DESCRIPTION FEATURES APPLICATIONS

RS2132
High Precision CC/CV Primary-Side PWM
Controller
DESCRIPTION
FEATURES
RS2132 is a high performance offline PWM controller
for low power AC/DC charger and adapter
applications. It operates in primary‐side sensing and
regulation. Consequently, opto‐coupler and 431 could
be eliminated. Proprietary Constant Voltage (CV) and
Constant Current (CC) control is integrated as shown
in the figure below.
In CC control, the current and output power setting can
be adjusted externally by the sense resistor at CS pin.
In CV control, multi‐mode operations are utilized to
achieve high performance and high efficiency. In
addition, good load regulation is achieved by the built‐
in cable drop compensation. Device operates in PFM
in CC mode as well at large load condition and it
operates in PWM with frequency reduction at
light/medium load.
RS2132 offers power on soft start control and
protection coverage with auto ‐ recovery features
including Cycle‐by‐Cycle current limiting,
VDD OVP, VDD clamp and UVLO. Excellent EMI
performance is achieved with Orister proprietary
frequency jiggling technique. High precision constant
voltage (CV) and constant current (CC) can be
achieved by RS2132.
• ±5% constant voltage regulation at universal AC
input
• High precision constant current regulation at
universal AC input
• Primary‐side sensing and regulation without 431 and
opto-coupler
• Programmable CV and CC regulation
• Adjustable constant current and output power setting
• Built‐in secondary constant current control with
primary side feedback
• Built‐in adaptive current peak regulation
• Built‐in primary winding inductance compensation
• Programmable cable drop compensation
• Power on soft‐start
• Built‐in leading edge blanking (LEB)
• Cycle‐by‐cycle current limiting
• VDD under voltage lockout with hysteresis (UVLO)
• VDD OVP & VDD clamp
• Available in an sot‐26 package
• RoHS compliant and 100% lead (Pb)‐free and green
(halogen free with commercial standard)
APPLICATIONS
•
•
•
•
•
Cell phone charger
Digital cameras charger
Small power adaptor
Auxiliary power for PC, TV etc.
Linear regulator/RCC replacement
Figure 1. Typical CC/CV Curve
Tel: 886-66296288‧Fax: 886-29174598‧ http://www.princeton.com.tw‧2F, No. 233-1, Baociao Rd., Sindian Dist., New Taipei City 23145, Taiwan
RS2132
BLOCK DIAGRAM
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RS2132
APPLICAION CIRCUIT
ORDER INFORMATION
Device
RS2132 Y Z
V1.0
Device Code
Y is package & Pin Assignments designator:
NF : SOT‐26
Z is Lead Free designator:
P: Commercial Standard, Lead (Pb) Free and Phosphorous (P) Free Package
G: Green (Halogen Free with Commercial Standard)
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RS2132
PIN ASSIGNMENTS
SOT‐26
PIN DESCRIPTION
Pin Name
GND
GATE
CS
INV
COMP
VDD
V1.0
Description
Ground.
Totem output to drive the external Power MOSFET.
Current sense input.
The voltage feedback from auxiliary winding. Connected to resistor divider from auxiliary
winding reflecting output voltage. PWM duty cycle is determined by EA output and current
sense signal at pin 4.
Loop Compensation for CV Stability.
Power Supply.
4
Pin No.
1
2
3
4
5
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RS2132
FUNCTION DESCRIPTION
RS2132 is a cost effective PWM power switch optimized for off‐line low power AC/DC applications including battery
chargers and adaptors. It operates in primary side sensing and regulation, thus opto‐coupler and 431 are not required.
Proprietary built‐in CV and CC control can achieve high precision CC/CV control meeting most adaptor and charger
application requirements.
STARTUP CURRENT AND START UP CONTROL
Startup current of RS2132 is designed to be very low so that VDD could be charged up above UVLO threshold and starts
up quickly. A large value startup resistor can therefore be used to minimize the power loss in application.
OPERATING CURRENT
The Operating current of RS2132 is as low as 2.5mA. Good efficiency is achieved with the low operating current together
with Multi‐mode control features.
SOFT START
RS2132 features an internal soft start to minimize the component electrical over‐stress during power on startup. As soon
as VDD reaches UVLO (OFF), the control algorithm will ramp peak current voltage threshold gradually from nearly zero
to normal setting of 0.90V. Every restart is a soft start.
CC/CV OPERATION
RS2132 is designed to produce good CC/CV control characteristic as shown in the Figure 1.
In charger applications, a discharged battery charging starts in the CC portion of the curve until it is nearly full charged
and smoothly switches to operate in CV portion of the curve.
In an AC/DC adapter, the normal operation occurs only on the CV portion of the curve. The CC portion provides output
current limiting. In CV operation, the output voltage is regulated through the primary side control. In CC operation mode,
RS2132 will regulate the output current constant regardless of the output voltage drop.
PRINCIPLE OF OPERATION
To support RS2132 proprietary CC/CV control, system needs to be designed in DCM mode for flyback system (Refer to
Typical Application Diagram).
In the DCM flyback converter, the output voltage can be sensed via the auxiliary winding. During MOSFET turn‐on time,
the load current is supplied from the output filter capacitor CO. The current in the primary winding ramps up. When
MOSFET turns off, the primary current transfers to the secondary at the amplitude of
IS =
NP
× IP
NS
The auxiliary voltage reflects the output voltage as shown in figure 2 and it is given by
VAUX =
V1.0
NAUX
× (V 0 + ΔV )
NS
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RS2132
Where ΔV indicates the drop voltage of the output Diode.
Figure 2. Auxiliary voltage waveform
Via a resistor divider connected between the auxiliary winding and INV (pin 3), the auxiliary voltage is sampled at the end
of the demagnetization and it is hold until the next sampling.
The sampled voltage is compared with VREF (2.0V) and the error is amplified. The error amplifier output COMP reflects
the load condition and controls the PWM switching frequency to regulate the output voltage, thus constant output voltage
can be achieved.
When sampled voltage is below VREF and the error amplifier output COMP reaches its maximum, the switching frequency
is controlled by the sampled voltage thus the output voltage to regulate the output current, thus the constant output
current can be achieved.
ADJUSTABLE CC POINT AND OUTPUT POWER
In RS2132, the CC point and maximum output power can be externally adjusted by external current sense resistor RS at
CS pin as illustrated in Typical Application Diagram. The output power is adjusted through CC point change. The larger
RS, the smaller CC point is, and the smaller output power becomes, and vice versa as shown in Figure 3.
Figure 3. Adjustable output power by changing RS
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RS2132
OPERATION SWITCHING FREQUENCY
The switching frequency of RS2132 is adaptively controlled according to the load conditions and the operation modes.
No external frequency setting components are required. The operation switching frequency at maximum output power is
set to 60KHz internally.
For flyback operating in DCM, The maximum output power is given by
POMAX =
1
× LP × FSW × I P 2
2
Where LP indicate the inductance of primary winding and IP is the peak current of primary winding.
Refer to the equation 3, the change of the primary winding inductance results in the change of the maximum output
power and the constant output current in CC mode. To compensate the change from variations of primary winding
inductance, the switching frequency is locked by an internal loop such that the switching frequency is
FSW =
1
2TDEMAG
Since TDemag is inversely proportional to the inductance, as a result, the product LP and Fsw is constant, thus the maximum
output power and constant current in CC mode will not change as primary winding inductance changes. Up to +/‐10%
variation of the primary winding inductance can be compensated.
FREQUENCY JIGGLING FOR EMI IMPROVEMENT
The Frequency Jiggling (switching frequency modulation) is implemented in RS2132. The oscillation frequency is
modulated so that the tone energy is spread out. The spread spectrum minimizes the conduction band EMI and therefore
eases the system design.
CURRENT SENSING AND LEADING EDGE BLANKING
Cycle‐by‐Cycle current limiting is offered in RS2132 current mode PWM control. The switch current is detected by a
sense resistor into the CS pin. An internal leading edge blanking circuit chops off the sensed voltage spike at initial
internal power MOSFET on state so that the external RC filtering on sense input is no longer needed. The PWM duty
cycle is determined by the current sense input voltage and the EA output voltage.
GATE DRIVE
The external power MOSFET is driven by a dedicated gate driver of RS2132. Too weak the gate drive strength results in
higher conduction and switch loss of MOSFET while too strong gate drive compromises EMI.
A good tradeoff is achieved through the built‐in totem pole gate design with right output strength control.
PROGRAMMABLE CABLE DROP COMPENSATION
In RS2132, cable drop compensation is implemented to achieve good load regulation. An offset voltage is generated at
INV by an internal current flowing into the resister divider. The current is inversely proportional to the voltage across pin
COMP, as a result, it is inversely proportional to the output load current, thus the drop due to the cable loss can be
compensated. As the load current decreases from full‐load to no‐load, the offset voltage at INV will increase. It can also
be programmed by adjusting the resistance of the divider to compensate the drop for various cable lines used.
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RS2132
PROTECTION CONTROL
Good power supply system reliability is achieved with its rich protection features including Cycle‐by‐Cycle current
limiting (OCP), VDD clamp, Power on Soft Start, and Under Voltage Lockout on VDD(UVLO).
VDD is supplied by transformer auxiliary winding output. The output of RS2132 is shut down when VDD drops below
UVLO (ON) limit and Switcher enters power on start‐up sequence thereafter.
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RS2132
ABSOLUTE MAXIMUM RATINGS
Parameter
Symbol
‐
‐
‐
‐
‐
TJ
TOPR
TSTG
TLEAD
VDD Voltage
VDD Zener Clamp Continuous Current
COMP Voltage
CS Input Voltage
INV Input Voltage
Junction Temperature
Operating Temperature Range
Storage Temperature Range
Lead Temperature (soldering, 10secs)
Range
‐0.3 to VDD_Clamp
10
‐0.3 to 7
‐0.3 to 7
‐0.3 to 7
‐20 to 150
‐20 to +85
‐40 to +150
260
Unit
V
mA
V
V
V
o
C
o
C
o
C
o
C
Note: Stress beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. Exposure to
absolute maximum‐rated conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(VDD=16V, TA=25 oC, unless otherwise specified)
Parameter
Symbol
Supply Voltage (VDD) Section
Standby Current
IDD ST
Operation Current
VDD Under Voltage Lockout Enter
VDD Under Voltage Lockout Exit
Over Voltage Protection Voltage
Maximum VDD Operation Voltage
Current Sense Input Section
LEB Time
Over Current Threshold
OCP Propagation Delay
Input Impedance
Soft Start Time
CV Section
System Nominal Switch Frequency
Frequency Jitter Range
Error Amplifier Section
Reference Voltage For EA
DC Gain Of The EA
Max. Cable Compensation Current
Gate Drive Output Section
Output Low Level
Output High Level
Output Clamp Voltage Level
Output Rising Time
Output Falling Time
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IDD_OP
UVLO(ON)
UVLO(OFF)
OVP
VDD
Clamp
Test Condition
Min.
Typ.
Max.
Unit
VDD=13V
Operation supply current
INV=2V,CS=0V, VDD=20V
VDD falling
VDD rising
Ramp up VDD until gate clock is
off
IDD=10mA
-
5
20
μA
‐
2.5
3.5
mA
13.5
7.5
14.5
8.5
16.0
10
V
V
27.5
29.5
31.5
V
30.5
32.5
34.5
V
‐
870
‐
‐
‐
540
900
150
50
10
930
-
ns
mV
ns
KΩ
ms
‐
‐
60
14
±4
-
KHZ
KHZ
%
INV=2V, COMP=0V
1.97
‐
-
2
60
42
2.03
-
V
dB
μA
IO=20mA
IO=20mA
‐
CL=0.5nF
CL=0.5nF
‐
8
‐
‐
‐
1
‐
‐
‐
‐
V
V
V
ns
ns
TLEB
Vth_oc
Td_oc
ZSENSE IN
Tss
Freq_Nom
Freq_startup
Δf/Freq
VREF_EA
GDC
I_COMP MAX
VOL
VOH
V_clamp
T_r
T_f
INV=0V, COMP=5V
9
‐
‐
16
650
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March 2013
RS2132
PACKAGE INFORMATION
6-PIN, SOT
Notes:
1. Refer to JEDEC MO-178 variation AB
2. All dimensions are in millimeter.
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RS2132
IMPORTANT NOTICE
Princeton Technology Corporation (PTC) reserves the right to make corrections, modifications, enhancements,
improvements, and other changes to its products and to discontinue any product without notice at any time.
PTC cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a PTC product. No
circuit patent licenses are implied.
Princeton Technology Corp.
2F, 233-1, Baociao Road,
Sindian Dist., New Taipei City 23145, Taiwan
Tel: 886-2-66296288
Fax: 886-2-29174598
http://www.princeton.com.tw
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