CN1305214C - Speed Control Circuit of Brushless DC Motor - Google Patents

Abstract

A speed control circuit for a brushless DC motor comprises a fan motor drive circuit, an overcurrent detection and current limiting circuit and a speed control circuit. The fan motor drive circuit is connected to the overcurrent detection and current limiting circuit, and the overcurrent detection and current limiting circuit is connected to the speed control circuit. The overcurrent detection and current limiting circuit is used to detect the speed and detect overcurrent. When the speed is abnormal and overcurrent is generated, the overcurrent detection and current limiting circuit can control the fan motor drive circuit to maintain a low current level. The speed control circuit is used to control the overcurrent detection and current limiting circuit. The speed signal of the speed control circuit can control the overcurrent detection and current limiting circuit to complete the speed control of the brushless DC motor.

Description

Speed Control Circuit of Brushless DC Motor

technical field

The present invention relates to a rotational speed control circuit, in particular to such a rotational speed control circuit of a brushless DC motor, which incorporates a rotational speed control circuit into the brushless DC motor, and the rotational speed control circuit is connected to a current limiting circuit, In order to be suitable for the speed control of the brushless DC motor.

Background technique

Please refer to Fig. 1, Taiwan Patent Gazette Announcement No. 540902 "Brushless DC Fan Motor Two-stage Current Limiting Circuit" announced on May 23, 2003, which discloses a fan motor drive circuit 10 and two-stage Current limiting circuit 20.

The fan motor driving circuit 10 includes a Hall voltage amplifying circuit 11 , a phase inversion circuit 12 and a motor coil winding driving circuit 13 . The Hall voltage amplifying circuit 11 is used to amplify the weak Hall voltage, and then output to the phase inversion circuit 12 . The phase inversion circuit 12 inverts the phase of the input amplified voltage by 180 degrees, and then outputs it to the motor coil winding drive circuit 13, so as to alternately excite the motor coil windings to drive the rotor to rotate.

The two-stage current limiting circuit 20 includes an overcurrent detection circuit 21 , a running detection circuit 22 and a current limiting circuit 23 . The overcurrent detecting circuit 21 can output a voltage level for judging whether the fan motor has overcurrent. The operation detection circuit 22 captures the voltage of the Hall voltage amplifying circuit 11, and uses a rectification and integration circuit to output a voltage level (high or low level) to determine whether the fan motor is operating abnormally. The current limiting circuit 23 utilizes the voltage levels of the overcurrent detection circuit 21 and the operation detection circuit 22 to determine whether the current limiting function is activated. In this way, the phase inversion circuit 12 of the motor driving circuit 10 is controlled to prevent the current of the motor coil winding from being limited to a low level which is not enough to damage the motor driving circuit. The current limiting circuit 23 has a comparator to calculate the voltage levels of the overcurrent detection circuit 21 and the operation detection circuit 22, and then determine whether the current limiting function is activated.

Please refer to FIG. 2, which is a block diagram of a PWM control circuit of a known fan motor. The fan motor 1 is connected to a PWM control circuit 30 and a temperature sensing element 31, so that the PWM speed can be performed according to the temperature of the temperature sensing element 31. control. Since the PWM control circuit 30 is connected to the drive circuit 10 inside the fan motor 1 from an external system (not shown), the drive circuit 10 is subject to the duty cycle generated by the PWM control circuit 30 of the external system. control.

FIG. 3 discloses a known graph of using the PWM control circuit 30 to control and adjust the rotational speed and temperature of the fan motor 1 . The fan motor 1 has multi-stage speed control. It has rotational speeds S0 , S1 , S2 at least at temperatures T0 , T1 , T2 .

Please refer to FIGS. 2 and 3 again, when the detected temperature of the temperature sensing element 31 reaches T1, the fan speed is adjusted to S1. When the detected temperature of the temperature sensing element 31 reaches S2, the fan speed is adjusted to S2. However, since the frequency ratio generated by the PWM control circuit 30 of the external system is not consistent with the required frequency ratio of the driving circuit 10 , the fan speed cannot be precisely controlled. That is, when the detected temperature of the temperature sensing element 31 does not reach T1 or T2, the fan speed will be switched to S1 or S2 in advance (please refer to FIG. 3 ).

Or when the detected temperature of the temperature sensing element 31 exceeds T1 and T2, the fan speed still cannot be switched to S1 or S2.

In short, the PWM speed control signal introduced from an external system is not suitable for brushless DC motors with speed control.

In view of this, the present inventor has developed the rotational speed control circuit of the brushless DC motor of the present invention in order to improve the defects of the above-mentioned known technologies.

Contents of the invention

The main technical problem to be solved by the present invention is to provide a speed control circuit for a brushless DC motor, which connects a fan motor drive circuit to an overcurrent detection current limiting circuit, and the overcurrent detection current limiting circuit is connected to a The rotational speed control circuit controls the overcurrent detection current limiting circuit by means of the rotational speed signal of the rotational speed control circuit, so that the present invention has the function of rotational speed control.

Another technical problem to be solved by the present invention is to provide a rotational speed control circuit of a brushless DC motor, connect a fan motor drive circuit to an overcurrent detection current limiting circuit and a rotational speed control circuit, and the rotational speed control circuit Incorporated into the brushless DC motor to simplify the overall structure of the rotational speed control circuit of the brushless DC motor, so that the present invention has the effect of simplifying the structure.

The technical solution of the present invention is: a speed control circuit of a brushless DC motor, comprising:

A fan motor drive circuit connected to a power supply:

An overcurrent detection current limiting circuit, which is connected to the fan motor drive circuit, the overcurrent detection current limiting circuit is used to detect the speed of the fan motor and detect whether it is overcurrent. When the speed is abnormal and an overcurrent is generated, The overcurrent detection current limiting circuit can control the fan motor drive circuit to maintain a low current level: and

A speed control circuit, which is connected to the over-current detection current-limiting circuit, the speed control circuit generates a PWM signal to output a speed signal to the over-current detection current-limiting circuit, and the over-current detection current-limiting circuit controls the brushless The speed of the DC motor.

In the speed control circuit of a brushless DC motor as described above, the overcurrent detection current limiting circuit includes an overcurrent detection circuit, a running detection circuit and a current limiting circuit, and the current limiting circuit is connected to the overcurrent detection circuit. Known circuit and operation detection circuit.

The rotational speed control circuit of the brushless DC motor described above, the rotational speed control circuit includes a PWM control circuit and a temperature sensing element, the PWM control circuit is connected to the temperature sensing element, so that the temperature of the temperature sensing element The detection signal is input to the PWM control circuit.

In the speed control circuit of the brushless DC motor described above, the PWM control circuit is composed of a PWM generator and a control circuit, the PWM generator is connected to the control circuit, and the PWM generator is further connected to the overcurrent detection Know the current limiting circuit.

The speed control circuit of the brushless DC motor as described above, the control circuit is connected to the temperature sensing element, the overcurrent detection current limiting circuit includes an operation detection circuit, and the control circuit is further connected to the operation detection circuit .

In the rotational speed control circuit of the brushless DC motor mentioned above, the temperature sensing element is a thermistor.

In the rotational speed control circuit of the brushless DC motor described above, the rotational speed control circuit is connected to the operation detection circuit and the current limiting circuit in the overcurrent detection current limiting circuit.

In the speed control circuit of the brushless DC motor described above, the fan motor drive circuit includes a Hall voltage amplifier circuit, a phase inversion circuit and a motor coil winding drive circuit, and the phase inversion circuit is connected to the Hall voltage Amplifying circuit and motor coil winding drive circuit.

The characteristics and advantages of the present invention are: the rotational speed control circuit of the brushless DC motor proposed by the present invention is to connect a fan motor drive circuit to an overcurrent detection current limiting circuit, and then connect a rotational speed control circuit to the overcurrent detection circuit. A current-limiting circuit is used to control the over-current detection current-limiting circuit by means of the speed signal of the speed control circuit, so as to complete the multi-stage speed control of the fan motor drive circuit. Since the rotational speed control circuit has a PWM generator, it can provide a frequency width ratio corresponding to the PWM signal of the brushless DC motor, so that the current limiting switch of the current limiting circuit can be precisely controlled, and the phase reversal of the fan motor driving circuit can be precisely controlled. Rotation circuit; the rotational speed control circuit is incorporated into the brushless DC motor to simplify the overall structure of the rotational speed control circuit of the brushless DC motor. Thereby overcoming the defect that the rotation speed of the known brushless DC motor cannot be accurately switched according to the detected temperature, that is, the known brushless DC motor has the defect of switching the rotation speed too early or delaying the switching speed, and the rotation speed of the brushless DC motor of the present invention can be determined according to The detected temperature switches the rotation speed accurately, is suitable for the rotation speed control of the brushless DC motor, and has the effect of simplifying the structure.

Description of drawings

FIG. 1 is a block diagram of a two-stage current limiting circuit of a brushless DC fan motor announced in Taiwan Patent Gazette No. 540902;

FIG. 2 is a block diagram of a conventional PWM control circuit for a fan motor:

FIG. 3 is a graph showing the rotational speed and temperature of a known fan motor;

Fig. 4 is the block diagram of the rotational speed control circuit of the brushless DC motor of the specific embodiment of the present invention:

5 is a schematic diagram of a rotational speed control circuit of a brushless DC motor according to a specific embodiment of the present invention;

FIG. 6 is a graph showing the rotational speed and temperature of the brushless DC motor according to a specific embodiment of the present invention.

Symbol Description:

1. Fan motor 10. Fan motor drive circuit 11. Hall voltage amplifier circuit

111. Hall sensor element 12. Phase inversion circuit 13. Motor coil winding drive circuit

131. Motor coil 20. Overcurrent detection current limiting circuit 21. Overcurrent detection circuit

22. Operation detection circuit 30. PWM control circuit 41. PWM control circuit

42. Temperature sensing element 23. Current limiting circuit 31. Temperature sensing element

411. PWM generator 231. Current limiting switch 40. Speed control circuit

412. Control circuit

Detailed ways

In order to make the above and other objects, features, and advantages of the present invention more clearly understood, specific embodiments of the present invention will be exemplified below, together with the accompanying drawings, for a detailed description as follows.

Fig. 4 discloses the flow block diagram of the rotational speed control circuit of the brushless DC motor of the specific embodiment of the present invention; Fig. 5 discloses the circuit diagram of the rotational speed control circuit of the brushless DC motor of the specific embodiment of the present invention; Fig. 6 discloses the brushless DC motor of the specific embodiment of the present invention A graph of speed versus temperature for a DC motor.

Please refer to FIG. 4 , the structurally identical parts of the specific embodiment of the present invention are marked with the same figure number group, so as to easily understand the differences between the specific embodiment of the present invention and the known. Part of the technical content of the specific embodiments of the present invention has been disclosed in the public description, which is hereby incorporated by reference and will not be described in detail.

Please refer to FIG. 4 , the rotational speed control circuit of the brushless DC motor according to the specific embodiment of the present invention includes a fan motor drive circuit 10 , an overcurrent detection current limiting circuit 20 and a rotational speed control circuit 40 . The fan motor driving circuit 10 is connected to the overcurrent detection current limiting circuit 20 , and the overcurrent detection current limiting circuit 20 is connected to the rotation speed control circuit 40 . The overcurrent detection current limiting circuit 20 is connected in series between the fan motor drive circuit 10 and the speed control circuit 40 .

Referring to FIG. 4 again, the fan motor drive circuit 10 is connected to a power supply (VCC) for driving a rotor to rotate. The overcurrent detection current limiting circuit 20 is used to detect the rotation speed of the rotor and detect whether there is an overcurrent. When the rotation speed is abnormal and an overcurrent is generated at the same time, the overcurrent detection current limiting circuit 20 controls the fan motor drive circuit. 10 is maintained at a low current level. The rotational speed control circuit 40 is used to control the overcurrent detection current limiting circuit 20 , the rotational speed control circuit 40 controls the overcurrent detection current limiting circuit 20 with a rotational speed signal, so as to complete the rotational speed control of the fan motor drive circuit 10 .

4 and 5, the fan motor drive circuit 10 includes a Hall voltage amplifying circuit 11, a phase inversion circuit 12 and a motor coil winding drive circuit 13, the phase inversion circuit 12 is connected to the Hall voltage The amplifier circuit 11 and the motor coil winding drive circuit 13 . The Hall voltage amplifying circuit 11 is connected to a Hall sensing element 111 so as to amplify the Hall signal of the Hall sensing element 111 and output it to the phase inversion circuit 12 . The phase inversion circuit 12 inverts the phase of the input amplified voltage by 180 degrees, and then outputs it to the motor coil winding driving circuit 13 . The motor coil winding drive circuit 13 is connected to a motor coil 131 . The motor coil 131 is alternately excited by the output of the phase inversion circuit 12 to drive the rotor to rotate.

Referring to FIGS. 4 and 5 again, the overcurrent detection and current limiting circuit 20 includes an overcurrent detection circuit 21 , an operation detection circuit 22 and a current limiting circuit 23 .

Referring to FIGS. 4 and 5 again, the overcurrent detection circuit 21 is connected in series between the motor coil winding driving circuit 13 and the current limiting circuit 23 . Referring to FIG. 5 again, the overcurrent detection circuit 21 is preferably a resistor, which outputs a voltage level for the current limiting circuit 23 to determine whether the motor coil winding drive circuit 13 has overcurrent.

Please refer to FIGS. 4 and 5 again, the operation detecting circuit 22 is connected in series between the Hall voltage amplifying circuit 11 and the current limiting circuit 23 . The operation detection circuit 22 captures the voltage of the Hall voltage amplifying circuit 11, and uses a rectification and integration circuit to output a voltage level (high or low level) for the current limiting circuit 23 to determine whether the fan motor is operating abnormally. .

Please refer to Figures 4 and 5 again, the current limiting circuit 23 includes a current limiting switch 231, which is connected to the phase inversion circuit 12, and the current limiting circuit 23 is connected to the overcurrent detection circuit 21 and the operation detection circuit. twenty two. The current limiting circuit uses the voltage levels of the overcurrent detection circuit 21 and the operation detection circuit 22 to determine whether the current limiting function is activated, thereby controlling the phase inversion circuit 12 of the motor drive circuit 10 to suppress the current of the motor coil winding 131 It is limited to a low level which is not enough to damage the fan motor driving circuit 10 . The current limiting circuit 23 has a comparator for computing the voltage levels of the overcurrent detection circuit 21 and the operation detection circuit 22, and the output of the comparator is output to the phase inversion circuit 12 through the current limiting switch 231, so that Perform current limiting control.

Please refer to FIG. 4 again, the speed control circuit 40 is connected to the fan motor drive circuit 10 via the overcurrent detection circuit 20, the speed control circuit 40 can be incorporated into the brushless DC motor,

Make the brushless DC motor itself have PWM control. And the speed control circuit 40 includes a PWM control circuit 41 and a temperature sensing element 42 . The PWM control circuit 41 is composed of a PWM generator 411 and a control circuit 412 . The rotational speed control circuit 40 is connected to the operation detection circuit 22 and the current limiting circuit 23 to obtain a rotational speed detection signal. The control circuit 412 is further connected to the temperature sensing element 42 to obtain a temperature detection signal. The PWM generator 411 is connected between the current limiting circuit 23 and the control circuit 412 , and the PWM generator 411 is used to generate a PWM signal and input it to the current limiting circuit 23 to control the fan motor driving circuit 10 . The control circuit 412 is connected to the operation detecting circuit 22 and the temperature sensing element 42 .

Please refer to FIG. 5 again, the PWM generator 411 and the control circuit 412 of the PWM control circuit 41 can be made into a single chip.

Referring to FIG. 5 again, the temperature sensing element 42 is a thermistor for detecting temperature so as to input the temperature detection signal into the control circuit 412 of the PWM control circuit 41 .

Please refer to FIG. 4 again, since the rotational speed control circuit 40 has the PWM generator 411, it can provide a frequency width ratio of the PWM signal conforming to the brushless DC motor, so that the current limiting of the current limiting circuit 23 can be precisely controlled. The switch 231 is as shown in FIG. 5 . Therefore, the rotational speed control circuit 40 can accurately control the phase inversion circuit 12 of the fan motor driving circuit 10 via the current limiting switch 231 .

Please refer to FIG. 6, under the control of the rotational speed control circuit 40, when the temperature sensing element 42 detects the temperature as T0, T1, T2, T3, the rotational speed control circuit 40 can precisely control the rotational speed of the brushless DC motor. It is S0, S1, S2, S3. For example, when the temperature rises to T1, the rotational speed of the brushless DC motor switches from S0 to S1 immediately. Similarly, when the temperature drops to T0, the switchback of the brushless DC motor immediately switches from S1 to S0.

Please refer to FIG. 1 to FIG. 6 again, the rotation speed of the conventional brushless DC motor cannot be accurately switched according to the detected temperature, that is, the known brushless DC motor has the defect of switching the rotation speed too early or delaying the switching speed. In contrast, the rotational speed of the brushless DC motor of the present invention can precisely switch the rotational speed according to the detected temperature, so that the rotational speed control circuit 40 of the present invention is suitable for the rotational speed control of the brushless DC motor.

Although the present invention has been disclosed with specific embodiments, it is not intended to limit the present invention. Any person skilled in the art can make replacements of equivalent components without departing from the concept and scope of the present invention, or replace them according to the present invention. The equivalent changes and modifications made in the scope of patent protection shall still fall within the scope of this patent.

Claims (8)

1. A speed control circuit for a brushless DC motor, characterized in that: the speed control circuit includes: A fan motor drive circuit connected to a power supply; An overcurrent detection current limiting circuit, which is connected to the fan motor drive circuit, the overcurrent detection current limiting circuit is used to detect the speed of the fan motor and detect whether it is overcurrent. When the speed is abnormal and an overcurrent is generated, The overcurrent detection current limiting circuit controls the fan motor drive circuit to maintain a low current level; and A speed control circuit, which is connected to the over-current detection current-limiting circuit, the speed control circuit generates a PWM signal to output a speed signal to the over-current detection current-limiting circuit, and the over-current detection current-limiting circuit controls the brushless The speed of the DC motor. 2. The rotational speed control circuit of a brushless DC motor according to claim 1, wherein the overcurrent detection and current limiting circuit comprises an overcurrent detection circuit, an operation detection circuit and a current limiting circuit, The current limiting circuit is connected with the overcurrent detection circuit and the operation detection circuit. 3. The rotational speed control circuit of a brushless DC motor according to claim 1, wherein the rotational speed control circuit comprises a PWM control circuit and a temperature sensing element, and the PWM control circuit is connected to the temperature sensing element , so that the temperature detection signal of the temperature sensing element is input to the PWM control circuit. 4. The rotational speed control circuit of a brushless DC motor according to claim 3, wherein the PWM control circuit is composed of a PWM generator and a control circuit, the PWM generator is connected to the control circuit, and the PWM The generator is further connected to the overcurrent detection current limiting circuit. 5. The rotational speed control circuit of a brushless DC motor according to claim 4, wherein the control circuit is connected to the temperature sensing element, the overcurrent detection current limiting circuit includes a running detection circuit, the The control circuit is also connected to the operation detection circuit. 6. The rotational speed control circuit of a brushless DC motor as claimed in claim 3, wherein the temperature sensing element is a thermistor. 7. The rotational speed control circuit of a brushless DC motor according to claim 2, wherein the rotational speed control circuit is connected to the operation detection circuit and the current limiting circuit in the overcurrent detection current limiting circuit. 8. The rotational speed control circuit of a brushless DC motor according to claim 1, wherein the fan motor driving circuit comprises a Hall voltage amplifying circuit, a phase inversion circuit and a motor coil winding driving circuit, the The phase inversion circuit connects the Hall voltage amplifying circuit and the motor coil winding drive circuit.

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