Multirange load detection circuitry

• US 8,575,917 B2
• Filed: 09/24/2009
• Issued: 11/05/2013
• Est. Priority Date: 09/24/2009
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Sims, Nicholas A., Terlizzi, Jeffrey J.
• Primary Examiner(s): VALONE, THOMAS F
• Application Number:
  US12/566,593
• Publication Number:
  US 20110068819A1
• Time in Patent Office: 1,503 Days
• Field of Search: 324/771
• US Class Current: 324/120
• CPC Class Codes: G01R 31/40 Testing power supplies testing photovoltaic devices H02S50/10
• CPC Class Codes: H02J 9/007 Detection of the absence of a load
• CPC Class Codes: H02J 9/06 with automatic change-over , e.g. UPS systems

Abstract

Load detection circuitry is provided that may be used to monitor an output line. The load detection circuitry may include one or more current sensing resistors. A monitor circuit can measure voltages across the current sensing resistors to determine whether current is flowing through a load connected to the output line. In configurations with multiple different current sensing resistors, the monitor circuit can determine the amount of current that is flowing through the load based on the measured voltages. A switch may be interposed between the current sensing resistor and the output line. A current-limited voltage regulator may supply a voltage to the output line. The monitor circuit may periodically open the switch and monitor resulting voltage changes on the output line to determine whether an electronic device or other load is attached. Opening of the switch may be inhibited whenever current is sensed through a current sensing resistor.

Claims

1. A power converter providing a DC voltage through a power converter output, the power converter comprising:

a first stage comprising an AC to DC power converter comprising a first terminal configured to receive an AC line voltage and a second terminal configured to deliver a first DC voltage wherein the second terminal is coupled to a first intermediate node;

a second stage comprising a voltage regulator comprising a third terminal coupled to the first intermediate node and a fourth terminal coupled to a second intermediate node, wherein the second stage is configured to provide a second DC voltage with a limited amount of current to the second intermediate node through the fourth terminal;

a switch disposed between the first intermediate node and the second intermediate node;

an energy storage device coupled to the first intermediate node and configured to store energy from and deliver energy to the first intermediate node; and

a control circuit configured to operate the first stage and the switch,

whereby the second intermediate node is coupled to the first intermediate node by the switch when the first stage is in an active state and the first and second stages provide power to the second intermediate node,

whereby the second intermediate node is isolated from the first intermediate node by the switch when the first stage is in a standby state and only the second stage provides power to the second intermediate node,

wherein the second intermediate node is coupled to the power converter output.

2. The power converter of claim 1, wherein the control circuit is configured to put the first stage in the standby state when the output voltage of the power converter rises.

3. The power converter of claim 2, wherein the energy storage device is configured to provide stored energy to the second stage when the first stage is in the standby state.

4. The power converter of claim 3, wherein the control circuit is configured to transition the first stage from the standby state to the active state when the stored energy in the energy storage device is less than a stored energy threshold.

5. The power converter of claim 1, wherein the control circuit is further configured to configure the switch to couple the first intermediate node to the second intermediate node when a load current is less than a first load current threshold and greater than a second load current threshold.

6. The power converter of claim 1, wherein the control circuit is configured to determine output load status by monitoring a voltage of the second intermediate node when the first stage is in a standby state.

7. A power converter for converting an AC line voltage to a DC voltage, the converter comprising:

an AC to DC converter stage comprising a first terminal coupled to the AC line voltage and a second terminal coupled to a first intermediate node, wherein the AC to DC converter stage is configured to provide a DC voltage to the second terminal;

a current sensing resistor comprising a first resistor terminal coupled to the first intermediate node and a second resistor terminal coupled to a second intermediate node;

a voltage regulator stage comprising a third terminal coupled to first intermediate node and a fourth terminal coupled to the second intermediate node, wherein the voltage regulator stage is configured to receive power from the third terminal and provide a limited amount of current to the fourth terminal; and

a controller coupled to the first intermediate node, the first and the second resistor terminals of the current sensing resistor and the second intermediate node, the controller configured to put the AC to DC converter in a standby mode when a sensed current is less than a predetermined current threshold and allow only the voltage regulator stage to provide output power for the power converter when the AC to DC converter is in the standby mode,

wherein the second intermediate node is coupled to an output for the power converter.

8. The power converter of claim 7, further comprising a switch disposed between the second resistor terminal of the current sensing resistor and the second intermediate node, wherein a first switch terminal is coupled to the second resistor terminal of the current sensing resistor and a second switch terminal is coupled to second intermediate node.

9. The power converter of claim 8, wherein the controller is coupled to a control terminal of the switch and is configured to control the state of the switch.

10. The power converter of claim 9, wherein the controller is configured to open the switch when a voltage drop across the current sensing resistor is less than a predetermined amount.

11. The power converter of claim 10, wherein the controller is configured to place the AC to DC converter stage in a standby state when the switch is open.

12. The power converter of claim 7, further comprising an energy storage element coupled to the first intermediate node and configured to provide power to the voltage regulator when the AC to DC converter stage is in a standby state.

13. The power converter of claim 12, further comprising a switch disposed between the second resistor terminal of the current sensing resistor and the second intermediate node wherein a first switch terminal is coupled to the second resistor terminal of the current sensing resistor and a second switch terminal is coupled to the second intermediate node.