Switch-mode oximeter LED drive with a single inductor
First Claim
1. A light emitter drive circuit for an oximeter comprising:
- a voltage generating circuit;
an inductor coupled to said voltage generating circuit;
a first switching circuit coupled to a first node of said inductor;
first and second energy storage circuits connected to said first switching circuit, such that current from said inductor can be steered by said first switching circuit to one of said energy storage circuits;
a second switching circuit coupled to a second node of said inductor; and
first and second light emitter drive lines connected to said second switching circuit, such that energy from said first and second energy storage circuits can be alternately coupled to said first and second light emitter drive lines.
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Accused Products
Abstract
A light emitter drive circuit for an oximeter which utilizes a single inductor for driving multiple light emitters. The inductor is connected to a switching circuit to multiple energy storage circuits, such as capacitors. These are alternately charged up, using the same inductor. Subsequently, the capacitors are alternately discharged for their corresponding light emitters through the same inductor. Also, the magnetic susceptibility of the LED drive circuit is reduced by using magnetic flux canceling in the inductor. In one embodiment, a toroidal inductor is used with geometric symmetry and its magnetic flux. In another embodiment, a dual core closed bobbin shielded inductor is used.
76 Citations
15 Claims
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1. A light emitter drive circuit for an oximeter comprising:
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a voltage generating circuit;
an inductor coupled to said voltage generating circuit;
a first switching circuit coupled to a first node of said inductor;
first and second energy storage circuits connected to said first switching circuit, such that current from said inductor can be steered by said first switching circuit to one of said energy storage circuits;
a second switching circuit coupled to a second node of said inductor; and
first and second light emitter drive lines connected to said second switching circuit, such that energy from said first and second energy storage circuits can be alternately coupled to said first and second light emitter drive lines. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. An LED circuit for an oximeter comprising:
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a voltage generating circuit;
an inductor coupled to said voltage generating circuit;
a first switching circuit coupled to a first node of said inductor;
first and second capacitors connected to said first switching circuit, such that current from said inductor can be steered by said first switching circuit to one of said capacitors;
an H-bridge drive switching circuit including four transistors coupled to a second node of said inductor; and
first and second light emitter drive lines, for LEDs in a back-to-back configuration, in the middle of said H-bridge, such that energy from said first and second capacitors can be alternately coupled to said first and second light emitter drive lines. - View Dependent Claims (14, 15)
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13. A light emitter drive circuit for an oximeter comprising:
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a voltage generating circuit;
first and second energy storage circuits;
a magnetic flux canceling inductor coupled to said voltage generating circuit and at least one of said energy storage circuits; and
switching circuitry configured to first steer current into said energy storage circuits, and then provide energy from said first and second energy storage circuits to drive lines for light emitters.
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Specification