NI-Cad battery charge rate controller

Claim 2

A circuit (26) according to claim 1, wherein the battery is a Nickel-Cadmium battery.

Claim 3

A circuit (26) according to claim 1, wherein the means for monitoring the battery temperature includes means for converting the battery temperature into a voltage signal (T) having a level indicative of the battery temperature.

Claim 4

A circuit (26) according to claim 3, wherein the means for converting the battery temperature into the voltage signal comprises a temperature sensor (82) in good thermal contact with the battery, the temperature sensor having an output terminal (VO) which outputs the voltage signal.

Claim 5

A circuit (26) according to claim 3 or claim 4, further comprising: means (114-120) for producing a plurality of reference voltages, and wherein the transistor control terminal signal providing means includes: means (160) for comparing the voltage signal (T) from the battery temperature to voltage conversion means with a first reference voltage (VREF1), wherein the first reference voltage has a level that corresponds to a low battery temperature, for providing a signal indicative of low temperature of the battery; means (162) for comparing the voltage signal (T) from the battery temperature to voltage conversion means with a second reference voltage (VREF2), wherein the second reference voltage has a level that corresponds to a high battery temperature, for providing a signal indicative of high temperature of the battery; and, means (164,166) connected to the low battery temperature signal and the high battery temperature signal, for providing a signal indicative of allowable temperature range between the low and high battery temperatures.

Claim 6

A circuit (26) according to claim 5, wherein the low battery temperature comparing means (160) comprises a first comparator having two input terminals and an output terminal wherein the first reference voltage is connected to one of the two input terminals and the voltage signal is connected to the other of the two terminals, wherein the high battery temperature comparing means (162) comprises a second comparator having two input terminals and an output terminal wherein the second reference voltage is connected to one of the two input terminals and the voltage signal is connected to the other of the two input terminals; and wherein the allowable temperature range means (164,166) comprises a gate (166) having two input terminals and one output terminal, the output terminal of the first comparator connected to one input terminal of the gate, the output terminal of the second comparator connected to the other input terminal of the gate, and the output terminal of the gate providing the signal indicative of the allowable temperature range.

Claim 7

A circuit (26) according to claim 5 or claim 6, wherein the transistor control terminal signal providing means further includes means (168-178) for sensing an error condition and turning off the transistor (78,80) during the error condition.

Claim 8

A circuit (26) according to any of claims 1 to 7, wherein the transistor control terminal signal providing means (90) further includes means (174) for keeping the transistor turned off after the transistor has been turned on and the battery temperature has exceeded the predetermined limit until an error condition occurs or the battery is discharged.

Claim 9

A circuit (26) according to any of claims 1 to 8, wherein the means for monitoring battery charge current includes a resistor (74) connected in series in the battery charge path and means (73) for detecting the voltage across the resistor.

Claim 10

A circuit (26) according to claim 9, wherein the resistor is connected between the constant trickle current limit means (72) and ground.

Claim 11

A circuit (26) according to claim 9 or claim 10, including means (168) for comparing the voltage across the resistor with a third reference voltage (VREF3), wherein the reference voltage corresponds to a predetermined current indicative of a fast charge rate and for providing a signal indicative of fast charge.

Claim 12

A circuit (26) according to claim 11, wherein the comparing means comprises a comparator (168) with two input terminals and an output terminal, the reference voltage connected to one of the two input terminals and the resistor voltage connected to the other of the two input terminals, the output terminal providing a signal indicative of fast charge.

Claim 13

A circuit (26) according to any of claims 1 to 12, wherein the constant trickle current limit means (72) comprises a resistor (74) and a voltage regulator (73) having an input terminal (VI), an output terminal (VO) and an adjust terminal (ADS), the resistor being connected between the adjust terminal and the output terminal, and the input terminal and the adjust terminal being coupled in series in the battery charge path.

Claim 14

A circuit (26) according to claim 13, wherein the regulator input terminal (VI) is connected to the negative terminal of the battery (VBATTNEG) and the regulator adjust terminal (ADS) is connected to the means for monitoring battery charge current (76).

Claim 15

A circuit (26) according to any of claims 1 to 14, wherein the transistor (78,80) is a field effect transistor (FET) having a drain terminal as the input terminal, a source terminal as the output terminal, and a gate terminal as the control terminal.

Claim 16

A circuit (26) according to any of claims 1 to 15, comprising two field effect transistors (78,80), each having a drain terminal as the input terminal, a source terminal as the output terminal, and a gate terminal as the control terminal, such that the FETs are connected in parallel.

Claim 17

A circuit (26) according to any of claims 1 to 16, including means (200,202) for comparing the battery voltage with a fourth reference voltage (VREP4), wherein the reference voltage corresponds to a battery voltage below a predetermined allowable level, and for providing a signal indicative of low voltage of the battery.

Claim 18

A circuit (26) according to claim 17, wherein the battery voltage monitoring means further includes means (104-108) for dividing the battery voltage and wherein the comparing means (200,202) comprises a comparator (202) with two input terminals and one output terminal, the reference voltage connected to one of the two input terminals and the divided battery voltage connected to the other of the two input terminals, and the output terminal providing the low voltage signal.

Claim 20

A system according to claim 19, wherein the power providing means includes a positive terminal and a negative terminal and the single physical unit includes a positive terminal and a negative terminal, the single physical unit positive and negative terminals being removably connected to the power providing means positive and negative terminals, respectively.

Claim 21

A system according to claim 20, wherein the battery includes a positive terminal connected to the single physical unit positive terminal and a negative terminal, and wherein the charge rate controller includes a positive terminal connected to the single physical unit positive terminal, a negative terminal connected to the single physical unit negative terminal, and a charge path terminal connected to the battery negative terminal of the battery.