UM2076
SCR
switch insulated control
DocID029457 Rev 1
33/43
𝑅
𝐹2
+ 𝑅
𝐹3
=
𝑉𝐶𝐶
𝐴𝐶
− 𝑉𝐶𝐸_𝑆𝐴𝑇
𝑂𝑃𝑇𝑂
− 𝑉𝐵𝐸_𝑆𝐴𝑇
𝑃𝑁𝑃
𝑉𝐶𝐶
𝐴𝐶
− 𝑉𝐶𝐸_𝑆𝐴𝑇
𝑁𝑃𝑁
− 𝑉
𝐺𝐾
𝛽 × 𝑅𝑔
+
𝑉𝐵𝐸_𝑆𝐴𝑇
𝑃𝑁𝑃
𝑅
𝐹1
Given optocoupler CTR and resistors R
F1
and R
F2
, the LED resistor (R
L
) of the optocoupler
is defined by Equation 6, where VCC_AC is the power supply to provide the gate current to
the AC switch, VCE_SAT
Opto
is the transistor collector-emitter of the optocoupler,
VBE_SAT
PNP
is the PNP transistor base-emitter and VOH_Min_MCU is the output MCU
voltage to drive the optocoupler.
Equation 6
𝑅
𝐿
=
𝑉𝑂𝐻_𝑀𝑖𝑛_𝑀𝐶𝑈 − 𝑉𝐹
𝑂𝑃𝑇𝑂
1
𝐶𝑇𝑅 ×
𝑉𝐶𝐶_𝐴𝐶 − 𝑉𝐶𝐸_𝑆𝐴𝑇
𝑂𝑃𝑇𝑂
− 𝑉𝐵𝐸_𝑆𝐴𝑇
𝑃𝑁𝑃
𝑅
𝐹2
+ 𝑅
𝐹3
With the LTV-817 optocoupler and the 2N2907 PNP transistor, the resistors should be:
R
F1
= 1 kΩ
R
F2
= 390 Ω
R
L
= 270 kΩ
C
F2
= 10 nF
C
F1
= 10 nF
The actual values in the ICL board schematic are:
R
F1
= R
13
= R
19
= 1 kΩ
R
F2
= R
F3
= R
15
= R
16
= R
21
= R
22
= 390 Ω
R
L
= R
14
= R
20
= 270 kΩ
C
F2
= C
11
= C
13
= 10 nF
C
F1
= C
10
= C
12
= 10 nF
Содержание STEVAL-ISF003V1
Страница 3: ...UM2076 Contents DocID029457 Rev 1 3 43 13 Conclusion 41 14 Revision history 42 ...
Страница 18: ...Schematic diagrams UM2076 18 43 DocID029457 Rev 1 Figure 12 STEVAL ISF003V1 control circuit schematic ...
Страница 19: ...UM2076 Schematic diagrams DocID029457 Rev 1 19 43 Figure 13 STEVAL ISF003V1 flyback SMPS schematic ...
