Switching power converter with current sensing transformer auxiliary power supply
First Claim
1. A switched-power circuit, comprising:
- a magnetic coupling element for coupling an input of the switched-power circuit to an output of the switched-power circuit and having at least one winding;
a switching circuit for controlling energizing of a primary winding of the magnetic coupling element from an input voltage source connected to the input of the switched-power circuit;
a current sensing transformer having a primary winding coupled in series with the at least one winding of the magnetic coupling element and the switching circuit, and having a secondary winding;
a control circuit for controlling switching of the switching circuit;
a current sensing circuit coupled to the secondary winding of the current sensing transformer for providing an indication of a magnitude of current conducted through the at least one winding of the magnetic coupling element; and
an auxiliary power supply having an input coupled to the secondary winding of the current sensing transformer and an output coupled to the control circuit for providing a supply voltage to the control circuit.
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Accused Products
Abstract
A switching power converter having a current sensing transformer providing input to an auxiliary power supply provides efficient current sensing, while reducing the cost of the magnetic coupling element. The auxiliary power supply and current sense circuit both receive input from a secondary winding of a current sensing transformer having a primary winding coupled in series with the converter'"'"'s main magnetic coupling element. To provide accurate sensing, the magnetization the current sensing transformer is accounted for. The magnetization is compensated for in the current sensing result, current sensing is performed during a part of the cycle in which charging of the auxiliary power supply is disabled, or the core of the current sensing transformer is made large, raising its mutual inductance. In another alternative technique, a circuit node can be pre-charged to a value that cancels the offset due to the magnetization current.
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Citations
22 Claims
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1. A switched-power circuit, comprising:
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a magnetic coupling element for coupling an input of the switched-power circuit to an output of the switched-power circuit and having at least one winding; a switching circuit for controlling energizing of a primary winding of the magnetic coupling element from an input voltage source connected to the input of the switched-power circuit; a current sensing transformer having a primary winding coupled in series with the at least one winding of the magnetic coupling element and the switching circuit, and having a secondary winding; a control circuit for controlling switching of the switching circuit; a current sensing circuit coupled to the secondary winding of the current sensing transformer for providing an indication of a magnitude of current conducted through the at least one winding of the magnetic coupling element; and an auxiliary power supply having an input coupled to the secondary winding of the current sensing transformer and an output coupled to the control circuit for providing a supply voltage to the control circuit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method of operating a switched-power circuit, comprising:
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switching an input voltage source across at least one winding of a magnetic coupling element to transfer power to an output of the switched-power circuit; sensing a current flowing through the at least one winding of the magnetic coupling element using a sensing transformer having a primary winding coupled in series with the at least one winding of the magnetic coupling element; and generating an auxiliary power supply from the secondary winding of the current sensing transformer for providing a supply voltage to a control circuit of the switched-power circuit. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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17. An integrated circuit, comprising:
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a switching control circuit for controlling a switch for charging an external magnetic coupling element through at least one primary winding; at least one input terminal for coupling to a secondary winding of a current sensing transformer; a current sensing circuit having an input coupled to the at least one input terminal for providing an indication of a magnitude of current conducted through the at least one winding of the external magnetic coupling element; and an auxiliary power supply having an input coupled to the at least one input terminal and an output coupled to the switching control circuit for providing a supply voltage to the control circuit. - View Dependent Claims (18, 19, 20, 21, 22)
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Specification