Patent ID: 9154037
Filing Date: 2015-10-06
Classification: H02M,Y02B

Abstract:
1. A current-mode buck converter, comprising: an oscillator, generating an oscillation signal; an input terminal, receiving an input voltage; an output terminal, receiving an output voltage; a feedback module, connected to the output terminal, and the feedback module generating a feedback signal according to the output voltage; a switch module, determining an electric connection of the input terminal, ground voltage and the output terminal according to a next-stage switch signal; a current detecting circuit, connected to the input terminal so as to receive an input current, for generating an image current; a slope compensating circuit, receiving a pre-stage switch signal and accordingly generating a slope compensating current; a detection resistor, having a first terminal electrically connected to the current detecting circuit and the slope compensating circuit, for transforming a sum of the image current and the slope compensating current to a detection voltage; an error amplifier, connected to the feedback module, for amplifying a difference of the feedback signal and a first reference voltage so as to generate a difference voltage; a modulation compensating circuit, connected to the error amplifier, for compensating frequency response of the current-mode buck converter according to the difference voltage and then generating a compensation voltage, wherein the modulation compensating circuit comprises: a first comparator, having an non-positive input end electrically connected to the first terminal of the detection resistor to receive the detection voltage and comparing the detection voltage with the compensation voltage so as to generate a PWM signal accordingly; a second comparator, receiving and comparing the compensation voltage with a threshold voltage, and transmitting a sleep-trigger signal with high voltage level to the current detecting circuit and the slope compensating circuit for disabling the current detecting circuit and the slope compensating circuit when the compensation voltage is smaller than the threshold voltage; a modulation control circuit, connected to the oscillator, the slope compensating circuit, the first comparator and the second comparator, for generating the pre-stage switch signal according to the PWM signal and the oscillation signal; a zero-crossing detecting circuit, connected to switch module, for detecting current; and a buffer, having an input end electrically connected to the first terminal of the detection resistor and an output end electrically connected to the PFM terminal, to receive the detection voltage and output the detection voltage to the PFM terminal, wherein when the current-mode buck converter enters into a pulse frequency modulation mode from a pulse width modulation mode, one terminal of the compensation switch is switched and connected to the PFM terminal from the PWM terminal for receiving the detection voltage, and voltage level of the detection voltage is equal to voltage level of the compensation voltage at this time, and thus reduces switch loss of the current-mode buck converter and stabilizes a transition between the pulse frequency modulation mode and the pulse width modulation mode.