Constant-voltage and constant-current buck converter and control circuit

A buck converter switch mode power supply (SMPS), comprising:

• input terminals for coupling to an input line voltage;
• output terminals for coupling to a load device, wherein at least one of the output terminals is coupled to either a ground terminal or a power terminal of the input line voltage;
• an inductor coupled to one of the output terminals;
• a rectifying device coupled to the inductor;
• a capacitor coupled to the output terminals;
• and
• a control circuit including:
• a power switch configured for coupling to a line voltage and configured for charging the inductor;
• an input line voltage sampling circuit configured to provide a sampled input line voltage;
• and
• a constant-voltage (CV) and constant-current (CC) control module coupled to the power switch, wherein the CV and CC control module is configured to:
• during a charging period of the inductor, control the power switch to provide a constant output current by maintaining a constant peak inductor current by:
• receiving the sampled input line voltage from the input line voltage sampling circuit;
• and
• modifying a threshold voltage based on the sampled input line voltage;
• and
• during a discharging period of the inductor, to monitor the sensed output voltage to control the power switch to provide a constant output voltage.