Title:
METHOD AND APPARATUS FOR GIVING OF LOCK OF PHASE-LOCKED LOOP SYSTEM FROM FREQUENCY SWEEP
Document Type and Number:
Japanese Patent JPH0686584
Kind Code:
A
Abstract:
PURPOSE: To synchronize a voltage-controlled oscillator VCO with open-loop frequency when frequency is kept within a pull-in range, and to give smooth transition from an open-loop step-up of system frequency to closed-loop PLL operation. CONSTITUTION: An external clocking signal is used until the clocking signal reaches a preset VCO frequency and synchronism with respect to the external clocking signal of an output from a VCO 52 is obtained, and clocked to an internal signal designed which the VCO should follow. Consequently, a smooth transition between an open-loop lamp-up of a polyphase DC motor 19 and a closed-loop operation of loop operation, into which the motor is incorporated, is enabled. Since the circuit phase-synchronizes an output from a PLL loop 40 for phase switching following up the back electromotive force of the motor 19 with an external clocking used for motor ramp-up, no 'oscillation' is generated in the motor in the transition from the open-loop operation of the motor to the closed-loop operation.
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Inventors:
FURANSESUKO KAROBORANTE
Application Number:
JP3882393A
Publication Date:
March 25, 1994
Filing Date:
February 26, 1993
Export Citation:
Assignee:
SGS THOMSON MICROELECTRONICS
International Classes:
H02P6/16; H02P6/20; H03L7/10; (IPC1-7): H02P6/02
Attorney, Agent or Firm:
Kazuo Kobashi (1 person outside)
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