TI中文支持网Part Number:UCC28740
UCC28740使用过程中,出现偶尔不起机现象,咨询相关锁死保护逻辑,如果触发过压过流保护,释放后能自行恢复还是需要重新上电才能恢复?
Daniel：
您好
https://www.ti.com/lit/ds/symlink/ucc28740.pdf
根据datasheet中有不同的报错不同的保护机制，在datasheet中7.3.4 Fault Protection有详细说明请您参考。
The UCC28740 provides extensive fault protection. The protection functions include: • Output overvoltage • Input undervoltage • Internal overtemperature • Primary overcurrent fault • CS-pin fault • VS-pin fault A UVLO reset and restart sequence applies to all fault-protection events.
The output-overvoltage function is determined by the voltage feedback on the VS pin. If the voltage sample of VS exceeds 4.6 V, the device stops switching and the internal current consumption becomes IFAULT which discharges the VDD capacitor to the UVLO-turnoff threshold. After that, the device returns to the start state and a startup sequence ensues. The UCC28740 always operates with cycle-by-cycle primary peak current control. The normal operating voltage range of the CS pin is 0.773 V to 0.194 V. An additional protection, not filtered by leading-edge blanking, occurs if the CS pin voltage reaches 1.5 V, which results in a UVLO reset and restart sequence. Current into the VS pin during the MOSFET on-time determines the line-input run and stop thresholds. While the VS pin clamps close to GND during the MOSFET on-time, the current through RS1 is monitored to determine a sample of VBULK. A wide separation of the run and stop thresholds allows for clean startup and shutdown of the power supply with the line voltage. The run-current threshold is 225 µA and the stop-current threshold is 80 µA. The internal overtemperature-protection threshold is 165°C. If the junction temperature reaches this threshold the device initiates a UVLO-reset cycle. If the temperature is still high at the end of the UVLO cycle, the protection cycle repeats. Protection is included in the event of component failures on the VS pin. If complete loss of feedback information on the VS pin occurs, the controller stops switching and restarts.
这是datasheet的详细说明。
UCC28740的过压和过流保护逻辑：
过压保护（Output Overvoltage Protection）：
当VS引脚上的电压样本超过4.6V时，设备会停止切换并进入故障模式。
内部电流消耗变为IFAULT，这会导致VDD电容放电到UVLO（欠压锁定）关闭阈值。
一旦VDD电容放电到UVLO关闭阈值以下，设备将返回到起始状态并启动启动序列。结论：对于过压保护，设备在故障后会自动通过UVLO重置和重启序列恢复到正常操作状态，无需重新上电。
过流保护（Internal Overcurrent Fault Protection）：
文档中提到的过流保护主要涉及CS引脚电压达到1.5V时的额外保护。
当CS引脚电压达到1.5V时，这会导致UVLO重置和重启序列。结论：与过压保护类似，过流保护触发后，设备也会通过UVLO重置和重启序列自动恢复，无需重新上电。
UVLO（欠压锁定）重置和重启序列：
UVLO是一个常见的电源管理特性，用于确保在电源电压过低时不会尝试启动或继续操作。
当电源电压上升到UVLO阈值以上时，设备会执行重置和重启序列以恢复正常操作。结论：UVLO重置和重启序列是设备自动恢复的一种机制，在电源电压恢复后，设备会自行恢复到正常操作状态。
综上所述，对于UCC28740来说，如果触发了过压或过流保护，设备会在故障后通过UVLO重置和重启序列自动恢复到正常操作状态，而无需重新上电。然而，如果故障条件持续存在（例如电源电压一直低于UVLO阈值或温度一直高于过热保护阈值），则设备可能无法成功启动或恢复到正常操作状态。在这种情况下，需要检查并解决故障条件，以便设备能够正常启动和运行。
