Semiconductor device provided with feedback circuit including resistive element and capacitive element

Abstract

The present invention provides a switching power supply circuit capable of stabilizing an output voltage as well as increasing a response speed of the output voltage by improving a phase margin of an open loop as a whole of the switching power supply circuit. The switching power supply circuit according to the present invention includes a resistor and a capacitor in addition to a configuration of a conventional switching power supply circuit. The resistor is connected between a node and the capacitor. The capacitor is connected between the resistor and another node. The resistor and the capacitor configure a phase compensation circuit. The phase compensation circuit has a cut-off frequency in accordance with a resonance frequency of an inductor and a capacitor by adjusting a resistance value of the resistor and a capacitance of the capacitor.

1 - 16 . (canceled) 
   
   
       17 . A switching power supply circuit comprising:
 an input terminal;   an output terminal:   a NMOS transistor whose source electrode is connected to a ground potential, drain electrode is connected to a first node, and gate electrode is connected to an output terminal of a gate driver, wherein said first node is located between said drain electrode and said output terminal;   an output voltage detection circuit which detects an output voltage as a voltage of said output terminal;   a control circuit which is connected between said gate electrode of said NMOS transistor and said output voltage detection circuit, and controls driving of said NMOS transistor on the basis of said output voltage detected by said output voltage detection circuit; and   a feedback circuit which is connected between said gate electrode of said NMOS transistor and a second node located between said output voltage detection circuit and said control circuit, and includes a resistive element and a capacitive element, wherein   said control circuit comprises:
 an error amplifier whose first input node is connected to said second node and whose output is connected to a third node; 
 a power supply connected between a second input node of the error amplifier and a ground potential; 
 a pulse width modulator comparator with a first input connected to said third node, a second input node connected to a triangular wave oscillator, and whose output is connected to the input of said gate driver, wherein 
   said resistive element is connected between said gate electrode of said NMOS transistor and said capacitive element, and said capacitive element is connected between said resistive element and said first input node of said error amplifier, and wherein   said control circuit includes a phase compensation circuit being connected between said input node of the error amplifier and an output node of the error amplifier via said third node.   
   
   
       18 . The switching power supply circuit according to  claim 17 , wherein
 said resistive element is connected to said second node through said capacitive element.   
   
   
       19 . The switching power supply circuit according to  claim 17 , wherein
 said phase compensation circuit includes a resistive element and a capacitive element,   a difference between the order of a resistance value of said resistive element in said feedback circuit and the order of a resistance value of said resistive element in said phase compensation circuit is within two digits, and   a difference between the order of a capacitance of said capacitive element in said feedback circuit and the order of a capacitance of said capacitive element in said phase compensation circuit is within two digits.