Circuit simulating a diode

• US 6,060,943 A
• Filed: 04/14/1998
• Issued: 05/09/2000
• Est. Priority Date: 04/14/1998
• Status: Expired due to Term

• Current Assignee: Minebea Company Limited (MinebeaMitsumi Inc.)
• Original Assignee: NMB Incorporated (MinebeaMitsumi Inc.)
• Inventors: Jansen, Arian M.
• Primary Examiner(s): Callahan, Timothy P.
• Assistant Examiner(s): Nguyen, Hai L.
• Application Number:
  US09/059,968
• Time in Patent Office: 756 Days
• Field of Search: 327/543, 327/541, 327/540, 327/538, 327/493, 330/288
• US Class Current: 327/538
• CPC Class Codes: H03K 17/063 in field-effect transistor switches
• CPC Class Codes: H03K 17/302 in field-effect transistor switches
• CPC Class Codes: H03K 2017/307 circuits simulating a diode, e.g. threshold zero

Abstract

A circuit simulating the function of a diode in the sense that it conducts current in one direction and blocks current in the opposite direction, but which has a low forward voltage drop. A voltage comparator and a three terminal switch are connected so that the intrinsic reverse diode associated with the switch is harnessed to conduct current in the direction in which it is desired to conduct current and to block current in the direction in which it is desired to block current. A voltage comparator controls the control terminal of the three terminal switch to turn on the switch to conduct current from a terminal A to a terminal K when the voltage at terminal A is higher than the voltage at terminal K and to interrupt current from terminal K to terminal A when the voltage at terminal K is higher than the voltage at terminal A. The switch terminal (source or drain) that is typically connected to the higher voltage of two voltage terminals is instead connected to the lower voltage of the two voltage terminals. The switch may be a MOSFET, p- or n-channel, depletion or enhancement. Alternatively, a bipolar transistor may be connected to a voltage comparator to simulate the function of a diode. Detection of a malfunctioning transistor is detected and indicated. Alternate embodiments of voltage comparators are disclosed. The invention further includes a method of conducting, current in one direction and blocking current in a second direction which reduces power losses.

Claims

1. A circuit with two terminals A and K, which conducts current in one direction from terminal A to terminal K and blocks current in the opposite direction from terminal K to terminal A, comprising:

a voltage comparator, having a positive input, a negative input, and an output; and

a three terminal means for switching current with a source for electrons, a drain for electrons, and a control terminal controlled by a voltage from the output of said voltage comparators;

said three terminal switching means having an internal resistance associated therewith, and an intrinsic diode associated therewith between said source and said drain; and

wherein an effective anode of said intrinsic diode is connected to terminal A of said circuit, and an effective cathode of said intrinsic diode is connected to terminal K of said circuit;

wherein said source is connected to the positive input of said voltage comparator and said drain is connected to the negative input of said voltage comparator; and

wherein said voltage comparator comprises a bipolar transistor with an emitter, collector and base, two series resistors, and a diode;

wherein the emitter of said bipolar transistor is the positive input of said voltage comparator, the collector of said bipolar transistor is the output of said voltage comparator, said series resistors are connected between the collector and the base of said bipolar transistor, and said base of said bipolar transistor is further connected to an anode of said diode and a cathode of said diode is the negative input of said voltage comparator.

4. A circuit with two terminals A and k, which conducts current in one direction from terminal A to terminal K and blocks current in the opposite direction from terminal K to terminal A, comprising:

a voltage comparator, having a positive input, a negative input, and an output; and

a three terminal means for switching current with a source for electrons, a drain for electrons, and a control terminal controlled by a voltage from the output of said voltage comparator;

said three terminal switching means having an internal resistance associated therewith, and an intrinsic diode associated therewith between said source and said drain; and

wherein an effective anode of said intrinsic diode is connected to terminal A of said circuit, and an effective cathode of said intrinsic diode is connected to terminal K of said circuit;

wherein said source is connected to the positive input of said voltage comparator and said drain is connected to the negative input of said voltage comparator; and

wherein said voltage comparator comprises two resistors and two transistors each having an emitter, a collector and a base, wherein the emitter of the first transistor is the positive input of the voltage comparator, the emitter of the second transistor is the negative input of the voltage comparator, the two resistors are connected in series between the collectors of the first and second transistors, the collector of the first transistor is the output of the voltage comparator, and the bases of the two transistors are connected and shorted to the collector of the second transistor.

2. The circuit as recited in claim 4, wherein said switching means comprises an n-channel MOSFET.

3. The circuit as recited in claim 4, wherein said switching means comprises a p-channel MOSFET.

18. The circuit as recited in claim 4, wherein said switching means comprises an n-channel MOSFET.

19. The circuit as recited in claim 4, wherein said switching means comprises a p-channel MOSFET.

5. A circuit with two terminals A and K, which conducts current in one direction from terminal A to terminal K and blocks current in the opposite direction from terminal K to terminal A, comprising:

a voltage comparator, having a positive input, a negative input, and an output; and

a three terminal means for switching current with a source for electrons, a drain for electrons, and a control terminal controlled by a voltage from the output of said voltage comparator;

said three terminal switching means having an internal resistance associated therewith, and an intrinsic diode associated therewith between said source and said drain; and

wherein an effective anode of said intrinsic diode is connected to terminal A of said circuit, and an effective cathode of said intrinsic diode is connected to terminal K of said circuit;

wherein said source is connected to the positive input of said voltage comparator and said drain is connected to the negative input of said voltage comparator; and

further comprising detection means for detecting if the switching means is malfunctioning.

6. The circuit as recited in claim 5, wherein said detection means detects a low impedance between said control terminal and said source of said switching means.

7. The circuit as recited in claim 5, wherein said detection means detects a low impedance between said control terminal and said drain of said switching means.

8. The circuit as recited in claim 5, wherein said detection means detects a zero current at a control terminal of said switching means.

20. The circuit as recited in claim 5, wherein said switching means comprises an n-channel MOSFET.

21. The circuit as recited in claim 5, wherein said switching means comprises a p-channel MOSFET.

9. A circuit comprising:

a voltage comparator having a positive input, a negative input, and an output;

a switching means for switching current having a drain for electrons, a source for electrons, and a control terminal, wherein said drain is connected to said negative input, said source is connected to said positive input and said control terminal is connected to said output of said voltage comparator; and

further comprising detection means for determining if said switching means is malfunctioning.

10. The circuit as recited in claim 9, wherein said switching means is an n-channel device.

11. The circuit as recited in claim 9, wherein said switching means is a p-channel device.

12. A circuit as recited in claim 9, wherein said switching means is a MOSFET.

13. A circuit comprising:

a voltage comparator having a positive input, a negative input, and an output;

a bipolar transistor having a collector, an emitter, and a base, wherein said collector is connected to said positive input of said voltage comparator, said emitter is connected to said negative input of said voltage comparator, and the base of said bipolar transistor is connected to the output of said voltage comparator; and

further comprising detection means for determining if said bipolar transistor is malfunctioning.

14. The circuit as recited in claim 13, wherein said detection means detects a low impedance between said base and collector of said bipolar transistor.

15. A method of conducting current in one direction from a terminal A to a terminal K and blocking current in a second direction from said terminal K to said terminal A, comprising:

i. comparing a voltage signal at a positive input of a comparator to a voltage signal at a negative input of said comparator to obtain an output voltage;

ii. connecting a three terminal switch between terminal A and terminal K, wherein said three terminal switch has an internal resistance associated therewith, an intrinsic diode associated therewith, and a source for electrons, a drain for electrons and a control terminal;

iii. connecting the output voltage to said control terminal of said three terminal switch;

iv. connecting an effective anode of said intrinsic diode to terminal A;

v. connecting an effective cathode of said intrinsic diode to terminal K;

vi. inputting voltage signals to said comparator by connecting said source of said three terminal switch to said positive input of said comparator, and connecting said drain of said three terminal switch to said negative input of said comparator; and

vii. further comprising detecting whether said three terminal switch is malfunctioning.

16. The method as recited in claim 15, wherein the malfunctioning of said three terminal switch is detected by detecting a low impedance between the control terminal and one of the source and drain of said three terminal switch.

17. The method as recited in claim 15, wherein the malfunctioning of said three terminal switch is detected by detecting zero current at the control terminal of said switching means.