Switched-mode power supply having an adaptive on-time function and controlling output with a ripple control method
First Claim
1. A switched-mode power supply that outputs a voltage different from an input voltage, the switched-mode power supply comprising:
- an inductor connected between a voltage input terminal to which a DC voltage is input and an output terminal to which a load is connected;
a drive switching element that causes a current to intermittently flow through the inductor; and
a control circuit that is provided on a semiconductor chip as a semiconductor integrated circuit and that generates a drive pulse in response to the voltage input to the voltage input terminal and a feedback voltage from the output terminal to switch on/off the drive switching element,wherein the control circuit comprises;
a ripple injection circuit connected between a first node connecting the drive switching element and the inductor and a second node at which the feedback voltage is generated, the ripple injection circuit including (i) a first filter that includes a first resistor and a first capacitor connected in series between the first node and a ground point, and (ii) a second filter that includes a second resistor and a second capacitor connected in series between a third node, which is between the first resistor and the first capacitor, and the second node, wherein the ripple injection circuit adds a ripple component to the feedback voltage through the first filter and the second filter based on a voltage at the first node, and the ripple injection circuit adds the ripple directly to the second node at which the feedback voltage is generated;
a simulated voltage generation circuit comprising a filter circuit that smoothes a voltage corresponding to the voltage at the first node, wherein the simulated voltage generation circuit receives a voltage at the third node and generates and outputs a simulated voltage corresponding to the output voltage, and wherein the voltage at the first node has a rectangular waveform with an amplitude corresponding to the voltage input to the voltage input terminal;
a timer that receives the simulated voltage output from the simulated voltage generation circuit and measures a time corresponding to the input voltage and the simulated voltage;
a voltage comparison circuit that compares the feedback voltage and a predetermined voltage;
a control pulse generation circuit that generates a control pulse having a pulse width corresponding to the time measured by the timer based on output from the timer and output from the voltage comparison circuit; and
wherein the control circuit varies the pulse width of the control pulse in accordance with a variation in the input voltage and the simulated voltage and outputs the drive pulse, corresponding to the control pulse, to maintain a constant switching cycle.
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Abstract
A ripple-control switched-mode power supply includes a control circuit to switch on/off a drive switching element. The control circuit includes a simulated voltage generation circuit that smoothes a voltage at a node connecting the drive switching element and an inductor and that generates a simulated voltage corresponding to an output voltage; a timer that measures a time corresponding to an input voltage and the simulated voltage; a voltage comparison circuit that compares a feedback voltage and a predetermined voltage; and a control pulse generation circuit that generates a control pulse having a pulse width corresponding to the time based on outputs from the timer and the voltage comparison circuit. The control circuit varies the pulse width of the control pulse in accordance with a variation in the input voltage to maintain a constant switching cycle.
24 Citations
11 Claims
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1. A switched-mode power supply that outputs a voltage different from an input voltage, the switched-mode power supply comprising:
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an inductor connected between a voltage input terminal to which a DC voltage is input and an output terminal to which a load is connected; a drive switching element that causes a current to intermittently flow through the inductor; and a control circuit that is provided on a semiconductor chip as a semiconductor integrated circuit and that generates a drive pulse in response to the voltage input to the voltage input terminal and a feedback voltage from the output terminal to switch on/off the drive switching element, wherein the control circuit comprises; a ripple injection circuit connected between a first node connecting the drive switching element and the inductor and a second node at which the feedback voltage is generated, the ripple injection circuit including (i) a first filter that includes a first resistor and a first capacitor connected in series between the first node and a ground point, and (ii) a second filter that includes a second resistor and a second capacitor connected in series between a third node, which is between the first resistor and the first capacitor, and the second node, wherein the ripple injection circuit adds a ripple component to the feedback voltage through the first filter and the second filter based on a voltage at the first node, and the ripple injection circuit adds the ripple directly to the second node at which the feedback voltage is generated; a simulated voltage generation circuit comprising a filter circuit that smoothes a voltage corresponding to the voltage at the first node, wherein the simulated voltage generation circuit receives a voltage at the third node and generates and outputs a simulated voltage corresponding to the output voltage, and wherein the voltage at the first node has a rectangular waveform with an amplitude corresponding to the voltage input to the voltage input terminal; a timer that receives the simulated voltage output from the simulated voltage generation circuit and measures a time corresponding to the input voltage and the simulated voltage; a voltage comparison circuit that compares the feedback voltage and a predetermined voltage; a control pulse generation circuit that generates a control pulse having a pulse width corresponding to the time measured by the timer based on output from the timer and output from the voltage comparison circuit; and wherein the control circuit varies the pulse width of the control pulse in accordance with a variation in the input voltage and the simulated voltage and outputs the drive pulse, corresponding to the control pulse, to maintain a constant switching cycle. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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Specification