RS2030 Orister Corporation, RS2030 Datasheet - Page 4

• Manufacturer Part Number: RS2030
• Description: Lowest Cost Greenpower Offline Pwm Controller
• Manufacturer: Orister Corporation

Page No. : 4/8
Detail Description
Current Model
Compared to voltage model control, current model control has a current feedback loop. When the voltage of the sample resistor peak
current of the primary winding reaches the internal setting value V
, comparator reverse, register reset and power BJT or MOSFET cut‐off.
TH
So that to detect and modulate the peak current cycle by cycle could control the output of the power supply. The current feedback has a
good linear modulation rate and a fast input and output dynamic impact avoid the pole that the output filter inductance brings and the
second class system descends to first class and so it widens the frequency range and optimizes overload protection and short circuit
protection.
Startup Current and Under Voltage Lockout
The startup current of RS2030 is set to be very low (3μA) so that a large value startup resistor can therefore be used to minimize the power
loss. For AC to DC adaptor with universal input range design, a 1.5 MΩ, 1/8 W startup resistor and a 10μF/25V V
hold capacitor could be
DD
used.
The turn‐on and turn‐off threshold of the RS2030 is designed to 5.4V/3.6V. During startup, the hold‐up capacitor must be charge to 5.4V
through the startup resistor. The hysteresis is implemented to prevent the shutdown from the voltage dip during startup.
Green Power Operation
The power dissipation of switching mode power supply is very important in zero load or light load condition. The major dissipation result
from conduction loss、switching loss and consume of the control circuit. However, all of them related to the switching frequency. There
are many difference topologies has been implemented in different chip. The basic operation theory of all these approaches intended to
reduce the switching frequency under light‐load or no‐load condition.
RS2030’s green power function adapts PWM、PFM and CRM combining modulation. The PWM frequency is 65KHz/100KHz in medium or
heavy load operation. Through modifying the pulse width, RS2030 could control output voltage. To decrease the standby consumption of
the power supply , Orister introduces the Cycle Reset Mode technology；If the feedback current were over 1.5mA, mode controller of
RS2030 would reset internal register all the time and cut off the power BJT, while the output voltage is lower than the set value, it would
set register, SW pin operating again. Although the frequency of the internal OSC is invariable, the register would reset some pulses so that
the practical frequency is decreased at the SW pin.
RS2030 Green‐Power Function
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. RS2030
is introduced an internal slope compensation adding voltage ramp to the current sense input voltage for PWM generation to solve this
problem. It improves the close loop stability greatly at CCM, prevents the sub‐harmonic oscillation and thus reduces the output ripple
voltage.
High/Low Voltage Power Compensation
DS‐RS2030‐13 September, 2009
www.Orister.com