A driver 24V fan short circuit protection circuit

Abstract

The utility model discloses a kind of driver 24V fan short-circuit protection circuit, and the circuit includes: sampling resistance Rm, for sampling voltage value according to fan current;First switch tube Q1, its gate is controlled to photoelectric coupling secondary side output, control fan negative pole interface FAN-COM and +24V ground EP2 conduction, supply fan power supply;NPN and PNP double triode structure, for when fan current is too large or short-circuit, NPN and PNP double triode structure conduction, low level is output to the gate of first switch tube Q1, turn off the passage of fan negative pole interface FAN-COM and +24V ground EP2, realize fan short-circuit protection.The utility model can actively cut off fan loop when driver external fan fails, protect the power supply circuit device of fan from being damaged.

Description

Technical Field

[0001] This utility model relates to a short-circuit protection method for a 24V fan driver. Background Technology

[0002] A drive is a power control device that combines frequency conversion technology and microelectronics to control an AC motor by changing the frequency of the motor's power supply. The heat generated by its power components directly affects the drive's operational stability and safety; therefore, using a fan to dissipate heat from the power components is crucial. However, since most drive fans are exposed outside the casing, their wires often suffer from damaged insulation, leading to short circuits and burnouts. Prolonged operation of such fans can have a destructive impact on the power components within the drive.

[0003] Existing methods for protecting DC fans in drivers have the following drawbacks: 1. Using a fan fuse: In the event of a short circuit, excessive current may blow the fuse, thus achieving a protective effect. However, this method is a passive and rigid defense approach. 2. Shutting off the fan's power supply circuit: However, since the power supply circuit of the DC fan in the driver is often connected to other DC external devices of the driver, such as contactors, shutting off the power supply circuit often pulls the power supply of the DC contactor low, causing an undervoltage alarm during driver operation, which increases the complexity of troubleshooting. 3. Using a microprocessor to assist in handling fan short circuit faults: However, for drivers, the control board and power board are often designed separately. This method will increase the cost of control board layout and software, and is prone to accidental triggering of the short-circuited fan, which may burn out the fan or power board. Summary of the Invention

[0004] The purpose of this invention is to address the deficiencies in the existing technology and provide a protection circuit for short-circuiting a 24V fan driver: when an external fan experiences a short circuit or overcurrent, it can quickly disconnect the connection between the fan's negative terminal and the power supply's negative terminal, cutting off the fan's power supply without affecting the operation of other DC power supply devices such as contactors.

[0005] To achieve the above objectives, the technical solution provided by this utility model is as follows:

[0006] A short-circuit protection circuit for a 24V fan driver, including

[0007] Optocoupler OC1 is isolated by outputting high and low level control signals;

[0008] The sampling resistor Rm is used to sample the current during the operation of the wind turbine, and the output sampling voltage is sent to the dual transistor structure.

[0009] The first switching transistor Q1 has its gate controlled by the high and low level output of optocoupler OC1, which controls the connection between the negative terminal FAN-COM of the fan and the +24V ground EP2, thus supplying power to the fan.

[0010] The NPN transistor Q2 and PNP transistor Q3 form the dual transistor structure. When the fan current is too high or short-circuited, the NPN transistor Q2 and PNP transistor Q3 are turned on, outputting a low level to the gate of the first switching transistor Q1, thereby turning off the path between the fan negative terminal FAN-COM and +24V ground EP2.

[0011] This invention controls the power supply to the fan by controlling the conduction of the first switching transistor through an optocoupler output. Simultaneously, a dual-transistor structure controlled by the voltage drop across the sampling resistor controls the connection between the fan's negative terminal and +24V ground, thus providing short-circuit protection for the fan. The control and power supply are isolated, ensuring the isolation between the power supply to the control system and the power supply to the drive motor. Furthermore, the short-circuit protection for the fan, by cutting off the connection between the fan's negative terminal and +24V ground, does not affect other components connected to +24V ground, such as the DC contactor in the driver.

[0012] Furthermore, the aforementioned sampling resistors are often low-resistance, high-power-rated resistors, and their resistance is not significantly affected by temperature changes. They are commonly used to convert current signals into voltage signals. In this fan short-circuit protection method, the output current of the fan is detected, the output current is converted into an output voltage, and the detected output voltage is output to a dual transistor structure composed of NPN and PNP transistors.

[0013] Furthermore, the aforementioned 24V fan short-circuit protection circuit for the driver also includes a fan turn-on signal interface FAN on the primary side of the optocoupler and a fan positive interface FAN+24V on the secondary side of the optocoupler; the fan turn-on signal interface FAN is connected to the input terminal of the optocoupler OC1, and the fan positive interface FAN+24V is connected to the output terminal of the optocoupler OC1.

[0014] Furthermore, the anode of the primary diode of the aforementioned optocoupler OC1 is connected to the control side power ground EP1 through a pull-down resistor R8 to prevent the optocoupler anode from being mis-energized when there is no control signal, which could cause the fan to be mis-energized. The secondary output emitter of the optocoupler OC1 is connected in series with a first current-limiting resistor R1 and a second current-limiting resistor R6 to control the output current and prevent the optocoupler from burning out.

[0015] Furthermore, the aforementioned first switching transistor Q1 is a transistor, including but not limited to a field-effect transistor.

[0016] Furthermore, the gate of the first switching transistor Q1 is connected to the emitter of the output terminal of the optocoupler OC1 via the first current-limiting resistor R1; the collector of the first switching transistor Q1 is connected to the negative terminal interface FAN-COM of the fan; and the emitter of the first switching transistor Q1 is connected in series with the sampling resistor Rm and then connected to the +24V ground EP2.

[0017] Furthermore, the gate and emitter of the first switching transistor Q1 are connected via a pull-down resistor R7, which pulls the floating gate level down to the emitter level when there is no fan input signal.

[0018] To ensure that when there is no fan control signal, the gate pull-down turns off the first switch, disconnects the connection between the fan negative terminal FAN-COM and +24V ground EP2, and disconnects the fan power supply circuit.

[0019] Another method for short-circuit protection of the wind turbine power supply is to connect a Zener diode to the gate of the first switching transistor to limit the amplitude of the gate control level and ensure that the first switching transistor will not break down.

[0020] Furthermore, the base of the aforementioned NPN transistor Q2 is connected to one end of the current-sensing resistor Rm via the third current-limiting resistor R3, and its emitter is connected to the +24V ground EP2 and the other end of the sampling resistor Rm. The voltage drop across the current-sensing resistor Rm is applied to the base and emitter of the NPN transistor Q2, controlling the turn-on and turn-off of the NPN transistor Q2. The collector of the NPN transistor is connected to the base of the PNP transistor Q3. The positive terminal interface FAN+24V of the fan is connected to the emitter of the PNP transistor Q3 via the optocoupler OC1 and the first current-limiting resistor R1. When the optocoupler OC1 is turned on, the PNP transistor Q3 is turned on or off under the control of the base voltage. The collector of the PNP transistor Q3 is connected to the sampling resistor Rm via the third current-limiting resistor R3, and the collector voltage level is controlled by the voltage drop across the sampling resistor Rm.

[0021] When the fan is short-circuited, the voltage drop across the sampling resistor increases rapidly. When the NPN and PNP dual transistors are turned on, they will enter a blocked conduction state. The continuous conduction pulls the gate of the first switching transistor low, cutting off the connection between the fan's negative terminal and +24V ground EP2, thus depriving the fan of its path. When the fan is turned off, since the dual transistors are in a blocked conduction state, unless the primary side of the optocoupler is pulled low to cut off the path between +24V ground EP2 and the first and second current-limiting resistors, the NPN and PNP dual transistors cannot be turned off, thus improving the reliability of the protection.

[0022] More preferably, when using the circuit of this utility model for short circuit protection of the fan, the fan control signal can be set low, causing the optocoupler output level to be pulled high, cutting off the path between +24V ground EP2 and the first and second current limiting resistors. When the fan short circuit or overcurrent situation is dealt with, the fan control signal can be turned on again to realize the re-conduction of the protection circuit.

[0023] Preferably, the short-circuit protection circuit for the fan of this utility model can be used in the circuit of the external cooling fan of the driver, where the driver refers to a driver that performs rectification and inversion, such as a frequency converter or servo frequency converter.

[0024] This utility model adopts the above solution and has the following characteristics compared with the prior art;

[0025] This utility model discloses a 24V fan short-circuit protection circuit for a driver. It achieves isolation control by isolating the control circuit and power supply circuit through an optocoupler. The sampling resistor samples the fan's current during operation, and the sampling voltage determines the conduction and turn-off of the NPN and PNP transistors, as well as the gate level of the first switching transistor. When a short circuit occurs, the NPN and PNP dual transistors conduct due to the sampling voltage, pulling the gate voltage of the first switching transistor down to a level lower than its emitter, thus turning off the first switching transistor and disconnecting the power supply ground from the fan's negative terminal, achieving a short circuit. When the NPN and PNP dual transistors conduct due to the fan short circuit, they form a blocked conduction state. Unless the primary-side control signal of the optocoupler is actively set low, the fan's power supply circuit will remain cut off, preventing false triggering that could cause a faulty fan to continue operating. Its rapid response and application in the driver field do not require changes to the control board hardware and software, reducing costs.

[0026] This invention disconnects the connection between the negative terminal of the fan and the 24V power supply ground, thus achieving short-circuit protection. Therefore, it will not affect other components on the 24V power supply, such as the DC contactor in the driver. The only issue will be that the fan stops, causing overheating and changing the carrier frequency. There will be no contactor disconnection alarm or undervoltage, which could lead to the sudden stop of the running motor. Attached Figure Description

[0027] Figure 1 This is a simplified circuit diagram of the 24V fan driver short-circuit protection of this utility model;

[0028] Figure 2 This is the circuit diagram for the short-circuit protection of the 24V fan driver of this utility model;

[0029] Figure 3 This is a simplified circuit diagram of the 24V main circuit contactor for short-circuit protection of a 24V fan driver according to this utility model. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for explaining the present utility model and are not intended to limit the present utility model.

[0031] like Figure 1 As shown, this utility model provides a short-circuit protection method for a 24V fan driven by an isolation control circuit that isolates the fan's on / off state, and a short-circuit protection circuit for the fan. This includes a fan on-signal interface FAN on the primary side of an optocoupler, which outputs a high or low level control signal controlled by the driver control system. Figure 2As shown, the short-circuit protection circuit for the fan of this utility model also includes:

[0032] The sampling resistor Rm is used to sample the current during wind turbine operation and outputs a sampling voltage.

[0033] The first switching transistor Q1 has its gate controlled by the high or low level output of the optocoupler OC1, which controls whether it is connected to the negative terminal interface FAN-COM of the fan and the +24V ground EP2 to supply power to the fan. The first switching transistor Q1 includes, but is not limited to, a field-effect transistor (MOSFET). A Zener diode (not shown) can be connected in parallel between its gate and emitter to limit the amplitude of the gate control level and ensure that the first switching transistor Q1 will not break down. The gate of the first switching transistor Q1 has a pull-down resistor R7 to ensure that when there is no fan control signal, the gate pulls down to turn off the first switching transistor Q1, disconnects the connection between the negative terminal interface FAN-COM of the fan and the +24V ground EP2, and disconnects the fan power supply circuit.

[0034] The NPN transistor Q2 and the PNP transistor Q3 form a dual transistor structure. When the fan current is too high or there is a short circuit, the NPN transistor Q2 and the PNP transistor are turned on, and a low level is output to the gate of the first switching transistor Q1, which turns off the path between the fan negative terminal FAN-COM and the +24V ground EP2.

[0035] like Figure 2 As shown, the optocoupler OC1 device with control signal isolation has a pull-down resistor R8 on the anode of its primary diode, which is connected to the control power ground EP1 to prevent the optocoupler anode from being mis-connected when there is no control signal, which could cause the fan to be mis-connected. Its secondary output emitter is also connected in series with a first current-limiting resistor R1 and a second current-limiting resistor R6 to control the output current and prevent the optocoupler OC1 from burning out.

[0036] like Figure 2 As shown, the sampling resistor Rm is usually a low resistance value with high rated power consumption, and its resistance value is not greatly affected by temperature changes. It is often used to convert current signals into voltage signals. This fan short-circuit protection method is used to detect the output current of the fan, convert the output current into output voltage, and output the detected output voltage to the dual triode structure composed of NPN transistor Q2 and PNP transistor Q3.

[0037] like Figure 1 As shown, the filter circuit between the dual transistor structure consisting of NPN transistor Q2 and PNP transistor Q3 and the sampling resistor Rm is used to filter out high-frequency noise generated during driver operation and prevent high-frequency noise interference from causing false activation or false protection.

[0038] like Figure 2 As shown, the positive terminal of the fan, FAN+24V, is normally closed to the positive terminal of the +24V power supply (i.e., FAN+24V). The fan is controlled by switching the +24V ground EP2 on and off to the negative terminal of the fan, FAN-COM.

[0039] like Figure 2 As shown, the base of NPN transistor Q2 is connected to the upper end of sampling resistor Rm via the third current-limiting resistor R3, and its emitter is connected to the +24V power supply ground EP2 and the lower end of sampling resistor Rm. That is, the voltage drop of sampling resistor Rm is applied to the base and emitter of NPN transistor Q2, controlling the turn-on and turn-off of NPN transistor Q2. Its collector is connected to the base of PNP transistor Q3.

[0040] like Figure 2 As shown, the base of PNP transistor Q3 is connected to the collector of NPN transistor Q2, and its emitter is connected to the lower end of the first current-limiting resistor R1. The positive terminal of the 24V power supply FAN+24V is connected to the emitter of PNP transistor Q3 via optocoupler OC1 and the first current-limiting resistor R1. When optocoupler OC1 is turned on, PNP transistor Q3 is turned on or off by the base voltage and controlled by the collector voltage of NPN transistor Q2, that is, controlled by the voltage drop across the sampling resistor Rm. Its collector is connected to the left end of the third current-limiting resistor R3, and the collector voltage level is controlled by the voltage drop across the sampling resistor Rm.

[0041] like Figure 2 As shown, when the fan is short-circuited, the voltage drop across the sampling resistor Rm increases rapidly. When the NPN and PNP dual transistors are turned on, they will enter a blocked conduction state. The continuous conduction pulls the gate of the first switching transistor Q1 low, cutting off the connection between the fan's negative terminal FAN-COM and the +24V power ground EP2, thus depriving the fan of its path. When the fan is turned off, since the dual transistors are in a blocked conduction state, unless the primary side of the optocoupler OC1 is pulled low to cut off the path between 24V and the first current-limiting resistor R1 and the second current-limiting resistor R6, the NPN and PNP dual transistors cannot be turned off, thus improving the reliability of the protection.

[0042] When the fan protection circuit enters the short-circuit protection state, the fan control signal at the fan turn-on signal interface FAN can be set low, causing the output level of optocoupler OC1 to go high, cutting off the path between the positive terminal of 24V power supply FAN+24V and the first current limiting resistor R1 and the second current limiting resistor R6. In the event of a short circuit or overcurrent in the fan, the fan control signal can be turned on again to restore the protection circuit.

[0043] The above fan protection circuit is used for the external cooling fan of the driver. The driver refers to the driver that performs rectification and inversion, such as frequency converters and servo frequency converters.

[0044] like Figure 3 As shown, a 24V DC contactor KM1 is often connected in the 24V power supply path of the driver to short-circuit the driver charging resistor R9. For example... Figure 1As shown, the 24V fan short-circuit method used in this utility model only disconnects the connection between the fan negative terminal FAN-COM and the +24V power ground EP2, cutting off the fan's power supply circuit. It will not affect other electrical appliances connected to the 24V power positive terminal FAN+24V. This is often the case in drivers. Figure 3 The DC contactor KM1 in this invention only causes the drive control system to alarm overheat and then operate at reduced frequency. After the fault is dealt with, the fan and drive can be restarted. It will not cause the contactor to alarm and operate under voltage due to the disconnection of the 24V power supply positive terminal FAN+24V protection, which will further lead to direct shutdown. It is beneficial to fault maintenance and handling.

[0045] Specific examples of wind turbine isolation control startup and short-circuit protection in this utility model are as follows:

[0046] The gate of the first switching transistor Q1 is isolated and controlled by optocoupler OC1. The first switching transistor Q1 controls the connection between the fan negative terminal FAN-COM and the +24V power ground EP2, achieving isolated control of the motor switch. The current during fan operation is sampled by sampling resistor Rm, and the sampled voltage is output to the base and emitter of NPN transistor Q2. When the fan is short-circuited, the sampled voltage exceeds the turn-on threshold of NPN transistor Q2. The turn-on voltage is at least the turn-on voltage Vge(th) of NPN transistor Q2. The collector of NPN transistor Q2 is pulled low to the low level of +24V power ground EP2. The collector of NPN transistor Q2 is connected to the base of PNP transistor Q3. At this time, the base of PNP transistor Q3 is pulled low. Because its emitter is at a high level during normal wind turbine operation, PNP transistor Q3 conducts. After conduction, the emitter Q3 is connected to the collector. At this time, the collector voltage of PNP transistor Q3 is approximately equal to the voltage drop across the sampling resistor. Since the emitter of PNP transistor Q3 is connected to the gate of the first switching transistor Q1, the gate potential of the first switching transistor Q1 is lower than the emitter potential, causing the first switching transistor Q1 to turn off. This disconnects the connection between the wind turbine negative terminal FAN-COM and the +24V power ground EP2, achieving short-circuit protection. At this time, the NPN and PNP dual transistor structure forms a blocking conduction, setting the wind turbine control signal low (i.e., setting the primary input of optocoupler OC1 low), setting the emitter Q3 of PNP transistors to a low level, and turning off both PNP and NPN transistors. After the wind turbine fault is resolved, the wind turbine control signal is returned to a high level, thus restoring power to the wind turbine. This wind turbine protection method prevents the restart of the faulty wind turbine caused by false triggering signals.

[0047] In this utility model, unless otherwise explicitly specified and limited, the terms "connection" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0048] In the description of this utility model, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this utility model is in use. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model. In addition, the terms "first," "second," and "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0049] The above description is merely a specific embodiment of this utility model. It should be noted that the protection scope of this utility model is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this utility model should be included within the protection scope of this utility model. Therefore, the protection scope of this utility model should be determined by the scope of the claims.

Claims

1. A short-circuit protection circuit for a 24V fan driver, characterized in that, include Optocoupler OC1 is isolated by outputting high and low level control signals; The sampling resistor Rm is used to sample the current during the operation of the wind turbine, and the output sampling voltage is sent to the dual transistor structure. The first switching transistor Q1 has its gate controlled by the high and low level output of optocoupler OC1, which controls the connection between the negative terminal FAN-COM of the fan and the +24V ground EP2, thus supplying power to the fan. The NPN transistor Q2 and PNP transistor Q3 form the dual transistor structure. When the fan current is too high or short-circuited, the NPN transistor Q2 and PNP transistor Q3 are turned on, outputting a low level to the gate of the first switching transistor Q1, thereby turning off the path between the fan negative terminal FAN-COM and +24V ground EP2.

2. The short-circuit protection circuit for the 24V fan driver according to claim 1, characterized in that, The driver's 24V fan short-circuit protection circuit also includes a fan turn-on signal interface FAN on the primary side of the optocoupler and a fan positive interface FAN+24V on the secondary side of the optocoupler; the fan turn-on signal interface FAN is connected to the input terminal of the optocoupler OC1, and the fan positive interface FAN+24V is connected to the output terminal of the optocoupler OC1.

3. The short-circuit protection circuit for the 24V fan driver according to claim 2, characterized in that, The anode of the primary diode of the optocoupler OC1 is connected to the control side power ground EP1 through a pull-down resistor R8; the secondary output emitter of the optocoupler OC1 is connected in series with a first current-limiting resistor R1 and a second current-limiting resistor R6.

4. The short-circuit protection circuit for the 24V fan driver according to claim 3, characterized in that, The first switch Q1 is a MOSFET.

5. The 24V fan short-circuit protection circuit for the driver according to claim 4, characterized in that, The gate of the first switch Q1 is connected to the emitter of the output terminal of the optocoupler OC1 via the first current-limiting resistor R1; the collector of the first switch Q1 is connected to the negative terminal interface FAN-COM of the fan; and the emitter of the first switch Q1 is connected in series with the sampling resistor Rm and then connected to the +24V ground EP2.

6. The 24V fan short-circuit protection circuit for the driver according to claim 5, characterized in that, The gate and emitter of the first switch Q1 are connected via a pull-down resistor R7, which pulls the floating gate level down to the emitter when there is no fan input signal.

7. The 24V fan short-circuit protection circuit for the driver according to claim 6, characterized in that, The base of the NPN transistor Q2 is connected to one end of the current-sensing resistor Rm via the third current-limiting resistor R3. Its emitter is connected to the +24V ground EP2 and the other end of the sampling resistor Rm. The voltage drop across the current-sensing resistor Rm is applied to the base and emitter of the NPN transistor Q2, controlling the turn-on and turn-off of the NPN transistor Q2. The collector of the NPN transistor is connected to the base of the PNP transistor Q3. The positive terminal interface FAN+24V of the fan is connected to the emitter of the PNP transistor Q3 via the optocoupler OC1 and the first current-limiting resistor R1. When the optocoupler OC1 is turned on, the PNP transistor Q3 is turned on or off under the control of the base voltage. The collector of the PNP transistor Q3 is connected to the sampling resistor Rm via the third current-limiting resistor R3, and the collector voltage level is controlled by the voltage drop across the sampling resistor Rm.

8. A driver employing the 24V fan short-circuit protection circuit of any one of claims 1 to 7.

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