Backward flow prevention method for power converter and power converter

Abstract

The embodiment of the invention provides an anti-backflow method for a power converter and the power converter, and the method comprises the steps: turning off a secondary side metal semiconductor oxide field effect MOS tube drive signal of the power converter for at least a first preset time under the condition that the transient drop of the input voltage of the power converter is detected; and when it is detected that the input voltage recovers to the normal working voltage, the secondary side MOS tube driving signal is turned on again. According to the invention, the problems that the voltage stress of the synchronous rectifier tube of the power converter exceeds the standard and the synchronous rectifier tube is in avalanche failure due to the fact that the reverse backward current is too large in the input transient drop process of the power converter adopting synchronous rectification are solved; moreover, no extra hardware circuit needs to be added, so that the layout area and the cost of the whole hardware circuit are reduced, and the efficiency and the overall power density of the power converter are also improved.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of communications, and in particular to a method for preventing backflow of a power converter and a power converter. Background Art

[0002] In power converters, bidirectional conducting devices with low on-resistance such as metal-oxide-semiconductor field-effect transistors (MOSFETs) are used to replace diodes to complete the synchronous rectification function, thereby improving the conversion efficiency of power converters. However, since MOSFETs are bidirectional conducting devices, compared to diode rectification, when MOSFETs are used to achieve synchronous rectification, the current in the rectification circuit can flow in both directions.

[0003] When the input voltage of a power converter using synchronous rectification drops transiently, the output energy will flow back to the primary input due to loop response delay and duty cycle limitation. The negative current that flows back will lose its freewheeling path at the moment the synchronous rectifier is turned off. If the negative current is too large, the voltage stress of the synchronous rectifier will be too high, causing avalanche failure, and thus damaging the power converter.

[0004] The commonly used solutions at present are: adding a large-capacity active clamping absorption circuit; detecting the negative current on the secondary side for related control, etc. However, these solutions all require the addition of additional circuit components and the increase of the volume of the overall design, and affect the power density and overall efficiency of the power converter. Summary of the invention

[0005] The embodiments of the present invention provide a method for preventing backflow of a power converter and a power converter, so as to at least solve the problem in the related art that the reverse backflow current of the power converter using synchronous rectification is too large when the input transient drops, resulting in excessive voltage stress of the synchronous rectifier tube of the power converter and avalanche failure of the synchronous rectifier tube.

[0006] According to an embodiment of the present invention, a method for preventing backflow of a power converter is provided, comprising:

[0007] When a transient drop in the input voltage of the power converter is detected, the secondary side MOS transistor driving signal of the power converter is turned off for at least a first preset time period;

[0008] When it is detected that the input voltage returns to the normal operating voltage, the secondary MOS tube driving signal is reopened.

[0009] In an exemplary embodiment, shutting down the secondary MOS tube driving signal of the power converter for at least a first preset time duration includes:

[0010] When a falling edge occurs in the primary MOS tube driving signal of the power converter, the secondary MOS tube driving signal of the power converter is turned off for at least a first preset time period.

[0011] In an exemplary embodiment, during the first preset time period when the secondary MOS tube driving signal is turned off, the method further includes:

[0012] When it is detected that the output voltage overshoot value is greater than a first preset voltage, the primary MOS tube drive signal of the power converter is turned off, and when the output voltage drops to a second preset voltage, the primary MOS tube drive signal is turned on; wherein the second preset voltage is less than the first preset voltage.

[0013] In an exemplary embodiment, after the secondary MOS tube driving signal is turned off for the first preset time, the method further includes:

[0014] When it is detected that the output voltage is greater than the set voltage threshold, the primary MOS tube drive signal is turned off, and when the output voltage decreases to a third preset voltage, the primary MOS tube drive signal is turned on again, wherein the third preset voltage is less than the set voltage threshold;

[0015] When it is detected that the output voltage is less than or equal to the set voltage threshold, the secondary MOS tube driving signal is reopened.

[0016] In an exemplary embodiment, when it is detected that the input voltage returns to a normal working voltage, reopening the secondary MOS tube driving signal includes:

[0017] When it is detected that the output voltage is lower than the rated voltage, the secondary MOS tube driving signal is reopened after a delay of a second preset time length; or,

[0018] When it is detected that the output voltage is equal to the rated voltage, the secondary MOS tube driving signal is reopened.

[0019] In an exemplary embodiment, when it is detected that the difference between two adjacent input voltages is greater than a preset voltage difference threshold, it is determined that a transient drop occurs in the input voltage.

[0020] According to another embodiment of the present invention, there is provided a power converter, including a controller, wherein the controller includes:

[0021] A first control module, configured to shut down a secondary-side MOS transistor driving signal of the power converter for at least a first preset time period when a transient drop in the input voltage of the power converter is detected;

[0022] The second control module is used to reopen the secondary MOS tube driving signal when it is detected that the input voltage returns to the normal working voltage.

[0023] In an exemplary embodiment, the first control module is used to shut down the secondary MOS tube drive signal of the power converter for at least a first preset time period when a falling edge occurs in the primary MOS tube drive signal of the power converter.

[0024] In an exemplary embodiment, the first control module is further configured to, during the first preset time period when the secondary MOS tube drive signal is turned off, turn off the primary MOS tube drive signal when it is detected that the output voltage overshoot value is greater than the first preset voltage;

[0025] The second control module is further configured to turn on the primary MOS tube drive signal when the output voltage drops to a second preset voltage; wherein the second preset voltage is lower than the first preset voltage.

[0026] In an exemplary embodiment, the first control module is further configured to, after the secondary MOS tube drive signal is turned off for the first preset time period, turn off the primary MOS tube drive signal when it is detected that the output voltage is greater than a set voltage threshold;

[0027] The second control module is further configured to reopen the primary MOS tube drive signal when the output voltage decreases to a third preset voltage, wherein the third preset voltage is less than the set voltage threshold.

[0028] In an exemplary embodiment, the second control module is used to reopen the secondary MOS tube drive signal after a second preset time delay when it is detected that the output voltage is lower than the rated voltage; or reopen the secondary MOS tube drive signal when it is detected that the output voltage is equal to the rated voltage.

[0029] In an exemplary embodiment, the first control module is used to determine that a transient drop occurs in the input voltage when it is detected that a difference between two adjacent input voltages is greater than a preset voltage difference threshold.

[0030] According to yet another embodiment of the present invention, a computer-readable storage medium is provided, in which a computer program is stored, wherein the computer program is configured to execute the steps of any one of the above method embodiments when run.

[0031] According to yet another embodiment of the present invention, there is provided an electronic device, including a memory and a processor, wherein the memory stores a computer program, and the processor is configured to run the computer program to execute the steps in any one of the above method embodiments.

[0032] The present invention uses the power converter backflow prevention method of the above embodiment. When a transient drop in the input is detected, the drive signal of the synchronous rectifier is controlled to be closed for at least a first preset time period, thereby effectively preventing the output backflow energy from accumulating and causing the problem of excessive stress when the synchronous rectifier is turned off. There is no need to add additional hardware circuits, thereby reducing the board area and cost of the entire hardware circuit, and also improving the efficiency of the power converter and the overall power density. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a schematic diagram of a conventional power converter using synchronous rectification according to an embodiment of the present invention;

[0034] Figure 2 is a flow chart of a power converter backflow prevention method according to an embodiment of the present invention;

[0035] Figure 3 is a schematic diagram of an isolated power converter circuit according to an embodiment of the present invention;

[0036] Figure 4 is a control timing logic diagram of an isolated power converter according to an embodiment of the present invention;

[0037] Figure 5 is a flow chart of a non-isolated converter backflow prevention control method according to an embodiment of the present invention;

[0038] Figure 6 is a schematic diagram of a non-isolated power converter circuit according to an embodiment of the present invention;

[0039] Figure 7 is a timing logic diagram of a non-isolated power converter control according to an embodiment of the present invention;

[0040] Figure 8 is a schematic diagram of a power converter according to an embodiment of the present invention (I);

[0041] Fig. 9 is a schematic diagram of a power converter according to an embodiment of the present invention (II);

[0042] Fig.10 is a schematic diagram of a power converter according to an embodiment of the present invention (III);

[0043] Fig.11 is a structural block diagram of a power converter according to an embodiment of the present invention. DETAILED DESCRIPTION

[0044] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings and in combination with the embodiments.

[0045] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence.

[0046] Figure 1 Schematic diagram of an existing power converter using synchronous rectification according to an embodiment of the present invention, wherein Vin is the input voltage source, Vout is the output voltage, C1 is the input capacitor, C3 is the output capacitor, Q1-Q4 are primary switch tubes, Q5-Q8 are synchronous rectifier tubes, and active clamping circuits and negative current detection circuits ensure that the stress peaks of Q5-Q8 are within the specification range. Figure 1 As shown in the figure, when the system is struck by lightning, the input voltage of the power converter drops rapidly and returns to normal after a period of time. In this scenario, the power converter will experience output energy backflow. At this time, the current flowing through the output inductor L1 is as follows: Figure 1 When the reference direction shown and the amplitude is large, when the synchronous rectifier (Q5-Q8) is suddenly turned off, there will be a large voltage stress spike, which will cause damage to the synchronous rectifier. In order to solve the problem of synchronous rectifier damage caused by the above scenario, the existing common technologies are: using a large-capacity active clamping circuit to absorb the energy of the MOSFET drain voltage spike; detecting the negative backflow current on the secondary side to control the synchronous rectifier, etc.

[0047] However, these solutions all require the addition of additional circuit components and increase the volume of the overall design, and affect the improvement of the power density and overall efficiency of the power converter.

[0048] The core concept of the embodiment of the present invention is that when a transient drop in input voltage is detected, the output backflow energy is effectively prevented from accumulating, which causes the problem of excessive stress when the synchronous rectifier is turned off, by controlling the drive shutdown timing of the synchronous rectifier. When the input voltage returns to normal, the MOS tube is turned on again in a certain timing to ensure the reliability of the power converter. This solves the problem that the reverse backflow current is too large during the input transient drop of the power converter using synchronous rectification, resulting in excessive voltage stress of the synchronous rectifier of the power converter and avalanche failure of the synchronous rectifier. The embodiment of the present invention does not need to add additional hardware circuits, thereby reducing the layout area and cost of the entire hardware circuit, while improving the efficiency and overall power density of the power converter.

[0049] In this embodiment, a method for preventing backflow of a power converter is provided. Figure 2 is a flow chart of a power converter backflow prevention method according to an embodiment of the present invention. Figure 2 As shown, the process includes the following steps:

[0050] Step S201 , when a transient drop in the input voltage of the power converter is detected, the secondary-side MOS transistor driving signal of the power converter is turned off for at least a first preset time period.

[0051] The embodiment of the present invention is described by taking an isolated power converter as an example. Figure 3 is a schematic diagram of an isolated power converter circuit according to an embodiment of the present invention, Figure 4 1 is a control timing logic diagram of an isolated power converter according to an embodiment of the present invention.

[0052] Reference Figure 3 and Figure 4 When the input voltage of the power converter drops transiently, the secondary MOS tube driving signal of the power converter can be turned off for at least a first preset time length.

[0053] In an optional embodiment, when it is detected that the difference between two adjacent input voltages is greater than a preset voltage difference threshold, it is determined that a transient drop occurs in the input voltage.

[0054] As an example, the power converter may detect the input voltage in real time, and determine that a transient drop in the input voltage occurs when it is detected that a difference ΔV between two adjacent input voltages is greater than a preset voltage difference threshold ΔVin.

[0055] As an example, the difference between the previous detection voltage and the next detection voltage may be defined as ΔV, and the preset voltage difference threshold ΔVin may be flexibly set according to actual application scenarios, and the embodiment of the present invention does not limit this.

[0056] In an optional embodiment, shutting down the secondary MOS tube drive signal of the power converter for at least a first preset duration includes: when a falling edge appears in the primary MOS tube drive signal of the power converter, shutting down the secondary MOS tube drive signal of the power converter for at least a first preset duration.

[0057] As an example, after determining that the power converter is in a state of input voltage transient drop, all secondary-side MOS tube drive signals may be immediately turned off, wherein the turn-off moment is when the primary-side MOS drive signal has a falling edge.

[0058] It should be noted that when the power converter is in no-load steady-state operation, when the output inductor current is negative, after the primary MOS tube driver is turned off and the secondary MOS tube driver is turned on, the output inductor current accumulates in a negative direction. In this state, the later the secondary MOS tube driver is turned off, the greater the stress on the secondary MOS tube. If all secondary drive signals are randomly turned off, there is a high probability that the stress on the secondary MOS tube exceeds the specification, causing damage to the MOS tube.

[0059] According to the embodiment of the present invention, after determining that the power converter is in a state of transient input voltage drop, the shutdown moment of all MOS tube drive signals on the secondary side is set to when the primary side MOS drive signal has a falling edge, thereby preventing the stress of the secondary side MOS tube from exceeding the specification and causing damage to the MOS tube.

[0060] In an optional embodiment, during the period of turning off the secondary MOS tube drive signal for the first preset time length, it also includes: when it is detected that the output voltage overshoot value is greater than the first preset voltage, turning off the primary MOS tube drive signal of the power converter, and when the output voltage drops to a second preset voltage, turning on the primary MOS tube drive signal; wherein the second preset voltage is less than the first preset voltage.

[0061] In an embodiment of the present invention, during the first preset time length t1 when the secondary MOS tube driving signal is turned off, only the primary MOS tube of the power converter drives the wave, and the secondary MOS tube only continues the current through its internal diode. If the power converter is in a no-load state and the t1 value is large, the output voltage may be too high to trigger the protection phenomenon. In order to avoid the problem of excessively high output voltage overshoot value in the t1 stage, when it is detected that the output voltage overshoot value is greater than the first preset voltage V1, the primary MOS tube driving signal of the power converter can be turned off, and when the output voltage drops to the second preset voltage V2, the primary MOS tube driving signal is turned on, thereby ensuring that the isolated power converter will not have an abnormally high output voltage protection problem caused by the secondary MOS tube being in the diode rectification mode during the t1 time period.

[0062] As an example, the first preset voltage V1 can be set according to the output overvoltage protection point. For example, the first preset voltage V1 can be set to be slightly higher than the rated voltage to control the output voltage not to exceed the output overvoltage protection point; the second preset voltage V2 can be set according to the system undervoltage point. For example, the second preset voltage V2 can be set to be slightly lower than the rated voltage to avoid the output voltage being lower than the undervoltage point and affecting the normal operation of the power converter.

[0063] In an optional embodiment, after turning off the secondary MOS tube drive signal for the first preset time period, it also includes: when it is detected that the output voltage is greater than a set voltage threshold, turning off the primary MOS tube drive signal, and when the output voltage is reduced to a third preset voltage, reopening the primary MOS tube drive signal, wherein the third preset voltage is less than the set voltage threshold; when it is detected that the output voltage is less than or equal to the set voltage threshold, reopening the secondary MOS tube drive signal.

[0064] As an example, if after the secondary MOS tube drive signal is turned off for the first preset time t1, if it is detected that the output voltage is higher than the set voltage threshold, the secondary MOS drive signal is directly turned on, energy backflow will occur, resulting in excessive stress in the secondary MOS tube when the drive signal is turned off, causing damage to the MOS tube. In order to avoid the above phenomenon, the primary MOS tube drive signal can be turned off when it is detected that the output voltage is greater than the set voltage threshold, and the primary MOS tube drive signal can be reopened when the output voltage drops to the third preset voltage V3.

[0065] As an example, if it is detected that the output voltage is less than or equal to the set voltage threshold, no energy backflow will occur, and the secondary MOS tube drive signal can be directly reopened.

[0066] As an example, the set voltage threshold can be expressed as Among them, V in is the real-time input voltage, D is the duty cycle, and N is the transformer turns ratio.

[0067] This embodiment can control the output voltage to avoid energy backflow by setting the voltage threshold, thereby ensuring the reliability of the isolated power converter.

[0068] Step S202, when it is detected that the input voltage returns to the normal working voltage, the secondary MOS tube driving signal is reopened.

[0069] As an example, when it is detected that the input voltage has returned to the normal working voltage, the secondary MOS tube drive signal can be turned on again. The normal working voltage can be a voltage range, for example, a normal working voltage of 12V-15V, or a specific voltage value, for example, a normal working voltage of 15V.

[0070] As an example, after the primary MOS tube driver is reopened, the output voltage gradually recovers. After the output voltage recovers to the rated voltage Vo or a delay of t2, the secondary MOS tube drive signal can be reopened, and the isolated power converter resumes normal operation mode.

[0071] In an optional embodiment, when it is detected that the input voltage returns to the normal operating voltage, the secondary MOS tube drive signal is reopened, including: when it is detected that the output voltage is lower than the rated voltage, the secondary MOS tube drive signal is reopened after a second preset time period; or, when it is detected that the output voltage is equal to the rated voltage, the secondary MOS tube drive signal is reopened.

[0072] As an example, after detecting that the input voltage has returned to the normal operating voltage, the secondary MOS tube drive signal can be reopened after a second preset time delay when it is detected that the output voltage is lower than the rated voltage; or, the secondary MOS tube drive signal can be reopened when it is detected that the output voltage is equal to the rated voltage.

[0073] The embodiment of the present invention solves the problem of excessive stress on the secondary MOS tube due to energy backflow when the input voltage of the isolated power converter drops transiently, by shutting off the secondary MOS tube drive signal of the power converter for at least a first preset time period when a transient drop in the input voltage of the power converter is detected, and reopening the secondary MOS tube drive signal when the input voltage is detected to be restored to a normal operating voltage, thereby effectively ensuring the reliability of the power converter.

[0074] The method for preventing backflow of a power converter of the present invention is not only applicable to isolated power converters, but also to non-isolated converters, and is described below through Example 1:

[0075] Embodiment 1:

[0076] Figure 5 is a flow chart of a non-isolated converter backflow prevention control method according to an embodiment of the present invention, Figure 6 is a schematic diagram of a non-isolated power converter circuit according to an embodiment of the present invention, Figure 7 1 is a control timing logic diagram of a non-isolated power converter according to an embodiment of the present invention.

[0077] Reference Figure 5 , Figure 6 , Figure 7 When the non-isolated power converter detects that the difference ΔV between two adjacent input voltages is greater than the preset input voltage difference threshold ΔVin, it is determined that the input voltage is in a transient drop state.

[0078] Among them, the difference between the previous detected input voltage and the next detected input voltage of the non-isolated power converter can be defined as ΔV, and the input voltage difference threshold ΔVin of the non-isolated power converter is flexibly set according to the actual application scenario, and the embodiment of the present invention does not limit this.

[0079] After determining that the non-isolated power converter is in a state of transient input voltage drop, the freewheeling tube MOS tube drive signal can be immediately turned off, and the turn-off time is: when the switch tube MOS tube drive signal has a falling edge.

[0080] The duration of shutting off the freewheeling tube MOS drive signal can be set to t1. During the t1 period, the non-isolated power converter only has the switch tube MOS drive signal waving, and the freewheeling tube MOS only continues current through the internal diode, and the non-isolated power converter detects the output voltage in real time. If the power converter is in a no-load state and the t1 value is large, the output voltage may be too high to trigger the protection phenomenon. In order to avoid the problem of excessive output voltage overshoot in the t1 stage, the switch tube MOS drive signal can be turned off when it is detected that the output voltage overshoot value is greater than the preset voltage V1, and the switch tube MOS drive signal can be turned on when the output voltage drops to the preset voltage V2, thereby ensuring that the non-isolated power converter will not have an abnormally high output voltage protection problem caused by the freewheeling tube MOS tube being in the diode rectification mode during the t1 period.

[0081] After the t1 period, the input voltage waveform gradually recovers. If the output voltage is detected to be greater than the set voltage threshold V in *D, the MOS drive signal of the switch tube can be turned off first, and then the MOS drive signal of the switch tube can be turned on when the output voltage drops to the preset voltage V3, wherein the preset voltage V3 can be set according to the rated output voltage, so as to avoid energy backflow, resulting in excessive stress of the freewheeling tube MOS tube when the drive signal is turned off, causing damage to the MOS tube; if it is detected that the output voltage is less than or equal to the set voltage threshold V in *D, there will be no energy backflow, and the MOS drive signal can be directly reopened. By setting the voltage threshold V in *D, which can avoid energy backflow in the output voltage of the non-isolated power converter and ensure the reliability of the non-isolated power converter.

[0082] After the MOS driving signal of the switching tube is turned on again, the output voltage gradually recovers. After the output voltage returns to the normal operating voltage or delays for t2 time (t2 can be flexibly set according to the specific actual application scenario), the MOS driving signal of the freewheeling tube can be turned on again, and the non-isolated power converter resumes the normal operating mode.

[0083] The control method can solve the problem of MOS stress exceeding the specification due to energy backflow when the input voltage of the non-isolated power converter drops transiently, thereby effectively ensuring the reliability of the non-isolated power converter.

[0084] The method for preventing backflow of a power converter of the present invention is not only applicable to isolated power converters and non-isolated power converters, but also applicable to other types of power converters, which will be described below through Examples 2-4.

[0085] Example 2

[0086] Figure 8 1 is a schematic diagram of a power converter according to an embodiment of the present invention (I).

[0087] Reference Figure 8 When the power converter detects that the voltage difference ΔV between two adjacent input voltages is greater than the set value ΔVin, it is determined that the input voltage is in a transient drop state.

[0088] Step 1: After determining that the power converter is in a state of transient input voltage drop, the secondary side Q7 / Q8 MOS drive signal can be immediately turned off. The turn-off time is: when the primary side Q3 / Q4 MOS drive has a falling edge.

[0089] Step 2: Turn off the secondary Q7 / Q8MOS drive signal for t1 duration: During the t1 duration stage, only the primary Q3 / Q4MOS drive of the isolated power converter generates current, and the secondary Q7 / Q8MOS only flows through the internal diode. If the converter detects that the output voltage overshoot value is greater than its set value V1 within t1, the primary Q3 / Q4MOS drive signal is turned off, and when the output voltage is detected to drop to its set value V2, the Q3 / Q4 primary MOS drive signal is turned on.

[0090] Step 3: After the t1 period, the input voltage waveform gradually recovers. If the output voltage is detected to be higher than the set voltage threshold, the primary side Q3 / Q4MOS driver can be turned off first, and when the output voltage drops to the set value V3, the primary side Q3 / Q4MOS drive signal can be turned on; if it is detected that the output voltage is less than or equal to the set voltage threshold, the secondary side Q7 / Q8MOS drive signal can be directly turned on.

[0091] Step 4: After the primary side Q3 / Q4 MOS drive signal is turned on again, the output voltage gradually recovers. After it recovers to the normal operating voltage V0 or after a delay of t2, the secondary side Q7 / Q8 drive signal is turned on again, and the power converter resumes normal operating mode.

[0092] Example 3

[0093] Fig. 9 2 is a schematic diagram of a power converter according to an embodiment of the present invention.

[0094] Reference Fig. 9 When the power converter detects that the voltage difference ΔV between two adjacent input voltages is greater than the set value ΔVin, it is determined that the input voltage is in a transient drop state.

[0095] Step 1: After determining that the power converter is in a state of transient input voltage drop, the secondary side Q5-Q8 MOS drive signal can be immediately turned off, and the turn-off time is: when the primary side Q3 / Q4 MOS drive signal has a falling edge.

[0096] Step 2: Turn off the secondary Q5~Q8MOS drive signal for t1 duration: During the t1 duration stage, only the primary Q3 / Q4MOS drive signal of the power converter is oscillating, and the secondary Q5~Q8MOS only continues current through the internal diode. If the voltage converter detects that the output voltage overshoot value is greater than the set value V1 within t1, the primary Q3 / Q4MOS drive signal can be turned off, and when the output voltage is detected to drop to the set value V2, the primary Q3 / Q4 MOS drive signal is turned on.

[0097] Step 3: After the t1 period, the input voltage waveform gradually recovers. If the output voltage is detected to be higher than the set voltage threshold, the primary Q3 / Q4MOS drive signal can be turned off first, and when the output voltage drops to the set value V3, the primary Q3 / Q4MOS drive signal can be turned on; if it is detected that the output voltage is less than or equal to the set voltage threshold, the secondary Q7 / Q8MOS drive signal can be directly turned on.

[0098] Step 4: After the primary side Q3 / Q4 MOS driver is turned on again, the output voltage gradually recovers. After it recovers to the normal operating voltage V0 or after a delay of t2, the secondary side Q5~Q8 drive signal is turned on again, and the power converter resumes normal operating mode.

[0099] Example 4

[0100] Fig.10 3 is a schematic diagram of a power converter according to an embodiment of the present invention.

[0101] Reference Fig.10When the power converter detects that the voltage difference ΔV between two adjacent input voltages is greater than the set value ΔVin, it is determined that the input voltage is in a transient drop state.

[0102] Step 1: After determining that the power converter is in a state of transient input voltage drop, the rectifier tube Q2MOS drive signal can be immediately turned off, and the turn-off time is: when the switch tube Q1MOS drive signal has a falling edge.

[0103] Step 2: Turn off the rectifier tube Q2MOS drive signal for t1 duration: During the t1 duration stage, only the switch tube Q1MOS drive signal of the power converter is emitting, and the rectifier tube Q2MOS only continues current through the internal diode. If the power converter detects that the output voltage overshoot value is greater than the set value V1 within t1, the switch tube Q1MOS drive can be turned off, and when the output voltage is detected to drop to the set value V2, the switch tube Q1MOS drive signal can be turned on.

[0104] Step three: After the t1 period, the input voltage waveform gradually recovers. If it is detected that the output voltage is higher than the set voltage threshold, the switch tube Q1MOS drive signal can be turned off first, and when the output voltage drops to the set value V3, the switch tube Q1MOS drive signal can be turned on; if it is detected that the output voltage is less than or equal to the set voltage threshold, the rectifier tube Q2MOS drive signal can be directly turned on.

[0105] Step 4: After the switch tube Q1MOS driver is turned on again, the output voltage gradually recovers. After it recovers to the normal operating voltage V0 or after a delay of t2, the rectifier tube Q2MOS driver can be turned on again, and the power converter resumes normal operating mode.

[0106] The present invention uses the power converter anti-backflow method of the above embodiment. When a transient drop in the input is detected, the output backflow energy can be effectively prevented from accumulating by controlling the drive shutdown timing of the synchronous rectifier tube, which leads to the problem of excessive stress when the synchronous rectifier tube is turned off. When the input returns to normal, the power MOS is turned on again according to a certain timing to ensure the reliability of the power converter. This solves the problem that the reverse backflow current is too large during the input transient drop of the power converter using synchronous rectification, resulting in excessive voltage stress of the synchronous rectifier tube of the power converter and avalanche failure of the synchronous rectifier tube; moreover, there is no need to add additional hardware circuits, thereby reducing the layout area and cost of the entire hardware circuit, and also improving the efficiency and overall power density of the power converter.

[0107] Through the description of the above implementation methods, those skilled in the art can clearly understand that the method according to the above embodiment can be implemented by means of software plus a necessary general hardware platform, and of course can also be implemented by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present invention, or the part that contributes to the prior art, can be embodied in the form of a software product, which is stored in a storage medium (such as ROM / RAM, a magnetic disk, or an optical disk), and includes a number of instructions for enabling a terminal device (which can be a mobile phone, a computer, a server, or a network device, etc.) to execute the methods described in each embodiment of the present invention.

[0108] In this embodiment, a power converter is also provided, which is used to implement the above-mentioned embodiments and preferred embodiments, and the descriptions that have been made will not be repeated. As used below, the term "module" can implement a combination of software and / or hardware of a predetermined function. Although the device described in the following embodiments is preferably implemented in software, the implementation of hardware, or a combination of software and hardware is also possible and conceived.

[0109] Fig.11 is a structural block diagram of a power converter according to an embodiment of the present invention. Fig.11 As shown, the power converter 11 includes a controller 110, wherein the controller includes:

[0110] The first control module 1101 is used to shut down the secondary side MOS transistor driving signal of the power converter for at least a first preset time period when a transient drop in the input voltage of the power converter is detected;

[0111] The second control module 1102 is used to reopen the secondary MOS tube driving signal when it is detected that the input voltage returns to the normal working voltage.

[0112] In an optional embodiment, the first control module 1101 is used to shut down the secondary MOS tube drive signal of the power converter for at least a first preset duration when a falling edge occurs in the primary MOS tube drive signal of the power converter.

[0113] In an optional embodiment, the first control module 1101 is further configured to, during the first preset time period of shutting down the secondary MOS tube drive signal, shut down the primary MOS tube drive signal when it is detected that the output voltage overshoot value is greater than the first preset voltage;

[0114] The second control module 1101 is further configured to turn on the primary MOS tube drive signal when the output voltage drops to a second preset voltage; wherein the second preset voltage is lower than the first preset voltage.

[0115] In an optional embodiment, the first control module 1101 is further configured to, after the secondary MOS tube drive signal is turned off for the first preset time period, turn off the primary MOS tube drive signal when it is detected that the output voltage is greater than a set voltage threshold;

[0116] The second control module 1101 is also used to reopen the primary MOS tube drive signal when the output voltage drops to a third preset voltage, wherein the third preset voltage is less than the set voltage threshold; and reopen the secondary MOS tube drive signal when it is detected that the output voltage is less than or equal to the set voltage threshold.

[0117] In an optional embodiment, the second control module 1102 is used to reopen the secondary MOS tube drive signal after a second preset time delay when it is detected that the output voltage is lower than the rated voltage; or reopen the secondary MOS tube drive signal when it is detected that the output voltage is equal to the rated voltage.

[0118] In an optional embodiment, the first control module 1101 is used to determine that a transient drop occurs in the input voltage when it is detected that the difference between two adjacent input voltages is greater than a preset voltage difference threshold.

[0119] It should be noted that the above modules can be implemented by software or hardware. For the latter, it can be implemented in the following ways, but not limited to: the above modules are all located in the same processor; or the above modules are located in different processors in any combination.

[0120] An embodiment of the present invention further provides a computer-readable storage medium, in which a computer program is stored, wherein the computer program is configured to execute the steps of any of the above method embodiments when running.

[0121] In an exemplary embodiment, the computer-readable storage medium may include, but is not limited to, various media that can store computer programs, such as a USB flash drive, a read-only memory (ROM), a random access memory (RAM), a mobile hard disk, a magnetic disk or an optical disk.

[0122] An embodiment of the present invention further provides an electronic device, including a memory and a processor, wherein a computer program is stored in the memory, and the processor is configured to run the computer program to execute the steps in any one of the above method embodiments.

[0123] In an exemplary embodiment, the electronic device may further include a transmission device and an input / output device, wherein the transmission device is connected to the processor, and the input / output device is connected to the processor.

[0124] For specific examples in this embodiment, reference may be made to the examples described in the above embodiments and exemplary implementation modes, and this embodiment will not be described in detail herein.

[0125] Obviously, those skilled in the art should understand that the above modules or steps of the present invention can be implemented by a general computing device, they can be concentrated on a single computing device, or distributed on a network composed of multiple computing devices, they can be implemented by a program code executable by a computing device, so that they can be stored in a storage device and executed by the computing device, and in some cases, the steps shown or described can be executed in a different order than here, or they can be made into individual integrated circuit modules, or multiple modules or steps therein can be made into a single integrated circuit module for implementation. Thus, the present invention is not limited to any specific combination of hardware and software.

[0126] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preventing backflow of a power converter, characterized in that: include: When a transient drop in the input voltage of the power converter is detected, the secondary side MOS transistor driving signal of the power converter is turned off for at least a first preset time period; When it is detected that the input voltage returns to the normal operating voltage, the secondary MOS tube driving signal is reopened.

2. The method according to claim 1, characterized in that Turning off the secondary MOS tube driving signal of the power converter for at least a first preset time duration includes: When a falling edge occurs in the primary MOS tube driving signal of the power converter, the secondary MOS tube driving signal of the power converter is turned off for at least a first preset time period.

3. The method according to claim 1, characterized in that During the first preset time period when the secondary MOS tube driving signal is turned off, the method further includes: When it is detected that the output voltage overshoot value is greater than a first preset voltage, the primary MOS tube drive signal of the power converter is turned off, and when the output voltage drops to a second preset voltage, the primary MOS tube drive signal is turned on; wherein the second preset voltage is less than the first preset voltage.

4. The method according to any one of claims 1 to 3, characterized in that: After turning off the secondary MOS tube driving signal for the first preset time, the method further includes: When it is detected that the output voltage is greater than the set voltage threshold, the primary MOS tube drive signal is turned off, and when the output voltage decreases to a third preset voltage, the primary MOS tube drive signal is turned on again, wherein the third preset voltage is less than the set voltage threshold; When it is detected that the output voltage is less than or equal to the set voltage threshold, the secondary MOS tube driving signal is reopened.

5. The method according to claim 1, characterized in that When it is detected that the input voltage returns to the normal working voltage, the secondary MOS tube driving signal is reopened, including: When it is detected that the output voltage is lower than the rated voltage, the secondary MOS tube driving signal is reopened after a delay of a second preset time length; or, When it is detected that the output voltage is equal to the rated voltage, the secondary MOS tube driving signal is reopened.

6. The method according to claim 1, characterized in that When it is detected that the difference between two adjacent input voltages is greater than a preset voltage difference threshold, it is determined that a transient drop occurs in the input voltage.

7. A power converter, characterized in that: A controller is included, wherein the controller includes: A first control module, configured to shut down a secondary-side MOS transistor driving signal of the power converter for at least a first preset time period when a transient drop in the input voltage of the power converter is detected; The second control module is used to reopen the secondary MOS tube driving signal when it is detected that the input voltage returns to the normal working voltage.

8. The power converter according to claim 7, characterized in that: The first control module is further configured to, during the first preset time period when the secondary MOS tube driving signal is turned off, turn off the primary MOS tube driving signal when it is detected that the output voltage overshoot value is greater than the first preset voltage; The second control module is further configured to turn on the primary MOS tube drive signal when the output voltage drops to a second preset voltage; wherein the second preset voltage is lower than the first preset voltage.

9. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, wherein the computer program implements the steps of the method described in any one of claims 1 to 6 when executed by a processor.

10. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of the method described in any one of claims 1 to 6 are implemented.

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