Apparatus and method for control and driving BJT used as synchronous rectifier
First Claim
1. A control and drive circuit for a BJT rectifier, comprising:
- an input adapted for coupling to a collector and an emitter of a BJT rectifier and configured to comprise a sensing pathway that senses a signal representative of the collector to emitter voltage (VCE) of that BJT rectifier;
an output adapted for coupling to a base of that BJT rectifier;
a drive circuit coupled to said input and said output that produces a base drive current (IB); and
an offset circuit coupled to said drive circuit that provides an offset of a given value (offset value);
said drive circuit being configured to produce a positive base drive current at said output that is proportional to the sensed VCE minus said offset value when the sensed VCE is essentially greater than said offset value, and to produce a negative base drive current at said output when the sensed VCE is essentially less than said offset value; and
said sensing pathway being comprised of sensing pathway components and being configured so as to substantially compensate for component induced variations in sensed VCE due to changes in operating conditions.
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Accused Products
Abstract
A bipolar junction transistor (BJT) used as a synchronous rectifier (SR) that is driven and controlled by an electronic circuit, such that when the collector-emitter voltage (VCE) is above an offset voltage (VOS) the circuit drives the base of the SR BJT with a base current proportional to the difference between VCE and VOS, turning the SR BJT on with a base current proportional to the collector current. When the VCE of the SR BJT falls below VOS the drive circuit turns on a second transistor coupled between the base and collector of the SR BJT to turn the SR BJT rapidly off and maintains it in the off state as the collector voltage reverses. When the VCE of the SR BJT is exceeds a threshold voltage above the normal conduction VCE range, the control circuit increases the base drive current to accelerate the SR BJT turn-on process.
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Citations
26 Claims
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1. A control and drive circuit for a BJT rectifier, comprising:
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an input adapted for coupling to a collector and an emitter of a BJT rectifier and configured to comprise a sensing pathway that senses a signal representative of the collector to emitter voltage (VCE) of that BJT rectifier;
an output adapted for coupling to a base of that BJT rectifier;
a drive circuit coupled to said input and said output that produces a base drive current (IB); and
an offset circuit coupled to said drive circuit that provides an offset of a given value (offset value);
said drive circuit being configured to produce a positive base drive current at said output that is proportional to the sensed VCE minus said offset value when the sensed VCE is essentially greater than said offset value, and to produce a negative base drive current at said output when the sensed VCE is essentially less than said offset value; and
said sensing pathway being comprised of sensing pathway components and being configured so as to substantially compensate for component induced variations in sensed VCE due to changes in operating conditions. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
inducing an imbalance in said sensing pathway;
orinducing a variation in the base drive current produced by said drive circuit that approximates the effect of having an imbalance in said sensing pathway.
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10. The circuit of claim 1, wherein said driving circuit is configured to produce a base drive current approximately equal to zero, when a sensed VCE is approximately equal to said offset value.
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11. The circuit of claim 1, wherein said drive circuit is powered by a single supply voltage.
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12. A control and drive circuit for a BJT rectifier, comprising:
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an input adapted for coupling to a collector and an emitter of a BJT rectifier and configured to comprise a sensing pathway that senses a signal representative of the collector to emitter voltage (VCE) of that BJT rectifier;
an output adapted for coupling to a base of that BJT rectifier;
a drive circuit coupled to said input and output that produces a base drive current (IB); and
an offset circuit coupled to said drive circuit that provides an offset of a given value (offset value);
said drive circuit being configured to produce a positive base drive current at said output when a sensed VCE is approximately greater than said offset value, and to produce a negative base drive current at said output when the sensed VCE is approximately less than said offset value; and
said sensing pathway being configured to compensate for component induced variations in sensed VCE due to changes in operating temperature. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20)
an offset voltage source;
an offset current source;
orcircuitry that provides at least one of the functions of;
inducing an imbalance in said sensing pathway;
orinducing a variation in the base drive current produced by said drive circuit that approximates the effect of having an imbalance in said sensing pathway.
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19. The circuit of claim 12, wherein said driving circuit is configured to produce a base drive current approximately equal to zero, when a sensed VCE is approximately equal to said offset value.
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20. The circuit of claim 12, wherein said drive circuit is powered by a single supply voltage.
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21. A control and drive circuit for a BJT rectifier, comprising:
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an input adapted for coupling to a collector and an emitter of a BJT rectifier and configured to comprise a sensing pathway that senses a signal representative of the collector to emitter voltage (VCE) of that BJT rectifier;
an output adapted for coupling to a base of that BJT rectifier;
a drive circuit coupled to said input and output that produces a base drive current (IB); and
an offset circuit coupled to said drive circuit that provides an offset of a given value (offset value);
said drive circuit being configured to produce a positive base drive current at said output that is proportional to a sensed VCE minus said offset value when the sensed VCE is approximately greater than said offset value, and to produce a negative base drive current at said output when the sensed VCE is approximately less than said offset value. - View Dependent Claims (22, 23, 24, 25, 26)
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Specification