AC/DC CONVERTER
First Claim
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1. A control circuit used for an AC/DC converter configured to convert an AC voltage into a first DC voltage, wherein the AC/DC converter comprises:
- a first rectifier circuit configured to rectify and smooth the AC voltage so as to convert the AC voltage into a second DC voltage;
an insulating DC/DC converter configured to step up or otherwise step down the second DC voltage; and
a feedback circuit configured to generate a feedback voltage that corresponds to the first DC voltage,wherein the control circuit comprises;
an input detection terminal coupled to receive a first rectified voltage obtained by performing full-wave rectification of the AC voltage is input;
a power supply terminal connected to an external capacitor, and coupled to receive a third DC voltage generated on a primary side of a transformer of the DC/DC converter in an operating state of the DC/DC converter;
a feedback terminal coupled to receive the feedback voltage;
a depletion-type high-voltage first NMOS transistor having its drain connected to the input detection terminal and its gate connected to its source;
an AC voltage detection circuit configured to detect an amplitude of the AC voltage based on a current that flows through the first NMOS transistor;
a starter circuit arranged between the input detection terminal and the power supply terminal, and configured to charge the capacitor connected to the power supply terminal using the first rectified voltage in a startup operation of the AC/DC converter; and
a driving circuit configured to receive a voltage at the power supply terminal as its operating voltage, and to drive a switching transistor of the DC/DC converter according to the feedback voltage,and wherein the control circuit is monolithically integrated on a single semiconductor substrate.
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Abstract
A first rectified voltage obtained by rectifying an AC voltage is input to an input detection terminal of a control circuit. A first NMOS transistor configured as a depletion-type high-voltage element, and its drain is connected to the input detection terminal, and its gate is connected to its source. An AC voltage detection circuit detects the amplitude of the AC voltage based on a current that flows through the first NMOS transistor.
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Citations
32 Claims
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1. A control circuit used for an AC/DC converter configured to convert an AC voltage into a first DC voltage, wherein the AC/DC converter comprises:
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a first rectifier circuit configured to rectify and smooth the AC voltage so as to convert the AC voltage into a second DC voltage; an insulating DC/DC converter configured to step up or otherwise step down the second DC voltage; and a feedback circuit configured to generate a feedback voltage that corresponds to the first DC voltage, wherein the control circuit comprises; an input detection terminal coupled to receive a first rectified voltage obtained by performing full-wave rectification of the AC voltage is input; a power supply terminal connected to an external capacitor, and coupled to receive a third DC voltage generated on a primary side of a transformer of the DC/DC converter in an operating state of the DC/DC converter; a feedback terminal coupled to receive the feedback voltage; a depletion-type high-voltage first NMOS transistor having its drain connected to the input detection terminal and its gate connected to its source; an AC voltage detection circuit configured to detect an amplitude of the AC voltage based on a current that flows through the first NMOS transistor; a starter circuit arranged between the input detection terminal and the power supply terminal, and configured to charge the capacitor connected to the power supply terminal using the first rectified voltage in a startup operation of the AC/DC converter; and a driving circuit configured to receive a voltage at the power supply terminal as its operating voltage, and to drive a switching transistor of the DC/DC converter according to the feedback voltage, and wherein the control circuit is monolithically integrated on a single semiconductor substrate. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A control circuit used for an AC/DC converter configured to convert an AC voltage into a first DC voltage, wherein the AC/DC converter comprises:
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a first rectifier circuit configured to rectify and smooth the AC voltage so as to convert the AC voltage into a second DC voltage; an insulating DC/DC converter configured to step up or otherwise step down the second DC voltage; and a feedback circuit configured to generate a feedback voltage that corresponds to the first DC voltage, wherein the control circuit comprises; an input detection terminal via which a first rectified voltage obtained by rectifying the AC voltage is input; a power supply terminal connected to an external capacitor, and configured to receive a third DC voltage generated on a primary side of a transformer of the DC/DC converter in an operating state of the DC/DC converter; a feedback terminal coupled to receive the feedback voltage; a first NMOS transistor configured as a depletion-type high-voltage transistor having its drain connected to the input detection terminal and its gate connected to its source; an AC voltage detection circuit comprising a first resistor and a second resistor arranged in series between the source of the first NMOS transistor and a ground line, and configured to detect the amplitude of the AC voltage based on a second rectified voltage that develops at a connection node that connects the first resistor and the second resistor; a starter circuit arranged between the input detection terminal and the power supply terminal, and comprising a path which allows the capacitor connected to the power supply terminal to be charged using the first rectified voltage; and a driving circuit configured to receive a voltage at the power supply terminal as its operating voltage, and to drive a switching transistor of the DC/DC converter according to the feedback voltage, and wherein the control circuit is monolithically integrated on a single semiconductor substrate. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32)
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Specification