DC-DC converter on an integral timer, 12/40 volts 1 ampere. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Voltage converters, rectifiers, inverters
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When choosing a DC-DC converter circuit, specialized microcircuits are now usually used, of which a great many are currently being produced. And yet, not being able to purchase the required specialized DC-DC chip, you can assemble it on a general-purpose element base, for example, by making a PWM pulse generator circuit on an affordable NE555 chip (integrated timer) or its numerous analogues.
When powered from a 12 V source, a voltage of up to 40 V can be obtained at its output. The value of this voltage depends on what stabilization voltage VD2 is designed for.
The supply voltage is supplied to the A1 timer, on which the pulse generator is assembled. The pulses are fed to the key on a powerful field-effect key transistor VT1, in the drain circuit of which the inductance L1 is turned on. EMF arises on the inductance, which is rectified by the rectifier on VD1.
The stabilization circuit consists of a transistor VT2 and a zener diode VD2.
This circuit works as a comparator, for which the reference voltage is the stabilization voltage VD2. As soon as the voltage at C4 exceeds the value of the sum of the stabilization voltage VD2 and the opening threshold VT2, the transistor VT2 opens, which leads to a decrease in the duty cycle of the pulses at pin 3 A1. Thus, when using the KS539G zener diode, the output voltage is maintained stable at 39,8 V.
Coil L1 is wound on a ferrite ring with an outer diameter of 18 mm, contains 20 turns of PEV wire 0,56.
The maximum output current is 1 A. When working with the converter, it must be taken into account that there is no overcurrent protection in its circuit.
Literature
- Radioconstructor 2008 №5
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