Laboratory Power Supply Symmetrical 0-40V 4A 0-20V 0-8A

Regulated power supply can be adjusted between 0.20 Volt 8 Ampere or 0.40 Volt 4 Ampere according to the selection. Current limiting between 0V and 20V 2mA..8A. High output voltage, i.e. current limiting between 0V and 40V, 2mA – 4A

Since the linear voltage regulation method is selected in the Laboratory Power Supply design, there is a secondary voltage selector in the circuit. For example, when there is a 40V input and 10V is adjusted, the regulator will remain at 30V. In general, current consumption (for example 4A) means a significant amount of power converted to heat (120W), This causes large losses and especially loads the power transistors.

The voltage selector allows two transformer windings to be connected in parallel or in series. Additionally, by connecting the windings in parallel, you can draw twice as much power from the source at lower range. This connection allows switching between 0 – 20V and 0 – 40V ranges.

The connection control of the output terminals and the output voltage selection are performed using relays. Circuits based on the NE555 timer are used to use push-buttons. In addition, the status of the buttons is indicated by LED indicators.

Another auxiliary circuit is Soft Start for transformers. The task of this circuit is to delay the connection of transformers to the network (via resistance). The reason is; It is to limit the current loop caused by the saturation of the transformer core and the aini charge of the capacitor. The Soft Start circuit provides a delay of approximately 2 seconds.

There is also thermal protection for the power supply. When the lower set temperature is reached, the cooling fans operate, and if the set temperature is excessive, the soft start stage is disconnected from the network. The power stage is disabled, but other circuits operate. When the temperature falls below the set limit, the source returns to normal mode.

The basic element of thermal protection is the LM358N opamp integrated circuit. It is possible to determine a separate switching limit temperature for each. The first of the comparators switches the fans via a transistor, the second via a relay with contacts.

Symmetrical laboratory power supply There are AutoCad 2014 case drawings and PCB, schematic drawings prepared with EagleCad. The document includes connection expansions between pages 73-74. In addition, there is a lot of information such as measurement graphs etc. It is a very high quality linear power supply.