启达启臣微CR3346 High Precision CC/CV PSR And QR Switch
CR3346FEATURES
Standby power less than 75mW
Bulit-in 650V Power MOSFET
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
Quasi_Resonant （QR） operation for
efficiency improving
Programmable Cable Drop
CR3346Compensation
Built-in line voltage and primary winding
inductance compensation
Multi-mode control
Built-in CS Open Protection
VDD Over Voltage Protection and
CR3346Clamp Protection
Built-in Short Circuit Protection
Built-in Leading Edge Blanking (LEB)
Over temperature protection(OTP)
Cycle-by-Cycle Current Limiting
VDD Under Voltage Lockout with
CR3346Hysteresis (UVLO)
SOP-7L Packaging
CR3346APPLICATIONS
Switching AC/DC Small Power Adaptor
Auxiliary Power for PC, TV etc
Linear Regulator/RCC Replacement
AC/DC LED lighting
CR3346GENERAL DESCRIPTION
CR3346 is a high performance offline PSR switch for low power AC/DC charger and adapter
applications,It operates in Quasi_Resonant （QR） mode; Less than 75mW standby power
consumption with typical application. 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.
CR3346 offers comprehensive protection coverage with auto-recovery features including
Cycle-by-Cycle current limiting, VDD over voltage protection and clamp protection, CS open
protection, short circuit protection, built-in leading edge blanking, VDD under voltage lockout
(UVLO),Over temperature protection(OTP),OUT over voltage protection(FB_OVP).
CR3346OPERATION DESCRIPTION
CR3346 is a cost effective PSR power switch optimized for off-line low power AC/DC
applications. It operates in primary side sensing and regulation, thus opto-coupler and TL431 are
not required. Proprietary operates in Quasi_Resonant(QR) mode,built-in CC/CV control can
achieve high precision CC/CV control to meet most charger application requirements.
Startup Current and Startup Control
Startup current of CR3346 is designed very low (typical 2uA) so that VDD could be charged
up above UVLO_OFF threshold level and device start up quickly.A large value startup resistor can
therefore be used to minimize the power loss yet reliable startup in application.
CR3346QR Control
CR3346 operates in Quasi_Resonant(QR) mode in CC/CV mode, it can achieve high
efficiency and low EMI .
CR3346Principle of Operation
To support CR3346 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 MOSFET turn-on time, the load current is supplied from the output filter capacitor. The
current in the primary winding ramps up. When MOSFET turns off, the energy stored in the
primary winding is transferred to the secondary side. The current in the secondary winding is
