SF Series

Electrical Characteristics & Description
SF Series units are extremely versatile, allowing the user to float the high voltage up to 5 kVDC above the input line. These power supplies are ideal for photomultiplier, CRT, and other electro-optical applications. The output voltage adjustment is via a 10 turn slotted screwdriver potentiometer located on the top surface of the unit. Each unit is encapsulated in an anodized aluminum case which provides electrostatic shielding and heat removal.  The calculated MTBF is 70,000 hours at 85 deg C case temperature. Units may be stacked on top of each other with this arrangement.

The SF Series high voltage power supplies are regulated by virtue of Pulse Width Modulation topology. The normal input voltage of 28 VDC is stepped up by resonant action to a high voltage output which is floating with respect to the input ground. The output voltage is sensed using a unique patented circuit to allow fully floating operation with no Galvanic connection to the input power side of the power supply.

The output voltage may be controlled in two different ways. In voltage programming mode, a control voltage between 1 VDC and 7 VDC will adjust the output between 20% and full output. In the resistance programming mode, a resistor placed between Pin 2 (7.0-V reference output) and Pin 3 (Vcontrol) will set the output to a voltage which depends on the value of the resistance used. Typically a 5  kOhm resistor will set the output voltage to 50%. Zero resistance yields full output. The maximum output current ability is set for each unit to be 120% above the nominal value determined by the maximum output power for the supply. The current limit circuitry internal to the SF high voltage power supply has a reaction time constant of less than 0.01 second.