Start-up control in power systems using fixed-ratio power conversion

Apparatus comprising:

• a controller configured to operate one or more power switches in a series of power conversion cycles, the controller being configured to:
• (a) turn one or more of the power switches ON in a high resistance state in a first operational phase to increase an equivalent series resistance of the power converter;
• (b) turn the one or more of the power switches ON in a low resistance state in a second operational phase to decrease the equivalent series resistance of the bus converter;
• (c) adjust a drive level for the one or more power switches within a range during the first operational phase from an initial value for turning the one or more of the power switching elements ON with a highest switch resistance to a final value for turning the one or more of the power switching elements ON with a lowest switch resistance including:
• (i) determine whether a current meets or exceeds a predetermined limit;
• (ii) increment the drive level for the one or more power switches if the current does not meet or exceed the limit;
• (iii) repeat the above steps (i) and (ii) until a maximum drive level is reached;
• and
• (iv) exit the first operational phase after the maximum drive level is reached.

Apparatus comprising:

• a control circuit for controlling power delivery to a load, the control circuit being configured to:
• generate a load disable signal to disable a load during a start-up phase;
• generate a first signal to enable a power converter to convert power during the start-up phase after power is applied to the converter input, the first signal causing the power converter to operate one or more power switches in a high resistance state during the start-up phase to increase an equivalent series resistance of the power converter during the start-up phase;
• generate a second signal to enable the power converter to convert power during a steady-state phase after the start-up phase, the second signal causing the power converter to operate one or more power switches in a low resistance state during the steady-state phase to decrease an equivalent series resistance of the power converter during the steady-state phase;
• and
• remove the load disable signal for the steady state phase.

Apparatus comprising:

• a controller configured to operate one or more power switches in a series of power conversion cycles, during which power received from a power converter input at an input voltage, VIN, and input current, IIN, is converted for delivery to a power converter output at an output voltage, VOUT, and an output current, IOUT, during start-up and steady-state phases of operation using a transformation ratio, K, where K=VOUT/VIN, that is essentially constant;
• the controller being configured to operate the power switches in first conversion operation cycles in the steady-state phase;
• the controller being configured to operate the power switches in second conversion operating cycles in the start-up phase, the second conversion operating cycles differing from the first conversion operating cycles, the second operating cycles limiting inrush current or power dissipation in the power converter;
• the controller being configured to issue a signal to disable a load during the start-up phase;
• the controller being configured to selectively enable the power conversion in the start-up phase after power is applied to the converter input;
• and
• the controller being configured to remove the load disable signal to enable the load during the steady state phase.

Apparatus for delivering power from an input source at a source voltage, VS, to a load at a load voltage, VL, the apparatus comprising:

• a bus converter having a converter input, a converter output, a plurality of power switching elements, and a switch controller adapted to operate the power switching elements in a series of converter operating cycles during a start-up phase and during a steady-state phase of operation to convert power received from the converter input at an input voltage, VIN, and input current, IIN, for delivery to the converter output at an output voltage, VOUT, and an output current, IOUT, using a transformation ratio, K, where K=VOUT/VIN, that is essentially constant;
• the bus converter being adapted in the steady-state phase to turn one or more of the power switching elements ON for a first duration during each converter operating cycle;
• the bus converter being adapted in the start-up phase to turn one or more of the power switching elements ON for a second duration during each converter operating cycle to limit in-rush current of the bus converter, the second duration being shorter than the first duration;
• and
• a control circuit having an output to provide a control signal to disable the load during the start-up phase and to enable the load during the steady-state phase.

Apparatus for delivering power from an input source at a source voltage, VS, to a load at a load voltage, VL, the apparatus comprising:

• a bus converter having a converter input, a converter output, a plurality of power switching elements, and a switch controller adapted to operate the power switching elements in a series of converter operating cycles during a start-up phase and during a steady-state phase of operation to convert power received from the converter input at an input voltage, VIN, and input current, IIN, for delivery to the converter output at an output voltage, VOUT, and an output current, IOUT, using a transformation ratio, K, where K=VOUT/VIN, that is essentially constant;
• the bus converter being adapted in the steady-state phase to operate the power switching elements in a standard converter operating cycle, each standard operating cycle having a standard period;
• the bus converter being adapted in the start-up phase to operate the power switching elements in truncated operating cycles to limit in-rush current of the bus converter, the truncated operating cycles having a period that is shorter than the standard period;
• and
• a control circuit having an output to provide a control signal to disable the load during the start-up phase and to enable the load during the steady-state phase.