CIRCUIT ARRANGEMENT FOR PREVENTING DEEP DISCHARGE OF A BATTERY

Abstract: The present invention relates to a printed circuit board arrangement comprising a printed circuit board (1) provided with connectors (3, 49) for connecting the printed circuit board to a battery (5, 6), an interrupt circuit (2) comprising a first (15) and a second (16) input and output (14) connected to said connectors (3, 4), and a power supply module (17, 18) comprising a first (7) and a second (10) input connected to said connectors (3, 4), means for producing operating voltage (Uout) from battery voltage, and an interrupt input (9) for interrupting the feed of the operating voltage (Uout) in response to an interrupt signal. To allow the use of the same interrupt circuit at several different battery voltages, the power supply module (17, 18) comprises a control output (8) connected to the control input (9) of the interrupt circuit (2) for feeding a control signal to the interrupt circuit (2), said control signal indicating to the interrupt circuit (2) the voltage level at which the interrupt circuit (2) feeds the interrupt signal to the power supply module (16, 17).

Description: CIRCUIT ARRANGEMENT FOR PREVENTING DEEP DISCHARGE OF A BATTERY The present invention relates to a printed circuit board arrangement comprising a circuit board provided with a first and a second connector for connecting the printed circuit board to a battery, an interrupt circuit comprising a first and a second input connected to said connectors, means for measuring battery voltage, an output for feeding a predetermined interrupt signal when the battery voltage is lower than a predetermined voltage level, a power supply module attached to the printed circuit board, said power supply module comprising a first and a second input connected to said connectors, means for producing operating voltage from the battery voltage transmitted through said inputs to be fed to the printed circuit board, and an interrupt input responsive to the output of the interrupt circuit for interrupting the operating voltage feed in response to the interrupt signal. The invention particularly relates to preventing the undervoltage operation of battery-operated telecommunications devices, but the invention can also be applied in other conditions. When a battery is discharged while in use, the operation of the battery-operated device utilizing it should be interrupted in case the battery voltage Tails below a predetermined limit; otherwise deep discharge may damage the battery. The limit value of the voltage at which the loading of the battery must be stopped depends, among other things, on the nominal voltage of said battery, in other words the limit values for stopping the loading of a 24V and a 48V battery deviate from each other, for example. A previously known printed circuit board comprises an interrupt cir- cuit for controlling the voltage obtained from the battery to a power supply module on the printed circuit board and for interrupting the operation of the power supply module when the battery voltage falls below a predetermined limit. If said known printed circuit board is to be used at several different battery voltages, the power supply module has to be changed to correspond to the battery voltage in use at each particular time. In such a case, the problem resides in the interrupt circuit on the printed circuit board, designed to interrupt the operation of the power supply module on reaching a predetermined voltage rating. If the battery voltage thus exceeds the limit for which the interrupt circuit is designed, for example, the interrupt circuit is unable to function in a desired manner, since the limit of the interrupt circuit cannot be reached until the battery has already undergone deep discharge. The object of the present invention is to solve the above problem and to provide a solution by which a given printed circuit board and the interrupt circuit thereof can be operated at several different battery voltages for preventing undervoltage battery operation with no need of manual adjustment or replacement of the interrupt circuit, for instance. This object is achieved with the printed circuit board arrangement of the invention which is characterized in that the power supply module comprises a control output connected to a control input of an interrupt circuit for feeding a predetermined control signal to the interrupt circuit, said control signal indicating to the interrupt circuit said pre- determined voltage level at which the interrupt circuit feeds the interrupt signal to the power supply module. The invention is based on the idea that providing the power supply module with a control output connected to a control input of the interrupt circuit allows the power supply module to use a control signal to indicate to the inter- rupt circuit the voltage level at which the loading of the battery should be interrupted. Thus the same interrupt circuit can be utilized at several different battery voltages, since the operation of the interrupt circuit is dependent on the control oϊJhe power supply module; In any case, the power supply module has to be chosen case by case to correspond to the nominal voltage of the battery used, whereby the necessarily required parts for feeding the proper control signal to the interrupt circuit can be integrated into the power supply modules operating at different battery voltages. Thus the most essential advantage of the printed circuit board of the invention is that the same printed circuit board and the interrupt circuit thereof can be utilized at different battery voltages with no need to adjust the interrupt circuit. The same printed circuit board and the same interrupt circuit being applicable more widely affords a smaller number of variations of requisite printed circuit boards and interrupt circuits. The preferred embodiments of the printed circuit board of the invention are shown in the attached dependent claims 2 to 3. The invention will be described in closer detail in the following by way of example using a preferred embodiment of the invention, with reference to the attached Figure 1 illustrating a first preferred embodiment of the printed circuit board arrangement of the invention. Figure 1 shows two identical printed circuit boards 1 each compris- ing identical interrupt circuits 2. A 24V nominal voltage battery 5 is connected to the upper printed circuit board by connectors 3 and 4. A 48V nominal volt- age battery 6 is similarly connected to the lower printed circuit board by connectors 3 and 4. To ensure the proper operating voltage for the printed circuit board, a power supply module corresponding to the nominal voltage of the battery connected to said printed circuit board is to be chosen in a manner known per se. Consequently, a power supply module 17 operating at a 24V primary voltage and comprising a first input 7 connected to the connector 3 and a second input 10 connected to the connector 4 is attached to the upper printed circuit board. A power supply module 18 operating at a 48V primary voltage and comprising a first input 7 connected to the connector 3 and comprising a second input 10 connected to the connector 4 is similarly attached to the lower printed circuit board. The power supply modules 17 and 18 can be of any type known per se, for instance switched-mode power supplies. The power supply modules can be attached to the printed circuit boards 1 for instance by quick-disconnect connectors. The power supply module 17 of the upper printed circuit board, for example, can thus be detached and replaced by another power supply module, provided that another batten/ of a nominal voltage deviant τrom the nominal voltage of battery 5 is connected to the upper printed circuit board. In the case shown in Figure 1 the output voltage Uout obtained from the outputs 1 and 12 of the power supply of both the upper and the lower printed circuit board is identical, for instance 3.3V. Thus the same operating voltage is provided on the upper and the lower printed circuit boards, independently of the nominal voltage of the battery connected to said printed circuit boards. To ensure the prevention of batteries 5 and 6 from deep discharging, an interrupt circuit 2 comprising a first 15 and a second 16 input connected to the connectors 3 and 4 is arranged on the printed circuit boards 1. The interrupt circuit further comprises a control input 13 connected to a control output 8 of the power supply module. As a result, the power supply module can use a control signal fed through the control input to control the interrupt circuit in such a way that the interrupt circuit is able to interrupt the operation of the power supply module at a proper voltage level dependent on the battery in use. Figure 1 shows that in the power supply module 17 attached to the upper printed circuit board, the input 7 and the control output 8 are intercon- nected whereas they are not interconnected in the power supply module 18 of the lower printed circuit board. Thus the power supply modules 17 and 18 feed a different control signal to the interrupt circuits 2, whereby the interrupt circuits 2 are able to identify which one of the power supply modules is attached to the printed circuit board in question. In the case shown in Figure 1 the interrupt circuit comprises a com- parator 19 comprising a first input connected to the inputs 15, 16 and 13 of the interrupt circuit through resistors R1 , R2 and R3. The level of the voltage signal U1 fed to the first input of the comparator 19 is thus also dependent on the control signal transmitted through the control input of the power supply, in other words on the type of the power supply (which is, in turn, dependent on the nominal voltage of the battery in use). The comparator 19 compares the voltage signal U1 fed to its first input with the reference voltage Uref fed to its second input. In case the voltage level of the voltage signal U1 is lower than the reference voltage Uref, the comparator 19 generates an interrupt signal fed by the output 14 of the interrupt circuit to the interrupt input 9 of the power supply module. The appearance of an interrupt signal interrupts the operation of the power supply module 17 or similarly the operation of the power supply module 18, whereby the loading of the battery 5 or the battery 6 stops correspondingly. It will be understood that the above description and the related fig- ures are only intended to illustrate the present invention. Many modifications and variations of the invention will be apparent to those skilled in the art without departing from the scope and spirit of the invention disclosed in the attached claims.

Claims: CLAIMS 1. A printed circuit board arrangement comprising a printed circuit board (1 ) comprising a first (3) and a second (4) connector for connecting the printed circuit board to a battery (5, 6), an interrupt circuit (2) comprising a first (15) and a second (16) input connected to said connectors (3, 4), means (R1 , R2, R3, 19) for measuring battery voltage and an output (14) for feeding a predetermined interrupt signal when the battery voltage is lower than a predetermined voltage level, and a power supply module (17, 18) attached to the printed circuit board (1 ), said power supply module comprising a first (7) and a second (10) input connected to said connectors (3, 4), means for producing operating voltage (Uout) from the battery voltage transmitted through said inputs (7, 10) to be fed to the printed circuit board (1), and an interrupt input (9) responsive to the output (14) of the interrupt circuit for interrupting the operating voltage (Uout) feed in response to the interrupt signal, c h a r a c t e r i z e d in that the power supplv module (17, 18) comprises a control output (8) connected to a control input (9) of the interrupt circuit (2) for feeding a predetermined control signai to the interrupt circuit (2), said control signal indicating to the interrupt circuit (2) said predetermined voltage level at which the interrupt circuit (2) feeds the interrupt signal to the power supply module (16, 17). 2. A printed circuit board arrangement as claimed in claim 1 , c h a r a c t e r i z e d in that the interrupt circuit (2) comprises means (R1 , R2, R3) for producing a voltage signal (U1 ) from signals received through a first, a second and a control input (15, 16, 13), the interrupt circuit (2) comprises a comparison means (19) for comparing said voltage signal (U1 ) with a predetermined reference voltage (Uref) for measuring the battery voltage, and the interrupt circuit (2) is arranged to feed said interrupt signal when the comparison means (19) indicates that the voltage level of the voltage signal (U1) is lower than the reference voltage (Uref). 3. A printed circuit board arrangement as claimed in claim 1 , c h a r a c t e r i z e d in that the voltage level of said control signal indicates to the interrupt circuit (2) said predetermined voltage level at which the interrupt circuit (2) feeds the interrupt signal to the power supply module (17, 18).

Inventors: BAARMAN GOESTA, BJOERKAS MIKAEL, MAEKINEN YRJOE, BAARMAN, GOESTA, BJOERKAS, MIKAEL, MAEKINEN, YRJOE
Applicants: BAARMAN GOESTA, BJOERKAS MIKAEL, MAEKINEN YRJOE, NOKIA TELECOMMUNICATIONS OY, BAARMAN, GOESTA, BJOERKAS, MIKAEL, MAEKINEN, YRJOE
Application year: 1998
Main classification: H02J7
IPC codes: H02H7, H02J7