FR2750228A1 - Supply device for feeding external data reader - Google Patents

Abstract

The device (20) supplies an external reader connected to a computer via a PCMCIA port (8) or a parallel port. The device has access to a first voltage supply (Vcc) inside the computer and uses a battery or capacitor (1) to store energy from the first voltage supply. A current limiter (2) is positioned between the voltage source and the energy storage device and limits the current flow from the voltage source. The voltage output from the energy storage device is boosted to a first voltage level (5V) required for feeding logic components (6L,7L) of the external reader (L1). A second booster (320) raising the output voltage of the energy storage device to a second voltage level (12V) which is required to feed the drive system (7M) of the external reader.

Description

"Device and method for powering an external reader
information carrier connected to a computer, and
external drive including this device
DESCRIPTION
The present invention relates to a device for supplying an external information carrier reader connected to a computer, in particular a microcomputer, from a port, in particular a PCMCIA port or a parallel port. It relates more particularly to portable computers. The invention also relates to a power supply method implemented in this device, as well as an external reader including this device.

A great difficulty in adapting a hard disk drive and / or CD-ROM to the PCMCIA port of a laptop computer lies in the low power available on the power pins of the ports.
PCMCIA. To supply these peripherals without using an external power supply, two voltages are available: a general supply voltage Vcc equal to 5 V or 3.3 V, and a secondary supply voltage Vpp equal to 12 V. In addition, in the case of an external reader connected to a parallel port of a computer, it is necessary in any case to provide another access to the first source of supply voltage (Vcc), no supply voltage being generally available on this type of port.

 On the general 5 V supply, it is possible in practice to draw a maximum current of the order of 500 mA, but this current is often limited by an internal protective resistance of the order of 1 Q. I1 follows that, under this called current, the output voltage is reduced below the threshold of the TTL logic: 4.75 V, which does not allow direct supply of logic circuits with a power greater than 1 W.

 The maximum current authorized on the secondary 12 V supply is most of the time of the order of 60 mA, with an internal resistance typically of 2 Q.

 In addition, these power supplies are very often protected by an internal circuit breaker which has the effect that either the power supplies of the PCMCIA port are cut, or the computer resets as soon as the current called exceeds the maximum allowable value.

 However, with the increase in the performance of external readers, and in particular of the speeds of rotation of the read heads, the peak current requirements are more and more high and the current power supply devices are not able to satisfy them. .

 The object of the invention is to remedy these drawbacks by proposing an external reader supply device which does not require an additional supply connection to the mains, while being able to deliver a peak current at least greater than 1 A.

It is a device for supplying an external reader with a data carrier, in particular a reader for
CD-ROM and / or hard disk, connected to a computer via a first port, in particular a PCMCIA port or a parallel port, this device comprising access to a first supply voltage source (Vcc).

According to the invention, it comprises:
a buffer battery charged by the first power source and delivering a predetermined output voltage substantially lower than the nominal voltage delivered by the first power source,
- current limiting means inserted between the first supply voltage source and the buffer battery, to limit the current supplied by the first supply source, and
first means for raising the output voltage of the buffer battery to a first voltage level required for supplying the logic components of the external reader.

Thus, the first power source, in this case the general power source Vcc permanently recharges the buffer battery via a current limiter. In the case of an external drive connected to a PCMCIA port, this current limitation prevents the internal circuit breakers of the power supply from the PCMCIA port from being stressed. The battery voltage is then raised to 5 V by a switching circuit of a very conventional type today, in so-called "voltage step-up" mounting. The device according to the invention in practice allows a peak current of up to 2 A at output while calling up a regular current on the first source of supply voltage, which cannot be envisaged with a direct supply of the reader. external from the port
PCMCIA.

 In the case of an external reader connected to a parallel port of a computer, thanks to the supply device according to the invention, it becomes possible to use the main supply voltage (Vcc) accessible on the keyboard port / computer mouse.

 During periods of low activity or inactivity of the external drive, the buffer battery stores energy which can be restored during periods of intense activity, in particular when the magnetic heads of the hard drive or the laser head of the CD-ROMs are moving.

 In one embodiment of a power supply device according to the invention, the latter further comprises means for lowering the voltage delivered by the second supply voltage source to a level substantially equal to that required for the reader. external, these voltage lowering means providing a complementary source of energy to power the logic components of the external reader.

 Thus, in addition to the energy provided by the 5V supply, a switching voltage reducer is used to lower the voltage from 12 V (second power source) to 5 V with a yield of the same order, with a classic assembly commonly called "Voltage step-down". In this embodiment, it is possible to draw a much higher power and to power a CD-ROM drive of higher rotational speed, paired or not with a hard disk drive, all operating at 5 V.

 In an advantageous version of the invention, the power supply device can further comprise second means for raising the output voltage of the buffer battery to a second voltage level required for powering the drive means of the external reader. . This version makes it possible to satisfactorily meet the ever higher power requirements observed with the increase in drive speeds of readers.

Furthermore, an advantageous option consists in providing the supply device according to the invention with a device for rapidly charging the buffer battery, comprising means for detecting a battery output voltage level below a predetermined voltage threshold. , means for interrupting any connection between the buffer battery and the voltage boosting means in the event of detection of too low battery voltage. Thus, when the voltage drops below a predetermined threshold, the buffer battery is automatically isolated from the step-up stage, which has the effect of eliminating the charge downstream and of forcing the rapid charge of the buffer battery to from the port
PCMCIA.

According to another aspect of the invention, there is provided a method for supplying an external information carrier reader, in particular a CD-ROM and / or hard disk drive, connected to a computer via a port.
PCMCIA, this PCMCIA port comprising an access to a first supply voltage source (Vcc) and an access to a second supply voltage source (Vpp), implemented in the supply device according to any one of the preceding claims. According to the invention, this method comprises:
a permanent charge of a buffer battery from the first power source, this buffer battery delivering a predetermined output voltage substantially lower than the nominal voltage delivered by the first power source,
- a limitation of the current delivered by the first power source,
an increase in the voltage delivered by the battery to a first voltage level required for supplying the logic components of the external reader.

Other features and advantages of the invention will appear in the description below. In the appended drawings given by way of nonlimiting examples:
- Figure 1 is a block diagram of a first embodiment of a supply device according to the invention;
- Figure 2 is a block diagram of a second embodiment of a supply device according to the invention, implementing two voltage boosting circuits;
- Figure 3 illustrates a practical embodiment of a supply device according to the invention; and
- Figure 3 is a block diagram of a third embodiment of a power supply device according to the invention, applied to an external reader connected to a parallel port of a computer.

 We will now describe, with reference to the above figures, two embodiments of a power supply device according to the invention, applied to an external reader connected to a PCMCIA port of a computer, at the same time as the method of power supply implemented in this device.

First, consider an external drive
Li according to the invention, - hard disk and / or CD player
ROM-, connected to a laptop (not shown) via a PCMCIA port 8 which normally provides access to a first source of supply voltage called main
Vcc (5 V) and a second source of supply voltage, called secondary or programming, Vpp (12 V). The external reader L1 includes a supply device 10 according to the invention comprising a current limiting circuit 2 provided to avoid any risk of stressing the internal circuit breakers supplying the PCMCIA port, a buffer battery 1 consisting for example of three Ni cells -Cd (Nickel-Cadmium) delivering a loaded voltage between 3.8 V and 3.9 V, a voltage booster (or booster) circuit 3 designed to deliver an output voltage of 5 V from the voltage of the buffer battery 1, and an automatic rapid charge device 5 acting as a circuit breaker and allowing disconnection between the buffer battery 1 and the voltage booster circuit 3. The output voltage of the voltage booster circuit 3, which is preferably produced in the form of a switching circuit in conventional mounting commonly called "voltage step up", is provided to supply the logic components 6L of the reading unit 6 of the external reader re 10.

The drive or motorization components 6M can generally be supplied directly from the buffer battery, since they are not subject to the constraints required by the TTL logic. The power supply device 10 further preferably comprises a step-down circuit 4 receiving as input the secondary voltage Vpp (12 V) and delivering a low voltage of 5 V which can be directly used for powering components of the external reader and / or applied to the buffer battery 1 as a source of additional charge via a diode and a limiting resistor 9. It should be noted that the various circuits making up the supply device according to the invention are in practice supplied from the secondary supply voltage Vpp.

In a second embodiment illustrated by FIG. 2 in which the elements common to FIG. 1 have common references, the external reader L2 comprises a supply device 20 according to the invention comprising, downstream of the automatic charging device 5 , a first voltage booster circuit 310 provided for supplying the logic components 7L of the reading unit 7 with a voltage of 5 V, and a second voltage booster circuit 320 provided for supplying a voltage of 12
V the drive or motorization components 7M of said read unit 7. This type of power supply device is particularly suitable for powering CD-ROM drives at high speed (6X and more).

 We will now describe a practical embodiment of the circuits making up a power supply device according to the invention, with reference to FIG. 3. Here, we use very conventional techniques and components in the field of electronics.

 The current limiting circuit 2 can thus include a shunt resistor 22 in series in the supply line, an amplifier 23, a comparator 24 mounted to detect an overshoot of the line current beyond a current setpoint, and a switch 21, for example an FET transistor, controlled by comparator 24 and designed to interrupt the supply circuit in the event of the current being exceeded being exceeded. In this exemplary embodiment, a Zener diode 25 is provided to provide a supply voltage reference used as a reference for the comparison.

 The buffer battery 1, produced from several Cd-Ni cells (in practice three to deliver 3.8 V), is provided with a diode 11 arranged upstream to avoid any return of current in the case where the charging voltage of the buffer battery 1 would become greater than the output voltage of the limiter 2.

 The automatic rapid charge device 5 comprises a comparator circuit 53 for comparing the output voltage of the buffer battery 1 with a voltage threshold adjustable by a potentiometer 54 connected to the supply voltage reference, and an amplifier 52 for controlling d 'a switch 55, made for example in the form of an FET transistor. This control amplifier 52 is connected to a fast charge control switch 51 which can be actuated manually. This automatic fast charging device 5 is implemented each time the battery voltage becomes too low. The power supply device according to the invention then devotes itself exclusively to charging the buffer battery 1 and no longer supplies the components of the external reader during this time.

The voltage booster (or booster) circuit 3 is designed around a specialized integrated circuit 30, for example reference Max 770, performing the "voltage step up" function and with which a small inductance 32 of the order is normally associated 40 uH, a transistor
FET 33 with very low internal resistance, a diode 33 and a polarized capacitor 34.

 The step-down circuit 4 is designed around a specialized integrated circuit 40, for example of reference Max 738, supplied from the secondary supply voltage of 12 V and with which are associated, according to a conventional diagram, a diode 43 , a small inductor 42 and a polarized capacitor 46. The output voltage (5 V) of the step-down circuit 4 is applied on the one hand, to the buffer battery 1 via a diode and a limiting resistor 9, and on the other hand , through a diode 45, for supplying components to the external drive (CD-ROM and / or hard disk).

We will now describe the supply method thus implemented, as well as the various energy transfers carried out in a supply device according to the invention. Initially, in the absence of current drawn by the high consumption components 6M, 7M of the external reader L1, L2 (for example when the read heads are at rest), the buffer battery 1 is permanently charged, via the unsolicited limiter circuit 2, from the main power source
Vcc and possibly as an additional contribution, from the secondary power source Vpp.

The electrical energy consumed by the logic components 6L, 7L remains modest and is supplied directly by the power sources after conversion in the voltage booster circuit. In addition, during periods of low activity or inactivity of the external reader, the buffer battery stores energy which can be restored during periods of intense activity.

 When the high-consumption components are activated (starting of the read heads), a high peak current (up to 2 A) is called and the necessary electric energy is then provided essentially by the buffer battery 1 which gradually discharges throughout the current draw. If it turns out that the battery voltage becomes too low, a "shut down" mechanism is initiated with the activation of the automatic rapid charge device 5. The transistor 55 is then controlled in blocked mode, the buffer battery is is isolated from the voltage booster circuit 3 and recharges quickly since it no longer has to deliver the current called downstream. When a sufficient charge voltage is again reached, the transistor 55 is controlled in on mode and the buffer battery 1 is again connected to the voltage booster circuit 3. It is also possible to provide an alert system, in particular d 'audible alert, to indicate to the user of the external reader that the external reader will no longer be supplied due to the weakening of the buffer battery 1.

 With the use of high frequency switching circuits (several hundred kHz), it is possible to achieve efficiencies close to 90% for the voltage raising and lowering circuits. The power supply device according to the invention allows a peak current of up to 2 A at output while drawing a regular current on the PCMCIA port.

 A power supply device according to the invention can also be included in an external reader intended to be connected to a parallel port of a computer, as illustrated in FIG. 4. An external reader L3 comprises a reading unit 60 comprising drives and logic circuits and connected to an IDE connector 63, and a power supply device 61 according to the invention connected as an input to a power connector 62. The computer 70, to which the external reader L3 is connected , comprises a parallel port 65 to which is connected an IDE controller 64 of plug structure which can optionally receive a cable 72 for connection to a printer 71, and a keyboard / mouse port 66, intended in particular for the connection of a mouse, on which connecting a mini-DIN type plug 67 of a connecting cable 69 to the power connector 62 of the external reader L3. The IDE 64 controller is connected to the IDE 63 connector of the external reader L3. The L3 external reader thus has a power source via the keyboard / mouse port.

 Of course, the invention is not limited to the examples which have just been described and numerous modifications can be made to these examples without departing from the scope of the invention. Thus, the means for raising and lowering tension can be produced according to many other techniques than those described here. The same is true for the buffer battery, the number of cells and the technology of which may depend on the respective voltage levels of the general power supply of the computer and of the logic and drive components of the external drive.

Claims (17)

1. Device (10, 20, 61) for supplying an external information carrier reader (L1, L2, L3), in particular a CD-ROM and / or hard disk drive, connected to a computer (70) via a first port, in particular a port PCMCIA (8) or a parallel port (65), this device comprising access to a first supply voltage source (Vcc) within the computer, characterized in that it comprises:  a buffer battery (1) charged by the first supply voltage source (Vcc) and delivering a predetermined output voltage substantially lower than the nominal voltage delivered by the first supply voltage source (Vcc),  - current limiting means (2) inserted between the first supply voltage source (Vcc) and the buffer battery (1), to limit the current supplied by the first supply voltage source (Vcc), and  - first means (3, 310) for raising the output voltage of the buffer battery (1) to a first voltage level (5 V) required in particular for supplying the logic components (6L, 7L) of the external reader ( L1, L2). 2. Supply device (20) according to claim 1, characterized in that it further comprises second means (320) for raising the output voltage of the buffer battery (1) to a second voltage level (12 V) required in particular for supplying drive means (7M) to the external reader (L2). 3. Feeding device (10, 20, 61) according to one of claims 1 or 2, characterized in that it further comprises an automatic rapid charging device (5) of the buffer battery (1), comprising means (52-54) for detecting a battery output voltage level below a predetermined voltage threshold, means (55) for interrupting any connection between the buffer battery (1) and the voltage boosting means (3) if the battery voltage is detected too low. 4. Supply device (10, 20, 61) according to claim 3, characterized in that the automatic rapid charge device (5) further comprises means (51) for forcibly controlling the switch means (55). 5. Power supply device (10, 20) according to one of the preceding claims, for supplying an external reader connected to a computer via a PCMCIA port (8), this PCMCIA port comprising access to the first voltage source of supply (Vcc) and access to a second supply voltage source (Vpp). 6. Supply device (10, 20) according to claim 5, characterized in that it further comprises means (4) for lowering the voltage delivered by the second supply voltage source (Vpp) to a level substantially equal to that required for powering the external drive (L1, L2). 7. Supply device (10, 20) according to claim 6, characterized in that the voltage lowering means (4) are further connected to the buffer battery (1) and provide a complementary source of charging energy for this buffer battery (1). 8. Power supply device (61) according to one of claims 1 to 4, for supplying an external reader (L3) connected to a parallel port (65) of a computer (70) via first connection means (68 , 63), characterized in that it further comprises second connection means (67, 69, 62) for accessing the first supply voltage source (Vcc) via a second port (66) of this computer ( 70), in particular a keyboard / mouse port. 9. Method for supplying an external information medium reader (L1, L2, L3), in particular a CD player ROM and / or hard drive, connected to a computer (70) via a first port, in particular a PCMCIA port (8) or a parallel port (65) comprising access to a first supply voltage source (Vcc) at the within this computer (70), this method being implemented in the supply device (10, 20, 61) according to any one of the preceding claims, characterized in that it comprises:  - A permanent charge of a buffer battery (1) from the first supply voltage source (Vcc), this buffer battery (1) delivering a predetermined output voltage substantially lower than the nominal voltage delivered by the first source supply voltage (Vcc),  a limitation of the current supplied by the first power source (Vcc), and  an increase in the voltage delivered by the buffer battery (1) to a first voltage level required for supplying the logic components of the external reader (L1, L2). 10. The method of claim 9, characterized in that it further comprises an increase in the voltage delivered by the first supply voltage source (Vcc) to a second voltage level (12 V) required for the supply drive means (7M) of the external reader (L2). 11. Method according to any one of claims 9 or 10, characterized in that it comprises automatic sequences of rapid charge of the buffer battery (1) comprising:  a detection of a battery voltage level below a predetermined voltage threshold, and  - in the event of detection, an interruption of any connection between the buffer battery (1) and the voltage boosting means (3, 310, 320). 12. The method of claim 11, characterized in that it further comprises controlled sequences of rapid charging of the buffer battery (1) comprising an interruption of any connection between the buffer battery (1) and the voltage boosting means ( 3, 310, 320). 13. Power supply method according to one of claims 9 to 12, applied to the supply of an external reader (L3) connected to a PCMCIA port (8) of a computer, this PCMCIA port (8) providing a access to the first supply voltage source (Vcc) and access to a second supply voltage source (Vpp). 14. The method of claim 13, characterized in that it further comprises a lowering of the voltage delivered by the second supply voltage source (Vpp), to the level required for the supply of the external reader (L1, L2 ). 15. The method of claim 14, characterized in that it further comprises an additional supply of energy for charging the buffer battery (1), from the lowered voltage. 16. Method according to one of claims 9 to 12, for supplying an external reader (L3) connected to a parallel port (65) of a computer (70), characterized in that the first voltage source is accessed power supply (Vcc) via a second port (66) of the computer (70), in particular a keyboard / mouse port. 17. External information carrier reader (L1, L2, L3), in particular of a hard disk and / or CD-ROM, including a supply device (10, 20, 61)) according to any one of claims 1 to 8.