Step-down type switching regulator
First Claim
1. A control circuit for controlling a synchronous rectifier step-down switching regulator comprising:
- an output stage which includes a switching transistor and a synchronous rectifier transistor connected in series, and which supplies a switching voltage at a connection node between said two transistors to a switching regulator output circuit connected as an external component to said control circuit;
a pulse signal generating circuit which generates a pulse signal having a duty ratio controlled such that the output voltage of said switching regulator approaches a predetermined reference voltage;
a driver circuit which generates first and second gate voltages, which are to be applied to the gates of said switching transistor and said synchronous rectifier transistor, based upon the pulse signal; and
a light-load detection circuit which compares the switching voltage with a threshold voltage that is synchronous with the second gate voltage, and that is in the high-level state in a period when said synchronous rectifier transistor is to be turned off and in the low-level state in a period when said synchronous rectifier transistor is to be turned on, and which is configured such that, when the switching voltage is greater than the threshold voltage, said light-load detection circuit outputs a light-load detection signal at a predetermined level,wherein, upon reception of the light-load detection signal at the aforementioned predetermined level from said light-load detection circuit, said driver circuit controls the second gate voltage so as to forcibly turn off said synchronous rectifier transistor.
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Accused Products
Abstract
A pulse signal generating circuit generates a pulse signal having a duty ratio controlled such that the output voltage approaches a reference voltage. A driver circuit generates first and second gate voltages, which are to be respectively applied to the gates of a switching transistor and a synchronous rectifier transistor, based upon the pulse signal. A threshold voltage generating unit generates a threshold voltage which is synchronous with the second gate voltage, and which is in the high-level state during a period when the synchronous rectifier transistor is to be turned off and in the low-level state during a period when the synchronous rectifier transistor is to be turned on. A light-load detection comparator compares a switching voltage with the threshold voltage, and outputs a light-load detection signal.
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Citations
10 Claims
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1. A control circuit for controlling a synchronous rectifier step-down switching regulator comprising:
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an output stage which includes a switching transistor and a synchronous rectifier transistor connected in series, and which supplies a switching voltage at a connection node between said two transistors to a switching regulator output circuit connected as an external component to said control circuit; a pulse signal generating circuit which generates a pulse signal having a duty ratio controlled such that the output voltage of said switching regulator approaches a predetermined reference voltage; a driver circuit which generates first and second gate voltages, which are to be applied to the gates of said switching transistor and said synchronous rectifier transistor, based upon the pulse signal; and a light-load detection circuit which compares the switching voltage with a threshold voltage that is synchronous with the second gate voltage, and that is in the high-level state in a period when said synchronous rectifier transistor is to be turned off and in the low-level state in a period when said synchronous rectifier transistor is to be turned on, and which is configured such that, when the switching voltage is greater than the threshold voltage, said light-load detection circuit outputs a light-load detection signal at a predetermined level, wherein, upon reception of the light-load detection signal at the aforementioned predetermined level from said light-load detection circuit, said driver circuit controls the second gate voltage so as to forcibly turn off said synchronous rectifier transistor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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Specification