SWITCHING REGULATOR
A switching regulator includes a ripple generating circuit that generates a ripple voltage signal having a voltage that increases when a first switch element is on and decreases when a second switch element is on, or a voltage that decreases when the first switch element is on and increases when the second switch element is on, a comparator that compares the ripple voltage signal to a reference voltage, and generates a comparison signal indicating the comparison result, and a switch element control circuit that generates, according to the comparison signal, a control signal to switch on and off of the first switch element and a control signal to switch on and off of the second switch element, and applies the control signals to the first and second switch elements, respectively, wherein the ripple generating circuit generates the ripple voltage signal based on the control signals.
1 . A switching regulator configured to convert an input voltage into a predetermined output voltage using first and second switch elements series-connected between a voltage source of the input voltage and a terminal of a ground voltage, comprising:
a ripple generating circuit configured to generate a ripple voltage signal having a voltage that increases when the first switch element is on and decreases when the second switch element is on, or a voltage that decreases when the first switch element is on and increases when the second switch element is on;
a comparator configured to compare the ripple voltage signal to a first reference voltage, and generate a comparison signal indicating the comparison result; and
a switch element control circuit configured to generate, according to the comparison signal, a first control signal to switch on and off of the first switch element and a second control signal to switch on and off of the second switch element, and apply the first and second control signals to the first and second switch elements, respectively, wherein
the ripple generating circuit generates the ripple voltage signal based on the first and second control signals.
2 . The switching regulator according to claim 1 , wherein
the ripple generating circuit includes
third and fourth switch elements series-connected between the voltage source of the input voltage and the terminal of the ground voltage, and
an integrating circuit including a first resistor element and a first capacitor series-connected between the terminal of the ground voltage and a node between the third and fourth switch elements, the integrating circuit configured to generate an integrated voltage by integrating a voltage at the node, and
on and off of the third and fourth switch elements are synchronized with on and off of the first and second switch elements, respectively.
3 . The switching regulator according to claim 2 , wherein
the ripple generating circuit generates the ripple voltage signal by superimposing the integrated voltage on the voltage proportional to the output voltage.
4 . The switching regulator according to claim 3 , wherein
the ripple generating circuit includes
second and third resistor elements series-connected between a terminal of the output voltage and the terminal of the ground voltage, and
a second capacitor connected to a node between the first resistor element and the first capacitor and to a node between the second and third resistor elements, and
the ripple generating circuit generates the ripple voltage signal at the node between the second and third resistor elements by superimposing the integrated voltage through the second capacitor on the output voltage divided at the node between the second and third resistor elements.
5 . The switching regulator according to claim 4 , wherein
the ripple generating circuit includes a third capacitor in parallel with the second resistor element between the terminal of the output voltage and the node between the second and third resistor elements.
6 . The switching regulator according to claim 1 , further comprising:
a backflow detection circuit configured to generate a backflow detection signal indicating whether or not a backflow current is generated, which flows from a node between the first and second switch elements to the second switch element; and
a mode signal generating circuit configured to generate a mode signal indicating any of a PFM (Pulse Frequency Modulation) control mode and a PWM (Pulse Width Modulation) control mode according to the backflow detection signal and the comparison signal, wherein
consumption current of the circuits included in the switching regulator controlled based on the mode signal.
7 . The switching regulator according to claim 6 , wherein
the mode signal generating circuit includes a counter circuit configured to count rising edges or falling edges of the backflow detection signal, and
the mode signal generating circuit generates a mode signal indicating the PFM control mode when the counter circuit counts a predetermined number of rising edges or falling edges of the backflow detection signal.
8 . The switching regulator according to claim 6 , wherein
the mode signal generating circuit generates a mode signal indicating the PWM control mode at a predetermined point in time determined by the comparison signal and the first control signal when the backflow detection signal is at a low level.
9 . The switching regulator according to claim 6 , wherein
the mode signal generating circuit has an input signal to select any of PWM fixing control to always generate a mode signal indicating the PWM control mode and automatic control to generate the mode signal indicating either the PFM control mode or the PWM control mode according to the backflow detection signal and the comparison signal.
10 . A switching regulator configured to convert an input voltage into a predetermined output voltage using first and second switch elements series-connected between a voltage source of the input voltage and a terminal of a ground voltage, comprising:
a ripple generating circuit configured to generate a ripple voltage signal having a voltage that increases when the first switch element is on and decreases when the second switch element is on, or a voltage that decreases when the first switch element is on and increases when the second switch element is on;
a comparator configured to compare the ripple voltage signal to a first reference voltage, and generate a comparison signal indicating the comparison result; and
a switch element control circuit configured to generate, according to the comparison signal, a first control signal to switch on and off of the first switch element and a second control signal to switch on and off of the second switch element, and apply the first and second control signals to the first and second switch elements, respectively, wherein
the ripple generating circuit generates the ripple voltage signal based on the first and second control signals, and
the ripple generating circuit includes
third and fourth switch elements series-connected between a voltage source of a second reference voltage and the terminal of the ground voltage, and
an integrating circuit including a first resistor element and a first capacitor series-connected between the terminal of the ground voltage and a node between the third and fourth switch elements, the integrating circuit configured to generate an integrated voltage by integrating a voltage at the node, and
on and off of the third and fourth switch elements are synchronized with on and off of the first and second switch elements, respectively.
11 . The switching regulator according to claim 10 , wherein
the ripple generating circuit generates the ripple voltage signal by superimposing the integrated voltage on the voltage proportional to the output voltage.
12 . The switching regulator according to claim 11 , wherein
the ripple generating circuit includes
second and third resistor elements series-connected between a terminal of the output voltage and the terminal of the ground voltage, and
a second capacitor connected to a node between the first resistor element and the first capacitor and to a node between the second and third resistor elements, and
the ripple generating circuit generates the ripple voltage signal at the node between the second and third resistor elements by superimposing the integrated voltage through the second capacitor on the output voltage divided at the node between the second and third resistor elements.
13 . The switching regulator according to claim 12 , wherein
the ripple generating circuit includes a third capacitor in parallel with the second resistor element between the terminal of the output voltage and the node between the second and third resistor elements.
14 . The switching regulator according to claim 10 , further comprising:
a backflow detection circuit configured to generate a backflow detection signal indicating whether or not a backflow current is generated, which flows from a node between the first and second switch elements to the second switch element; and
a mode signal generating circuit configured to generate a mode signal indicating any of a PFM (Pulse Frequency Modulation) control mode and a PWM (Pulse Width Modulation) control mode according to the backflow detection signal and the comparison signal, wherein
consumption current of the circuits included in the switching regulator is controlled based on the mode signal.
15 . The switching regulator according to claim 14 , wherein
the mode signal generating circuit includes a counter circuit configured to count rising edges or falling edges of the backflow detection signal, and
the mode signal generating circuit generates a mode signal indicating the PFM control mode when the counter circuit counts a predetermined number of rising edges or falling edges of the backflow detection signal.
16 . The switching regulator according to claim 14 , wherein
the mode signal generating circuit generates a mode signal indicating the PWM control mode at a predetermined point in time determined by the comparison signal and the first control signal when the backflow detection signal is at a low level.
17 . The switching regulator according to claim 14 , wherein
the mode signal generating circuit has an input signal to select any of PWM fixing control to always generate a mode signal indicating the PWM control mode and automatic control to generate the mode signal indicating either the PFM control mode or the PWM control mode according to the backflow detection signal and the comparison signal.
18 . A method of controlling a switching regulator configured to convert an input voltage into a predetermined output voltage using first and second switch elements series-connected between a voltage source of the input voltage and a terminal of a ground voltage, comprising the steps of:
generating a ripple voltage signal having a voltage that increases when the first switch element is on and decreases when the second switch element is on, or a voltage that decreases when the first switch element is on and increases when the second switch element is on;
comparing the ripple voltage signal to a first reference voltage, and generating a comparison signal indicating the comparison result; and
generating, according to the comparison signal, a first control signal to switch on and off of the first switch element and a second control signal to switch on and off of the second switch element, and applying the first and second control signals to the first and second switch elements, respectively, wherein
the step of generating the ripple voltage signal generates the ripple voltage signal based on the first and second control signals.
19 . The method according to claim 18 , wherein the step of generating the ripple voltage signal prepares third and fourth switch elements series-connected between the voltage source of the input voltage and the terminal of the ground voltage, and an integrating circuit including a first resistor element and a first capacitor series-connected between the terminal of the ground voltage and a node between the third and fourth switch elements, the integrating circuit configured to generate an integrated voltage by integrating a voltage at the node, and synchronizes on and off of the third and fourth switch elements with on and off of the first and second switch elements, respectively.
20 . The method according to claim 19 , wherein
the step of generating the ripple voltage signal generates the ripple voltage signal by superimposing the integrated voltage on the voltage proportional to the output voltage.
21 . The method according to claim 18 , wherein the step of generating the ripple voltage signal prepares third and fourth switch elements series-connected between a voltage source of a second reference voltage and the terminal of the ground voltage, and an integrating circuit including a first resistor element and a first capacitor series-connected between the terminal of the ground voltage and a node between the third and fourth switch elements, the integrating circuit configured to generate an integrated voltage by integrating a voltage at the node, and synchronizes on and off of the third and fourth switch elements with on and off of the first and second switch elements, respectively.