I have a regulated power supply. Only voltage is regulated; therefore, there is no current regulation. For some purposes it is enough. I decided to assemble a unit with current and voltage regulation. A laboratory power supply, or LBP, is a very necessary thing.
The LBP circuit is very simple, as I will use DC-DC converter module from China.
Characteristics
Main characteristics of the module:
- Input voltage 5 - 40 Volts;
- Output voltage 1.2 - 35 Volts;
- Output current (max) 9 Amperes, it is advisable to install a cooler.
Power supply diagram
As I already said, the scheme is simple. The mains voltage is supplied to the transformer. There is a power switch and fuse. The voltage is stepped down by a transformer. The top honor of the power circuit. Alternating voltage is supplied to the diode bridge and smoothing capacitor. Next it goes to the DC-DC converter. From the converter, voltage is supplied to the output terminals. The minus of the circuit is broken by the device. For convenience, the adjustment resistors are removed from the board.
The lower one is designed to power the voltammeter. The transformer has a separate winding.As with the power winding, alternating voltage is supplied to the diode bridge and filter capacitor. Next, I installed a 5 Volt linear stabilizer.
Components
We figured out the scheme. Now let's move on to the components.
The body of the LBP will be the old body from the soldering iron regulator. The soldering iron regulator dates back to USSR times. Very kind.
The front panel will be made of composite plastic. The plastic consists of two aluminum plates and plastic between it. On the one hand it is white, on the other it is black. The black side will be the front.
A step-down transformer from old equipment, I don’t remember which one. It had to be slightly modified. I made a tap at 22 Volts, a full winding at 27 Volts. If left, then after the diode bridge the voltage is more than 30 Volts. This is a lot for a 7805 regulator installed on a [leech=http://]DC-DC converter[/leech]. It powers the op-amp circuit. Although 40 Volts are stated, taking into account the maximum for 7805 at 30 Volts.
DC/DC Buck Converter.
3-segment voltammeter. For a more accurate display of output parameters, you need to apply it to 4 segments. I had the one I had and used it.
Terminals from the times of the USSR. Strong and reliable.
Capacitor 4700 microfarads * 63 Volts. Based on 1000 microfarads per 1 Ampere. Another 2*470 uF are installed on the module.
You can use a single diode bridge, but I still have it from an old project. Assembled on 4 D242 diodes.
Manufacturing
At the bottom of the case we mark and drill holes for: transformer, diode bridge, module. We solder everything according to the circuits. I removed two trimming resistors from the module. I soldered wires instead. There are 3 wires for current, two for voltage.
I will power the Voltammeter through a 5 Volt linear stabilizer.Diode bridge KTs402 and a small capacitor.
On the back panel I make markings for the power connector and fuse. I carefully cut everything out and install it.
I mark and cut out all the holes on the front panel. There will be: output terminals, mains switch, current and voltage resistors, Volt-ampere meter.
I soldered all the elements installed from the inside. The power switch switches both network wires. Initially I wanted to use another one.
We install all the elements of the front panel. The positive terminal is marked with red paint. Resistor handles of different colors. Red is the color of the Volts display. Yellow in current. I have not yet signed where the current and voltage are. Later I will change the resistors to multi-turn ones, and perhaps change the handles too.
I painted the top cover. There was too big a gap between the front panel and the lid; it was closed with a small corner. When tested, the unit produced 9 Amperes on short, at 28 Volts, which amounted to a little more than 250 Watts.
This is how the Laboratory Power Supply turned out. They can power various types of devices and also charge batteries. Initially I wanted to use a 24 Volt pulse source, but I came across a transformer of the required dimensions. Also, I try to assemble a device from what I have. Thank you all for your attention!
