NCP1239: Fixed Frequency Current Mode Controller for Flyback Converter with HV startup
Description: The NCP1239 is a fixed-frequency current-mode cont...
The NCP1239 is a fixed-frequency current-mode controller featuring the Dynamic Self-Supply. This function greatly simplifies the design of the auxiliary supply and the Vcc capacitor by activating the internal startup current source to supply the controller during start-up, transients, latch, stand-by etc.
With a supply range up to 35 V, the controller hosts a jittered 65 or 100-kHz switching circuitry operated in peak current mode control. When the power on the secondary side starts to decrease, the controller automatically folds back its switching frequency down to minimum level of 26 kHz. As the power further goes down, the part enters skip cycle while limiting the peak current that insures excellent efficiency in light load condition.
It features a timer-based fault detection that ensures the detection of overload and an adjustable compensation to help keep the maximum power independent of the input voltage.
Fixed-frequency 65-kHz or 100-kHz current-mode control operation - Fixed-frequency is simple to implement and predictable in term of EMI
Frequency foldback down to 26 kHz and skip mode - Maximize performance in light load conditions
Adjustable Over Power Protection (OPP) circuit - OPP can be adjusted to the need of specific applications
High-voltage Current Source with Brown-out (BO) detection - BO monitor and detect a falling input voltage, needed in some applications
Internal fixed 8-ms soft-start - Simplified implementation that does not require programming
Frequency jittering in normal and frequency foldback modes - Lowers switching frequency EMI
64-ms timer-based short-circuit protection with auto-recovery or latched operation - Allows for safe operation while tolerant to faults if needed
Pre-short ready - Safe operation yet tolerant to faults
Latched OVP on Vcc (NCP1239 A & B versions) - Safe operation
Latched OVP/OTP input for improved robustness - Safe operation
+500 mA/ -500 mA peak source/sink drive capability - Can drive larger FETs
Internal thermal shutdown - Safe operation
Extremely low no-load standby power - Ideal for environmentally friendly applications
Pin-to-pin compatible with the existing NCP1236/1247 series - Enable cost saving compared to other device
Internal ramp compensation
35-V Vcc operation
Ac-dc converters for TVs, set-top boxes and printers
Offline adapters for notebooks and netbooks
Technical Documentation & Design Resources
Evaluation/Development Tool Information
Product Change Notification
fsw Typ (kHz):
Short Circuit Protection:
VCC Max (V):
Drive Cap. (mA):
500 / 500