Getting
started
UM2076
14/43
DocID029457 Rev 1
charged). This flashing mode can last less than one second and may therefore
not be perceived.
Green: DC bus is charged to the right voltage.
Orange flashing: the DC bus capacitors are charging, but the rate of increase of
the output DC voltage is too low. This may occur when a load connected to the
HVDC bus sinks too much current for the DC capacitor to charge efficiently.
Orange: the LED stops flashing and remains lit orange if the output DC capacitor
is not charged to the peak line voltage. This may occur if the bridge is started but
a power load is already connected to the HVDC bus and sinks too much current
for the DC capacitor to fully charge.
Red flashing: the MCU detected an error (e.g., line voltage outside 85 to 264 V
operating range or line frequency outside 45 to 65 Hz operating range).
HVDC (LED6): lights red when the voltage between HVDC and GND_DC terminals is
higher than 50 V (see
Section 4.3: "DC bus capacitor discharge for demonstration
POWER_ON (LED14): lights when the AC line is plugged to the AC line.
2.5
Possible board variations
The STEVAL-ISF003V1 board allows some external components to be added to the front-
end circuit so designers can evaluate entire systems.
2.5.1
EMI filter and DC bus capacitor alteration
The EMI filter and DC capacitors are simple through-hole devices so they are easy to
change. This allows a designer to adapt the EMI filter and HVDC voltage ripple to specific
application requirements (e.g., the power rating).
However, if these components are modified, the SCR control law must be updated to
maintain IEC 61000-3-3 compliance. This can be done by adjusting the maximum peak
current during start-up with the MAX-INRUSH CURRENT potentiometer. When this
potentiometer is turned clockwise, the SCRs are turned on sooner (according to the AC line
polarity) at each half-cycle, leading to a higher peak current.
Maximum RMS current or voltage fluctuation (if a normalized line impedance is used) must
then be measured according to the potentiometer position to check IEC 61000-3-3
compliance.
If the EMI filter capacitor (C4 to C9) values are increased, R10 and R12 values
may be decreased to ensure that the capacitors still discharge down to a safe
voltage (120 V for DC voltage) in less than one or two seconds. Indeed, the EMI
filter capacitor voltage is applied to the power plug when the board is unplugged
and, if the power terminals have accessible live parts, you may be vulnerable to
electric shock.
2.5.2
Power factor circuit connection
A PFC can be connected on the HVDC bus via the HVDC (J2) and GND_DC connections
(J8). Capacitor C3 must be unsoldered by using a 630 V DC film capacitor if needed.
As SCRs are alternately controlled by a DC gate current (according to AC line polarity),
when the HVDC voltage reaches its steady-state value, either a discontinuous mode or a
continuous mode PFC can be used.
For proper STEVAL-ISF003V1 front-end circuit operation, the PFC must be activated after
the PFC_START signal is set to a low level (see
Figure 10: "PFC activation permission
(PFC_Start signal) when the HV output capacitor is charged"
, indicating that the PFC HV
