Powering the laptop from the power supply of the old TV. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Power Supplies
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One quiet summer evening, I had a big trouble - quite unexpectedly, the laptop's power supply died. Of course, it can be repaired (and later I repaired it by replacing a powerful pulse converter microcircuit and two diodes), but then there was neither the time nor the necessary parts. But there was a set of boards from the old 3USCT TV, including the MP-3-1 power module.
On fig. 1 shows the output diagram of this power module.
As you can see, the voltages available are 130V, 28V, 15V, 12V and 16V. There is nothing suitable to power a laptop, since it requires 18V.
Rewinding the TPI-4-3 transformer is a bad thing, the core is glued tightly, and when you try to separate the ferrite, it cracks (I know about this from repair practice). Therefore, it is optimal, perhaps, to use the 28 V output to power the vertical scan - the power is more than sufficient. The problem is just too much stress. But this problem was solved with the help of two powerful D815G zener diodes (Fig. 2). Each zener diode has a stabilization voltage of 10 V and a stabilization current of 20 to 800 mA. The current consumption of the laptop is 1,5 A. This means that the maximum current is greater than 800 mA, so two zener diodes connected in parallel (maximum current 1,6 A) are taken.
They work on current almost at the limit, so it is advisable to put them on some kind of radiator. I just screwed them onto a piece of metal corner. When the reverse current flows, the zener diode enters the stabilization mode and holds a voltage of 10V. Thus, this voltage is subtracted from the voltage of 28 V and only 18 V remains at the output. If you need more voltage, for example, 20 V, you need to use D815V zener diodes (by 8,2 V). The 390 ohm resistor gives the minimum current at idle.
Some MP-3-3s do not want to start unless the 130V circuit is loaded. If so, load it with a regular 220V 15W or 25W incandescent lamp.
You can set the exact voltage with a trimming resistor R2 on the power module board.
Author: Andreev S.
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