Battery charger

Claim 3

The apparatus of claim 1 further comprising: a low battery control for limiting the output current of said apparatus when the output voltage of a battery to be charged is below a predetermined level, operably connected to sense said battery output voltage and to provide a control signal to said pulse width modulator; an inoperable thermister control connected to compare an internal voltage with a portion of the output voltage of the apparatus and to turn off said pulse width modulator if said comparison exceeds a predetermined tolerance; and a low bias control connected to compare a portion of the input DC voltage to the control section with a fixed reference end to turn off said pulse width modulator if said input voltage is too low.

Claim 4

The apparatus of claim 2 wherein said transformer EMI filter section provides three phase power to said power switching section via said rectifier filter section, and a low power supply to said control section.

Claim 5

The apparatus of claim 2 wherein said power switching section comprises: a plurality of power switches for supplying power from said main power supply to a battery to be charged, operably connected therebetween; means for cooperatively driving said power switches in accordance with signals from said control section, operably connected therebetween; and means for assuring equal current across each power switch, operably connected thereto.

Claim 6

The apparatus of claim 4, wherein: said means for cooperatively driving said power switches are two transistors connected in parallel to said control circuit, each having the base thereof connected to one side of said pulse width modulator output and each having the emitter thereof connected to the other side of said pulse width modulator output, having a resistive element connected between the respective base and emitters thereof; and said power switches are each a transistor having the base thereof connected in parallel to the emitters of said power drivers, the emitters of each power switch being connected to said equal current assuring means and the collector thereof connected in parallel to the collector of each power driver, said power switches controlling the current through said battery return line.

Claim 7

The apparatus of claim 5, further comprising: a plurality of coasting diodes each having its cathode connected to one side of said rectifier and its anode connected to the collector of a number of said power drivers; a resistor-capacitor transient suppression network connected in parallel with each coasting diode; a plurality of output filter chokes each connected on one side to the anode of one of said coasting diodes and connected on the other side to a common point; a pair of common mode filter chokes each having two inputs and two outputs, the first having inputs connected to said rectifier filter section at the same point as the cathodes of said coasting diodes and to said rectifier filter section at a common point with said output filter chokes, the second common mode filter choke being connected between said first common mode filter choke and the battery output line and the battery return line, whereby each common mode filter choke is in both the battery out and battery return line.

Claim 8

The apparatus of claim 5 wherein said equal current assuring means comprises: a first plurality of inductors, each inductor thereof connected to the emitter of one of said power switches; a plurality of resistors, each resistor thereof connected in parallel with each inductor of said plurality of inductors; a plurality of diodes, each diode connected in parallel with one of said resistors and said inductors, such that the cathode thereof is connected to the emitter of a power switch; a second plurality of inductors, each inductor thereof connected serially to two inductors from said first plurality of inductors; a first plurality of serial resistor diode networks, each of said networks connected in parallel with an inductor from said second plurality of inductors; a third plurality of inductors, each inductor thereof serially connected to two inductors from said second plurality of inductors; a second plurality of serially connected resistor diode networks, each of which is connected in parallel with an inductor from said third plurality of inductors; a fourth plurality of inductors, each serially connected to two inductors from said third plurality of inductors; and a third plurality of serially connected resistor-diode networks, each connected in parallel with said fourth plurality of inductors, each of said fourth plurality of inductors also being connected to the same output of said control section as are the emitters of said power drivers and to the return side of said rectifier filter section.

Claim 9

The apparatus of claim 2 wherein said main power supply further comprises a fuse serially connected in said battery output line, and a shunt serially connected in said battery return line.

Claim 10

The apparatus of claim 2 wherein said low voltage regulator comprises: an input transformer having a center tapped secondary, a full wave rectifier, receiving input from said input transformer, having a positive and a negative output; a negative voltage regulator formed by a first capacitor connected between the negative outputs of said full wave rectifier and said center tap of said input transformer, a resistor connected to the junction of said first capacitor and said input transformer's negative output, a zener diode connected between said resistor and said input transformer center tap, and a second capacitor connected parallel to said zener diode; and a positive voltage regulator including a first transistor having its base resistively coupled to the positive output of said rectifier, a first zener diode connected between the base of said first transistor and the center tap of said input transformer, said first transistor having its emitter connected to said center tap via a resistive element; a second zener diode having its anode connected to the emitter of said first transistor, a third zener diode having its anode connected to the collector of said first transistor, a fourth zener diode having its anode serially connected to said third zener diode, a second transistor having its base resistively connected to said positive output of said rectifier and having its base connected directly to the cathode of said fourth zener diode, its emitter connected to the output of said rectifier and its collector connected to the anode of said second zener diode, thereby providing a pulsing and non-pulsing positive voltage output to said control section, said non-pulsing output filtered by a filter capacitor connected between the junction of said second zener diode with said second transistor and the center tap of said input transformer, with said pulsing voltage output filtered by the combination of a first filter inductor connected to the collector of said transistor, a second filter inductor connected on one side between said filter capacitor and said transformer, and a second filter capacitor connected between the output of said first and second filter inductors.

Claim 11

The apparatus of claim 9 wherein said pulse width modulator section comprises: means for producing pulses, having an internal input comparator and a control pin whereby an external input can control the width of said pulses; a voltage divider network connected between the center tap of said input transformer and one input of said internal input comparator; means for sensing battery voltage connected to one input of said internal comparator; a first transistor amplifier having its base connected to one pulse output of said pulse producing means, said base resistively coupled to the output of said second filter inductor of said low voltage regulator, the emitter of said transistor amplifier connected to said second filter inductor; a driver switch transformer having two primaries and a center tapped secondary, each primary connected on one side to said first filter inductor, and one of said primaries operably connected to the collector of said first amplifier transistor; a second amplifier transistor operably connected to said pulse producing means for amplifying said pulses produced thereby and transmitting them to the secondary of said driver switch transformer in the same manner as said first transistor amplifier.

Claim 12

The apparatus of claim 5 wherein said low voltage regulator comprises: a center tapped input transformer providing a positive or negative output; a negative voltage regulator having a filtered output; and a positive voltage regulator capacitively filtered for a non-pulsing output and inductively filtered for a pulsing output, said positive and negative voltage regulators operably connected to said input transformer.

Claim 13

The apparatus of claim 11 wherein said pulse width modulator section comprises: a pulse producing microcircuit having two outputs and also having control inputs for modifying the operation and output thereof; means for sensing battery overcharge operably connected to a control input of said microcircuit; pulse amplifiers operably connected to the output of said pulse producing microcircuit and to said positive voltage output of said low voltage regulator, having an output; pulse transformers operably connected through their primaries to the output of said pulse amplifiers, and having center tapped secondaries providing pulses to said switch driver transistors.

Claim 14

The apparatus of claim 12 wherein said constant current control section comprises: voltage amplification means operably connected to amplify a voltage developed across said shunt in said battery return line, having an output therefrom connected to a control input of said pulse producing microcircuit; and means for selecting a predetermined current limit operably connected to said voltage amplification means.

Claim 15

The apparatus of claim 13 wherein said current level selecting means comprises: first, second and third current limiting transistors providing a parallel input to said voltage amplification means; a jumper removably connected between the bases of said current limiting transistors and the center tap of said low voltage regulator transformer; and an end of charge transistor operably connected to alter the operation of said current limiting transistors and to receive a signal from said timer circuitry.

Claim 16

The apparatus of claim 14 wherein said constant voltage control comprises: means for comparing the battery output voltage with a predetermined reference to determine the end of charge, providing an output signal to the base of said end of charge transistor to turn on said transistor when the end of charge is reached; a first reference voltage transistor operably connected to said current limiting transistors to change the reference voltage applied thereto when the end of charge is reached; and a second reference voltage transistor operably connected to said current limiting transistors to provide a selectable reference voltage thereto in accordance with the position of said removably connected jumper.

Claim 17

The apparatus of claim 14 further comprising a low battery voltage control means for comparing the output voltage of a battery to be charged with a predetermined reference, operably connected to turn off said current limiting transistors if said output voltage is below said predetermined reference.

Claim 18

The apparatus of claim 12 further comprising: a thermister used to sense battery temperatures; a resistive element operably connected to said thermister, forming a voltage divider network therewith; means for comparing the voltage developed across said resistive element to a portion of the output voltage to determine the operability of said thermister, having an output; and a second jumper removably connected between said comparing means output and said control input of said pulse producing microcircuit.

Claim 19

The apparatus of claim 17 wherein said battery overtemperature control comprises: means for comparing a portion of the output voltage to a portion of the voltage developed across said thermister and the voltage divider network formed therewith to determine battery temperature, having an output to said control input of said pulse producing microcircuit.

Claim 20

The apparatus of claim 12 further comprising a low bias control means for comparing the DC input to said control section with a fixed reference operably connected to sense said DC input at the positive output of said control system rectifier, and having an output to the control input of said pulse producing microcircuit.

Claim 21

The apparatus of claim 2 wherein said timer section comprises: a fast clock having an output; a slow clock having an output; logic means for selecting either said fast clock or said slow clock in accordance with a signal received from said control section; a time base generator connected to the output of said fast and slow clocks, having an output, a reset input and a control input for varying the output rate of said time base generator; two up/down counters operably connected to receive input from the output of said time base generator and each having an output; second logic means operably connected to the output of said up/down counters for determining when a predetermined count has been reached in each counter; latching means receiving input from said second logic means and from said control section, each input causing said latch to output a signal to said up/down counters, changing said count from up to down, and changing the rate of said time base generator; fault latching means receiving a toggle input from said down latching means to prevent recycling batteries; a start gate receiving an input from said control section derived from the output voltage of the battery to be charged and having an output; a recycle latch operably connected to said up/down counters and having an input from said start gate; means for supplying reset signals for initiation of a battery charging cycle having outputs to said time base generator, said up/down counters, said down latch, said fault latch, and to enable said recycle latch; and output means for supplying an end of charge signal to said control section.