Control circuit for a switching DC-DC power converter including a controlled magnetic core flux resetting technique for output regulation
First Claim
1. A self-oscillating DC-DC power converter comprising:
- input means for accepting a DC voltage source;
a power transformer, responsive to the input means, having a first primary winding, a second primary winding, and a first secondary winding, wherein the first primary winding has a first terminal connected to the input means, and wherein the secondary winding has a first terminal connected to an output means;
a switch drive, operatively connected to the input means, the first primary winding and the second primary winding;
a first switch means, responsive to the switch drive, operatively connected to a second terminal of the first primary winding, for alternately and repeatedly applying the input means DC voltage to the first primary winding, the switch means controlling the on and off time of the power transformer corresponding to the on and off time of the switch means;
a regulator, connected to a second terminal of the first secondary winding, for regulating the output voltage of the power converter, wherein the regulator controls the reset voltage produced by the first secondary winding during the off time of the switch means, the regulator controlling the magnetic flux reset time of the power transformer by controlling the off time of the switch means;
output means, responsive to the regulator, for providing a regulated DC voltage at the output of the power converter.
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Accused Products
Abstract
A DC-DC power converter having a power transformer primary winding and a secondary winding producing a regulated output using a control technique and circuit to control the magnetic flux reset time of the core of the power transformer. The control circuit for the power converter provides control of the on and off time of the power transformer by controlling the magnetic flux reset voltage produced on the secondary winding, thereby controlling the duty cycle of the power transformer, and thereby regulating the output of the power transformer. Because control of the power transformer is accomplished by controlling the secondary winding reset voltage, input-to-output isolation and improved converter stability is provided. Minor variations to the input section of the DC-DC converter allows for a wide range of input voltages. Minor variations to the control circuit configuration provide the capability for short-circuit protection and inrush current limitation.
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Citations
40 Claims
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1. A self-oscillating DC-DC power converter comprising:
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input means for accepting a DC voltage source; a power transformer, responsive to the input means, having a first primary winding, a second primary winding, and a first secondary winding, wherein the first primary winding has a first terminal connected to the input means, and wherein the secondary winding has a first terminal connected to an output means; a switch drive, operatively connected to the input means, the first primary winding and the second primary winding; a first switch means, responsive to the switch drive, operatively connected to a second terminal of the first primary winding, for alternately and repeatedly applying the input means DC voltage to the first primary winding, the switch means controlling the on and off time of the power transformer corresponding to the on and off time of the switch means; a regulator, connected to a second terminal of the first secondary winding, for regulating the output voltage of the power converter, wherein the regulator controls the reset voltage produced by the first secondary winding during the off time of the switch means, the regulator controlling the magnetic flux reset time of the power transformer by controlling the off time of the switch means; output means, responsive to the regulator, for providing a regulated DC voltage at the output of the power converter. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A short-circuit protection circuit for a self-oscillating DC-DC power converter, comprising:
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a power transformer having a primary winding; a first secondary winding for generating an output voltage; an output means; an input switching means for controlling the switching frequency of the power transformer; and a second secondary winding responsive to the primary winding, wherein the second secondary winding controls the reset voltage produced by the first secondary winding during the off time of the input switching means whenever the output voltage decreases below a predetermined voltage level due to the overloading of the output means, the second secondary winding controlling the magnetic flux reset time of the power transformer by controlling the on and off time of the input switching means. - View Dependent Claims (18, 19, 20)
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21. A control circuit for a self-oscillating DC-DC power converter, the converter including a power transformer having a first primary winding, a second primary winding, and a secondary winding for generating an output voltage, the converter having an input switching means for controlling the switching frequency of the power transformer, the secondary winding producing a reset voltage during the off time of the input switching means, the control circuit controlling the on and off time of the power transformer by limiting the secondary winding reset voltage to a predetermined level, comprising:
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a reset capacitor having a first terminal connected to a first terminal of the secondary winding, the reset capacitor limiting the reset voltage produced by the secondary winding to a predetermined level; a rectifying diode having a first terminal connected to a second terminal of the secondary winding and having a second terminal connected to a second terminal of the reset capacitor; a reference diode, having a first terminal connected to the first terminal of the secondary winding; two voltage divider resistors connected in series with the reference diode; a switch means, operatively connected to the reset capacitor, the rectifying diode, the reference diode and the voltage divider resistors, the switch means discharging the voltage stored by the reset capacitor during the off time of the input switching means.
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22. A self-oscillating DC-DC power converter comprising:
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an input receiving a voltage signal; an output providing a DC voltage signal; a power transformer, responsive to the input voltage signal, having a first primary winding and a first secondary winding, wherein the first primary winding receives the input voltage signal, and the first secondary winding provides an output voltage to the output; a switch operably engaged with the transformer so that when the switch is in an on state, current flows through the first primary winding of the transformer; a switch drive which induces the switch to move between an on and an off state wherein the switch drive induces the switch to move from the off state to the on state when the power transformer has been reset; and a regulator, connected to the first secondary winding, which controls the reset voltage produced by the first secondary winding during the time when the switch is in an off state and thereby controls the magnetic flux reset time of the power transformer and the time the switch is in the off state. - View Dependent Claims (23, 24, 25, 26, 27, 28)
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29. A self-oscillating DC-DC power converter comprising:
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an input receiving a DC voltage; an output providing a DC voltage; a power transformer, responsive to the input DC voltage source, having a first primary winding and a first secondary winding, wherein the first primary winding receives the input DC voltage through a first terminal, and the first secondary winding provides an output voltage to the output through a first terminal; a switch operably engaged with a second terminal of the transformer so that when the switch is in an on state, current flows through the first primary winding of the transformer; a switch drive which induces the switch to move between an on and an off state wherein the switch drive induces the switch to move from the off state to the on state when the power transformer has been reset; and a control circuit, connected to the first terminal of the first primary winding, which controls the reset voltage produced by the first primary winding during the time when the switch is in an off state and thereby controls the magnetic flux reset time of the power transformer and the time the switch is in the off state. - View Dependent Claims (30, 31)
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32. A self-oscillating DC-DC power converter comprising:
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an input receiving a DC voltage; an output providing a DC voltage; a power transformer, responsive to the input DC voltage source, having a first primary winding and a first secondary winding, wherein the first primary winding receives the input DC voltage through a first terminal, and the first secondary winding provides an output voltage to the output through a first terminal; a switch operably engaged with a second terminal of the transformer so that when the switch is in an on state, current flows through the first primary winding of the transformer; a switch drive which induces the switch to move between an on and an off state wherein the switch drive induces the switch to move from the off state to the on state when the power transformer has been reset; and a control circuit, connected to a first terminal of the second secondary winding of the power transformer, which controls the reset voltage produced by the second secondary winding during the time when the switch is in an off state and thereby controls the magnetic flux reset time of the power transformer and the time the switch is in the off state. - View Dependent Claims (33, 34)
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35. A control circuit for a self-oscillating DC-DC power converter, the converter including a power transformer having a primary winding and a secondary winding, the converter having an input switching means for controlling the switching frequency of the power transformer, the secondary winding producing a reset voltage during the off time of the input switching means, the control circuit controlling the on and off time of the power transformer by limiting the secondary winding reset voltage to a predetermined level, comprising:
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a reset capacitor having a first terminal connected to a first terminal of the secondary winding, the reset capacitor limiting the reset voltage produced by the secondary winding to a predetermined level; a rectifying diode having a first terminal connected to a second terminal of the secondary winding and having a second terminal connected to a second terminal of the reset capacitor; a reference diode, having a first terminal connected to the first terminal of the secondary winding; two voltage divider resistors connected in series with the reference diode; a switch means, operatively connected to the reset capacitor, the rectifying diode, the reference diode and the voltage divider resistors, the switch means discharging the voltage stored by the reset capacitor during the off time of the input switching means.
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36. A method for regulating the output of a self-oscillating DC-DC power converter, the converter including a power transformer having a primary winding and a secondary winding, the converter having an input switching means for controlling the switching frequency of the power transformer, the secondary winding producing a reset voltage during the off time of the input switching means, the regulation method controlling the on and off time of the input switching means, comprising:
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limiting the reset voltage produced by the secondary winding to a predetermined clamped voltage level, thereby varying the magnetic flux reset time of the power transformer; and discharging the clamped reset voltage at a rate corresponding to the off time of the input switching means.
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37. An inrush current limiting circuit for a self-oscillating DC-DC power converter, comprising:
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a power transformer having a primary winding; a first secondary winding for generating an output voltage; an input means; an input switching means for controlling the switching frequency of the power transformer; and a second secondary winding responsive to the primary winding, wherein the second secondary winding clamps the reset voltage produced by the first secondary winding to a predetermined voltage level during the off time of the input switching means when an input voltage is initially applied to the input means, the second secondary winding controlling the inrush current of the power transformer during the initial application of an input voltage to the input means. - View Dependent Claims (38, 39, 40)
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Specification