Capacitive sensing enabled switch mode power supply and data transfer

• US 9,496,793 B2
• Filed: 10/31/2012
• Issued: 11/15/2016
• Est. Priority Date: 11/01/2011
• Status: Expired due to Fees

• Current Assignee: Azoteq Pty Ltd.
• Original Assignee: Azoteq Pty Ltd.
• Inventors: Bruwer, Frederick Johannes, Van Wyk, Daniel, Doorduin, Willem Adriaan
• Primary Examiner(s): White, Dylan
• Application Number:
  US14/355,564
• Publication Number:
  US 20140253032A1
• Time in Patent Office: 1,476 Days
• Field of Search: 315/291
• US Class Current: 1/1
• CPC Class Codes: G01R 27/2605 Measuring capacitance capacitive sensors G01D5/24
• CPC Class Codes: H02J 50/10 using inductive coupling
• CPC Class Codes: H02M 1/0006 Arrangements for supplying an adequate voltage to the control circuit of converters
• CPC Class Codes: H02M 1/0032 Control circuits allowing low power mode operation, e.g. in standby mode
• CPC Class Codes: H02M 1/36 Means for starting or stopping converters
• CPC Class Codes: H02M 3/33507 with automatic control of the output voltage or current, e.g. flyback converters H02M3/33561, H02M3/33569 take precedence
• CPC Class Codes: H02M 7/05 Capacitor coupled rectifiers
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

A microchip for control of a switch mode power supply (SMPS), with said microchip also having the ability to measure capacitance of an electrode or sense plate structure or structures, and use of a low power, power supply structure to supply said microchip, said power supply structure distinct from the main energy path via said SMPS to a load. The microchip may control said SMPS to transition between an active state and an inactive state, with the measured capacitance used to determine a condition for state transition. In said SMPS inactive state, only the microchip draws power to operate its capacitive sensing circuitry, leading to a significant SMPS standby losses decrease compared to prior art. Further teachings by the present invention include capacitive sensing based data transfer, universal charging platforms for mobile devices, noise immunity enhancements, various lighting embodiments as well as SMPS operation improvements.

Claims

1. A microchip for use in a switch mode power supply (SMPS) circuit, wherein said SMPS circuit is used to convert alternating current (AC) power to direct current (DC) power in order to energize a load, wherein said microchip is a controller for and connected to said SMPS circuit and characterised in that said microchip also comprises Charge Transfer (CT) measurement circuitry, and wherein said CT measurement circuitry is active and powered from the AC power through a secondary power supply circuit when the SMPS circuit is in an inactive state, and wherein measurements by said CT measurement circuitry are used to determine a condition for activation of said SMPS circuit.

2. The microchip of claim 1, wherein said CT measurement circuitry is connected to a sensor, wherein said microchip monitors for a predetermined change in a parameter being measured with the sensor and the CT measurement circuitry, and wherein a detection of said change is used by the microchip to determine a condition for activation of said SMPS circuit.

3. The microchip of claim 2, wherein said sensor is an electrode or sense plate structure, and said parameter is a capacitance of said electrode or sense plate structure.

4. The microchip of claim 2 wherein said SMPS circuit includes at least one main switching element and wherein the microchip uses a count of state changes of said at least one switching element or elements of said switch mode power supply within a limited period to monitor said load, and wherein load status is used in conjunction with said measured parameter to determine a condition for SMPS circuit activation or deactivation by said microchip.

5. The microchip of claim 4, wherein said SMPS circuit is used in a product, and wherein said microchip enters said SMPS circuit into an inactive state due to at least one of the following:

a) said microchip detects that said load is less than a predetermined minimum;

b) an indication given by said product to said microchip; and

c) user touch or proximity gestures discerned by said microchip from CT measurements of an electrode or sense plate structure capacitance, wherein said electrode or sense plate structure functions as said sensor.

6. The microchip of claim 2, wherein said SMPS circuit includes at least one main switching element, wherein said parameter measurement is not performed during periods when said at least one switching element is changing from an open state to a closed state, or vice versa, or during voltage transients resulting from said state change.

7. The microchip of claim 2 wherein said load is a light generating element, and wherein an amount of light emitted by said element is directly controlled by said SMPS circuit controller according to user touch or proximity gestures detected by said microchip on or in the vicinity of an electrode or sense plate structure, wherein said electrode or sense plate structure functions as said sensor, and wherein said detection is based on changes in a capacitance of said electrode or sense plate structure measured by said CT measurement circuitry of said microchip.

8. The microchip of claim 7 wherein a detection of user proximity to a product by said microchip causes it to activate a Find-in-the-Dark indicator, said indicator powered via said secondary power supply circuit or via an output of said SMPS circuit, and wherein said light generating element is activated by said microchip if it detects a user touch gesture within a predetermined period after said proximity detection, wherein the amount of light emitted by said element is controlled by said microchip according to user touch sequences detected by said microchip, and wherein a housing of said product is used as said electrode or sense plate structure for said proximity detection.

9. The microchip of claim 2 wherein said SMPS circuit is used with two or more light generating elements as loads in a product, and wherein amounts of light emitted by said elements are directly controlled by said SMPS circuit controller, said control based on user effected changes in said measured parameter, and wherein at least one of said elements emits white light, and at least one of said elements emits coloured light, and wherein said controller can control all loads separately or simultaneously, and wherein said controller optimizes SMPS circuit operation based on selected light sources and the amount of light emitted.

10. The microchip of claim 2 wherein a cable between said load and said SMPS circuit is used as said sensor, and wherein said parameter is a capacitance of said cable.

11. The microchip of claim 10 wherein projected- or self-capacitance is measured.

12. The microchip of claim 1, wherein said microchip utilizes an improved Signal to Noise Ratio, in terms of CT measurements, achieved when the switch mode power supply circuit is inactive and power is only supplied via said secondary power supply circuit, for selecting a further action.

13. The microchip of claim 12 wherein more than one rectifying path is used to convert an AC voltage to a DC voltage, with a first rectifying path using a full-wave diode bridge and said SMPS circuit, and wherein a second rectifying path uses a full- or half-wave diode bridge and a structure that is not a SMPS circuit to supply power to said microchip, by causing a sufficient voltage drop over at least two capacitors in series with diodes of said second rectifying path, and wherein the DC-blocking ability of said capacitors allows the grounds of said first and said second rectifying paths to be connected.

14. The microchip of claim 1 wherein the secondary power supply circuit, which is not a SMPS circuit, consumes less power than said SMPS circuit.

15. The microchip of claim 1, wherein data relevant to the control of said SMPS circuit by said controller is transferred across an isolation barrier in said SMPS circuit, and characterised by the use of said CT measurement circuitry to demodulate said data after said transfer.

16. The microchip of claim 1, wherein said microchip keeps a DC voltage bus in an active state when said SMPS circuit is in an inactive state, and wherein said active state of said DC bus allows said controller to decrease the time required to return said SMPS circuit to an active state.

17. The microchip of claim 1, wherein said load is a light generating element, wherein said CT measurement circuitry is connected to a sensor, wherein said microchip monitors for a predetermined change in a parameter being sensed by said sensor, and wherein detection of said change affects the control of said load by said microchip.

18. The microchip of claim 1 used in a product, wherein said load is a light generating element, and wherein a first signal proportional to the operating temperature of said product is fed back to said microchip, and wherein said first signal is used in conjunction with or apart from a second signal, said second signal being proportional to a current flowing through said load, to control the operation of said SMPS circuit.

19. The microchip of claim 1, wherein said load is a light generating element, and wherein said microchip receives commands, wherein said commands are remotely generated and communicated to said microchip, and wherein execution of said commands by said microchip results in an operation change for the load.