LPS Power Supply

Version 1 by Stephane Carrez


The power supply controllers and the master power supply board need themselves a power supply. To drive the output power supply transistors a specific power supply is used. By doing this it decouples the interactions of the power supply loads on the voltage regulator.

LPS Power Supply

Positive Power Supplies

We have the following needs on the positive supplies:

Negative Power Supplies

We have the following needs on the negative supplies:

Master Controller

LPS Power Supply Regulation

To obtain the LPS power supplies we use the toric transformer of the positive power supply. The +24V and -24V are obtained by a voltage multiplier from the 2x9V toric transformers. In theory it can reach 36V so the decoupling capacitor is chosen to support at least 50V. The voltage multipliers use 1000uF electrolytic capacitors and the voltage rippling can be approximated to: \Delta V = \left ( \frac{i * \Delta T}{C} \right ) which should be arround 0.4V if we assume that the output current is less than 40mA. On the other hand the maximum rippling being arround 8V, the time is given by the formula \Delta T = \left ( \frac{C * \Delta V}{i} \right ) which gives us arround 200ms during which we will continue to have a stable +24V/-24V.

LPS Power Supply Summary

Positive Power Supply Rectifierxx
Negative Power Supply Rectifierxxx
Positive Voltage RegulatorXX
Negative Voltage RegulatorXX
Positive Power Supply ControllerRXXX
Negative Power Supply ControllerXXXR
LPS Master ControllerXX
LPS LCD Panelxx

The following tables indicates the maximum current rating for the boards and for each power supply.

+24Positive Power Supply RectifierAnalog10mAAnalog power supply for operational amplifiers.
Positive Voltage RegulatorAnalog20mA
+9VNegative Power Supply RectifierAnalog10mA
Negative Voltage RegulatorAnalog20mA
Positive Power Supply ControllerAnalog30mA
Negative Power Supply ControllerAnalog30mA
+5VPositive Power Supply ControllerDigital80mA
Negative Power Supply ControllerDigital80mA
LPS Master ControllerDigital250mA
LPS LCD PanelDigital100mA
-5VPositive Power Supply RectifierAnalog50mAUsed by the AOPs and the relays.
Positive Power Supply ControllerAnalog20mAUsed by 2 TL074
Negative Power Supply RectifierAnalog50mAUsed by the AOPs and the relays.
Negative Power Supply ControllerAnalog50mA
-24VNegative Power Supply RectifierAnalog20mA
Negative Voltage RegulatorAnalog20mA


LPS Power Supply
LPS Power Supply


LPS Power Supply PCB Placement
LPS Power Supply PCB Placement
The LPS power supply placement board is 102mm x 80mm wide on a single sided 35um copper board. The placement of VPOS_UNREG and VNEG_UNREG are not the best we could find as they are more or less in the middle of the board. They were added quite late, after all the schema was successfully routed on the single sided board.

LPS Power Supply PCB
LPS Power Supply PCB
For the auto-layout the following class have been used in Eagle:

Signal classWidthClearanceDrill
Signal and others0.8mm0.3mm0.8mm

LPS Power Supply PCB Picture
LPS Power Supply PCB Picture


Below is a collection of datasheets, white papers and articles related to the parts used in the board.