CURRENT SENSING ON A MOSFET

• US 20120007613A1
• Filed: 09/21/2011
• Published: 01/12/2012
• Est. Priority Date: 12/05/2007
• Status: Active Grant

• Current Assignee: Meir Gazit
• Original Assignee: Meir Gazit
• Inventors: Gazit, Meir
• Granted Patent: US 9,831,824 B2
• Time in Patent Office: Days
• US Class Current: 324/654
• CPC Class Codes: G01S 3/7861 Solar tracking systems
• CPC Class Codes: H02J 13/00 Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network
• CPC Class Codes: H02J 2300/26 involving maximum power point tracking control for photovoltaic sources maximum power point systems in particular G05F1/67
• CPC Class Codes: H02J 3/38 Arrangements for parallely feeding a single network by two or more generators, converters or transformers
• CPC Class Codes: H02J 3/381 Dispersed generators
• CPC Class Codes: H02J 3/388 Islanding, i.e. disconnection of local power supply from the network
• CPC Class Codes: H02J 3/46 Controlling of the sharing of output between the generators, converters, or transformers
• CPC Class Codes: H02M 1/0009 Devices or circuits for detecting current in a converter
• CPC Class Codes: H02M 1/0077 Plural converter units whose outputs are connected in series
• CPC Class Codes: H02M 1/08 Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
• CPC Class Codes: H02M 1/44 Circuits or arrangements for compensating for electromagnetic interference in converters or inverters
• CPC Class Codes: H02M 3/04 by static converters
• CPC Class Codes: H02M 7/44 by static converters
• CPC Class Codes: H02M 7/493 the static converters being arranged for operation in parallel
• CPC Class Codes: H02S 40/22 Light-reflecting or light-concentrating means directly associated with the PV cell or integrated with the PV cell H01L31/054
• CPC Class Codes: Y02E 10/52 PV systems with concentrators
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers

Abstract

A device having a switch with a voltage applied across the switch. A current sensing circuit is connected to one terminal of the switch. The current sensing circuit receives power independently of the voltage applied across the switch. The power supply shares the other terminal of the switch with the current sensing circuit. The switch is adapted for opening and closing. When the switch closes, the current sensing circuit senses current through the switch and upon opening the switch the high voltage of the switch is blocked from the current sensing circuit. The sense current is caused to flow from the current sensing circuit to the other terminal when the switch is closed. The flow of the sense current produces a voltage which is compared differentially to another voltage referenced by the other terminal.

Claims

1. A device comprising:

a switch;

wherein a voltage is applied across said switch;

a current sensing circuit connected to one terminal of said switch;

wherein said current sensing circuit which receives power independently of said voltage;

wherein said power shares the other terminal of said switch with said current sensing circuit;

wherein said switch is adapted for opening and closing so that when said switch is closed, said current sensing circuit is configured to sense current through said switch and when said switch is open, voltage of said switch is blocked from said current sensing circuit.

2. The device according to claim 1 wherein a sense current is caused to flow from the current sensing circuit to said other terminal when said switch is closed.

3. The device according to claim 2, wherein flow of said sense current produces a first voltage which is compared differentially to a second voltage referenced by said other terminal.

4. The device according to claim 1, wherein said current sensing circuit includes an operational amplifier which is configured to output a voltage sense signal proportional to current flowing through said switch.

5. The circuit according to claim 1, wherein said switch is a MOSFET.

6. The device according to claim 1, further comprising:

a switched power converter including said switch;

wherein said current sensing circuit is adapted to sense current while the voltage output of said switched power converter is switched to a common rail.

7. The device according to claim 6, wherein said current sensing circuit draws said power independently and not from said switched power converter.

8. The device according to claim 6, wherein said switched power converter is selectably either:

a buck converter a boost converter or a buck/boost converter.

9. The device according to claim 6, further comprising:

an inductor connected to said one terminal of said switch;

wherein said current sensing circuit senses current through said inductor

10. The device according to claim 9, wherein said current sensing circuit does not integrate voltage across said inductor.

11. In a device including:

a switch;

wherein a voltage is applied across the switch, wherein a current sensing circuit is connected to one terminal of the switch, wherein the current sensing circuit which receives power independently of the voltage,

wherein the power derived independently, shares the other terminal of the switch with the current sensing circuit, a method comprising the steps of;

upon closing the switch the current sensing circuit senses the current through the switch; and

upon opening the switch, voltage of the switch is blocked from the current sensing circuit.

12. A circuit for sensing current flowing through an inductor, the circuit comprising:

a cathode of a first diode connected to a first side of the inductor;

a cathode of a second diode connected to a second side of the inductor;

a first node connecting the anode of the first diode with the anode of the second diode;

a first voltage divider with a first and second resistor connected between the first node and a power supply, wherein the connection between the first and second resistor forms a second node;

a second voltage divider with a third and fourth resistor and a third diode disposed between the power supply and a ground, wherein the connection between the third and fourth resistor forms a third node;

a capacitor disposed between the ground and the third node;

an operational amplifier with a non-inverting input connected to the second node and an inverting input connected to the third node; and

a fifth resistor connected between the output of the amplifier and the third node;

wherein power is supplied to the operational amplifier and current is not drawn from the inductor.