Off-line bootstrap startup circuit
First Claim
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1. An off-line bootstrap circuit being responsive to a line voltage for providing a bias voltage to an integrated circuit, the off-line bootstrap circuit comprising:
- a high voltage device having first and second current carrying terminals and a control terminal, said first current carrying terminal of said high voltage device being connected for receiving the line voltage, said second current carrying terminal of said high voltage device being coupled for providing the bias voltage, said high voltage device including,(a) a first transistor for extending a range of the bias voltage, said first transistor having first and second current carrying electrodes and a control electrode, said second current carrying electrode coupled for providing the bias voltage, said control electrode of said first transistor coupled to said control terminal of said high voltage device, and(b) a second transistor having first and second current carrying electrodes and a control electrode, said first current carrying electrode connected for receiving the line voltage, said second current carrying electrode connected to said first current carrying electrode of said first transistor, said control electrode of said second transistor coupled to a first supply voltage terminal wherein said first current carrying electrode of said first transistor is merged in a common region with said second current carrying electrode of said second transistor;
control means having an output coupled to said control terminal of said high voltage device and responsive to a control signal for rendering said high voltage device inoperative when the bias voltage has exceeded a predetermined threshold; and
a switching transistor having a first electrode coupled to said output of said control means for receiving a switching signal, a second electrode coupled to said first supply voltage terminal, and a third electrode connected to the line voltage.
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Abstract
A novel off-line bootstrap startup circuit (10) including a high voltage device (100) for providing an initial bias voltage to an integrated circuit (IC) is provided. The high voltage device includes an NMOS transistor (102) having a high source to ground breakdown voltage thereby extending a bias voltage range provided to the IC. This bias voltage range may be needed to support large comparator (303) hysteresis and allow for an unregulated bias voltage. The bootstrap startup circuit becomes inoperative when the bias voltage exceeds a predetermined value.
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Citations
18 Claims
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1. An off-line bootstrap circuit being responsive to a line voltage for providing a bias voltage to an integrated circuit, the off-line bootstrap circuit comprising:
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a high voltage device having first and second current carrying terminals and a control terminal, said first current carrying terminal of said high voltage device being connected for receiving the line voltage, said second current carrying terminal of said high voltage device being coupled for providing the bias voltage, said high voltage device including, (a) a first transistor for extending a range of the bias voltage, said first transistor having first and second current carrying electrodes and a control electrode, said second current carrying electrode coupled for providing the bias voltage, said control electrode of said first transistor coupled to said control terminal of said high voltage device, and (b) a second transistor having first and second current carrying electrodes and a control electrode, said first current carrying electrode connected for receiving the line voltage, said second current carrying electrode connected to said first current carrying electrode of said first transistor, said control electrode of said second transistor coupled to a first supply voltage terminal wherein said first current carrying electrode of said first transistor is merged in a common region with said second current carrying electrode of said second transistor; control means having an output coupled to said control terminal of said high voltage device and responsive to a control signal for rendering said high voltage device inoperative when the bias voltage has exceeded a predetermined threshold; and a switching transistor having a first electrode coupled to said output of said control means for receiving a switching signal, a second electrode coupled to said first supply voltage terminal, and a third electrode connected to the line voltage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. An integrated circuit for switching an inductive load, the inductive load coupled between a line voltage and a first pin of the integrated circuit, the integrated circuit comprising:
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a bootstrap circuit connected to the first pin of the integrated circuit for providing an initial bias voltage at a first terminal, wherein said bootstrap circuit includes a high voltage device having first and second current carrying terminals and a control terminal, said first current carrying terminal of said high voltage device being connected to the first pin of the integrated circuit, said second current carrying terminal of said high voltage device being coupled to said first terminal, said high voltage device including, (a) a first transistor for extending a range of said bias voltage, said first transistor having first and second current carrying electrodes and a control electrode, said second current carrying electrode coupled for providing said bias voltage, said control electrode coupled to a control means, (b) a second transistor having first and second current carrying electrodes and a control electrode, said first current carrying electrode connected for receiving the line voltage, said second current carrying electrode connected to said first current carrying electrode of said first transistor, said control electrode of said second transistor coupled to a first supply voltage terminal wherein said first current carrying electrode of said first transistor is merged in a common region with said second current carrying electrode of said second transistor; switching means connected to the first pin of the integrated circuit for alternately switching the inductive load on and off; and first circuit means coupled to said first terminal for turning off said bootstrap circuit and for enabling said switching means when said initial bias voltage appearing at said first terminal exceeds a predetermined threshold, wherein when said bootstrap circuit is turned off a voltage appearing at said first terminal is provided via the inductive load. - View Dependent Claims (13, 14, 15, 16, 17)
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18. An off-line bootstrap circuit being responsive to a line voltage for providing a bias voltage to an integrated circuit, the off-line bootstrap circuit comprising:
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a high voltage device having first and second current carrying terminals and a control terminal, said first current carrying terminal of said high voltage device being connected for receiving the line voltage, said second current carrying terminal of said high voltage device being coupled for providing the bias voltage, said high voltage device including, (a) a first transistor for extending a range of the bias voltage, said first transistor having first and second current carrying electrodes and a control electrode, said second current carrying electrode coupled for providing the bias voltage, said control electrode of said first transistor coupled to said control terminal of said high voltage device, and (b) a second transistor having first and second current carrying electrodes and a control electrode, said first current carrying electrode connected for receiving the line voltage, said second current carrying electrode connected to said first current carrying electrode of said first transistor, said control electrode of said second transistor coupled to a first supply voltage terminal wherein said first current carrying electrode of said first transistor is merged in a common region with said second current carrying electrode of said second transistor; clamping means coupled to said control terminal of said high voltage device for limiting voltage appearing thereat; control means having an output coupled to said control terminal of said high voltage device and responsive to a control signal for rendering said high voltage device inoperative when the bias voltage has exceeded a predetermined threshold; a logic circuit having an output, a first input coupled to said control terminal of said high voltage device, and a second input for receiving an output of a pulse width modulator; and a switching transistor having a first electrode coupled to said output of said logic circuit, a second electrode coupled to said first supply voltage terminal, and a third electrode connected to the line voltage.
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Specification