Automatic temperature control and speed regulation circuit for direct current fan

Abstract

The application relates to a kind of automatic temperature control speed regulation circuit of direct current fan, comprising: first comparator, first voltage dividing circuit, third resistance, first capacitor, second comparator, fourth resistance, thermistor, first MOS tube, diode, second capacitor, PWM output pin, direct current positive output pin and direct current negative output pin, the input end of PWM output pin is connected to the output end of second comparator, the gate of first MOS tube is connected to the output end of second comparator, one of source electrode and drain electrode is grounded, the other is respectively connected to one end of second capacitor, the anode of diode and direct current negative output pin, the other end of second capacitor is respectively connected to the cathode of diode, direct current positive output pin and the anode of first direct current power supply.Compared with prior art, the application has advantages such as wide application range and small size.

Description

Technical Field

[0001] This invention relates to fan control circuits, and more particularly to an automatic temperature control and speed regulation circuit for a DC fan. Background Technology

[0002] DC speed control is currently widely used in fan control, generally consisting of a triangular wave generation module, a comparator module, and a current amplifier module. For example, Chinese patent CN104265670A discloses a DC voltage feedback type PWM temperature control speed control circuit, belonging to the field of DC fan control technology, especially relating to PWM temperature control speed control technology for DC fans. It includes: a temperature detection and amplification circuit composed of an operational amplifier, an operational amplifier bias circuit, a temperature detection circuit, and capacitors; the output of the temperature detection and amplification circuit is connected to a voltage comparator, and the other input of the voltage comparator receives a triangular wave voltage generated by the triangular wave generator; the voltage comparator outputs a PWM signal to the power drive circuit, and the output of the power drive circuit is connected to the DC fan.

[0003] However, DC speed control circuits, including the aforementioned DC voltage feedback type PWM temperature control speed control circuit, generally suffer from at least one of the following drawbacks:

[0004] 1) It needs to be matched with DC fans one by one. The DC speed regulation of different DC fans cannot be used interchangeably, resulting in poor versatility.

[0005] 2) For DC fans without PWM speed control lines, the failure rate is high or the size is large. This paper aims to meet the requirements of both small size and durability.

[0006] 3) It is impossible to simultaneously support both fans with and without PWM speed control lines. Summary of the Invention

[0007] The purpose of this invention is to provide an automatic temperature control and speed regulation circuit for a DC fan.

[0008] The objective of this invention can be achieved through the following technical solutions:

[0009] An automatic temperature control and speed regulation circuit for a DC fan, comprising:

[0010] The system comprises a first comparator, a first voltage divider circuit, a third resistor, and a first capacitor. The inverting input of the first comparator is connected to the host computer through the third resistor, and the non-inverting input is connected to the voltage divider output of the first voltage divider circuit. One end of the first voltage divider circuit is connected to the positive terminal of the first DC power supply, and the other end is grounded. One end of the first capacitor is connected to the inverting input of the first comparator, and the other end is connected to the output of the first comparator.

[0011] The second comparator, the fourth resistor, and the thermistor are connected in series to form a second voltage divider circuit. One input terminal of the second comparator is connected to the output terminal of the first comparator, and the other input terminal is connected to the voltage divider output terminal of the second voltage divider resistor. One end of the second voltage divider resistor is connected to the positive terminal of the first DC power supply, and the other end is grounded.

[0012] The system comprises a first MOSFET, a diode, a second capacitor, a PWM output pin, a DC positive output pin, and a DC negative output pin. The input of the PWM output pin is connected to the output of a second comparator. The gate of the first MOSFET is connected to the output of the second comparator. One of the source and drain is grounded, and the other is connected to one end of the second capacitor, the anode of the diode, and the DC negative output pin, respectively. The other end of the second capacitor is connected to the cathode of the diode, the DC positive output pin, and the positive terminal of the first DC power supply.

[0013] The first voltage divider circuit includes a first resistor and a second resistor, which are connected in series.

[0014] The resistance values ​​of the first resistor and the second resistor are equal.

[0015] The thermistor is a positive temperature coefficient resistor. In the second voltage divider circuit formed by the fourth resistor and the thermistor, the end connected to the positive terminal of the first DC power supply is the fourth resistor.

[0016] A fifth resistor is provided between the second comparator and the first MOSFET.

[0017] The first MOSFET is an N-channel MOSFET.

[0018] The first comparator and the second comparator are integrated on the same integrated circuit.

[0019] The first DC power supply outputs a voltage of 12V.

[0020] The capacitance of the second capacitor is 1000 microfarads.

[0021] The capacitance of the first capacitor is 100 microfarads.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. By designing a first comparator and a second comparator, combined with a second capacitor and a diode, and three output pins, this design is suitable for both DC fans with and without PWM speed control lines. It also improves the voltage stability of the first MOSFET pin, thereby effectively protecting the first MOSFET. It has the advantages of being durable and having a wide range of applications, while also taking into account the overall size.

[0024] 2. The first voltage divider circuit consists of two resistors connected in series, which can provide a more stable voltage.

[0025] 3. The first and second comparators are integrated on the same integrated circuit, further reducing the size.

[0026] 4. The host computer signal is used as the input to the inverting input terminal. The two ends of the first capacitor are connected to the output terminal and the inverting input terminal of the first comparator respectively, thus making it suitable for control signals of different frequencies and further expanding the scope of application. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of the present invention;

[0028] Figure 2 The output signal of the first comparator when the host computer signal frequency is 25kHz;

[0029] Figure 3 The output signal of the first comparator when the host computer signal frequency is 20kHz;

[0030] Figure 4 The output signal of the first comparator when the host computer signal frequency is 15kHz;

[0031] Wherein: R1, first resistor; R2, second resistor; R3, third resistor; R4, fourth resistor; R5, fifth resistor; C1, first capacitor; C2, second capacitor; U1A, first comparator; U1B, second comparator; Q1, first MOSFET; FAN1, first DC fan; FAN2, second DC fan; D1, diode; NTC1, thermistor; PWMout, PWM output pin; FAN+, DC positive output pin; FAN-, DC negative output pin; CLKin, host computer signal. Detailed Implementation

[0032] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0033] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0034] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "proximal," "distal," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Physical quantities in formulas, unless otherwise specified, should be understood as basic quantities in the International System of Units (SI), or derived quantities derived from basic quantities through mathematical operations such as multiplication, division, differentiation, or integration.

[0035] Furthermore, terms such as "horizontal," "vertical," and "sag" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal relative to "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0036] An automatic temperature control and speed regulation circuit for a DC fan, such as Figure 1 As shown, it includes:

[0037] The system consists of a first comparator U1A, a first voltage divider circuit, a third resistor R3, and a first capacitor C1. The inverting input of the first comparator U1A is connected to the host computer through the third resistor R3, and the non-inverting input is connected to the voltage divider output of the first voltage divider circuit. One end of the first voltage divider circuit is connected to the positive terminal of the first DC power supply, and the other end is grounded. One end of the first capacitor C1 is connected to the inverting input of the first comparator U1A, and the other end is connected to the output of the first comparator U1A.

[0038] The second comparator U1B, the fourth resistor R4, and the thermistor NTC1 are connected in series to form the second voltage divider circuit. One input terminal of the second comparator U1B is connected to the output terminal of the first comparator U1A, and the other input terminal is connected to the voltage divider output terminal of the second voltage divider resistor. One end of the second voltage divider resistor is connected to the positive terminal of the first DC power supply, and the other end is grounded.

[0039] The circuit consists of a first MOSFET Q1, a diode D1, a second capacitor C2, a PWM output pin PWMOUT, a DC positive output pin FAN+, and a DC negative output pin FAN-. The input of the PWM output pin PWMOUT is connected to the output of the second comparator U1B. The gate of the first MOSFET Q1 is connected to the output of the second comparator U1B. One of its source and drain is grounded, and the other is connected to one end of the second capacitor C2, the anode of the diode D1, and the DC negative output pin FAN-, respectively. The other end of the second capacitor C2 is connected to the cathode of the diode D1, the DC positive output pin FAN+, and the positive terminal of the first DC power supply, respectively.

[0040] By designing the first comparator U1A and the second comparator U1B, combined with the second capacitor C2 and the diode D1, and three output pins, it is applicable to both DC fans with and without PWM speed control lines. It can also improve the voltage stability of the first MOSFET Q1 pin, thereby effectively protecting the first MOSFET Q1. It has the advantages of being durable and having a wide range of applications, while also taking into account the overall size.

[0041] Furthermore, in this embodiment, the host computer signal CLKin is used as the input to the inverting input terminal. The two ends of the first capacitor C1 are connected to the output terminal and the inverting input terminal of the first comparator U1A, respectively, thus making it suitable for control signals of different frequencies and further broadening its applicability. Of course, in some other embodiments, this part can also adopt a similar approach to that in Chinese patent CN104265670A, that is, replacing the first comparator U1A, the first voltage divider circuit, the third resistor R3, and the first capacitor C1 with a structure that can generate a triangular wave autonomously, but this will reduce its applicability to some extent.

[0042] Specifically, the host computer signal CLKin provided by the host computer is a square wave with a 50% duty cycle, such as... Figures 2 to 4 The images above show square waves with host computer signals CLKin of 25kHz, 20kHz, and 15kHz, respectively. Correspondingly, the output signals of the first comparator U1A are as follows: Figures 2 to 4 As shown in the image below.

[0043] Generally, in most embodiments, the first voltage divider circuit includes a first resistor R1 and a second resistor R2 connected in series. The first voltage divider circuit consists of two resistors connected in series, which can provide a more stable voltage. In this embodiment, the resistance values ​​of the first resistor R1 and the second resistor R2 are equal. Specifically, in all embodiments, the voltage ratio of the first resistor R1 and the second resistor R2 determines the voltage level of the voltage divider output terminal of the first voltage divider circuit, so it can be adjusted according to the actual situation.

[0044] Furthermore, in this application, the thermistor NTC1 is a positive temperature coefficient resistor, and in the second voltage divider circuit formed by the fourth resistor R4 and the thermistor NTC1, the end connected to the positive terminal of the first DC power supply is the fourth resistor R4. In this way, on the one hand, the cost is lower, and on the other hand, it has more stable operating conditions while having multiple outputs and a wider range of applications.

[0045] In addition, in this embodiment, a fifth resistor R5 is provided between the second comparator U1B and the first MOS transistor Q1, and the first MOS transistor Q1 is an N-channel MOS transistor.

[0046] In addition, in this embodiment, the first comparator U1A and the second comparator U1B are integrated on the same integrated circuit, which further reduces the size. The first DC power supply output voltage is 12V, the capacitance of the second capacitor C2 is 1000 microfarads, and the capacitance of the first capacitor C1 is 100 microfarads.

[0047] A square wave with a set frequency and a 50% duty cycle is provided via the host computer signal CLKin. Based on the energy stored in the first capacitor C1, a triangular wave of the same frequency can be output by the first comparator U1A, thus making it suitable for different specifications of fans. Since the resistance of the thermistor NTC1 decreases with increasing temperature, the voltage at the output terminal of the second voltage divider resistor will decrease due to the increased temperature. This increases the duty cycle of the PWM signal output by the second comparator U1B, thereby increasing the duty cycle of the second DC fan FAN2 connected to the PWM output pin PWMOUT. The power is increased, thereby improving the heat dissipation effect. Similarly, for the first fan, the conduction time can be adjusted by the first MOSFET Q1. Unlike the MOSFET in the prior art which is in the amplification operating region, the function of the first MOSFET Q1 in this application is chopping. At this time, combined with the second capacitor C2 and diode D1, the operating voltage of the first MOSFET Q1 can be made more stable. Therefore, the overall circuit function can be more durable and the loss is lower, with the advantage of low energy consumption. The input terminals of the first DC fan FAN1 are connected to the DC positive output pin FAN+ and the DC negative output pin FAN- respectively.

[0048] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

Claims

1. An automatic temperature control and speed regulation circuit for a DC fan, characterized in that, include: The system comprises a first comparator, a first voltage divider circuit, a third resistor, and a first capacitor. The inverting input of the first comparator is connected to the host computer through the third resistor, and the non-inverting input is connected to the voltage divider output of the first voltage divider circuit. One end of the first voltage divider circuit is connected to the positive terminal of the first DC power supply, and the other end is grounded. One end of the first capacitor is connected to the inverting input of the first comparator, and the other end is connected to the output of the first comparator. The second comparator, the fourth resistor, and the thermistor are connected in series to form a second voltage divider circuit. One input terminal of the second comparator is connected to the output terminal of the first comparator, and the other input terminal is connected to the voltage divider output terminal of the second voltage divider resistor. One end of the second voltage divider resistor is connected to the positive terminal of the first DC power supply, and the other end is grounded. The system comprises a first MOSFET, a diode, a second capacitor, a PWM output pin, a DC positive output pin, and a DC negative output pin. The input of the PWM output pin is connected to the output of a second comparator. The gate of the first MOSFET is connected to the output of the second comparator. One of the source and drain is grounded, and the other is connected to one end of the second capacitor, the anode of the diode, and the DC negative output pin, respectively. The other end of the second capacitor is connected to the cathode of the diode, the DC positive output pin, and the positive terminal of the first DC power supply.

2. The automatic temperature control and speed regulation circuit for a DC fan according to claim 1, characterized in that, The first voltage divider circuit includes a first resistor and a second resistor, which are connected in series.

3. The automatic temperature control and speed regulation circuit for a DC fan according to claim 2, characterized in that, The resistance values ​​of the first resistor and the second resistor are equal.

4. The automatic temperature control and speed regulation circuit for a DC fan according to claim 1, characterized in that, The thermistor is a positive temperature coefficient resistor. In the second voltage divider circuit formed by the fourth resistor and the thermistor, the end connected to the positive terminal of the first DC power supply is the fourth resistor.

5. The automatic temperature control and speed regulation circuit for a DC fan according to claim 1, characterized in that, A fifth resistor is provided between the second comparator and the first MOSFET.

6. The automatic temperature control and speed regulation circuit for a DC fan according to claim 1, characterized in that, The first MOSFET is an N-channel MOSFET.

7. The automatic temperature control and speed regulation circuit for a DC fan according to claim 1, characterized in that, The first comparator and the second comparator are integrated on the same integrated circuit.

8. The automatic temperature control and speed regulation circuit for a DC fan according to claim 1, characterized in that, The first DC power supply outputs a voltage of 12V.

9. The automatic temperature control and speed regulation circuit for a DC fan according to claim 1, characterized in that, The capacitance of the second capacitor is 1000 microfarads.

10. The automatic temperature control and speed regulation circuit for a DC fan according to claim 1, characterized in that, The capacitance of the first capacitor is 100 microfarads.

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