DC-DC converter
View Patent ↗To provide a DC-DC converter which prevents overshoot from occurring in an output voltage even when a power supply voltage rises from a voltage lower than a desired output voltage of the DC-DC converter to a normal voltage. A DC-DC converter is equipped with a 100% DUTY detection circuit which detects a 100% DUTY state of a PWM comparator, a power supply voltage rise detection circuit which detects a rise in a power supply voltage, and a discharge control circuit which lowers an output voltage of an error amplifier. The DC-DC converter is configured to lower the output voltage of the error amplifier when a power supply voltage rise detection signal is outputted where a 100% DUTY state is reached and the output voltage of the error amplifier is higher than a predetermined voltage.
1. A DC-DC converter comprising:
an error amplifier which amplifies a difference between a divided voltage obtained by dividing a voltage outputted from an output transistor and a reference voltage to output a voltage VERR;
a ramp wave generating circuit which generates a ramp wave;
a PWM comparator which compares the voltage VERR and the ramp wave and thereby outputs a signal PWM;
a 100% DUTY detection circuit which detects that the signal PWM is brought to 100% DUTY, and outputs a 100% DUTY detection signal;
a phase compensation capacitor and a phase compensation resistor provided at an output terminal of the error amplifier;
a power supply voltage rise detection circuit which detects a rise in a power supply voltage; and
a discharge control circuit which discharges an electric charge of the phase compensation capacitor in response to an output signal of the power supply voltage rise detection circuit.
2. The DC-DC converter according to claim 1 , wherein the discharge control circuit outputs a discharge control signal when the 100% DUTY detection signal is inputted when the voltage VERR is higher than a predetermined voltage.
3. The DC-DC converter according to claim 2 , wherein the power supply voltage rise detection circuit is equipped with a capacitor having one end connected to a power supply terminal, and a switch having one end connected to the other end of the capacitor and the other end connected to a ground terminal, and being controlled by the discharge control signal, and
wherein the power supply voltage rise detection circuit provides a connection point of the switch and the capacitor as an output terminal.
4. The DC-DC converter according to claim 1 , wherein the power supply voltage rise detection circuit is equipped with a capacitor having one end connected to a power supply terminal, and a switch having one end connected to the other end of the capacitor and the other end connected to a ground terminal, and being controlled by the 100% DUTY detection signal, and
wherein the power supply voltage rise detection circuit provides a connection point of the switch and the capacitor as an output terminal.
5. The DC-DC converter according to claim 4 , wherein the discharge control circuit discharges the electric charge of the phase compensation capacitor when a detection signal is inputted from the power supply voltage rise detection circuit when the voltage VERR is higher than a predetermined voltage.