The present disclosure relates to switching regulators, and more particularly to overcurrent protection of switching regulators in a hysteretic control mode.
In general, switching regulators can efficiently convert electrical power, and thus are used as power supply circuits of various electronic devices. In particular, in mobile devices using a battery as an input voltage source, control is performed, such as appropriately changing electrical power supplied to an electronic circuit in accordance with the use condition so as to enable long-term use. Therefore, switching regulators responding to a change in the use condition at high speed are required.
Some of these switching regulators do not perform feedback control using error amplifiers but hysteretic control for controlling a switching element using a comparator so that an output voltage falls within a predetermined range. The hysteretic control does not require operation time determined by a slew rate of an error amplifier, and thus, enables high-speed responses.
Although output ripple amplitude needs to be large to perform stable hysteretic control, a proper output voltage cannot be obtained when the amplitude is too large. Thus, a virtual ripple voltage, which is obtained by superimposing a voltage having a reversed waveform to an output ripple on a reference voltage, is used to control a switching element to be on for a predetermined time period, when an output voltage is lower than the virtual ripple voltage.