Polarity sensing circuit

Patent metadata

Field	Value
Publication number	US-9506955-B2
Application number	US-201313932678-A
Country	US
Kind code	B2
Filing date	Jul 1, 2013
Priority date	Jul 1, 2013
Publication date	Nov 29, 2016
Grant date	Nov 29, 2016

Abstract

A dc input circuit receives a dc input voltage. At least four rectification elements are coupled to each other in a diode bridge configuration, where an input of the diode bridge configuration is coupled to the dc input circuit to receive the dc input voltage. At least one of the rectification elements includes a transistor. A decision circuit indicates, as a function of one of collector current and emitter current of the transistor, that the received dc input voltage has normal or reversed polarity. Other embodiments are also described and claimed.

First claim

What is claimed is:

1. A polarity sensing circuit comprising:
a dc input circuit to receive a dc input voltage;
at least four rectification elements coupled to each other in a diode bridge configuration whose input is coupled to the dc input circuit to receive the dc input voltage, wherein at least one of the rectification elements comprises a transistor with a control electrode in a current path of the diode bridge configuration that conducts a current from the input of the diode bridge configuration through the transistor to an output of the diode bridge configuration; and
a decision circuit coupled to the transistor, the decision circuit to indicate, as function of the current conducted by the transistor, that the received dc input voltage has normal or reversed polarity.

2. The polarity sensing circuit of claim 1 wherein the transistor is a bipolar junction transistor (BJT) in which the current conducted by the transistor is a collector current.

3. The polarity sensing circuit of claim 2 wherein the transistor is one of an NPN BJT and a PNP BJT.

4. The polarity sensing circuit of claim 1 wherein the transistor is a junction field effect transistor (JFET) in which the current conducted by the transistor is a drain current.

5. The polarity sensing circuit of claim 1 wherein the transistor has at least three electrodes comprising a base electrode, a collector electrode and an emitter electrode, wherein the emitter and the base electrodes are cathode and anode terminals of the rectification element, and the collector electrode is coupled to the decision circuit and the decision circuit is responsive to a collector current of the transistor.

6. The polarity sensing circuit of claim 1 wherein the decision circuit is powered by an output of said four rectification elements in the diode bridge configuration which provides a dc output voltage that has the same polarity regardless of polarity of the dc input voltage.

7. The polarity sensing circuit of claim 6 wherein the dc input circuit comprises a connector configured to connect with a mating connector of one of a power cable and an accessory cable that brings the dc input voltage from a separate dc power source.

8. The polarity sensing circuit of claim 1 in combination with a power supply circuit that has
a rectifier circuit coupled to draw power from a dc power source, and
a control input to receive the polarity indication from the decision circuit, wherein the control input is configured to control the rectifier circuit in accordance with the received polarity indication.

9. The polarity sensing circuit and power supply circuit of claim 8 wherein the power supply circuit has a configurable rectification circuit that uses transistor switch rectification elements and that is configured for polarity in accordance with the polarity indication from the decision circuit.

10. The polarity sensing circuit and power supply circuit of claim 8 wherein the power supply circuit is to provide at least ten (10) times more output current than an output of said four rectification elements in the diode bridge configuration.

11. The polarity sensing circuit of claim 1 wherein the dc input circuit comprises a connector configured to connect with a mating connector of a power cable that brings the dc input voltage from a separate dc power source.

12. An electronic device comprising:
a dc input to receive a dc input voltage;
a main power supply having a power input coupled to the dc input;
a supporting power supply having at least four rectification elements coupled to each other in a diode bridge configuration whose input is coupled to the dc input to receive the dc input voltage, wherein at least one of the rectification elements comprises a transistor with a control electrode in a current path of the diode bridge configuration that conducts a current from the input of the diode bridge configuration through the transistor to an output of the diode bridge configuration; and
a decision circuit having a decision input coupled to the transistor and that is to indicate polarity of the received dc input voltage to the main power supply as a function of the current conducted by the transistor in the supporting power supply.

13. The electronic device of claim 12 wherein the decision circuit is powered by an output of said four rectification elements in the diode bridge configuration.

14. The electronic device of claim 12 wherein the main power supply has a configurable rectification circuit that uses transistor switch rectification elements and that is configured for polarity in accordance with the polarity indication from the decision circuit.

15. The electronic device of claim 12 wherein the main power supply is to provide at least ten (10) times more output current than an output of said four rectification elements in the diode bridge configuration.

16. The electronic device of claim 12 wherein the transistor is a bipolar junction transistor (BJT) in which the current conducted by the transistor is a collector current.

17. The electronic device of claim 12 wherein the transistor is a junction field effect transistor (JFET) in which the current conducted by the transistor is a drain current.

18. A method for operating an electronic device, comprising:
rectifying a dc input voltage using a circuit in which at least four rectification elements are coupled to each other in a diode bridge configuration, wherein at least one of the rectification elements is a transistor with a control electrode in a current path of the diode bridge configuration that conducts a current from the input of the diode bridge configuration through the transistor to an output of the diode bridge configuration; and
indicating polarity of the dc input voltage as a function of the current conducted by the transistor.

19. The method of claim 18 further comprising configuring a power supply in accordance with the polarity indication.

20. The method of claim 19 wherein configuring the power supply comprises turning on and off a plurality of transistor switches of an active rectification circuit that is receiving the dc input voltage.

21. The method of claim 18 wherein the transistor is a bipolar junction transistor (BJT) in which the current conducted by the transistor is a collector current.

22. The method of claim 18 wherein the transistor is a junction field effect transistor (JFET) in which the current conducted by the transistor is a drain current.

Assignees

• Apple Inc

Inventors

• Moyer Todd K

Classifications

• G01R19/14 Primary

  Indicating direction of current; Indicating polarity of voltage · CPC title