Current mode control type switching regulator
View Patent ↗A switching regulator for converting input voltage to output voltage includes a switch; an inductor energized by input voltage by the switch; a rectifier for discharging the inductor; and a slope voltage generator for generating slope voltage inclined responsive to current of the inductor, amplifies a difference between reference voltage and divided output voltage, and compares the amplified voltage and the slope voltage to generate signal for controlling the switch. The slope voltage generator includes a detector for converting current flowing through the inductor when the switch is on into voltage; and a voltage generator for generating ramp voltage. These voltages are added as the slope voltage. The voltage generator includes constant current; a resistor; and a ramp capacitor charged by the constant current through the resistor. Voltage drop of the resistor is added to terminal voltage of the ramp capacitor to output the ramp voltage.
1. A current mode control type switching regulator for converting an input voltage into an output voltage that is a predetermined constant voltage, comprising:
a switching element;
an inductor energized by the input voltage in response to switching of the switching element;
a rectifier element for discharging the inductor; and
a slope voltage generating circuit unit configured to generate and output a slope voltage having an inclination responsive to a current flowing through the inductor,
said current mode control type switching regulator being configured to amplify a voltage difference between a predetermined reference voltage and a divided voltage obtained by dividing the output voltage; compare the amplified voltage and the slope voltage to generate a pulsed signal having a duty cycle determined by the comparison; and control switching of the switching element in response to the pulsed signal,
wherein the slope voltage generating circuit unit includes an inductor current detecting circuit for detecting a current flowing through the inductor when the switching element is on to energize the inductor and converting the detected current into a voltage; and a ramp voltage generating circuit for generating and outputting a ramp voltage having a predetermined inclination, said slope voltage generating circuit unit being configured to add the voltage obtained by the inductor current detecting circuit and the ramp voltage to generate the slope voltage;
the ramp voltage generating circuit includes a constant current circuit for generating and outputting a predetermined constant current; an offset voltage generating resistor through which the constant current outputted by the constant current circuit flows; and a ramp capacitor charged by the constant current outputted by the constant current circuit through the offset voltage generating resistor, said ramp voltage generating circuit being configured to add a voltage drop caused by the offset voltage generating resistor to a terminal voltage of the ramp capacitor to generate and output the ramp voltage.
2. The current mode control type switching regulator as claimed in claim 1 , wherein the ramp voltage generating circuit further includes an impedance converter circuit configured to perform impedance conversion on the ramp voltage and output the ramp voltage.