Battery Charger Digital Control Circuit and Method

• US 20120194141A1
• Filed: 02/23/2011
• Published: 08/02/2012
• Est. Priority Date: 01/31/2011
• Status: Active Grant

• Current Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Original Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Inventors: Shi, Justin, Soenen, Eric, Roth, Alan
• Granted Patent: US 8,441,235 B2
• Time in Patent Office: Days
• US Class Current: 320/137
• CPC Class Codes: H02J 7/0071 with a programmable schedule
• CPC Class Codes: H02M 3/157 with digital control

Abstract

A digital controlled battery charger comprises a power converter, a voltage sensor, a current senor, a mode selector and a digital controller. The voltage sensor and current sensor detect the voltage of a rechargeable battery and the current flowing through the rechargeable battery respectively. The mode selector selects a feedback signal from either the output of the voltage sensor or the output of the current sensor. The digital controller receives the selected feedback signal and generates a pulse width modulated signal for the power converter. Additionally, the digital controller is capable of dynamically adjusting its coefficients so that the control loop can maintain a stable system when the battery charger operates in different battery charging phases.

Claims

1. A digital control circuit comprising:

a mode selector being configured to receive both a current sense signal and a voltage sense signal;

an analog-to-digital converter (ADC) coupled between the mode selector and a digital controller; and

the digital controller being configured to generate a digital pulse width modulated (PWM) signal.

2. The digital control circuit of claim 1, wherein the mode selector selects an input signal and forwards the input signal to the ADC.

3. The digital control circuit of claim 1, wherein the ADC comprises a sigma delta ADC and a differential amplifier.

4. The digital control circuit of claim 1, further comprising:

a decimator coupled between the ADC and a digital filter;

the digital filter being configured to add a plurality of poles and zeros to increase a power converter'"'"'s phase margin; and

a digital PWM generator receiving a digital signal from the digital filter and converting the digital signal to the PWM signal.

5. The digital control circuit of claim 4, wherein the digital filter adds multiple poles and multiple zeros to increase the power converter'"'"'s phase margin.

6. The digital control circuit of claim 1, wherein a digital filter is configured such that:

a first group of coefficients is enabled when the current sense signal is selected; and

a second group of coefficients is enabled when the voltage sense signal is selected.

7. The digital control circuit of claim 1, wherein the ADC is configured to receive a reference voltage and a feedback signal from the mode selector.

8. A system comprising:

a power converter having an output coupled to a rechargeable battery;

a current sensor being configured to detect a current flowing through the rechargeable battery;

a voltage sensor being configured to detect a voltage across the rechargeable battery; and

a digital control circuit comprising;

a mode selector being configured to receive both a current sense signal from the current sensor and a voltage sense signal from the voltage sensor;

an analog-to-digital converter (ADC) coupled between the mode selector and a digital controller; and

the digital controller being configured to generate a digital pulse width modulated (PWM) signal.

9. The system of claim 8, further comprising:

a sense resistor connected in series with the rechargeable battery;

a current sense amplifier having two inputs across the sense resistor; and

a driver coupled between the digital controller and the power converter.

10. The system of claim 8, wherein the power converter is selected from the group consisting of a buck switching mode converter, a boost switching mode converter, a buck-boost switching mode converter, a linear regulator, a forward converter, a full bridge converter and a half bridge converter.

11. The system of claim 8, wherein the current sensor and the voltage sensor are configured such that:

a current sense signal from the current sensor and a voltage sense signal from the voltage sensor share a reference voltage.

12. The system of claim 8, wherein the digital controller is configured to receive an external signal through which a user dynamically adjusts the digital controller.

13. The system of claim 8, further comprising:

a decimator coupled between the ADC and a digital filter;

the digital filter being configured to add a plurality of poles and zeros to increase the power converter'"'"'s phase margin; and

a digital PWM generator receiving a digital signal from the digital filter and converting the digital signal to the PWM signal.

14. The system of claim 8, wherein the current sensor is selected from the group consisting of a sense resistor, a Hall effect device, a magneto resistive sensor, a current sense integrated circuit.

15. A method comprising:

detecting a current flowing through a rechargeable battery and converting the current to a current sense signal;

detecting a voltage across two terminals of the rechargeable battery and converting the voltage to a voltage sense signal;

determining a selected signal from the current sense signal and the voltage sense signal and forwarding the selected signal to a digital controller;

generating a digital pulse width modulated (PWM) signal; and

sending the PWM signal to a power converter coupled to the rechargeable battery.

16. The method of claim 15, further comprising:

comparing the selected signal with a reference voltage and converting an error between the selected signal and the reference voltage to a digital number by using an analog-to-digital converter (ADC);

compensating a digital control loop by adding a plurality of poles and zeros via a digital filter.

17. The method of claim 15, further comprising:

reducing data size by using a decimator coupled between the ADC and the digital filter.

18. The method of claim 15, further comprising sending the PWM signal to a driver to control the power converter.

19. The method of claim 15, further comprising adjusting the digital controller by using an external signal from a user or a system management unit.

20. The method of claim 15, further comprising:

receiving operating parameters from the power converter;

receiving an external signal; and

generating the PWM signal in consideration of the operating parameters and the external signal.

21. The method of claim 20, where the operating parameters are selected from the group consisting of an input voltage coupled to the power converter, an operating temperature of the power converter, a voltage across a switching element of the power converter, an input current of the power converter, an output current of the power converter, an output voltage of the power converter, a current flowing through an inductor of the power converter, an input ripple voltage of the power converter, an output ripple voltage of the power converter, an input voltage change of the power converter and an output voltage change of the power converter.

22. The method of claim 20, where the external signal includes battery parameters comprising:

an open circuit voltage;

a charging current limit; and

an equivalent load resistor.