CN114337235B - Power supply capable of preventing surge and lightning strike and power supply control method - Google Patents
Power supply capable of preventing surge and lightning strike and power supply control method Download PDFInfo
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- CN114337235B CN114337235B CN202111415320.XA CN202111415320A CN114337235B CN 114337235 B CN114337235 B CN 114337235B CN 202111415320 A CN202111415320 A CN 202111415320A CN 114337235 B CN114337235 B CN 114337235B
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
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Abstract
The embodiment of the application discloses a power supply capable of preventing surge and lightning strike and a control method of the power supply, and relates to the power electronic technology. The power supply includes a power factor correction circuit, a protection circuit, and a controller. The protection circuit comprises a lightning protection diode and a current detection unit. The lightning protection diode is used for conducting under the condition of surge lightning strike, and transmitting current generated by the surge lightning strike to an output circuit of the power supply. The current detection unit is used for detecting the current passing through the lightning protection diode under the condition of surge lightning strike. The power factor correction circuit is used for correcting the power factor of the power supply and comprises a power factor inductor and a switching tube. One end of the power factor inductor is connected with an input circuit of the power supply, and the other end of the power factor inductor is connected with the switching tube. The controller is used for controlling the conduction state of the switching tube according to the current passing through the lightning protection diode.
Description
Technical Field
The embodiment of the application relates to a power electronic technology, in particular to a power supply capable of preventing surge and lightning strike and a power supply control method.
Background
The power supply is typically composed of an input circuit, an electromagnetic compatibility (electro magnetic compatibility, EMC) circuit, a power factor correction (power factor correction, PFC) circuit, a direct current conversion circuit, and a control circuit. Wherein the EMC circuit is used to ensure that the power supply is operating properly in an electromagnetic environment and does not create intolerable electromagnetic interference to any device in the battery system. The PFC circuit is used for correcting the power factor of the power supply and improving the power utilization efficiency of the power supply. The PFC circuit generally includes components such as PFC inductors and MOS transistors.
When the power supply is in a lightning environment, it may be struck by lightning. The lightning current/voltage firstly passes through the input circuit and the EMC circuit and then passes through the PFC circuit, so that the voltage of the bus capacitor for externally supplying power is finally increased. A large instantaneous current/voltage is generated due to a lightning strike. Without a corresponding protection circuit, various switching tubes in the power supply are likely to be damaged, ultimately resulting in power failure.
In the prior art, a lightning protection diode is adopted to protect a switching tube in a circuit, the lightning protection diode is in an off state under the condition of no lightning stroke, the lightning protection diode is conducted when the lightning stroke is received, at the moment, a part of voltage generated by the lightning stroke is directly added to two ends of a bus capacitor through the lightning protection diode to play a role in protecting other module components, and the other part of voltage is added to two ends of the bus capacitor through a PFC inductor and an MOS tube in the PFC circuit. This will likely lead to excessive voltage breakdown of the MOS transistor in the PFC circuit, causing damage to the MOS transistor in the PFC circuit, and eventually leading to power failure. Therefore, how to protect the MOS transistor in the PFC circuit to protect the power supply safety becomes a problem to be solved.
Disclosure of Invention
The embodiment of the application provides a power supply capable of preventing surge and lightning stroke and a power supply control method, wherein a current detection unit is used for obtaining current passing through a lightning protection diode and controlling the conduction state of an MOS (metal oxide semiconductor) tube in a PFC (power factor correction) circuit according to the obtained current of the lightning protection diode so as to achieve the purpose of protecting the MOS tube.
A first aspect of an embodiment of the present application provides a power supply for protecting against a surge lightning strike, including:
the power supply consists of an input circuit, a power factor correction circuit, a protection circuit, a controller and an output circuit. The power factor correction circuit consists of a power factor inductor and a switching tube and is used for correcting the power factor and improving the electric energy conversion efficiency. One end of the power factor inductor is connected with the input circuit, and the other end of the power factor inductor is connected with the switching tube. The protection circuit plays a role in circuit protection and comprises a lightning protection diode and a current detection unit. When the power supply works normally, the lightning protection diode in the protection circuit is disconnected and does not work. The direct current provided by the input circuit is corrected by the power factor correction circuit, and then stable direct current is output to the outside. When the power supply is struck by lightning, the lightning protection diode is conducted, and a part of surge voltage generated by the lightning is transmitted to an output circuit of the power supply through the lightning protection diode. The other part will pass through the pfc circuit into the output circuit. In this case, if the surge voltage is too large, there is a high possibility that the switching tube in the power factor correction circuit breaks down, causing damage to the switching tube, and thus the power supply cannot normally supply power to the outside. Accordingly, the current passing through the lightning protection diode can be detected by the current detection unit, and the on state of the switching tube in the power factor correction circuit can be controlled by the current value of the current passing through the lightning protection diode. When the current value of the current passing through the lightning protection diode is overlarge, the overlarge surge voltage generated by lightning stroke can be determined, and then a switching tube in the power factor correction circuit can be turned off in time according to the determination result, so that the effect of protecting the switching tube is achieved.
In the above power supply, the current passing through the lightning protection diode is detected by the current detection unit, and then the on state of the switching tube in the power factor correction circuit is controlled according to the current passing through the lightning protection diode. Therefore, when the surge voltage generated after the power supply is struck by lightning is overlarge, the switching tube can be turned off timely, the switching tube is protected more quickly and efficiently, and the phenomenon that the switching tube is broken down due to overlarge instantaneous voltage is avoided. Thereby protecting the safety of the power supply and ensuring the normal work of the power supply and the service life of the power supply.
In an alternative embodiment, the current detection unit may feed back the detected current value to the controller of the power supply when the current is detected. After the controller determines that the current passing through the lightning protection diode exceeds the preset current threshold, the fact that the surge voltage generated by lightning stroke is likely to cause damage to components is indicated, so that a switching tube in the power factor correction circuit needs to be controlled to be turned off, and the situation that the switching tube is broken down is avoided. Thereby ensuring the normal work of the power factor correction circuit and ensuring the normal power supply of the power supply.
In an alternative embodiment, the current detection unit may be composed of a sampling element, a voltage comparator, a reverse diode, and a field effect MOS transistor. One end of the sampling element is connected with the input end of the voltage comparator, and the other end of the sampling element is grounded. The sampling element is used for converting the current passing through the lightning protection diode into a voltage signal and inputting the voltage signal into the voltage comparator. Then the output end of the voltage comparator is connected with one end of the reverse diode, and the other end of the reverse diode is connected with the grid electrode of the MOS tube. One end of the voltage comparator is input with a voltage signal corresponding to the sampling element, the other end of the voltage comparator is input with a preset voltage signal, when the voltage signal corresponding to the sampling element is larger than the preset voltage signal, the voltage comparator outputs a low-level signal, at the moment, the reverse diode is conducted, the grid electrode of the MOS tube is in a low level, and the drain electrode of the output end outputs a high-level signal. The high-level signal is fed back to the controller, and the controller controls a switching tube in the PFC circuit to be turned off after receiving the high-level signal.
In this embodiment, the current detection unit uses a voltage comparator to determine the control signal to turn off the switching tube. Therefore, the switching tube in the PFC circuit can be controlled to be turned off more accurately by flexibly adjusting the value of the preset voltage.
In an alternative embodiment, the current detection unit comprises two voltage comparators. This is because there may be two current directions of the current through the lightning protection diode, and thus two voltage comparators are required to determine the magnitudes of the currents in different directions. The first end of the sampling element is connected with the positive input end of the first voltage comparator through the first resistor, and the first end of the sampling element is connected with the negative input end of the second voltage comparator through the third resistor. When the voltage at two ends of the sampling element is negative voltage, the first voltage comparator is used for comparing the magnitude of the negative voltage with the magnitude of a preset voltage value, and if the absolute value of the negative voltage is larger than the preset voltage value, the first voltage comparator outputs a low-level signal. When the voltage at two ends of the sampling element is positive voltage, the second voltage comparator is used for comparing the positive voltage with a preset voltage value, and if the absolute value of the positive voltage is larger than the preset voltage value, the second voltage comparator outputs a low-level signal.
In an alternative embodiment, the first voltage comparator corresponds to a positive voltage source and the second resistor, and the second voltage comparator corresponds to a negative voltage source and the fourth resistor. One end of the second resistor is connected with the positive voltage source, and the other end of the second resistor is connected with the positive input end of the first voltage comparator. One end of the fourth resistor is connected with a negative voltage source, and the other end of the fourth resistor is connected with the negative input end of the second voltage comparator. The first preset voltage value input by the first voltage comparator can be adjusted by changing the resistance values of the first resistor and the second resistor. By changing the resistance values of the third resistor and the fourth resistor, the second preset voltage value input by the second voltage comparator can be adjusted.
In an alternative embodiment, the first voltage comparator outputs the low signal when it determines that the absolute value of the negative voltage across the sampling element is greater than a first predetermined voltage value. When the second voltage comparator determines that the absolute value of the positive voltage across the sampling element is greater than a second preset voltage value, a low level signal is output. Then, the low-level signal can enable the MOS tube to output a high-level signal and feed the high-level signal back to the controller, and the controller controls the switching tube in the PFC circuit to be turned off according to the high-level signal.
In an alternative embodiment, the power supply further comprises a rectifying circuit. When the surge lightning stroke occurs, the voltage generated by the lightning stroke is transmitted to the output circuit through the lightning protection diode, when the surge lightning stroke does not occur, the rectification circuit converts alternating current provided by the input circuit into direct current, then the direct current is provided for the power factor correction circuit to carry out power factor correction, and finally stable direct current is output to provide electric energy for the outside.
In an alternative embodiment, the power supply further comprises a drive circuit, the drive circuit being directly connected to the controller. When the controller receives the high-level signal, an instruction can be sent to the driving circuit, and the driving circuit drives a switching tube in the power factor correction circuit to be turned off according to the instruction.
In an alternative embodiment, the sampling element in the current detection unit may be a sampling resistor, a sampling inductor or a sampling current transformer, which is not particularly limited.
The second aspect of the embodiment of the application provides a power supply control method for preventing surge lightning strike, which comprises the following steps:
the controller obtains the current passing through the lightning protection diode in the protection circuit, and then controls the conduction state of a switching tube included in the power factor correction circuit according to the current passing through the lightning protection diode.
The power supply comprises a power factor correction circuit, a protection circuit and a controller.
The protection circuit comprises a lightning protection diode and a current detection unit. The lightning protection diode is used for conducting under the condition of surge lightning strike, and transmitting current generated by the surge lightning strike to an output circuit of the power supply. The current detection unit is used for detecting the current passing through the lightning protection diode under the condition of surge lightning strike. The power factor correction circuit is used for correcting the power factor of the power supply and comprises a power factor inductor and a switching tube. One end of the power factor inductor is connected with an input circuit of the power supply, and the other end of the power factor inductor is connected with the switching tube.
In an alternative embodiment, the controller determines that the current through the lightning protection diode exceeds a preset current threshold, and controls the switching tube to be turned off according to the determination result.
In an alternative embodiment, the current detection unit includes a sampling element, a voltage comparator, a reverse diode, and a field effect MOS transistor. The first end of the sampling element is connected with the input end of the voltage comparator, and the second end of the sampling element is grounded. The output end of the voltage comparator is connected with one end of the reverse diode, and the other end of the reverse diode is connected with the grid electrode of the MOS tube.
The sampling element is used for converting current corresponding to the lightning protection diode into voltage. The voltage comparator is used for determining that the voltage at two ends of the sampling element is larger than a preset voltage value and outputting a low-level signal. The reverse diode is used for conducting a low-level signal. The MOS tube is used for outputting a high-level signal to the control module according to the low-level signal. And then the controller controls the switching tube to be turned off according to the high-level signal.
In an alternative embodiment, the voltage comparator comprises a first voltage comparator and a second voltage comparator. The first end of the sampling element is connected with the positive input end of the first voltage comparator through the first resistor. The first end of the sampling element is connected with the negative input end of the second voltage comparator through a third resistor. The first voltage comparator is used for outputting a low-level signal according to the negative voltage at two ends of the sampling element. The second voltage comparator is used for outputting a low-level signal according to the positive voltage at two ends of the sampling element.
In an alternative embodiment, the first voltage comparator corresponds to a positive voltage source and the second resistor, and the second voltage comparator corresponds to a negative voltage source and the fourth resistor. One end of the second resistor is connected with the positive voltage source, and the other end of the second resistor is connected with the positive input end of the first voltage comparator. One end of the fourth resistor is connected with a negative voltage source, and the other end of the fourth resistor is connected with the negative input end of the second voltage comparator.
The resistance values of the first resistor and the second resistor are used for adjusting a first preset voltage value. The resistance values of the third resistor and the fourth resistor are used for adjusting the second preset voltage value.
In an alternative embodiment, the first voltage comparator is configured to determine that an absolute value of the negative voltage across the sampling element is greater than a first preset voltage value, and output a low level signal. The second voltage comparator is used for determining that the absolute value of the positive voltage at two ends of the sampling element is larger than a second preset voltage value and outputting a low-level signal.
In an alternative embodiment, the power supply further comprises a rectifying circuit. The rectification circuit is used for converting alternating current provided by an input circuit of the power supply under the condition of no surge lightning strike into direct current and providing the direct current to the power factor correction circuit.
In an alternative embodiment, the power supply further comprises a drive circuit, the drive circuit being coupled to the controller. The driving circuit is used for driving the switching tube to be turned on or turned off according to the instruction of the controller.
In an alternative embodiment, the sampling element comprises a sampling resistor, a sampling inductance or a sampling current transformer.
In the above power protection method, the controller controls the current detection unit to detect the current passing through the lightning protection diode, and then controls the on state of the switching tube in the power factor correction circuit according to the current passing through the lightning protection diode. Therefore, when the surge voltage generated after the power supply is struck by lightning is overlarge, the switching tube can be turned off timely, the switching tube is protected more quickly and efficiently, and the phenomenon that the switching tube is broken down due to overlarge instantaneous voltage is avoided. Thereby protecting the safety of the power supply and ensuring the normal work of the power supply and the service life of the power supply.
Drawings
Fig. 1 is a schematic diagram of a power supply device according to an embodiment of the present application;
fig. 2 is a schematic structural diagram of a power supply according to an embodiment of the present application;
FIG. 3 is a schematic diagram of another power supply according to an embodiment of the present application;
FIG. 4 is a schematic structural diagram of a power supply for preventing surge lightning according to an embodiment of the present application;
fig. 5 is a schematic structural diagram of a current detection circuit according to an embodiment of the present application;
fig. 6 is a schematic flow chart of a power supply control method for preventing surge lightning strike according to an embodiment of the application.
Detailed Description
The embodiment of the application provides a power supply capable of preventing surge and lightning stroke and a protection method of the power supply, wherein a current detection unit is used for acquiring current passing through a lightning protection diode, and the conducting state of an MOS (metal oxide semiconductor) tube in a PFC (power factor correction) circuit is controlled according to the acquired current of the lightning protection diode so as to achieve the purpose of protecting the MOS tube.
A power supply is a device that converts other forms of energy into electrical energy and provides the electrical energy to an electronic device or circuit. In general, a power supply is generally composed of an input circuit, an electromagnetic compatibility EMC circuit, a power factor correction PFC circuit, a direct current-to-direct current DC-DC circuit, and a control circuit. Fig. 1 is a schematic diagram of a power supply device according to an embodiment of the present application. As shown in fig. 1, the input circuit is configured to receive ac power provided by an external system (e.g., a power supply system) and convert the ac power into dc power. The direct current eliminates electromagnetic interference through an EMC circuit, and then after the PFC circuit corrects the power factor, the direct current is output to a DC-DC circuit stably and continuously. Then, the DC-DC circuit can convert the direct current into charging direct current required by the device to be charged, and the charging process of the device to be charged is realized.
The following is a brief description of a PFC circuit. The power factor refers to the ratio of the effective power to the total power consumption in the power supply system, and is used to measure the degree to which the power is effectively utilized. The larger the value of the power factor, the higher the power conversion efficiency representing the power supply. Since the power supply is generally a capacitor input type circuit, a phase difference between a voltage and a current thereof may seriously affect a value of effective power, a PFC circuit is required to improve a power factor.
Generally, PFC circuits can be classified into passive PFC circuits and active PFC circuits. The passive PFC circuit may be further classified into an "inductance compensation type" and a "valley-fill circuit type". The "inductance compensation" is to increase the power factor by reducing the phase difference between the fundamental current and the voltage of the ac input, and generally only the power factor of the power supply can reach 0.7 to 0.8. The 'valley filling circuit' belongs to a novel passive power factor correction circuit, the conduction angle of a rectifying tube is greatly increased by utilizing a valley filling circuit behind the rectifying circuit, and the input current is changed into a waveform close to a sine wave from a spike pulse by filling a valley point, so that the power factor can be improved to about 0.9. The active PFC circuit consists of a capacitor inductor and an electronic element, is small in size, and adjusts the waveform of current through a special IC to compensate the phase difference between current and voltage, so that the power supply achieves a higher power factor.
Fig. 2 is a schematic structural diagram of a power supply according to an embodiment of the present application. In fig. 2, AC is an alternating current input source, and diodes are used for rectification. The PFC circuit is composed of a PFC inductor L and two switching transistors (MOS transistors). The bus capacitor is used for storing electric energy and is used as an input of the next-stage DC-DC circuit to provide stable continuous direct current for the next-stage DC-DC circuit. Specifically, when the alternating current provided by the AC is positive, the MOS transistor 1 is turned on, and the MOS transistor 2 is turned off. The current flows into the MOS tube 1 through the PFC inductor L, and charges the bus capacitor through the drain electrode of the MOS tube 1, and the voltages at two ends of the bus capacitor are positive and negative. When the alternating current provided by the AC is negative, the MOS tube 1 is turned off, and the MOS tube 2 is turned on. The current flows into the MOS tube 2 through the PFC inductor, and then returns to the AC through the diode 2 by the MOS tube 2, and the bus capacitor is not charged at the moment. Therefore, the voltage across the bus capacitor is always positive, providing direct current for the next stage DC-DC circuit.
In the above power supply structure, if the power supply receives a lightning strike, an excessive surge voltage may be generated. The surge voltage refers to an instantaneous overvoltage generated by lightning strike. The surge voltage can cause that a great voltage difference is generated between the drain electrode and the source electrode of two MOS tubes in the PFC circuit, the MOS tubes are likely to be broken down, the MOS tubes are damaged, the power supply is finally damaged, and the normal work cannot be performed. To protect the power supply from damage after lightning strikes, lightning protection diodes are often used to protect the power supply. Fig. 3 is a schematic structural diagram of another power supply provided in the embodiment of the present application, as shown in fig. 3, in the power supply structure, compared with the power supply structure shown in fig. 2, two lightning protection diodes are connected between AC and PFC inductor L, wherein the positive electrode of one of the lightning protection caps is connected with AC, and the negative electrode of the other lightning protection cap is connected with AC.
The lightning protection diode is in an off state when the lightning protection diode is not struck by lightning normally, and the whole power supply system is not affected. When the power supply is struck by lightning, the lightning protection diode is in an operating state, and if the positive electrode is connected with a high level, the lightning protection diode is conducted. Thus, in fig. 3, if the power supply is struck by lightning, the lightning protection diode 1 will be in a conducting state if the generated surge voltage is a positive voltage. At this time, a part of the surge current will charge the bus capacitor through the lightning protection diode 1. The other part of surge current enters the MOS tube 1 through the PFC inductor L in the PFC circuit, and then charges the bus capacitor through the MOS tube 1. Since the PFC inductor has the effect of blocking the current variation, the current flowing into the MOS transistor 1 will lag behind the current flowing into the lightning protection diode.
It can be appreciated that if the surge voltage is too large, damage to the MOS transistor is likely to occur. In the prior art, the voltage values at two ends of a bus capacitor or the current value passing through a PFC inductor are detected generally and then compared with a protection threshold value, and if the voltage values at two ends of the bus capacitor or the current value passing through the PFC inductor are larger than a certain threshold value, the fact that surge voltage generated by lightning stroke is overlarge is indicated, so that the working state of an MOS tube in the PFC circuit is controlled, and the PFC circuit is protected. However, the voltage change across the bus capacitor is lagging, and the inductor has the effect of blocking the current change, and the change is lagging, which is likely to cause the voltage value across the bus capacitor or the current value through the PFC inductor to have not risen beyond the protection threshold, and the voltage difference across the drain and source of the MOS transistor is too large. Because the speed of detection and protection is too slow, the PFC circuit cannot be effectively protected in time in the prior art, and finally, the power supply is disabled.
Based on the above problems, the embodiment of the application provides a power supply capable of preventing surge and lightning strike and a protection method of the power supply, and whether the surge voltage generated by lightning strike is excessive or not is determined by detecting the current value corresponding to the lightning protection diode, so that the MOS tube in the PFC circuit is damaged or not is determined. Because lightning protection diode can switch on fast when receiving the thunderbolt, consequently also will change fast through lightning protection diode's electric current, according to the operating condition who controls the MOS pipe through lightning protection diode's electric current, can be quick effectual protection MOS pipe to guarantee the normal work of power.
Fig. 4 is a schematic structural diagram of a power supply for preventing surge lightning according to an embodiment of the present application. As shown in fig. 4, the power supply for preventing surge lightning strike includes an AC input source AC, diodes Z1 and Z2, lightning protection diodes D1 and D2, PFC inductor L1, MOS transistor 1 and MOS transistor 2, a control circuit 101, a current detection circuit 102, a driving circuit 103, and a bus capacitor 104.
The PFC inductor L1, the MOS tube 1 and the MOS tube 2 form a PFC circuit, and the current detection circuit 102 and the lightning protection diodes D1 and D2 form a protection circuit. The first terminal of the current detection circuit 102 is connected to AC and is grounded. The second end is connected with the positive end of the lightning protection diode D1 and the negative end of the lightning protection diode D2. The current detection circuit 102 is connected with the control circuit 101, the control circuit 101 is connected with one end of the driving circuit 103, and the other end of the driving circuit 103 is connected with the grids of the MOS tube 1 and the MOS tube 2.
When the power supply is not struck by lightning and normally supplies power to the outside, the lightning protection diodes D1 and D2 are in an off state, so no current passes. At this time, the current detection circuit 102 has no detection result, and therefore the control circuit 101 cannot issue an instruction to the driving circuit according to the detection result. At this time, the operation state of the power supply is similar to the power supply state of the power supply in the embodiment shown in fig. 2. Specifically, when the alternating current provided by the AC is positive, the MOS transistor 1 is turned on, and the MOS transistor 2 is turned off. The current flows into the MOS tube 1 through the PFC inductor L1, and charges the bus capacitor 104 through the drain electrode of the MOS tube 1, and at the moment, the voltages at two ends of the bus capacitor 104 are positive and negative. When the alternating current provided by the AC is negative, the MOS tube 1 is turned off, and the MOS tube 2 is turned on. The current flows into the MOS tube 2 through the PFC inductor L1, and then returns to the AC through the diode Z2 by the MOS tube 2, and the bus capacitor is not charged at the moment. Therefore, the voltage across the bus capacitor is always positive, providing direct current for the next stage DC-DC circuit.
When the power supply receives lightning stroke, current passes through the lightning protection diode D1 or D2, and at the moment, if surge voltage generated by the power supply due to the lightning stroke is positive voltage, the lightning protection diode D1 is in a conducting state. At this time, a part of the surge current charges the bus capacitor through the lightning protection diode D1. The other part of surge current enters the MOS tube 1 through the PFC inductor L1 in the PFC circuit, and then charges the bus capacitor through the MOS tube 1.
In order to protect the MOS transistor 1 and the MOS transistor 2 in the PFC circuit, when a current flows through the lightning protection diode D1, the current detection circuit 102 detects the current flowing through the lightning protection diode D1 and feeds back the detected current value to the control circuit 101. The control circuit 101 compares the current passing through the lightning protection diode D1 with a preset current threshold value, and determines the surge voltage condition. It can be understood that if the current passing through the lightning protection diode D1 is smaller than the preset current threshold, it indicates that the surge voltage generated by lightning strike is not large enough to cause the breakdown of the MOS transistor. Therefore, the control circuit does not need to forcibly turn off the MOS tube, so that the PFC circuit can be ensured to normally carry out power factor correction, and the normal power supply of the power supply is ensured. If the current passing through the lightning protection diode D1 is larger than the preset current threshold value, the fact that surge voltage is overlarge due to lightning stroke is indicated, and the MOS tube is likely to be broken down. At this time, the control circuit 101 needs to send an instruction to the driving circuit 103, so that the driving circuit 103 forcibly turns off the MOS transistor, thereby protecting the MOS transistor from breakdown, and finally protecting the power supply from damage.
It can be understood that during lightning strike, the surge current firstly enters the bus capacitor through the lightning protection diode, and then enters the bus capacitor 104 through the PFC inductor L1 and the MOS tube of the PFC circuit, so that the change of the voltage on the bus capacitor 104 is relatively lagged. The current change of the PFC inductor L1 is more lagged, and the working frequency of the PFC circuit is higher and higher along with the miniaturization and high densification of the power supply, the inductance of the PFC inductor is smaller and smaller, and the lagging effect of the PFC inductor current is not obvious. At this time, when the voltage of the bus capacitor 104 rises to the protection threshold, the MOS transistor in the PFC circuit has a greater risk of damage. Therefore, the protection speed of protecting the MOS transistor according to the voltage variation at both ends of the bus capacitor 104 is too slow to effectively protect the PFC circuit in time. The current change of the lightning protection diode is far earlier than the current change of the PFC inductance L1 and the voltage change of the bus voltage 104, and once the power supply is struck by lightning, the lightning protection diode can pass current. According to the protection of the MOS tube by the current of the lightning protection diode, the protection speed of the MOS tube can be greatly improved, so that the PFC circuit is timely and effectively protected, and the damage of a power supply is prevented.
Based on the above description, an embodiment of the present application provides a current detection circuit. Fig. 5 is a schematic structural diagram of a current detection circuit according to an embodiment of the present application. As shown in fig. 5, the current detection circuit includes a current sampling resistor R, a voltage comparator S1 and a voltage comparator S2, diodes D1 and D2, and a MOS transistor M1.
The first end of the current sampling resistor R is connected between two lightning protection diodes in the embodiment shown in fig. 4, and the second end is grounded, so that the current sampling resistor R is connected in series with the lightning protection diodes. The current sampling resistor R is used to convert the current passing through the lightning protection diode into a voltage signal, and the voltage signal is input into the voltage comparator. It can be understood that the current sampling resistor R may be replaced by a sampling element such as an inductor or a current transformer, which is not specifically limited, and the sampling element may convert a current into a voltage signal.
And the first end of the current sampling resistor R is also connected with the positive input end of the comparator S1 through a resistor R2, and is connected with the negative input end of the comparator S2 through a resistor R4. The positive input end of the comparator S1 is further connected to a positive voltage source +vref and a resistor R2. It will be appreciated that by varying the resistance of R1 and R2, the partial pressure at point A can be varied. The reference voltage of the voltage comparator S1 is the first preset voltage value. The negative input end of the comparator S2 is also connected with a negative voltage source-Vref and a resistor R5. It will be appreciated that by varying the resistance of R4 and R5, the partial pressure at point B can be varied. The reference voltage of the voltage comparator S2 is the second preset voltage value. The power VCC, the resistors R3, R6, R7, etc. are peripheral circuits of the comparator, and are used for supporting the functions of the comparators S1 and S2, which are not described herein.
When the power supply works normally, no current passes through the lightning protection diode. Therefore, the voltage across the circuit sampling resistor R is 0, and the voltage division of the positive voltage source +vref at the point a is positive at this time, and the comparator S1 outputs a high level. The voltage division of the negative voltage source-Vref at point B is negative, and the output of the comparator S2 is also high because the negative input terminal of the comparator S1 is connected to point B. At this time, the diodes D1 and D2 are both turned off, so that the drain of the MOS transistor will output a low level signal to the control circuit 101, and when the control circuit 101 receives the low level signal, it can be determined that the power supply is not at risk of being damaged by lightning strike, so that the power supply normally supplies power to the outside.
And when a lightning strike occurs, the surge voltage through the lightning protection diode may have two directions. At this time, the direction of the current flowing through the circuit sampling resistor R may be from ground to point C or from point C to low. If the current flowing through the circuit sampling resistor R is from the ground to the point C, and then enters the bus capacitor through the lightning protection diode D1, the voltage at two ends of the sampling resistor is negative. When the absolute value of the negative voltage is greater than the voltage division of the positive voltage source +Vref at the point A, the voltage at the positive input terminal of the comparator S1 is negative, and the comparator S1 outputs a low level. While the voltage at the negative input of the comparator S2 is still negative and still outputs a high level. At this point diode D1 is on and D2 is off, which will prevent the two comparators from shorting. So that the drain of the MOS transistor will output a high level signal to the controller 101. When the control circuit 101 obtains the high-level signal, the control circuit 101 considers that the power supply is struck by lightning, then an instruction can be sent to the driving circuit 103, and the driving circuit 103 is controlled to turn off the MOS tube in the PFC circuit, so that the PFC circuit is protected.
When the current flowing through the circuit sampling resistor R is from point C to low and then enters the bus capacitor through the lightning protection diode D2, the voltage at two ends of the sampling resistor is positive voltage. When the absolute value of the positive voltage is greater than the voltage division of the negative voltage source-Vref at the point B, the voltage at the negative input end of the comparator S2 is positive, and the comparator S2 outputs a low level. While the voltage at the positive input of the comparator S1 is still positive and still outputs a high level. Diode D2 is on and D1 is off at this point, which will prevent the two comparators from shorting. So that the drain of the MOS transistor will output a high level signal to the controller 101. When the control circuit 101 obtains the high-level signal, the control circuit 101 considers that the power supply is struck by lightning, then an instruction can be sent to the driving circuit 103, and the driving circuit 103 is controlled to turn off the MOS tube in the PFC circuit, so that the PFC circuit is protected.
In the current detection circuit, the voltage comparator is used for judging whether surge voltage generated by lightning stroke is overlarge or not, so that the structure of the current detection circuit can be simplified, the lightning stroke condition can be more quickly and simply determined, and the PFC circuit is protected. It will be appreciated that the above configuration of the current detection circuit is merely one configuration, and is not particularly limited. As long as the current detection circuit based on the idea of protecting the MOS transistor in the PFC circuit according to the current corresponding to the lightning protection diode belongs to the protection scope of the embodiment of the present application, for example, the ammeter is used to measure the current passing through the lightning protection diode, and the measured current value is fed back to the control circuit 101, and the control circuit 101 compares the current value with the preset threshold value, so that the turn-off of the MOS transistor in the PFC circuit is also a form of the lightning protection power supply provided by the embodiment of the present application.
Fig. 6 is a schematic flow chart of a power supply control method for preventing surge lightning strike according to an embodiment of the present application, which can be used in the power supplies for preventing surge lightning strike shown in fig. 5 and 6, and the method includes:
601. the controller obtains the current passing through the lightning protection diode in the protection circuit.
602. And the controller controls the conduction state of a switching tube included in the power factor correction circuit according to the current passing through the lightning protection diode.
The power supply comprises a power factor correction circuit, a protection circuit and a controller.
The protection circuit comprises a lightning protection diode and a current detection unit. The lightning protection diode is used for conducting under the condition of surge lightning strike, and transmitting current generated by the surge lightning strike to an output circuit of the power supply. The current detection unit is used for detecting the current passing through the lightning protection diode under the condition of surge lightning strike. The power factor correction circuit is used for correcting the power factor of the power supply and comprises a power factor inductor and a switching tube. One end of the power factor inductor is connected with an input circuit of the power supply, and the other end of the power factor inductor is connected with the switching tube.
The controller determines that the current passing through the lightning protection diode exceeds a preset current threshold value, and controls the switching tube to be turned off according to the determination result.
The current detection unit includes a sampling element, a voltage comparator, a reverse diode, and a field effect MOS transistor. The first end of the sampling element is connected with the input end of the voltage comparator, and the second end of the sampling element is grounded. The output end of the voltage comparator is connected with one end of the reverse diode, and the other end of the reverse diode is connected with the grid electrode of the MOS tube.
The sampling element is used for converting current corresponding to the lightning protection diode into voltage. The voltage comparator is used for determining that the voltage at two ends of the sampling element is larger than a preset voltage value and outputting a low-level signal. The reverse diode is used for conducting a low-level signal. The MOS tube is used for outputting a high-level signal to the control module according to the low-level signal. And then the controller controls the switching tube to be turned off according to the high-level signal.
The voltage comparator includes a first voltage comparator and a second voltage comparator. The first end of the sampling element is connected with the positive input end of the first voltage comparator through the first resistor. The first end of the sampling element is connected with the negative input end of the second voltage comparator through a third resistor. The first voltage comparator is used for outputting a low-level signal according to the negative voltage at two ends of the sampling element. The second voltage comparator is used for outputting a low-level signal according to the positive voltage at two ends of the sampling element.
Illustratively, the first voltage comparator corresponds to a positive voltage source and a second resistor, and the second voltage comparator corresponds to a negative voltage source and a fourth resistor. One end of the second resistor is connected with the positive voltage source, and the other end of the second resistor is connected with the positive input end of the first voltage comparator. One end of the fourth resistor is connected with a negative voltage source, and the other end of the fourth resistor is connected with the negative input end of the second voltage comparator. The resistance values of the first resistor and the second resistor are used for adjusting the first preset voltage value. The resistance values of the third resistor and the fourth resistor are used for adjusting the second preset voltage value.
The first voltage comparator is for determining that an absolute value of a negative voltage across the sampling element is greater than a first preset voltage value, and outputting a low level signal. The second voltage comparator is used for determining that the absolute value of the positive voltage at two ends of the sampling element is larger than a second preset voltage value and outputting a low-level signal.
The power supply also includes a rectifier circuit, for example. The rectification circuit is used for converting alternating current provided by an input circuit of the power supply under the condition of no surge lightning strike into direct current and providing the direct current to the power factor correction circuit.
The power supply further comprises a driving circuit, and the driving circuit is connected with the controller. The driving circuit is used for driving the switching tube to be turned on or turned off according to the instruction of the controller.
Illustratively, the sampling element comprises a sampling resistor, a sampling inductance, or a sampling current transformer.
In the above power protection method, the controller controls the current detection unit to detect the current passing through the lightning protection diode, and then controls the on state of the switching tube in the power factor correction circuit according to the current passing through the lightning protection diode. Therefore, when the surge voltage generated after the power supply is struck by lightning is overlarge, the switching tube can be turned off timely, the switching tube is protected more quickly and efficiently, and the phenomenon that the switching tube is broken down due to overlarge instantaneous voltage is avoided. Thereby protecting the safety of the power supply and ensuring the normal work of the power supply and the service life of the power supply.
The technical terms used in the embodiments of the present invention are only used to illustrate specific embodiments and are not intended to limit the present invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. Further, as used in the specification, the terms "comprises" and/or "comprising" mean that there is a stated feature, integer, step, operation, element, and/or component, but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, and/or components.
The corresponding structures, materials, acts, and equivalents of all means or step plus function elements, if any, in the claims below are intended to include any structure, material, or act for performing the function in combination with other specifically claimed elements. The description of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in the form disclosed.
Claims (18)
1. A power supply for protecting against a surge lightning strike, said power supply comprising: a power factor correction circuit, a protection circuit and a controller;
the protection circuit comprises a lightning protection diode and a current detection unit; the lightning protection diode is used for being conducted under the condition of surge lightning strike, and transmitting current generated by the surge lightning strike to an output circuit of the power supply; the current detection unit is used for detecting the current passing through the lightning protection diode under the condition of surge lightning stroke;
the power factor correction circuit is used for correcting the power factor of the power supply and comprises a power factor inductor and a switching tube; one end of the power factor inductor is connected with an input circuit of the power supply, and the other end of the power factor inductor is connected with the switching tube;
The controller is used for controlling the conduction state of the switching tube according to the current passing through the lightning protection diode.
2. The power supply of claim 1, wherein the power supply comprises a power supply,
the controller determines that the current passing through the lightning protection diode exceeds a preset current threshold value, and the controller controls the switching tube to be turned off.
3. The power supply according to claim 1, wherein the current detection unit includes: the device comprises a sampling element, a voltage comparator, a reverse diode and a field effect MOS (metal oxide semiconductor) tube;
the first end of the sampling element is connected with the input end of the voltage comparator, and the second end of the sampling element is grounded; the output end of the voltage comparator is connected with one end of the reverse diode, and the other end of the reverse diode is connected with the grid electrode of the MOS tube;
the sampling element is used for converting current corresponding to the lightning protection diode into voltage;
the voltage comparator is used for determining that the voltage at two ends of the sampling element is larger than a preset voltage value and outputting a low-level signal;
the reverse diode is used for conducting according to the low-level signal;
the MOS tube is used for outputting a high-level signal to the controller according to the low-level signal;
The controller is used for controlling the switching tube to be switched off according to the high-level signal.
4. A power supply according to claim 3, wherein the voltage comparator comprises a first voltage comparator and a second voltage comparator;
the first end of the sampling element is connected with the positive input end of the first voltage comparator through a first resistor; the first end of the sampling element is connected with the negative input end of the second voltage comparator through a third resistor;
the first voltage comparator is used for outputting the low-level signal according to the negative voltage at two ends of the sampling element;
the second voltage comparator is used for outputting the low-level signal according to the positive voltage at two ends of the sampling element.
5. The power supply of claim 4, wherein the first voltage comparator corresponds to a positive voltage source and a second resistor; the second voltage comparator is correspondingly provided with a negative voltage source and a fourth resistor;
one end of the second resistor is connected with the positive voltage source, and the other end of the second resistor is connected with the positive input end of the first voltage comparator;
one end of the fourth resistor is connected with the negative voltage source, and the other end of the fourth resistor is connected with the negative input end of the second voltage comparator;
The resistance values of the first resistor and the second resistor are used for adjusting a first preset voltage value;
and the resistance values of the third resistor and the fourth resistor are used for adjusting a second preset voltage value.
6. The power supply of claim 5, wherein the first voltage comparator is configured to determine that an absolute value of a negative voltage across the sampling element is greater than the first preset voltage value, and output the low level signal;
the second voltage comparator is used for determining that the absolute value of the positive voltage at two ends of the sampling element is larger than the second preset voltage value and outputting the low-level signal.
7. The power supply of any one of claims 1 to 6, further comprising a rectifying circuit;
the rectification circuit is used for converting alternating current provided by the input circuit of the power supply under the condition of no surge lightning strike into direct current and providing the direct current to the power factor correction circuit.
8. The power supply of any one of claims 1 to 6, further comprising a drive circuit; the driving circuit is connected with the controller;
the driving circuit is used for driving the switching tube to be turned on or turned off according to the instruction of the controller.
9. The power supply of any one of claims 3 to 6, wherein the sampling element comprises:
sampling resistor, sampling inductance or sampling current transformer.
10. A power supply control method for protecting against a surge lightning strike, the power supply control method comprising:
the controller obtains the current passing through the lightning protection diode in the protection circuit;
the controller controls the conduction state of a switching tube included in the power factor correction circuit according to the current passing through the lightning protection diode;
wherein the power supply comprises the power factor correction circuit, the protection circuit and the controller;
the protection circuit comprises the lightning protection diode and a current detection unit; the lightning protection diode is used for being conducted under the condition of surge lightning strike, and transmitting current generated by the surge lightning strike to an output circuit of the power supply; the current detection unit is used for detecting the current passing through the lightning protection diode under the condition of surge lightning stroke;
the power factor correction circuit is used for correcting the power factor of the power supply and comprises a power factor inductor and the switching tube; one end of the power factor inductor is connected with an input circuit of the power supply, and the other end of the power factor inductor is connected with the switching tube.
11. The method for controlling a power supply according to claim 10, wherein,
the controller determines that the current passing through the lightning protection diode exceeds a preset current threshold value, and controls the switching tube to be turned off according to a determination result.
12. The power supply control method according to claim 10, wherein the current detection unit includes: the device comprises a sampling element, a voltage comparator, a reverse diode and a field effect MOS (metal oxide semiconductor) tube;
the first end of the sampling element is connected with the input end of the voltage comparator, and the second end of the sampling element is grounded; the output end of the voltage comparator is connected with one end of the reverse diode, and the other end of the reverse diode is connected with the grid electrode of the MOS tube;
the sampling element is used for converting current corresponding to the lightning protection diode into voltage;
the voltage comparator is used for determining that the voltage at two ends of the sampling element is larger than a preset voltage value and outputting a low-level signal;
the reverse diode is used for conducting according to the low-level signal;
the MOS tube is used for outputting a high-level signal to the controller according to the low-level signal;
the controller controls the on state of a switching tube included in the power factor correction circuit according to the current passing through the lightning protection diode, and the controller controls the switching tube to be turned off according to the high-level signal.
13. The power control method according to claim 12, wherein the voltage comparator includes a first voltage comparator and a second voltage comparator;
the first end of the sampling element is connected with the positive input end of the first voltage comparator through a first resistor; the first end of the sampling element is connected with the negative input end of the second voltage comparator through a third resistor;
the first voltage comparator is used for outputting the low-level signal according to the negative voltage at two ends of the sampling element;
the second voltage comparator is used for outputting the low-level signal according to the positive voltage at two ends of the sampling element.
14. The power control method of claim 13, wherein the first voltage comparator corresponds to a positive voltage source and a second resistor; the second voltage comparator is correspondingly provided with a negative voltage source and a fourth resistor;
one end of the second resistor is connected with the positive voltage source, and the other end of the second resistor is connected with the positive input end of the first voltage comparator;
one end of the fourth resistor is connected with the negative voltage source, and the other end of the fourth resistor is connected with the negative input end of the second voltage comparator;
The resistance values of the first resistor and the second resistor are used for adjusting a first preset voltage value;
and the resistance values of the third resistor and the fourth resistor are used for adjusting a second preset voltage value.
15. The power supply control method according to claim 14, characterized in that:
the first voltage comparator is used for determining that the absolute value of the negative voltage at two ends of the sampling element is larger than the first preset voltage value and outputting the low-level signal;
the second voltage comparator is used for determining that the absolute value of the positive voltage at two ends of the sampling element is larger than the second preset voltage value and outputting the low-level signal.
16. The power supply control method according to any one of claims 10 to 15, characterized in that the power supply further comprises a rectifying circuit;
the rectification circuit is used for converting alternating current provided by the input circuit of the power supply under the condition of no surge lightning strike into direct current and providing the direct current to the power factor correction circuit.
17. The power supply control method according to any one of claims 10 to 15, characterized in that the power supply further includes a drive circuit; the driving circuit is connected with the controller;
The driving circuit is used for driving the switching tube to be turned on or turned off according to the instruction of the controller.
18. The power supply control method according to any one of claims 12 to 15, characterized in that the sampling element includes:
sampling resistor, sampling inductance or sampling current transformer.
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| CN117748924A (en) * | 2022-09-13 | 2024-03-22 | 中兴通讯股份有限公司 | Surge protection method and circuit |
| CN115276396A (en) * | 2022-09-26 | 2022-11-01 | 长城电源技术有限公司 | Bridgeless PFC circuit with lightning surge protection |
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| US5726845A (en) * | 1996-02-28 | 1998-03-10 | Astec International Limited | Short circuit protection for power factor correction circuit |
| TW200703839A (en) * | 2005-07-13 | 2007-01-16 | Mitac Int Corp | Inrush current control circuit |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| KR20210045175A (en) * | 2019-10-16 | 2021-04-26 | 삼성전자주식회사 | Electronic apparatus |
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| US5726845A (en) * | 1996-02-28 | 1998-03-10 | Astec International Limited | Short circuit protection for power factor correction circuit |
| TW200703839A (en) * | 2005-07-13 | 2007-01-16 | Mitac Int Corp | Inrush current control circuit |
| CN101997310A (en) * | 2009-08-24 | 2011-03-30 | 深圳桑达国际电子器件有限公司 | Surge protection circuit and flyback power factor correction device |
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