초록 ▼

A circuit suitable for formation as a small sized IC, able to decrease the number of externally attached parts and reduce the size, and stably rotating a motor. When rotating a rotor 101 by three-phase drive signals U, V, and W generated based on a CLK signal from a VCO 7, induction voltages induced

A circuit suitable for formation as a small sized IC, able to decrease the number of externally attached parts and reduce the size, and stably rotating a motor. When rotating a rotor 101 by three-phase drive signals U, V, and W generated based on a CLK signal from a VCO 7, induction voltages induced in the three-phase coils 102 are monitored and a phase deviation of a rotor phase relative to an electric phase is detected. As a result, when the rotor phase is late relative to the electric phase, a charge pump circuit 5 is driven by an up signal f_up which becomes active for exactly a time in accordance with the phase delay amount, while when the rotor phase is advanced, the charge pump circuit 5 is driven by a down signal f_down which becomes active for exactly a time corresponding to a phase advance amount. In this motor drive circuit 1, the voltage of a VCO control terminal T_cp is directly and instantaneously and dynamically changed not in accordance with detected phase deviation information without going through a smoothing filter.

대표청구항 ▼

The invention claimed is: 1. A motor drive circuit for driving a sensorless brushless DC motor provided with a rotor and a plurality of coils for rotating the rotor, providing: a voltage controlled type variable frequency oscillation circuit operating by a frequency in accordance with a voltage app

The invention claimed is: 1. A motor drive circuit for driving a sensorless brushless DC motor provided with a rotor and a plurality of coils for rotating the rotor, providing: a voltage controlled type variable frequency oscillation circuit operating by a frequency in accordance with a voltage applied to a control terminal and generating a clock signal; a drive pulse generator for generating a plurality of drive signals having a cycle defined by the frequency of the clock signal and indicating drive circuit phases having sequentially different phase differences based on the clock signal from the variable frequency oscillation circuit; a rotor phase detector for detecting the rotor phase from phases of induction voltages induced in the plurality of coils when supplying said plurality of drive signals to said plurality of coils and rotating said rotor; and a phase comparison circuit for comparing said detected rotor phase and a drive circuit phase included in the drive signal generated by said drive pulse generator, outputting an advance phase difference signal to said voltage controlled type variable frequency oscillation circuit within a range not exceeding a defined advance maximum duration when said rotor phase is advanced from said drive circuit phase, and outputting a delay phase difference signal to said voltage controlled type variable frequency oscillation circuit within a range not exceeding a defined delay maximum duration when said rotor phase is later than said drive circuit phase, wherein said maximum duration is defined longer than the advance maximum duration. 2. A motor drive circuit as set forth in claim 1, wherein the circuit is further provided with a charge pump circuit, the charge pump circuit includes resistors and capacitors having predetermined time constants for converting currents flowing in said control terminal to voltages, applies voltages in a direction making the oscillation frequency of said voltage controlled type variable frequency oscillation circuit high to said resistors and said capacitors when there is an advance phase difference signal from said phase comparison circuit, applies voltages in a direction making the oscillation frequency of said voltage controlled type variable frequency oscillation circuit low to said resistors and said capacitors when there is a delay phase difference signal from said phase comparison circuit, and does not apply voltages to said resistors and said capacitors when there is neither a delay phase difference signal nor advance phase difference signal from said phase comparison circuit. 3. A motor drive circuit as set forth in claim 1, wherein said voltage controlled type variable frequency oscillation circuit has an oscillation frequency lower limit limit circuit determining a startup frequency at which said rotor is reliably started up from a stopped state as a lower limit frequency. 4. A motor system having a built-in sensorless brushless DC motor provided with a rotor and a plurality of coils for rotating the rotor and a motor drive circuit for driving the brushless DC motor in a modular form, wherein: said motor drive circuit provides a voltage controlled type variable frequency oscillation circuit operating by a frequency in accordance with a voltage applied to a control terminal and generating a clock signal; a drive pulse generator for generating a plurality of drive signals having a cycle defined by the frequency of the clock signal and indicating drive circuit phases having sequentially different phase differences based on the clock signal from the variable frequency oscillation circuit; a rotor phase detector for detecting the rotor phase from phases of induction voltages induced in the plurality of coils when supplying said plurality of drive signals to said plurality of coils and rotating said rotor; and a phase comparison circuit for comparing said detected rotor phase and a drive circuit phase included in the drive signal generated by said drive pulse generator, outputting an advance phase difference signal to said voltage controlled type variable frequency oscillation circuit within a range not exceeding a defined advance maximum duration when said rotor phase is advanced from said drive circuit phase, and outputting a delay phase difference signal to said voltage controlled type variable frequency oscillation circuit within a range not exceeding a defined delay maximum duration when said rotor phase is later than said drive circuit phase, wherein said maximum duration is defined longer than the advance maximum duration. 5. A motor system as set forth in claim 4, wherein: the motor drive circuit is further provided with a charge pump circuit, the charge pump circuit includes resistors and capacitors having predetermined time constants for converting currents flowing in said control terminal to voltages, applies voltages in a direction making the oscillation frequency of said voltage controlled type variable frequency oscillation circuit high to said resistors and said capacitors when there is an advance phase difference signal from said phase comparison circuit, applies voltages in a direction making the oscillation frequency of said voltage controlled type variable frequency oscillation circuit low to said resistors and said capacitors when there is a delay phase difference signal from said phase comparison circuit, and does not apply voltages to said resistors and said capacitors when there is neither a delay phase difference signal nor advance phase difference signal from said phase comparison circuit. 6. A motor system as set forth in claim 4, wherein said voltage controlled type variable frequency oscillation circuit has an oscillation frequency lower limit limit circuit determining a startup frequency at Which said rotor is reliably started up from a stopped state as a lower limit frequency. 7. A motor drive method for driving a sensorless brushless DC motor provided with a rotor and coils for driving the rotor, comprising the steps of operating an oscillator by a frequency in accordance with a voltage applied to a control terminal and generating a clock signal having a frequency in accordance with the oscillation frequency of the oscillator, generating a plurality of drive signals having a cycle defined by the frequency of said clock signal and having sequentially different phase differences based on said clock signal, generating a plurality of drive signals having a cycle defined by the frequency of said clock signal and indicating drive circuit phases having sequentially different phase differences based on said clock signal, detecting the rotor phase from phases of induction voltages induced in said plurality of coils when supplying said plurality of drive signals to said plurality of coils and rotating said rotor, comparing said detected rotor phase and the drive circuit phase included in the drive signal generated in said drive pulse generator; causing oscillation by the frequency of the voltage in accordance with the advance phase difference signal within a range not exceeding the defined advance maximum duration when said rotor phase is advanced from said drive circuit phase and generating the clock signal of the frequency in accordance with the oscillation frequency, and causing oscillation by the frequency of the voltage in accordance with the delay phase difference signal within a range not exceeding the defined delay maximum duration when said rotor phase is later than said drive circuit phase and generating the clock signal of the frequency in accordance with the oscillation frequency, wherein said delay maximum duration is defined longer than the advance maximum continuance time. 8. A motor drive method as set forth in claim 7, further comprising outputting a voltage in a direction by which said variable frequency oscillation frequency becomes high when there is an advance phase difference signal as a result of said phase comparison, and outputting a voltage in a direction by which said variable frequency oscillation frequency becomes low as a result of said phase comparison. 9. A motor drive method as set forth in claim 7, further comprising controlling a lower limit frequency determining the startup frequency for reliably starting up said rotor from the stopped state as the lower limit at the time of the generation of said clock signal. 10. A motor drive method as set forth in claim 8, further comprising outputting a first signal when the information of the phase deviation indicates that the rotor phase is delayed relative to the electric phase and outputting a second signal when the information of the phase deviation indicates that the rotor phase is advanced relative to the electric phase, making a maximum duration of the active state of the first signal shorter than a maximum duration of the active state of the second signal, and changing the voltage of the control terminal for exactly the duration of the active state of the first or second signal. 11. A motor drive method as set forth in claim 8, further comprising, at the time of the generation of the clock signal, controlling the lower limit frequency to make the startup frequency for reliably starting up the rotor from the stopped state the lower limit.