Off time control method for switching regulator
First Claim
Patent Images
1. A switching regulator using off time control, comprising:
- a switch; and
a control circuit, controlling the on and off of said switch;
wherein said control circuit compares a current flowing through said switch with a current threshold and turns off said switch when the current flowing through said switch is larger than said current threshold, said control circuit further determines an off time of said switch based on the magnitude of a load; and
said current threshold varies along with the load during light load and is maintained constant during heavy load, wherein during light load said current threshold is increased and decreased along with the load;
a voltage feedback circuit, sensing an output voltage of said switching regulator and generating a feedback signal accordingly; and
a current sensing circuit, electrically coupled to said switch, sensing the current flowing through said switch and generating a current sensing signal representative of it;
wherein said control circuit comprises a threshold adjusting circuit which is electrically coupled to said voltage feedback circuit to receive said feedback signal and generate said current threshold accordingly; and
said control circuit compares said current sensing signal with said current threshold and turns off said switch based on the comparison resultwherein the threshold adjusting circuit comprises;
a variable threshold generating circuit, electrically coupled to said voltage feedback circuit, receiving said feedback signal and generating a variable threshold accordingly, wherein said variable threshold is increased and decreased along with the load; and
a threshold comparison circuit, electrically coupled to said variable threshold generating circuit, comparing said variable threshold with a constant threshold and outputting the smaller one of said variable threshold and said constant threshold as said current threshold.
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Abstract
The present invention provides an off time control method and switching regulator using it. The current flowing through a switch is compared with a current threshold, and the switch is turned off if the current flowing through the switch is larger than the current threshold. The off time of the switch is determined by the load. The current threshold is variable at light load to prevent generating the audible noise and improve the whole efficiency.
18 Citations
8 Claims
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1. A switching regulator using off time control, comprising:
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a switch; and a control circuit, controlling the on and off of said switch;
wherein said control circuit compares a current flowing through said switch with a current threshold and turns off said switch when the current flowing through said switch is larger than said current threshold, said control circuit further determines an off time of said switch based on the magnitude of a load; and
said current threshold varies along with the load during light load and is maintained constant during heavy load, wherein during light load said current threshold is increased and decreased along with the load;a voltage feedback circuit, sensing an output voltage of said switching regulator and generating a feedback signal accordingly; and a current sensing circuit, electrically coupled to said switch, sensing the current flowing through said switch and generating a current sensing signal representative of it;
wherein said control circuit comprises a threshold adjusting circuit which is electrically coupled to said voltage feedback circuit to receive said feedback signal and generate said current threshold accordingly; and
said control circuit compares said current sensing signal with said current threshold and turns off said switch based on the comparison resultwherein the threshold adjusting circuit comprises; a variable threshold generating circuit, electrically coupled to said voltage feedback circuit, receiving said feedback signal and generating a variable threshold accordingly, wherein said variable threshold is increased and decreased along with the load; and a threshold comparison circuit, electrically coupled to said variable threshold generating circuit, comparing said variable threshold with a constant threshold and outputting the smaller one of said variable threshold and said constant threshold as said current threshold. - View Dependent Claims (2, 3, 4, 5, 6)
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7. An off time control method, comprising:
- comparing a current flowing through a switch with a current threshold, and turning off said switch if the current flowing through said switch is larger than said current threshold;
determining the an off time of said switch based on a load; and
varying said current threshold along with the load during light load and maintaining said current threshold constant during heavy load, wherein during light load said current threshold is increased and decreased along with the load; and
sensing the an output voltage of said a switching regulator and generating a feedback signal accordingly;
sensing the current flowing through said switch and generating a current sensing signal representative of it;
generating said current threshold according to said feedback signal; and
comparing said current sensing signal with said current threshold and turning off said switch based on the comparison result; and
generating a variable threshold according to said feedback signal, wherein said variable threshold is increased and decreased along with the load;comparing said variable threshold with a constant threshold and using the smaller one of said variable threshold and said constant threshold as said current threshold. - View Dependent Claims (8)
- comparing a current flowing through a switch with a current threshold, and turning off said switch if the current flowing through said switch is larger than said current threshold;
Specification