Overvoltage protection circuit, driving chip and switching power supply

Abstract

The invention relates to an overvoltage protection circuit, a driving chip and a switching power supply. The overvoltage protection circuit comprises a first current module, a second current module, a first energy storage module, a second energy storage module and a judgment module, the first current module is used for outputting first charging current in the demagnetization time to charge the first energy storage module; the second current module is used for outputting a second charging current which is positively correlated with the input voltage within the conduction time of the power tube so as to charge the second energy storage module; the judgment module is used for judging whether the second voltage of the second energy storage module is larger than the first voltage of the first energy storage module or not when demagnetization is finished, and outputting an overvoltage protection signal when the second voltage is larger than the first voltage, so that the situation that deviation exists in judgment of overvoltage protection due to deviation existing in inductor production can be avoided; the consistency and reliability of the overvoltage protection trigger threshold are ensured, and the precision is high.

Description

Technical Field

[0001] The present application relates to the field of power management technology, and in particular to an overvoltage protection circuit, a driver chip and a switching power supply. Background Art

[0002] With the development of power electronics technology, in order to improve the safety of the driving power supply, the current driving power supplies are basically designed with an overvoltage protection mechanism, which prevents the output voltage from being too high and damaging the components in the driving power supply. In order to protect the driving power supply, it is necessary to determine whether the output of the driving power supply is overvoltage. Therefore, how to determine whether the output of the driving power supply is overvoltage and then protect it is a problem that needs to be solved at present.

[0003] Traditional output overvoltage protection is achieved by detecting the demagnetization time, for example, ,therefore, ;in, is the inductor, is the inductor peak current, is the demagnetization time. It can be seen that by detecting Time and built-in set time The size of can determine whether it is overvoltage protection. For example, when When it is judged as overvoltage protection, but When there is a deviation in inductance during production, The voltage will also change accordingly, which will cause deviations in the judgment of overvoltage protection. Summary of the invention

[0004] Based on this, it is necessary to provide an overvoltage protection circuit, a driver chip and a switching power supply, which can avoid the situation where the inductance deviation in production causes the overvoltage protection judgment to be biased, thereby ensuring the reliability of the overvoltage protection judgment with high accuracy.

[0005] In a first aspect, the present application provides an overvoltage protection circuit, comprising: a first current module, a second current module, a first energy storage module, a second energy storage module and a judgment module;

[0006] a first current module, electrically connected to the first energy storage module, and configured to output a first charging current I1 within a demagnetization time to charge the first energy storage module;

[0007] A second current module, electrically connected to the second energy storage module, and configured to output a second charging current I2 positively correlated with the input voltage Vin during the conduction time of the power tube to charge the second energy storage module;

[0008] The judgment module is electrically connected to the first energy storage module and the second energy storage module respectively, and is used to judge whether the second voltage of the second energy storage module is greater than the first voltage of the first energy storage module when demagnetization is completed, and output an overvoltage protection signal when the second voltage is greater than the first voltage.

[0009] In one embodiment, the determination module includes:

[0010] A comparison unit, configured to compare the first voltage and the second voltage and output a comparison signal;

[0011] The latch unit is connected to the output end of the comparison unit and is used to latch the comparison signal when the demagnetization is completed.

[0012] In one of the embodiments, it further includes: a reset module;

[0013] The reset module is used to discharge the first energy storage module and the second energy storage module after demagnetization is completed, so as to reset the first energy storage module and the second energy storage module.

[0014] In one embodiment, the first current module includes:

[0015] A first current unit, used to generate a first initial charging current I01;

[0016] A first current mirror unit, connected to the first current unit, and configured to generate the first charging current I1 in mirror proportion to the first initial charging current I01;

[0017] The first switch unit is connected to the first current mirror unit, and is configured to be in a conducting state during the demagnetization time to output the first charging current I1 to charge the first energy storage module.

[0018] In one embodiment, the second current module includes:

[0019] A second current unit, used for receiving the input voltage Vin, and converting the input voltage Vin into a second initial charging current I02; wherein I02=K*Vin, K is a proportionality coefficient;

[0020] A second current mirror unit, connected to the second current unit, and configured to generate the second charging current I2 in mirror proportion to the second initial charging current I02;

[0021] The second switch unit is connected to the second current mirror unit, and is used to be in a conducting state during the conduction time of the power tube to output the second charging current I2 to charge the second energy storage module.

[0022] In one embodiment, the second current module includes:

[0023] A second current unit, used for receiving the input voltage Vin, and converting the input voltage Vin into a second initial charging current I02; wherein I02=K*Vin, K is a proportionality coefficient;

[0024] A second current mirror unit, electrically connected to the second current unit, and configured to generate a second mirror current Im in mirror proportion to the second initial charging current I02;

[0025] A first current source, used to generate a preset current Io proportional to the first initial charging current I01;

[0026] The third switch unit is electrically connected to the first current source, and is used to be in a conducting state during the conduction period of the power tube to output the second charging current I2 to charge the second energy storage module; wherein I2=Im-Io.

[0027] In one embodiment, the third switch unit includes: a first switch and a second switch; wherein the first end of the first switch is connected to the second current mirror unit, the second end of the first switch is connected to the first end of the second switch, and the second end of the second switch is connected to the first current source; the first switch and the second switch are respectively in the on state during the on time period of the power tube.

[0028] In one embodiment, the first current source comprises:

[0029] a third current mirror unit;

[0030] The third current mirror unit is used to output the preset current Io in mirror proportion to the first initial charging current I01.

[0031] In a second aspect, the present application also provides a driver chip, characterized in that it includes the aforementioned overvoltage protection circuit.

[0032] In a third aspect, the present application also provides a switching power supply, characterized in that it includes the aforementioned driver chip.

[0033] The above-mentioned overvoltage protection circuit, driving chip and switching power supply include a first current module, a second current module, a first energy storage module, a second energy storage module and a judgment module. The first current module can generate a first charging current to charge the first energy storage module during the demagnetization time, and the second current module can generate a second charging current based on the input voltage during the conduction time to charge the second energy storage module. The judgment module can judge whether the second voltage of the second energy storage module is greater than the first voltage of the first energy storage module at the end of the demagnetization time, and output an overvoltage protection signal when the second voltage is greater than the first voltage. In the present application, the overvoltage protection triggering threshold is related to the input voltage, the conduction time of the power tube, the demagnetization time, etc., but has nothing to do with the inductance. This can avoid the situation where the judgment of the overvoltage protection will also have deviations due to deviations in the inductance during production, and can avoid false triggering of the overvoltage protection, achieve safe and reliable detection protection, and have high overvoltage judgment accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the conventional technology, the drawings required for use in the embodiments or the conventional technology descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0035] FIG1 is a schematic diagram of an overvoltage protection circuit according to an embodiment of the present invention;

[0036] FIG2 is a timing diagram of an overvoltage protection circuit according to an embodiment;

[0037] FIG3 is a second circuit diagram of an overvoltage protection circuit according to an embodiment;

[0038] FIG4 is a third circuit diagram of an overvoltage protection circuit according to an embodiment;

[0039] FIG5 is a fourth circuit diagram of an overvoltage protection circuit according to an embodiment;

[0040] FIG6 is a circuit diagram of a switching power supply according to an embodiment of the present invention;

[0041] FIG7 is a fifth circuit diagram of an overvoltage protection circuit according to an embodiment;

[0042] FIG8 is a circuit diagram of a switching power supply according to another embodiment;

[0043] FIG9 is a sixth circuit diagram of an overvoltage protection circuit according to an embodiment;

[0044] FIG10 is a seventh circuit diagram of an overvoltage protection circuit according to an embodiment;

[0045] FIG. 11 is an eighth circuit diagram of an overvoltage protection circuit according to an embodiment.

[0046] Description of reference numerals:

[0047] 110 - a first current module; 111 - a first current unit; 112 - a first current mirror unit; 113 - a first switch unit;

[0048] 120 - second current module; 121 - second current unit; 122 - second current mirror unit; 123 - second switch unit; 124 - third switch unit; 1241 - first switch; 1242 - second switch; 125 - first current source;

[0049] 130-first energy storage module;

[0050] 140- second energy storage module;

[0051] 150-judgment module; 151-comparison unit; 152-latch unit; 1521-D flip-flop;

[0052] 160 - reset module; 161 - first reset unit; 162 - second reset unit. DETAILED DESCRIPTION

[0053] In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. Embodiments of the present application are provided in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0054] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0055] It is understood that the terms "first", "second", etc. used in this application may be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish a first element from another element. For example, without departing from the scope of this application, a first resistor may be referred to as a second resistor, and similarly, a second resistor may be referred to as a first resistor. Both the first resistor and the second resistor are resistors, but they are not the same resistor.

[0056] It can be understood that the “connection” in the following embodiments should be understood as “electrical connection”, “communication connection”, etc. if the connected circuits, modules, units, etc. have electrical signals or data transmission between each other.

[0057] It can be understood that “at least one” means one or more, “plurality” means two or more, and “at least a portion of an element” means a part or all of an element.

[0058] When used herein, the singular forms "a", "an", and "said / the" may also include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "include / comprise" or "have" and the like specify the presence of stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not exclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. At the same time, the term "and / or" used in this specification includes any and all combinations of the relevant listed items.

[0059] Traditional output overvoltage protection is achieved by detecting the demagnetization time, for example, ,therefore, ;in, is the inductor, is the inductor peak current, is the demagnetization time. It can be seen that by detecting Time and built-in set time The size of can determine whether it is overvoltage protection. For example, when When it is judged as overvoltage protection, but When there is a deviation in inductance during production, The voltage will also change accordingly, which will cause deviations in the judgment of overvoltage protection.

[0060] Based on this, the present application provides an overvoltage protection circuit that can improve the accuracy of overvoltage protection judgment, quickly and effectively identify output overvoltage, and effectively prevent false triggering, and the responsiveness of output overvoltage protection detection is better.

[0061] As shown in FIG1 , in an exemplary embodiment, an overvoltage protection circuit can be applied to a switching power supply. The switching power supply can be one of a Buck-type switching power supply, a Buck-Boost-type switching power supply, a Boost-type switching power supply, and a flyback-type switching power supply. In the embodiment of the present application, the switching power supply is a Buck-type switching power supply as an example for explanation. Output overvoltage protection (Over Voltage Protection, OVP) is a more commonly used protection method in the switching power supply protection circuit. It can effectively identify abnormal conditions when the switching power supply is in an output overvoltage, and control the switching state of the transistor in the switching power supply to prevent damage to the switching power supply.

[0062] The overvoltage protection circuit may include: a first current module 110, a second current module 120, a first energy storage module 130, a second energy storage module 140 and a judgment module 150. The first current module 110 is electrically connected to the first energy storage module 130, and is used to output a first charging current I1 during the demagnetization time to charge the first energy storage module 130. The first current module 110 may generate a first charging current, and the current of the first charging current may be related to the device parameters of the relevant devices in the first current module 110. In the embodiment of the present application, the device parameters of the relevant devices in the first current module 110 may be set so that the first current module 110 generates a preset first charging current. The first current module 110 may include a current source device, and may also include other electrical devices that can generate current signals. In the embodiment of the present application, the specific composition form of the first current module 110 is not specifically limited.

[0063] The first energy storage module 130 can be charged with the first charging current during the demagnetization time T2. It is understandable that the charging time of the first energy storage module 130 is the demagnetization time T2. , i.e. the demagnetization time of the inductor L1 in FIG6 and FIG8 , or the freewheeling time of the freewheeling diode D1, specifically, the time period from when the power switch tube N1 is turned off to when the current flowing through L1 (or D1) is zero. During this period, the inductor L1 is in the demagnetization stage, and the demagnetization signal =1, after demagnetization is completed, the demagnetization signal =0, therefore, the degaussing signal =1, the time period corresponding to which can be regarded as the demagnetization time T2. The demagnetization time T2 can be obtained by detecting the gate terminal voltage of the power switch tube.

[0064] The second current module 120 is electrically connected to the second energy storage module 140, and is used to output a second charging current I2 that is positively correlated with the input voltage Vin during the on-time T1 of the power tube (for example, T1 is the time period corresponding to the on-signal Ton=1) to charge the second energy storage module 140. The input voltage Vin varies depending on the application circuit. For example, it can be the voltage of the negative output terminal VOUT- of the switching power supply, or it can be the voltage of the positive output terminal VOUT+ of the switching power supply. The second current module 120 can generate a second charging current that is positively correlated with the input voltage based on the received input voltage. During the on-time (Ton=1) of the power tube, the second charging current is used to charge the second energy storage module 140. Among them, the demagnetization time and the on-time of the power tube do not overlap. In an embodiment of the present application, the on-time (Ton=1), the demagnetization time ( ), the demagnetization end delay time (TD_dk=1) can constitute the overvoltage detection cycle of the overvoltage protection circuit. Exemplarily, in the overvoltage detection cycle, its conduction time is earlier than the demagnetization time, as shown in FIG2 .

[0065] The judgment module 150 is electrically connected to the first energy storage module 130 and the second energy storage module 140 respectively. ) is in the charging state, and at the end of the demagnetization time ( When the first input terminal of the judgment module 150 jumps from high to low), the node voltage connected to the first energy storage module 130 is the first voltage. Wherein, when the first charging current and the energy storage parameters of the first energy storage module 130 are constant, the first voltage is positively correlated with the demagnetization time T2. It can be understood that the longer the demagnetization time is, the greater the first voltage is. The second storage module is in a charging state during the on-time (Ton=1). After the on-time is over, the node voltage connected to the second input terminal of the judgment module 150 and the second energy storage module 140 is the second voltage. Wherein, when the second charging current and the energy storage parameters of the second energy storage module 140 are constant, the second voltage is positively correlated with the on-time T1. It can be understood that the longer the on-time T1 is, the greater the second voltage is.

[0066] At the end of the demagnetization time, the judgment module 150 judges whether the second voltage of the second energy storage module 140 is greater than the first voltage of the first energy storage module 130, and when the second voltage is greater than the first voltage, outputs an overvoltage protection signal to control the switching state of the transistor N1 in the switching power supply to prevent damage to the switching power supply.

[0067] The overvoltage protection circuit of the present application includes a first current module, a second current module, a first energy storage module, a second energy storage module and a judgment module. The first current module can generate a first charging current to charge the first energy storage module during the demagnetization time, and the second current module can generate a second charging current based on the input voltage during the conduction time to charge the second energy storage module. The judgment module can judge whether the second voltage of the second energy storage module is greater than the first voltage of the first energy storage module at the end of the demagnetization time, and output an overvoltage protection signal OVP of "1" when the second voltage is greater than the first voltage. In the embodiment of the present application, the overvoltage protection triggering threshold is related to the input voltage, the conduction time of the power tube, the demagnetization time, etc., and has nothing to do with the capacitor CL. Specifically, it is related to the first charging current, the second charging current, the capacity value of the first energy storage module, and the capacity value of the second storage module, but is not related to the capacitor CL. The inductance is irrelevant, so as to avoid the deviation of inductance in production, which may lead to the deviation of overvoltage protection judgment. It can avoid the false triggering of overvoltage protection, realize safe and reliable overvoltage protection detection, and ensure the high accuracy of overvoltage protection.

[0068] In an exemplary embodiment, the first energy storage module 130 and the second energy storage module 140 may respectively include at least one energy storage device. Among them, the energy storage device may be a capacitor device. Exemplarily, as shown in FIG3, the first energy storage module 130 may include a first capacitor C1, the first end of which may be used as the first end of the first energy storage module, connected to the first current module 110, and the second end of the first capacitor C1 may be used as the second end of the first energy storage module 130, connected to the common potential end. Exemplarily, the common potential end may be a common ground end. Optionally, the first energy storage module 130 may also include a plurality of energy storage devices, for example, a plurality of first capacitors or at least one first capacitor or at least one first inductor. The plurality of energy storage devices in the first energy storage module 130 may be connected in at least one of parallel and series connection. Accordingly, the second energy storage module 140 may include a second capacitor C2, the first end of which may be used as the first end of the second energy storage module, connected to the second current module 120, and the second end of the second capacitor C2 may be used as the second end of the second energy storage module 140, connected to the common potential end. Optionally, the second energy storage module 140 may further include a plurality of energy storage devices, which may be connected in at least one of parallel and series connection. It should be noted that in the embodiment of the present application, the device type, quantity and connection relationship of the energy storage devices specifically included in the first energy storage module 130 and the second energy storage module 140 are not limited to the above examples.

[0069] In this embodiment, a simple energy storage device (such as a capacitor) is used as the first energy storage module and the second energy storage module, wherein the first voltage is negatively correlated with the capacitance of the first capacitor in the first energy storage module, and the second voltage is negatively correlated with the capacitance of the second capacitor C2 in the second energy storage module 140. The first voltage and the second voltage can be set by setting the capacitance of the first capacitor C1 and the second capacitor C2.

[0070] Please continue to refer to FIG. 3. In an exemplary embodiment, the first current module 110 includes a first current unit 111, a first current mirror unit 112, and a first switch unit 113. The first current unit 111 can be used to generate a first initial charging current I01. Exemplarily, the first current unit 111 can include at least a current source device to provide a corresponding current signal. Optionally, the first current unit 111 can include a voltage source and a conversion module, wherein the voltage source can provide a preset voltage signal, and the conversion module can convert the preset voltage signal to generate a corresponding current signal.

[0071] The first current mirror unit 112 is connected to the first current unit 111, and is used to generate a first charging current I1 that is in mirror proportion to the first initial charging current I01. Exemplarily, the relationship between the first charging current and the first initial charging current can be expressed as: first charging current I1=a*first initial charging current I01. Wherein, a is a mirror proportion coefficient, and the mirror proportion coefficient can be set according to demand, for example, a can be 1, or it can be a positive number greater than 1. The mirror proportion coefficient in the embodiment of the present application is not limited. Exemplarily, the first current mirror unit 112 includes but is not limited to a simple current mirror, a common source and common gate current mirror, a low-voltage common source and common gate current mirror, and a multi-stage current mirror. In the embodiment of the present application, the type of current mirror included in the first current mirror unit 112 is not specifically limited.

[0072] The first switch unit 113 is connected to the first current mirror unit 112 and is used to ) is in a conducting state to output a first charging current I1 to charge the first energy storage module 130. The first switch unit 113 can be in a conducting state within the demagnetization time ( ) is in an on state in response to the first switch control signal to transmit the first charging current generated by the first current mirror unit 112 to the first energy storage module 130 to charge the first energy storage module 130. The first switch unit 113 may be in an off state in response to the first switch control signal during the non-demagnetization time to disconnect the charging path for transmitting the first charging current to the first energy storage module 130 to suspend charging the first energy storage module 130. The first switch control signal may be selected as a demagnetization signal In the embodiment of the present application, the signal type of the first switch control signal can be determined according to the switch type included in the first switch unit 113. Exemplarily, the switch type of the switch in the first switch unit 113 includes but is not limited to a transistor, a field effect transistor, an electric knife switch, a relay, a thyristor, and the like.

[0073] In the embodiment of the present application, for the convenience of explanation, as shown in FIG4, the first current unit 111 includes a current source IS, a resistor Rovp, a resistor Rcs, a third capacitor C3, a first operational amplifier U1, a first switch tube M1 and a fourth resistor R4. The first end of the current source IS receives a preset voltage VDD, the second end of the current source IS is respectively connected to the first end of the resistor Rovp and the first end of the resistor Rcs, the second end of the resistor Rovp is connected to the common potential end, the second end of the resistor Rcs is respectively connected to the first end of the third capacitor C3 and the first input end (for example, the positive phase input end) of the first operational amplifier U1, the second end of the third capacitor C3 is connected to the common potential end, the second input end (for example, the negative phase input end) of the first operational amplifier U1 is respectively connected to the first end of the resistor R4 and the second pole of the first switch tube M1, the output end of the first operational amplifier U1 is connected to the gate of the first switch tube M1, the second end of the resistor R4 is connected to the common potential end, and the first pole of the first switch tube M1 is connected to the first current mirror unit 112. The first initial charging current I01 generated by the first current unit 111 is related to the resistor R4, the resistance value of the resistor Rovp, and the current Iovp of the current source IS. The first initial charging current I01 is negatively correlated with the resistance value of the resistor R4, and positively correlated with the resistance value of the resistor Rovp and the current Iovp. It should be noted that, in one embodiment, the first pole of the first switch tube M1 is a drain, and the second pole is a source.

[0074] The first current mirror unit 112 may include a cascode current mirror. Exemplarily, the cascode current mirror includes: a second switch tube M2 and a third switch tube M3, wherein the gate of the second switch tube M2 is respectively connected to the gate of the third switch tube M3 and the second end of the first switch tube M1, the first pole of the second switch tube M2 is connected to the gate of the second switch tube M2, and the second pole of the second switch tube M2 is used to receive a preset voltage VDD; the first pole of the third switch tube M3 is connected to the first switch unit 113, and the second pole of the third switch tube M3 is used to receive a preset voltage VDD. Wherein, the second switch tube M2 and the third switch tube M3 are both MOS tubes. It should be noted that in the embodiment of the present application, the first current mirror unit 112 can also be other types of current mirrors, not limited to the cascode current mirror in the present embodiment.

[0075] The first switch unit 113 may include a first NOT gate N1 and a fourth switch tube M4, wherein the input end of the first NOT gate N1 is used to receive a first switch control signal (which may be a demagnetization time signal , during the demagnetization time, =1, outside the demagnetization time, =0), the output end of the first NOT gate N1 is connected to the gate of the fourth switch tube M4, the first electrode of the fourth switch tube M4 is connected to the first end of the first energy storage module 130 (for example, the first capacitor C1), and the second electrode of the fourth switch tube M4 is connected to the first electrode of the third switch tube M3. The first switch control signal is a high-level signal during the demagnetization time and a low-level signal at other times. The first switch control signal is inverted by the first NOT gate N1 and output to the fourth switch tube M4. The fourth switch tube M4 responds to the inverted first switch control signal and is in a conducting state during the demagnetization time, so that the first charging current generated by the first current mirror unit 112 is transmitted to the first capacitor C1 to charge the first capacitor C1. Correspondingly, the fourth switch tube M4 responds to the inverted first switch control signal and is in a disconnected state at other times, and the first capacitor C1 stops charging.

[0076] Please continue to refer to FIG3 , in an exemplary embodiment, the second current module 120 includes a second current unit 121, a second current mirror unit 122 and a second switch unit 123. The second current unit 121 is used to receive the input voltage Vin and convert the input voltage Vin into a second initial charging current I02; wherein I02=K*Vin, K is a proportionality coefficient, and K is greater than 0.

[0077] The second current mirror unit 122 is connected to the second current unit 121, and is used to generate a second charging current I2 that is in mirror proportion to the second initial charging current I02. Exemplarily, the relationship between the second charging current and the second initial charging current can be expressed as: second charging current I2=b*second initial charging current I02. Wherein, b is the mirror proportional coefficient, and the proportional coefficient can be set according to demand. For example, b can be 1 or a positive number greater than 1. The mirror proportional coefficient in the embodiment of the present application is not limited. Exemplarily, the second current mirror unit 122 includes but is not limited to a simple current mirror, a common source and common gate current mirror, and a low-voltage common source and common gate current mirror. In the embodiment of the present application, the type of current mirror included in the second current mirror unit 122 is not specifically limited.

[0078] The second switch unit 123 is connected to the second current mirror unit 122, and is used to be in a conducting state during the conduction time (Ton=1) of the power tube to output the second charging current I2 to charge the second energy storage module 140. The second switch unit 123 can be in a conducting state in response to the second switch control signal during the conduction time (Ton=1) of the power tube to transmit the second charging current generated by the second current mirror unit 122 to the second energy storage module 140 to charge the second energy storage module 140. The second switch unit 123 can be in a disconnected state in response to the second switch control signal during the disconnection time (Ton=0) of the power tube to disconnect the charging path for the second charging current to be transmitted to the second energy storage module 140 to suspend charging the second energy storage module 140. In the embodiment of the present application, the second switch control signal can be selected as the conduction signal Ton, and the signal type of the second switch control signal can be determined according to the switch type included in the second switch unit 123. Exemplarily, the switch types of the switches in the second switch unit 123 include, but are not limited to, transistors, field effect transistors, electric knife switches, relays, thyristors, and the like.

[0079] As shown in FIG5 , in an exemplary embodiment, the second current unit 121 includes a first resistor R1, a second resistor R2, a second operational amplifier U2, a fifth switch tube M5 and a third resistor R3. The first resistor R1 is used to receive the input voltage Vin, the second end of the first resistor R1 is respectively connected to the second end of the second resistor R2 and the first input end (e.g., positive phase) of the second operational amplifier U2, the second end of the second resistor R2 is connected to the common potential end, the second input end (e.g., negative phase) of the second operational amplifier U2 is respectively connected to the first end of the third resistor R3 and the second end of the fifth switch tube M5, the output end of the second operational amplifier U2 is connected to the gate of the fifth switch tube M5, and the second end of the third resistor R3 is connected to the common potential end. The first resistor R1 and the second resistor R2 can form a voltage dividing unit, which can perform voltage dividing processing on the received input voltage Vin, and the voltage dividing signal of the voltage dividing processing can be input to the positive phase input end of the second operational amplifier U2. The second initial charging current I02 is negatively correlated with the resistance value of the third resistor R3 and positively correlated with the input voltage Vin.

[0080] Among them, the second current mirror unit 122 may include a sixth switch tube M6 and a seventh switch tube M7; wherein the sixth switch tube M6 and the seventh switch tube M7 may form a common source and common gate current mirror, and their specific connection relationship may refer to the first current mirror unit 112, which will not be repeated here.

[0081] The second switch unit 123 may include a second NOT gate N2 and an eighth switch tube M8. The connection relationship between the second NOT gate N2 and the eighth switch tube M8 may refer to the first switch unit 113, and will not be repeated here. It should be noted that the input end of the second NOT gate N2 may receive a second switch control signal. The second switch control signal is a high level signal during the conduction time and a low level signal outside the conduction time. That is, when Ton=1, the second switch control signal is, and when Ton=0, the second switch control signal is 0. The second switch control signal is inverted by the second NOT gate N2 and output to the eighth switch tube M8. The eighth switch tube M8 responds to the inverted second switch control signal and is in a conducting state when the conduction signal Ton=1, so that the second charging current generated by the second current mirror unit 122 is transmitted to the second capacitor C2 to charge the second capacitor C2. Accordingly, the eighth switch tube M8 responds to the inverted second switch control signal and is in a disconnected state when Ton=0, and the second capacitor C2 stops charging.

[0082] For the sake of convenience, the overvoltage protection circuit shown in FIG5 is applied to the switching power supply shown in FIG6 as an example for explanation. In the switching power supply shown in FIG6, the port receiving the input voltage Vin can be connected to the negative output terminal Vout- of the switching power supply, wherein the switching power supply can include a Buck circuit. It can be seen from the volt-second characteristic of the Buck circuit that:

[0083]

[0084] when When , it is determined to be output overvoltage protection, where, is the overvoltage protection threshold, which is a setting parameter and a fixed value. In this case, we have:

[0085]

[0086] in this way, , therefore, when When , the judgment module 150 outputs an overvoltage protection signal, OVP is "1", so when When , the signal OVP output by the judgment module 150 is "0".

[0087] According to the overvoltage protection circuit diagram shown in FIG5 above, the second voltage is calculated with the mirror ratio coefficient being 1. :

[0088]

[0089] From this we can deduce:

[0090]

[0091] Calculate the first voltage :

[0092]

[0093] From this we can deduce:

[0094]

[0095] when hour:

[0096]

[0097] From this we can deduce:

[0098]

[0099] make ;in, Depend on Parameters determine.

[0100] So, if , that is, When the judging module 150 is in the demagnetization time At the end of the judgment , then the overvoltage protection signal is output, OVP is "1". In this way, and Related to inductance This can avoid the inductance deviation of the inductor, resulting in When voltage changes occur, the accuracy of output overvoltage protection OVP can be improved.

[0101] In an exemplary embodiment, the specific circuit structure of the second current module 120 can be adaptively adjusted according to the switching power supply used. As shown in Figure 7, the second current module 120 may include a second current unit 121, a second current mirror unit 122, a third switch unit 124 and a first current source 125. Among them, the second current unit 121 is used to receive the input voltage Vin and convert the input voltage Vin into a second initial charging current I02; wherein I02=K*Vin, K is a proportional coefficient. The second current mirror unit 122 is electrically connected to the second current unit 121, and is used to generate a second mirror current Im that is in mirror proportion to the second initial charging current I02. In this embodiment, the structures of the second current unit 121 and the second current mirror unit 122 are the same as those in the aforementioned embodiment, and are not repeated here.

[0102] The second current mirror unit 122 is connected to the first current source 125 through the third switch unit 124, that is, the first current source 125 can be connected to the third switch unit 124. The first current source 125 can be used to generate a preset current Io proportional to the first initial charging current I01. The third switch unit 124 is used to be in a conducting state during the conduction time period (Ton=1) of the power tube to output the second charging current I2 to charge the second energy storage module 140; wherein the second charging current I2 is the difference between the second mirror current Im and the preset current Io, for example, I2=Im-Io. Correspondingly, the third switch unit 124 is used to be in a disconnected state during the non-conduction time (Ton=0) of the power tube N1 to stop charging the second energy storage module 140.

[0103] The second current module in the overvoltage protection circuit in this embodiment is different from the specific structure of the second current module in the previous embodiment, and can be applied to switching power supplies different from those in the previous embodiment. The overvoltage protection circuit in this embodiment can be applied to a power supply system as shown in FIG8 , in which the port of the input voltage Vin is electrically connected to the positive output terminal Vout+ of the switching power supply, as shown in FIG8 .

[0104] As shown in FIG9 , in an exemplary embodiment, the third switch unit 124 includes: a first switch 1241 and a second switch 1242; wherein the first end of the first switch 1241 is connected to the second current mirror unit 122, the second end of the first switch 1241 is connected to the first end of the second switch 1242, and the second end of the second switch 1242 is connected to the first current source 125; the first switch 1241 and the second switch 1242 are respectively in a conducting state during the conduction time period (Ton=1) of the power tube. Exemplarily, the first switch 1241 may include a second NOT gate N2 and an eighth switch tube M8, and the second switch 1242 includes a ninth switch tube M9. The input end of the second NOT gate N2 is connected to the gate of the ninth switch tube M9 for receiving the third switch control signal, the output end of the second NOT gate N2 is connected to the gate of the eighth switch tube M8, the second electrode of the eighth switch tube M8 is connected to the second current mirror unit 122, the first electrode of the eighth switch tube M8 is respectively connected to the first electrode of the ninth switch tube M9 and the first end of the second capacitor C2, the second electrode of the ninth switch tube M9 is connected to the common potential end, and the gate of the ninth switch tube M9 is connected to the first current source 125. The third switch control signal can be selected as the conduction signal of the power tube N1, that is, the Ton signal. When the power tube is turned on, Ton=1, and when the power tube is turned off, Ton=0. The third switch control signal is inverted by the second NOT gate N2 and output to the eighth switch tube M8. The eighth switch tube M8 responds to the inverted third switch control signal and is in a conduction state during the conduction time (Ton=1) to output the second mirror current Im generated by the third current mirror unit. At the same time, the ninth switch tube M9 responds to the third switch control signal and is in the on state during the on time (Ton=1) to output the preset current Io generated by the first current source 125, wherein the second mirror current Im and the preset current Io are in opposite directions, and the current at the second end of the first capacitor C1 is the second charging current (Im-Io), that is, the second charging current (Im-Io) can be used to charge the second capacitor C2 during the on time (Ton=1).

[0105] In an exemplary embodiment, please continue to refer to FIG. 9 , the first current source 125 includes a third current mirror unit. Exemplarily, the third current mirror unit may include: a tenth switch tube M10, an eleventh switch tube M11, and a twelfth switch tube M12. Among them, the gate of the tenth switch tube M10 is connected to the gate of the eleventh switch tube M11, the first electrode of the tenth switch tube M10 is connected to the second switch 1242, and the second electrode of the tenth switch tube M10 is connected to the common potential end; the first electrode of the eleventh switch tube M11 is connected to the first electrode of the twelfth switch tube M12, and the second electrode of the eleventh switch tube M11 is connected to the common potential end; the second electrode of the twelfth switch tube M12 is used to receive a preset voltage VDD, and the gate of the twelfth switch tube M12 is connected to the first current mirror unit 112 in the first current module 110. In the embodiment of the present application, the specific current mirror structure of the third current mirror unit is not limited to the above-mentioned example, and other types of current mirror structures can also be used.

[0106] For the sake of convenience, the overvoltage protection circuit shown in FIG9 is applied to the switching power supply shown in FIG8 as an example for explanation. Among them, the switching power supply shown in FIG8 may include a Buck circuit. It can be known from the volt-second characteristic of the Buck circuit that:

[0107]

[0108] From this we can deduce:

[0109]

[0110] when When , it is determined to be output overvoltage protection, where, is the overvoltage protection threshold, which is a setting parameter and a fixed value. In this case, we have:

[0111]

[0112] in this way, Therefore, the circuit can be designed to achieve When the overvoltage protection signal is output, OVP is "1", so when When the OVP is “0”.

[0113] According to the overvoltage protection circuit shown in FIG. 9 , the second voltage is calculated by taking the mirror ratio coefficient as 1. :

[0114]

[0115] ;

[0116] Calculate the first voltage :

[0117]

[0118]

[0119] when When the comparator outputs "1",

[0120]

[0121]

[0122] For the sake of explanation, we can use , , the above formula can be simplified to:

[0123] ;

[0124] make ,in, Voltage from Parameters determine.

[0125] The above formula can be simplified to:

[0126]

[0127] therefore, .

[0128] So, if The determination module 150 may be configured to determine when the demagnetization time is over ( jumps to low) output overvoltage protection signal, OVP is "1", it is judged as output overvoltage. and Related to inductance This can avoid the inductance deviation of the inductor, resulting in When voltage changes occur, the accuracy of output overvoltage protection OVP can be improved.

[0129] As shown in FIG. 10 , in an exemplary embodiment, the judgment module 150 includes a comparison unit 151 and a latch unit 152. The comparison unit 151 is used to compare the first voltage and the second voltage and output a comparison signal. The first input terminal of the comparison unit 151 is connected to the first energy storage module 130 to receive the first voltage; the second input terminal of the comparison unit 151 is connected to the first energy storage module 130 to receive the second voltage, and the output terminal of the comparison unit 151 is connected to the latch unit 152. The comparison unit 151 can compare the received first voltage and the second voltage, and output the comparison signal to the latch unit 152 through the output terminal of the comparison unit 151. The comparison signal includes a first comparison signal and a second comparison signal. The first comparison signal is output when the second voltage is greater than the first voltage, and the second comparison signal is output when the second voltage is less than or equal to the first voltage. One of the first input terminal and the second input terminal of the comparison unit 151 is a positive input terminal, and the other of the first input terminal and the second input terminal of the comparison unit 151 is a negative input terminal.

[0130] The latch unit 152 may be configured to lock the degaussing time at the end of the degaussing time ( The latch unit 152 jumps to low) and latches the comparison signal it receives. For example, if the latch unit 152 receives the first comparison signal, it can output an overvoltage protection signal at the end of the demagnetization time. If the latch unit 152 receives the second comparison signal, it can output a non-overvoltage protection signal (e.g., "0") at the end of the demagnetization time.

[0131] Please continue to refer to Figure 10. In an exemplary embodiment, the comparison unit 151 may include a comparator U3, and the latch unit 152 may include a D flip-flop 1521, a fourth NOT gate N4, and a fifth NOT gate N5. Among them, the positive phase input terminal of the comparator U3 is connected to the second energy storage module 140, the negative phase input terminal of the comparator U3 is connected to the first energy storage module 130, and the output terminal of the comparator U3 is connected to the data terminal D of the D flip-flop 1521. When the second voltage is greater than the first voltage, the comparator U3 may output a first comparison signal (for example, a high level signal "1") to the data terminal D of the D flip-flop 1521; when the second voltage is equal to or greater than the first voltage, the comparator U3 may output a second comparison signal (for example, a low level signal "0") to the data terminal D of the D flip-flop 1521. The input terminal of the fourth NOT gate N4 is used to receive a demagnetization signal , the output end of the fourth NOT gate N4 is connected to the clock end of the D flip-flop 1521. The input end of the fifth NOT gate N5 is used to receive the conduction signal Ton, and the output end of the fifth NOT gate N5 is connected to the reset end R of the D flip-flop 1521. When the reset end R of the D flip-flop 1521 receives a low-level signal, the D flip-flop 1521 outputs a low-level signal. When the reset end R of the D flip-flop 1521 receives a high-level signal, the D flip-flop 1521 is enabled, and the output end of the D flip-flop 1521 can be changed based on the signals received by the data end D and the clock end CLK. If the clock end CLK receives a rising edge signal (i.e., a demagnetization signal The falling edge of the data terminal is the trigger, and the trigger will output the comparison signal received by the data terminal. For example, the data terminal D is the first comparison signal, such as a high level signal "1". When the clock terminal CLK receives a rising edge signal, its D trigger 1521 outputs an overvoltage protection signal, such as "1".

[0132] Optionally, in the embodiment of the present application, the circuit structure of the latch unit 152 can be changed so that the clock terminal CLK receives a falling edge signal (or a demagnetization signal). The trigger takes the comparison signal received at the data end as output.

[0133] Optionally, in the embodiment of the present application, different types of triggers may be used to replace the D trigger 1521 in the aforementioned embodiment, and different triggers may be designed with different logic circuits to implement the same function of the latch unit 152. For example, the D trigger 1521 in the aforementioned embodiment is a trigger whose reset terminal R is reset when a low-level signal is applied, and it may be replaced by a trigger whose reset terminal R is reset when a high-level signal is applied. In this case, the fifth NOT gate N5 may be omitted.

[0134] In this application, by setting the comparison unit and the latch unit, during the off time of the switch tube (Ton=1), at the end of the demagnetization time ( jumps to low), its clock signal jumps to a high level signal, and when the comparator U3 detects that the second voltage is greater than the first voltage, the trigger will output an overvoltage protection signal, such as a high level signal "1".

[0135] As shown in FIG. 11 , in an exemplary embodiment, based on any of the above embodiments, the overvoltage protection circuit further includes a reset module 160. The reset module 160 can be used to discharge the first energy storage module 130 and the second energy storage module 140 after the demagnetization is completed, so as to reset the first energy storage module 130 and the second energy storage module 140. In the embodiment of the present application, the overvoltage detection cycle also includes a demagnetization end delay time T3, wherein after the demagnetization time of the overvoltage detection cycle is completed ( =0), and you can also set the demagnetization end delay time The reset module 160 may be used to discharge the first energy storage module 130 and the second energy storage module 140 during the demagnetization end delay time T3 to reset the first energy storage module 130 and the second energy storage module 140 .

[0136] The reset module 160 includes a first reset unit 161 and a second reset unit 162. The first end of the first reset unit 161 is connected to the first energy storage module 130, and the second end of the first reset unit 161 is connected to the common point end. The first reset unit 161 can respond to the first reset signal at the end of the demagnetization delay time T3. , so as to conduct the discharge path between the first end of the first energy storage module and the common point end, and discharge the electric energy stored in the first energy storage module 130 to reset the first energy storage module 130. The first end of the second reset unit 162 is connected to the second energy storage module 140, and the second end of the second reset unit 162 is connected to the common point end. The second reset unit 162 can be reset during the demagnetization end delay time. In response to the second reset signal , the discharge path between the first end of the second storage module and the common point end is turned on, and the electric energy stored in the second energy storage module 140 can be discharged to reset the second energy storage module 140. Exemplarily, the first reset unit 161 and the second reset unit 162 can respectively include a reset switch. The reset switch can be set to the reset state after the demagnetization end delay time. In the on state, the first energy storage module 130 and the second energy storage module 140 are discharged to reset the first energy storage module 130 and the second energy storage module 140. Among them, the switch type of the reset switch includes but is not limited to a transistor, a field effect tube, an electric knife switch, a relay, a thyristor, etc. Exemplarily, the first reset unit 161 includes a first reset MOS tube M13, and the second reset unit 162 includes a second reset MOS tube M13. The first reset MOS tube M13 and the second reset MOS tube M13 are both NMOS tubes. The first reset MOS tube M13 and the second reset MOS tube M14 can be turned on in response to a reset signal with a high level.

[0137] In this embodiment, by setting the reset module 160, the demagnetization end delay time can be set. The first energy storage module 130 and the second energy storage module 140 are discharged to achieve the reset processing of the first energy storage module 130 and the second energy storage module 140, and then the first voltage and the second voltage can be reset. In the next protection detection cycle, the accurate first voltage and the second voltage are obtained, which can improve the judgment accuracy of overvoltage protection in different protection detection cycles, avoid false triggering of overvoltage protection, and achieve safe and reliable OVP detection protection.

[0138] The embodiment of the present application also provides a driver chip, which may include the overvoltage protection circuit in any of the above embodiments. The driver chip of the present application includes a first current module 110, a second current module 120, a first energy storage module 130, a second energy storage module 140 and a judgment module 150. The first current module 110 can generate a first charging current to charge the first energy storage module during the demagnetization time, and the second current module 120 can generate a second charging current based on the input voltage Vin during the conduction time to charge the second energy storage module 140. The judgment module 150 can determine whether the second voltage of the second energy storage module 140 is greater than the first voltage of the first energy storage module 130 at the end of the demagnetization time, and output an overvoltage protection signal when the second voltage is greater than the first voltage. The overvoltage protection trigger threshold is related to the inductance. This can avoid the situation where the inductor has deviations in production, which will lead to deviations in the judgment of overvoltage protection. It can also avoid false triggering of overvoltage protection, achieve safe and reliable OVP detection protection, and ensure high accuracy.

[0139] As shown in FIG. 6 and FIG. 8 , an embodiment of the present application further provides a switching power supply, which may include the aforementioned driving chip or the overvoltage protection circuit in any of the aforementioned embodiments.

[0140] Optionally, the switching power supply may further include a capacitor CL, a resistor RL, an inductor L1 and a diode D1. The capacitor CL and the resistor RL are connected in parallel, the second end of the capacitor CL, the second end of the resistor RL and the cathode of the diode D1 are respectively connected to the positive output terminal VOUT+ of the switching power supply, the first end of the capacitor CL and the first end of the resistor RL are respectively connected to the negative output terminal VOUT- of the switching power supply, the anode of the diode D1 is respectively connected to the drain of the power switch tube and the first end of the inductor L1, and the second end of the inductor L1 is connected to the capacitor CL.

[0141] The switching power supply provided in the embodiment of the present application includes a first current module 110, a second current module 120, a first energy storage module 130, a second energy storage module 140 and a judgment module 150. The first current module 110 can generate a first charging current to charge the first energy storage module during the demagnetization time, and the second current module 120 can generate a second charging current based on the input voltage Vin during the conduction time to charge the second energy storage module 140. The judgment module 150 can judge whether the second voltage of the second energy storage module 140 is greater than the first voltage of the first energy storage module 130 at the end of the demagnetization time, and output an overvoltage protection signal when the second voltage is greater than the first voltage. The overvoltage protection triggering threshold is related to the first charging current and the second charging current, and is not related to the inductance. This can avoid the situation where the inductor has deviations in production, which will lead to deviations in the judgment of overvoltage protection. It can also avoid false triggering of overvoltage protection, achieve safe and reliable OVP detection protection, and ensure high accuracy.

[0142] In the description of this specification, the description with reference to the terms "some embodiments", "other embodiments", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic description of the above terms does not necessarily refer to the same embodiment or example.

[0143] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0144] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. An overvoltage protection circuit, characterized in that: include: A first current module, a second current module, a first energy storage module, a second energy storage module and a judgment module; a first current module, electrically connected to the first energy storage module, and configured to output a first charging current I1 within a demagnetization time to charge the first energy storage module; A second current module, electrically connected to the second energy storage module, and configured to output a second charging current I2 positively correlated with the input voltage Vin during the conduction time of the power tube to charge the second energy storage module; The judgment module is electrically connected to the first energy storage module and the second energy storage module respectively, and is used to judge whether the second voltage of the second energy storage module is greater than the first voltage of the first energy storage module when demagnetization is completed, and output an overvoltage protection signal when the second voltage is greater than the first voltage.

2. The overvoltage protection circuit according to claim 1, characterized in that: The judging module comprises: A comparison unit, configured to compare the first voltage and the second voltage and output a comparison signal; The latch unit is connected to the output end of the comparison unit and is used to latch the comparison signal when the demagnetization is completed.

3. The overvoltage protection circuit according to claim 1, characterized in that: The overvoltage protection circuit further includes: A reset module is used to discharge the first energy storage module and the second energy storage module after demagnetization is completed, so as to reset the first energy storage module and the second energy storage module.

4. The overvoltage protection circuit according to any one of claims 1 to 3, characterized in that: The first current module comprises: A first current unit, used to generate a first initial charging current I01; A first current mirror unit, connected to the first current unit, and configured to generate the first charging current I1 in mirror proportion to the first initial charging current I01; The first switch unit is connected to the first current mirror unit, and is configured to be in a conducting state during the demagnetization time to output the first charging current I1 to charge the first energy storage module.

5. The overvoltage protection circuit according to claim 4, characterized in that: The second current module comprises: A second current unit, used for receiving the input voltage Vin, and converting the input voltage Vin into a second initial charging current I02; wherein I02=K*Vin, K is a proportionality coefficient; A second current mirror unit, connected to the second current unit, and configured to generate the second charging current I2 in mirror proportion to the second initial charging current I02; The second switch unit is connected to the second current mirror unit, and is used to be in a conducting state during the conduction time of the power tube to output the second charging current I2 to charge the second energy storage module.

6. The overvoltage protection circuit according to claim 4, characterized in that: The second current module comprises: A second current unit, used for receiving the input voltage Vin, and converting the input voltage Vin into a second initial charging current I02; wherein I02=K*Vin, K is a proportionality coefficient; A second current mirror unit, electrically connected to the second current unit, and configured to generate a second mirror current Im in mirror proportion to the second initial charging current I02; A first current source, used to generate a preset current Io proportional to the first initial charging current I01; The third switch unit is electrically connected to the first current source, and is used to be in a conducting state during the conduction period of the power tube to output the second charging current I2 to charge the second energy storage module; wherein I2=Im-Io.

7. The overvoltage protection circuit according to claim 6, characterized in that: The third switch unit includes: a first switch and a second switch; wherein the first end of the first switch is connected to the second current mirror unit, the second end of the first switch is connected to the first end of the second switch, and the second end of the second switch is connected to the first current source; the first switch and the second switch are respectively in a conducting state during the conduction time period of the power tube.

8. The overvoltage protection circuit according to claim 6, characterized in that: The first current source comprises: a third current mirror unit; The third current mirror unit is used to output the preset current Io in mirror proportion to the first initial charging current I01.

9. A driver chip, characterized in that: Comprising the overvoltage protection circuit as described in any one of claims 1-8.

10. A switching power supply, characterized in that: Comprising the driving chip as claimed in claim 9.

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