Extended dynamic range drive circuit for emitter arrays

摘要

Drive circuit (100, 200, 300, 400) for LED thermal emitters in pixel elements of an infrared scene projector (IRSP). At least two current sources (Q1, Q2, Q5) provide output currents (I1, I2, I3) which may be summed and provided to a single LED (150), or provided independently to two or more LEDs (450A, 450B). The current sources may have different gains (G1, G2, G3), and different turn-on voltages (Voffset). This allows for different resolutions for different ranges of apparent temperatures, such as high resolution in a low range and low resolution in a high range, thereby facilitating a digital implementation of the drive circuit(s).

主权项

1. A drive circuit for an LED-based thermal emitter of an infrared scene projector (IRSP) comprising:
an input line for receiving a voltage input (Vin); at least one output line for providing corresponding at least one output current (Iout, I1, I2) to at least one LED in a pixel of the IRSP; a first transistor (Q1) having a first gain (G1) and providing a first output current (I1) to the at least one LED in response to the voltage input (Vin); a second transistor (Q2) having a second gain (G2) and providing a second output current (I2) to the at least one LED in response to the voltage input (Vin); wherein: the second gain (G2) of the second transistor (Q2) is larger than the first gain (G1) of the first transistor (Q1); and a first offset voltage is applied to the second transistor (Q2) to establish a first breakpoint between a low end range of apparent temperatures with high resolution and a higher range of apparent temperatures with lower resolution.