Transformerless nine-volt voltage converter, 9/16 volts 120 milliamps. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Voltage converters, rectifiers, inverters
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The converter (Fig. 4.14) consists of an economical master square-wave generator, assembled on a DD1 chip, and an output power amplifier on transistors V1 ... V4.
The frequency of the master oscillator is approximately 10 kHz. The amplitude of the rectangular pulses at the output of the master oscillator is almost equal to the voltage of the converter power supply. Therefore, during one half-cycle, transistors V1 and V4 are saturated, and V2 and V3 are closed, and capacitor C3 is quickly charged through a saturated transistor V4 and diode V5 to a voltage almost equal to the supply voltage. In the same way, during the other half-cycle, capacitor C4 is charged through a saturated transistor V3 and diode V6. On the capacitor C5, the voltages on the capacitors C3 and C4 are added.
Due to the relatively high conversion frequency, the output voltage ripple is very low. With no load, the converter draws about 5 mA and the output voltage approaches 18 V. With a load current of 120 mA, the output voltage drops to 16 V at a ripple level of 20 mV. Converter efficiency - about 85%, output impedance - about 10 ohms.
If it is necessary that the performance of the converter is maintained when the supply voltage is reduced to 5 V, the resistors R3 and R4 should be replaced with others with a resistance of 1,5 kOhm. A properly assembled converter starts working immediately and does not need to be adjusted. Instead of those indicated in the diagram, any transistors of the KT315 and KT361 series with a static current transfer ratio of at least 50 can be used in the converter. Diodes D312 can be replaced with D310, D311 or any of the D7 series. Instead of K176LA7, you can use the K176LE5 chip.
Author: Semyan A.P.
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