LOAD DETECTING CIRCUITS AND THE METHOD THEREOF
First Claim
1. A no-load detecting circuit for a switching mode power supply, comprising:
- a variable resistance circuit coupled between the switching mode power supply and a load of the switching mode power supply, wherein an equivalent resistance of the variable resistance circuit will vary depending on the status of the load of the switching mode power supply; and
a first comparison circuit coupled to the variable resistance circuit to receive a voltage across the variable resistance circuit, wherein based on the comparison of the voltage across the variable resistance circuit and a first threshold, the first comparison circuit generates a no-load detecting signal indicative of the load status.
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Abstract
A no-load detecting circuit and the method thereof are disclosed. The no-load detecting circuit may be applied in switching mode power supplies or other circuits. The no-load detecting circuit comprises: a variable resistance circuit coupled in series to a load of the switching mode power supply; and a first comparison circuit coupled to the variable resistance circuit to receive the voltage across the variable resistance circuit, wherein based on the comparison of the voltage across the variable resistance circuit and a first threshold, the first comparison circuit generates a no-load detecting signal indicative of the load status; wherein the equivalent resistance of the variable resistance circuit varies based on the varying of the load of the switching mode power supply.
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Citations
19 Claims
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1. A no-load detecting circuit for a switching mode power supply, comprising:
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a variable resistance circuit coupled between the switching mode power supply and a load of the switching mode power supply, wherein an equivalent resistance of the variable resistance circuit will vary depending on the status of the load of the switching mode power supply; and a first comparison circuit coupled to the variable resistance circuit to receive a voltage across the variable resistance circuit, wherein based on the comparison of the voltage across the variable resistance circuit and a first threshold, the first comparison circuit generates a no-load detecting signal indicative of the load status. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A load detecting circuit for a switching mode power supply configured to supply power to a load, wherein the switching mode power supply comprises a switching circuit, and wherein the load detecting circuit comprises:
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a no-load detecting circuit coupled to the load to detect the load status and to generate a no-load detecting signal indicative of the load status; and a reload detecting circuit configured to supply a current to the load when the no-load detecting signal indicates the no-load status, and generates a reload determining signal indicating whether the switching circuit is reloaded based on the comparison of the voltage across the load and a third threshold;
whereinthe switching circuit is shut down when the no-load detecting signal indicates the no-load status, and is restarted when the reload determining signal indicates the reload status. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15)
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16. A load detecting method for a switching mode power supply which provides power to a load, wherein the load detecting method comprises:
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coupling a first transistor to the load; coupling a second transistor in parallel to the first transistor; comparing a drain-source voltage of the first transistor to a second threshold to determine the load status; turning ON the first transistor and the second transistor when the load is light; and turning ON the first transistor and turning OFF the second transistor when the load is heavy. - View Dependent Claims (17, 18, 19)
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Specification