Description

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

	+24V	+9V	+5V	-5V	-24V
Positive Power Supply Rectifier	x			x
Negative Power Supply Rectifier		x		x	x
Positive Voltage Regulator	X			X
Negative Voltage Regulator		X			X
Positive Power Supply Controller	R	X	X	X
Negative Power Supply Controller		X	X	X	R
LPS Master Controller			X	X
LPS LCD Panel			x	x

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

+24	Positive Power Supply Rectifier	Analog	10mA	Analog power supply for operational amplifiers.
	Positive Voltage Regulator	Analog	20mA
+9V	Negative Power Supply Rectifier	Analog	10mA
	Negative Voltage Regulator	Analog	20mA
	Positive Power Supply Controller	Analog	30mA
	Negative Power Supply Controller	Analog	30mA
+5V	Positive Power Supply Controller	Digital	80mA
	Negative Power Supply Controller	Digital	80mA
	LPS Master Controller	Digital	250mA
	LPS LCD Panel	Digital	100mA
-5V	Positive Power Supply Rectifier	Analog	50mA	Used by the AOPs and the relays.
	Positive Power Supply Controller	Analog	20mA	Used by 2 TL074
	Negative Power Supply Rectifier	Analog	50mA	Used by the AOPs and the relays.
	Negative Power Supply Controller	Analog	50mA
-24V	Negative Power Supply Rectifier	Analog	20mA
	Negative Voltage Regulator	Analog	20mA

Schematics

PCB

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.

For the auto-layout the following class have been used in Eagle:

Signal class	Width	Clearance	Drill
Supply	1.4mm	0.3mm	1mm
GND	1.8mm	0.4mm	1mm
Supply24	1mm	0.3mm	1mm
Signal and others	0.8mm	0.3mm	0.8mm

Datasheets

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

Resistors

• Metal Film Resistor

Capacitors

• SOLID POLYMER ALUMINUM CAPACITOR CHIPS IN DC-DC CONVERTER MODULES REDUCE COST AND SIZE AND IMPROVE HIGH-FREQUENCY PERFORMANCE
• CONDUCTIVE POLYMER ALUMINUM SOLID ELECTROLYTIC CAPACITORS
• Electrolytic Capacitor Guide
• EPCOS Electrolytic Aluminium Capacitor (22000uF/25V)
• EPCOS Electrolytic Aluminium Capacitor (22000uF/16V)

Semiconductors

• L7800 series voltage regulator
• BZX85 Zener Diode
• BD139 NPN Transistor
• BD140 PNP Transistor
• Undervoltage Sensing Circuit

Others

• PCB Layout Guidelines for Power Controllers (Texas Instrument)
• Molex Connectors
• Molex Connectors