JP2007288962A - Control circuit for motor speed - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem, wherein although it is considered to change the resistance value of an externally-mounted resistor, when a target rotational speed is changed, it is also required to externally mount an analog switch in that case, in a brushless motor speed control circuit of a speed discriminator system. <P>SOLUTION: A voltage of a pulse voltage signal S4, outputted from a speed discriminator circuit 5, is switched by a select switch SL1. Consequently, it is possible to reduce the number of externally-mounted components. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a motor speed control circuit, and more particularly to a speed discriminator motor speed control circuit.

  The speed discriminating circuit compares the period of an FG (Frequency Generator) signal, which is a rotation speed signal of the motor, with the period of a reference clock, and outputs a pulse voltage signal according to the difference. The period of the reference clock is set according to the target rotation speed.

  FIG. 6 shows a timing chart of the speed discrete circuit.

  First, the FG signal is converted into a 1/2 FG signal having a 1/2 frequency. When the 1 / 2FG signal rises, a trigger pulse T1 (rising pulse) is output, and when the 1 / 2FG signal falls, a trigger pulse T2 (falling pulse) is output.

  Then, a pulse signal P1 corresponding to the pulse width of the reference clock is output by the trigger pulse T1. Further, a pulse signal P2 corresponding to the pulse width of the reference clock is output by the trigger pulse T2.

  At this time, the pulse voltage signal is output as the fast signal F (deceleration command) when the pulse signal P1 and the pulse signal P2 are “H”. Further, a pulse voltage signal is output as a slow signal S (acceleration command) when the pulse signal P1 and the pulse signal P2 are “L”.

  Then, the pulse voltage signal output from the speed discrete circuit is converted into a pulse current signal by an external resistor. Next, the pulse current signal is converted into a DC voltage signal by an integrating circuit. Thereafter, the DC voltage signal is input to a PWM (Pulse Width Modulation) driving circuit, and the PWM driving circuit performs PWM control of the on-duty of the transistor for driving the motor, and the motor is controlled to rotate at a constant speed.

As related technical literatures, for example, the following patent literatures can be cited.
JP 2001-282046 A

  In the speed discriminating circuit, when changing the target rotation speed, the cycle of the reference clock is changed.

  That is, when the target rotation speed is changed to a low speed, the period of one cycle of the FG signal becomes long, so the period of the reference clock is set to be long. Further, when the target rotation speed is changed to a high speed, the time of one cycle of the FG signal is shortened, so that the cycle of the reference clock is set short.

  Therefore, the pulse width of the pulse voltage signal differs greatly between when the target rotation speed is low and when it is high. That is, when the target rotation speed is low, the pulse width of the pulse voltage signal is long, and when the target rotation speed is high, the pulse width of the pulse voltage signal is small.

  By the way, as described above, the pulse voltage signal is converted into a pulse current signal by an external resistor. The pulse current signal is converted into a DC voltage signal by charging and discharging the integrating capacitor of the integrating circuit. At this time, when the target rotation speed is low, the pulse width of the pulse voltage signal is long, and therefore the amount of current that charges and discharges the integrating capacitor is large. Therefore, the DC voltage signal is likely to change greatly, which causes uneven rotation of the motor. Further, when the target rotation speed is high, the pulse width of the pulse voltage signal is short, so that the amount of current that charges and discharges the integrating capacitor is small. Therefore, the DC voltage signal does not immediately correspond to the pulse voltage signal, and proper speed control cannot be performed.

  Therefore, a function for switching the time constant of the integration circuit is required when changing the target rotational speed. However, a resistor and a capacitor that determine the time constant of the integrating circuit are externally attached. For this reason, in order to provide a function for switching the time constant, it is necessary to increase the number of external parts.

  In view of the above, a motor speed control circuit according to the present invention includes a speed discriminating circuit that generates a pulse voltage signal for controlling the rotation speed of the motor, a pulse voltage switching circuit that switches a voltage of the pulse voltage signal, and the pulse And an integration circuit including a resistor that converts a voltage signal into a pulse current signal and a capacitor that converts the pulse current signal into a DC voltage signal.

  Preferably, the time constant of the integration circuit is not changed when the target rotation speed of the motor is switched.

  Preferably, the pulse voltage switching circuit has a function of clamping the voltage of the pulse voltage signal.

  The motor speed control circuit according to the present invention includes a speed discriminating circuit for generating a pulse voltage signal for controlling the rotation speed of the motor, a set voltage applied to the resistor in accordance with the pulse voltage signal, and a pulse current A charge pump circuit that outputs a signal; a setting voltage switching circuit that switches the setting voltage; and an integration circuit that converts the pulse current signal into a DC voltage signal.

  Preferably, the time constant of the integration circuit is not changed when the target rotation speed of the motor is switched.

  The motor speed control circuit according to the present invention includes a pulse voltage switching circuit for switching a pulse voltage. Therefore, even if the target rotational speed is changed, the current for charging and discharging the capacitor of the integration circuit can be changed without changing the external resistance. Therefore, in the speed control circuit, it is not necessary to switch the time constant of the integration circuit, and the number of external resistors and analog switches can be reduced.

  Preferably, if the pulse voltage switching circuit is a clamp circuit for a pulse voltage signal, the above technical effect can be easily enjoyed.

  In addition, a speed control circuit including a charge pump circuit that converts a pulse voltage signal into a pulse current signal can enjoy the above technical problem by including a setting voltage switching circuit that switches a setting voltage of the charge pump circuit.

  A motor speed control circuit according to the present invention will be described below in detail with reference to the drawings.

  First, a motor speed control circuit according to a first embodiment of the present invention will be described.

  FIG. 1 is a block diagram of a motor speed control circuit according to the first embodiment.

  The motor 1 has a three-phase drive coil including a coil CU, a coil CV, and a coil CW. The motor 1 is driven by supplying current from the motor drive 2 to the coil CU, the coil CV, and the coil CW.

  First, an FG pattern S1 having a frequency proportional to the rotational speed of the motor 1 is converted into an FG signal S2 having a pulse voltage by the FG amplifier 3 and the hysteresis amplifier 4.

  Next, the FG signal S2 is inputted to the speed discriminating circuit 5. The speed discriminating circuit 5 compares the cycle of the FG signal S2 with the cycle of the reference clock S3, and outputs a pulse voltage signal S4 according to the difference from the cycle of the reference clock S3. The period of the reference clock S3 is set according to the target rotation speed.

  At this time, the pulse width of the pulse voltage signal S4 is long when the target rotational speed is low, and is small when the target rotational speed is high.

  Next, the pulse voltage signal S4 is converted into a pulse current signal S5 in accordance with an external setting resistor R1.

  Next, the pulse current signal S5 is input to the integrating circuit 6. The integration circuit 6 includes an operational amplifier 7, a capacitor C1, a capacitor C2, and a resistor R2. In the integration circuit 6, the pulse current signal S5 charges and discharges the capacitor C1 and the capacitor C2, and is converted into a DC voltage signal S6.

  Here, since the pulse width of the pulse voltage signal S4 varies greatly depending on the target rotational speed, the amount of current of the pulse current signal S5 also varies greatly depending on the target rotational speed. Accordingly, it is necessary to increase the time constant of the integration circuit 6 when the target rotation speed is high, and to decrease the time constant of the integration circuit 6 when the target rotation speed is low. In this regard, for example, when changing the target rotational speed, the current value is changed by switching the resistance value of the setting resistor R1 with an external analog switch, and the time constant of the integrating circuit is changed. Can do. However, this method increases the number of external parts, which is a factor that presses down on the cost. On the other hand, in the motor speed control circuit according to the present invention, the voltage of the pulse voltage signal S4 output from the speed discriminating circuit 5 can be changed by the select switch SL1. Therefore, in the motor speed control circuit according to the present embodiment, the response speed can be adjusted without switching the time constant of the integration circuit even if the rotation speed of the motor is changed.

  Next, the DC voltage signal S6 is input to the PWM drive circuit 8. As shown in FIG. 2, the PWM drive circuit 8 outputs a PWM signal S8 in accordance with the DC voltage signal S6 and a preset reference signal S7. still. The frequency of the PWM signal S8 is set by a capacitor C3.

  Here, the Hall element HU, the Hall element HV, and the Hall element HW generate voltage waveforms S9 that are out of phase based on the position information of the rotor of the motor 1, respectively. The voltage waveform S9 is amplified by the hall amplifier 9, and further amplified and synthesized by the matrix circuit 10. Then, the matrix circuit 10 outputs a phase switching signal S10 having a phase shift so that a force is always applied in the rotational direction necessary for the motor 1.

  Then, the pre-driver 11 outputs a signal for controlling the motor 1 to rotate at a constant speed to the motor drive 2 according to the input PWM signal S8 and the phase switching signal S10.

  As described above, in the motor speed control circuit according to the first embodiment, the current value of the pulse current signal can be switched without changing the resistance value of the external setting resistor R1.

  Next, the function of switching the voltage of the pulse voltage signal S4 output from the speed discriminating circuit 5 will be specifically described with reference to FIG.

  The output unit 12 indicates an output stage of the speed discriminating circuit 5. In the output unit 12, the transistor Q1 and the transistor Q2 are controlled based on the FG signal S2, and the pulse voltage signal S4 is output. Here, when the SL input is “H”, the pulse voltage signal S4 is output from the speed discriminating circuit 5 to the setting resistor R1 as it is. On the other hand, when the SL input is “L”, the pulse voltage signal is clamped at the voltage “H” and “L” by the clamp circuit 13 and is output from the speed discriminating circuit 5 to the setting resistor R1. Is done.

  That is, when the current rotation speed of the motor 1 is slower than the target rotation speed, the transistor Q1 is turned on and the transistor Q2 is turned off. In this case, the transistor Q3 is turned on, and the output section 12 outputs “H” of the pulse voltage signal S4. On the other hand, when the current rotation speed of the motor 1 is slower than the target rotation speed, the transistor Q1 is turned off and the transistor Q2 is turned on. In this case, the transistor Q3 is turned off, and the output section 12 outputs "L" of the pulse voltage signal S4.

  Here, when the input of the select switch SL1 is “H”, the transistors Q4 and Q5 of the clamp circuit 13 are turned on. In this case, the transistor Q6 is turned off. Further, since the transistor Q7 is turned off, the transistor Q8 is also turned off. Therefore, “H” and “L” of the pulse voltage signal S4 are output as they are without being clamped.

  On the other hand, when the input of the select switch SL1 is “L”, the transistor Q4 and the transistor Q5 are turned on. In this case, the voltage V1 divided by the resistors R3 and R4 is applied to the base of the transistor Q6. Further, since the transistor Q5 is turned off, the transistor Q7 is turned on. For this reason, the voltage V2 divided by the resistors R5 and R6 is applied to the base of the transistor Q8.

  At this time, when “H” of the pulse voltage signal S4 is output from the output unit 12, the transistor Q8 is turned on and the transistor Q6 is turned off. Therefore, “H” of the pulse voltage signal S4 is clamped to a potential obtained by adding approximately 0.7V to the base voltage V2 of the transistor Q8. Further, when “L” of the pulse voltage signal is output from the output unit 12, the transistor Q6 is turned on and the transistor Q8 is turned off. Therefore, “L” of the pulse voltage signal is clamped to a potential obtained by subtracting approximately 0.7 V from the base voltage V1 of the transistor Q6.

  Next, a motor speed control circuit according to a second embodiment of the present invention will be described.

  FIG. 4 is a block diagram of a motor speed control circuit according to the second embodiment.

  First, similarly to the motor speed control circuit according to the first embodiment, a pulse voltage signal S4 is output from the speed discriminating circuit 5. In the present embodiment, the speed switch circuit 5 is not connected to the select switch SL1 and the clamp circuit 13.

  Next, the pulse voltage signal S4 is input to the charge pump circuit 14. The charge pump circuit 14 charges and discharges the pulse current signal S11 to and from the capacitor C4 and the capacitor C5 constituting the integrating circuit 15 in accordance with the pulse voltage signal S4. The integration circuit 15 outputs a DC voltage signal S12 corresponding to the pulse current signal S11. The resistor R7 of the integrating circuit 15 is for adjusting the feedback amount.

  Here, the current value of the pulse current signal S11 is set by a voltage applied to the setting terminal 16 and a setting resistor R8 externally attached to the charge pump circuit. However, as described above, the pulse width of the pulse voltage signal S4 varies greatly depending on the target rotational speed. For this reason, when changing the target rotational speed, it is necessary to change the time constant of the integration circuit 15. In this regard, in the motor speed control circuit according to the prior art, the time constant is changed by switching the resistance value of the setting resistor R8 with, for example, an external analog switch to change the current value. On the other hand, in the motor speed control circuit according to the present invention, the voltage applied to the setting terminal 16 can be changed by the select switch SL2. Therefore, in the present invention, it is not necessary to switch the time constant of the integration circuit 15 even if the target rotational speed is changed.

  Thereafter, similarly to the motor speed control circuit according to the first embodiment, the motor 1 is controlled to rotate at a constant speed based on the DC voltage signal S12.

  As described above, the motor speed control circuit according to the second embodiment can also switch the current value of the pulse current signal S11 without changing the resistance value of the external setting resistor R8.

  Next, the function of switching the select switch SL2 to switch the voltage applied to the setting terminal 16 will be described with reference to FIG.

  As in the first embodiment, the output unit 12 indicates the output stage of the speed discriminating circuit 5 and outputs the pulse voltage signal S4. When the pulse voltage signal S4 is “H”, the sink current I2 is output from CPOUT, and when the pulse voltage signal S4 is “L”, the source current I3 is output from CPOUT. In this circuit, the current values of the sink current I2 and the source current I3 are switched by SL input.

  That is, when “H” of the pulse voltage signal S4 is output from the output unit 12, in the first comparator 17, the base potential of the transistor Q23 is determined by the resistance division of the resistor R12 and the resistor R13. Since it becomes higher than the base potential, the transistor Q9 is turned on. In this case, in the second comparator 18, the transistor Q10 is turned off. On the other hand, when “L” of the pulse voltage signal S4 is output from the output unit 12, the transistor Q9 connected to the first comparator 17 is turned off, and the transistor connected to the second comparator 18 is turned off. Q10 turns on.

  Here, when the input of the select switch SL2 is “H”, the transistor Q11 of the voltage setting circuit 18 is turned on. At this time, since the transistor Q12 is turned off, the voltage V3 set by the resistance division of the resistor R9 and the resistors R10 and R11 is applied to the base of the transistor Q13. Therefore, a voltage approximately 0.7 V lower than the base voltage V3 of the transistor Q13 is applied to the setting terminal 16. A current I1 determined by the voltage applied to the setting terminal 16 and the setting resistor R8 flows through the emitter of the transistor Q13. Further, since the transistor Q14, the transistor Q15, and the transistor Q16 form a current mirror circuit, the current I1 also flows through the collectors of the transistor Q15 and the transistor Q16.

  First, when “H” of the pulse voltage signal S4 is output, the transistor Q9 is turned on. For this reason, the current I1 does not flow to the collector of the transistor Q17. On the other hand, the transistor Q10 is turned off. Therefore, the current I1 flows through the collector-emitter path of the transistor Q18. Since the transistor Q18 and the transistor Q19 constitute a current mirror circuit, the current I1 also flows through the collector of the transistor Q19. Accordingly, when “H” of the pulse voltage signal S4 is output, the charge pump circuit 14 outputs a sink current I2 based on the current I1.

  On the other hand, when “L” of the pulse voltage signal S4 is output, the transistor Q9 is turned off. Therefore, the current I1 flows through the collector of the transistor Q17. The transistor Q17 and the transistor Q20 constitute a current mirror circuit. For this reason, the current I1 also flows through the collector of the transistor Q20. The transistor Q21 and the transistor Q22 constitute a current mirror circuit. For this reason, the current I1 also flows through the collector of the transistor Q22. On the other hand, the transistor Q10 is turned on. Therefore, the current I1 does not flow through the collector of the transistor Q18. Therefore, when “L” of the pulse voltage signal S4 is output, the source current I3 based on the current I1 is output from the charge pump circuit 5.

  When the input of the select switch SL2 is “L”, the transistor Q11 of the voltage setting circuit 18 is turned off. At this time, since the transistor Q12 is turned on, a voltage V4 set by resistance division of the resistor R9 and the resistor R10 is applied to the base of the transistor Q13. Therefore, a voltage approximately 0.7V lower than the base voltage V4 of the transistor Q13 is applied to the setting terminal 16. At this time, the voltage applied to the setting terminal 16 is smaller than that when the input of the select switch SL2 is “H”. That is, the current I1 flowing through the emitter of the transistor Q13 is reduced. Therefore, the current values of the sink current I2 and the source current I3 are reduced.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiment but by the scope of claims for patent, and all modifications within the meaning and scope equivalent to the scope of claims for patent are included.

  For example, in the motor speed control circuit according to the present invention, only one setting resistor is arranged. However, as in the prior art, several setting resistors may be connected and an analog switch may be arranged. In this case, when combined with the effects of the invention according to the present invention, a speed control circuit corresponding to more rotational speeds is configured.

The block diagram of the speed control circuit which concerns on one Embodiment of this invention is shown. The input / output signal of a PWM drive circuit is shown. The circuit diagram of the clamp circuit concerning one embodiment of the present invention is shown. The block diagram of the speed control circuit which concerns on other embodiment of this invention is shown. The circuit diagram of the voltage setting circuit which concerns on other embodiment of this invention is shown. Indicates the input / output signals of the speed control circuit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Motor 2 Motor drive 3 FG amplifier 4 Hysteresis amplifier 5 Speed discriminator circuit 6 Integration circuit 7 Operational amplifier 8 PWM drive circuit 9 Hall amplifier 10 Matrix circuit 11 Pre-driver 12 Output part 13 Clamp circuit 14 Charge pump circuit 16 Setting terminal 15 Integration Circuit 17 First comparator 18 Second comparator 19 Voltage setting circuit R1 Setting resistor R8 Setting resistor

Claims (5)

A speed discrete circuit for generating a pulse voltage signal for controlling the rotational speed of the motor;
A pulse voltage switching circuit for switching a voltage level of the pulse voltage signal;
A motor speed control circuit comprising: an integration circuit including a resistor that converts the pulse voltage signal into a pulse current signal; and a capacitor that converts the pulse current signal into a DC voltage signal.   2. The motor speed control circuit according to claim 1, wherein a time constant of the integration circuit is not changed when the target rotation speed of the motor is switched. 3.   2. The motor speed control circuit according to claim 1, wherein the pulse voltage switching circuit has a function of clamping a voltage of the pulse voltage signal. A speed discrete circuit for generating a pulse voltage signal for controlling the rotational speed of the motor;
In accordance with the pulse voltage signal, a set voltage is applied to the resistor, and a charge pump circuit that outputs a pulse current signal;
A set voltage switching circuit for switching the set voltage;
An integration circuit for converting the pulse current signal into a DC voltage signal; 5. The motor speed control circuit according to claim 4, wherein the time constant of the integration circuit is not changed when the target rotation speed of the motor is switched.