CN114079260A

CN114079260A - Fan protection circuit

Info

Publication number: CN114079260A
Application number: CN202010828918.0A
Authority: CN
Inventors: 王永胜; 陈明飞; 范晶荣
Original assignee: Zhejiang Holip Electronic Technology Co Ltd
Current assignee: Zhejiang Holip Electronic Technology Co Ltd
Priority date: 2020-08-17
Filing date: 2020-08-17
Publication date: 2022-02-22

Abstract

A fan protection circuit is disclosed. According to an embodiment, the fan protection circuit may include: a switching device connected in the power supply channel of the fan and configured to turn on or off the power supply channel of the fan according to the validity of the fan control signal; a current sampling section connected in the power supply channel of the fan, configured to sample a current flowing in the power supply channel of the fan; and the self-locking circuit is configured to be triggered to enter a self-locking state when the current sampled by the current sampling component exceeds a preset threshold value, and continuously provide a protection turn-off signal in the self-locking state, wherein the self-locking circuit and the switching device are connected, so that the protection turn-off signal provided by the self-locking circuit can cover the fan control signal and enable the switching device to cut off a power supply channel of the fan. According to the embodiments of the present disclosure, the fan can be reliably cut off without completely cutting off the power supply of the electrical appliance at the time of overcurrent/short circuit, and an overcurrent/short circuit alarm signal can be provided.

Description

Fan protection circuit

Technical Field

The present disclosure relates to the field of electronic circuits, and more particularly, to fan protection circuits with improved performance.

Background

Electrical devices often use (direct current) fans for purposes such as heat dissipation. To avoid fan burn out, it is desirable to provide over-current/short circuit protection. Typically, this function is provided by the power supply of the fan. For example, when the fan is over-current/short-circuit, the power supply triggers over-current/short-circuit protection, and cuts off the power supply. However, this affects the power supply of the entire electrical equipment, so that the electrical equipment cannot normally operate. In addition, the electrical device cannot provide a fan over/short alarm.

Disclosure of Invention

In view of the above, it is an object of the present disclosure, at least in part, to provide a fan protection circuit with improved performance.

According to an embodiment of the present disclosure, there is provided a fan protection circuit including: a switching device connected in the power supply channel of the fan and configured to turn on or off the power supply channel of the fan according to the validity of the fan control signal; a current sampling section connected in the power supply channel of the fan, configured to sample a current flowing in the power supply channel of the fan; and the self-locking circuit is configured to be triggered to enter a self-locking state when the current sampled by the current sampling component exceeds a preset threshold value, and continuously provide a protection turn-off signal in the self-locking state, wherein the self-locking circuit and the switching device are connected, so that the protection turn-off signal provided by the self-locking circuit can cover the fan control signal and enable the switching device to cut off a power supply channel of the fan.

The self-locking circuit may be further configured to provide an alarm signal upon entering the self-locking state.

The fan control signal may be from a controller in the electrical device in which the fan protection circuit is located, and the alarm signal may be sent to the controller. The controller may be electrically isolated from the fan protection circuit.

The self-locking circuit may include a PNP transistor and an NPN transistor, wherein a base of the PNP transistor is connected to a collector of the NPN transistor, and a base of the NPN transistor is connected to the collector of the PNP transistor. The current sampling component may include a resistor, and the resistor may be connected such that a voltage across the resistor is applied to a base-emitter of the NPN transistor, and an emitter of the PNP transistor may be used to provide the alarm signal.

The fan protection circuit may further include an RC filter, wherein the voltage across the resistor may be filtered by the RC filter and then applied to the base-emitter of the NPN transistor.

The fan protection circuit may further include: an amplifier configured to amplify a voltage across the resistor; a comparator configured to compare the amplified voltage with a predetermined reference voltage, wherein an output of the comparator is applied to a base-emitter of the NPN transistor and an emitter of the PNP transistor is used to provide the alarm signal.

The switching device may comprise a control terminal for controlling the switching on or off of the switching device. The fan protection circuit may further include: a first channel for control terminals configured to apply a fan control signal; and a second channel for the control terminal, wherein the self-locking circuit is arranged in the second channel, the self-locking circuit is communicated with the second channel in a self-locking state, and the second channel bypasses the first channel when being communicated.

The self-locking circuit can comprise a thyristor, the anode of the thyristor is used for providing an alarm signal, and the voltage of the current sampling component is applied to the control electrode of the thyristor.

According to an embodiment of the present disclosure, there is provided a fan protection circuit in which a fan is connected between a power supply and ground. The fan protection circuit may include: the first optical coupler part is connected to be switched on or switched off according to the validity of a fan control signal received by the primary side; a switching device connected between the fan and ground; a resistor connected in series with the secondary side of the first optocoupler, connected such that a voltage across the resistor is applied to the control terminal of the switching device; the self-locking circuit is connected with a bypass serving as a resistor and comprises a PNP triode and an NPN triode, wherein the base electrode of the PNP triode is connected to the collector electrode of the NPN triode, and the base electrode of the NPN triode is connected to the collector electrode of the PNP triode; a current sampling resistor connected between the switching device and ground, the current sampling resistor being connected such that a voltage across the current sampling resistor is applied to a base-emitter of the NPN transistor; and the second optical coupler part is connected in such a way that the secondary side is connected with the self-locking circuit in series through the emitting electrode of the PNP triode, and the primary side outputs an alarm signal.

According to the embodiments of the present disclosure, the switching device is provided in the power supply channel of the fan, so that the power supply of the fan can be individually cut off when the overcurrent/short circuit is detected, without completely cutting off the power supply of the electrical appliance. In addition, the self-locking circuit may enter a self-locking state in response to detection of an overcurrent/short circuit, and may continuously provide a protection turn-off signal capable of turning off the switching device in the self-locking state. Thus, the over-current/short-circuit protection function can be locked until the power supply of the fan is restarted or the fan control signal is restarted. In addition, based on the self-locking state of the self-locking circuit, an overcurrent/short circuit alarm signal can be provided.

Drawings

The above and other objects, features and advantages of the present disclosure will become more apparent from the following description of embodiments of the present disclosure with reference to the accompanying drawings, in which:

FIG. 1 schematically illustrates a block diagram of a fan protection circuit according to an embodiment of the disclosure;

FIG. 2 schematically illustrates a circuit diagram of a fan protection circuit according to an embodiment of the present disclosure;

fig. 3 schematically illustrates a circuit diagram of a fan protection circuit according to another embodiment of the present disclosure.

Detailed Description

Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. It should be understood that the description is illustrative only and is not intended to limit the scope of the present disclosure. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present disclosure.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. The words "a", "an" and "the" and the like as used herein are also intended to include the meanings of "a plurality" and "the" unless the context clearly dictates otherwise. Furthermore, the terms "comprises," "comprising," and the like, as used herein, specify the presence of stated features, steps, operations, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, or components.

All terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art unless otherwise defined. It is noted that the terms used herein should be interpreted as having a meaning that is consistent with the context of this specification and should not be interpreted in an idealized or overly formal sense.

Unless expressly indicated otherwise, the numerical parameters set forth in this specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by the present disclosure. In particular, all numbers expressing quantities of ingredients, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term "about". Generally, the expression is meant to encompass variations of a particular quantity, for example ± 10% or more or less in some embodiments.

The use of ordinal numbers such as "first," "second," "third," etc., in the specification and claims to modify a corresponding element does not by itself connote any ordinal number of the element, nor does it denote the order of a particular element or order of importance in a manufacturing process. The use of ordinal numbers is only used to clearly distinguish one element having a certain name from another element having the same name.

Fig. 1 schematically illustrates a block diagram of a fan protection circuit according to an embodiment of the disclosure.

In the block diagram of fig. 1, the fan itself is also shown to more clearly show the connections between the components. It is noted, however, that a fan protection circuit according to embodiments of the present disclosure may not include a fan. For example, a fan protection circuit according to an embodiment of the present disclosure may be integrated into a fan, thereby being provided together with the fan; alternatively, the fan protection circuit according to the embodiments of the present disclosure may be fabricated as a module separate from the fan.

As shown in fig. 1, the fan 101 may be connected between a power supply and ground. That is, there is a current path from the power supply source to ground through the fan 101 (also referred to as a power supply channel of the fan 101). According to an embodiment of the present disclosure, in order to be able to individually control the on and off of the power supply channel of the fan 101, the fan protection circuit 100 may include a switching device 103 connected in the power supply channel. Here, the switching device 103 is shown connected between the fan 101 and ground, since the action of the fan protection circuit 100 with such a connection may be based on the same voltage reference (ground voltage), as will become apparent from the further detailed description below. However, the present disclosure is not limited thereto. For example, the switching device 103 may also be connected between the power supply and the fan 101. A fan control signal from, for example, a controller may be connected to the control terminal of the switching device 103, and may control the switching of the switching device 103, and thus the switching of the power supply channel of the fan 101, according to the validity or non-validity of the fan control signal. Thus, the turning off of the fan 101 can be individually controlled based on the fan control signal without completely cutting off the power supply to the electrical equipment where the fan 101 is located.

In the power supply channel of the fan 101, a current sampling section 105 is also provided. For example, the current sampling part 105 may be connected in series with a fan in the power supply channel. Thus, the current flowing through the fan 101 (or a current related thereto, e.g., proportional) also flows through the current sampling part 105. For example, the current sampling part 105 may be a resistor, and thus may convert a current (flowing through the fan 101) into a voltage. Here, the current sampling section 105 is connected on the ground side, which is for simplifying the circuit configuration because it can operate based on the same voltage reference (ground voltage) as described above.

The sampling signal (e.g. the voltage across the resistor) of the current sampling means 105 may be used as a control signal for the self-locking circuit 107 to trigger the self-locking circuit 107 to enter the self-locking state. By "self-locking" it is meant that after triggering, the state can be maintained until restart, even if the trigger signal disappears. The latching circuit 107 may be implemented in various suitable ways, such as in the form of two transistors connected as described below. In the case of an overcurrent/short circuit, the current sampled by the current sampling section 105 increases (e.g., the voltage across the resistor increases), which may trigger the self-locking circuit 107 when it increases beyond a predetermined threshold.

Based on the self-locking circuit 107 entering the self-locking state, a protection-off signal may be applied to the switching device 103. The protection shutdown signal may override the (override) fan control signal to turn off the switching device 103. Since the self-locking circuit 107 can maintain its own state in the self-locking state, the protection-off signal can be continuously supplied, so that the switching device 103 is always in the off state (i.e., the fan 101 is powered off) until restarting. The override of the fan control signal by the protection shutdown signal may be implemented in various ways, for example, by their connection means or by combinational logic, etc.

In addition, when the self-locking circuit 107 enters the self-locking state, an alarm signal may be provided to, for example, a controller. Thus, the fan may be notified of the occurrence of overcurrent/short circuit to the outside.

The fan protection circuit 100 can be applied to various electrical devices where a fan needs to be disposed, such as a frequency converter, a motor, and the like. In some electrical devices, there may be a division between a low voltage side and a high voltage side depending on the level of operating voltage and safety considerations. For electrical safety, an electrical isolation component, such as an optical coupler, a capacitive coupler, a magnetic coupler, or the like, is usually disposed between the low-voltage side and the high-voltage side to isolate the low-voltage side from the high-voltage side and to transmit signals. According to an embodiment of the present disclosure, such an electrical isolation component may be disposed between the controller and the fan protection circuit 100.

Fig. 2 schematically illustrates a circuit diagram of a fan protection circuit according to an embodiment of the present disclosure.

As shown in fig. 2, the dc FAN1 is connected between the power supply VDD and the ground GND. A diode D1 is connected in reverse parallel to the dc FAN1 for reverse current protection. As described above, in the power supply channel of the dc FAN1, the power MOSFET (metal oxide semiconductor field effect transistor) Q1 serving as a switching device and the resistor R1 serving as a current sampling section are provided.

The FAN control signal FAN _ ON/OFF is applied to the control terminal of the switching device Q1 through the opto-coupler IC 1. For example, the anode of the primary diode of the optocoupler IC1 is connected to the power supply VBB through a resistor R5, and the cathode is connected to the reference voltage UDC-1 through a switching device Q4, such as an NPN transistor. The FAN control signal FAN _ ON/OFF may be applied to a control terminal (e.g., the base of an NPN transistor) of the switching device Q4 through a resistor R6. The secondary side of the optocoupler ICl is connected to the supply voltage VDD via a resistor R4 on the one hand and to ground GND via a resistor R3 on the other hand. The voltage at node a (i.e., the voltage across resistor R3) may be applied to a control terminal of switching device Q1 (e.g., the gate of a power MOSFET).

Here, it is assumed that a high level of the FAN control signal FAN _ ON/OFF indicates that the FAN is turned ON, and a low level indicates that the FAN is turned OFF. When the FAN control signal FAN _ ON/OFF is at a high level, the switching device Q4 is turned ON, and thus the primary side diode of the opto-coupler IC1 is turned ON, and the secondary side is also turned ON. Thus, the voltage at node a (approximately VDD × R3/(R3+ R4)) is "high" (i.e., greater than the threshold voltage of switching device Q1) capable of turning on switching device Q1. Then, the power supply channel of the FAN1 is turned on, and the FAN1 is operated. ON the other hand, when the FAN control signal FAN _ ON/OFF is at a low level, the switching device Q4 is turned OFF, and thus the primary side diode of the optocoupler ICl is turned OFF, and the secondary side is also turned OFF. Thus, the voltage at the a node (about the ground voltage GND) is a "low level" that cannot turn on the switching device Q1 (i.e., less than the threshold voltage of the switching device Q1). Then, the power supply path of FAN1 is turned off, and FAN1 stops operating.

Here, the opto-coupler IC1 transfers the control logic of the FAN control signal FAN _ ON/OFF from the primary side to the a node ON the secondary side, and thus is applied to the switching device Q1. A person skilled in the art may envisage a number of ways of opto-coupling ICl to implement this transfer of control logic.

The current flowing through FAN FAN1 also flows through resistor R1. Thus, the voltage at node C (i.e., the voltage across resistor R1) is proportional to the current flowing through FAN1 and, therefore, may indicate an over/short circuit condition. Specifically, when FAN1 is over-current/short-circuited, the voltage at node C increases (e.g., greater than a threshold determined based on a normal state). The voltage at node C can then be used as a trigger signal for the latch circuit. To avoid the effects of voltage fluctuations (e.g., false triggering), the voltage at node C may be filtered by a filter circuit, such as an RC filter circuit formed by resistor R2 and capacitor C1, and the filtered voltage may be applied to node B (the control terminal of the latch circuit).

In this example, the latching circuit is formed by connecting a PNP transistor Q2 and an NPN transistor Q3. Specifically, the base of PNP transistor Q2 is connected to the collector of NPN transistor Q3, and the base of NPN transistor Q3 is connected to the collector of PNP transistor Q2 at node B. The emitter of the PNP transistor Q2 and the emitter of the NPN transistor Q3 serve as input/output terminals of the latch circuit. Here, an emitter of the PNP transistor Q2 is connected to the power supply VDD (via other components, which will be described below), and an emitter of the NPN transistor Q3 is connected to the ground GND.

When the voltage at node B is above the threshold voltage of NPN transistor Q3, NPN transistor Q3 turns on, and PNP transistor Q2 turns on by pulling the base of PNP transistor Q2 down to ground. On the other hand, when the PNP transistor Q2 is turned on, the base (i.e., node B) of the NPN transistor Q3 may be pulled up to a certain voltage (depending on the connection member between the emitter of the PNP transistor Q2 and the power supply VDD), so that the NPN transistor Q3 is turned on. In this way, PNP transistor Q2 and NPN transistor Q3 achieve self-locking (similar to a thyristor). In this state, PNP transistor Q2 and NPN transistor Q3 remain in a conductive state at all times even if the voltage at node C returns to normal (i.e., after filtering is no higher than the threshold voltage of NPN transistor Q3). The PNP transistor Q2 and the NPN transistor Q3 release the latch-up state only when the power supply VDD or the FAN control signal FAN _ ON/OFF is restarted.

The resistance value of the resistor R1 may be set based on the threshold voltage of the NPN transistor Q3, the current (e.g., the nominal current) in the normal state of the FAN 1.

Here, in order to cover the fan control signal by the latch circuit, the latch circuit is connected between the node a and the ground GND in parallel with the resistor R3. That is, the self-locking circuit may bypass the resistor R3 after entering the self-locking state, and thus may override the fan control signal applied through the resistor R3. More specifically, the latch circuit pulls down the voltage at the node a to the ground GND in the latch state, thereby applying a low-level signal to the control terminal of the switching device Q1. In other words, for node a (control terminal of switching device Q1), two channels may be provided: the channel in which resistor R3 is located, may apply a fan control signal (or equivalent logic) to the control terminal of switching device Q1; the channel where the self-locking circuit is located can bypass the previous channel in the self-locking state, so that the switching device Q1 is no longer controlled by the FAN control signal, but is turned off to turn off the FAN 1.

Here, in order to realize the alarm function, an optical coupler IC2 is further provided. For example, one input/output terminal of the latch circuit (the emitter of the PNP transistor Q2) is connected to the node a via the primary diode of the optocoupler IC 2. In addition, the secondary side of the optocoupler IC2 is connected to the supply voltage VBB through a resistor R7 on the one hand and to the reference voltage UDC-1 through a resistor R8 on the other hand. In a normal state, a primary side diode of the optocoupler IC2 is cut off, so that a secondary side is also cut off, and an overcurrent/short circuit alarm signal can be at a low level. On the other hand, when the overcurrent/short circuit is detected, the self-locking circuit enters a self-locking state, so that a primary side diode of the optocoupler IC2 is conducted, a secondary side is also conducted, and an overcurrent/short circuit alarm signal can be at a high level.

Here, the optocoupler IC2 transmits the state of the latch circuit from the primary side to the secondary side. Those skilled in the art may envision a variety of ways for optocoupler IC2 to achieve this transfer.

According to the embodiment, the overcurrent/short circuit protection can be realized by using fewer devices. The circuit is simple, the cost is low, the reliability is high, and the protection delay is small.

In the above embodiments, the self-locking circuit is implemented using two triode strings in series. However, the present disclosure is not limited thereto. For example, a thyristor may be used to implement the self-locking circuit. The sampled voltage (the voltage across resistor R1) may be applied to the gate of the thyristor, and the anode of the thyristor may be used to provide an alarm signal. More specifically, the node B shown in fig. 2 may correspond to the control electrode of the thyristor, the emitter of the PNP transistor Q2 may correspond to the anode of the thyristor, and the emitter of the NPN transistor Q3 may correspond to the cathode of the thyristor.

The circuit of fig. 3 is substantially the same as the circuit of fig. 2, except for the manner in which the voltage is applied from node C to the control node B of the latching circuit. Hereinafter, differences between the two embodiments will be mainly described.

Specifically, the voltage across the sampling resistor R1 is applied to the amplifier IC4 through the resistors R7, R8 to be amplified. In this example, the amplifier may be an operational amplifier with a feedback resistor R9 and a capacitor C1 connected. The amplified voltage is obtained at the node D and fed to the comparator IC3 via the resistor R10 to be compared with the reference voltage obtained by dividing the resistors R11 and R12. The output of the comparator IC3 may be pulled up to the power supply VDD through a pull-up resistor R2 and may be applied to the node B via an RC filter circuit composed of, for example, a resistor R13 and a capacitor C12. When overcurrent/short circuit occurs, the output of the comparator IC3 can be at high level, and therefore, the NPN transistor Q3 can be turned on, so that the self-locking circuit enters a self-locking state.

The resistance value of the resistor R1 may be set based on the current (e.g., nominal current) in the normal state of the FAN1, the gain of the amplifier, and the voltage division ratio of the voltage division resistors R11 and R12.

In this embodiment, due to the presence of the amplifier, the voltage drop across the sampling resistor R1 can be low, the loss can be reduced, the design parameters can be adjusted conveniently, the accuracy of the over-current/short-circuit protection trigger value is high, and the temperature drift is small.

The embodiments of the present disclosure have been described above. However, these examples are for illustrative purposes only and are not intended to limit the scope of the present disclosure. Although the embodiments are described separately above, this does not mean that the measures in the embodiments cannot be used in advantageous combination. The scope of the disclosure is defined by the appended claims and equivalents thereof. Various alternatives and modifications can be devised by those skilled in the art without departing from the scope of the present disclosure, and such alternatives and modifications are intended to be within the scope of the present disclosure.

Claims

1. A fan protection circuit, comprising:

a switching device connected in the power supply channel of the fan and configured to turn on or off the power supply channel of the fan according to the validity of the fan control signal;

a current sampling section connected in the power supply channel of the fan, configured to sample a current flowing in the power supply channel of the fan;

a self-locking circuit configured to be triggered to enter a self-locking state when the current sampled by the current sampling part exceeds a predetermined threshold value, and continuously provide a protection off signal in the self-locking state,

the self-locking circuit and the switch device are connected to provide the protection turn-off signal for the self-locking circuit, so that the fan control signal can be covered by the protection turn-off signal, and the switch device can disconnect a power supply channel of the fan.

2. The fan protection circuit of claim 1, wherein the self-locking circuit is further configured to provide an alarm signal upon entering a self-locking state.

3. The fan protection circuit of claim 2, wherein the fan control signal is from a controller in an electrical device in which the fan protection circuit is located, the alarm signal being sent to the controller.

4. The fan protection circuit of claim 3, wherein the controller is electrically isolated from the fan protection circuit.

5. The fan protection circuit of claim 1, wherein the self-locking circuit comprises:

the base electrode of the PNP triode is connected to the collector electrode of the NPN triode, and the base electrode of the NPN triode is connected to the collector electrode of the PNP triode.

6. The fan protection circuit of claim 5,

the current sampling means comprises a resistor which is,

the resistor is connected such that the voltage across the resistor is applied to the base-emitter of the NPN transistor and the emitter of the PNP transistor is used to provide an alarm signal.

7. The fan protection circuit of claim 6, further comprising:

an RC filter, wherein the voltage across the resistor is applied to the base-emitter of the NPN triode after being filtered by the RC filter.

8. The fan protection circuit of claim 6, further comprising:

an amplifier configured to amplify a voltage across the resistor;

a comparator configured to compare the amplified voltage with a predetermined reference voltage,

wherein the output of the comparator is applied to the base-emitter of the NPN transistor, and the emitter of the PNP transistor is used for providing an alarm signal.

9. The fan protection circuit of claim 1, wherein the switching device includes a control terminal for controlling turning on or off of the switching device,

the fan protection circuit further includes:

a first channel for the control terminal configured to apply the fan control signal; and

and the self-locking circuit is arranged in the second channel, the self-locking circuit is communicated with the second channel in a self-locking state, and the second channel bypasses the first channel when being communicated.

10. The fan protection circuit according to claim 1, wherein the self-locking circuit comprises a thyristor, an anode of the thyristor is used for providing an alarm signal, and a control electrode of the thyristor is applied with the voltage of the current sampling component.

11. A fan protection circuit in which a fan is connected between a power supply and ground, the fan protection circuit comprising:

the first optical coupler part is connected to be switched on or switched off according to the validity of a fan control signal received by the primary side;

a switching device connected between the fan and ground;

a resistor connected in series with the secondary side of the first optocoupler component, connected such that a voltage across the resistor is applied to a control terminal of the switching device;

the self-locking circuit is connected as a bypass of the resistor and comprises a PNP triode and an NPN triode, wherein the base electrode of the PNP triode is connected to the collector electrode of the NPN triode, and the base electrode of the NPN triode is connected to the collector electrode of the PNP triode;

a current sampling resistor connected between the switching device and ground such that a voltage across the current sampling resistor is applied to a base-emitter of the NPN transistor;

and the second optical coupler part is connected in such a way that the secondary side is connected with the self-locking circuit in series through the emitting electrode of the PNP triode, and the primary side outputs an alarm signal.