SSC2006SA 데이터 시트보기 (PDF) - Sanken Electric co.,ltd.
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SSC2006SA Datasheet PDF : 23 Pages
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SSC2006SA
The off duty DOFF of boost converter in CRM mode
have the relation of DOFF(t) = VAC(t)/VOUT and is
proportional to input voltage, where VAC(t) is the input
voltage of AC line as a function of time.
As a result of aforementioned control shown in Figure
8-4, the peak current ILPEAK of the inductance current IL
becomes sinusoidal. Since the averaged input current
become similar to AC input voltage waveform by Low
Pass Filter at input stage, high power factor is achieved.
8.2 Startup Operation
Figure 8-5 and Figure 8-7 show the VCC pin
peripheral circuit. Figure 8-5 shows how to use an
external power supply. Figure 8-7 shows how to use an
auxiliary winding.
8.2.1 To Use an External Power Supply
When an external power supply shown in Figure 8-5
is used, the startup operation is as follows.
As shown in Figure 8-6, when VCC pin voltage rises
to the Operation Start Voltage VCC(ON) = 12.0 V, the
control circuit starts operation and the COMP pin
voltage increases. The COMP pin voltage increases to
the Zero Duty COMP Voltage VCOMP(ZD) = 0.65 V,
switching operation starts.
When the VCC pin voltage decreases to
VCC(OFF) = 9.5 V, the control circuit stops operation by
Undervoltage Lockout (UVLO) circuit, and reverts to
the state before startup.
Since the COMP pin voltage rises from zero during
startup period, the VCOMP signal shown in Figure 8-3
gradually rises from low voltage. The on-width
gradually increased to restrict the rise of output power
by the Softstart Function. Thus, the stress of the
peripheral component is reduced.
External
power supply
U1
8
VCC
C7
RS
CS
3
COMP
CP
GND
6
Figure 8-5 VCC pin peripheral circuit
(Power supply from external power supply)
ICC
ICC（ON）
VCC（OFF）
VCC pin
voltage
VCC（ON）
Figure 8-6 Relationship between VCC pin voltage
and ICC
8.2.2 To Use an Auxiliary Winding
When an auxiliary winding is used as shown in Figure
8-7, CVCC is charged through RST at startup. When VCC
pin voltage rises to VCC(ON) = 12.0 V, the control circuit
starts operation.
Figure 8-8 shows the VCC pin voltage behavior
during startup period.
When the VCC pin voltage reaches VCC(ON), the
control circuit starts operation. Then the circuit current
increases and the VCC pin voltage decreases. At the
same time, the auxiliary winding voltage VD increases in
proportion to the output voltage. These are all balanced
to produce VCC pin voltage.
The value of CVCC, the turns ratio of boost winding P
and auxiliary winding D should be set so that VCC pin
voltage is maintained higher than VCC(OFF) = 9.5 V (Refer
to Section 9.1).
If the values of RST and CVCC are large, the startup
time becomes longer. Adjustment is necessary in actual
operation.
When the COMP pin voltage increases to the Zero
Duty COMP Voltage VCOMP(ZD) = 0.65 V after the
control circuit starts operation, switching operation starts
and the circuit current is supplied from auxiliary
winding D as follows.
VB and VD are the voltage of auxiliary winding during
Q1 on and off, respectively.
When Q1 is on, CCP is charged by VB. When Q1 is off,
the capacitor connected to VCC pin, CVCC, is charged by
VD + VB (=VCCP).
VB is calculated using Equation (1).
VB
VIN
ND
NP
(V)
(1)
Where,
VIN: C1 voltage (V)
NP: Number of turns of boost winding P (turns)
ND: Number of turns of auxiliary winding D (turns)
SSC2006SA - DSJ Rev.1.6
SANKEN ELECTRIC CO.,LTD.
9
Aug.11, 2015
http://www.sanken-ele.co.jp/en/
© SANKEN ELECTRIC CO.,LTD. 2013
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