Secondary side synchronous rectification chip and switching power supply

Abstract

The invention discloses a secondary side synchronous rectification chip and a switching power supply, and relates to the field of switching power supplies, and the chip comprises a rectification control module and a driving module. The driving module is connected with the rectification control module, the rectification control module is connected with the secondary side of the switching power supply, and the driving module is connected with a rectifier tube of the secondary side of the switching power supply; the rectification control module is used for receiving the output voltage of the secondary side of the switching power supply and sending a starting signal to the driving module when the output voltage is greater than a preset starting voltage; the driving module is used for driving a rectifier tube on the secondary side of the switching power supply to be turned on when receiving the turn-on signal so as to enable the secondary side of the switching power supply to output; the rectification control module is used for receiving the output voltage of the secondary side of the switching power supply and sending a turn-off signal to the driving module when the output voltage is smaller than a preset turn-on voltage; and the driving module is used for driving the rectifier tube of the switching power supply secondary side to be switched off when receiving the switching-off signal so as to stop the output of the switching power supply secondary side, thereby realizing the output rectification of the switching power supply secondary side.

Description

Technical Field

[0001] This application relates to the technical field of switched-mode power supplies, and particularly to a secondary-side synchronous rectification chip and a switched-mode power supply. Background Art

[0002] In a traditional switched-mode power supply, a Schottky diode is used at the output terminal (secondary side) to rectify the output voltage. However, in the case of high current, the power consumption of the diode may become very large. For example, when the diode voltage drop is 0.7V and the current is 10A, the power consumption is as high as 7W.

[0003] Secondly, switched-mode power supplies usually need to operate at high frequencies to achieve fast response and efficient energy conversion. Due to its physical characteristics and operating principle, the diode may exhibit large switching losses and high noise at high frequencies. Therefore, there are problems of low rectification efficiency and high power consumption in the secondary-side rectification of switched-mode power supplies in the prior art. Summary of the Invention

[0004] The main purpose of this application is to provide a secondary-side synchronous rectification chip and a switched-mode power supply, aiming to solve the technical problems of low rectification efficiency and high power consumption in the secondary side of the switched-mode power supply in the prior art.

[0005] To achieve the above object, this application proposes a secondary-side synchronous rectification chip. The secondary-side synchronous rectification chip is applied to a switched-mode power supply, and the secondary-side synchronous rectification chip includes: a rectification control module and a driving module; The driving module is connected to the rectification control module, the rectification control module is connected to the secondary side of the switched-mode power supply, and the driving module is used to connect the rectification tube on the secondary side of the switched-mode power supply; The rectification control module is configured to receive the output voltage of the secondary side of the switched-mode power supply and send an enabling signal to the driving module when the output voltage is greater than a preset enabling voltage; The driving module is configured to drive the rectification tube on the secondary side of the switched-mode power supply to turn on when receiving the enabling signal so that the secondary side of the switched-mode power supply outputs; The rectification control module is configured to receive the output voltage of the secondary side of the switched-mode power supply and send a shutdown signal to the driving module when the output voltage is less than the preset enabling voltage; The driving module is configured to drive the rectification tube on the secondary side of the switched-mode power supply to turn off when receiving the shutdown signal so that the secondary side of the switched-mode power supply stops outputting.

[0006] Optionally, the secondary-side synchronous rectification chip further includes: a power generation module; The power generation module is respectively connected to the rectification control module; The power generation module is configured to supply power to the rectification control module when receiving the output voltage of the secondary side of the switched-mode power supply.

[0007] Optionally, the secondary side synchronous rectification chip further includes: a secondary side discontinuous evaluation module; The secondary side discontinuous evaluation module is respectively connected to the rectification control module and the driving module; The secondary side discontinuous evaluation module is configured to send a discontinuous signal to the rectification control module when it detects that the secondary side of the switching power supply is in a discontinuous state; The rectification control module is further configured to send an adjustment signal to the driving module when it receives the discontinuous signal; The driving module is further configured to adjust the switching state of the rectifying tube when it receives the adjustment signal.

[0008] Optionally, the rectification control module includes: a synchronous rectification turn-off module and a synchronous rectification turn-on module; The synchronous rectification turn-on module is respectively connected to the synchronous rectification turn-off module and the driving module, and the synchronous rectification turn-off module is connected to the driving module; The synchronous rectification turn-on module is configured to receive the output voltage of the secondary side of the switching power supply and send an on signal to the driving module when the output voltage is greater than a preset turn-on voltage; The driving module is further configured to drive the rectifying tube on the secondary side of the switching power supply to turn on so that the secondary side of the switching power supply outputs when it receives the on signal; The synchronous rectification turn-off module is configured to receive the output voltage of the secondary side of the switching power supply and send an off signal to the driving module when the output voltage is less than the preset turn-on voltage; The driving module is further configured to drive the rectifying tube on the secondary side of the switching power supply to turn off so that the secondary side of the switching power supply stops outputting when it receives the off signal.

[0009] Optionally, the driving module includes: a control unit and a driving unit; The control unit is respectively connected to the driving unit and the rectification control module, and the rectification control module is connected to the driving unit; The control unit is configured to send a first control signal to the driving unit when it receives the on signal; The driving unit is configured to send a first voltage signal to the rectifying tube on the secondary side of the switching power supply so that the secondary side of the switching power supply outputs when it receives the first control signal; The control unit is further configured to send a second control signal to the driving unit when it receives the off signal; The driving unit is further configured to send a second voltage signal to the rectifying tube on the secondary side of the switching power supply so that the output of the secondary side of the switching power supply is turned off when it receives the second control signal.

[0010] Optionally, the rectification control module is further configured to detect the output voltage of the secondary side of the switching power supply when the primary chip of the switching power supply is turned off; The rectification control module is further configured to determine that the rectifier diode is in an on state when detecting that the output voltage of the secondary side of the switching power supply decreases.

[0011] Optionally, the rectification control module is further configured to set a preset turn-off time when the rectifier diode is in an on state; The rectification control module is further configured to send an on signal to the drive module to ensure that the rectifier diode is in an on state during the preset turn-off time.

[0012] In addition, to achieve the above object, the present application further provides a power supply system, and the power supply system includes the output fast turn-off circuit as described above.

[0013] One or more technical solutions proposed by the present application have at least the following effects: The present application provides a secondary-side synchronous rectification chip and a switching power supply. The secondary-side synchronous rectification chip is applied to the switching power supply. The secondary-side synchronous rectification chip includes a rectification control module and a drive module; the drive module is connected to the rectification control module, the rectification control module is connected to the secondary side of the switching power supply, and the drive module is used to connect the rectifier diode on the secondary side of the switching power supply; the rectification control module is configured to receive the output voltage of the secondary side of the switching power supply and send an on signal to the drive module when the output voltage is greater than a preset on voltage; the drive module is configured to drive the rectifier diode on the secondary side of the switching power supply to turn on when receiving the on signal so that the secondary side of the switching power supply outputs; the rectification control module is configured to receive the output voltage of the secondary side of the switching power supply and send a turn-off signal to the drive module when the output voltage is less than the preset on voltage; the drive module is configured to drive the rectifier diode on the secondary side of the switching power supply to turn off when receiving the turn-off signal so that the secondary side of the switching power supply stops outputting, thereby realizing efficient synchronous rectification of the output voltage of the secondary side of the switching power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative efforts.

[0015] Figure 1 It is a schematic structural diagram of the first embodiment of the secondary-side synchronous rectification chip proposed by the embodiment of the present application; Figure 2 It is a schematic structural diagram of the second embodiment of the secondary-side synchronous rectification chip proposed by the embodiment of the present application; Figure 3 This is the circuit schematic diagram of the first embodiment of the secondary synchronous rectification chip proposed in the embodiments of the present application.

[0016] Description of the reference numerals in the drawings:

[0017] The realization of the purpose, functional characteristics and advantages of the present application will be further described in conjunction with the embodiments with reference to the accompanying drawings. Specific embodiments

[0018] It should be understood that the specific embodiments described herein are only used to explain the technical solutions of the present application and are not used to limit the present application.

[0019] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0020] It should be noted that all directional indications (such as up, down, left, right, front, back...) in the embodiments of the present application are only used to explain the relative positional relationship and movement conditions between components in a specific posture (as shown in the drawings). If the specific posture changes, the directional indications will also change accordingly.

[0021] In addition, the descriptions involving "first", "second", etc. in the present application are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the fact that those of ordinary skill in the art can implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present application.

[0022] The main solution of the embodiments of the present application is: by precisely controlling the on and off of the rectifying diode Q in the secondary circuit of the switching power supply, the high-efficiency synchronous rectification of the output voltage of the secondary circuit of the switching power supply is realized.

[0023] In the output terminal (secondary side) of a traditional switching power supply, a Schottky diode is used to rectify the output voltage. However, in the case of high current, the power consumption of the diode may become very large. For example, when the diode voltage drop is 0.7V and the current is 10A, the power consumption is as high as 7W. In contrast, the voltage drop (i.e., on-state voltage drop) of a MOS transistor when it is fully turned on is usually much smaller than that of a diode. Therefore, using a MOS transistor to replace the diode can significantly reduce power loss. Secondly, a switching power supply usually needs to operate at high frequencies to achieve fast response and efficient energy conversion. Due to its physical characteristics and operating principle, a diode may exhibit large switching losses and high noise at high frequencies, while a MOS transistor has a faster switching speed and lower switching losses and is more suitable for operating at high frequencies. In the design of a switching power supply, adopting synchronous rectification technology can further improve efficiency. The synchronous rectification technology uses two MOS transistors (one as a switch and the other as a freewheeling device) to replace the traditional diode rectifier. This way can ensure that during the turn-off period of the switching transistor, the freewheeling MOS transistor can be turned on in time, thereby reducing the power loss during the rectification process.

[0024] This application proposes a secondary-side synchronous rectification chip and a switching power supply. The secondary-side synchronous rectification chip is applied to the switching power supply. The secondary-side synchronous rectification chip includes: a rectification control module 1 and a drive module 2; the drive module 2 is connected to the rectification control module 1, the rectification control module 1 is connected to the secondary side of the switching power supply, and the drive module 2 is used to connect the rectifier diode Q on the secondary side of the switching power supply; the rectification control module 1 is configured to receive the output voltage of the secondary side of the switching power supply and send an enabling signal to the drive module 2 when the output voltage is greater than a preset enabling voltage; the drive module 2 is configured to drive the rectifier diode Q on the secondary side of the switching power supply to turn on when receiving the enabling signal so that the secondary side of the switching power supply outputs; the rectification control module 1 is configured to receive the output voltage of the secondary side of the switching power supply and send a turn-off signal to the drive module 2 when the output voltage is less than the preset enabling voltage; the drive module 2 is configured to drive the rectifier diode Q on the secondary side of the switching power supply to turn off when receiving the turn-off signal so that the secondary side of the switching power supply stops outputting, thereby realizing efficient synchronous rectification of the output voltage of the secondary side of the switching power supply.

[0025] It should be noted that when the flyback switching power supply operates in DCM (Discontinuous Conduction Mode), CCM (Continuous Conduction Mode), or QR (flyback quasi-resonant mode, which is also a type of DCM), due to the excitation of the inductor, when the primary chip (the chip that controls the output of the primary side of the switching voltage) is turned off, oscillations will occur. To prevent misdetection of the oscillation signal and cause abnormal turn-on of the rectifier diode Q, the secondary side synchronous rectification chip of this application adopts the primary side turn-on determination and secondary side discontinuous determination technologies, which can effectively avoid misoperation of the drive chip caused by excitation oscillation. When the primary chip of the switching power supply is turned on, a flyback voltage is generated between the output of the secondary side of the switching power supply and the secondary side synchronous rectification chip through the transformer; when the primary chip is turned off, the voltage between the drain of the secondary side and the ground drops. By detecting the voltage drop at the drain of the rectifier diode Q, the turn-on of the rectifier diode Q can be accurately judged, and by detecting the secondary side current or related voltage parameters, it can be accurately judged whether the secondary side is in a discontinuous state.

[0026] Based on this, an embodiment of this application provides a secondary side synchronous rectification chip.

[0027] Refer to Figure 1 , Figure 1 which is a schematic structural diagram of the first embodiment of the secondary side synchronous rectification chip proposed in the embodiment of this application.

[0028] Considering that the input voltage of the switching power supply is an alternating voltage, and in order to perform efficient synchronous rectification on the output voltage of the secondary side of the switching power supply, as Figure 1 shown, the secondary side synchronous rectification chip described in this embodiment is applied to the switching power supply, and the secondary side synchronous rectification chip includes: a rectification control module 1 and a drive module 2; The drive module 2 is connected to the rectification control module 1, the rectification control module 1 is connected to the secondary side of the switching power supply, and the drive module 2 is used to connect the rectifier diode Q on the secondary side of the switching power supply; The rectification control module 1 is used to receive the output voltage of the secondary side of the switching power supply and send an on signal to the drive module 2 when the output voltage is greater than a preset turn-on voltage; The drive module 2 is used to drive the rectifier diode Q on the secondary side of the switching power supply to turn on when receiving the on signal so that the secondary side of the switching power supply outputs; The rectification control module 1 is used to receive the output voltage of the secondary side of the switching power supply and send an off signal to the drive module 2 when the output voltage is less than a preset turn-on voltage; The drive module 2 is used to drive the rectifier diode Q on the secondary side of the switching power supply to turn off when receiving the off signal so that the secondary side of the switching power supply stops outputting.

[0029] It should be noted that the switching power supply in this embodiment is a flyback switching power supply. "Flyback" refers to the way of energy storage and release in the transformer during the on and off processes of the switching tube. Specifically, when the switching tube is on, the input power supply charges the primary coil of the transformer, and at this time, the inductor in the output circuit is in a discharging state; when the switching tube is off, the energy stored in the primary coil of the transformer is released to the load through the secondary coil, and at this time, the inductor in the output circuit is in a charging state. A switching power supply generally consists of an electronic switching device such as a pulse width modulation (PWM) control chip and a MOSFET. By controlling the primary circuit, the electronic switching device is continuously turned on and off to perform PWM modulation on the input voltage, thereby realizing voltage conversion and stable voltage regulation. The secondary side of the switching power supply refers to the secondary side of the transformer in the switching power supply. The rectifying diode Q can be an NMOS transistor, a PMOS transistor, or can be set according to actual situations. The turn-on signal and the turn-off signal can be voltage signals, current signals, or can be set according to actual situations, and this embodiment does not impose any restrictions.

[0030] It can be understood that, as Figure 3 shown, Figure 3 is the circuit schematic diagram of the first embodiment of the secondary synchronous rectification chip proposed in the embodiment of the present application. The preset turn-on voltage is the startup voltage of the secondary synchronous rectification chip. For example, the startup voltage range can be 2.8V to 3.6V. When the system (switching power supply) is powered on, the body diode of the externally driven MOS tube conducts, and the output capacitor starts to charge, and the output voltage rises. When the output voltage rises to the preset turn-on voltage, the internal control circuit of chip U starts to work, controlling the normal on and off of the MOS tube to achieve synchronous rectification of the output voltage. When the MOS tube is normally on, the current no longer flows through the body diode but through the channel of the MOS tube.

[0031] In specific implementation, the rectification control module 1 is used to receive the output voltage of the secondary side of the switching power supply and send a turn-on signal to the drive module 2 when the output voltage is greater than the preset turn-on voltage; the drive module 2 is used to drive the rectifying diode Q of the secondary side of the switching power supply to turn on to enable the secondary side of the switching power supply to output when receiving the turn-on signal; the rectification control module 1 is used to receive the output voltage of the secondary side of the switching power supply and send a turn-off signal to the drive module 2 when the output voltage is less than the preset turn-on voltage; the drive module 2 is used to drive the rectifying diode Q of the secondary side of the switching power supply to turn off to stop the output of the secondary side of the switching power supply when receiving the turn-off signal, thereby realizing high-efficiency synchronous rectification of the output voltage of the secondary side of the switching power supply.

[0032] It should be noted that, as Figure 3As shown, the rectifier diode Q is a MOS transistor. The pins of the secondary synchronous rectification chip include a linear voltage regulation output terminal Vcc, a ground terminal Gnd, a drain voltage detection terminal Vd of the power transistor, and a gate drive output terminal Gate. The reference range of Vcc is -0.3V to 12V, the reference value of Vd is 120V, the turn-on voltage (preset turn-on voltage) range of Vcc is 2.8V to 3.6V, the turn-on voltage range of the rectification control module 1 is -0.4V to 0V, the reference value of the drive-off threshold of the rectification control module 1 is -5V, the reference value of the high-level output of the gate drive output terminal Gate is 7V, and the reference value of the low-level output of the gate drive output terminal Gate is 0.15V.

[0033] It can be understood that Figure 3 the circuit in

[0034] is the secondary rectification circuit when the same-name terminal (black dot) of the transformer in the switching power supply is at a high level, that is, the high-side rectification circuit. The secondary synchronous rectification chip in this application can also be applied to the low-side rectification circuit. The power generation module 3 is respectively connected to the rectification control module 1; The power generation module 3 is used to supply power to the rectification control module 1 when receiving the output voltage of the secondary side of the switching power supply.

[0035] In a specific implementation, when the system (switching power supply) is powered on, the body diode of the externally driven MOS transistor conducts, the output capacitor starts to charge, the output voltage rises, and the power generation module 3 is powered by the drain voltage detection terminal Vd of the power transistor.

[0036] Furthermore, considering that in the discontinuous mode of the switching power supply, the secondary current has a zero-current state during the conduction period. Therefore, in order to determine whether the secondary side is in a discontinuous state through the secondary discontinuous determination technology, the secondary synchronous rectification chip further includes: a secondary discontinuous evaluation module 4; The secondary discontinuous evaluation module 4 is respectively connected to the rectification control module 1 and the drive module 2; The secondary discontinuous evaluation module 4 is used to send a discontinuous signal to the rectification control module 1 when detecting that the secondary side of the switching power supply is in a discontinuous state; The rectification control module 1 is further used to send an adjustment signal to the drive module 2 when receiving the discontinuous signal; The drive module 2 is further used to adjust the switching state of the rectifier diode Q when receiving the adjustment signal.

[0037] It should be noted that the discontinuous state refers to the state where the current in the secondary side is zero during the conduction period of the rectifier diode Q. The secondary side discontinuous determination technology can accurately determine whether the secondary side is in a discontinuous state by monitoring the secondary side current or related voltage parameters. When it is detected that the secondary side is in a discontinuous state, the switching state of the switching tube can be adjusted in a timely manner, thereby avoiding misoperations caused by interference factors such as excitation oscillation.

[0038] It can be understood that the discontinuous signal can be a voltage signal, a current signal, or can be set according to the actual situation, and the adjustment signal is a voltage signal.

[0039] In a specific implementation, the secondary side discontinuous evaluation module 4 is configured to send a discontinuous signal to the rectification control module 1 when it is detected that the secondary side of the switching power supply is in a discontinuous state; the rectification control module 1 is further configured to send an adjustment signal to the drive module 2 when receiving the discontinuous signal; the drive module 2 is further configured to adjust the switching state of the rectifier diode Q when receiving the adjustment signal, thereby avoiding misoperations caused by interference factors such as excitation oscillation.

[0040] Based on the first embodiment of the present application, in the second embodiment of the present application, the same or similar content as the above first embodiment can be referred to the above introduction and will not be repeated hereinafter. On this basis, please refer to Figure 2 , Figure 2 which is a schematic structural diagram of the second embodiment of the secondary side synchronous rectification chip proposed in the embodiment of the present application.

[0041] Considering synchronous rectification of the output voltage of the secondary side of the switching power supply, as Figure 2 shown, the rectification control module 1 includes: a synchronous rectification turn-off module 12 and a synchronous rectification turn-on module 11; The synchronous rectification turn-on module 11 is respectively connected to the synchronous rectification turn-off module 12 and the drive module 2, and the synchronous rectification turn-off module 12 is connected to the drive module 2; The synchronous rectification turn-on module 11 is configured to receive the output voltage of the secondary side of the switching power supply and send an on signal to the drive module 2 when the output voltage is greater than a preset turn-on voltage; The drive module 2 is further configured to drive the rectifier diode Q of the secondary side of the switching power supply to turn on to enable the secondary side of the switching power supply to output when receiving the on signal; The synchronous rectification turn-off module 12 is configured to receive the output voltage of the secondary side of the switching power supply and send an off signal to the drive module 2 when the output voltage is less than the preset turn-on voltage; The drive module 2 is further configured to drive the rectifier diode Q of the secondary side of the switching power supply to turn off to stop the output of the secondary side of the switching power supply when receiving the off signal.

[0042] It should be noted that the synchronous rectification technology uses two MOS transistors (one as a switch to control the primary output of the switching power supply, and the other as a freewheeling (rectifying) device to control the secondary output of the switching power supply), which can ensure that during the turn-off period of the switching transistor, the freewheeling (rectifying) MOS transistor can be turned on in time, thereby reducing the power loss during the rectification process.

[0043] In a specific implementation, the synchronous rectification enabling module 11 is configured to receive the output voltage of the secondary side of the switching power supply and send an enabling signal to the driving module 2 when the output voltage is greater than a preset enabling voltage; the driving module 2 is further configured to drive the rectifying diode Q on the secondary side of the switching power supply to turn on when receiving the enabling signal so that the secondary side of the switching power supply outputs; the synchronous rectification turning-off module 12 is configured to receive the output voltage of the secondary side of the switching power supply and send a turning-off signal to the driving module 2 when the output voltage is less than the preset enabling voltage; the driving module 2 is further configured to drive the rectifying diode Q on the secondary side of the switching power supply to turn off when receiving the turning-off signal so that the secondary side of the switching power supply stops outputting, thereby realizing efficient synchronous rectification of the output voltage of the secondary side of the switching power supply.

[0044] Furthermore, considering driving the rectifying diode Q, and further to control the on-off of the rectifying diode Q, the driving module 2 includes: a control unit 21 and a driving unit 22; The control unit 21 is respectively connected to the driving unit 22 and the rectification control module 1, and the rectification control module 1 is connected to the driving unit 22; The control unit 21 is configured to send a first control signal to the driving unit 22 when receiving the enabling signal; The driving unit 22 is configured to send a first voltage signal to the rectifying diode Q on the secondary side of the switching power supply to enable the secondary side of the switching power supply to output when receiving the first control signal; The control unit 21 is further configured to send a second control signal to the driving unit 22 when receiving the turning-off signal; The driving unit 22 is further configured to send a second voltage signal to the rectifying diode Q on the secondary side of the switching power supply to turn off the output of the secondary side of the switching power supply when receiving the second control signal.

[0045] It should be noted that the first control signal and the second control signal can be voltage signals, current signals, or can be set according to actual situations.

[0046] In a specific implementation, the control unit 21 is configured to send a first control signal to the driving unit 22 when receiving an enabling signal; the driving unit 22 is configured to send a first voltage signal to the rectifying diode Q on the secondary side of the switching power supply when receiving the first control signal, so that the secondary side of the switching power supply outputs; the control unit 21 is further configured to send a second control signal to the driving unit 22 when receiving a disabling signal; the driving unit 22 is further configured to send a second voltage signal to the rectifying diode Q on the secondary side of the switching power supply when receiving the second control signal, so that the output of the secondary side of the switching power supply is turned off, thereby realizing highly efficient synchronous rectification of the output voltage of the secondary side of the switching power supply.

[0047] Further, considering the magnetizing effect of the inductor, when the primary chip is turned off, oscillations will occur. Further, in order to prevent misdetection of the oscillation signal, resulting in abnormal turn-on of the rectifying diode Q. The rectification control module 1 is further configured to detect the output voltage of the secondary side of the switching power supply when the primary chip of the switching power supply is turned off; The rectification control module 1 is further configured to determine that the rectifying diode Q is in an on state when detecting that the output voltage of the secondary side of the switching power supply decreases, thereby avoiding misoperation caused by interference factors such as magnetizing oscillation.

[0048] It should be noted that the secondary-side discontinuous determination technique can accurately determine whether the secondary side is in a discontinuous state by detecting the secondary-side current or related voltage parameters.

[0049] In a specific implementation, the rectification control module 1 is further configured to detect the output voltage of the secondary side of the switching power supply when the primary chip of the switching power supply is turned off; the rectification control module 1 is further configured to determine that the rectifying diode Q is in an on state when detecting that the output voltage of the secondary side of the switching power supply decreases, thereby preventing abnormal turn-on of the rectifying diode Q caused by misdetection of the oscillation signal.

[0050] Further, considering that in order to avoid misdetection of the turn-off signal due to a large magnetizing oscillation amplitude when the synchronous rectifying diode Q is turned on, resulting in abnormal turn-off of the rectifying diode Q. The rectification control module 1 is further configured to set a preset turn-off time when the rectifying diode Q is in an on state; The rectification control module 1 is further configured to send an enabling signal to the driving module 2 to ensure that the rectifying diode Q is in an on state when within the preset turn-off time.

[0051] It should be noted that the preset turn-off time can be set according to actual conditions, for example, 1 us.

[0052] In a specific implementation, the rectification control module 1 is further configured to set a preset turn-off time when the rectifying diode Q is in an on state; the rectification control module 1 is further configured to send an enabling signal to the driving module 2 to ensure that the rectifying diode Q is in an on state when within the preset turn-off time, thereby ensuring reliable operation of the synchronous rectification.

[0053] To achieve the above object, the present application further provides a switching power supply, and the switching power supply includes the secondary side synchronous rectification chip as described above.

[0054] The above are only the preferred embodiments of the present application, and do not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present application, or directly or indirectly applied to other related technical fields, shall be equally included in the patent protection scope of the present application.

Claims

1. A secondary side synchronous rectification chip, characterized in that The secondary side synchronous rectification chip is applied to a switching power supply. The secondary side synchronous rectification chip includes: a rectification control module and a driving module; The driving module is connected to the rectification control module. The rectification control module is connected to the secondary side of the switching power supply. The driving module is used to connect to the rectifier tube on the secondary side of the switching power supply; The rectification control module is used to receive the output voltage of the secondary side of the switching power supply and send an enabling signal to the driving module when the output voltage is greater than a preset enabling voltage; The driving module is used to drive the rectifier tube on the secondary side of the switching power supply to turn on when receiving the enabling signal so that the secondary side of the switching power supply outputs; The rectification control module is used to receive the output voltage of the secondary side of the switching power supply and send a shutdown signal to the driving module when the output voltage is less than the preset enabling voltage; The driving module is used to drive the rectifier tube on the secondary side of the switching power supply to turn off when receiving the shutdown signal so that the secondary side of the switching power supply stops outputting.

2. The secondary side synchronous rectification chip according to claim 1, wherein The secondary side synchronous rectification chip further includes: a power generation module; The power generation module is respectively connected to the rectification control module; The power generation module is used to supply power to the rectification control module when receiving the output voltage of the secondary side of the switching power supply.

3. The secondary side synchronous rectification chip according to claim 1, wherein The secondary side synchronous rectification chip further includes: a secondary side discontinuous evaluation module; The secondary side discontinuous evaluation module is respectively connected to the rectification control module and the driving module; The secondary side discontinuous evaluation module is used to send a discontinuous signal to the rectification control module when detecting that the secondary side of the switching power supply is in a discontinuous state; The rectification control module is further used to send an adjustment signal to the driving module when receiving the discontinuous signal; The driving module is further used to adjust the switching state of the rectifier tube when receiving the adjustment signal.

4. The secondary side synchronous rectification chip according to claim 1, wherein The rectification control module includes: a synchronous rectification shutdown module and a synchronous rectification startup module; The synchronous rectification startup module is respectively connected to the synchronous rectification shutdown module and the driving module. The synchronous rectification shutdown module is connected to the driving module; The synchronous rectification startup module is used to receive the output voltage of the secondary side of the switching power supply and send an enabling signal to the driving module when the output voltage is greater than the preset enabling voltage; The driving module is further used to drive the rectifier tube on the secondary side of the switching power supply to turn on when receiving the enabling signal so that the secondary side of the switching power supply outputs; The synchronous rectification shutdown module is used to receive the output voltage of the secondary side of the switching power supply and send a shutdown signal to the driving module when the output voltage is less than the preset enabling voltage; The driving module is further used to drive the rectifier tube on the secondary side of the switching power supply to turn off when receiving the shutdown signal so that the secondary side of the switching power supply stops outputting.

5. The secondary side synchronous rectification chip according to claim 1, characterized in that The driving module includes: a control unit and a driving unit; The control unit is respectively connected to the driving unit and the rectification control module. The rectification control module is connected to the driving unit; The control unit is used to send a first control signal to the driving unit when receiving the enabling signal; The driving unit is used to send a first voltage signal to the rectifier tube on the secondary side of the switching power supply when receiving the first control signal so that the secondary side of the switching power supply outputs; The control unit is further configured to send a second control signal to the driving unit when receiving a turn-off signal; The driving unit is further configured to send a second voltage signal to the rectifying diode on the secondary side of the switching power supply to turn off the output of the secondary side of the switching power supply when receiving the second control signal.

6. The secondary-side synchronous rectification chip according to claim 1, wherein The rectification control module is further configured to detect the output voltage of the secondary side of the switching power supply when the primary chip of the switching power supply is turned off; The rectification control module is further configured to determine that the rectifying diode is in an on state when detecting that the output voltage of the secondary side of the switching power supply decreases; 7. The secondary side synchronous rectification chip according to claim 1, wherein The rectification control module is further configured to set a preset turn-off time when the rectifying diode is in an on state; The rectification control module is further configured to send an on signal to the driving module to ensure that the rectifying diode is in an on state within the preset turn-off time.

8. A switching power supply, characterized in that, The switching power supply includes the secondary side synchronous rectification chip according to any one of claims 1 to 7.

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