K.-Y. Hung and Y.-C. Chen (Taiwan)
Switching regulator, Transformer-free circuitry, Flyback boost circuit.
A commercial power supply is bulk in size, extremely expensive and outputs considerably noisy voltage, carrying about 45mV of surge at the maximum. For an APD (Avalanche Photo Diode) used to detect weak fluorescent signals, this make it easy to generate extremely intensified noise, thereby degrading the S/N ratio. To resolve such a problem, a portable high voltage transformer-free DC drive circuit module with low cost, noise, and power for photoelectric components will be developed in this paper. Designed on the switching regulator concept, this power supply module outputs DC voltage as high as about 142V, with the noise approximately down to 1.28mV, using only USB 0-5V DC input. It allows for the switching current up to 1.2A. The module may be used on photoelectric components requiring high reverse voltage, such as APDs, PZTs (Piezo Transformers), VFDs (Vacuum Florescent Displays), and MEMs (Micro Electric Machines). This low-noise module effectively reduces the thermal noise of photodiodes, improving the S/N ratio of photoelectric components about 37%. Designed with a transformer-free circuitry, the module is efficient, compact, and portable. This power supply module is successfully developed; it will be much more feasible to utility in developing portable products, such as TFT-LCD bias, digital cameras, and other advanced products.
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