Every Amateur radio operator, engaged in the development and repair radio equipment, would like to have in his laboratory, universal power supply, that is, on all occasions. Such a source should be adjustable in wide range output voltage, high current, high stability voltage, low ripple, safe protection (overcurrent, over voltage and over temperature), ensuring safety as fed equipment and the source. The power supply should be simple and not contain scarce, expensive and bulky components.
Attempts to find the description of finished devices meets the above the requirements were unsuccessful, so the author had to develop such block independently. What came out of it, judge for yourself.
The focus in the development of the proposed laboratory power supply (PSU) was paid to the security node. According to the author, to ensure maximum reliability of electronic and Electromechanical protection should be applied in complex.
In the described BP implemented nodes on the supply voltage, excess voltage on the output, as well as heat.
To protect against electrical damage to radios in a wide range the load current, current protection shall be adjustable. In the process of developing there were some difficulties with the implementation of the current sensor. Classic embodiment is a resistor which is connected in the power circuit, the voltage drop across which monitors the management node protection. To implement adjustable the current sensor would highly variable resistor high power resistance from a few to tenths and even hundredths of an Ohm. For example, when the resistance of the current sensor of 0.1 Ohm and a current of 15 And it dissipates more power 20 watts! There is the option of switching resistors, but in this case the switch must withstand the maximum load current. In addition, the contact resistance of the switch is unstable and commensurate with the resistance switchable resistors, therefore, the threshold will be unstable, and the switch itself is very cumbersome. Of course, you can use a constant resistor of very low resistance and exacerbate the fall voltage regulated DC amplifier, but in this version the device is much more complicated.
The decision came after reading the article [1] and is as follows: case reed relays RES-55 is wound an additional winding that include in the power circuit of the PSU to the stabilizer. The direction of the current in the primary and additional windings of relays are chosen so that they create a magnetic field were summed up. Then, changing the current in the main winding, it is possible to adjust the level the tripping current protection BP.
In the nodes of protection against excess voltage at the output is usually used powerful a Zener diode or SCR, which is at a higher voltage and open close the output of the PSU. As a result of a sharp increase in current is triggered the fuse installed in the power circuit.
In the proposed host protection against over voltage on the output in BP entered additional low-power stabilizer with the same law regulation output voltage as that of the primary stabilizer. The output voltage additional stabilizer should be slightly larger than the main the stabilizer. Both voltage serves on the simplest node comparison. The excess the voltage at the output of the main regulator triggers the protection.
Node thermal protection built on the switches.
Main technical characteristics of BP:
- The intervals of the output voltage regulation, In......1,2...15; 1,2...30
- The maximum load current (in the range of 1.2 To 30 guaranteed if the voltage 15...30 V), AND......15
- The stabilization factor for voltage not less than.....100
- The level of ripple in the output voltage of 12 V and a load current of 10 A, mV, not more......30
- The throttle current protection operation, And......0,5...15
- Output over voltage at which protection is triggered, not more......2
- The temperature fan switch cooling, °C......50
- The temperature of activation for thermal protection, °C......60
The BP scheme shown in the figure. From the secondary winding of the transformer T1 network alternating voltage is supplied to the rectifier bridge VD1. The intervals of the output voltage switch jumper S1: in the circuit on the position - 1,5... 15 V; in the right - 1,2...30 V. the Capacitors C1 - C4 reduce multiplicative noise. The rectified voltage is smoothed by capacitors C6-C9, arrives at the inputs of primary and secondary stabilizers, which are assembled on chips and DA3 DA1 included in the model scheme [2]. To increase the output current of the main stabilizer applied regulating transistors VT1-VT4, in the emitter circuits which has takavarasha resistors R9-R12. Diodes VD2, VD3, and VD10 VD11 - protective. The output voltage of primary and secondary stabilizers regulate dual variable resistor R2. Resistor R3 sets the minimum voltage of the additional stabilizer over voltage the main things necessary for the proper operation of the node protection.
(click to enlarge)
The output voltage of the PSU is measured by a voltmeter PV1, and the output current of the ammeter RA1.
To improve the stability of the node on the supply voltage fed from the stabilizer DA2. Resistor R4 regulate the current in the primary winding 1 -2 reed relays K1, the result of varying the operating current of the supplementary winding 3-4. If output current PSU exceeds the set value, the relay K1 will work, contacts K1 1 will activate the relay K2 and it locks automatically through the diode VD8. Relay K2 will work contacts K2.1 shut off the main stabilizer from the rectifier. The color glow HL1 led will change from green to red and an audible alarm (acoustic radiator 1 with a built-in generator). Sound the alarm can be disabled by the switch SA3. After removing the cause tripping current PSU is returned to the original state by clicking on the button SB1 "Reset". Diode VD7 and VD9 limit the voltage of self-induction of the windings relays K1 and K2.
In the node comparing the voltages of the main and additional stabilizers applied triac optocoupler U1. Voltage stabilizers are served on emitting diode optocoupler, which in the initial state is closed. If the output voltage the primary stabilizer for any reason will increase the thyristor optocoupler will open that will lead to protection as described above. Diode VD4-VD6 protect emitting diode of the Photocoupler overload, and the resistor R8 limits the current.
Thermal protection is made on the thermal switches SF1 and SF2. Switch SF1 triggered when the heat sink temperature has reached 50 °C, and includes fan motor M1. If the heat sink temperature continues to grow at 60 °C will switch SF2 that will enable protection. Fan motor M1 can enforce switch SA2.
The main element that determines the electrical parameters and the dimensions of the PS - network the transformer T1. The author used ready core transformer with an overall with a power of about 600 W, having a secondary winding with an output voltage of 30 V with an average output. In PSU you can use any transformer with necessary characteristics.
Diode bridge MV (VD1) will replace any rectifier series MB or SWРС. In extreme if the bridge can be assembled from individual diodes that provide the needed current load.
Switch intervals of the output voltage S1 is made of three instrument terminals, connected by a bridge.
Stabilizers CREA interchangeable with any of the series or imported analogues series SD1083 DV1083, LT1083, SD1084, DV1084, LT1084, and stabilizer CREB - import analogue of the 7812.
Relay K1 - RES-55B performance RS4.569.600-00 (passport RS4.569.626). Suitable also relay performances RS4.569.600-05 (passport RS4.569.631), RS4.569.600-01 (passport RS4.569.627) and RS4.569.600-06 (passport RS4.569.632). If the relay does not triggered when the voltage of 12 V, the voltage DA2 need be increased to a reliable relay (with a margin of 1.5...2), inserted between the pin 2 of the chip and the common wire one or two low-power silicon diode Conclusion the housing of the relay removed. In the case of the relay coil additional winding wire PETV (sew). When you select the wire diameter should focus on density current 10 A/mm In the author's version additional winding has 16 turns wire with a diameter of 1.4 mm. Winding fixed with heat shrink tube. Estimated the resistance of the winding is 0,006 Ohms, the voltage drop at a current of 15 A - 0,09 V, the maximum power dissipation - 1.35 watts. Relay K2 - automotive 90.3747-01, capable of switching currents up to 30 A. thermal switches SF1 and SF2 RB-2 with a temperature of 60 °C, previously widely used in UCS. One switch is adjusted at a temperature of 50 °C. thermal switches can be replaced imported V at a suitable temperature, but because their normally closed contacts, they must be enabled through the inverters. The motor M1 is a fan used for cooling of power supplies IBM PCs.
Led ALSA (HL1) it is permissible to replace imported dichroic or any two single color (red and green respectively). Transistors CTHM (VT1-VT4) interchangeable powerful p-n-p transistors with a maximum power dissipation is not less than 100 watts, for example, from the series CT, CT, CT.
Resistors R9-R12 is C5-MW power of 2 watts. You can replace homemade, made of nichrome wire with a diameter of 0,8... 1 mm. you Can do without these resistors, if you pick the transistors on the equality of the currents collectors when equal voltages base-emitter.
For reasons of reliability applied wirewound variable resistors PPV-45 (R2, R4) and multi-turn trimmer resistors-SP5-SV (R3, R5, R13, R17), but their you can use any. Diodes KDA (VD3-VD8, VD11) any interchangeable silicon low-power, and diodes KDA (VD2, VD9, VD10) - all with a maximum current of less than 1 A.
To measure the voltage and current measuring head used M resistance 500 Ohms with a current total deviation of 1 mA. The use of other measuring heads will require recalculation of the resistors R13, R16, R17.
Capacitors C6-C9 - C50-37, but it is permissible to use any other. Should remember that the total capacitance should be at least 2000 µf for each amp load current, a rated voltage exceeding the output voltage rectifier with a maximum supply network voltage.
Capacitors C5, C10-C12, C14 - tantalum K52-1, K52-2 and K53-1A. In the case of the use of aluminum oxide capacitors, their capacity should be increased in several times. The remaining capacitors - all-ceramic.
The switch SA1 - T2 or the other, with a current capacity of at least 3 Switches A. SA2, SA3 - MT, button SB - 1 km-1, but they can be replaced by any other.
Instead of a triac optocoupler AOA permissible to use any from the optocoupler AO.
BP is assembled in a rectangular metal case dimensions 230x120x300 In mm. top, bottom and side panels of the casing drilled ventilation holes. On the front panel is equipped with measuring instruments, terminals, terminal blocks switch intervals of the output voltage, the power switch, switches blower motor, common alarm output regulators voltage R2 and current tripping R4 and led alarm tripping.
Back panel is made of aluminum of a thickness of 3 mm it through mica strip, coated on both sides with a paste KPT-8, fixed to the transistors VT1-VT4, circuits DA1-DA3, rectifier bridge VD1 and thermal switches. Fan installed on the rear panel above the transistors VT1-VT4 on the racks. In free the ground beneath drilled ventilation holes. The rear panel also submitted fuses FU1 and FU2.
Mounting the unit mainly hinged on the findings and insulating supports. Installation power circuits performed stranded wire 2.5 mm2 minimum length. Capacitors C6-C9 screwed contacts to the Board of foil fiberglass, which is attached to the side panel brackets. On the printed the conductors between the terminals of the capacitor along the entire length of soldered copper wire the diameter of 1.4 mm. Transformer mounted on the bottom panel using the corners.
The establishment of BP is reduced to adjust the node's protection and calibration of ammeter and the voltmeter. This will require a voltmeter with a limit of measurement 35, ammeter with a limit of measurement 20 A, an auxiliary regulated power supply with the maximum output voltage of 35 V and variable load resistors (rheostats) resistance 10 and 100 Ω or equivalent load. Node protection adjust in the following sequence.
1. First regulate the protection node from exceeding the output voltage.
1.1. The slider of the variable resistor R4 is set to the maximum resistance.
1.2 Connect the voltmeter positive to the positive output to the output of the stabilizer DA1 and negative - to the output of the stabilizer DA3.
1.3. Changing the output voltage of the PSU within the intervals 1 2... 1,2...15 and 30 In using the resistor R3 are making to the measured voltage was always positive, and its value is a minimum and not greater than 1.5 V. If this could not do that, you should swap the resistors R2.1 and R2.2 or pick up resistor R2 with a smaller misalignment.
1.4. Set the output voltage of 30 BP In
1.5. Disable right circuit output resistor R8 from the output of the PSU and feed on him voltage (a few less 30 In) from the auxiliary source.
1.6. Gradually increasing the voltage of the auxiliary source, capture the moment tripping on the color change of the illumination of the led. The output voltage auxiliary source in this case should not exceed 32 V.
1.7. Reconnect the resistor R8 to the output of the PSU.
The serviceability of protection against excess voltage can be checked and in the process operation. The capacitance of the capacitor C12 primary stabilizer DA3 more capacity of the similar purpose of the capacitor C5 in additional the stabilizer DA1. Increased capacity helps to reduce the ripple the output of the main regulator, but also increases the inertia adjust the output voltage of power supply. If the engine resistor R2 to turn sharply in the direction of decreasing voltage, due to the larger capacity of the output voltage BP short-term will exceed the output voltage DA1, which will lead to the protection is activated.
2. Then adjust the node on the supply voltage.
2.1. Break the chain between the resistors R4 and R5, between pin 4 additional winding of the relay contacts K1 and K2.1 relay K2.
2.2. Between pin 4 of the additional winding of the relay K1 and the common wire connected serially connected to a load resistor of 10 Ohm and the ammeter.
2.3. Reducing the resistance of the load resistor to measure the current response protection that should be in the range 16... 18 A. This is achieved by changing the number of turns of the additional winding 3-4 of relay K1.
2.4. Restore the connection of resistors R4 and R5. A load resistor resistance of 10 Ohms replace the 100 Ohm.
2.5. The slider of the variable resistor R4 is set to the minimum resistance, and a trimming resistor R5 and a ceiling of resistance.
2.6. Changing the load resistance, establish a current of 0.5 A.
2.7. Moving the engine tuning resistor R5, achieve actuation protection.
2.8. A load resistor of 100 Ω is replaced by 10 Ohms. The slider of the variable resistor R4 is set to the maximum resistance.
2.9. Changing the resistance of the load resistor to measure the current response protection. If the value differs from 15 And will require the selection of resistor R4.
2.10. Setting multiple values of load current, graduate scale variable resistor R4.
2.11. Disconnect the load resistor and an ammeter. Reconnect between pin 4 of the relay contacts K1 and K2.1.
Ammeter and voltmeter is calibrated by the standard technique. Note that the scale ammeter - linear.
In conclusion, it should be noted that similar site security or its individual elements can be equipped with almost any BP.
Literature
Author: E. Kolomoets, Irkutsk