ICE5QSAG 查看數據表（PDF） - Infineon Technologies
零件编号
产品描述 (功能)
生产厂家
ICE5QSAG Datasheet PDF : 27 Pages
| |||
Quasi-Resonant Controller
Functional Description
3
Functional Description
3.1
VCC Pre-Charging and Typical VCC Voltage during Start-up
As shown in Figure 1, once the line input voltage is applied, a rectified voltage appears across the capacitor
CBUS. The pull up resistor RSTARTUP provides a current to charge the Ciss (input capacitance) of CoolMOS™ and
gradually generate one voltage level. If the voltage over Ciss is high enough, CoolMOS™ on and VCC capacitor will
be charged through primary inductance of transformer LP, CoolMOS™ and internal diode D3 with two steps
constant
current
source
IVCC_
1
Charge1
and
IVCC_
.1
Charge3
A very small constant current source (IVCC_Charge1) is charged to the VCC capacitor till VCC reach VCC_SCP to protect
the controller from VCC pin short to ground during the start up. After this, the second step constant current
source (IVCC_Charge3) is provided to charge the VCC capacitor further, until the VCC voltage exceeds the turned-on
threshold VVCC_ON. As shown in the time phase I in Figure 4, the VCC voltage increase almost linearly with two
steps.
VVCC
I
II III
(VVCC_ON )16V
(VVCC_OFF) 10V
tA
tB
(VVCC_SCP) 1.1V
t
IVCC
(IVCC_Normal) 0.9mA
0
(IVCC_Charge1) -0.2mA
t
t1 t2
IVCC_Charge2/3) -3/-3.2mA
-IVCC
Figure 4
VCC voltage and current at start up
The time taking for the VCC pre-charging can then be approximately calculated as:
��1
=
��A
+
��B
=
��������_������ ∙ ��������
��������_��ℎ��������1
+
(��������_���� − ��������_������)
��������_��ℎ��������3
∙
��������
(1)
When the VCC voltage exceeds the VCC turned on threshold VVCC_ON at time t1, the IC begins to operate with soft
start. Due to power consumption of the IC and the fact that there is still no energy from the auxiliary winding to
charge the VCC capacitor before the output voltage is built up, the VCC voltage drops (Phase II). Once the output
voltage is high enough, the VCC capacitor receives the energy from the auxiliary winding from the time t2 onward
and
delivering
the
IVCC_
2
Normal
to
the
controller.
The
VCC
then
will
reach
a
constant
value
depending
on
output
load.
3.2
Soft-start
As shown in Figure 5, at the time ton, the IC begins to operate with a soft-start. By this soft-start the switching
stresses for the MOSFET, diode and transformer are minimized. The soft-start implemented in ICE5QSAG is a
digital time-based function. The preset soft-start time is tSS (12 ms) with 4 steps. If not limited by other
functions, the peak voltage on CS pin will increase step by step from 0.3 V to 1 V finally. During the first 3 ms of
1 IVCC_ Charge1/2/3 is charging current from the controller to VCC capacitor during start up
2 IVCC_ Normal is supply current from VCC capacitor or auxiliary winding to the controller during normal operation
Datasheet
6 of 27
V 2.1
2020-02-03
Share Link: 