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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING Reduced power 190-stroke inverter, 230-6/27-6 volts XNUMX amps. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Voltage converters, rectifiers, inverters A push-pull half-bridge pulse inverter with small dimensions is used as a power source and for charging batteries. The reduced inverter supply voltage implies the use of key transistors with a low operating voltage in the circuit. Batteries are charged at a stable voltage. Passport charge current of the battery is reduced by the end of the charging cycle to the state of buffer charging. The inverter provides:
The resulting DC voltage is used to charge batteries or power loads (electronic circuits, electric motors, etc.). Reduced inverter power allows the use of key transistors with low nameplate voltage and reduces conversion noise. The inverter circuit is equipped with two regulators: current and voltage. The network noise filter consists of a two-winding inductor T2 and capacitors C13, C14. The filter reduces noise from the inverter entering the network and eliminates impulse noise from the network. Fuse FU1 and switch SA1 are installed in front of the filter. After the mains voltage rectifier VD4 and the smoothing filter on the capacitor C12, a constant voltage is supplied to the transistor filter-stabilizer R15 VD2-VT3. From the emitter VT3, the reduced voltage is determined by the stabilization voltage of the zener diode VD2. used to power the inverter. It is additionally smoothed by capacitors C8 and C9 with shunted resistors R12 and R13 to equalize the voltage relative to the midpoint. Thermistor RK2 limits the charge current of the filter capacitors when the mains voltage is applied. The primary winding of the high-frequency transformer T1 of the inverter with one output is connected to the midpoint of the capacitors C8 C9. and the second output (through a separating capacitor C7) - to the connection point of the power transistors VT1, VT2 of the key converter. The R14-C11 chain suppresses parasitic RF oscillations in the transformer windings after the end of the pulse. The separating capacitor C7 eliminates the magnetization of the magnetic circuit of the transformer T1 with a spread in the parameters of the capacitors C8 C9 and transistors VT1, VT2, and also allows the use of a transformer without a gap in the magnetic circuit. From the gain of transistors VT1, VT2 depends on the current switching speed and control power loss. The input RC circuit R7-C4 protects the inverter from the occurrence of through currents and accelerates the passage of pulse fronts to the bases of transistors When power is applied to the generator, output 3 DA1 is set to a high level for a time depending on the ratings of R1, R2 and C1. The appearance of a positive pulse on the bases of transistors VT1, VT2 leads to the opening of the transistor VT1 and the closing of VT2. Capacitor C7 in the diagonal of the bridge, charged through an open transistor VT2 with voltage from the midpoint of capacitors C8, C9. discharged through the transistor VT1 In the primary winding of the transformer T1, a current pulse occurs, which is transformed into the secondary winding. When the generator is switched and a low level appears at output 3 DA1, the transistor VT1 closes, and VT2 opens. On the capacitor C7, the polarity of the voltage changes, and a reverse current occurs in the primary winding of the transformer T1. The impulse voltage from the primary winding of the transformer T1 is transferred to the secondary (taking into account the transformation ratio), rectified by the high-frequency bridge VD3 on avalanche diodes and smoothed by the capacitor C10. The pulse generator is made on an analog CMOS timer DA1 with minimal power consumption. It is not recommended to use the KR1006VI1 timer due to the increased current consumption. The DA1 timer chip contains two comparators connected to inputs 6 and 2, an RC flip-flop output amplifier and a key transistor at pin 7 to discharge an external timing capacitor. Chip DA1 operates in multivibrator mode. When charging the capacitor C1 to a level of 2/3 Upit at output 3 is a high level. After reaching this level, the internal trigger DA1 sets a low level at output 3, opens the key transistor, and capacitor C1 is discharged through it and resistors R2, R3. After discharging C1 to the level of 1/3 Upit, the internal trigger switches the outputs 3...7 DA1 to its original state. The cycle is repeated. The output voltage from the capacitor C10 through the thermistor RK1 is supplied to the variable resistor R11. the engine of which is connected to the control input of the parallel voltage regulator DA2. The DA2 stabilizer is included in the VU1 optocoupler LED circuit. When the output voltage rises, for example, due to an increase in load resistance. DA2 opens more strongly, the current through the VU1 LED increases, the optocoupler transistor opens and shunts the voltage at the 5DA1 control input. The frequency of the generator is reduced without changing the duty cycle of the pulses, which leads to a decrease in the output voltage, that is, to its return to the set value. With a decrease in the output voltage, the described process occurs in reverse. Details. The diode assembly VD4 must be for a voltage of at least 400 V and a maximum current of at least 3 A. A low-voltage rectifier VD3 - for a voltage of at least 50 V and a current of at least 20 A. Transistors VT1 and VT2 - of different polarity with the closest possible parameters. Collector-emitter voltage - not less than 90 V and current - not less than 3 A. Transistors are installed on a common radiator using gaskets and heat-conducting paste. The RK1 thermistor is attached to the heatsink with a bracket with a gasket and connected to the printed circuit board with flexible wires in insulation. Optocouplers are suitable from the LTV816, PC817 series Inductor L1 is taken from the power supply of the YX EE25-01 computer or is made on a ferrite ring with a diameter of 24 ... 36 mm. The winding contains 14 20 turns of PEL wire 0,8 mm. Transformer T1 type KR4127, ERL35 2, E1-28 is used without modification from the computer power supply. It is wound on a core measuring 10x8x22 mm. Winding 1 T1 contains 38 46 turns of wire 0,6 mm, windings 2 and 3 have 7,5 turns each, made with a bundle of 4 wires 0,27 mm (to reduce losses from the surface effect). The details of the device are placed on a printed circuit board, the drawing of which and the layout of the elements are shown in Fig. 2.
The board is installed in a plastic case of the BP-1 type. Remote elements are mounted in the holes of the case and connected to the board with insulated wires of a suitable section (control wires - 0,5 mm2, power wires - 2 mm2). Before turning on the assembled circuit for the first time, it is necessary to turn on the light bulb (220 V 100 W) in the break of the mains supply circuit. This will protect the device from failure if there are errors in the circuit or low-quality parts. A weak glow of the mains light bulb at idle and an increase in its brightness when the load is connected indicate the normal state of the circuit. At the end of the control check, the light bulb is removed, and the converter is connected to the network without current limitation. Inverter tuning is best done with an oscilloscope. It is necessary to check the presence of rectangular pulses at output 3 DA1 and pulsed voltage on the windings of the transformer T1. By selecting resistance R8 at the junction point of the emitters of transistors T1 and T2, a voltage equal to half the supply voltage is set The load current is visually set by the ammeter RA1 by the current regulator - resistor R2. output voltage - resistor R11 As an active load during commissioning, you can use a car light bulb (12 V, 30 ... 50 W) To operate the inverter as a charger, resistor R11 with the middle position of the slider R2 sets the output voltage to 14,2 V by resistor R2 - the required charge current (within 0,05 battery capacity). The charge time usually does not exceed 5-6 hours, the end of the charge is controlled by reducing the charge current to almost zero. Attention! During testing, the safety regulations must be observed. Authors: V.Konovalov, A.Vanteev, Creative Laboratory "Automation and Telemechanics", Irkutsk Center "Energy Saving Technologies", Irkutsk
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Comments on the article: Varangian-61 Will not work. The timer will fly out immediately - and along the VT2 chain, etc. Fedyun Thank you very much for the description and diagram, I have been looking for it for a long time. Just what you need, thanks. [up]
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