Multiple, well-regulated voltages are very important to reduce power consumption and to isolate the coupling noise between different functional blocks in VLSI applications requiring multiple supplies. With the proliferated number of functional blocks in these applications, the need for a cost and efficiency effective solution is looming. Single-Inductor-Multiple-Output (SIMO) switching regulator, which provides several output voltages with only one inductor, becomes a hot research topic due to the reduced cost and volume. However, with one inductor shared by all the outputs to accumulate and transfer energy from input, cross regulation easily appears at outputs when a change in the inductive energy is induced by a load transient at one output. These unwanted voltage variations af...[ Read more ]

Multiple, well-regulated voltages are very important to reduce power consumption and to isolate the coupling noise between different functional blocks in VLSI applications requiring multiple supplies. With the proliferated number of functional blocks in these applications, the need for a cost and efficiency effective solution is looming. Single-Inductor-Multiple-Output (SIMO) switching regulator, which provides several output voltages with only one inductor, becomes a hot research topic due to the reduced cost and volume. However, with one inductor shared by all the outputs to accumulate and transfer energy from input, cross regulation easily appears at outputs when a change in the inductive energy is induced by a load transient at one output. These unwanted voltage variations affect the performance or even the function of the loading devices. In addition, the efficiency of the regulator will degrade with more switches introduced to control the energy delivery. High efficiency SIMO switching regulators with independent and well-regulated output voltages are in great demand.

The aim of this research is to develop SIMO switching regulators with minimized loss, well-regulated output voltages independent of each other. First, the topology and loss property of SIMO switching regulators are investigated. A systematic method is introduced to extend the conversion ratio of each output. Optimized switching schemes are discussed to reduce conduction loss and boost the efficiency of SIMO switching regulators with reduced inductor average current and inductor current ripple. In addition, power loss and switching noise mechanisms for multiple-output converters are also proposed. A sequential controlled Single-Inductor-Dual-Output (SIDO) boost switching regulator is used to analyze the parasitics of the power stage. The mechanisms of the power loss and switching noise induced by these parasitic are presented. A four-transistor based low Shoot-Through-Current (STC) driver with two separate High-Voltage-Selectors (HVSs) are used to reduce the power loss and switching noise.

To minimize cross regulation of a SIMO switching regulator, a SIDO boost switching regulator with Constant-Charge-Auto-Hopping (CCAH) control based on sequential control is proposed. Flexible driving capability as well as minimized cross-regulation can be achieved. Frequency hopping is adopted to further extend the power capability with a predictable noise spectrum. An inductor peak current prediction method that adaptively adjusts ramp charging current is introduced to minimize cross-regulation as well as enable faster transient response.

For the above method with a voltage-mode PWM controller, the transient response is limited by the proportional-integral (PI) compensators. A SIDO boost switching regulator with current-mode hysteretic control is proposed. A high frequency clock is introduced to synchronize the system to enable a predictable noise spectrum. The outputs can operate at either Continuous-Conduction-Mode (CCM) or Discontinuous-Conduction-Mode (DCM), depending on the loads. Without a low band-width compensation loop, the system has ultra fast transient response. Minimized cross-regulation can be achieved due to the fast detection and transfer of the proper energy for all of the outputs.