Laser diode drive circuit

• US 6,510,168 B1
• Filed: 09/27/2000
• Issued: 01/21/2003
• Est. Priority Date: 03/06/2000
• Status: Expired due to Term

• Current Assignee: NeoPhotonics Corporation (Lumentum Holdings Inc.)
• Original Assignee: OKI Electric Industry Company Limited
• Inventors: Kikuchi, Osamu
• Primary Examiner(s): Ip, Paul
• Assistant Examiner(s): AL NAZER, LEITH A
• Application Number:
  US09/669,878
• Time in Patent Office: 846 Days
• Field of Search: 372/38.02, 372/31
• US Class Current: 372/38.02
• CPC Class Codes: H01S 5/042 Electrical excitation ; Circuits therefor monolithically integrated laser drive components H01S5/0261
• CPC Class Codes: H03K 17/603 with coupled emitters
• CPC Class Codes: H03K 17/6292 using current steering means
• CPC Class Codes: H03K 2217/0036 Means reducing energy consumption

Abstract

A drive current Ip used to control the light output from a laser diode LD is controlled by using an output Vsft from a level shift circuit 3. By inserting the level shift circuit 3 between a drive source (V+) and a switch buffer 5, the lower limit (V+)−(V−) of the drive voltage in the circuit is lowered to enable the laser diode drive circuit to be driven at a lower voltage and to achieve a reduction in power consumption.

Claims

1. A laser diode drive circuit comprising:

a level shift circuit connected to a drive source, that reduces a drive source voltage by a specific quantity;

a current switch that turns on/off a laser diode connected to said drive source; and

a switch buffer connected to said level shift circuit, that implements control on said current switch;

wherein said level shift circuit varies the quantity by which said drive source voltage is reduced in correspondence to a signal Vset input from the outside;

wherein said level shift circuit is provided with a first resistor located between said drive source voltage and said switch buffer and a plurality of resistors connected to said first resistor via a transistor, and a voltage generated at said first resistor is varied by varying a combined resistance of said plurality of resistors;

wherein;

said plurality of resistors are connected in series;

a plurality of switches are provided between said plurality of resistors and the ground; and

a decoder that selects one of said plurality of switches in conformance to said signal Vset input from the outside to vary said combined resistance of said plurality of resistors is provided.

2. A laser diode drive circuit comprising:

a level shift circuit connected to a drive source, that reduces a drive source voltage by a specific quantity;

a current switch that turns on/off a laser diode connected to said drive source; and

a switch buffer connected to said level shift circuit, that implements control on said current switch;

wherein said level shift circuit varies the quantity by which said drive source voltage is reduced in correspondence to a signal Vset input from the outside;

wherein said level shift circuit is provided with a combined resistance constituted of a plurality of resistors located between said drive source voltage and said switch buffer, and said level shift circuit varies the combined resistance value of said combined resistance;

wherein;

said plurality of resistors are connected in series;

a plurality of switches are provided between said plurality of resistors and said switch buffer; and

a decoder that selects one of said plurality of switches in conformance to said signal Vset input from the outside to vary said combined resistance of said plurality of resistors is provided.