Because RFL™ and Hubbell® have a policy of continuous product improvement, we reserve the right to change designs and specifications without notice.
10.2.4 THEORY OF OPERATION (9547-910, -920, -930 AND -950)
The RFL IMUX 2000, 50 Watt power supply is a multiple output, forward, dc to dc converter. The
9547-10 power supply operates from a 19 to 29 Vdc input, the 9547-20 power supply operates from a
38 to 150 Vdc input, the 9547-30 power supply operates from a 180 to 265 Vac input, and the 9547-50
power supply operates from a 120 Vac input. Each of these supplies has four outputs: 5 Vdc at 4.0
Adc, + 15 Vdc at 1.0 Adc, -15 Vdc at -0.75 Adc, and -48 Vdc at 100 mAdc. All of the outputs are
connected to a common ground. The 5 Vdc output is constantly monitored and signals are provided if
the output should exceed lower limits. All outputs contain or’ing diodes for paralleling a second
supply for redundancy.
Input power is fed through terminals A23-25. C23-25 and A30-32, C30-32. An external alarm and
interface board provides fusing and EMI suppression.
Diode CR1 protects the power supply form reversal of input voltage. Under such conditions, a fuse on
the alarm and interface board clears. Inrush limiter TH1 allows charging of capacitor C5 from a stiff
ac or dc source, as applicable, without excessive input currents.
The forward converter is designed around PWM integrated circuit U1. The device has an internal clock
set by resistor R12 and capacitor C11. Power for the device is initially provided by a series regulator
consisting of MOSFET Q3, resistors R2 and R8, and diode CR5. With power applied and internal
clock set, pin 11 of U1 goes high causing MOSFETs Q1, Q2, and Q5 to conduct. This causes the dc
bus voltage to be applied across windings 1 and 2 of transformer E1 and conduction of output diodes
CR7, CR9, CR11, and CR14. Upon conduction of these diodes, power flows from the input to the
output of the power supply. The dc bus current, which flows through MOSFETs Q1 and Q2 is detected
across resistors R5 and R6 and is monitored at pins 3 and 4 of U1. When the peak increases to a level
set at pin 7 of U1, pin 11 of U1 is set low causing transistor Q4 to conduct. This drives MOSFETs Q1
and Q2 to an off state. Transformer E1 voltage reverses and diodes CR8, CR9 (opposite device),
CR10, CR14 (opposite device) conduct and circulate current stored in inductor L3. Inductor L3 and
capacitors C19, C24, C26, and C34 form a low pass filter producing a dc that is the half cycle average
voltage produced by transformer E1. Inductor L3 is a multi-winding inductor that is matched to
transformer E1.
The auxiliary winding of transformer E1, terminals 5 and 6, provides a source of power for the
supply’s control circuit. After the first few cycles, the voltage at capacitor C17 increase rendering
MOSFET Q3 non-conductive.
The secondary auxiliary winding of transformer E1, terminals 3 and 4, capacitor C6, and diode CR2, is
a clamp to limit voltage transients across MOSFETs Q1 and Q2.
IMUX 2000E1 RFL Electronics Inc.
January 1, 2008 10-6 (973) 334-3100
To Next Page
Loading...
