Introduction

A DC-to-DC converter is typically implemented as a constant voltage (CV) regulator. The control loop will adjust the duty cycle in order to maintain a constant output voltage regardless of changes to the input voltage and load current.

A constant current (CC) converter regulates current the same way: the control loop adjusts the duty cycle to maintain a constant output current regardless of changes to the input voltage and output resistance. A change in output resistance will cause the output voltage to adjust as the load resistance varies; the higher the output resistance, the greater the output voltage.

A CC/CV converter will regulate both current and voltage depending on the output resistance level.

see more on this here https://e2e.ti.com/blogs_/b/powerhouse/archive/2017/11/24/how-to-design-a-simple-constant-current-constant-voltage-buck-converter?jktype=e2e_blog