Linear AC to DC regulator with synchronous rectification

• US 6,404,173 B1
• Filed: 07/28/2000
• Issued: 06/11/2002
• Est. Priority Date: 07/28/2000
• Status: Expired due to Term

• Current Assignee: Dialog Semiconductor Incorporated (Renesas Electronics Corporation)
• Original Assignee: iWatt, Inc. (Renesas Electronics Corporation)
• Inventors: Telefus, Mark D.
• Primary Examiner(s): NGUYEN, MATTHEW VAN
• Application Number:
  US09/627,953
• Time in Patent Office: 683 Days
• Field of Search: 323/220, 323/223, 323/226, 323/268, 323/270-273, 323/282
• US Class Current: 323/272
• CPC Class Codes: G05F 1/56 using semiconductor devices in series with the load as final control devices G05F1/461 takes precedence

Abstract

A power supply having a plurality of bi-directional switches coupled in parallel between an input and an output regulates the output voltage by altering the number of conducting bi-directional switches in response to power demands at the output.

Claims

1. AC to DC linear power regulator, comprising:

an input;

an output;

a plurality of bi-directional switches coupled in parallel between the input and output, each bi-directional switch comprising a pair of saturated, series-connected field effect transistors, wherein the series-connected field effect transistors in each pair are coupled source to source; and

a controller for switching ON a subset of the plurality of bi-directional switches while switching OFF the remainder of the plurality of bi-directional switches, wherein the controller varies the size of the subset in response to sensing a power demand at the output such that the controller regulates an output voltage.

2. The power regulator of claim 1, wherein each bi-directional switch comprises a transmission gate.

3. The power regulator of claim 1, wherein the controller switches ON the subset of bi-directional switches in response to comparing the output voltage to a reference voltage.

4. The power regulator of claim 1, wherein the controller switches ON the subset of bi-directional switches in response to comparing an output current to a reference current.

5. The power regulator of claim 1, wherein the controller further varies the size of the subset in response to anticipating a power demand at the output.

6. A method of providing linear AC to DC power regulation, comprising:

providing a plurality of bi-directional switches coupled in parallel between an input and an output, each bi-directional switch comprising a pair of saturated, series-connected field effect transistors coupled source to source, wherein a subset of the switches, when ON, define a resistance between the input and the output when the remainder of the plurality of switches are OFF; and

in response to sensing a power demand at the output;

varying the resistance between the input and the output by varying the size of the subset of ON switches, whereby a voltage at the output is regulated.

7. The method of claim 6, further comprising:

applying an AC voltage at the input; and

controlling the subset of ON switches to only be ON when the AC voltage input is greater than a positive output voltage, whereby synchronous rectification is achieved.

8. The method of claim 6, further comprising:

applying an AC voltage at the input; and

controlling the subset of ON switches to only be ON when the AC voltage input is less than a negative output voltage, whereby synchronous rectification is achieved.