NE1187 is a high-performance resonator controller dedicated to the half-bridge LLC topology with high integration, high precision and high efficiency.
The NE1187 high voltage side switch and low voltage side switch drive the switch at a 180° out-of-phase complementary Angle in the same cycle, providing a high stable and reliable complementary duty cycle with a fixed dead zone. And a fixed dead time is added between the switches of the high and low switching tubes to ensure the realization of the soft switch and the operation of the high frequency switching state.
The NE1187 achieves output voltage regulation by adjusting the operating switching frequency, and the converter‘s operating frequency range can be set by setting an external oscillator with the pin.
In order to prevent boot surge, the chip is designed with a special soft start circuit. When starting, the switching frequency starts from the maximum designed value and gradually decreases through the control loop until the frequency is stabilized. The frequency adjustment is completely controlled by the loop control, which can effectively reduce the output voltage overshoot degree; The entire startup process time can be set by peripheral parameters.
The main loss of switching power supply under light load is switching loss, and NE1187 works in Burst mode during light load, which effectively reduces switching loss and improves light-load efficiency.