Homemade Starfinder Power Supply

This article introduces a power conversion circuit unit in a commercially available star finder circuit. It uses a single-ended flyback structure with TL494 as the control IC. The control IC in most desktop computer power supplies is TL494 (half-bridge type). This circuit has battery current limiting and antenna short-circuit protection functions. When a short circuit occurs, the power supply will be automatically turned off. It is equipped with an antenna access indicator to indicate whether the antenna is connected.

This circuit is applicable to almost all brands of receiver motherboards (including some Zhongjiu motherboards).

Pin ① of TL494 is the output voltage feedback input terminal, and pin (16) is the power consumption current feedback input terminal. Q2 and Q3 are driver tubes. T1 is a switching transformer, pins ⑤ and ⑥ are the same-name terminals, and Q4 is a power MOS tube. Q1 is a switch tube for short-circuit protection. When the antenna has a short-circuit fault, Q1 will change from cutoff to conduction, LED1 will light up, and at the same time, the oscillation will stop because the level of pin ④ of U1 is pulled up. Q5 is a switch tube used to indicate the antenna connection status (when horizontally polarized). This function can detect whether the antenna system has a short circuit or a break. J1 is a 4PIN plug with a wire, which is connected to the power input socket of the motherboard.