Multi-load control apparatus and slave circuit and control method thereof

A slave circuit of a multi-load control apparatus, wherein the multi-load control apparatus includes a master circuit and at least one the slave circuit, wherein the master circuit is configured to operably generate at least one pulse width modulation (PWM) signal according to an input signal, and wherein the at least one slave circuit is coupled to the master circuit, and is configured to operably generate at least one switch control signal according to a corresponding one of the at least one PWM signal, to control at least one corresponding power switch, the slave circuit comprising:

• a primary side circuit, which is configured to operably generate an AC PWM signal according to the corresponding PWM signal, wherein the primary side circuit and the master circuit are commonly coupled to a ground level;
• a secondary side circuit, which is coupled to a control terminal of the power switch, and is configured to operably generate the switch control signal according to the AC PWM signal, such that the power switch operates according to the switch control signal received by the control terminal of the power switch, wherein the control terminal is driven according to a floating ground level which is not a constant voltage level;
• and
• an isolation device, which has a primary side unit and a secondary side unit, wherein the primary side unit is electrically connected to the primary side circuit and the secondary side unit is electrically connected to the secondary side circuit, wherein and the secondary side unit is isolated from the primary side unit, and wherein the isolation device is configured to operably transfer the AC PWM signal from the primary side unit to the secondary side unit and further to the secondary side circuit;
• wherein the power switch has a current inflow terminal and a current outflow terminal, and is configured to be operably connected to a load circuit in series, and the series circuit of the power switch and the load circuit is configured to receive an AC voltage;
• wherein the PWM signal or the AC PWM signal has a modulated frequency, wherein a conductive period of the switch control signal is determined by a time period wherein the PWM signal or the AC PWM signal operates by a first frequency, and a non-conductive period of the switch control signal is determined by a time period wherein the PWM signal or the AC PWM signal operates by a second frequency;
• or
• the PWM signal or the AC PWM signal has a modulated duty ratio, wherein the conductive period of the switch control signal is determined by a time period wherein the PWM signal or the AC PWM signal operates by a first duty ratio, and the non-conductive period of the switch control signal is determined by a time period wherein the PWM signal or the AC PWM signal operates by a second duty ratio;
• wherein the PWM signal or the AC PWM signal has the modulated frequency, and the secondary side circuit includes:
• a rectifier circuit, which is coupled to the secondary side unit, and is configured to operably convert the AC PWM signal to a rectified PWM signal;
• a filter circuit, which is coupled to the rectifier circuit, and is configured to operably filter the rectified PWM signal to generate a filtered signal;
• a comparison circuit, which is coupled to the filter circuit, and is configured to operably generate a comparison signal according to the filtered signal and a reference signal;
• a logic circuit, which is coupled to the comparison circuit, and is configured to operably generate a setting signal according to the comparison signal and the rectified PWM signal;
• a latch circuit, which is coupled to the logic circuit, and is configured to operably generate a control signal according to the setting signal and the comparison signal;
• and
• a driver circuit, which is coupled to the latch circuit, and is configured to operably generate the switch control signal according to the control signal.

A control method of a multi-load control apparatus, comprising:

• generating at least one pulse width modulation (PWM) signal according to an input signal;
• generating at least one AC PWM signal according to the at least one PWM signal;
• transferring the at least one AC PWM signal from one side of an isolation device to another side of the isolation device;
• and
• generating at least one switch control signal according to the transferred at least one AC PWM signal, to control at least one corresponding power switch;
• wherein a control terminal of the power switch is driven according to a floating ground level which is not a constant voltage level;
• and
• wherein the power switch has a current inflow terminal and a current outflow terminal, and is configured to be operably connected to a load circuit in series, and the series circuit of the power switch and the load circuit is configured to receive an AC voltage;
• wherein the PWM signal or the AC PWM signal has a modulated frequency, wherein a conductive period of the switch control signal is determined by a time period wherein the PWM signal or the AC PWM signal operates by a first frequency, and a non-conductive period of the switch control signal is determined by a time period wherein the PWM signal or the AC PWM signal operates by a second frequency;
• or
• the PWM signal or the AC PWM signal has a modulated duty ratio, wherein the conductive period of the switch control signal is determined by a time period wherein the PWM signal or the AC PWM signal operates by a first duty ratio, and the non-conductive period of the switch control signal is determined by a time period wherein the PWM signal or the AC PWM signal operates by a second duty ratio;
• wherein the PWM signal or the AC PWM signal has the modulated frequency, wherein the step of generating at least one switch control signal according to the transferred at least one AC PWM signal includes:
• converting the AC PWM signal to a rectified PWM signal;
• filtering the rectified PWM signal to generate a filtered signal;
• generating a comparison signal by comparing the filtered signal with a reference signal;
• performing a logic operation of the comparison signal with the rectified PWM signal to generate a setting signal;
• generating a control signal according to the setting signal and the comparison signal;
• and
• generating the switch control signal according to the control signal.