Low forward voltage rectifier

• US 9,350,254 B2
• Filed: 07/02/2015
• Issued: 05/24/2016
• Est. Priority Date: 10/29/2011
• Status: Active Grant

• Current Assignee: Littelfuse Incorporated
• Original Assignee: IXYS Corporation (Littelfuse Incorporated)
• Inventors: Seok, Kyoung Wook
• Primary Examiner(s): Berhane, Adolf
• Application Number:
  US14/790,709
• Publication Number:
  US 20150311811A1
• Time in Patent Office: 327 Days
• Field of Search: 363/21.12, 363/21.13, 363/21.14, 363/147
• US Class Current: 1/1
• 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. 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 transistor, 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, such that a cathode of the diode is coupled to the emitter of the bipolar transistor, and such that the package includes an amount of molded plastic encapsulant that encapsulates the current transformer, the bipolar transistor and the diode.

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

3. The method of claim 1, wherein the package has no package terminal other than the first package terminal and the second package terminal.

4. The method of claim 1, wherein the anode of the diode is coupled to the collector of the bipolar transistor via a collector metal electrode.

5. The method of claim 1, wherein the diode is a distributed diode that comprises a plurality of PN junctions.

6. The method of claim 1, 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.

7. The method of claim 1, wherein there is no diode whose anode is directly connected to the emitter of the bipolar transistor and whose cathode is directly connected to the base of the bipolar transistor.

8. The method of claim 1, wherein the first winding has a first number of turns, wherein the second winding has a second number of turns, and wherein the first number is at least twice as large as the second number.

9. The method of claim 1, wherein the bipolar transistor has a reverse breakdown voltage between the emitter of the bipolar transistor to the base of the bipolar transistor, and wherein the reverse breakdown voltage is at least twenty volts.

10. The method of claim 1, wherein the current transformer has a ferrite core.

11. A method comprising:

coupling an anode of a diode to a collector of a bipolar transistor;

coupling a cathode of the diode to an emitter of the bipolar transistor; and

packaging the diode, a current transformer and a bipolar transistor in a two-terminal package, wherein a first end of a first winding of the current transformer is coupled to a first package terminal of the package, wherein a first end of a second winding of the current transformer is coupled to the first package terminal of the package, wherein a second end of the first winding of the current transformer is coupled to a base of the bipolar transistor, wherein a second end of the second winding of the current transformer is coupled to a collector of the bipolar transistor, wherein an emitter of the bipolar transistor is coupled to a second package terminal of the package, and wherein the package includes an amount of molded plastic encapsulant that encapsulates the diode, the current transformer and the bipolar transistor.

12. The method of claim 11, wherein the bipolar transistor and the diode are parts of an integrated circuit.

13. The method of claim 11, wherein the anode of the diode is coupled to the collector of the bipolar transistor via a collector metal electrode.

14. The method of claim 11, wherein the diode is a distributed diode that comprises a plurality of PN junctions.

15. The method of claim 11, 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.

16. The method of claim 11, wherein there is no diode whose anode is directly connected to the emitter of the bipolar transistor and whose cathode is directly connected to the base of the bipolar transistor.

17. The method of claim 11, further comprising:

wrapping the first winding and the second winding around a ring-shaped core.

18. The method of claim 11, wherein the current transformer has a ferrite core.

19. The method of claim 11, wherein there is no resistive current sense element disposed in a collector current path between the first package terminal and the collector of the bipolar transistor.