Switching converter and control circuit and control method thereof

Abstract

The invention discloses a switching converter and a control circuit and a control method thereof. The control circuit uses a first conduction time control circuit to obtain a first conduction time, and uses a PWM comparator to compare a superposed signal related to an error signal of the DC output voltage with a feedback signal related to the DC output voltage so as to generate an intermediate signal. The switch-on time of the switch tube of the switch converter is adaptively adjusted according to the intermediate signal and the first switch-on time, so that the switch-on time of the switch tube of the switch converter can be prolonged when a voltage drop event occurs at the load end, and the transient performance of the switch converter is improved.

Description

technical field [0001] The present invention relates to the technical field of switching power supplies, and more particularly, to a switching converter and its control circuit and control method. Background technique [0002] Switching converters have been widely used in electronic systems to generate operating voltages and currents required by internal circuit modules or loads. The switching converter uses a power switch tube to control the power transmission from the input terminal to the output terminal, so that a constant output voltage and / or output current can be provided at the output terminal. In switching converters, the ripple-based constant on-time control method has the advantages of good light-load efficiency, fast transient response and easy implementation, so it has been widely used in recent years. [0003] figure 1 A schematic circuit diagram of a switching converter according to the prior art is shown. The switching converter 100 includes a main circuit...

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Problems solved by technology

Since this type of output filter produces very little output ripple even in the presence of a lot of noise, and the capacitor ripple is phase delayed compared to the inductor ripple, sub-harmonic oscillations can occur in the system , so it may lead to the instability of the control system

However, using a capacitor with a large ESR (such as an electrolytic capacitor) as the output capacitor at the output end of the switching converter 100 will not only increase the circuit area and cost, but also cause the ripple of the output voltage to increase and cause large fluctuations. normal operation of the stage circuit

[0007] In addition, the transient response of the switching converter 100 in the prior art is relatively slow, and when a large voltage drop event occurs at the load end, the voltage at the output end will change. Limits the application of this control model in areas requiring fast transient response

Moreover, due to the limitation of the conduction time of the switch control signal, the switching converter 100 cannot provide stable power supply when the input voltage Vin and the output voltage Vout are close, which reduces the overall efficiency of the switching converter.

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