Switching regulator control circuit which prevents shoot-through current in a synchronous rectifier
View Patent ↗In a maximum duty control state of a switching regulator control circuit, a period of time during which any one of a step-up switching circuit and a synchronous rectification switching circuit is always off is ensured, thereby preventing the switching efficiency from being remarkably deteriorated. In a maximum duty control state, a voltage difference is provided between a limiter voltage that is inputted to a comparator that controls the switching operation of the step-up switching circuit and a limiter voltage that is inputted to a comparator that controls the switching operation of the synchronous rectification switching circuit, to thereby ensure the period of time during which any one of the step-up switching circuit and the synchronous rectification switching circuit is always off.
1. A switching regulator control circuit, comprising:
a first reference voltage generator circuit;
a second reference voltage generator circuit;
a third reference voltage generator circuit;
a dividing resistor for dividing an output voltage of the switching regulator;
a chopping wave generator circuit;
an error amplifier for inputting a voltage of the first reference voltage generator circuit and a voltage divided by the dividing resistor;
a first comparator for receiving a voltage obtained by dropping an output of the error amplifier by a voltage of a first constant voltage source, a voltage of the third reference voltage generator circuit, and a voltage of the chopping wave generator circuit;
a second comparator for receiving a voltage obtained by dropping an output of the error amplifier by a voltage of a second constant voltage source, a voltage of the second reference voltage generator circuit, and the voltage of the chopping wave generator circuit;
a synchronous rectification switching circuit that is controlled based on an output of the first comparator; and
a step-up switching circuit that is controlled based on an output of the second comparator.
2. The switching regulator control circuit according to claim 1 , wherein the voltage of the second reference voltage generator circuit and the voltage of the third reference voltage generator circuit are lower than a maximum voltage of the chopping wave generator circuit, and one of the step-up switching circuit and the synchronous rectification switching circuit is always off even when the output voltage of the switching regulator drops.
3. The switching regulator control circuit according to claim 1 , wherein the voltage of the third reference voltage generator circuit is a voltage obtained by adding a difference between the voltage of the first constant voltage source and the voltage of the second constant voltage source to the voltage of the second reference voltage generator circuit.
4. The switching regulator control circuit according to claim 1 , wherein there is provided a period of time during which the synchronous rectification switching circuit and the step-up switching circuit are off at the same time.
5. A switching regulator comprising the switching regulator control circuit according to claim 1 .