Patent ID: 8531446

Claim:
A DC-DC converter, comprising: a burst mode circuit configured to work when a load connected to an output terminal of the DC-DC converter is a light load of which a load value is a predetermined threshold value or less; and a PWM mode circuit configured to work when the load is a heavy load of which the load value is greater than the threshold value, wherein the burst mode circuit is further configured to: switch a voltage at the output terminal during a period of time when a feedback voltage from the output terminal reaches a high potential reference voltage; generate a switch start signal with frequencies divided by predetermined frequency division values; and switch the voltage at the output terminal in response to the switch start signal, wherein the PWM mode circuit is further configured to switch the voltage at the output terminal during a period of time when a ramp wave signal is greater than a difference voltage between the feedback voltage and a predetermined PWM mode reference voltage, and wherein the burst mode circuit comprises: a first comparator configured to compare the high potential reference voltage with the feedback voltage, a second comparator configured to compare a low potential reference voltage with the feedback voltage, a third comparator configured to detect a current between the output terminal and a ground voltage source, a frequency generation unit configured to generate a signal with frequencies which vary depending on an output from the third comparator; a frequency conversion unit configured to divide the signal from the frequency generation unit by the use of the frequency division value, generating the switch start signal, a logic unit configured to output switch-on pulses in response to the switch start signal from the frequency conversion unit during a period of time when the feedback voltage increases to the high potential reference voltage, and a driving unit configured to control a transistor which switches a current path between the output terminal and the ground voltage source in response to the switch-on pulses from the logic unit.