receives a control signal output by the undervoltage protection circuit (3) and outputs the control logic signal to the anode and cathode voltage stabilizing module (6), the pull-up module (5) and the pull-down module (7) of the synchronous rectifier diode;
the anode voltage stabilizing module (6), the cathode voltage stabilizing module (6), the pull-up module (5) and the pull-down module (7) of the synchronous rectifier diode are controlled by control logic signals output by the logic module (4), pulse voltages between the anode (A) and the cathode (K) of the synchronous rectifier diode are respectively detected, voltages are output to a grid (G) of a power MOSFET, and the voltage of the grid (G) of the power MOSFET is fed back to the logic module (4);
when the positive voltage of the energy storage capacitor (C) is charged to the undervoltage protection threshold voltage stage from 0V, the power supply generation circuit (2) charges the energy storage capacitor (C); when the positive voltage of the energy storage capacitor (C) is lower than the undervoltage protection threshold voltage, the logic module (4) outputs a control logic signal to close the anode of the synchronous rectifier diode, the cathode voltage stabilizing module (6), the pull-up module (5), the pull-down module (7) and the power MOSFET (metal oxide semiconductor field effect transistor); when the voltage of the positive electrode of the energy storage capacitor (C) reaches the undervoltage locking threshold voltage, the undervoltage protection circuit (3) opens the pull-up module (5), the anode of the synchronous rectifier diode, the cathode voltage stabilizing module (6) and the pull-down module (7);
when the power MOSFET (M) is not started and current starts to flow from the anode to the cathode of the synchronous rectifier diode, the logic module (4) closes the pull-down module (7) and the anode and cathode voltage stabilizing module (6) of the synchronous rectifier diode, and opens the pull-up module (5); the pull-up module pulls up the grid (G) voltage of the power MOSFET (M) to the power supply voltage, and the power MOSFET (M) is opened;
when the turn-on time of the power MOSFET (M) reaches the minimum turn-on time, the logic module (4) turns on the pull-down module (7) and the anode and cathode voltage stabilizing module (6) of the synchronous rectifier diode.
5. The synchronous rectification control circuit for the synchronous rectification diode according to claim 4, wherein: the anode and cathode voltage stabilizing module (6) of the synchronous rectifying diode comprises a first comparator (AMP1), a second comparator (AMP2) and a clamping voltage MOS tube (M1); the non-inverting input end of the first comparator (AMP1) is connected with the inverting input end of the second comparator (AMP2), the inverting input end of the first comparator (AMP1) is connected with the non-inverting input end of the second comparator (AMP2), the first comparator (AMP1) and the second comparator (AMP2) output voltages to the drain electrode and the source electrode of the clamping voltage MOS tube (M1) respectively, and the second comparator (AMP2) also outputs a voltage to the grid electrode (G) of the power MOSFET tube; the grid of the clamping MOS tube (M1) receives a reference voltage.
6. The synchronous rectification control circuit for the synchronous rectification diode according to claim 4, wherein: the power supply generation circuit (2) comprises a diode I (D1), a diode V (D5), a fourth adjusting tube (M4) and an error amplifier (AMP 3); one input end of the error amplifier (AMP3) is connected with the anode (A) of the synchronous rectifier diode through a second resistor (R2), and is connected with the upper plate of the energy storage capacitor (C) through a first resistor (R1); the other input end of the error amplifier (AMP3) receives a second reference voltage signal, and the output end of the error amplifier (AMP3) is connected with the grid electrode of the fourth adjusting tube (M4) through a switching circuit (11); the drain terminal of the fourth adjusting tube (M4) receives a pulse signal output by the synchronous rectifying diode through the diode I (D1), the pulse signal charges the energy storage capacitor (C) through the fourth adjusting tube (M4) and the diode V (D5), when the charging voltage of the energy storage capacitor (C) reaches a set value, the error amplifier (AMP3) outputs a signal to close the fourth adjusting tube (M4), the pulse signal stops charging the energy storage capacitor (C), when the voltage on the energy storage capacitor (C) is consumed by other circuit units to be lower than the set value, the error amplifier (AMP3) outputs a signal to open the fourth adjusting tube (M4), and the pulse signal charges the energy storage capacitor (C).
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