Switching regulator control circuit and DC/DC converter
Provided is a DC/DC converter capable of providing overvoltage protection reliably without being affected by, for example, an external element connected to an output terminal. The DC/DC converter includes a comparator, an RS-FF circuit, a drive circuit, and an ON-timer circuit, and the ON-timer circuit includes: a current source circuit which provides an electric current based on a power supply voltage; a ripple generation circuit which generates a ripple voltage; an averaging circuit which averages the ripple voltage; a timer circuit which generates an ON-timer signal; and an overvoltage protection circuit (clamp circuit).
1. A switching regulator control circuit, comprising:
a comparator configured to compare a divided voltage corresponding to an output voltage from a DC/DC converter and a reference voltage;
an RS-FF circuit having a set terminal connected to an output terminal of the comparator, and an output terminal connected to an input terminal of a drive circuit; and
an ON-timer circuit having an input terminal connected to the output terminal of the RS-FF circuit, and an output terminal connected to a reset terminal of the RS-FF circuit,
the ON-timer circuit including:
a current source circuit configured to provide an electric current based on a power supply voltage;
a ripple generation circuit configured to generate a ripple voltage depending on the electric current and an output signal from the RS-FF circuit;
an averaging circuit configured to average the ripple voltage;
a timer circuit configured to generate an ON-timer signal depending on the electric current, the output signal from the RS-FF circuit, and the averaged ripple voltage; and
a clamp circuit configured to clamp the ripple voltage to a predetermined voltage.
2. The switching regulator control circuit according to claim 1 , wherein the clamp circuit is configured to clamp the ripple voltage provided by the ripple generation circuit.
3. The switching regulator control circuit according to claim 1 , wherein the clamp circuit is configured to clamp the averaged ripple voltage provided by the averaging circuit.
4. A switching regulator control circuit, comprising:
a comparator configured to compare a divided voltage corresponding to an output voltage from a DC/DC converter and a reference voltage;
an RS-FF circuit having a set terminal connected to an output terminal of the comparator, and an output terminal connected to an input terminal of a drive circuit; and
an ON-timer circuit having an input terminal connected to the output terminal of the RS-FF circuit, and an output terminal connected to a reset terminal of the RS-FF circuit,
the ON-timer circuit including:
a current source circuit configured to provide an electric current based on a power supply voltage;
a ripple generation circuit configured to generate a ripple voltage depending on the electric current and an output signal from the RS-FF circuit;
an averaging circuit configured to average the ripple voltage;
a timer circuit configured to generate an ON-timer signal depending on the electric current, the output signal from the RS-FF circuit, and the averaged ripple voltage; and
an overvoltage protection circuit configured to provide the ON-timer signal irrespective of the ON-timer signal from the timer circuit when detecting that the averaged ripple voltage is a predetermined voltage or more.
5. A DC/DC converter, comprising:
the switching regulator control circuit of claim 1 ;
a coil and a capacitor provided at an output terminal of the switching regulator control circuit;
an output terminal of the DC/DC converter provided at a connection point between the coil and the capacitor; and
a voltage divider circuit which is provided between the output terminal of the DC/DC converter and an input terminal of the switching regulator control circuit, and is configured to provide a divided voltage obtained by dividing an output voltage from the DC/DC converter to the input terminal of the switching regulator control circuit.
6. A DC/DC converter, comprising:
the switching regulator control circuit of claim 4 ;
a coil and a capacitor provided at an output terminal of the switching regulator control circuit;
an output terminal of the DC/DC converter provided at a connection point between the coil and the capacitor; and
a voltage divider circuit which is provided between the output terminal of the DC/DC converter and an input terminal of the switching regulator control circuit, and is configured to provide a divided voltage obtained by dividing an output voltage from the DC/DC converter to the input terminal of the switching regulator control circuit.