Introduction
WRB1209S-3W-7892-8740K1 is isolated 3W DC-DC converter module with a wide 2:1 input voltage range (9-18V), and a regulated output of 9V. The product has a relatively compact open-frame SIP-7 package. The power module features high efficiency, operating ambient temperature of -40℃ to +85℃, remote control, and continuous short-circuit protection. The smaller size and cost-effective design make the module an ideal solution in communication, instruments, and industrial electronics applications.
Functional Block Diagram
WRB1209S-3W-7892-8740K1 module employs an isolated flyback architecture with primary-side regulation. The system primarily comprises a flyback controller IC, a transformer, input and output capacitors, and associated peripheral components.

During the off-time (Toff ), the voltage across the primary winding is VIN+N·VO . Consequently, the voltage across resistor RFB equals N·VO , generating a current of N·VO/RFB . This current flows through resistor RREF , producing a voltage drop of (N·VO/RFB)·RREF . This voltage is compared against the error amplifier’s internal 1V reference to generate an error signal. The signal is subsequently amplified and processed by the control circuit to drive the power MOSFET.
Features
- Ultra compact SIP package
- Cost-effective open-frame solution
- No-opto solution for higher reliability
- Wide 2:1 input voltage range
- Isolation test voltage: 1.5kVDC
- Short circuit protection (Auto-recovery)
- Remote ON/OFF

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