Constant-current circuit capable of voltage compensation and zero-voltage switching

A constant-current circuit capable of voltage compensation and zero-voltage switching, the constant-current circuit being a single-switch isolated flyback converter and comprising:

• a transformer having a primary side for receiving an input voltage and a secondary side for providing an output voltage;
• a primary-side power switch connected to the primary side;
• a sensing resistor connected to the primary-side power switch so as to sense information related to a primary-side current;
• a voltage divider having a first end for receiving the input voltage and a second end connected to a line between the sensing resistor and the primary-side power switch so as to generate a compensation signal;
• a comparator having a first input end connected to the voltage divider and a second input end connected to a reference voltage;
• and
• a control circuit having a first input end connected to an output end of the comparator so as to control the primary-side power switch according to the information related to the primary-side current and the compensation signal obtained through the comparator, and adjust a peak voltage resulting from the sensing resistor to a reference voltage through adding the compensation signal thereto, thus enabling the secondary side to generate a constant output current.