Abstract: A dual mode regulator, having a high current PWM regulator mode and a low current LDO regulator mode, briefly changes the operating parameters of the PWM and LDO regulators during a transition between modes. Changes during the transition period include: raising the error amplifier reference voltage of the LDO or PWM regulator to ensure a definite handover, raising the bias current in the LDO stages during the transition to cause the LDO regulator to quickly and stably respond to voltage glitches, and augmenting the LDO regulator series pass transistors with one or more additional pass transistors during the transition to enable the LDO regulator to handle higher currents. After the transition, the operating parameters of the enabled regulator portion are reset to their nominal values. The PWM regulator is started with a soft start routine to limit current through the power transistor.

Abstract: A method for starting up a voltage-mode switching power supply into a biased load includes computing a ratio of the load voltage at the biased load to an input voltage of the switching power supply, generating a first signal indicative of the duty cycle of the voltage-mode switching power supply, comparing the first signal indicative of the duty cycle to the ratio, and turning on an output stage of the voltage-mode switching power supply only when the first signal indicative of the duty cycle is equal to the ratio. In this manner, the voltage-mode switching power supply can be started up to supply power to a biased load without dragging down the load voltage of the biased load.

Abstract: In master-slave current-tracking load-share systems using switching power supplies, a method and apparatus for preventing current recirculation at light-load and no-load operational conditions. The slave power supply is run in a discontinuous mode when load current falls to light-load or no-load state, preventing the slave from sinking current, therefore preventing recirculation from the master to the slave. The slave power supply is run at a lower current level than the master, preventing recirculation from the slave to the master.

Abstract: In master-slave current-tracking load-share systems using switching power supplies, a method and apparatus for preventing current recirculation at light-load and no-load operational conditions. The slave power supply is run in a discontinuous mode when load current falls to light-load or no-load state, preventing the slave from sinking current, therefore preventing recirculation from the master to the slave. The slave power supply is run at a lower current level than the master, preventing recirculation from the slave to the master.

Abstract: A switching regulator includes a compensation circuit for applying a scaling factor to the loop gain of the feedback control loop of the regulator. In operation, the loop gain of the feedback control loop has a dependency on the input and output voltages of the switching regulator. The compensation circuit applies a function as the scaling factor where the function is a reciprocal function of the loop gain dependency on the input voltage and output voltage. In one embodiment, the loop gain has a dependency on the ratio VIN/VOUT and a scaling factor having a value indicative of the ratio VOUT/VIN is applied by the compensation circuit. In one embodiment, the compensation circuit is coupled in series with the output circuit of an error amplifier in the feedback control loop of the regulator. In another embodiment, the compensation circuit is subsumed within the circuitry of the error amplifier.

Abstract: A current mode switching regulator implementing a dual sense scheme includes a first current sensing circuit for sensing a current through a first switch and providing a first current sense signal, and a second current sensing circuit for sensing a current through a second switch and providing a second current sense signal. The switching regulator includes a control circuit for generating switch control signals for driving the first and second switches in response to one of the first and second current sense signals. The regulator further includes a duty cycle detection circuit coupled to determine a duty cycle of the switching regulator. The detection circuit asserts a first select signal to select the first current sense signal when the duty cycle exceeds a first threshold level and asserts a second select signal to select the second current sense signal when the duty cycle is less than a second threshold level.