Digital feedback power supply

• US 5,969,514 A
• Filed: 11/24/1997
• Issued: 10/19/1999
• Est. Priority Date: 11/24/1997
• Status: Expired due to Term

• Current Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Original Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Inventors: Merrill, Richard B.
• Primary Examiner(s): Riley, Shawn
• Application Number:
  US08/977,314
• Time in Patent Office: 694 Days
• Field of Search: 323/282, 323/271, 323/272, 323/284, 323/283
• US Class Current: 323/283
• CPC Class Codes: H02M 3/157 with digital control
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load
• CPC Class Codes: H03K 17/122 in field-effect transistor switches

Abstract

A digital feedback power supply circuit capable of adjusting the flow of power to a load includes a switching array having a plurality of switches. Each of the plurality of switches is individually controlled by a control circuit. A monitoring circuit measures the output voltage level at an output node and sends this measured output voltage to the control circuit as a feedback signal. The control circuit then compares the measured output voltage level with a reference voltage value. Based on this comparison, the control circuit determines how many of the switches contained in the switching array need to be active to satisfy the power drawn by the load. When the load requires more power, the control circuit sends control signals to turn ON a particular number of inactive switches to satisfy the power drawn by the load. In contrast, when the load requires less power, the control circuit sends control signals to turn OFF a particular number of active switches so that no more than the required power is delivered to the load.

Claims

1. An apparatus including an integrated digital feedback power supply circuit for providing a signal to an external circuit, the digital feedback power supply circuit comprising:

an output node configured to couple to an external circuit and convey an output power signal, wherein an amount of power the external circuit draws varies;

a switching array circuit comprising three or more switches, each of the three or more switches being individually controlled to provide a switching output signal;

an output circuit coupled to the switching array circuit and configured to receive the switching output signal and in accordance therewith generate the output power signal to the output node;

a monitoring circuit coupled to the output node and configured to monitor the output power signal from the output circuit and in accordance therewith generates a digital feedback signal; and

a control circuit coupled between the monitoring circuit and the switching array circuit,

wherein when the control circuit receives the digital feedback signal from the monitoring circuit, the control circuit compares a magnitude of the digital feedback signal to a reference signal value to determine a number of the three or more switches that need to be active to satisfy the amount of power drawn by the external circuit.

2. The apparatus of claim 1, wherein the number of the three or more switches that need to be active to satisfy the amount of power drawn by the external circuit may be successively arranged from a minimum voltage level, wherein none of the three or more switches are active, to a maximum voltage level wherein the three or more switches are active.

3. The apparatus of claim 2, wherein when the digital feedback signal changes, the control circuit adjusts the number of the three or more switches that are active.

4. The apparatus of claim 1, wherein the three or more switches comprise three or more transistors.

5. The apparatus of claim 1, wherein the output circuit comprises an inductor and a capacitor.

6. An apparatus including an integrated digital feedback power supply circuit for providing a power signal to an external circuit, the digital feedback power supply circuit comprising:

an output node configured to couple to an external circuit and convey an output power signal, wherein an amount of power the external circuit draws varies;

a switching array circuit comprising a plurality of switches wherein each of the plurality of switches is individually controlled to provide a switching output signal;

an output circuit coupled to the switching array circuit and configured to receive the switching output signal and in accordance therewith generate the output power signal to the output node;

an analog-to-digital circuit coupled to the output node and configured to monitor the output power signal from the output circuit and in accordance therewith generate a feedback signal; and

a digital logic control circuit coupled between the monitoring circuit and the switching array,

wherein when the digital logic control circuit receives the feedback signal from the monitoring circuit, the digital logic control circuit compares a magnitude of the feedback signal to a reference signal value to determine a number of the plurality of switches that need to be active to satisfy the amount of power drawn by the external circuit.

7. The apparatus of claim 6, wherein the plurality of switches comprises at least three switches.

8. The apparatus of claim 6, wherein the plurality of switches comprise a plurality of transistors.

9. The apparatus of claim 6, wherein the output circuit comprises an inductor and a capacitor.

10. The apparatus of claim 6, wherein the number of the plurality of switches that need to be active to satisfy the amount of power drawn by the external circuit may be successively arranged from a minimum voltage level, wherein none of the plurality of switches is active, to a maximum voltage level wherein the plurality of switches is active.

11. The apparatus of claim 10, wherein when the feedback signal changes, the logic control circuit adjusts the number of the plurality of switches that are active.

12. A method of controlling an integrated digital feedback power supply circuit to provide a power signal to an external circuit, the method comprising the steps of:

generating an output power signal;

receiving the output power signal by an output node and conveying the first output power signal to an external circuit, wherein an amount of power the external circuit draws varies;

monitoring the output power signal from the output node and in accordance therewith generating a digital feedback signal;

comparing a magnitude of the digital feedback signal with a reference signal value;

determining, based on the comparison of the magnitude of the digital feedback signal with the reference signal value, a number of three or more switches that need to be active to satisfy the amount of power drawn by the external circuit; and

generating a plurality of control signals, wherein the control signals individually controls the plurality of switches, which activates the number of the three or more switches that need to be active to satisfy the amount of power drawn by the external circuit.

13. The method of claim 12, wherein when the number of the three or more switches that need to be active are activated, a remainder of the three or more switches is inactive.

14. The method of claim 12, wherein when the magnitude of the feedback signal exceeds the reference value, at least one of the three or more switches that is active, is deactivated.

15. The method of claim 12, wherein when the magnitude of the feedback signal is less than the reference value, at least one of the three or more switches that is inactive, is activated.

16. The method of claim 12, wherein the three or more switches comprise three or more transistors.

17. A method of controlling an integrated digital feedback power supply circuit to provide a power signal to an external circuit, the method comprising the steps of:

generating an output power signal;

receiving the output power signal by an output node and conveying the first output power signal to an external circuit, wherein an amount of power the external circuit draws varies;

monitoring the output power signal from the output node and in accordance therewith generating a feedback signal;

comparing a magnitude of the feedback signal with a reference signal value;

determining, based on the comparison between the magnitude of the feedback signal and the reference signal value, a number of a plurality of switching transistors that need to be turned on to satisfy the amount of power drawn by the external circuit; and

generating a plurality of control signals to turn on or turn off at least one of the plurality of switching transistors, wherein

when the magnitude of the feedback signal transcends the reference signal value in a first direction, at least one of the switching transistors that is active is deactivated to decrease the amount of power supplied to the external circuit, and

when the magnitude of the feedback signal transcends the reference signal value in a second direction, at least one of the switching transistors that is inactive is activated to increase the amount of power supplied to the external circuit.