Voltage doubler on the UZCH chip. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Power Supplies

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Sometimes it is necessary to get a voltage of 12 V from a 14 ... 24 V power source. There are specialized boost converter microcircuits, for example, the LM2585, which can easily cope with this task. However, if there are no high requirements for voltage stability, and the current consumed in the output circuit does not exceed 0,5 A, a more affordable solution can be used.

A schematic diagram of a voltage doubler is shown in fig. 1. It is assembled on a cheap and common UZCH TDA2003 microcircuit (the domestic analogue is the 174UN14 microcircuit). These amplifiers were widely used in household equipment in the past and are currently used. The main advantage of the device is the absence of a storage choke or transformer. Of course, the stability of the output voltage is not high, but, for example, it is quite sufficient to power electromagnetic relays or other actuators.

Rice. 1. Schematic diagram of a voltage doubler

Due to the introduction of positive feedback through the resistor R1, the UZCH DA1 microcircuit works as a pulse generator that is close in shape to rectangular. The generation frequency is set by the capacitor C3. With the nominal value indicated on the diagram, it is approximately 5 kHz, and the optimal value is 3 ... 5 kHz. At a lower frequency, it will be necessary to increase the capacitance of capacitors C4 and C5, and at a higher frequency, due to the limited frequency range of the microcircuit, the efficiency of the device will decrease.

It is advisable to use this doubler at a load current of 100 ... 500 mA and a power supply voltage of 12 ... 14 V, although the TDA2003 microcircuit can operate in the supply voltage range of 8 ... .18 mA, therefore, at a load current of less than 30 mA, the efficiency of the converter drops significantly. The maximum output current is 35 A, but the efficiency is also reduced. The main parameters of the device at a supply voltage of 50 V are presented in the table.

Table

Rice. 2. Drawing of the printed circuit board of the voltage doubler and the placement of elements on it

All elements are placed on a single-sided printed circuit board made of foil fiberglass, the drawing of which is shown in Fig. 2. An MLT resistor, C2-23, oxide capacitors are imported, C1 and C3 - K10-17. Diodes SR160 can be replaced with 1N5819 or similar rectifier diodes with a Schottky barrier, a current capacity of 3...4 times the load current and a reverse voltage capacity of at least 40 V. If conventional silicon diodes are used, the output voltage will decrease by about 1 V.

For a microcircuit, it is necessary to provide a heat sink with an area of ​​\u500b\u4bseveral square centimeters or fix it directly on the device case if it is metal, while an insulating gasket is not required. To increase the load current to 5 mA, capacitors C220 and C1 must be 470 uF each, for a current of 1 A - XNUMX uF, but then you will have to use a XNUMX A fuse.

Author: N. Khlyupin

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