Current sensing on a MOSFET
First Claim
1. 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 third resistor connected in series with a fourth resistor to form a second voltage divider;
wherein the second voltage divider is connected between the power supply and the anode of a third diode;
wherein the cathode of the third diode is connected to a ground;
wherein the connection between the third and fourth resistor forms a third node;
a capacitor connected between the ground and the third node;
an operational amplifier with a non-inverting input connected to the third node and an inverting input connected to the second node; and
a fifth resistor connected between the output of the amplifier and the second node;
wherein power is supplied to the operational amplifier and substantially zero current is drawn from the inductor.
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Accused Products
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.
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Citations
19 Claims
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1. A circuit for sensing current flowing through an inductor, the circuit comprising:
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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 third resistor connected in series with a fourth resistor to form a second voltage divider; wherein the second voltage divider is connected between the power supply and the anode of a third diode; wherein the cathode of the third diode is connected to a ground; wherein the connection between the third and fourth resistor forms a third node; a capacitor connected between the ground and the third node; an operational amplifier with a non-inverting input connected to the third node and an inverting input connected to the second node; and a fifth resistor connected between the output of the amplifier and the second node; wherein power is supplied to the operational amplifier and substantially zero current is drawn from the inductor.
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2. A device for sensing current flow in a switched power converter circuit, the switched power converter circuit including a first semi-conductor switch, wherein said first semi-conductor switch includes:
- (i) a first power terminal connected to a first voltage (ii) a second power terminal connected to ground, (iii)a control terminal operatively connected to a drive circuit, wherein said drive circuit drives selectively either a maximal current between said first power terminal and said second power terminal or a substantially zero current between said first power terminal and said second power terminal, the device for sensing current flow comprising;
an operational amplifier; a reference voltage connected to a first differential input of said operational amplifier; a diode with a first anode connected to a second differential input of said operational amplifier; wherein a second reference voltage is connected to said second differential input of said amplifier, and wherein at least one of said maximal current and said substantially zero current modifies said second reference voltage applied to said second differential input of said amplifier, and wherein an output voltage of said operational amplifier is responsive to said maximal current and said substantially zero current; a first cathode of said diode connected to said first power terminal of the first semi-conductor switch. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
- (i) a first power terminal connected to a first voltage (ii) a second power terminal connected to ground, (iii)a control terminal operatively connected to a drive circuit, wherein said drive circuit drives selectively either a maximal current between said first power terminal and said second power terminal or a substantially zero current between said first power terminal and said second power terminal, the device for sensing current flow comprising;
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13. In a device to sense current flow in a switched power converter circuit, the switched power converter circuit including:
- a first semi-conductor switch including a first power terminal connected to a first voltage, a second power terminal connected to ground, a control terminal operatively connected to a drive circuit, wherein the drive circuit drives selectively either a maximal current between the first power terminal and the second power terminal or a substantially zero current between the first power terminal and the second power terminal, the device including a reference voltage connected between a first differential input of an operational amplifier and the ground, a diode with a first anode connected to a second differential input of the operational amplifier, wherein a second reference voltage is connected between the second differential input of the operational amplifier and ground, and a first cathode of the diode connected to the first power terminal, a method comprising the steps of;
upon a current flowing between the first power terminal and the second power terminal approaching the maximal current, sensing the current through said first power terminal and said second power terminal;
wherein an output voltage of the operational amplifier is responsive to said current;upon a current flowing between said first power terminal and said second power terminal approaching the substantially zero current, blocking the first voltage of the first power terminal from the current sensing circuit by the first cathode of said diode. - View Dependent Claims (14, 15, 16, 17, 18, 19)
- a first semi-conductor switch including a first power terminal connected to a first voltage, a second power terminal connected to ground, a control terminal operatively connected to a drive circuit, wherein the drive circuit drives selectively either a maximal current between the first power terminal and the second power terminal or a substantially zero current between the first power terminal and the second power terminal, the device including a reference voltage connected between a first differential input of an operational amplifier and the ground, a diode with a first anode connected to a second differential input of the operational amplifier, wherein a second reference voltage is connected between the second differential input of the operational amplifier and ground, and a first cathode of the diode connected to the first power terminal, a method comprising the steps of;
Specification