Battery charger/rectifier voltage temperature compensation circuit including protection and diagnostic scheme

• US 5,869,969 A
• Filed: 11/13/1996
• Issued: 02/09/1999
• Est. Priority Date: 11/13/1996
• Status: Expired due to Fees

• Current Assignee: Astec International Limited (Emerson Electric Company)
• Original Assignee: Northern Telecom Limited (Nortel Networks Corporation)
• Inventors: Cividino, Lorenzo, Carli, Giampaolo
• Primary Examiner(s): Ballato, Josie
• Assistant Examiner(s): Solis, Jose M.
• Application Number:
  US08/747,824
• Time in Patent Office: 818 Days
• Field of Search: 320/35, 340/636, 324/431, 324/433
• US Class Current: 320/153
• CPC Class Codes: H02J 7/007192 in response to temperature
• CPC Class Codes: H02J 7/342 The other DC source being a battery actively interacting with the first one, i.e. battery to battery charging with circuits for polarity protection H02J7/0034

Abstract

A temperature compensation module for use with battery charger/rectifier units. The compensation module is used to vary the battery charger output voltage as a function of temperature. This is done by controlling the series impedance of the charger'"'"'s voltage sense leads. The impedance is controlled to produce a voltage offset in series with the sense leads. Thus, the charger'"'"'s output voltage is equal to its adjusted output voltage plus the offset voltage.

Claims

1. A temperature compensating battery charger device to control a charging float voltage of a battery connected to the battery charger device as a function of temperature, said battery charger device comprising:

a pair of sense leads connected to sense lead terminals on said battery charger device and across impedance means in series with the battery to be charged;

means to vary an impedance of said impedance means in response to a change in an ambient temperature; and

a temperature dependent device to generate a temperature dependent voltage reference proportional to the ambient temperature.

2. A battery charger device according to claim 1, wherein said means to vary the impedance includes a power MOSFET.

3. A battery charger device according to claim 2, wherein said means to vary the impedance further includes an error amplifier that controls a gate voltage of the power MOSFET to maintain a drain voltage of the power MOSFET equal to a reference voltage of the error amplifier.

4. A battery charger device according to claim 1, wherein said temperature dependent device is a thermistor.

5. A battery charger device according to claim 3, wherein the reference voltage of the error amplifier is temperature dependent.

6. A temperature compensating battery charger device to control a charging float voltage of a battery connected to the battery charger device as a function of temperature, said battery charger device comprising:

a pair of sense leads connected to sense lead terminals on said battery charger device and across a variable impedance device in series with the battery to be charged;

said variable impedance device varies its impedance in response to a change in an ambient temperature and includes a power MOSFET and an error amplifier, wherein the error amplifier controls a gate voltage of the power MOSFET to maintain a drain voltage of the power MOSFET equal to a reference voltage of the error amplifier; and

a temperature dependent device to generate the reference voltage proportional to the ambient temperature.