Method and apparatus for multiple output regulation in a step-down switching regulator
DCFirst Claim
1. A switching regulator comprising:
- a magnetic storage device having at least a first output and a second output;
a current sensing device for detecting a current through a primary winding of said magnetic storage device, said current sensing device coupled to said primary winding and to a control circuitry;
a first switching device for connecting an input side of said primary winding to a first input voltage, said first switching device coupled to said input side of said primary winding, to said control circuitry and to said first input voltage, said first switching device controlled by said control circuitry;
a second switching device for connecting an input side of said primary winding to a second input voltage, said second switching device coupled to said input side of said primary winding, to said control circuitry and to said second input voltage, said second switching device controlled by said control circuitry;
said first output of said magnetic storage device coupled to said primary winding and to said control circuitry;
said second output of said magnetic storage device coupled to said control circuitry; and
said control circuitry comprising;
a first comparator for detecting whether said current through said primary winding is greater than a limit value, said first comparator coupled to said current sensing device, to said limit value, and to said second switching device;
a second comparator for detecting loss of regulation in said second output, said second comparator coupled to said second output and to said second switching device;
a switch logic circuitry for allowing only one of said first switching device and said second switching device to turn on at a time, said switch logic circuitry coupled to said second comparator, to said first comparator, to said first switching device and to said second switching device.
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Abstract
A step-down switching regulator of the present invention includes (1) a magnetic storage device having at least one primary output and one secondary output, (2) a current sensing device for detecting current through a primary winding of the magnetic storage device, (3) a first switch, (4) a second switch, (5) a first comparator for detecting whether the current through the primary winding is greater than a limit value, (6) a second comparator for detecting loss of regulation in the secondary output, and (7) a switch logic circuitry for allowing only one of the first switch or the second switch to turn on at a time. When the primary output is out of regulation, the first switch turns on to deliver power to the primary output. When the secondary output is out of regulation, one of two methods can be used to supply power to the secondary output. A first method turns on the first switch for a short time, and then the second switch turns on to deliver power to the secondary output. A second method turns on the second switch without first turning on the first switch. In either methods, the second switch can be turned off at the end of a pre-determined time period, at the end of a clock cycle, when the current through the primary winding exceeds a pre-determined limit value, or when the current through the primary winding is substantially zero.
114 Citations
30 Claims
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1. A switching regulator comprising:
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a magnetic storage device having at least a first output and a second output; a current sensing device for detecting a current through a primary winding of said magnetic storage device, said current sensing device coupled to said primary winding and to a control circuitry; a first switching device for connecting an input side of said primary winding to a first input voltage, said first switching device coupled to said input side of said primary winding, to said control circuitry and to said first input voltage, said first switching device controlled by said control circuitry; a second switching device for connecting an input side of said primary winding to a second input voltage, said second switching device coupled to said input side of said primary winding, to said control circuitry and to said second input voltage, said second switching device controlled by said control circuitry; said first output of said magnetic storage device coupled to said primary winding and to said control circuitry; said second output of said magnetic storage device coupled to said control circuitry; and said control circuitry comprising; a first comparator for detecting whether said current through said primary winding is greater than a limit value, said first comparator coupled to said current sensing device, to said limit value, and to said second switching device; a second comparator for detecting loss of regulation in said second output, said second comparator coupled to said second output and to said second switching device; a switch logic circuitry for allowing only one of said first switching device and said second switching device to turn on at a time, said switch logic circuitry coupled to said second comparator, to said first comparator, to said first switching device and to said second switching device. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. In a switching regulator having a magnetic storage device including a first output and a second output, a first switching device coupled to a primary winding of said magnetic storage device, a second switch device coupled to said primary winding of said magnetic storage device, a control circuitry coupled to said first output, to said second output, to said first switching device and to said second switching device, a current sensing device measuring a current through said primary winding of said magnetic storage device, said current sensing device coupled to said primary winding and to said control circuitry, a method of regulating output voltages of said switching regulator comprising the steps of:
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detecting a voltage of said first output being in regulation; detecting a voltage of said second output being out of regulation by comparing the voltage of said second output to a first reference voltage; turning on said first switching device; turning off said first switching device; turning on said second switching device; turning off said second switching device when one of a first event, a second event, a third event and a fourth event occurs; wherein said first event is said current becoming substantially zero; wherein said second event is said current exceeding a pre-determined limit value; wherein said third event is an end of a clock cycle; wherein said fourth event is an end of a pre-determined time period.
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19. In a switching regulator having a magnetic storage device including a first output and a second output, a first switching device coupled to a primary winding of said magnetic storage device, a second switching device coupled to said primary winding of said magnetic storage device, a control circuitry coupled to said first output, to said second output, to said first switching device and to said second switching device, a current sensing device for sensing a current through said primary winding of said magnetic storage device, said current sensing device coupled to said primary winding and to said control circuitry, a method of regulating output voltages of said switching regulator comprising the steps of:
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detecting a voltage of said first output being in regulation; detecting a voltage of said second output being out of regulation by comparing the voltage of said second output to a first reference voltage; turning on said second switching device; turning off said second switching device when one of a first event, a second event, a third event and a fourth event occurs; wherein said first event is said current becoming substantially zero; wherein said second event is said current exceeding a pre-determined limit value; wherein said third event is an end of a clock cycle; wherein said fourth event is an end of a pre-determined time period. - View Dependent Claims (20, 21, 22, 23)
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24. A method of regulating a switching regulator comprising the steps of:
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changing a current in a first direction through a primary winding of a magnetic storage device until a first output coupled to said primary winding is in regulation; changing said current in a second direction through said primary winding of said magnetic storage device to supply power to a second output coupled to said magnetic storage device until one of a first event, a second event, a third event and a fourth event occurs; wherein said first event is said current becoming substantially zero; wherein said second event is said current exceeding a pre-determined limit value; wherein said third event is an end of a clock cycle; wherein said fourth event is an end of a pre-determined time period.
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25. A method of operating a switching regulator having a transformer with a primary and at least one secondary winding and having a first regulator output coupled to one end of the primary winding and a second regulator output coupled to the secondary winding, a second end of the primary winding being coupled to switches for controllably coupling the second end of the primary winding to a first supply voltage and to a second supply voltage, comprising the steps of:
controlling the switches to provide currents through the primary of the transformer to maintain the first regulator output above a first predetermined voltage; and
, controlling the switches to provide time rates of change of currents through the primary of the transformer to maintain the second regulator output above a second predetermined voltage.- View Dependent Claims (26)
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27. A switching regulator having a transformer with a primary and at least one secondary winding and having a first regulator output coupled to one end of the primary winding and a second regulator output coupled to the secondary winding, a second end of the primary winding being coupled to switches for controllably coupling the second end of the primary winding to a first supply voltage and to a second supply voltage, comprising:
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a controller for; controlling the switches to provide currents through the primary of the transformer to maintain the first regulator output above a first predetermined voltage; and
,controlling the switches to provide time rates of change of currents through the primary of the transformer to maintain the second regulator output above a second predetermined voltage. - View Dependent Claims (28)
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29. A controller for a switching regulator having a transformer with a primary and at least one secondary winding and having a first regulator output coupled to one end of the primary winding and a second regulator output coupled to the secondary winding, a second end of the primary winding being coupled to switches for controllably coupling the second end of the primary winding to a first supply voltage and to a second supply voltage, the controller comprising:
circuitry for controlling the switches to provide currents through the primary of the transformer to maintain the first regulator output above a first predetermined voltage; and
, for controlling the switches to provide time rates of change of currents through the primary of the transformer to maintain the second regulator output above a second predetermined voltage.- View Dependent Claims (30)
Specification