Pulse adjustable voltage converter can work as a boost converter or inverting converter, providing negative voltage.
A specialized pulse controller MC34063 from Motorola was used to create the converter.. This is a universal microcircuit for building simple pulse converters.. On it you can build lowering, boost and inverter converters.
Main technical characteristics of MC34063 microcircuit
- Wide range of input voltages: from 3 V to 40 AT;
- High output pulse current: to 1,5 BUT;
- Adjustable output voltage;
- Converter frequency up to 100 kHz;
- Internal Reference Accuracy: 2%;
- Short-circuit current limitation;
- Low consumption in sleep mode.
There are two main application configurations for the MC34063: upconverter, shown in Fig. 1, and converter, supply voltage negative with respect to supply voltage – inverting converter (rice. 2).
Diode D1 protects against reverse polarity of the supply, capacitor C1 filters the supply voltage, resistors R1 … R4, connected in parallel, have a resultant resistance 0,25 Ohm and are used as a current control circuit. capacitors C2, C4 and choke L3 filter the output voltage, potentiometer R8 allows you to adjust this voltage, resistors R5, R6 set the regulation range, and the capacitance C3 determines the operating frequency. L1 elements, D3 и L2, D2 are required for stable operation of the converter.
Stabilization of the output voltage for the first option is possible in the range U0 … 24 AT, for the second option in the range -1.3 …– 24 AT. The upper limit depends on circuit load and supply voltage. when the load 100 mA boost converter allowed to reach voltage 24 V when powered 5 AT, and the inverting converter reaches a voltage of about –20 V (–24 V when powered 6 AT). In both cases, the microcircuit was slightly heated, therefore do not exceed the output current 100 mA. In theory, the system works correctly from 3 AT, in practice even at slightly lower voltage.
When powered by two AA batteries, the voltage 12 V was achieved with a load current of approximately 50 mA. Moreover, if you connect two circuits of different configurations to one power source, you can get a balanced power supply, For example, ± 24 AT.
The DC / DC converter circuit board on MC34063 is shown in Fig.. 3.
Author: Damian Sosnovski