PWM boost system and start-up method thereof
AssigneeAdvanced Analog Technology, Inc.
InventorsYung Ching Chang, Yen Kuo Lo, Wen Chia Pi
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Abstract
A PWM (pulse width modulation) boost system includes a boost circuit, a voltage dividing circuit, a comparator, a PWM circuit, a pre-oscillator, and a current limit circuit. A start-up method of the PWM boost system includes (1) providing an error voltage; (2) generating a PWM signal according to the error voltage; (3) controlling a switch in a boost circuit with the PWM signal, so as to control an inductor current flowing through a boost inductor in the boost circuit; (4) charging a capacitor in the boost circuit with the inductor current, wherein charges stored in the capacitor define a DC output voltage; and (5) providing a feedback voltage according to the DC output voltage to adjust the error voltage.
Claims14
A pulse width modulation (PWM) boost system, comprising:
- a boost circuit comprising a boost inductor, wherein said boost circuit increases a first voltage to generate a DC output voltage;
- a voltage dividing circuit configured to generate a feedback voltage with said DC output voltage;
- a comparator configured to compare a reference voltage with said feedback voltage in a PWM period to generate an error voltage;
- a PWM circuit configured to receive said error voltage to generate a PWM signal to control said boost circuit;
- a pre-oscillator configured to generate a pre-oscillation signal to said PWM circuit in a pre-oscillation period;
- and
- a current limit circuit configured to control an inductor current flowing through said boost inductor;
- wherein a pre-oscillation period is a period when said DC output voltage is lower than a first predetermined voltage, and wherein a PWM period is a period when said DC output voltage is higher than said first predetermined voltage.
A start-up method of a PWM boost system, comprising the steps of:
- providing an error voltage;
- generating a PWM signal according to said error voltage;
- controlling a switch in a boost circuit with said PWM signal, so as to control an inductor current flowing through a boost inductor in said boost circuit;
- charging a capacitor in said boost circuit with said inductor current, wherein charges stored in said capacitor define a DC output voltage;
- and
- providing a feedback voltage according to said DC output voltage to adjust said error voltage;
- wherein a pre-oscillation period is a period when said DC output voltage is lower than a first predetermined voltage, and wherein a PWM period is a period when said DC output voltage is higher than said first predetermined voltage.
Dependencies are inferred from the claim text.