Startup control circuit of drive circuit
View Patent ↗Startup of motor is reliably executed and sonic noise is reduced. A control circuit controls a selector to apply control to output a full-drive waveform at startup and then output a PWM modulation waveform. The full-drive waveform which is an alternating waveform in which positive and negative are inverted at 180° is output. Then, the PWM drive waveform is selected.
1. A startup control circuit of a drive circuit which controls driving of a motor at startup, the startup control circuit comprising:
a full-drive waveform outputting circuit which outputs a full-drive waveform which is an alternating waveform in which positive and negative are inverted at 180°;
a limited drive waveform outputting circuit which outputs a limited drive waveform in which a predetermined drive stop period is provided at a time when the positive and the negative are inverted;
a PWM circuit which obtains a PWM drive waveform by applying pulse-width modulation to the limited drive waveform;
a selector which selects one of the full-drive waveform and the PWM drive waveform; and
a control circuit which controls the selector to apply control to output the full-drive waveform at startup and then output the PWM drive waveform.
2. The startup control circuit of the drive circuit according to claim 1 , wherein
switching of the drive waveform in the control circuit is executed according to a count value of a number of alternations in a rotational state signal detecting rotation of the motor.
3. The startup control circuit of claim 1 , further comprising a 150°-electricity application generating circuit which modifies the PWM drive waveform after an initial period of time.
4. The startup circuit of claim 1 , wherein the control circuit applies control to output the full-drive waveform at startup, then output the PWM drive waveform, and then output the limited drive wave to which the pulse-width modulation is applied.
5. The startup circuit of claim 1 , further comprising a comparator circuit that provides an output signal to the full-drive waveform outputting circuit and the limited drive waveform outputting circuit, wherein the output of the comparator is produced by comparing the output of an offset controlling circuit with a reference voltage, wherein the offset controlling circuit receives an output from a Hall device that senses a rotational position of the motor and wherein the offset controlling circuit adds an offset to the output of the Hall device.
6. The startup control circuit of claim 5 , wherein switching of the drive waveform in the control circuit is executed according to a count value of a number of alternations in a rotational state signal detecting rotation of the motor.
7. The startup control circuit of claim 1 , further comprising an output circuit that outputs the selected one of the full-drive waveform and the PWM drive waveform to an output circuit that alternates current direction through a coil in accordance with the selected waveform.
8. A startup control circuit of a drive circuit which controls driving of a motor at startup, the startup control circuit comprising:
a full-drive waveform outputting circuit which outputs a full-drive waveform which is an alternating waveform in which positive and negative are inverted at 180°;
a limited drive waveform outputting circuit which outputs a limited drive waveform in which a predetermined drive stop period is provided at a time when the positive and the negative are inverted;
a selector which receives the full-drive waveform and the limited drive waveform and which selects and outputs one of the full-drive waveform and the limited drive waveform;
a PWM circuit which applies pulse-width modulation to the limited drive waveform; and
a control circuit which controls the selector and the PWM circuit to apply a control to output the full-drive waveform at startup and then output a limited drive wave obtained by applying the pulse-width modulation to the limited drive waveform.
9. The startup control circuit of the drive circuit according to claim 8 , wherein
the control circuit applies control to output the full-drive waveform at startup, then output the limited drive waveform, and then output the limited drive wave to which the pulse-width modulation is applied.
10. The startup control circuit of the drive circuit according to claim 9 , wherein
switching of the drive waveform in the control circuit is executed according to a count value of a number of alternations in a rotational state signal detecting rotation of the motor.
11. The startup control circuit of the drive circuit according to claim 8 , wherein
switching of the drive waveform in the control circuit is executed according to a count value of a number of alternations in a rotational state signal detecting rotation of the motor.
12. The startup control circuit of claim 8 , further comprising a 150°-electricity application generating circuit which modifies the limited drive waveform after an initial period of time.
13. The startup control circuit of claim 12 , further comprising an output circuit that outputs the selected one of the full-drive waveform and the PWM drive waveform to an output circuit that alternates current direction through a coil in accordance with the selected waveform.
14. A motor control circuit, comprising:
a full-drive waveform outputting circuit which outputs a full-drive waveform which is an alternating waveform in which positive and negative are inverted at 180°;
a limited drive waveform outputting circuit which outputs a limited drive waveform in which a predetermined drive stop period is provided at a time when the positive and the negative are inverted;
a selector which receives the full-drive waveform and the limited drive waveform and which selects and outputs one of the full-drive waveform and the limited drive waveform;
a PWM circuit which applies pulse-width modulation to the limited drive waveform; and
a control circuit which controls the selector and the PWM circuit to apply a control to output the full-drive waveform at startup and then output a limited drive wave obtained by applying the pulse-width modulation to the limited drive waveform, wherein switching of the drive waveform in the control circuit is executed according to a count value of a number of alternations in a rotational state signal detecting rotation of the motor.
15. The motor control circuit of claim 14 , wherein the control circuit applies control to output the full-drive waveform at startup, then output the limited drive waveform, and then output the limited drive wave to which the pulse-width modulation is applied.
16. The motor control circuit of claim 14 , wherein switching of the drive waveform in the control circuit is executed according to a count value of a number of alternations in a rotational state signal detecting rotation of the motor.
17. The motor control circuit of claim 14 , further comprising an output circuit that outputs the selected one of the full-drive waveform and the PWM drive waveform to an output circuit that alternates current direction through a coil in accordance with the selected waveform.
18. The motor control circuit of claim 17 , wherein the output circuit is a second selector.
19. The motor control circuit of claim 14 , wherein the limited drive waveform inverts at 150°.
20. The motor control circuit of claim 14 , further comprising a comparator circuit that provides an output signal to the full-drive waveform outputting circuit and the limited drive waveform outputting circuit, wherein the output of the comparator is produced by comparing the output of an offset controlling circuit with a reference voltage, wherein the offset controlling circuit receives an output from a Hall device that senses a rotational position of the motor and wherein the offset controlling circuit adds an offset to the output of the Hall device.