The PN8359ac-dc isolated primary-side feedback switching power supply chip integrates a 650V power MOSFET and primary-side inductance compensation circuit, eliminating the need for optocouplers and TL431. It features excellent and comprehensive protection functions and is used by Liwei Electronics in high-performance switching power adapters, battery chargers, set-top box power supplies, and LED lighting with simplified external components.
Let's take a closer look at the functional description of the PN8359 switching power converter chip with the help of Chipown's distributor, Liwei Electronics:
1. Startup: During startup, the internal high-voltage current source powers the internal bias circuit and charges the external VDD capacitor. When the VDD voltage reaches 15V, the chip starts working while the high-voltage startup circuit is turned off; as long as the VDD voltage is not lower than 8V, the chip maintains normal operation. After startup, the bias circuit is powered by an auxiliary source.
2. CC Operating Mode: In CC operating mode, the PN8359 switching power converter chip samples the signal from the FB pin (which is a voltage divider formed by the auxiliary winding signal through a resistor). The pulse width of the auxiliary winding signal determines the oscillation frequency. The higher the output voltage, the smaller the pulse width, and the higher the oscillation frequency, thus obtaining a constant output current.
3. CV Operating Mode: In CV operating mode, the PN8359 switching power converter chip samples the signal from the FB pin (derived from the auxiliary winding signal through a resistor voltage divider), and the auxiliary winding voltage determines the oscillation frequency. In heavy load mode, the output current decreases, and the oscillation frequency decreases; under no-load conditions, the chip enters a skip-cycle mode to further reduce standby power consumption. Under light load conditions, the chip operates with a smaller peak current to reduce audio noise.
4. Current Sensing and Leading-Line Blanking: The PN8359 switching power converter chip provides cycle-by-cycle sensing. The power transistor current is sensed through a resistor on the CS pin. The CC mode setpoint and maximum output power are both achieved by externally adjusting the resistor on the CS pin. A voltage spike is generated when the power transistor turns on; the internal leading-line blanking circuit prevents false triggering without requiring an additional RC filter circuit.
5. Programmable Cable Compensation Function: The cable compensation module can compensate for output line loss voltage drop. When the load decreases from full load to no load, the line loss voltage drop also decreases. Under no load, the CV setpoint is decreased, while under full load, the CV setpoint is increased. This compensation is determined by the chip's internal settings, and the required compensation range can be selected by using different chip versions.
6. Protection and Control: The PN8359 switching power supply converter chip has several self-protection functions, such as overvoltage protection, overtemperature protection, open-loop protection, output short-circuit protection, CS resistor open/short-circuit protection, and VDD undervoltage lockout protection. Except for CS short-circuit protection, the other protections are self-recoverable.
The PN8359 switching power converter chip features a built-in high-voltage startup circuit and extremely low chip power consumption, enabling it to meet high standby power consumption standards. In constant current mode, the current and output power can be adjusted via the Rs resistor on the CS pin; in constant voltage mode, the PFM operating mode achieves high performance and efficiency. Under light load, this chip, distributed by Liwei Electronics, operates with a smaller peak current to reduce audio noise. Additionally, output line compensation helps achieve good load regulation.
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