Auxiliary battery charge control circuit

• US 5,668,463 A
• Filed: 07/22/1994
• Issued: 09/16/1997
• Est. Priority Date: 07/22/1994
• Status: Expired due to Fees

• Current Assignee: Advanced Micro Devices, Inc.
• Original Assignee: Advanced Micro Devices, Inc.
• Inventors: Duley, Raymond S.
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): Law, Patrick B.
• Application Number:
  US08/279,294
• Time in Patent Office: 1,152 Days
• Field of Search: 320/13, 320/14, 320/15, 320/16, 320/39, 320/49, 307/66
• US Class Current: 320/103
• CPC Class Codes: H01M 10/46 Accumulators structurally combined with charging apparatus circuits for charging H02J7/00
• 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
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A circuit is provided for controlling charge (or discharge) of an auxiliary battery using an auxiliary battery charge control circuit of improved design. The auxiliary battery charge control circuit is coupled between an auxiliary battery and a main battery for regulating charge and discharge of the auxiliary battery. The auxiliary battery control circuit includes a pair of voltage dividers coupled between ground potential and the main battery, and a pair of comparators having a mutually connected output. The inputs of the pair of comparators are connected to a reference voltage and the pair of voltage dividers. The output of the comparators is connected to a switch transistor, and the switch transistor modulates a battery connected transistor coupled between the main battery and the auxiliary battery. When the main battery voltage exceeds a maximum voltage level or is less than a minimum voltage level, then the comparators turn off the switch transistor, and the switch transistor correspondingly turns off the battery connected transistor causing disconnect of the main battery from the auxiliary battery. Conversely, if the main battery voltage is between the upper and lower voltage limits, then comparator output will cause switch transistor and battery connect transistor to turn on thereby connecting main battery to the auxiliary battery. A reference voltage and resistor values within voltage divider networks are chosen according to user-defined application for setting the upper and lower voltage limits necessary for connecting or disconnecting auxiliary battery from main battery.

Claims

1. A circuit for controlling charge upon an auxiliary battery comprising:

an auxiliary battery, a main battery and an ac-to-dc converter connected in parallel with each other and in parallel to a load device;

a main battery charge control circuit connected between said main battery and said ac-to-dc converter for providing a current from said ac-to-dc converter to said main battery;

an auxiliary battery charge control circuit connected between said auxiliary battery and said main battery for providing current from said main battery to said auxiliary battery and for modulating connectivity therebetween, said auxiliary battery charge control circuit comprises;

a pair of voltage dividers coupled between a ground potential and said main battery;

a pair of comparators, each comparator having an output connected to the other comparator output and a pair of inputs connected to a reference voltage and a respective one of said pair of voltage dividers, and wherein at least one of said pair of comparators comprises a power node coupled through a low pass filter to said main battery;

a switch transistor having a switch transistor base and a switch transistor conductive path, said switch transistor base is connected to said mutually coupled comparator outputs and said switch transistor conductive path is modulated by said switch transistor base and is connected between a current limiting resistor and said ground potential; and

a battery connect transistor having a battery connect transistor base and a battery connect conductive path, said battery connect transistor base is connected through said current limiting resistor to said switch transistor conductive path, and wherein said battery connect conductive path is connected between said auxiliary battery and said main battery, whereby changes in conductivity of said switch transistor conductive path correspondingly cause changes in connectivity between said auxiliary battery and said main battery.

2. A circuit for charging and discharging an auxiliary battery and for disconnecting said auxiliary battery from a main battery, comprising:

an auxiliary battery and a main battery connected in parallel to a load device;

a series connected diode and resistor connected between said auxiliary battery and said main battery for charging said auxiliary battery from said main battery during times in which a voltage upon said main battery exceeds by a threshold amount a voltage upon said auxiliary battery;

an auxiliary battery charge control circuit connected between said main battery and said auxiliary battery for disconnecting said auxiliary battery from said main battery during times in which a voltage upon said main battery exceeds a threshold mount above the voltage upon said auxiliary battery and is less than a threshold mount above a ground potential;

said auxiliary battery charge control circuit comprises;

a first and a second voltage divider coupled in parallel between said ground potential and said main battery;

a first and a second comparator having a mutually coupled output, said first comparator includes an inverting input adapted to receive a first divided voltage from said first voltage divider and said second comparator includes a non-inverting input adapted to receive a second divided voltage from said second voltage divider, wherein said first divided voltage is less than said second divided voltage;

a switch transistor having a switch transistor base and a switch transistor conductive path, said switch transistor base is connected to said mutually coupled comparator output and said switch transistor conductive path is modulated by said switch transistor base and is connected between a current limiting resistor and said ground potential; and

a battery connect transistor having a battery connect transistor base and a battery connect conductive path, said battery connect transistor base is connected through said current limiting resistor to said switch transistor conductive path, and wherein said battery connect conductive path is connected between said auxiliary battery and said main battery, whereby changes in conductivity of said switch transistor conductive path correspondingly cause changes in connectivity between said auxiliary battery and said main battery.

3. The circuit as recited in claim 2, wherein said auxiliary battery charge control circuit achieves maximum connectivity between said auxiliary battery and said main battery during times in which said first divided voltage and said second divided voltage are less than and greater than, respectively, said reference voltage.

4. The circuit as recited in claim 2, wherein at least one of said pair of comparators comprises a power node coupled through a low pass filter to said main battery.

5. The circuit as recited in claim 2, wherein said auxiliary battery comprises five batteries connected in series, each battery is 1.2 volts nominal.

6. The circuit as recited in claim 2, wherein said main battery comprises ten batteries connected in series, each battery is 1.2 volts nominal.

7. The circuit as recited in claim 2, wherein said switch transistor comprises an npn bipolar transistor having the emitter connected to said ground potential.

8. The circuit as recited in claim 2, wherein said battery connect transistor comprises a pnp bipolar transistor having the emitter connected to said auxiliary battery and the collector connected to said main battery.