Power measurement for adaptive battery charger

• US 6,144,187 A
• Filed: 07/13/1999
• Issued: 11/07/2000
• Est. Priority Date: 11/12/1998
• Status: Expired due to Term

• Current Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Original Assignee: Fairchild Semiconductor Corporation (ON Semiconductor Corporation)
• Inventors: Bryson, Steven W.
• Primary Examiner(s): Riley, Shawn
• Assistant Examiner(s): LUK, LAWRENCE W
• Application Number:
  US09/352,437
• Time in Patent Office: 483 Days
• Field of Search: 320/137, 320/164, 320/160, 320/161, 320/162, 320/163
• US Class Current: 320/137
• CPC Class Codes: H02J 5/00 Circuit arrangements for transfer of electric power between ac networks and dc networks H02J3/36 takes precedence
• CPC Class Codes: H02J 7/0068 Battery or charger load switching, e.g. concurrent charging and load supply H02J7/0013 takes precedence
• CPC Class Codes: H02J 7/00712 the cycle being controlled or terminated in response to electric parameters
• CPC Class Codes: H02J 7/02 for charging batteries from ac mains by converters
• CPC Class Codes: Y02B 40/00 Technologies aiming at improving the efficiency of home appliances, e.g. induction cooking or efficient technologies for refrigerators, freezers or dish washers

Abstract

A highly flexible adaptive battery charger circuit that optimizes the efficiency of battery charging. The battery charger provides internal multiplier circuitry to measure input power allowing it to be used with AC adapters having different wattage. It further includes circuitry to digitally adjust threshold levels for the various control loops within the charger circuitry.

Claims

1. A battery charger circuit for an electronic device operated by a battery, the circuit comprising:

a voltage control loop adapted to couple to the battery to control a voltage level of the battery to a selected voltage level;

a current control loop adapted to couple to the battery to control current delivered to the battery at a selected current magnitude;

a power control loop adapted to couple to the battery and the electronic device to control the power drawn by the charger circuit to a selected power level; and

a combine circuit configured to combine outputs of the voltage control loop, current control loop and power control loop,

wherein, the power control loop comprises;

a current sense circuit having first and second input terminals adapted to couple across a current sense resistor,

a voltage input terminal configured to monitor an input supply voltage, and

a multiplier circuit having a first input coupled to an output of the current sense circuit, a second input coupled to the voltage input terminal, and an output, the multiplier circuit being configured to generate at its output a signal representative of the power draw from the charger circuit.

10. The battery charger circuit of claim 1 wherein the multiplier circuit comprises an analog multiplier circuit comprising:

a first log amplifier having an input coupled to receive the output of the current sense circuit;

a second log amplifier having an input coupled to receive the input supply voltage;

a summing amplifier having a first input coupled to an output of the first log amplifier, and a second input coupled to an output of the second log amplifier; and

an anti-log amplifier having an input coupled to an output of the summing amplifier.

11. The battery charger circuit of claim 10 wherein the current sense circuit comprises:

a level shift circuit having first and second inputs coupled to receive a current signal across the current sense resistor, the level shift circuit being configured to reduce a high voltage common mode component of the current signal to a lower voltage; and

an integrating differential amplifier coupled to the level shift circuit.

12. The battery charger of claim 11 wherein the level shift circuit comprises switched-capacitor circuitry configured to commutate the high voltage common mode component of the current signal to the lower voltage in response to non-overlapping clock signals.

13. The battery charger of claim 12 wherein the current sense circuit further comprises a sample and hold circuit coupled to the integrating differential amplifier.

2. A battery charger circuit for an electronic device operated by a battery, the circuit comprising:

a voltage control loop adapted to couple to the battery to control a voltage level of the battery to a selected voltage level;

a current control loop adapted to couple to the battery to control current delivered to the battery at a selected current magnitude;

a power control loop adapted to couple to the battery and the electronic device to control the power drawn by the charger circuit to a selected power level; and

a combine circuit configured to combine outputs of the voltage control loop, current control loop and power control loop,

wherein, the power control loop comprises;

a current sense circuit having first and second input terminals adapted to couple across a current sense resistor,

a voltage input terminal configured to monitor an input supply voltage,

a multiplier circuit having a first input coupled to an output of the current sense circuit a second input coupled to the voltage input terminal and an output, the multiplier circuit being configured to generate at its output a signal representative of the power draw from the charger circuit;

a first amplifier having a first input coupled to the output of the multiplier circuit, a second input, and an output; and

a first digital-to-analog converter having an output coupled to the second input of the first amplifier and a plurality of inputs configured to receive digital power control signal,

wherein, the selected power level is set by the digital power control signal.

3. The battery charger circuit of claim 2 wherein the current control loop comprises:

a second amplifier having first and second terminals adapted to couple across a second current sense resistor;

a third amplifier having a first input coupled to an output of the second amplifier; and

a second digital-to-analog converter having an output coupled to a second input of the third amplifier, and a plurality of inputs configured to receive digital current control signal,

wherein, the selected current magnitude is set by the digital current control signal.

4. The battery charger circuit of claim 3 wherein the voltage control loop comprises:

a fourth amplifier having a first input adapted to be coupled to the battery, a second input, and an output; and

a third digital-to-analog converter having an output coupled to the second input of the fourth amplifier and a plurality of inputs configured to receive digital voltage control signal,

wherein, the selected voltage level is set by the digital voltage control signal.

5. The battery charger circuit of claim 4 further comprising a charger control circuit having an input coupled to an output of the combine circuit and an output coupled to control the battery voltage or current or input power.

6. The battery charger circuit of claim 5 wherein the charger control circuit is a pulse-width-modulated DC-DC converter controller configured to compare the output of the combine circuit with a ramping signal.

7. The battery charger circuit of claim 6 wherein the combine circuit comprises circuitry configured to perform a logical OR function.

8. The battery charger circuit of claim 7 wherein the circuitry configured to perform a logical OR function comprises three common-collector bipolar transistors having their emitter terminal coupled together, and each having a base terminal coupled to respective output of first, third and fourth amplifiers.

9. The battery charger circuit of claim 4 wherein the first digital-to-analog converter (DAC)is a 4-bit DAC, and the second and third digital-to-analog converters are each 8-bit DACs.

14. An adaptive battery charger circuit comprising:

a current control loop having an amplifier with a first input coupled to a signal representing battery current and a second input coupled to an output of a digital-to-analog converter;

a voltage control loop having an amplifier with a first input coupled to a signal representing battery voltage and a second input coupled to an output of a digital-to-analog converter; and

a power control loop having an amplifier with a first input coupled to a signal representing input power and a second input coupled to an output of a digital-to-analog converter.

15. The adaptive battery charger circuit of claim 14 further comprising:

a combine circuit configured to combine outputs of the current control loop, voltage control loop and power control loop; and

a charger control circuit having an input coupled to the combine circuit and an output coupled to battery charging circuitry.

16. The adaptive battery charger circuit of claim 15 wherein each digital-to-analog converter sets a threshold level for its respective control loop in response to a digital control signal from a system controller.

17. A method of charging a battery for a battery-operated device, comprising the steps of:

sensing an input current supplied by a power supply source;

sensing an input voltage supplied by a power supply source;

calculating an input power by multiplying the sensed input current with the sensed input voltage;

detecting a magnitude of current being delivered to the battery;

detecting a voltage level of the battery; and

varying an amount of charge being supplied to the battery in response to the charging needs of the battery and the power needs of the battery-operated device.

18. The method of claim 17 wherein the step of varying comprises the steps of:

regulating the magnitude of current being delivered to the battery as long as the voltage level of the battery is below a selected level, and the calculated input power is below a maximum level;

regulating the voltage level of the battery when the voltage level of the battery reaches the selected level, and as long as the calculated input power is below the maximum level; and

limiting the amount of charge being supplied to the battery when the calculated input power reaches the maximum level.

19. A battery charging system for a battery-operated device, comprising:

an AC adapter configured to convert an AC power signal to a DC power signal; and

an adaptive battery charger circuit coupled to the AC adapter, the charger circuit comprising;

a power control loop configured to measure an amount of input power and to regulate an amount of charge being delivered to the battery based on a power threshold level,

a current control loop configured to sense an amount of current being delivered to the battery and to regulate an amount of charge being delivered to the battery based on a current threshold level, and

a voltage control loop configured to detect the battery voltage level and to regulate an amount of charge being delivered to the battery based on a voltage threshold level;

a controller coupled to the adaptive battery charger circuit,

wherein, the controller digitally varies the power threshold level, the current threshold level and the voltage threshold level depending on the system requirements.

20. The battery charging system of claim 19 wherein the power control loop comprises:

a current sense circuit configured to sense an amount of input current supplied by the adapter;

a voltage sense circuit configured to detect an amount of input voltage supplied by the adapter; and

a multiplier coupled to the current sense circuit and the voltage sense circuit, and configured to calculate the amount of input power by multiplying the sensed input current with the sensed input voltage.