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2.25 Active DC-DC converter
Circuit 58: DC-DC converter 9V to 18V with coil-moving instrument
Setup information
Install the two transistors, the two diodes and the five resistors as shown in Fig. 2.58. Next, install the
ceramic capacitor, the electrolytic capacitor and the fixed inductance. Make sure that the electrolytic capaci-
tor has a dielectric strength of 160V. The twelve jumper wires come next. Last but not least connect the
moving-coil instrument. Check the placement on the board again and only then connect the battery.
Experiment
This circuit is used to convert a larger DC voltage to a smaller one. The two transistors ensure that strong
current pulses are sent through the fixed value inductor. This results in a very high induction voltage, which
charges the electrolytic capacitor C2 after rectification with D1. There then the highly-transformed output
voltage is available. In our circuitry the unregulated output voltage is at 18V. The voltage is detected by the
red LED and the moving-coil instrument.
The circuit diagram for this experiment is shown in Chap. 3, Fig. 3.58.
Components required:
2 x 2N3904 transistors,
1 x 1N4148 silicon diode,
1 x red LED, 1 x 1 MΩ resistor,
1 x 10 kΩ resistor, 3 x 22 kΩ
resistors, 1 x 220 μH fixed
inductance, 1 x 1 nF ceramic
capacitor, 1 x 1 μF/160V
electrolytic capacitor,
1 x breadboard, 1 x 9V bat-
tery with clip connector,
1 x moving-coil instrument.
Fig. 2.58: DC-DC converter 9V to
18V with coil-moving instrument
83
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