RS2051 Orister Corporation, RS2051 Datasheet - Page 6

• Manufacturer Part Number: RS2051
• Description: Green?mode
• Manufacturer: Orister Corporation

Internal Synchronized Slope Compensation
Although there are more advantages of the current mode control than conventional voltage mode control, there are still
several drawbacks of peak‐sensing current‐mode converter, especially the open loop instability when it operates in higher
than 50% of the duty‐cycle. To solve this problem, the RS2051 is introduced an internal slope compensation adding voltage
ramp to the current sense input voltage for PWM generation. It improves the close loop stability greatly at CCM, prevents the
sub‐harmonic oscillation and thus reduces the output ripple voltage.
Current Sensing & Dynamic peak limiting
The current flowing by the power MOSFET comes into being a voltage V
to the internal reference voltage, and controls the reverse of the internal register, limits the peak current IMAX of the
primary of the transformer. The transformer energy is
power of the power supple. The current flowing by the power MOSFET has an extra value (
delay time that is from detecting the current through the Sense pin to power MOSFET off in the RS2051 (Among these, V
the primary winding voltage of the transformer and L
guarantee the output power is a constant for universal input AC voltage, there is a dynamic peak limit circuit to compensate
the system delay T that the system delay brings on.
Frequency Jiggling for EMI improvement
The Frequency Jiggling Technique is introduced in the RS2051. As following figure, the internal oscillation frequency is
modulated by itself. A whole surge cycle includes 128 pulses and the Jiggling ranges from ‐4% to +4%. Thus, the function
could minimize the electromagnetic interferer from the power supply module.
DS‐RS2051‐09 November, 2009
1.10
1.05
1.00
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0%
70K
65K
60K
Vsense
Frequency(HZ)
V
Frequency Jiggling to reduce EMI
SLOP
10%20%30%40%50%60%70%80%90%
=
. 0
Slope Compensation
33
P
is the primary wind inductance). V
×
DUTY
E
DUTY
=
1
2
MAX
L ×
=
I ×
. 0
MAX
4389
2
SENSE
So adjusting the R
×
Duty Cycle
DUTY
on the Sense pin cycle‐by‐cycle, which compares
Time
IN
ranges from 85VAC to 264VAC. To
SENSE
Δ
= I
can set the maximal output
V
L
IN
P
×
T
D
) due to the system
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IN
is