HIGH FREQUENCY CONNECTOR-LESS CHARGING SCHEME

• US 20080116846A1
• Filed: 04/18/2007
• Published: 05/22/2008
• Est. Priority Date: 08/04/2006
• Status: Active Grant

• Current Assignee: Intersil Americas LLC (Renesas Electronics Corporation)
• Original Assignee: Intersil Americas LLC (Renesas Electronics Corporation)
• Inventors: RADHAKRISHNAN, GURUPRAKASH, GREENFELD, FRED
• Granted Patent: US 7,876,067 B2
• Time in Patent Office: Days
• US Class Current: 320/108
• CPC Class Codes: H02J 50/10 using inductive coupling
• CPC Class Codes: H02J 50/70 involving the reduction of electric, magnetic or electromagnetic leakage fields
• CPC Class Codes: H02J 7/00 Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries

Abstract

A connector-less charging circuit includes a transformer having a primary side associated with a secondary side. A primary switch is responsive to a control signal for connecting the transformer to ground during a first portion of a duty cycle, and disconnecting the transformer from ground during the second portion of the duty cycle. An active clamp circuit connects to the primary side of the transformer for recycling leakage energy from the transformer back to the source responsive to the control signal during the second portion of the duty cycle. A PWM controller generates the control signal to both the active clamp circuit and the primary switch.

Claims

1. A connector-less charging circuit, comprising:

a transformer having a primary side for coupling a charging voltage to a secondary side of the transformer, the primary side removably associated with the secondary side;

a primary switch responsive to a control signal for connecting the transformer to ground during a first portion of a duty cycle and disconnecting the transformer from ground during a second portion of the duty cycle;

an active clamp circuit connected to the primary side of the transformer for recycling leakage energy from the transformer back to the source responsive to the control signal during the second portion of the duty cycle; and

a PWM controller for generating the control signal.

2. The connector-less charging circuit of claim 1, wherein the secondary side of the transformer comprises an asymmetrically wrapped center tapped transformer.

3. The connector-less charging circuit of claim 2, further including an output capacitor, wherein the output capacitor is peaked charged by a first portion of the asymmetrically wrapped center tapped transformer during the first portion of the duty cycle and by a second portion of the asymmetrically wound center tapped transformer during the second portion of the duty cycle.

4. The connector-less charging circuit of claim 1, wherein the active clamp circuit further includes:

a clamp capacitor; and

a p-channel transistor switch for connecting the clamp capacitor to ground during the second portion of the duty cycle.

5. The connector-less charging circuit of claim 1, wherein the PWM controller comprises a single-ended controller.

6. The connector-less charging circuit of claim 1, wherein circuit operates at a frequency of at least 300 kilohertz.

7. The connector-less charging circuit of claim 1, wherein the primary side of the transformer further comprises a core half with a winding wrapped around one leg of the core half.

8. The connector-less charging circuit of claim 7, wherein the secondary side of the transformer further comprises:

two sets of windings configured to slide over the primary side of the transformer; and

wherein the core-winding combination of the primary side of the transformer is inserted concentrically within the secondary windings to enable electrical coupling between the primary side and the secondary side.

9. The connector-less charging circuit of claim 8, wherein an amount of coupling is responsive to an airgap between the primary core and secondary core halves.

10. A connector-less charging circuit, comprising:

a transformer having a primary side for coupling a charging voltage to a secondary side of the transformer, the primary side removably associated with the secondary, wherein the secondary side of the transformer comprises an asymmetrically wrapped center tapped transformer;

a primary switch responsive to a control signal for connecting the transformer to ground during a first portion of a duty cycle and disconnecting the transformer from ground during a second portion of the duty cycle;

an active clamp circuit connected to the primary side of the transformer for recycling leakage energy from the transformer back to the source responsive to the control signal during the second portion of the duty cycle, wherein the active clamp circuit further includes;

a clamp capacitor; and

a p-channel transistor switch for connecting the clamp capacitor to ground during the second portion of the duty cycle; and

a PWM controller for generating the control signal.

11. The connector-less charging circuit of claim 10, further including an output capacitor, wherein the output capacitor is peak charged by a first portion of the asymmetrically wrapped center tapped transformer during the first portion of the duty cycle and by a second portion of the asymmetrically wrapped center tapped transformer during the second portion of the duty cycle.

12. The connector-less charging circuit of claim 10, wherein the PWM controller comprises a single-ended controller.

13. The connector-less charging circuit of claim 10, wherein circuit operates at a frequency of at least 300 kilohertz.

14. The connector-less charging circuit of claim 10, wherein the primary side of the transformer further comprises:

a core having at least one leg; and

a winding wrapped around the at least one leg.

15. The connector-less charging circuit of claim 14, wherein the secondary side of the transformer further comprises:

two sets of windings configured to slide over the primary side of the transformer; and

wherein the core-winding combination of the primary side of the transformer is inserted concentrically within the secondary windings to enable electrical coupling between the primary side and the secondary side.

16. A system, comprising:

a charging base station defining a charging bay therein;

a portable electronic device configured to fit within the charging bay of the charging base station;

charging circuitry for providing a charging voltage to the portable electronic device in the charging bay, the charging circuitry comprising;

a transformer having a primary side within the charging base station for coupling the charging voltage to a secondary side of the transformer within the portable electronic device, the primary side removably associated with the secondary;

a primary switch within the charging base station responsive to a control signal for connecting the transformer to ground during a first portion of a duty cycle and disconnecting the transformer from ground during a second portion of the duty cycle;

an active clamp circuit connected to the primary side of the transformer within the charging base station for recycling leakage energy from the transformer back to the source responsive to the control signal during the second portion of the duty cycle; and

a PWM within the charging base station controller for generating the control signal.

17. The system of claim 16, wherein the secondary side of the transformer within the portable electronic device comprises an asymmetrically wrapped center tapped transformer.

18. The system of claim 17, further including an output capacitor within the portable electronic device, wherein the output capacitor is peak charged by a first portion of the asymmetrically wrapped center tapped transformer during the first portion of the duty cycle and by a second portion of the asymmetrically wrapped center tapped transformer during the second portion of the duty cycle.

19. The system of claim 16, wherein the active clamp circuit further includes:

a clamp capacitor; and

a p-channel transistor switch for connecting the clamp capacitor to ground during the first portion of the duty cycle.

20. The system of claim 16, wherein the PWM controller comprises a single-ended controller.

21. The system of claim 16, wherein system operates at a frequency of at least 300 kilohertz.