CN1741364A - Linear rotating speed control circuit for fan motor - Google Patents

Abstract

A linear speed control circuit for a fan motor is disclosed. The control circuit comprises a digital-analog conversion unit, a square wave generation unit, an integration unit and a comparison unit. The digital-to-analog conversion unit receives a pulse width modulation signal and converts the pulse width modulation signal into an analog signal, and a triangular wave signal is generated through the square wave generation unit and the integration unit. The analog signal and the triangular wave signal are received by the comparison unit and output a digital signal for controlling the rotating speed of the fan motor, so that the rotating speed of the fan motor is in direct proportion to the working period of the pulse width modulation signal.

Description

A linear speed control circuit for fan motor

technical field

The invention relates to a speed control circuit, in particular to a linear speed control circuit for a fan motor.

Background technique

In the known fan motor speed control technology, those skilled in the art usually use a control circuit composed of various transistors and drive integrated circuit (integrated circuit; IC) chips and an external drive signal, such as pulse width modulation ( Pulse Width Modulation (PWM) signal to control the speed of the fan motor.

Please refer to FIG. 1A. In a known fan motor speed control technology, a PWM signal input circuit 2 is usually used to drive the drive IC4, thereby controlling the terminal voltage of the fan motor (indicated by M in the figure) 1, and the Hall component (Denoted by H in the figure) 3 is used to detect the magnetic poles of the rotor (not shown) of the fan motor 1 so that the current direction of the stator coil (not shown) of the fan motor 1 matches the position of the rotor magnetic poles.

Please refer to FIG. 1B , a digital/analog conversion circuit (indicated by D→A in the figure) 5 can also be used to convert a PWM signal into an analog signal, which can be used as a reference for the driving IC 4 to control the speed of the fan motor 1 . In this way, the noise problem caused by the vibration generated during the switching process of fan motor stop/activation can be effectively reduced when the PWM signal is low in frequency.

However, as shown in the curve (a) or (b) of FIG. 1C, in the above-mentioned known technology, the working curve between a PWM signal and the fan motor speed is always nonlinear. The high-low level duty cycle of the input PWM signal is not linearly proportional to the fan motor speed ratio. For example, in FIG. 1C , when the duty cycle of the high (or low) level of the input PWM signal is 50%, the obtained fan motor speed ratio will not be 50%. In this way, the obtained fan motor speed cannot meet the requirements, resulting in a decrease in the fan motor speed and a decrease in fan efficiency.

A conventional fan motor speed control circuit cannot avoid the non-linear relationship between an input pulse width modulation (PWM) signal and an output speed, thus causing a decrease in the speed of the fan motor and reducing fan efficiency.

Contents of the invention

In order to solve this problem, the present invention proposes a linear speed control circuit for fan motors, which can maintain a linear relationship between the output speed of the fan motor and the input pulse width modulation signal, and satisfy various input pulse widths. Modulation signal and various fan motor load requirements.

The invention provides a linear speed control circuit for a fan motor, which implements the linear speed control of the fan motor by converting a digital-to-analog signal and comparing a triangular wave reference signal.

A linear speed control circuit for a fan motor according to an embodiment of the present invention includes a digital-to-analog conversion unit, a square wave generation unit, an integration unit and a comparison unit. The digital-to-analog converting unit receives a pulse width modulation signal and converts it into an analog signal, and generates a triangular wave signal through the square wave generating unit and the integrating unit. The analog signal and the triangular wave signal are received by the comparison unit to output a digital signal for controlling the rotation speed of the fan motor, so that the rotation speed of the fan motor is directly proportional to the duty cycle of the pulse width modulation signal.

Since there is a linear proportional relationship between the fan motor rotational speed change and the input pulse width modulation signal, the present invention has the advantage of being convenient for the user to control the motor rotational speed and adapt to the user's needs to obtain a reliable rotational speed output without the need for a fan motor. Disadvantages of reduced efficiency. In addition, due to the configuration of the digital-to-analog conversion unit, the present invention also reduces the known vibration and noise problems caused by a control circuit directly driven by a low-frequency pulse width modulation signal to the fan motor.

In order to make the above and other objects, features, and advantages of the present invention more comprehensible, a preferred embodiment is specifically cited below and described in detail with reference to the accompanying drawings.

Description of drawings

FIG. 1A is a block diagram showing the basic structure of a conventional fan motor rotation speed control circuit.

FIG. 1B is a block diagram showing the basic structure of another conventional fan motor rotation speed control circuit.

FIG. 1C is a graph showing the relationship between the known fan motor speed and the duty cycle of its PWM signal.

FIG. 2A is a block diagram showing the basic structure of the linear speed control circuit for the fan motor of the present invention.

FIG. 2B is a schematic diagram showing a linear speed control circuit for a fan motor according to an embodiment of the present invention.

2C is a graph showing the voltage level of the reference triangular waveform generated by the linear speed control circuit for the fan motor according to the present invention as a function of time.

FIG. 2D is a graph showing the relationship between the rotation speed of the fan motor and the duty cycle of the pulse width modulation signal of the present invention.

Description of reference symbols

1, 40: motor; 2: PWM signal input circuit; 3, 20: Hall component; 4, 30: driver IC; 5, 101: digital-to-analog signal conversion unit; 10: linear speed control circuit; 102: square wave generation Unit; 103: Integral unit; 104～comparison unit; 105: Triangular wave generating unit; 11: Pulse width modulation signal; 12: Analog signal; 13: Square wave signal; 14, 230: Triangular wave signal; 15, 231: Digital signal; 220, 34, 41: DC voltage source; 221: transistor; 222, 42, 43: diode; 223, 44: capacitor; 224a～224c, 33a～33e, 46, 47, 48, 53a, 53b: resistor; 225 : Pulse width modulation signal input terminal; 226, 31, 32, 45, 49: Applied voltage connection terminal; 227: Analog signal output terminal; 228: Pulse width modulation signal; 229: Analog signal; 50: Triangular wave signal output terminal; 51a , 51b: signal input terminal; 52: voltage control voltage source; 54: signal output terminal; 55, 56: P-channel MOSFET.

Detailed ways

Please refer to FIG. 2A, the linear speed control circuit 10 for the fan motor (indicated by M in the figure) 40 of the present invention includes a digital/analog conversion unit (indicated by D/A in the figure) 101, a square wave generating unit 102, An integrating unit 103 and a comparing unit 104 . The fan motor 40 is also connected to a driver IC 30 and a Hall element (indicated by H in the figure) 20 , and the connection relationship is known, and will not be repeated here.

The digital/analog conversion unit 101 is used for converting the received PWM signal 11 into an analog signal 12, the square wave generation unit 102 is used for generating a reference square wave signal 13 and the integration unit 103 is used for converting the reference square wave signal 13 into a reference triangular wave signal 14. The comparison unit 104 is used to receive the analog signal 12 and the triangular wave signal 14, and output a digital signal 15 for controlling the speed of the fan motor after comparing their voltage levels. In addition, the square wave generating unit 102 and the integrating unit 103 can be directly replaced by the triangular wave generating unit 105 .

A linear speed control circuit 10 for a fan motor according to an embodiment of the present invention is shown in FIG. 2B . In this embodiment, the digital-to-analog signal conversion unit 101 is composed of a transistor 221, a diode 222, a capacitor 223, several resistors 224a-224c, a PWM signal input terminal 225, an applied voltage input terminal 226, and an analog signal output terminal 227. The square wave generating unit 102 is composed of an external voltage input terminal 31, a voltage control voltage source 32, and several resistors 33a-33e, wherein the resistance values of the resistors 33d and 33e are R ₁ and R ₂ respectively. Integrating unit 103 is made up of diode 42 and 43, capacitor 44, voltage control voltage source 45, several resistors 46～48, applied voltage input end 49 and signal output end 50, and comparison unit 104 is made up of signal input end 51a and 51b, The voltage control voltage source 52 , resistors 53 a and 53 b and a digital signal output terminal 54 are composed.

The applied voltage input terminal 226 of the digital-to-analog signal conversion unit 101 is connected to a DC voltage source 220 , and its voltage value is denoted by V ₁ . The analog signal output terminal 227 of the digital-to-analog signal conversion unit 101 is connected to the signal input terminal 51 a of the comparison unit 104 . The applied voltage input terminal 31 of the square wave generating unit 102 is connected to a DC voltage source 34, and its voltage value is represented by _VR . The square wave generating unit 102 is connected to the integrating unit 103, the applied voltage input terminal 49 of the integrating unit 103 is connected to the DC voltage source 41, and its voltage value is represented by V ₊ , and the signal output terminal 50 is connected to the signal input terminal 51b of the comparing unit 104. The digital signal output end 54 of the comparison unit 104 is also connected to the gates of two independent P channel Metal-Oxide-Semiconductor Field Effect Transistors (P channel Metal-Oxide-Semiconductor Ficld Effect Transistor; PMOSFET) 55 and 56, and the PMOSFET55 and The drain terminals A and B of 56 are respectively connected to the two connecting lines between the driving IC 30 and the motor 40 in FIG. 2A . Wherein, the PMOSFETs 55 and 56 can also be changed to N-channel depletion metal-oxide-semiconductor field effect transistors or other types of transistors according to actual requirements.

Please refer to FIG. 2B and FIG. 2C , the working principle of the linear speed control circuit 10 for the fan motor in this embodiment is as follows:

First, the input pulse width modulation signal 228 will be converted into an analog signal 229 by the digital-to-analog signal conversion circuit 101, and then received by the comparison unit 104 through the signal input terminal 51a. The voltage level of the analog signal 229 is represented by V _A . At the same time, through the functions of the square wave generation unit 102 and the integration unit 103, a triangular wave signal 230 can be generated at the signal output terminal 50, and can be received by the comparison unit 104 through the signal input terminal 51b. The voltage level of the triangular wave signal 230 is as follows: V _x said.

Secondly, the comparison unit 104 will compare the voltage level V _A of the analog signal 229 and the voltage level V _x of the triangular wave signal 230, and output a low-level digital signal when V _x is greater than the minimum value V _min of V _x and less than V _A , output a high-level digital signal when V _x is greater than VA _and less than the maximum value V _max of V _x . Therefore, a digital signal 231 is output at the digital signal output terminal 54 .

Then, this digital signal 231 is utilized to drive the PMOSFETs 55 and 56, and then drive the fan motor 40 to control the rotation speed.

Please refer to FIG. 2C, since the period T (including T ₁ and T ₂ ), the peak value of the voltage level V _max and the valley value of the voltage level V _min of the above-mentioned triangular wave signal 230 can be adjusted by adjusting _VR , R ₁ , R ₂ and V ₊ Therefore, it can adapt to the change of the pulse width modulation signal 228 in different application modes, adjust VR, _{R 1} , R ₂ and V ₊ to change the waveform of the triangular wave signal 230, and then compensate the part of the nonlinear variable to achieve linear control of the fan The purpose of the rotational speed of the motor 40 .

In this embodiment, the relationship between the duty cycle of the pulse width modulation signal 228 and the speed ratio of the fan motor 10 is a linear proportional relationship as shown in FIG. 2D .

In summary, the present invention has been described in detail through the above-mentioned embodiments and variations. However, those skilled in the art should understand that all the embodiments of the present invention are only illustrative rather than restrictive, that is, without departing from the true spirit and scope of the present invention, the above-mentioned Other changes and modifications to the linear speed control circuit of the fan motor are covered by the present invention. Therefore, the protection scope of the present invention is defined by the claims of the present invention.

Claims (12)

1. A linear speed control circuit for a fan motor, comprising: a digital-to-analog conversion unit, which receives a pulse width modulation signal and converts the pulse width modulation signal into an analog signal; a square wave generating unit, which generates a square wave signal; An integrating unit, connected to the square wave generating unit, receives the square wave signal and converts it into a triangular wave signal; and A comparison unit, connected to the integration unit and the digital-to-analog conversion unit, receives and compares the analog signal and the triangular wave signal and outputs a digital signal; The rotation speed of the fan motor is directly proportional to the duty cycle of the pulse width modulation signal. 2. The linear speed control circuit for a fan motor as claimed in claim 1, wherein the digital-to-analog conversion unit comprises a transistor, a diode and a capacitor, and is connected to a DC voltage source. 3. The linear speed control circuit for fan motor as claimed in claim 1, wherein the square wave generating unit comprises a voltage control voltage source, a first resistor and a second resistor, and is connected to a first DC voltage source. 4. The linear rotational speed control circuit for a fan motor as claimed in claim 3, wherein the integrating unit comprises at least one diode, a capacitor, a voltage control voltage source and at least one resistor, and is connected to a second DC voltage source, wherein the voltage level of the triangular wave signal is determined by the resistance value of the first resistor, the resistance value of the second resistor, the voltage value of the first DC voltage source and the voltage value of the second DC voltage source. 5. The linear rotation speed control circuit for a fan motor as claimed in claim 1, wherein the comparison unit comprises a voltage control voltage source, at least one resistor and a signal output terminal, and the digital signal is output through the signal output terminal. 6. The linear rotational speed control circuit for a fan motor as claimed in claim 5, wherein the signal output terminal is also connected to gates of at least two metal-oxide-semiconductor field effect transistors, and each of the metal-oxide-semiconductor field-effect transistors The drain of the semiconductor field effect transistor is connected to a driver IC and a transistor switch of the fan motor, wherein the metal-oxide-semiconductor field effect transistor is a P-channel metal-oxide-semiconductor field-effect transistor or an N-channel metal- Oxide-semiconductor field-effect transistors. 7. A linear speed control circuit for a fan motor, comprising: a digital-to-analog conversion unit, which receives a pulse width modulation signal and converts the pulse width modulation signal into an analog signal; a triangular wave generating unit, which generates a triangular wave signal; and A comparing unit is connected with the triangular wave generating unit and the digital-to-analog converting unit, receives and compares the analog signal and the triangular wave signal and outputs a digital signal. 8. The linear speed control circuit for a fan motor as claimed in claim 7, wherein the digital signal is used to control the speed of the fan motor. 9. The linear speed control circuit for a fan motor as claimed in claim 7, wherein the fan motor speed is proportional to the duty cycle of the PWM signal. 10. The linear rotational speed control circuit for fan motor as claimed in claim 7, wherein the triangular wave generating unit comprises a voltage control voltage source, a first resistor and a second resistor, and is connected to a first DC a voltage source and a second DC voltage source, wherein the voltage level of the triangular wave signal is determined by the resistance value of the first resistor, the resistance value of the second resistor, the voltage value of the first DC voltage source and the second The voltage value of the two DC voltage sources. 11. The linear rotational speed control circuit for a fan motor as claimed in claim 7, wherein the comparison unit comprises a voltage control voltage source, at least one resistor and a signal output terminal, and the digital signal is output through the signal output terminal. 12. The linear rotational speed control circuit for a fan motor as claimed in claim 11, wherein the signal output terminal is further connected to gates of at least two metal-oxide-semiconductor field effect transistors, and each of the metal-oxide-semiconductor field-effect transistors The drain of the semiconductor field effect transistor is connected to a driver IC and a transistor switch of the fan motor, wherein the metal-oxide-semiconductor field effect transistor is a P-channel metal-oxide-semiconductor field-effect transistor or an N-channel metal-oxide Thin-semiconductor field-effect transistors.

Images