UM2027
Getting
started
DocID029048 Rev 1
11/37
the HVDC bus during charging and sinks a current which is too high, preventing
the DC capacitor from being charged efficiently.
Orange constant indicates the output DC capacitor is not charged to the peak line
voltage. This may occur when the bridge is started, but a power load is already
connected to the HVDC bus and sinks a current which is too high, preventing the
DC capacitor from being fully charged.
Red constant indicates the board is connected to a 198-264 V line while the
doubler jumper is connected.
Red flashing indicates the MCU detected an error (e:g., the line voltage is outside
the two correct operating ranges: 90-132 V and 198-264 V; the line frequency is
not detected as stable for 50 or 60 Hz).
"HVDC" (LED2): this LED lights red when a voltage higher than 50 V is present
between HVDC and GND_DC terminals (refer to
Section 2.3: "DC bus capacitor
discharge for demonstration purpose"
for further information).
"OUT1" to "OUT5" (LED6 to LED10) are ON when the corresponding AC switch (T1 to
T5) is turned on.
2.5
Possible board adaptations
The STEVAL-IHT008V1 board allows certain external components to be added to the front-
end circuit, so designers can validate an entire system. The main possible modifications
are listed below.
2.5.1
ACST use and MOV removal
The T1635T-8FP Triac used for T_ICL can be replaced by an ACST1635-8FP. Both
devices are indeed pin-to-pin compatible. The MOV used to protect the T1635T-8FP
(SIOV1) can be removed as the ACST1635T is an overvoltage protected device.
if the ACST1635-8FP is triggered in breakover mode, the applied current and its
rate of increase (di/dt) must remain below the values specified in the datasheet:
290 A peak current (8/20 µs waveform) and 150 A/µs, respectively.
For a high output DC capacitor value, the current may exceed this datasheet limit.
On our board, the input varistor (SIOV2) clamps the voltage applied to the ACST1635-8FP
below the typical clamping voltage of the device (VCL) for surges up to 2 kV. This prevents
ACST1635-8FP turn-on in breakover.
2.5.2
EMI filter and DC bus capacitors change
The EMI filter and DC capacitors only use through-hole devices to facilitate unsoldering
them to replacing them with ones used in the target application. This allows a designer to
adapt the EMI filter and HVDC voltage ripple to specific application requirements (such as
the power rating).
Obviously, as soon as these component values are modified, the control law of the T_ICL
Triac has to be updated to ensure ongoing compliance with the IEC 61000-3-3 limits. For
this purpose, the maximum peak current during startup can be adjusted with the "MAX-
INRUSH CURRENT" potentiometer. When this potentiometer is turned clockwise, the Triac
is turned sooner at each half-cycle, leading to a higher peak current.
The maximum RMS current or voltage fluctuation (when a normalized line impedance is
used) must then be measured according to the potentiometer position to check compliance
with IEC 61000-3-3.
