Analog signal to discrete time interval converter
An analog signal to discrete time interval converter (ASDTIC) is a specialized kind of an analog-to-digital converter, which converts the analog input signal (e.g. voltage or current) to time intervals between pulses.
This type of conversion is obscure. Its only obvious use, and the origin of the term, lies with NASA around 1970.[1]
ASDTIC were used in the control of DC-DC converters.[2] For use in space-rated systems, reliable hybrid circuits were developed to implement the ASDTIC function.[3]
Operation
The DC-DC converters under study in this work[4] had a similar form as a DC chopper or switching regulator. A bipolar transistor switches current flowing into an L-C network of an inductor and capacitor. To reduce switching losses, the transistor is always turned either fully off or fully on. Control of this transistor is derived from a control circuit that supplies a series of pulses. In the circuits studied here, the pulses are all of equal length. The overall ON time or mark/space ratio of the pulse train (and thus the output power delivered) is controlled by varying the interval between pulses. Closely spaced pulses increase output. This control signal is derived by use of an ASDTIC circuit.[3]
References
- ^ US 3659184, Schwarz, Francisc C., "Analog signal to discrete time interval converter (ASDTIC)", published Apr 25, 1972, assigned to NASA
- ^ Schoenfeld, A. D.; Yu, Y. (February 1973). "ASDTIC control and standardized interface circuits applied to buck, parallel and buck-boost dc to dc power converters". NASA. NASA CR-121106.
- ^ a b c d Schoenfeld, A. D.; Yu, Y. (August 1, 1973). "The application of the analog signal to discrete time interval converter to the signal conditioner power supplies" (PDF). NASA. NASA CR-120906.
- ^ Research contract NAS12-2017, December 1969 – October 1970, TRW for NASA Lewis Research Center
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