ZENER DIODE PROTECTION NETWORK IN SUBMOUNT FOR LEDS CONNECTED IN SERIES
First Claim
1. A light emitting device comprising:
- N flip-chip light emitting diodes (LEDs) connected in series, the LEDs having electrodes and semiconductor light emitting surfaces, where N is two or more, wherein there is a node at each connection between LEDs, and wherein the LEDs comprise a first end LED having an anode connected to a first power terminal and a second end LED having a cathode connected to a second power terminal; and
a transient voltage suppression circuit connected to the N LEDs comprising a first end zener diode connected to the anode of the first end LED, a second end zener diode connected to the cathode of the second end LED, and only one intermediate zener diode per node connected to its associated node at each connection between LEDs.
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Accused Products
Abstract
A transient voltage suppressor circuit is disclosed for a plurality (N) of LEDs connected in series. Only one zener diode is created for connection to each node between LEDs, and a pair of zener diodes (the “end” zener diodes) are connected to the two pins (anode and cathode pads) of the series string. Therefore, only N+1 zener diodes are used. The end zener diodes (Q1 and Qn+1) effectively create back-to-back zener diodes across the two pins since the zener diodes share a common p+ substrate. The n+ regions of the end zener diodes Q1 and Qn+1 have the highest breakdown voltage requirement and must be placed relatively far apart. Adjacent n+ regions of the intermediate zener diodes have a much lower breakdown voltage requirement so may be located close together. Since there are fewer zener diodes and their spacings may be small, the zener diodes may be placed within a very small footprint or can be larger for better suppressor performance.
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Citations
15 Claims
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1. A light emitting device comprising:
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N flip-chip light emitting diodes (LEDs) connected in series, the LEDs having electrodes and semiconductor light emitting surfaces, where N is two or more, wherein there is a node at each connection between LEDs, and wherein the LEDs comprise a first end LED having an anode connected to a first power terminal and a second end LED having a cathode connected to a second power terminal; and a transient voltage suppression circuit connected to the N LEDs comprising a first end zener diode connected to the anode of the first end LED, a second end zener diode connected to the cathode of the second end LED, and only one intermediate zener diode per node connected to its associated node at each connection between LEDs. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method comprising:
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providing on a silicon submount N flip-chip light emitting diodes (LEDs) connected in series, the LEDs having electrodes and semiconductor light emitting surfaces, where N is three or more, wherein there is a node at each connection between LEDs, and wherein the LEDs comprise a first end LED having an anode connected to a first power terminal and a second end LED having a cathode connected to a second power terminal, the silicon submount having formed in and on it a transient voltage suppression circuit connected to the N LEDs comprising a first end zener diode connected to the anode of the first end LED, a second end zener diode connected to the cathode of the second end LED, and only one intermediate zener diode per node connected to its associated node at each connection between LEDs, wherein the silicon submount is a p+ type and each zener diode is formed by a n+ region in a surface of the silicon submount, a patterned metal layer being formed over a top surface of the silicon submount, the metal layer interconnecting all LEDs in series and connecting the zener diodes to the electrodes of the LEDs; connecting a bias voltage to the p+ type material in the silicon submount to electrically bias the semiconductor light emitting surfaces of the N LEDs via the p+ material and the zener diodes; immersing the semiconductor light emitting surfaces in an electrolyte solution; and performing photo-electrochemical etching (PEC) of the semiconductor light emitting surfaces.
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Specification