Closed-loop control device of a mechanical sewing machine and method for controlling the same

A closed-loop control device of a mechanical sewing machine, comprising:

• an isolated switch-mode power supply module having:
• an input terminal adapted to connect to an AC (Alternating Current) power source;
• and
• an output terminal outputting an output voltage;
• a DC (Direct Current) motor connected to the output terminal of the isolated switch-mode power supply module to receive the output voltage;
• a speed control module outputting a speed signal;
• a processor connected to the speed control module and outputting a control signal according to the speed signal;
• an electronic switch connected between the DC motor and the processor, controlling a turn-on time of the electronic switch according to the control signal, and adjusting an average operating voltage of the DC motor;
• a current detection module connected between the electronic switch and the processor, detecting an operating current of the DC motor, and generating an operating current signal;
• and
• a voltage detection module connected between the DC motor and the processor, detecting an operating voltage of the DC motor, and generating an operating voltage signal;
• wherein the processor further adjusts the control signal according to the operating current signal and the operating voltage signal;
• and
• wherein the isolated switch-mode power supply module has:
• a rectification unit connected to the input terminal of the isolated switch-mode power supply module and rectifying an AC power from the AC power source to a DC voltage;
• a transformer having:
• a primary side connected to the rectification unit and receiving the DC voltage outputted from the rectification unit;
• and
• a secondary side;
• a voltage regulation unit connected to the primary side of the transformer, and having:
• an electronic power switch;
• a PWM (Pulse Width Modulation) IC (Integrated Circuit) controlling a turn-on time of the electronic power switch and adjusting a duty cycle of the DC voltage from the primary side of the transformer;
• and
• a rectifier and filter circuit connected between the secondary side of the transformer and the output terminal of the isolated switch-mode power supply module.