Presents the PSU has the ability to change the voltage turning the resistor R9 from 1 to 32 volts, it is protected from overloading and the power required for all Amateur radio experiments. Load capacity on all ranges does not exceed 6 amps.
The power supply has a voltage and galvanic isolation with 220V. This power supply was made by me and my friends and tested in the action. During Assembly and configuration of the power supply unit (PSU) essential dual beam oscilloscope.
(click to enlarge)
Alternating voltage is supplied to the node prevent instant splash
huge current when charging the capacitors C5 and C6 consisting of resistors
R1, R2, R3 relay, RES, transistor, Zener diode XA, condenser
C1 and capacitor with a capacitance of 0.33 μf 250V, diode assemblies on KD105B.
When turned on, the capacitors C5 and C6 is charged through the resistor R3, bramatherium chain of the relay provides the necessary time
for charging high power capacitors C5 and C6, after the capacitor is charged
the relay closes the contacts and the current goes directly, thereby giving the possibility to load
the power source is at full capacity.
The next node is the node of protection from interference power source AC current and into the surrounding space. The housing of the power adapter must be made of metal . He serves as a shield protecting from interference in the surrounding space and shall be earthed.
The building is served pomehoemissii the voltage across capacitors C2 and C3, these disturbances are also rooted in the ground wire. The noise filter in 220V performed on the coil L1 and the capacitor C4.
Power rectifier, made a powerful diode Assembly SWРС1006, she has small dimensions and can withstand a DC current to 10A, and pulse up to 50A. The capacitors C5 and C6 and resistors R3 R4 assembled a voltage divider 2, thereby lowering the voltage in the region of 150 volts, this voltage is applied on power transformer T1 through a capacitor C7 having a small capacity and thereby unleashes a powerful field-effect transistors DC during the switching of the transformer at a frequency of 50 kHz.
Capacitor C7 prevents breakdown of the IRF740 MOSFETs in case of shutdown the master oscillator pulses. High frequency diodes shunt the transformer T1 and the IRF740 MOSFETs protect from high voltage surge of the transformer T1 is not giving the punch transistors high voltage, although the transistors are protected in such a case, but the diodes are faster and more reliable.
The choice of field-effect transistors due to the fact that they have a more rapid indicators rather than bipolar, it is of great importance because transistors have greater instantaneous power during the transition from closed position to an open position. The faster the cycle of opening and closing of the transistors, the more their load the ability to.
Management of field effect transistors fully charged chip IR2113. Field-effect transistors have parasitic capacitance of the drain stopper and therefore possess action decelerates while driving, chip IR 2113 during the management can develop a current pulse of up to 2 amps, thereby providing a rapid saturation of the power field-effect transistors, and also the output from saturation. The resistors connected to the gates of transistors 10 ohms, prevent excessively high current.
Capacitor C18 and a diode CDD serve as a power source Manager node chip IR2113 upper circuit of the transistor IRF740. The amplitude at the gates of the transistors should not exceed 20V 18.. and should not be below 11 volts. The control pulses of the chip IR2113 are received from the pulse width modulator TL494.
This chip due to expansion and contraction of rectangular pulses changes the power delivered to the power transformer, and thereby performs the role of stabilizer and voltage regulator. The control pulses from the output 9 and 10 TL494 is input to the management of the upper transistor 10 IR2113 and bottom 12 IR2113. Load the outputs of the TL494 are two resistors of 1 kω.
The frequency of the master oscillator which operates the power supply capacity is determined by the capacitor connected to the input 5 ТL494 and trimmer, connected to the input 6 of the TL494. Control IRF740 MOSFETs during their work should the pulse be closed, due to the fact that the transistors cannot immediately be closed and thus may receive the pass-through current, when the upper transistor is not fully closed, and the bottom has already started to open and therefore can go direct current directly through the two transistors and thus put them out of action. For that on input 4 TL494 is energized defines this minimum the gap between the pulses.
A capacitor C14 and a trimming resistor of 15 kω create the same offset, allow you to adjust this gap, and the capacitor C14 gradually raises the voltage when you switch the unit to the network. Charged, it reduces the protective gap and increases the width of the control pulses of the transformer T1. You need to check on the oscilloscope? Protective dead gap should not to be lower than the pulse width quarter width himself. The width of the pulses from the outputs of the TL494 is adjusted depending on the voltage in the range from 0 to 3 volts, input 3.
This voltage is applied from the voltage regulator chip TL494 from the outputs 14 and 13, it is 5 V ±5%. Optocoupler, which performs galvanic isolation, it regulates the voltage applied to the input 3 TL494 depending on the voltage of the source output power.
The 680 Ohm resistor in series with the optocoupler and the capacitor 100mkf prevent the initiation of power supply, if this happens we need the values of these parts increase. If excitation occurs, it is possible to load the PSU in any case it is impossible, as it can overload the power transistors in IRF740 the charging time of capacitors C8 C9 C10.
During the excitation the power supply starts to podveshivat and output voltage starts to jump. The rectifier of the secondary winding consists of two diodes, the Schottky they have a speed of 100 kHz and the maximum current up to 30 amps, their type CDA or they can be replaced CD with any letter. First smoothing occurs on the capacitors C8 and C9, C8 high frequencies S9 on low 50Hz, then through the inductor and one capacitor 10. The protection circuit is assembled on the transistors, some resistors and RS trigger, it has great performance. The adjustment of the current operation adjust trimpot resistor R8.
The amplified voltage signal from the transistor VT1 is supplied to the trigger, which when a voltage below 2 volts at the inlet 4 through the transistor includes the coupler PS2501 , 16 which connects the entrance with TL494 +5 V, which leads to the failure of the control pulses. With optocoupler in a 16-input circuit the voltage across the resistor is 10 ohms the diode and capacitor, charged to a voltage of diode saturation of 0.5 volt. The diode in this case needed Kremny, for example KDA, clicking on control button trigger optocoupler is turned off and the power supply unit out of the the overload condition. Inlet 16 TL494 voltage gradually decreases, discharging resistor on 2 kOhm and 10 kOhm and thereby the pulse width begins to increase to the limit, set a variable resistor R9.
Items must be the same as in the diagram. Transformer T1 is made from the W-shaped ferrite MN section H, the height of the window 31mm and a width of 9mm. the Primary winding has a coil 32 from single wires of 0.3 mm sew-2, 8 secondary windings of the individual wires of 0.8 mm sew-2, for the primary General section all lived 1mm, the secondary 2mm.
The secondary winding can be wound and to another voltage 4 volts per coil. The inductor in the output the cascade of the same ferrite and has 20 turns sew-2 1.2 mm. Transformer T2 has power 4...10 watts. On the power transistors need a radiator area of 80 cm2, diodes on the output kasada the same on each.
Author: Radikov E. Y.; Publication: N. Bolshakov, rf.atnn.ru