Three-terminal switched mode power supply integrated circuit
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1. A switched-mode power supply chip having exactly three electrical connections, comprising:
- a first electrical connection terminal providing for a connection to a first end of a primary winding of a transformer with a second end of said primary winding connected to a source of direct current (DC) power;
a second electrical connection terminal providing for a ground reference for said source of DC power;
a third electrical connection terminal providing for a connection to a source of feedback current derived from a secondary winding of said transformer with a second end of said secondary winding connected to said ground reference for said source of DC power, wherein a combined feedback signal (Ifb) and internal low voltage supply current (Is) may be accepted on a single pin of said chip, such that said low voltage supply current may provide the operating power necessary for voltage regulation after a startup phase and during an operation phase of said chip;
a junction-type field effect transistor (JFET) having a drain electrode connected to the first electrical connection terminal, a gate electrode connected to the second electrical connection terminal, and a source electrode for providing a bias voltage that is reduced substantially from a voltage appearing at the first electrical connection terminal;
a metal oxide semiconductor field effect transistor (MOSFET) having a drain electrode connected to said source electrode of the JFET and thereby placing the MOSFET and JFET in series connection, a gate electrode for controlling a switching current through both the JFET and MOSFET in series, and a source electrode connected to the second electrical connection terminal;
voltage regulation means having an input connected to the third electrical connection terminal and an output connected to said gate of the MOSFET and having a bias voltage power supply connection to said source electrode of the JFET for switching the MOSFET and JFET on and off according to a feedback current received at the third electrical connection terminal, wherein a voltage output by said transformer is thereby regulated; and
input means connected to the third electrical connection terminal for accepting a combined feedback signal (Ifb) and internal low voltage supply current (Is) on a single pin, wherein said low voltage supply current provides operating power for the voltage regulation means after said startup and during said operation of said chip.
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Abstract
An embodiment of the present invention is a three-terminal switched mode power supply chip with a signal terminal for accepting a combination of a feedback control signal and bias supply voltage to operate the chip. A feedback extraction circuit separates the feedback signal from the power supply voltage within the chip by sensing the excess current flowing through a shunt regulator.
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11 Claims
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1. A switched-mode power supply chip having exactly three electrical connections, comprising:
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a first electrical connection terminal providing for a connection to a first end of a primary winding of a transformer with a second end of said primary winding connected to a source of direct current (DC) power; a second electrical connection terminal providing for a ground reference for said source of DC power; a third electrical connection terminal providing for a connection to a source of feedback current derived from a secondary winding of said transformer with a second end of said secondary winding connected to said ground reference for said source of DC power, wherein a combined feedback signal (Ifb) and internal low voltage supply current (Is) may be accepted on a single pin of said chip, such that said low voltage supply current may provide the operating power necessary for voltage regulation after a startup phase and during an operation phase of said chip; a junction-type field effect transistor (JFET) having a drain electrode connected to the first electrical connection terminal, a gate electrode connected to the second electrical connection terminal, and a source electrode for providing a bias voltage that is reduced substantially from a voltage appearing at the first electrical connection terminal; a metal oxide semiconductor field effect transistor (MOSFET) having a drain electrode connected to said source electrode of the JFET and thereby placing the MOSFET and JFET in series connection, a gate electrode for controlling a switching current through both the JFET and MOSFET in series, and a source electrode connected to the second electrical connection terminal; voltage regulation means having an input connected to the third electrical connection terminal and an output connected to said gate of the MOSFET and having a bias voltage power supply connection to said source electrode of the JFET for switching the MOSFET and JFET on and off according to a feedback current received at the third electrical connection terminal, wherein a voltage output by said transformer is thereby regulated; and input means connected to the third electrical connection terminal for accepting a combined feedback signal (Ifb) and internal low voltage supply current (Is) on a single pin, wherein said low voltage supply current provides operating power for the voltage regulation means after said startup and during said operation of said chip.
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2. A semiconductor chip having as few as three external electrical connections, comprising:
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a first electrical connection terminal providing for a pulse-width modulated output relative to an internal ground reference; a second electrical connection terminal providing for connection of said internal ground reference to an external ground reference; a third electrical connection terminal providing for a connection to a combined source of bias supply power and a feedback current that is controlled in part by said pulse-width modulated output; voltage regulation means having an input connected to the third electrical connection terminal and an output connected to control the on and off duty cycle of an output transistor connected between the first and second electrical connection terminals according to said feedback current received at the third electrical connection terminal, wherein an output of a circuit including said chip is thereby regulated; and input means connected to the third electrical connection terminal for accepting a combined feedback signal (Ifb) and internal low voltage supply current (Is) on a single pin for providing operating power with said low voltage supply current to the voltage regulation means after a startup and during operation of said chip. - View Dependent Claims (3)
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4. A switched-mode power supply chip having as few as three electrical connections, comprising:
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a first electrical connection terminal providing for a connection to a first end of a primary winding of a transformer with a second end of said primary winding connected to receive a source of direct current (DC) power; a second electrical connection terminal providing for a ground reference for said source of DC power; a third electrical connection terminal providing for a connection to a sourced of feedback current derived from a secondary winding of said transformer with a second end of said secondary winding connected to said ground reference for said source of DC power; voltage regulation means having an input connected to the third electrical connection terminal and an output connected to control an output transistor connected between the first and second electrical connection terminals on and off according to a feedback current received a the third electrical connection terminal, wherein a voltage output by said transformer is thereby regulated and the voltage regulation means is provided with a bias voltage power supply current during operation of said chip; and input means connected to the third electrical connection terminal for accepting a combined feedback signal (Ifb) and internal low voltage supply current (Is) on a single pin, wherein said low voltage supply current provides operating power for the voltage regulation means after said startup and during said operation of said chip. - View Dependent Claims (5, 6, 7, 8, 9)
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10. A power supply, comprising:
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a three-terminal switched-mode power supply chip, including; a first electrical connection terminal providing for a connection to a first end of a primary winding of a transformer with a second end of said primary winding connected to receive a source of direct current (DC) power; a second electrical connection terminal providing for a ground reference for said source of DC power; a third electrical connection terminal providing for a connection to a source of feedback current derived from a secondary winding of said transformer with a second end of said secondary winding connected to said ground reference for said source of DC power; voltage regulation means having an input connected to the third electrical connection terminal and an output connected to control an output transistor connected between the first and second electrical connection terminals on and off according to a feedback current received at the third electrical connection terminal for regulating a voltage output by said transformer and for providing the voltage regulation means with a bias voltage power supply current during operation of said chip; and input means connected to the third electrical connection terminal for accepting a combined feedback signal (Ifb) and internal low voltage supply current (Is) on a single pin, wherein said low voltage supply current provides operating power for the voltage regulation means after said startup and during said operation of said chip; a transformer, including a primary winding and a secondary winding, connected at a first end of said primary winding to said first electrical connection terminal of the switched-mode power supply chip, and connected at a second end of said primary winding to receive a source of direct current (DC) power; DC output means for converting an output of a said secondary winding of the transformer to a regulated DC output voltage; and bias means for converting a voltage induced in said secondary winding of the transformer to a bias supply and connected to said third electrical connection terminal to power the switched-mode power supply chip. - View Dependent Claims (11)
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Specification