Multi-iPM Laser Drive Circuit With Shared Current Source
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Solution Overview
Problem
Existing semiconductor light emitting devices with multiple iPM lasers face issues of large size, high power consumption, and heat generation due to unnecessary standby power consumption, particularly in applications requiring compact and efficient operation.
Innovation Solution
A semiconductor light emitting device with a common current source circuit for multiple iPM lasers, switch sections for ON/OFF control, and integrated drive circuitry to reduce power consumption and heat generation, allowing for smaller device size and efficient operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a separate current source circuit is provided for each iPM laser, then each laser can be independently controlled, but the device size and power consumption increase due to multiple redundant circuits
Solution Approach 1:
The patent merges multiple separate current source circuits into a single shared current source circuit that serves all iPM lasers. This is achieved by providing a common current source circuit that supplies current to multiple lasers through shared current supply lines, thereby reducing the overall device area while maintaining independent control capability through individual switch sections.
Solution Approach 2:
The shared current source circuit is designed to serve multiple functions by providing current to multiple different iPM lasers. The single current source circuit can dynamically supply current to any combination of lasers through the switch sections, making it a universal current supply solution that replaces multiple dedicated circuits.
2Measurement precision
If multiple digital-to-analog converters and operational amplifiers are provided for each laser, then precise control is achieved, but power consumption and heat generation increase due to standby power in non-operating circuits
Solution Approach 1:
The patent combines multiple separate digital-to-analog converters and operational amplifiers into shared circuits. A single digital-to-analog converter converts digital control signals that are then distributed to multiple lasers, and a shared operational amplifier processes control voltages for multiple lasers through the switch sections, eliminating redundant conversion and amplification circuits.
Solution Approach 2:
The switch sections enable periodic or selective activation of individual laser channels. By controlling the switch sections to activate only the required laser channels at specific times, the system minimizes the number of active circuits during operation, thereby reducing standby power consumption and heat generation from non-operating circuits.
3Ease of operation
If a large number of signal lines are provided between the microcontroller and digital-to-analog converter, then individual control of each laser is enabled, but the device complexity and area increase
Solution Approach 1:
The microcontroller uses a single digital control signal line that can address and control multiple iPM lasers sequentially or selectively through the switch sections. This universal control approach allows one signal line to serve multiple functions by controlling different laser channels at different times, thereby reducing the total number of dedicated signal lines required.
Solution Approach 2:
The patent introduces temporal dimension to the control scheme by enabling sequential or time-multiplexed control of multiple lasers through a single control line. Instead of requiring simultaneous dedicated lines for each laser, the system uses time-based separation to achieve individual control with fewer physical connections.
Data Source
AI summary
A semiconductor light emitting device includes: a plurality of iPM lasers each having a first surface and a second surface opposite to the first surface and outputting light from the first surface; and a drive circuit that supplies a drive current to cause each of the plurality of iPM lasers to emit light. The drive circuit includes: a current source circuit common to the plurality of iPM lasers; a plurality of switch sections provided corresponding to the plurality of iPM lasers, respectively, for ON/OFF switching of the drive current; and a switch operating section that individually operates each of the plurality of switch sections.