CN109931287B - Fault detection circuit of alternating current fan and fault detection method thereof - Google Patents
Fault detection circuit of alternating current fan and fault detection method thereof Download PDFInfo
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- CN109931287B CN109931287B CN201910287590.3A CN201910287590A CN109931287B CN 109931287 B CN109931287 B CN 109931287B CN 201910287590 A CN201910287590 A CN 201910287590A CN 109931287 B CN109931287 B CN 109931287B
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Abstract
The invention discloses a fault detection circuit of an alternating current fan, which comprises an alternating current fan and a fan control circuit for controlling the alternating current fan, and is characterized in that a thermal protection switch K2 is arranged in the alternating current fan, the fault detection circuit also comprises a fan driving circuit for driving the alternating current fan and a fan fault detection circuit for detecting the fault of the alternating current fan; the driving signal output end of the fan control circuit is connected with the driving signal input end of the fan driving circuit, the driving signal output end of the fan driving circuit is connected with the driving signal input end of the alternating current fan, the signal detection end of the fan fault detection circuit is connected with the fan driving circuit, and the detection signal output end of the fan fault detection circuit is connected with the detection signal input end of the fan control circuit. The technical scheme of the invention simplifies the fault detection circuit and the fault detection method of the traditional alternating current fan, greatly reduces the power loss, saves the PCB layout and wiring space and saves the cost.
Description
Technical Field
The invention relates to the field of alternating current fans, in particular to a fault detection circuit of an alternating current fan and a fault detection method thereof.
Background
In the interior of high-power electrical equipment in various industries of the society, a plurality of heating devices exist, in order to ensure that the devices are not damaged by overheating, certain cooling measures must be taken for the equipment, and forced air cooling is one of the cooling measures. In the forced air cooling method, a fan is one of the most important components, and good operation conditions of the fan are the premise for normal operation of equipment. Because the fan belongs to a vulnerable part, the equipment generally needs to detect the fan fault, so that a user is reminded of replacing the fan in time when the fan is in fault, and normal operation is continued after equipment maintenance is carried out in time.
In the existing fault detection technology, a rectifier bridge and a diode are connected in series into a power supply loop, so that the diode generates direct current voltage drop, the voltage drop enables an optical coupler to be conducted, and signals output by an optical coupler receiving tube are sent to a processor. The existing fault detection technology has the following defects:
1. because the current of the alternating current fan is usually larger, a power diode needs to be selected for the rectifier bridge and the diode, and meanwhile, because the optical coupler needs basic insulation isolation, in order to meet the requirements of creepage distance and electrical clearance safety regulation, the optical coupler with large encapsulation needs to be adopted, so that the cost of a detection circuit is higher;
2. when the diode normally works, conduction voltage drop is generated on the diode, so that great conduction loss is generated;
3. when the diode is selected, a larger package must be selected or certain heat dissipation measures are taken to occupy a larger PCB layout wiring space.
Disclosure of Invention
The invention mainly aims to provide a fault detection circuit and a fault detection method of an alternating current fan, aiming at simplifying the fault detection circuit and the fault detection method of the traditional alternating current fan, greatly reducing power consumption, saving PCB layout and wiring space and saving cost.
In order to achieve the above object, the fault detection circuit of an ac fan according to the present invention includes an ac fan, a fan control circuit for controlling the ac fan, a thermal protection switch K2 built in the ac fan, a fan driving circuit for driving the ac fan, and a fan fault detection circuit for detecting a fault of the ac fan; the driving signal output end of the fan control circuit is connected with the driving signal input end of the fan driving circuit, the driving signal output end of the fan driving circuit is connected with the driving signal input end of the alternating current fan, the signal detection end of the fan fault detection circuit is connected with the fan driving circuit, and the detection signal output end of the fan fault detection circuit is connected with the detection signal input end of the fan control circuit;
the fan fault detection circuit comprises a current transformer T1, diodes D1, D2, D3 and D4, and a triode Q1, wherein the anode of the diode D1 is connected with the cathode of the diode D2, the anode of the diode D3 is connected with the cathode of the diode D4, the cathode of the diode D1 is connected with the cathode of the diode D3, and the anode of the diode D2 is connected with the anode of the diode D4; the primary side of the current transformer T1 is connected in series with the fan driving circuit, one end of the secondary side of the current transformer T1 is connected with the anode of the diode D1, and the other end of the secondary side of the current transformer T1 is connected with the anode of the diode D3; the base electrode of the triode Q1 is connected with the cathodes of the diode D1 and the diode D3, the emitter electrode of the triode Q1 is connected with the anodes of the diode D2 and the diode D4, and the output end of the triode Q1 is set as the detection signal output end of the fan fault detection circuit.
Preferably, the fan driving circuit comprises an alternating current power supply S1, a switch K1 and a starting capacitor C1 which are connected in series, and the primary side of the current transformer T1 is connected in series between the switch K1 and the starting capacitor C1.
Preferably, the ac fan further includes a start winding L1 and an operation winding L2, one end of the thermal protection switch K2 is connected to the ac power source S1, the other end of the thermal protection switch K2 is connected to the first ends of the start winding L1 and the operation winding L2, the second end of the start winding L1 is connected to the first end of the start capacitor C1, and the second end of the operation winding L2 is connected to the second end of the start capacitor C1.
Preferably, the diodes D1, D2, D3, D4 are provided as signal diodes.
In order to achieve the above object, the present invention provides another fault detection circuit for an ac fan, including an ac fan, a fan control circuit for controlling the ac fan, a thermal protection switch K2 being built in the ac fan, a fan driving circuit for driving the ac fan, and a fan fault detection circuit for detecting a fault of the ac fan; the driving signal output end of the fan control circuit is connected with the driving signal input end of the fan driving circuit, the driving signal output end of the fan driving circuit is connected with the driving signal input end of the alternating current fan, the signal detection end of the fan fault detection circuit is connected with the fan driving circuit, and the detection signal output end of the fan fault detection circuit is connected with the detection signal input end of the fan control circuit;
the fan fault detection circuit comprises a current transformer T1 and a bidirectional input optocoupler U1, wherein an output end of the bidirectional input optocoupler U1 is set as a detection signal output end of the fan fault detection circuit, a first light emitting diode D11 and a second light emitting diode D12 are arranged in the bidirectional input optocoupler U1, an anode of the first light emitting diode D11 is connected with a cathode of the second light emitting diode D12, a cathode of the first light emitting diode D11 is connected with an anode of the second light emitting diode D12, a primary side of the current transformer T1 is connected with the fan driving circuit in series, and two ends of a secondary side of the current transformer T1 are respectively connected with anodes of the first light emitting diode D11 and the second light emitting diode D12.
In order to achieve the above object, the present invention further provides a method for detecting a fault of an ac fan, in which a fan control circuit for controlling the ac fan is connected to the ac fan, the ac fan having a built-in thermal protection switch K2, the method comprising:
step S1: judging whether a fan driving circuit of the alternating current fan is normally driven;
step S2: if the fan driving circuit is normally driven, the level of a detection signal sent by the fan fault detection circuit is judged; if the detection signal is high level, the alternating current fan is in failure, and if the detection signal is low level, the alternating current fan is normal;
step S3: if the fan driving circuit is not driven, the level of a detection signal sent by the fan fault detection circuit is judged; if the detection signal is high level, the alternating current fan is normal, and if the detection signal is low level, the alternating current fan is in failure.
Preferably, the fan fault detection circuit comprises a current transformer T1, diodes D1, D2, D3, D4, a transistor Q1, wherein an anode of the diode D1 is connected to a cathode of the diode D2, an anode of the diode D3 is connected to a cathode of the diode D4, a cathode of the diode D1 is connected to a cathode of the diode D3, and an anode of the diode D2 is connected to an anode of the diode D4; the primary side of the current transformer T1 is connected in series with the fan driving circuit, one end of the secondary side of the current transformer T1 is connected with the anode of the diode D1, and the other end of the secondary side of the current transformer T1 is connected with the anode of the diode D3; the base electrode of the triode Q1 is connected with the cathodes of the diode D1 and the diode D3, the emitter electrode of the triode Q1 is connected with the anodes of the diode D2 and the diode D4, and the output end of the triode Q1 is set as the detection signal output end of the fan fault detection circuit.
Preferably, the fan driving circuit comprises an alternating current power supply S1, a switch K1 and a starting capacitor C1 which are connected in series, and the primary side of the current transformer T1 is connected in series between the switch K1 and the starting capacitor C1.
Preferably, the ac fan further includes a start winding L1 and an operation winding L2, one end of the thermal protection switch K2 is connected to the ac power source S1, the other end of the thermal protection switch K2 is connected to the first ends of the start winding L1 and the operation winding L2, the second end of the start winding L1 is connected to the first end of the start capacitor C1, and the second end of the operation winding L2 is connected to the second end of the start capacitor C1.
Preferably, the fan fault detection circuit includes a current transformer T1 and a bidirectional input optocoupler U1, an output end of the bidirectional input optocoupler U1 is set as a detection signal output end of the fan fault detection circuit, a first light emitting diode D11 and a second light emitting diode D12 are built in the bidirectional input optocoupler U1, an anode of the first light emitting diode D11 is connected with a cathode of the second light emitting diode D12, a cathode of the first light emitting diode D11 is connected with an anode of the second light emitting diode D12, a primary side of the current transformer T1 is connected in series with the fan drive circuit, and two secondary sides of the current transformer T1 are connected with anodes of the first light emitting diode D11 and the second light emitting diode D12, respectively.
Compared with the prior art, the invention has the beneficial effects that:
1. because of the adoption of the current transformer, the current of the secondary side detection circuit of the transformer is very small, the secondary side detection circuit does not need a power device any more, and meanwhile, the transformer has an isolation function and does not need optical coupling isolation, thereby greatly saving the circuit cost.
2. The voltage drop of the primary side of the current transformer is very small, the current of the secondary side is very small, and the power loss of the whole fault detection circuit is very low.
3. And a large packaging device is not needed, heat dissipation measures are omitted, and the PCB layout and wiring space is greatly saved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.
FIG. 1 is a schematic block diagram of AC fan fault detection according to the present invention;
FIG. 2 is a schematic diagram of an AC fan fault detection circuit according to an embodiment of the present invention;
FIG. 3 is a positive current flow diagram of the AC fan when KI is closed according to the present invention;
FIG. 4 is a negative current diagram of the AC fan when KI is closed according to the present invention;
FIG. 5 is a diagram of the circuit configuration for AC fan failure with KI closed according to the present invention;
FIG. 6 is a schematic diagram of an AC fan fault detection circuit according to a second embodiment of the present invention;
FIG. 7 is a flow chart of the AC fan fault detection method of the present invention;
the implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The first embodiment is as follows:
referring to fig. 1, the fault detection circuit for an ac fan according to the present invention includes an ac fan 1, a fan control circuit 2 for controlling the ac fan 1, a thermal protection switch K2 being disposed in the ac fan 1, a fan driving circuit 3 for driving the ac fan 1, and a fan fault detection circuit 4 for detecting a fault of the ac fan 1; the driving signal output end of the fan control circuit 2 is connected with the driving signal input end of the fan driving circuit 3, the driving signal output end of the fan driving circuit 3 is connected with the driving signal input end of the alternating current fan 1, the signal detection end of the fan fault detection circuit 4 is connected with the fan driving circuit 3, and the detection signal output end of the fan fault detection circuit 4 is connected with the detection signal input end of the fan control circuit 2.
It should be noted that, when the ac fan 1 is locked, or otherwise fails, which may cause the internal coil to overheat and reach a certain temperature, the thermal protection switch K2 inside the ac fan 1 is turned off, so as to cut off the external power supply current, thereby realizing self protection of the ac fan 1.
Referring to fig. 2, the fan failure detection circuit 4 includes a current transformer T1, diodes D1, D2, D3, D4, and a transistor Q1, wherein an anode of the diode D1 is connected to a cathode of the diode D2, an anode of the diode D3 is connected to a cathode of the diode D4, a cathode of the diode D1 is connected to a cathode of the diode D3, and an anode of the diode D2 is connected to an anode of the diode D4; the primary side of the current transformer T1 is connected in series with the fan driving circuit 3, one end of the secondary side of the current transformer T1 is connected with the anode of the diode D1, and the other end of the secondary side of the current transformer T1 is connected with the anode of the diode D3; the base of the triode Q1 is connected with the cathodes of the diode D1 and the diode D3, the emitter of the triode Q1 is connected with the anodes of the diode D2 and the diode D4, the output end of the triode Q1 is set as the detection signal output end of the fan fault detection circuit 4, and the diodes D1, D2, D3 and D4 are set as signal diodes.
The fan driving circuit 3 comprises an alternating current power supply S1, a switch K1 and a starting capacitor C1 which are connected in series, and the primary side of the current transformer T1 is connected in series between the switch K1 and the starting capacitor C1.
Alternating current fan 1 still includes a start winding L1 and an operation winding L2, thermal protection switch K2 one end with alternating current power supply S1 is connected, thermal protection switch K2 'S the other end respectively with start winding L1 and operation winding L2' S first end are connected, start winding L1 'S second end with start-up electric capacity C1 first end is connected, operation winding L2' S second end with start-up electric capacity C1 second end is connected.
It should be noted that the ac power supply S1 supplies power for the operation of the ac fan 1; the switch K1 is a controllable switch such as a relay or a thyristor, and the switch K1 is switched on and off to control the operation and stop of the alternating current fan 1; c1 is a starting capacitor, and provides a rotating magnetic field together with a starting winding L1 and a running winding L2 of the alternating current fan 1; the primary side of the current transformer T1 is connected in series in the fan driving circuit 3 for collecting the current of the AC fan 1, and the current is changed into a smaller current with a certain transformation ratio and is transmitted to the secondary side of the current transformer T1; the diodes D1, D2, D3, and D4 form a rectifying circuit to rectify the ac current at the secondary side of the current transformer T1 into dc, and the transistor Q1 amplifies the signal and outputs a level signal to the fan control circuit 2.
Specifically, the method comprises the following steps:
1. referring to fig. 2, when the fan control circuit 2 controls the switch K1 to be turned off, no current flows through the primary side of the current transformer T1, no current flows through the secondary side of the current transformer T1, no current flows through the base electrodes of the diodes D1, D2, D3, D4 and the transistor Q1, the transistor Q1 is turned off, and the normal output level signal of the transistor Q1 is at a high level, so that it can be determined that the ac fan 1 is normal.
2. When the fan control circuit 2 controls the switch K1 to be switched off, under normal conditions, the triode Q1 outputs a high level signal, and if the triode Q1 outputs a low level signal, it indicates that the switch K1 is switched on by mistake, the current transformer T1 has current flowing through, or the fan fault detection circuit 4 has a fault, and it can be determined that the ac fan 1 has a fault.
3. When the fan control circuit 2 controls the switch K1 to be closed and the ac fan 1 normally operates, the thermal protection switch K2 built in the ac fan 1 is in a closed state, and an ac current flows through the primary side of T1:
a. referring to fig. 3, when the ac current is greater than zero, the primary side current of the current transformer T1 returns to the ac power supply S1 from the ac power supply S1 through the switch K1, the primary side of the current transformer T1, the capacitor C1 and the ac fan 1; the current of the secondary side of the current transformer T1 returns to the secondary side of the current transformer T1 from the secondary side of the current transformer T1 through a diode D1, a triode Q1 and a diode D4, at the moment, a triode Q1 is conducted, and an output level signal is a low level;
b. referring to fig. 4, when the ac current is less than zero, the primary side current of the current transformer T1 returns to the ac power supply S1 from the ac power supply S1 through the capacitor C1, the ac fan, the primary side of the current transformer T1, and the switch K1; the current on the secondary side of the current transformer T1 returns to the secondary side of the current transformer T1 from the current transformer T1 through the diode D3, the triode Q1 and the diode D2, at the moment, the triode Q1 is conducted, and the output level signal is at a low level.
4. Referring to fig. 5, when the fan control circuit 2 controls the switch K1 to be closed, if the ac fan 1 fails, the thermal protection switch K2 of the fan is in an open state, the fan driving circuit 3 is turned off, no current flows through the ac fan 1, no current flows through the current transformer T1, no current flows through the bases of the diodes D1, D2, D3, D4 and the transistor Q1, the transistor Q1 is turned off, and the output signal is at a high level.
The current transformer is adopted in the embodiment, so that the current of the secondary side detection circuit of the transformer is very small, the secondary side detection circuit does not need a power device any more, and meanwhile, the transformer has an isolation function and does not need optical coupling isolation, so that the circuit cost is greatly saved. The voltage drop of the primary side of the current transformer is very small, the current of the secondary side is very small, and the power loss of the whole fault detection circuit is very low. Does not need large packaging devices, saves heat dissipation measures and greatly saves PCB layout and wiring space
Example two:
referring to fig. 6, the present invention further provides another fault detection circuit for an ac fan, including an ac fan 1, a fan control circuit 2 for controlling the ac fan 1, a thermal protection switch K2 being disposed in the ac fan 1, a fan driving circuit 3 for driving the ac fan 1, and a fan fault detection circuit 4 for detecting a fault of the ac fan 1; a driving signal output end of the fan control circuit 2 is connected with a driving signal input end of the fan driving circuit 3, a driving signal output end of the fan driving circuit 3 is connected with a driving signal input end of the alternating current fan 1, a signal detection end of the fan fault detection circuit 4 is connected with the fan driving circuit 3, and a detection signal output end of the fan fault detection circuit 4 is connected with a detection signal input end of the fan control circuit 2;
the fan fault detection circuit 4 comprises a current transformer T1 and a bidirectional input optocoupler U1, an output end of the bidirectional input optocoupler U1 is set as a detection signal output end of the fan fault detection circuit 4, a first light emitting diode D11 and a second light emitting diode D12 are arranged in the bidirectional input optocoupler U1, an anode of the first light emitting diode D11 is connected with a cathode of the second light emitting diode D12, a cathode of the first light emitting diode D11 is connected with an anode of the second light emitting diode D12, a primary side of the current transformer T1 is connected in series with the fan drive circuit 3, and two ends of a secondary side of the current transformer T1 are respectively connected with anodes of the first light emitting diode D11 and the second light emitting diode D12.
It should be noted that, in the fan fault detection circuit 4 of the present embodiment, the diodes D1, D2, D3, D4 and the transistor Q1 in the first embodiment are replaced by a bidirectional input optocoupler U1, and the fault detection principle is the same as that in the first embodiment, and is not described again here. It should be noted that, in the following description,
when the alternating current is larger than zero, the current on the primary side of the current transformer T1 returns to the alternating current power supply S1 from the alternating current power supply S1 through the switch K1, the primary side of the current transformer T1, the capacitor C1 and the alternating current fan 1; the current of the secondary side of the current transformer T1 returns to the secondary side of the current transformer T1 from the secondary side of the current transformer T1 through the first light-emitting diode D11, the first light-emitting diode D11 is conducted, and the bidirectional input optocoupler U1 outputs low level;
when the alternating current is less than zero, the current on the primary side of the current transformer T1 returns to the alternating current power supply S1 from the alternating current power supply S1 through the capacitor C1, the alternating current fan, the primary side of the current transformer T1 and the switch K1; the current of the secondary side of the current transformer T1 returns to the secondary side of the current transformer T1 from the secondary side of the current transformer T1 through a second light emitting diode D12, the second light emitting diode D12 is conducted, and a bidirectional input optocoupler U1 outputs low level;
when the alternating current is zero, the first light-emitting diode D11 and the second light-emitting diode are not conducted, and the bidirectional input optocoupler U1 outputs high level;
in summary, whether the alternating current fan 1 fails or not can be judged according to the level of the level signal output by the bidirectional input optocoupler U1 in combination with whether the fan driving circuit 3 is driven or not.
Referring to fig. 7, an ac fan 1 is connected to a fan control circuit 2 for controlling the ac fan 1, and the ac fan is characterized in that a thermal protection switch K2 is built in the ac fan 1, and when an internal coil is overheated and reaches a certain temperature due to a stall of the ac fan 1 or other faults, the thermal protection switch K2 inside the ac fan 1 is turned off, so as to cut off an external power supply current, and achieve self protection of the ac fan 1.
The method for detecting the fault of the alternating current fan 1 comprises the following steps:
step S1: judging whether a fan driving circuit 3 of the alternating current fan 1 is normally driven;
step S2: if the fan driving circuit 3 is normally driven, the level of a detection signal sent by the fan fault detection circuit 4 is judged; if the detection signal is high level, the alternating current fan 1 is in failure, and if the detection signal is low level, the alternating current fan 1 is normal;
step S3: if the fan driving circuit 3 is not driven, the level of a detection signal sent by the fan fault detection circuit 4 is judged; if the detection signal is at a high level, the ac fan 1 is normal, and if the detection signal is at a low level, the ac fan 1 fails.
Further, the fan fault detection circuit 4 includes a current transformer T1, diodes D1, D2, D3, D4, and a transistor Q1, wherein an anode of the diode D1 is connected to a cathode of the diode D2, an anode of the diode D3 is connected to a cathode of the diode D4, a cathode of the diode D1 is connected to a cathode of the diode D3, and an anode of the diode D2 is connected to an anode of the diode D4; the primary side of the current transformer T1 is connected in series with the fan driving circuit 3, one end of the secondary side of the current transformer T1 is connected with the anode of the diode D1, and the other end of the secondary side of the current transformer T1 is connected with the anode of the diode D3; the base of the triode Q1 is connected with the cathodes of the diode D1 and the diode D3, the emitter of the triode Q1 is connected with the anodes of the diode D2 and the diode D4, and the output end of the triode Q1 is set as the detection signal output end of the fan failure detection circuit 4.
Further, the fan driving circuit 3 includes an ac power source S1, a switch K1, and a starting capacitor C1 connected in series, and the primary side of the current transformer T1 is connected in series between the switch K1 and the starting capacitor C1.
Further, alternating current fan 1 still includes a start winding L1 and an operation winding L2, thermal protection switch K2 one end with alternating current power supply S1 is connected, thermal protection switch K2 'S the other end respectively with start winding L1 and the first end of operation winding L2 are connected, start winding L1' S second end with start capacitor C1 first end is connected, the second end of operation winding L2 with start capacitor C1 second end is connected.
It should be noted that the ac power supply S1 supplies power for the operation of the ac fan 1; the switch K1 is a controllable switch such as a relay or a thyristor, and the switch K1 is switched on and off to control the operation and stop of the alternating current fan 1; c1 is a starting capacitor, and provides a rotating magnetic field together with a starting winding L1 and a running winding L2 of the alternating current fan 1; the primary side of the current transformer T1 is connected in series in the fan driving circuit 3 for collecting the current of the AC fan 1, and the current is changed into a smaller current with a certain transformation ratio and is transmitted to the secondary side of the current transformer T1; the diodes D1, D2, D3, and D4 form a rectifying circuit to rectify the ac current at the secondary side of the current transformer T1 into dc, and the transistor Q1 amplifies the signal and outputs a level signal to the fan control circuit 2.
Specifically, the method comprises the following steps:
1. referring to fig. 2, when the fan control circuit 2 controls the switch K1 to be turned off, no current flows through the primary side of the current transformer T1, no current flows through the secondary side of the current transformer T1, no current flows through the bases of the diodes D1, D2, D3, D4 and the transistor Q1, the transistor Q1 is turned off, and the normal output level signal of the transistor Q1 is at a high level, so that it can be determined that the ac fan 1 is normal.
2. When the fan control circuit 2 controls the switch K1 to be switched off, under normal conditions, the triode Q1 outputs a high level signal, and if the triode Q1 outputs a low level signal, it indicates that the switch K1 is switched on by mistake, the current transformer T1 has current flowing through, or the fan fault detection circuit 4 has a fault, and it can be determined that the ac fan 1 has a fault.
3. When the fan control circuit 2 controls the switch K1 to be closed and the ac fan 1 normally operates, the thermal protection switch K2 built in the ac fan 1 is in a closed state, and an ac current flows through the primary side of T1:
a. referring to fig. 3, when the ac current is greater than zero, the primary side current of the current transformer T1 returns to the ac power supply S1 from the ac power supply S1 through the switch K1, the primary side of the current transformer T1, the capacitor C1 and the ac fan 1; the current of the secondary side of the current transformer T1 returns to the secondary side of the current transformer T1 from the secondary side of the current transformer T1 through a diode D1, a triode Q1 and a diode D4, at the moment, a triode Q1 is conducted, and an output level signal is a low level;
b. referring to fig. 4, when the ac current is less than zero, the primary side current of the current transformer T1 returns to the ac power supply S1 from the ac power supply S1 through the capacitor C1, the ac fan, the primary side of the current transformer T1, and the switch K1; the current on the secondary side of the current transformer T1 returns to the secondary side of the current transformer T1 from the current transformer T1 through the diode D3, the triode Q1 and the diode D2, at the moment, the triode Q1 is conducted, and the output level signal is at a low level.
4. Referring to fig. 5, when the fan control circuit 2 controls the switch K1 to be closed, if the ac fan 1 fails, the thermal protection switch K2 of the fan is in an open state, the fan driving circuit 3 is turned off, no current flows through the ac fan 1, no current flows through the current transformer T1, no current flows through the bases of the diodes D1, D2, D3, D4 and the transistor Q1, the transistor Q1 is turned off, and the output signal is at a high level.
Further, referring to fig. 6, the fan fault detection circuit 4 may replace diodes D1, D2, D3, D4 and a triode Q1 with a bidirectional input optocoupler U1, an output end of the bidirectional input optocoupler U1 is set as a detection signal output end of the fan fault detection circuit 4, a first light emitting diode D11 and a second light emitting diode D12 are built in the bidirectional input optocoupler U1, an anode of the first light emitting diode D11 is connected with a cathode of the second light emitting diode D12, a cathode of the first light emitting diode D11 is connected with an anode of the second light emitting diode D12, a primary side of the current transformer T1 is connected in series with the fan driving circuit 3, and two secondary sides of the current transformer T1 are connected with anodes of the first light emitting diode D11 and the second light emitting diode D12, respectively. The method of detecting the fault of the fan fault detection circuit 4 after replacement is the same as that before replacement, and is not described herein again. It should be noted that, when the ac current is greater than zero, the primary side current of the current transformer T1 returns to the ac power supply S1 from the ac power supply S1 through the switch K1, the primary side of the current transformer T1, the capacitor C1 and the ac fan 1; the current of the secondary side of the current transformer T1 returns to the secondary side of the current transformer T1 from the secondary side of the current transformer T1 through the first light-emitting diode D11, the first light-emitting diode D11 is conducted, and the bidirectional input optocoupler U1 outputs low level;
when the alternating current is less than zero, the current on the primary side of the current transformer T1 returns to the alternating current power supply S1 from the alternating current power supply S1 through the capacitor C1, the alternating current fan, the primary side of the current transformer T1 and the switch K1; the current of the secondary side of the current transformer T1 returns to the secondary side of the current transformer T1 from the secondary side of the current transformer T1 through a second light emitting diode D12, the second light emitting diode D12 is conducted, and a bidirectional input optocoupler U1 outputs low level;
when the alternating current is zero, the first light-emitting diode D11 and the second light-emitting diode are not conducted, and the bidirectional input optocoupler U1 outputs high level;
in summary, whether the alternating current fan 1 fails or not can be judged according to the level of the level signal output by the bidirectional input optocoupler U1 in combination with whether the fan driving circuit 3 is driven or not.
The current transformer is adopted in the method, so that the current of the secondary side detection circuit of the transformer is very small, a power device is not needed in the secondary side detection circuit, and meanwhile, the transformer has an isolation function and does not need optical coupling isolation, so that the circuit cost is greatly saved. The voltage drop of the primary side of the current transformer is very small, the current of the secondary side is very small, and the power loss of the whole fault detection circuit is very low. Does not need large packaging devices, saves heat dissipation measures and greatly saves PCB layout and wiring space
The above description is only a preferred embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes, which are made by using the contents of the present specification and the accompanying drawings, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.
Claims (6)
1. A fault detection circuit of an alternating current fan comprises the alternating current fan and a fan control circuit for controlling the alternating current fan, and is characterized in that a thermal protection switch K2 is arranged in the alternating current fan, the fault detection circuit also comprises a fan driving circuit for driving the alternating current fan and a fan fault detection circuit for detecting faults of the alternating current fan; the driving signal output end of the fan control circuit is connected with the driving signal input end of the fan driving circuit, the driving signal output end of the fan driving circuit is connected with the driving signal input end of the alternating current fan, the signal detection end of the fan fault detection circuit is connected with the fan driving circuit, and the detection signal output end of the fan fault detection circuit is connected with the detection signal input end of the fan control circuit;
the fan fault detection circuit comprises a current transformer T1, a diode D1, a diode D2, a diode D3, a diode D4 and a triode Q1, wherein the anode of the diode D1 is connected with the cathode of the diode D2, the anode of the diode D3 is connected with the cathode of the diode D4, the cathode of the diode D1 is connected with the cathode of the diode D3, and the anode of the diode D2 is connected with the anode of the diode D4; the primary side of the current transformer T1 is connected in series with the fan driving circuit, one end of the secondary side of the current transformer T1 is connected with the anode of the diode D1, and the other end of the secondary side of the current transformer T1 is connected with the anode of the diode D3; the base electrode of the triode Q1 is connected with the cathodes of the diode D1 and the diode D3, the emitter electrode of the triode Q1 is connected with the anodes of the diode D2 and the diode D4, and the output end of the triode Q1 is set as the detection signal output end of the fan fault detection circuit.
2. The ac fan fault detection circuit as claimed in claim 1, wherein said fan driving circuit comprises an ac power source S1, a switch K1 and a starting capacitor C1 connected in series, and a primary side of said current transformer T1 is connected in series between said switch K1 and said starting capacitor C1.
3. The ac fan fault detection circuit of claim 2, wherein said ac fan further comprises a start winding L1 and a run winding L2, one end of said thermal protection switch K2 is connected to said ac power source S1, the other end of said thermal protection switch K2 is connected to first ends of said start winding L1 and a run winding L2, respectively, a second end of said start winding L1 is connected to a first end of said start capacitor C1, and a second end of said run winding L2 is connected to a second end of said start capacitor C1.
4. The fault detection circuit of an ac fan according to claim 1, wherein the diodes D1, D2, D3 and D4 are provided as signal diodes.
5. A fault detection circuit of an alternating current fan comprises the alternating current fan and a fan control circuit for controlling the alternating current fan, and is characterized in that a thermal protection switch K2 is arranged in the alternating current fan, the fault detection circuit also comprises a fan driving circuit for driving the alternating current fan and a fan fault detection circuit for detecting faults of the alternating current fan; the driving signal output end of the fan control circuit is connected with the driving signal input end of the fan driving circuit, the driving signal output end of the fan driving circuit is connected with the driving signal input end of the alternating current fan, the signal detection end of the fan fault detection circuit is connected with the fan driving circuit, and the detection signal output end of the fan fault detection circuit is connected with the detection signal input end of the fan control circuit;
the fan fault detection circuit comprises a current transformer T1 and a bidirectional input optocoupler U1, wherein an output end of the bidirectional input optocoupler U1 is set as a detection signal output end of the fan fault detection circuit, a first light emitting diode D11 and a second light emitting diode D12 are arranged in the bidirectional input optocoupler U1, an anode of the first light emitting diode D11 is connected with a cathode of the second light emitting diode D12, a cathode of the first light emitting diode D11 is connected with an anode of the second light emitting diode D12, a primary side of the current transformer T1 is connected with the fan driving circuit in series, and two ends of a secondary side of the current transformer T1 are respectively connected with anodes of the first light emitting diode D11 and the second light emitting diode D12.
6. A method for detecting a fault detection circuit of an ac fan according to any one of claims 1 to 5, wherein a fan control circuit for controlling the ac fan is connected to the ac fan, and a thermal protection switch K2 is incorporated in the ac fan, and the method for detecting a fault of an ac fan includes the steps of:
step S1: judging whether a fan driving circuit of the alternating current fan is normally driven;
step S2: if the fan driving circuit is normally driven, the level of a detection signal sent by the fan fault detection circuit is judged; if the detection signal is high level, the alternating current fan is in failure, and if the detection signal is low level, the alternating current fan is normal;
step S3: if the fan driving circuit is not driven, the level of a detection signal sent by the fan fault detection circuit is judged; if the detection signal is high level, the alternating current fan is normal, and if the detection signal is low level, the alternating current fan is in failure.
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