Switched-mode power supply

Abstract

The present invention provides a switched-mode power supply. The ripple-control switched-mode power supply integrates a ripple injection function into an feedback voltage in a control circuit without increasing the number of external terminals. The ripple-control switched-mode power supply includes a control circuit 20 to switch on / off a drive switching element SW1 for making current through an inductor. The control circuit comprises: a voltage comparator 23 comparing the feedback voltage with a predetermined voltage; a ripple injection circuit 27, wherein the ripple injection circuit has an integrator outputting an integral of the voltage at the node between the driver switching element and the inductor, and a series RC circuit for adding a ripple component to the feedback voltage; and a control pulse generator 24 generating the control pulse based on an output of the voltage comparator. The switched-mode power supply is configured to switch on / off the drive switching element based on the control ripple generated by the control pulse generator.

Description

technical field [0001] The present invention relates to a switching regulator type DC-DC converter for converting DC voltage, and more particularly to a switching power supply device having a pulse injection function. Background technique [0002] As a circuit that converts a DC input voltage and outputs a DC voltage having a different potential, there is a DC-DC converter (DC-DC converter) of a switching regulator type. This DC-DC converter includes a driving switching element that applies a DC voltage supplied from a DC power source such as a battery to an inductor (coil) to cause a current to flow through the inductor (inductor), a rectifying element, and a control circuit. , causing the coil to store energy, the rectifying element rectifies the current of the coil during the energy release period when the driving switching element is turned off, and the control circuit controls the turning on and off of the driving switching element. [0003] Conventionally, as the cont...

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Problems solved by technology

[0009] Therefore, a terminal for connecting the capacitor Cff is required in addition to the terminal for applying the output voltage, so the number of external terminals (the number of pins) increases, leading to an increase in cost.

In addition, due to the limitation of the number of external terminals of the IC, it may not be possible to mount the ripple injection function.

In addition, since the feedforward capacitor Cff in the switching power supply of Patent Document 1 is an element with a large capacitance value, there is a problem that an external element needs to be used, and the number of parts increases.

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