A fan control circuit with overcurrent and short-circuit protection functions

Abstract

The present invention discloses a fan control circuit with overcurrent and short-circuit protection functions, comprising a power supply module and a switch module, and also comprising a fault signal output module. The fault signal output module comprises a current acquisition circuit and a comparison circuit; the current acquisition circuit comprises a sampling resistor R6, which is connected in series to the switch module; the comparison circuit comprises resistors R15, R16, R17, a comparator U1A, and a comparator U1B, wherein the resistors R15, R17, and R16 are connected in series between a power supply and a ground, respectively; the comparators U1A and U1B form a window comparator, the upper and lower limit comparison voltage input pins of the window comparator are respectively connected to the two ends of the resistor R17, the input end of the window comparator is connected to the sampling resistor R6, and the output end of the window comparator can output a fault signal. This circuit can output a fault signal in a timely manner when the fan is operating abnormally, facilitating maintenance.

Description

Technical Field

[0001] The present invention relates to the technical field of machine tool cooling fan control, and in particular to a fan control circuit with overcurrent and short-circuit protection functions. Background Art

[0002] With the rapid advancement of electronic technology, electronic components are becoming increasingly smaller and denser, while their power levels are also increasing. This leads to a continuous increase in the amount of heat generated per unit area of electronic products. If this heat cannot be dissipated promptly, localized high temperatures will form, causing electronic components to malfunction, impacting their operational stability and lifespan. Product heat dissipation capacity is crucial, and air-cooled designs continue to lead advancements and innovations in the cooling system market, but this also impacts product operational stability. To increase product heat dissipation capacity, fans are often added to products to dissipate heat when temperatures rise too high. However, existing fan control circuits lack fault detection capabilities, making it impossible to detect and address fan failures in a timely manner, resulting in damage to the product or fan. Summary of the Invention

[0003] The present invention provides a fan control circuit with overcurrent and short-circuit protection functions, which solves the problem that the existing fan circuit cannot detect fan operation failures.

[0004] The technical means adopted in the present invention are as follows:

[0005] A fan control circuit with overcurrent and short-circuit protection functions includes a power supply module and a switch module, and also includes a fault signal output module. The fault signal output module includes a current acquisition circuit for acquiring control circuit current and a comparison circuit for determining the operating status of the fan; the current acquisition circuit includes a sampling resistor R6, and the sampling resistor R6 is connected in series in the switch module; the comparison circuit includes a resistor R15, a resistor R16, a resistor R17, a comparator U1A, and a comparator U1B, wherein the resistors R15, R17, and R16 are connected in series between a power supply and a ground, and the comparators U1A and U1B constitute a window comparator. The upper and lower limit comparison voltage input pins of the window comparator are respectively connected to the two ends of the resistor R17, the input end of the window comparator is connected to the sampling resistor R6, and the output end of the window comparator can output a fault signal.

[0006] Furthermore, an overcurrent protection circuit is included. The overcurrent protection circuit includes a transistor U4. The base of the transistor U4 is connected to the sampling resistor R6, the emitter is grounded, and the collector is connected to the control end of the switch module.

[0007] Furthermore, a low-pass filter circuit is provided in the overcurrent protection circuit. The low-pass filter circuit includes a resistor R5 and a capacitor C5. The resistor R5 is connected in series between the base of the transistor U4 and the sampling resistor R6. The capacitor C5 is connected in parallel between the base of the transistor U4 and the ground.

[0008] Furthermore, it also includes a short-circuit protection circuit, which includes a resistor R2, a capacitor C3, a voltage-stabilizing diode D3, a resistor R11 and a transistor U5; one end of the resistor R2 is connected to one end of the fan, and the other end is connected to the cathode of the voltage-stabilizing diode D3 and one end of the capacitor C3, the anode of the voltage-stabilizing diode D3 is connected to one end of the resistor R11 and the base of the transistor U5, the other end of the resistor R11 is grounded, the emitter of the transistor U5 is grounded, and the collector is connected to the control end of the switch module.

[0009] Furthermore, it also includes a short-circuit protection auxiliary circuit, which includes a resistor R3, a resistor R10 and a transistor U3. One end of the resistor R3 is connected to the control signal, and the other end is connected to one end of the resistor R10 and the base of the transistor U3. The other end of the resistor R10 is grounded, the emitter of the transistor U3 is grounded, and the collector is connected to the cathode of the voltage regulator D3.

[0010] Compared with the prior art, the fan control circuit with overcurrent and short-circuit protection functions described in the present invention has the following advantages: by providing a current acquisition circuit and a window comparison circuit, the operating current of the fan can be acquired by the current acquisition circuit, and the normal operation of the fan can be determined by the comparison circuit. At the same time, when the fan operates abnormally, a fault signal is issued by the window comparator, and an alarm information can be issued in a timely manner. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 A circuit block diagram of the fan control circuit disclosed in the present invention;

[0012] Figure 2 This is a structural diagram of the fan control circuit disclosed in the present invention.

[0013] In the figure: 1. Power supply module, 3. Fault signal output module, 4. Overcurrent protection circuit, 5. Short-circuit protection circuit. DETAILED DESCRIPTION

[0014] like Figure 1 and Figure 2The fan control circuit with overcurrent and short-circuit protection functions disclosed in the present invention is shown, including a power supply module 1 and a switch module. The power supply module includes a diode D1 and a voltage regulator D2. The anode of the diode D1 is connected to the +24V power supply, and the cathode is connected to the input end of the fan to power the fan. The voltage regulator D2 is connected between the cathode of the diode D1 and the ground to ensure the stability of the voltage input to the fan. The switch module includes a resistor R8, a resistor R9, a transistor U2, a MOS transistor Q1, a resistor R1 and a resistor R12. One end of the resistor R8 is connected to the control signal, and the other end is connected to the One end of resistor R9 is connected to the base of transistor U2, and the other end of resistor R9 is grounded. The emitter of transistor U2 is grounded, and the collector is connected to the gate of MOS transistor Q1. One end of resistor R1 is connected to the cathode of diode D1, and the other end is connected to one end of resistor R12 and the gate of MOS transistor Q1. The other end of resistor R12 is grounded. Resistors R1 and R2 form a voltage divider circuit for providing a turn-on voltage for MOS transistor Q1. The drain of MOS transistor Q1 is connected to the fan, and the source is connected to ground. In this embodiment, the MOS transistor is model IRFR24N15D.

[0015] The circuit also includes a fault signal output module 3, which includes a sampling resistor R6, a resistor R15, a resistor R16, a resistor R17, a comparator U1A and a comparator U1B. The sampling resistor R6 is connected between the source of the MOS tube and the ground to collect the current flowing through the MOS tube Q1 to form a sampling voltage. The resistors R15, R17 and R16 are connected in series to form a voltage divider circuit. The other end of the resistor R15 is connected to the power supply. In this embodiment, one end of the resistor R15 is connected to the 3.3V power supply, and the other end of the resistor R16 is grounded. The comparator U1A and the comparator U1B form a window comparator. The non-inverting input end of the comparator U1A is connected to the common end of the resistor R15 and the resistor R17 to set the upper limit comparison voltage of the threshold comparator. In this embodiment, the upper limit comparison voltage is set to 0.84V. The inverting input end of the comparator U1B is connected to the common end of the resistor R15 and the resistor R17 to set the upper limit comparison voltage of the threshold comparator. The terminal is connected to the common terminal of resistors R17 and R16 and is used to set the lower limit comparison voltage of the threshold comparator. In this embodiment, the lower limit comparison voltage is set to 0.08V. The inverting input of comparator U1A and the non-inverting input of comparator U1B are connected to the source of MOS transistor Q1. Sampling resistor R6 collects the current in MOS transistor Q1 to form a sampled voltage. This sampled voltage on sampling resistor R6 is compared with the upper and lower limit voltages of the threshold comparator. The output of the threshold comparator is connected to a controller (not shown in the figure), which is connected to an alarm module. When the fan operates abnormally, with excessive or insufficient current, the sampled voltage on sampling resistor R6 will be greater than 0.84V or less than 0.08V. At this time, the threshold comparator outputs a fault signal (the FAN_BACK signal in the figure) to the controller, which issues a fault alarm upon receiving the fault signal. A filter capacitor C6 is also provided between the inverting input of comparator U1A and ground.

[0016] Furthermore, an overcurrent protection circuit 4 is included. The overcurrent protection circuit 4 includes a transistor U4. The base of the transistor U4 is connected to the source of the MOS transistor Q1, the emitter is grounded, and the collector is connected to the gate of the MOS transistor Q1. The sampling voltage of the sampling resistor R6 is used as the operating voltage of the transistor U4. When the fan is working normally, the voltage on the sampling resistor R6 is lower than the conduction voltage of the transistor U4, the transistor U4 is disconnected, and the MOS transistor Q1 controls the switch of the fan. When an overcurrent occurs in the circuit, the voltage on the sampling resistor R6 is higher than the conduction voltage of the transistor U4. When the transistor U4 is turned on, the gate of the MOS transistor Q1 is pulled low, and the MOS transistor Q1 is turned off, thereby controlling the fan to stop working to prevent the fan from being damaged due to long-term overcurrent operation. Furthermore, a low-pass filter circuit is also provided in the overcurrent protection circuit. The low-pass filter circuit includes a resistor R5 and a capacitor C5. The resistor R5 is connected in series between the base of the transistor U4 and the source of the MOS transistor, and the capacitor C5 is connected in parallel between the base of the transistor U4 and the ground. When the fan is working, current fluctuations may occur in the circuit. The low-pass filter circuit is used to prevent the transistor U4 from malfunctioning.

[0017] Furthermore, the switch module further includes a short-circuit protection circuit 5, which includes a resistor R2, a capacitor C3, a voltage regulator D3, a resistor R11, and a transistor U5. One end of the resistor R2 is connected to one end of the fan, and the other end is connected to the cathode of the voltage regulator D3 and one end of the capacitor C3. The anode of the voltage regulator D3 is connected to one end of the resistor R11 and the base of the transistor U5. The other end of the resistor R11 is grounded. The emitter of the transistor U5 is grounded, and the collector is connected to the control end of the switch module. When the fan short-circuits, the voltage at the cathode of the voltage regulator D3 approaches the power supply voltage (24V). At this time, the resistor R2, the voltage regulator D3, and the resistor R11 form a voltage divider circuit, so that the anode terminal voltage of the voltage regulator D3 is higher than the conduction voltage of the transistor U5. The transistor U5 is turned on, which in turn pulls down the gate voltage of the MOS transistor Q1, turning off the MOS transistor and stopping the fan. Resistor R2 and capacitor C3 are also included. These two components form a charging circuit that slows down the voltage rise at D3's cathode, thereby reducing the turn-on speed of U5's base and ensuring proper fan startup. Because the fan itself takes time to start, the RC charging circuit formed by C3 and R2 must match the fan's startup timing. If the RC time is less than the fan startup time, U5 may unexpectedly turn on and Q1 may turn off during the fan startup process, resulting in an abnormal startup.

[0018] Furthermore, it also includes a short-circuit protection auxiliary circuit, which includes a resistor R3, a resistor R10 and a transistor U3. One end of the resistor R3 is connected to the control signal, and the other end is connected to one end of the resistor R10 and the base of the transistor U3. The other end of the resistor R10 is grounded, the emitter of the transistor U3 is grounded, and the collector is connected to the cathode of the voltage regulator D3. When the control signal input is a high level, the transistor U3 is turned on, and the charge on the capacitor C3 can be released through the transistor U3. When the fan is turned off, the charge on the capacitor C3 can be released to prevent malfunction of the circuit.

[0019] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A fan control circuit with overcurrent and short-circuit protection functions, including a power supply module and a switch module, characterized in that: It also includes a fault signal output module, which includes a current acquisition circuit for acquiring the current of the control circuit and a comparison circuit for judging the working state of the fan; The current acquisition circuit includes a sampling resistor R6, and the sampling resistor R6 is connected in series with the switch module; The comparison circuit includes a resistor R15, a resistor R16, a resistor R17, a comparator U1A, and a comparator U1B. The resistor R15, the resistor R17, and the resistor R16 are sequentially connected in series between the power supply and the ground. The comparator U1A and the comparator U1B constitute a window comparator. The upper and lower limit comparison voltage input pins of the window comparator are respectively connected to the two ends of the resistor R17. The input end of the window comparator is connected to the sampling resistor R6. The output end of the window comparator can output a fault signal. It also includes a short-circuit protection circuit, which includes a resistor R2, a capacitor C3, a voltage-stabilizing diode D3, a resistor R11, and a transistor U5; one end of the resistor R2 is connected to one end of the fan, the other end of the resistor R2 is connected to the cathode of the voltage-stabilizing diode D3 and one end of the capacitor C3, the other end of the capacitor C3 is grounded, the anode of the voltage-stabilizing diode D3 is connected to one end of the resistor R11 and the base of the transistor U5, the other end of the resistor R11 is grounded, the emitter of the transistor U5 is grounded, and the collector is connected to the control end of the switch module; It also includes a short-circuit protection auxiliary circuit, which includes a resistor R3, a resistor R10 and a transistor U3. One end of the resistor R3 is connected to the control signal, and the other end is connected to one end of the resistor R10 and the base of the transistor U3. The other end of the resistor R10 is grounded, the emitter of the transistor U3 is grounded, and the collector is connected to the cathode of the voltage regulator D3.

2. The fan control circuit with overcurrent and short-circuit protection functions according to claim 1, characterized in that: It also includes an overcurrent protection circuit, which includes a transistor U4. The base of the transistor U4 is connected to the sampling resistor R6, the emitter is grounded, and the collector is connected to the control end of the switch module.

3. The fan control circuit with overcurrent and short-circuit protection functions according to claim 2, characterized in that: The overcurrent protection circuit is further provided with a low-pass filter circuit, which includes a resistor R5 and a capacitor C5. The resistor R5 is connected in series between the base of the transistor U4 and the sampling resistor R6, and the capacitor C5 is connected in parallel between the base of the transistor U4 and the ground.

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