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US 2015/0028830 A1Published application
Current-mode buck converter and electronic system using the same
AssigneeAnpec Electronics Corporation
InventorChih-Ning CHEN
Life of this patent
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Abstract
A current-mode buck converter is disclosed, wherein the current-mode buck converter operates in a pulse width modulation (PWM) mode or a pulse frequency modulation (PFM) mode. When the current-mode buck converter enters into the PFM mode, the voltage level of the parking voltage is maintained at the voltage level of compensation voltage, so as to decrease switch loss of the current-mode buck converter operating between PWM mode and PFM mode, and stabilize the output voltage of the current-mode buck converter.
Claims18
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 one terminal 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 compensation switch, having a control terminal receiving a mode switch signal and accordingly making one terminal of the compensation switch be switched to one of a PWM terminal and a PFM terminal;
- a compensation resistor, having one terminal connected to another terminal of the compensation switch;
- and
- a compensation capacitor, having a first terminal connected to another terminal of the compensation resistor, having a second terminal connected the ground voltage,
- a first comparator, receiving 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 so as to generate and transmit a sleep-trigger signal to the current detecting circuit and the slope compensating circuit;
- 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, receiving the detection voltage and outputting 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.
18 more elements
An electronic system, comprising:
- a current-mode buck converter, receiving an input voltage, and the input voltage being step down to output voltage;
- and
- a load, connected to the current-mode buck converter for receiving the output voltage,
- wherein the current-mode buck converter comprises:
- 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 one terminal 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 compensation switch, having a control terminal receiving a mode switch signal and accordingly making one terminal of the compensation switch be switched to one of a PWM terminal and a PFM terminal;
- a compensation resistor, having one terminal connected to another terminal of the compensation switch;
- and
- a compensation capacitor, having a first terminal connected to another terminal of the compensation resistor, having a second terminal connected the ground voltage,
- a first comparator, receiving 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 so as to generate and transmit a sleep-trigger signal to the current detecting circuit and the slope compensating circuit;
- 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, receiving the detection voltage and outputting 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.
22 more elements
Dependencies are inferred from the claim text.