WO1998033269A1

WO1998033269A1 - Softstart for battery controller

Info

Publication number: WO1998033269A1
Application number: PCT/US1998/001227
Authority: WO
Inventors: Steven Belyo
Original assignee: Dax Industries, Inc.
Priority date: 1997-01-23
Filing date: 1998-01-22
Publication date: 1998-07-30
Also published as: AU5928298A

Abstract

Methods and devices are provided in which power to a circuit is provided first via a 'controlled' power source (520), and, once the circuit (540) is 'charged', power is provided via a second power source (546).

Description

._ i ..

SOFTSTART FOR BATTERY CONTROLLER

Field of The Invention

Circuit power input protectors

Background of The Invention

Considerable resources have been invested over the last few years to develop battery controllers. Battery controllers can be used to provide pulsed power to DC motors as set forth in co-pending application Ser. No. 08/925,278, also assigned to DAX Industries, Inc., as well as other applications such as portable hand tools such as electric drills. A particularly important application of such battery controllers is for providing electric power to motors of electric vehicles.

A significant problem which may arise in such use is that any rapid application of DC power to initially energize the controller may result in an excessive current draw across the controller, especially through the main contactor (power switch) which connects a power source such as a traction battery pack to the battery controller. In the past, this problem was addressed by placing a pre-charging bypass resistor (generally about 200- 250 Ω) across the contacts of the main contactor. Placing the bypass resistor across the contacts of the main contactor allowed a "trickle" current to enter the controller even when the main contactor was "open". Because the controller is kept in a "charged" state, such solutions are effective in eliminating potentially harmful surge currents within the controller, but they accomplish this result by maintaining a charge across capacitors within the controller. This creates a safety hazard because the controller is never fully powered off.

Thus, there is still a need to prevent excessive current draw across the controller during initial startup, while avoiding the creation of additional safety problems.

Summary of the Invention

Methods and devices are provided in which power to a circuit is provided first via a

"controlled" power source, and, once the circuit is "charged", power is provided via a second power source. Various objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the invention, along with the accompanying drawings in which like numerals represent like components.

Brief Description of the Drawings

Fig. 1 is a schematic view of a first controller embodying the invention.

Fig. 2 is a schematic view of a second controller embodying the invention. Fig. 3 is a schematic view of a third controller embodying the invention. Fig. 4 is a schematic view of a fourth controller embodying the invention.

Detailed Description

Referring to figure 1, circuit 10 comprises power input terminals 30A and 30B, and circuit state output terminal 40. Also shown is a circuit protector 50 having power input terminal 20A, 20B, 60A and 60B, power output terminal 70A and 70B, and circuit state input terminal 80. Circuit protector 50 is electrically coupled to circuit state output terminal 40, and to power input terminal 30B. Applying power across terminals 20A and 20B results in the circuit becoming "charged" (i.e. capacitors at least 25%, 50%, 75%, 90%, or greater than 90% charged, magnetic fields established, etc.). Once the circuit is charged, a signal indicating that the circuit is charged is transmitted to circuit protector 50, which then allows power to pass through it such that power applied to terminals 60A and 60B can enter the controller.

The purpose for the controller having two sets of power input terminals is to allow initial power to the circuit to be provided by a "controlled" (i.e. limited and or tightly controlled or filtered voltage and or current outputs) power source, coupled to the first set of power input terminals, to "pre-charge" or "soft start" the controller. Once the controller is "charged", the risk of damage to the controller decreases and additional power can be provided via the second set of power input terminals. The purpose of protector circuit 50 is to prevent power from entering the controller via the second set of power input terminals until after the controller is "charged".

Referring to figure 2, power input terminals 20A and 20B of figures 1 have been eliminated and circuit protector 50 first provides "controlled" power to circuit input terminals 30A and 30B and later provides additional power. In essence, circuit protector 50 modifies power entering via terminals 60 A and 60B so that circuit 10 receives "controlled" power until it is "charged", and then received additional or less "controlled" power.

Referring to figure 3, when compared to figure 2, it can be seen that circuit state input and output terminals 40 and 80 have been eliminated. In this configuration, circuit protector 50 determines when circuit 10 is charged by monitoring the characteristics which can be measured via power input terminals 30A and 30B such as the voltage across the terminals, the current flowing in and out of circuit 10, capacitance, inductance, etc.

The actual makeup of circuit 10 is unimportant so long as it has means through which power can be provided to the circuit and means for signaling circuit protector 50 when the circuit is "charged". Obviously, although circuit 10 and circuit protector 50 are shown as separate pieces, the functionality of each could be combined to form a single, self protecting "circuit".

The actual makeup of circuit protector 50 is also unimportant so long as it only allows "controlled" power to enter the circuit until after the circuit is charged.

Although figures 1 and 2 seem to indicate an electrical connection is used to transmit a signal from circuit 10 to circuit protector 50, alternative transmission mechanisms such as the use of radio, light, and or sound transmitters is also contemplated.

Any individual terminal could be replaced by multiple terminals. Pairs of terminals might be replaced by a single terminal if a common ground exists.

Referring to the preferred embodiment of figure 4, a battery pack 420 is electrically connected to a controller 430 via a prestart battery controller circuit 440. The battery pack 420 is contemplated to be any type of battery pack, including especially lead acid batteries, and including especially a 144 Volt battery pack. The controller 430 is intended here to represent a generic controller having a storage capacitor bank 432 having leads across main supply rails (30A and 30B), and is therefore not limited to any particular number or arrangement of capacitors, transistors and so forth. Circuit 440 includes a voltage triggered switch 442 which activates the main contactor coil, armature or solenoid 444 through an auxiliary battery supply 446. Although the figure appears to indicate specific components, replacements components or groups of components known to have similar characteristics and or functionality are also contemplated. Thus, specific embodiments and applications of circuit power input protectors have been disclosed. It should be apparent, however, to those skilled in the art that many more modifications besides those already described are possible without departing from the inventive concepts herein. The inventive subject matter, therefore, is not to be restricted except in the spirit of the appended claims.

Claims

CLAIMSWhat is claimed is:

1. A method of protecting an electrical circuit comprising: providing the circuit with at least one transient state which the circuit enters after power is applied to the circuit, and which the circuit leaves at some later time;

applying initial power to the circuit, said power being sufficient to cause the circuit to

enter the transient state and to later leave the transient state, said power being limited to decrease

the likelihood of damage to the circuit while the circuit is in the transient state; detecting when the circuit leaves the transient state;

applying additional power to the circuit after the circuit has left the transient state.

2. The method of claim 1 wherein the circuit has at least one capacitor and applying power to

the circuit results in a voltage being applied to the capacitor, and wherein the circuit is in the transient state from the time of initial application of power until the voltage across the

capacitor terminals is equal to or greater than 90% of the voltage being applied to the

capacitor.

3. The method of claim 1 further comprising supplying at least two power sources wherein at

least some of the initial power is provided from at least one source which is not used to provide the additional power.

4. The method of claim 1 further comprising supplying at least two power sources wherein at

least some of the additional power is provided from at least one source which is not used to provide the initial power.

5. A motor controller comprising a first power input path, a second power input path, a detector circuit, and two points, the first power input path further comprising a switch which prevents power from entering the controller through the first path while the switch is open, said switch being coupled to the detector circuit in a manner which allows the detector circuit to open and close the switch, the detector circuit being coupled to the two points and the two

points being coupled to the second power input path such that power entering the controller

through the second input path results in a voltage differential between the two points and, when the voltage differential exceeds a threshold value, also results in the detector circuit closing the switch and allowing power to enter the controller through the first power input

path.

6. The controller of claim 5 further comprising a capacitor wherein the voltage differential

threshold value is met or exceeded after the capacitor has been charged to at least x% of its

capacity wherein x is 75%.

7. The controller of claim 6 wherein x is 50%.

8. The controller of claim 6 wherein x is 90%.