Synchronized power-up for multiple voltage system

• US 20040056532A1
• Filed: 09/25/2002
• Published: 03/25/2004
• Est. Priority Date: 09/25/2002
• Status: Active Grant

• Current Assignee: Dell Products LP A Texas Limited Partnership
• Original Assignee: Dell Products LP (Dell Technologies Inc.)
• Inventors: Rowe, Jeffrey R.
• Granted Patent: US 6,917,123 B2
• Time in Patent Office: Days
• US Class Current: 307/18
• CPC Class Codes: H02J 1/102 being switching converters H02J1/108, H02J1/12 take precedence

Abstract

A power-up control circuit controls the initial application of power to a system having multiple loads and multiple voltage supply levels. The control circuit causes the power to each load to rise equally, and limits the voltage levels to all loads to the lowest voltage being controlled by the control circuit. As each load reaches its target voltage, its voltage no longer limits the control circuit. The voltages to the remaining loads continue to rise, and loads whose target voltages are reached continue to drop out of the control circuit, until each load is receiving its target voltage.

Claims

1. A power-up control circuit for controlling the initial application of power to a system having multiple loads and multiple voltage supply voltage signals, comprising:

a feedback regulator associated with each load, connected between the load and its voltage supply signal, operable to control the voltage delivered to the associated load by limiting the voltage to the level of a setpoint signal;

a voltage finder operable to determine the setpoint signal by finding the minimum of the voltages from the feedback regulators, and to deliver the setpoint signal to each feedback regulator circuit; and

a cutout circuit connected to the output of each feedback regulator, operable to compare the associated feedback regulator output to a reference endpoint representing the voltage required by the associated load, and to cut out the associated feedback regulator output from the voltage finder when the voltage delivered to the associated load reaches the reference endpoint.

2. The circuit of claim 1, further comprising a ramp rate control circuit operable to equalize the rate at which the voltage to each load increases.

3. The circuit of claim 1, wherein each feedback regulator circuit has a pulse width modulator for modulating the voltage supply signal to the associated load.

4. The circuit of claim 3, wherein the pulse width modulator controls a pass transistor.

5. The circuit of claim 1, wherein the reference endpoint voltage associated with each load is equal to the voltage required by the load.

6. The circuit of claim 1, wherein the reference endpoint voltage associated with each load is greater than the voltage required by the load.

7. The circuit of claim 1, wherein the voltage finding circuit has a diode associated with each load, such that the anode of each diode is connected to a setpoint node and the cathode of each diode is connected to the output of the feedback regulator of the associated load.

8. The circuit of claim 1, wherein the cutout circuit has means for comparing two input signals and a cutout transistor responsive to the means for comparing.

9. A method of powering-up a system having multiple loads and multiple voltage supply lines, which provide at least two different input voltages, comprising the steps of:

connecting a feedback regulator between each load and its input voltage supply;

applying power to the voltage supplies;

generating a setpoint signal by finding the minimum of a set of feedback regulator outputs;

delivering the setpoint signal to each feedback regulator;

limiting the voltage delivered to each load, by using the setpoint signal to limit the output of the feedback regulators;

determining when any feedback regulator is delivering a voltage equal to an endpoint voltage for the associated load;

removing, from the set of feedback regulator outputs being used to find the setpoint, the feedback regulator output of any load receiving its endpoint voltage; and

repeating the generating, delivering, limiting, determining, and removing steps until each load is receiving its endpoint voltage.

10. The method of claim 9, further comprising the step of controlling the ramp rate of the setpoint such that the voltage to each load rises at an equal rate.

11. The method of claim 9, wherein the limiting step is performed by pulse width modulating the voltage supply signal to the associated load.

12. The method of claim 9, wherein the determining step is performed for each load by comparing the reference endpoint voltage for that load to the output of the feedback regulator associated with that load.

13. The method of claim 9, wherein the endpoint voltage associated with a load is substantially the same as the voltage required by that load.

14. The method of claim 9, wherein the endpoint voltage associated with a load is greater than the voltage required by the load.

15. The method of claim 9, wherein the generating step is performed by connecting diodes between each feedback regulator outputs and a setpoint node, such that the anodes of all diodes are connected to the setpoint node and the cathodes are connected to the respective feedback regulator outputs.

16. The method of claim 9, wherein at least the generating step is performed with digital circuitry.

17. The method of claim 9, wherein the method is performed with analog circuitry.