Switching converter equipped with adaptive frequency control function
A switching converter equipped with an adaptive frequency control function includes a switching unit, an inductor, an output capacitor, a zero crossing detector that receives a signal of the switching node and a signal of the output terminal, that are fed back, and detects whether or not an inductor current flowing through the inductor crosses a zero point, a DCM/CCM detector that outputs an operation section discrimination signal that discriminates a current operation section by dividing the current operation section into a discontinuous conduction mode (DCM) operation section and a continuous conduction mode (CCM) operation section according to a zero crossing detection signal output by the zero crossing detector, a variable oscillator that changes and outputs a clock frequency signal according to the operation section discrimination signal output by the DCM/CCM detector, and a controller that controls switching of switches constituting the switching unit according to the clock frequency signal output by the variable oscillator.
1 . A switching converter equipped with an adaptive frequency control function, the switching converter comprising:
a switching unit;
an inductor connected between a switching node connected to the switching unit and a ground terminal;
an output capacitor connected between an output terminal connected to the switching unit and a ground terminal;
a zero crossing detector configured to receive a signal of the switching node and a signal of the output terminal, that are fed back, and detect whether or not an inductor current flowing through the inductor crosses a zero point;
a DCM/CCM detector configured to output an operation section discrimination signal that discriminates a current operation section by dividing the current operation section into a discontinuous conduction mode (DCM) operation section and a continuous conduction mode (CCM) operation section according to a zero crossing detection signal output by the zero crossing detector;
a variable oscillator configured to change and output a clock frequency signal according to the operation section discrimination signal output by the DCM/CCM detector; and
a controller configured to control switching of switches constituting the switching unit according to the clock frequency signal output by the variable oscillator.
2 . The switching converter of claim 1 , wherein
the zero crossing detector is configured to output the zero crossing detection signal when the inductor current reaches approximately zero within one cycle.
3 . The switching converter of claim 2 , wherein
the DCM/CCM detector is configured to:
determine the current operation section as the DCM operation section when the zero crossing detection signal is continuously received from the zero crossing detector, and
determine the current operation section as the CCM operation section when the zero crossing detection signal is not received from the zero crossing detector.
4 . The switching converter of claim 3 , wherein
the variable oscillator is configured to:
output a clock frequency signal corresponding to a DCM operating frequency when the operation section discrimination signal output by the DCM/CCM detector indicates the DCM operation section, and
output a clock frequency signal corresponding to a CCM operating frequency higher than the DCM operating frequency when the operation section discrimination signal output by the DCM/CCM detector indicates the CCM operation section.
5 . The switching converter of claim 4 , wherein
the controller is configured to:
control switching of the switches by applying a pulse width modulation (PWM) signal corresponding to the DCM operating frequency or the CCM operating frequency to gate terminals of the switches constituting the switching unit according to the clock frequency signal output by the variable oscillator.