Low forward voltage rectifier

• US 20130107583A1
• Filed: 10/29/2011
• Published: 05/02/2013
• Est. Priority Date: 10/29/2011
• Status: Active Grant

• Current Assignee: Littelfuse Incorporated
• Original Assignee: IXYS Corporation (Littelfuse Incorporated)
• Inventors: Seok, Kyoung Wook
• Granted Patent: US 8,649,199 B2
• Time in Patent Office: Days
• US Class Current: 363/21.12
• CPC Class Codes: H01L 2224/32245 the item being metallic
• CPC Class Codes: H01L 2224/45015 being circular
• CPC Class Codes: H01L 2224/45099 Material
• CPC Class Codes: H01L 2224/48137 the bodies being arranged next to each other, e.g. on a common substrate
• CPC Class Codes: H01L 2224/48195 the item being a discrete passive component
• CPC Class Codes: H01L 2224/48472 the other connecting portion not on the bonding area also being a wedge bond, i.e. wedge-to-wedge
• CPC Class Codes: H01L 2224/4903 Connectors having different sizes, e.g. different diameters
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• CPC Class Codes: H01L 23/3107 the device being completely enclosed
• CPC Class Codes: H01L 23/49562 for devices being provided for in H01L29/00
• CPC Class Codes: H01L 24/32 of an individual layer connector
• CPC Class Codes: H01L 24/48 of an individual wire connector
• CPC Class Codes: H01L 24/49 of a plurality of wire connectors
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/00012 Relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/12032 Schottky diode
• CPC Class Codes: H01L 2924/12036 PN diode
• CPC Class Codes: H01L 2924/1305 Bipolar Junction Transistor [BJT]
• CPC Class Codes: H01L 2924/15747 Copper [Cu] as principal constituent
• CPC Class Codes: H01L 2924/181 : Encapsulation
• CPC Class Codes: H01L 2924/19107 : off-chip wires
• CPC Class Codes: H01L 2924/207 : Diameter ranges
• CPC Class Codes: H02M 1/0048 : Circuits or arrangements for reducing losses using snubbers H02M1/34
• CPC Class Codes: H02M 3/335 : using semiconductor devices only
• CPC Class Codes: H02M 3/33538 : of the forward type H02M3/3353, H02M3/33569 take precedence
• CPC Class Codes: H02M 3/33576 : having at least one active switching element at the secondary side of an isolation transformer
• CPC Class Codes: Y02B 70/10 : Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
• CPC Class Codes: Y10T 29/4913 : Assembling to base an electrical component, e.g., capacitor, etc.

Abstract

A Low Forward Voltage Rectifier (LFVR) includes a bipolar transistor, a parallel diode, and a base current injection circuit disposed in an easy-to-employ two-terminal package. In one example, the transistor is a Reverse Bipolar Junction Transistor (RBJT), the diode is a distributed diode, and the base current injection circuit is a current transformer. Under forward bias conditions (when the voltage from the first package terminal to the second package terminal is positive), the LFVR conducts current at a rated current level with a low forward voltage drop (for example, approximately 0.1 volts). In reverse bias conditions, the LFVR blocks current flow. Using the LFVR in place of a conventional silicon diode rectifier in the secondary of a flyback converter reduces average power dissipation and increases power supply efficiency.

Claims

1. An electronic device comprising:

a current transformer having a first winding and a second winding, the first winding having a first end and a second end, the second winding having a first end and a second end;

a bipolar transistor having a first terminal, a second terminal, and a third terminal, wherein the second terminal is a base terminal, wherein the second end of the first winding of the current transformer is coupled to the second terminal of the bipolar transistor, wherein the second end of the second winding of the current transformer is coupled to the first terminal of the bipolar transistor; and

a diode having an anode and a cathode, wherein the anode is coupled to the first terminal of the bipolar transistor, and wherein the cathode is coupled to the third terminal of the bipolar transistor; and

a package having a first package terminal and a second package terminal, wherein the first package terminal is coupled to the first end of the first winding of the current transformer, wherein the first package terminal is coupled to the first end of the second winding of the current transformer, wherein the second package terminal is coupled to the third terminal of the bipolar transistor, and wherein the package encapsulates the current transformer, the bipolar transistor, and the diode.

2. The electronic device of claim 1, wherein the bipolar transistor and the diode are parts of an integrated circuit.

3. The electronic device of claim 2, wherein the diode is a distributed diode and comprises a plurality of distributed PN junctions.

4. The electronic device of claim 1, wherein the first winding has a first number of turns, wherein the second winding has a second number of turns, wherein the first number is at least twice as large as the second number.

5. The electronic device of claim 4, wherein an increase in a first current flow from the first package terminal through the second winding to the first terminal of the bipolar transistor results in an increase in a second current flow from the first package terminal through the first winding to the second terminal of the bipolar transistor.

6. The electronic device of claim 1, wherein the bipolar transistor has a reverse breakdown voltage between the third terminal of the bipolar transistor to the second terminal of the bipolar transistor, and wherein the reverse breakdown voltage is at least twenty volts.

7. The electronic device of claim 1, wherein the first and second windings are wrapped around a ring-shaped core.

8. The electronic device of claim 1, wherein the package has no package terminal other than the first package terminal and the second package terminal.

9. The electronic device of claim 1, wherein the bipolar transistor and the diode are parts of an integrated circuit, wherein the diode is a distributed diode and comprises a plurality of PN junctions, wherein the bipolar transistor includes a lightly doped layer, wherein a base region of the bipolar transistor and a collector region of the bipolar transistor are disposed on an opposite side of the lightly doped layer from an emitter region of the bipolar transistor.

10. The electronic device of claim 9, wherein the bipolar transistor comprises a base metal electrode that adjoins the base region, wherein the bipolar transistor comprises a collector metal electrode that adjoins the collector region, and wherein the collector metal electrode bridges over the base metal electrode.

11. The electronic device of claim 10, wherein the current transformer has a ferrite core.

12. The electronic device of claim 1, wherein there is no resistive current sense element disposed in a collector current path between the first package terminal and the first terminal of the bipolar transistor, and wherein there is no semiconductor material disposed in a collector current path between the first package terminal and the first terminal of the bipolar transistor.

13. An electronic device comprising:

a bipolar transistor having an emitter, a base, and a collector;

a diode having an anode and a cathode, wherein the anode is coupled to the collector of the bipolar transistor, and wherein the cathode is coupled to the emitter of the bipolar transistor;

a package having a first package terminal and a second package terminal, wherein the second package terminal is coupled to the emitter of the bipolar transistor; and

means for injecting a base current I_B from the first package terminal into the base of the bipolar transistor when a collector current I_C is flowing from the first package terminal and through the bipolar transistor from the collector to the emitter, and wherein the package encapsulates the bipolar transistor, the diode and the means for injecting.

14. The electronic device of claim 13, wherein the means injects the base current such that a collector-to-emitter voltage drop across the bipolar transistor is less than 0.7 volts at a time when the collector current I_C is flowing.

15. The electronic device of claim 13, wherein the means injects the base current such that a voltage drop from the first package terminal, through the bipolar transistor, and to the second package terminal is less than 0.7 volts at a time when the collector current I_C is flowing.

16. The electronic device of claim 13, wherein the means injects the base current such that the electronic device blocks current flow from the second package terminal to the first package terminal when the second package terminal is at a higher voltage than the first package terminal, and such that the electronic device conducts current flow from the first package terminal to the second package terminal when the first package terminal is at a higher voltage than the second package terminal.

17. The electronic device of claim 13, wherein a voltage drop from the first package terminal to the second package terminal is substantially less than 0.7 volts when a current greater than a predetermined critical current is flowing from the first package terminal to the second package terminal, and wherein a voltage drop from the first package terminal to the second package terminal is limited by the diode to approximately 0.8 volts when a current less than the predetermined critical current is flowing from the first package terminal to the second package terminal.

18. A method comprising:

assembling a current transformer, a bipolar transistor, and a diode such that a first end of a first winding of the current transformer is coupled to a first package terminal of a package, such that a first end of a second winding of the current transformer is coupled to the first package terminal of the package, such that a second end of the first winding of the current transformer is coupled to a base of the bipolar transformer, such that a second end of the second winding of the current transformer is coupled to a collector of the bipolar transistor, such that an emitter of the bipolar transistor is coupled to a second package terminal of the package, such that an anode of the diode is coupled to the collector of the bipolar transistor, and such that a cathode of the diode is coupled to the emitter of the bipolar transistor.

19. The method of claim 18, wherein the bipolar transistor and the diode are parts of an integrated circuit.

20. The method of claim 18, wherein the package has no package terminal other than the first package terminal and the second package terminal.

21. The method of claim 18, wherein the package includes an amount of molded plastic encapsulant, and wherein the molded plastic encapsulant encapsulates the current transformer, the bipolar transistor, and the diode.

22. The method of claim 18, wherein the anode of the diode is coupled to the collector of the bipolar transistor via a collector metal electrode.

23. The method of claim 18, wherein the diode is a distributed diode that comprises a plurality of PN junctions.

24. The method of claim 18, wherein the bipolar transistor comprises a base metal electrode that adjoins the base, wherein the bipolar transistor comprises a collector metal electrode that adjoins the collector, and wherein the collector metal electrode bridges over the base metal electrode.