Monolithic Power Systems has introduced the HR1275, a digital ac-dc power controller which combines a PFC stage with a resonant LLC converter in a single chip.
The HR1275 has built-in power-saving features which help to achieve ultra-low standby power consumption, while maintaining high efficiency and a high power factor across the range from light to full loads. This makes the controller well suited to applications such as compact, high-power adapters which require both efficiency and flexibility.
The controller is configurable via a user-friendly GUI, allowing engineers to program and adjust many operating parameters, from soft-start timing and loop compensation to protection thresholds, which are stored in the chip’s non-volatile memory. This programmable digital core means that the same hardware can be quickly modified to meet different efficiency standards, noise targets, or load profiles without hardware changes. This greatly accelerates prototyping and design optimization.
The PFC controller in the HR1275 operates in both critical and discontinuous conduction modes to maximize efficiency across the load range. The controller uses intelligence to minimize switching losses and audible noise, and can drive the PFC stage at frequencies up to 400kHz. At light loads, a configurable soft burst-mode helps to maintain efficiency without compromising power quality.
In the LLC stage, the HR1275 adopts current-mode control with adaptive dead-time adjustment to ensure zero-voltage switching with minimal dead-time, improving efficiency and reducing heat dissipation.
An internal high-voltage start-up current source powers the chip directly from the ac line, eliminating the need for auxiliary power supply for the start-up and cutting standby power dissipation. Designers benefit from a built-in power-good indicator and the ability to connect an external temperature sensor.
