The proposed device, in addition to good technical characteristics, very attractive in that it is based on the switching power supply end the term IBM-compatible personal computer. This eliminates the need to purchase many of the specific radioactive elements, manufacturing pulse transformers and chokes.
Describe the unit allows you to power stabilized voltage Amateur radio construction and charge different stable current rechargeable batteries.
The PSU is equipped with a digital scale for indication of output voltage and current the load has regulators output voltage for coarse and fine setup, the regulator limits the output current, the maximum current indicator, fuse to protect the output circuits in case of wrong polarity the inclusion of a rechargeable battery.
Schematic diagram of the device depicted in Fig. 2.55, where BP PC" -switching power supply unit of the computer; "Prefix" - a display device with the node stabilization of the load current.
Fig. 2.55 (click to enlarge)
Main technical characteristics.
- input voltage, V.....110-220;
- stabilized output voltage, .....5-15;
- voltage ripple at a current of 5 A, mV, not more.....25;
- output constant current, And.....1-10.
In the power supply of the computer is necessary to make some changes. The management node is usually performed on a specialized chip (CHI-controller) TL494 or its equivalents MW, CA, CREW.
On pin 1 of the chip is filed with the feedback signal from the output rectifiers stress+5 V and+12 V, and the output 2 is exemplary voltage from internal regulator output 14. The feedback from the voltage source to "+5 V" should be disabled by removing resistor R4 (hereinafter the numbering of the elements of the conditional), and R6 and R8 to replace resistors indicated in the diagram of the values.
Together with a variable resistor R1, they form a voltage divider return communication, thus making it possible to adjust (coarse) output voltage of the block. The exact value is set by the variable resistor R2, is connected to pin 2 CHI-controller.
The power supply has a built-in fan is powered from a voltage source 12 V. since the output voltage will vary within wide limits, fan you need to connect through the quenching resistor R7 to the rectifier feeding SHIH-controller not changing a voltage of about 24 V.
To the output of the "+ 12V" you need to add a resistor R5, which will ensure sustainable the operation of the power supply at no load at low output voltage. It is also desirable to swap the rectifier diodes sources "+ 5 V" and "+ 12 In", because in the first one used a more powerful diodes.
The regulator output current is collected by operational amplifier DA1. On his reinstitute input voltage with resistor R17 included in the negative lead of the output circuit of the power supply.
To the inverting input DA1 comes exemplary voltage with AC resistor R4, which specify the level of constant current. Resistor R9 and the capacitor C2 in the circuit of the EP, covering the shelter, provide resiliency this host. Through the diode VD1 feedback voltage is fed to pin 3 CHI-controller.
HL1 led indicator maximum current, it glows with a load current, close to or equal to the specified value.
Measuring voltage and current is made to the ADC DA3 included in the model scheme, and digital indicators HG1-HG4. Operation mode select switch SA1. The contact group SA1.1 commutes measured voltage, SA1.2-commas a digital scale.
In the switch position "U" at the ADC input receives the output voltage power supply through a fuse F1 and a resistor divider R11-R13, thanks what if the blown fuse indicator shows 0 V. In control mode, the current (the switch is in position I), the ADC measures the voltage drop across the current sensor - the resistor R17.
The voltage of the "+ 5 V" stable integral stabilizer DA1, voltage "-5" - parametric stabilizer VD3, R8, connected via diode VD2 to the rectifier negative voltage pulse block.
Adjustment of the device
The establishment of the PSU to start with check throttle limits the output voltage (switch SA1 - in the "U") according to an exemplary the voltmeter. The current stabilizer at this time, shut off, hotpaw wire coming from output 3 of the circuit Board to the conclusion 3 CHI-controller. If necessary, adjust the limits the selection of resistors R4 and R8. Then to the unit connect the load with a current consumption of 5 to 10 And, translate the switch to position "1" and the exemplary ammeter trimmer resistor R12 install the necessary indication. Further, by switching the light on the measurement of voltage, adjusting his testimony according to an exemplary voltmeter set by resistor R9.
After that restore the feedback circuit of a current stabilizer switch the indicator on the current measurement and by changing the load resistance, convinced the health of the stabilizer. If necessary, the boundaries of the interval the current control set selection of resistors R1 and R4.
At a load current of 15 A and a voltage of 15 V can be somewhat increased heating winding of the inductor L2 in the pulse power supply. This disadvantage can be eliminated, means of winding the winding wire is twice larger cross section.
When charging the battery batteries stable current install regulators R1 and R2, the voltage charging is complete, and then by connecting the battery, variable resistor R4 is the required current. During the charging light should be on led HL1. Upon its completion, when the voltage on the battery increases to a predetermined value, the current decreases, the led will turn off and the power supply will go into stabilization mode voltage, in which it may be a long time. Thus, there is no the need to control the charging process and the time it is finished, no need to disconnect the battery after charging.
Details
Details of display device with the node of the constant current load with variable resistors R1, R2, R4 and sockets X1 and x2 are mounted on a printed Board (Fig. 1.1), fastened with threaded posts and screw on the front the wall of the block. On it (for PCB) installed without insulation strip integral voltage regulator DA1.
The power supply used fixed resistors MLT, variables SDR-9a, rigged SDR-38.
The resistor R3 is made of three wire segments of the wire 1 and length of about 50 mm, bent in the form of U-shaped staples and soldered to corresponding to the printed conductors of the Board. The deviation of the resistance of this resistor from the circuit, the values of (0.01 Ohm) should not exceed ± 20%.
Capacitors C1...C3 - C50-35, C9 + C11 - K73-17, and the rest - km.
Diode VD1 - any germanium.
Operational amplifier DA2 - CRUD with any letter index, CRUD.
Digital indicators HG1 - HG4 - ALSB, ALSSS, ALSB.
Switch S A1 - button compact circuit Board or B170G similar.
Fuse F1 is a flat road at a current of 10 A.
Author: I. P. Shelestov