Circuit for monitoring a battery voltage

• US 20080001575A1
• Filed: 06/08/2007
• Published: 01/03/2008
• Est. Priority Date: 06/08/2006
• Status: Abandoned Application

• Current Assignee: Atmel Germany GmbH (Microchip Technology Incorporated)
• Original Assignee: Atmel Germany GmbH (Microchip Technology Incorporated)
• Inventors: Bonin, Andreas, Dathe, Lutz
• Application Number:
  US11/808,415
• Publication Number:
  US 20080001575A1
• Time in Patent Office: Days
• US Class Current: 320/136
• CPC Class Codes: G01R 15/04 Voltage dividers
• CPC Class Codes: G01R 19/16542 for batteries charge condition monitoring in G01R31/36
• CPC Class Codes: G01R 19/1659 to indicate that the value is within or outside a predetermined range of values (window) G01R19/16514, G01R19/16519, G01R19/16528 and G01R19/16533 take precedence
• CPC Class Codes: G01R 19/2509 Details concerning sampling, digitizing or waveform capturing
• CPC Class Codes: G01R 19/257 using analogue/digital converters of the type with comparison of different reference values with the value of voltage or current, e.g. using step-by-step method
• CPC Class Codes: H03M 1/202 by interpolation
• CPC Class Codes: H03M 1/46 with digital/analogue converter for supplying reference values to converter

Abstract

A method, circuit, and use for monitoring a battery voltage is provided that includes a reference voltage source having a reference voltage, a first switchable voltage divider which is connected or connectable to the battery voltage, a second switchable voltage divider which is connected to the reference voltage source, and a comparator which is connected to the first switchable voltage divider and to the second switchable voltage divider for comparison of a first divider voltage from the first switchable voltage divider to a second divider voltage from the second switchable voltage divider.

Claims

1. A circuit for monitoring a battery voltage, the circuit comprising:

a reference voltage source having a reference voltage;

a first switchable voltage divider that is connected or connectable to the battery voltage;

a second switchable voltage divider that is operatively connected to the reference voltage source; and

a comparator that is operatively connected to the first switchable voltage divider and to the second switchable voltage divider for comparing a first divider voltage from the first switchable voltage divider to a second divider voltage from the second switchable voltage divider.

2. The circuit according to claim 1, wherein the second switchable voltage divider has a multiplexer for switching the second divider voltage to the comparator.

3. The circuit according to claim 1, wherein the first switchable voltage divider has a switching transistor for modifying a voltage divider ratio.

4. The circuit according to claim 1, wherein the first switchable voltage divider and/or the second switchable voltage divider are operatively connected to a logic control system for control.

5. The circuit according to claim 4, wherein the comparator is operatively connected to the logic control system for evaluating an output signal from the comparator.

6. The circuit according to claim 5, wherein the comparator has an operational amplifier and a threshold switch, in particular a Schmitt trigger, which is operatively connected to the output of the operational amplifier, one input of the logic control system being operatively connected to an output of the threshold switch for the comparator.

7. The circuit according to claim 4, wherein the logic control system is designed for determining the battery voltage by switching the first switchable voltage divider and/or the second switchable voltage divider by a stepwise approximation or by a successive approximation.

8. The circuit according to claim 1, wherein the first voltage divider has a plurality of transistors as divider elements.

9. The circuit according to claim 8, wherein at least one transistor, which acts as a divider element, is operatively connected in such a way that the transistor may be controlled for deactivating the first voltage divider.

10. The circuit according to claim 9, further comprising a controllable transistor for deactivating the first voltage divider, the controllable transistor being connected to the logic control system for control.

11. The circuit according to claim 1, wherein the second switchable voltage divider has a plurality of integrated ohmic resistors as divider elements.

12. The circuit according to claim 1, wherein the first switchable voltage divider has a coarser resolution than the second switchable voltage divider or wherein the first switchable voltage divider has a finer resolution than the second switchable voltage divider.

13. The circuit according to claim 1, wherein the first switchable voltage divider and the second switchable voltage divider are designed in such a way that a quantization increment width is less for smaller battery voltages than for larger battery voltages.

16. The circuit according to claim 4, further comprising a controllable transistor for deactivating the first voltage divider, the controllable transistor being connected to the logic control system for control.

14. A method for monitoring a battery voltage, the method comprising switching, via a logic control system, a first voltage divider which is connected or connectable to a battery voltage;

switching, via the logic control system, a second voltage divider which is operatively connected to a reference voltage source; and

switching, via the logic control system, the first voltage divider and the second voltage divider as a function of an evaluation of an output signal from a comparator, which is operatively connected to the first switchable voltage divider and to the second switchable voltage divider for comparing a first divider voltage from the first switchable voltage divider to a second divider voltage from the second switchable voltage divider.

15. Use of a first switchable voltage divider, which is connected or connectable to the battery voltage of a second switchable voltage divider, which is operatively connected to the reference voltage source, and of a comparator which is operatively connected to the first switchable voltage divider and to the second switchable voltage divider for comparison of a first divider voltage from the first switchable voltage divider to a second divider voltage from the second switchable voltage divider for monitoring a battery voltage.