Peak Current Servo

The proposed disclosure combines peak-mode monitoring with valley-mode control, in a Buck switching converter, by means of a peak-current sampling circuit, not to turn the high side device off, but to control a slow loop, which in turn controls a variable offset incorporated into the loop control current. This helps the loop control current define the exact peak current, regardless of what other offsets, compensation ramp or peak-to-peak current ripple, are applied to the loop control current. The peak current is determined by an operational transconductance amplifier (OTA), whose maximum current is clamped to a programmed value. The loop control current is most likely implemented using a digital successive approximation register (SAR) system, but may also be implemented using a slow analog control loop.