启达启臣微CR5212 High Precision CC/CV PSR PWM Switch
CR5212FEATURES
Low startup current
±4% CC and ±5% CV Precision
Primary-side Sensing and Regulation
Without TL431 and Opto-coupler
High precision constant voltage and
current regulation at universal AC input
Programmable CV and CC Regulation
Built-in Primary winding inductance
compensation
Programmable Cable Drop
CR5212Compensation
Built-in Feedback Loop Open Protection
Built-in CS Open Protection
VDD Over Voltage Protection
Built-in Output Short Circuit Protection
Built-in Leading Edge Blanking (LEB)
Over temperature protection(OTP)
Cycle-by-Cycle Current Limiting
VDD Under Voltage Lockout with
Hysteresis (UVLO)
SOP-7L green Packaging
CR5212Applications
Switching AC/DC Small Power Adaptor
Cell Phone or Digital Cameras Charger
Auxiliary Power for PC, TV etc
Linear Regulator/RCC Replacement
CR5212General Description
CR5212 is a high performance offline PSR controller for low power AC/DC charger and
adapter applications. It operates in primary-side sensing and regulation, so opto-coupler and
TL431 could be eliminated. In CC control, the current and output power setting can be adjusted
externally by the sense resistor R S at CS pin. In CV control, PFM operations are utilized to
achieve high performance and high efficiency. In addition, good load regulation is achieved by the
built-in cable drop compensation.
The chip consumes very low operation current (typical 650μA), it can achieve less than 30mW
standby power to meet strict standby power standard. CR5212 offers comprehensive protection
coverage with auto-recovery features including Cycle-by-Cycle current limiting, VDD over
voltage protection, feedback loop open protection, CS open protection, Output short circuit
protection, built-in leading edge blanking, VDD under voltage lockout (UVLO), Over temperature
protection , etc. CR5212 is offered in SOP-7L package.
CR5212OPERATION DESCRIPTION
CR5212 is a high performance offline PSR controller for low power AC/DC charger and
adapter applications. It operates in primary-side sensing and regulation, So opto-coupler and
TL431 could be eliminated. In CC control, the current and output power setting can be adjusted
externally by the sense resistor R S at CS pin. In CV control, PFM operations are utilized to
achieve high performance and high efficiency. In addition, good load regulation is achieved by the
built-in cable drop compensation.
Startup and Under Voltage Lockout
Startup current of CR5212 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.
.
CR5212CC/CV Operation
CR5212 is designed to produce good CC/CV control. 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. The CC portion provides output current limiting.
In CV operation, the output voltage is regulated through the primary side control. In CC operation
mode, CR5212 will regulate the output current constant regardless of the output voltage drop.
CR5212Principle of Operation
To support CR5212 CC/CV control, system needs to be designed in DCM mode for flyback
system. In the DCM flyback converter, the output voltage can be sensed via the auxiliary winding.
During NPN turn-on time, the load current is supplied from the output filter capacitor. The
current in the primary winding ramps up. When NPN turns off, the energy stored in the primary
winding is transferred to the secondary side. The current in the secondary winding is
