FR2817677A1 - Battery charger for mobile electronic equipment, comprises first transistor regulating supply to rectifying diode and inductance and second transistor transferring load between supply and battery - Google Patents

Abstract

Continuous current (4) is supplied through a first diode (D1) to a first regulating transistor (FET2) which controls a second diode (D2) and an inductance (L) constituting the supply circuit (8) to the battery (3). The operation of the first regulating transistor is varied by a control circuit (10) which receives a signal (FB) from an inductance current detector (11). A second transistor (FET1) changes a load (7) to the battery when the supply is removed

Description

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Battery charger power supply device.

 The present invention relates to electrical supply devices for battery chargers.

une borne d'entrée adaptée pour être raccordée à une alimentation en courant continu pour charger la batterie, un premier dispositif redresseur qui relie la borne d'entrée à un premier noeud,

une borne de sortie adaptée pour alimenter électriquement un dispositif utilisateur, la borne de sortie étant reliée audit premier noeud, et un circuit de chargement de batterie reliant ledit premier noeud à la borne de connexion de batterie. More particularly, the invention relates to a battery charger electrical supply device, comprising: a battery connection terminal intended to be connected to a rechargeable battery,

an input terminal adapted to be connected to a DC power supply for charging the battery, a first rectifier device which connects the input terminal to a first node,

an output terminal adapted to electrically supply a user device, the output terminal being connected to said first node, and a battery charging circuit connecting said first node to the battery connection terminal.

 Known devices of this type include a battery supply circuit which connects the battery connection terminal to said first node to supply the output terminal from the battery in the absence of voltage at the input terminal. This battery supply circuit generally comprises a diode which passes from the battery to the output terminal, so that the battery is recharged through the battery charging circuit and not through the battery discharge circuit when a voltage is present at the input terminal.

 When these known devices operate on battery, this diode has the drawback of generating a voltage drop, hence a loss of efficiency.

 The object of the present invention is in particular to overcome this drawback.

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 To this end, according to the invention, a battery charger electrical supply device of the type in question is characterized in that the battery charging circuit comprises: a first switch and an inductor connected in series between the first node and the battery connection terminal, said first switch being close to the first node and the inductor being close to the battery connection terminal, the battery charging circuit comprising only the first switch and the inductor in series between the first node and the battery connection terminal, at least a second rectifier device connecting the ground to a second node located between the first switch and the inductor, and a control device adapted to alternately open and close the first switch, said control device having a first input connected at a point of the battery charger device located upstream of the first device f rectifier for detecting the input voltage, the control device being adapted to keep the first switch closed when the input voltage is less than a predetermined value.

 Thanks to these provisions, during battery operation, that is to say in the absence of voltage at the input terminal, the battery charging circuit behaves substantially like a short circuit between the battery and the output terminal, so that the output terminal can be powered by the battery at least by said battery charging circuit avoiding or at least minimizing voltage drops.

 In preferred embodiments of the invention, it is optionally possible to have recourse to one and / or the other of the following arrangements: the first switch is a first

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 MOS transistor; the device further comprises a second switch mounted in parallel with the battery charging circuit between the battery connection terminal and the first node, this second switch being controlled by a voltage measured upstream of the first rectifier device; the second switch is a second MOS transistor; the second switch is a PMOS transistor whose gate is connected to the input terminal, whose drain is connected to the first node and whose source is connected to the battery connection terminal; the control device is adapted to alternately open and close the second switch by modulating its duty cycle as a function of a charging current flowing through the inductor towards the battery connection terminal during the charging of the battery, so as to maintain said charging current in the vicinity of a predetermined value; the control device has a second input adapted to receive a return signal generated at least by a current measuring device, which current measuring device is suitable for measuring the charging current and for generating a current-dependent return signal loading; the current measurement device comprises an amplifier provided with at least one low-pass input filter, this amplifier being mounted in parallel with the inductor and being sensitive to a direct component of the voltage across the inductors, the return signal being a function of said DC component of the voltage across the inductor; the current measurement device comprises first and second inputs connected to the terminals of

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 the inductance respectively to the second node and to the battery connection terminal, and the amplifier is a current mirror circuit comprising: a first circuit mounted between the first input and ground, this first circuit comprising in series, a first resistor, a first diode-mounted transistor and a current source, the first transistor comprising an input (emitter or source, depending on whether it is a bipolar transistor or a field effect transistor) connected to the first resistor, an output (collector or drain) connected to the current source and a control terminal (base or gate) connected to said output of the first transistor, the current source generating in the first circuit a first derivative current, a current mirror connecting the second input to ground, this current mirror comprising a second transistor which allows a second derivative current equal to said first current d to pass to ground riveted, this second transistor comprising an input (emitter or source) connected to the second input of the current measurement device, an output (collector or drain) connected to ground and a control terminal (base or gate) connected to said terminal for controlling the first transistor, and a third transistor controlled by the output of the second transistor and comprising an input (emitter or source) connected to the input of the second transistor and an output (collector or drain) connected to ground via a second resistor, the second input of the control device being connected to the output of the third transistor; the input of the first transistor is connected to the second input of the current measurement device by a first capacitor; the control terminals of the first and second transistors are connected to the second input of the device

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- l'entrée du troisième transistor est reliée à l'entrée du deuxième transistor par une cinquième résistance ; les deuxième, troisième et quatrième résistances sont égales ; - les premier, deuxième et troisième transistors sont des transistors bipolaires PNP ; le dispositif de commande est en outre relié à un dispositif de mesure de tension mesurant une tension de charge de batterie au niveau de la borne de connexion de batterie, le dispositif de commande étant adapté pour réduire le rapport cyclique du premier interrupteur lorsque ladite tension de charge de batterie est supérieure à une valeur prédéterminée ; le dispositif de commande est relié au dispositif de mesure de tension par sa deuxième entrée, lequel dispositif de commande est adapté pour comparer la tension de charge de batterie avec une valeur prédéterminée et pour générer un signal d'erreur représentatif de l'écart entre ladite tension de charge de batterie et ladite valeur prédéterminée lorsque la tension de charge de batterie est supérieure à la valeur prédéterminée, ce signal d'erreur s'ajoutant au signal généré par le dispositif de mesure de courant pour former le signal de retour ; le dispositif d'alimentation comporte un dispositif de mesure de courant connecté aux bornes de l'inductance (ce dispositif peut servir à mesurer le courant de charge de la batterie, et/ou le courant de décharge de la batterie, lorsque ce courant de décharge current measurement by a second capacitor; the current source consists of a third resistor connecting the output of the first transistor to ground; the output of the second transistor is connected to ground by a fourth resistor;

- the input of the third transistor is connected to the input of the second transistor by a fifth resistor; the second, third and fourth resistances are equal; the first, second and third transistors are PNP bipolar transistors; the control device is further connected to a voltage measuring device measuring a battery charge voltage at the battery connection terminal, the control device being adapted to reduce the duty cycle of the first switch when said voltage battery charge is greater than a predetermined value; the control device is connected to the voltage measurement device by its second input, which control device is suitable for comparing the battery charge voltage with a predetermined value and for generating an error signal representative of the difference between said battery charge voltage and said predetermined value when the battery charge voltage is greater than the predetermined value, this error signal adding to the signal generated by the current measuring device to form the return signal; the power supply device comprises a current measurement device connected to the terminals of the inductor (this device can be used to measure the charge current of the battery, and / or the discharge current of the battery, when this discharge current

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 goes entirely through the battery charging circuit).

 Other characteristics and advantages of the invention will appear during the following description of one of its embodiments, given by way of nonlimiting example, with reference to the attached drawing.

 In the drawing, the single figure is a simplified diagram of an electric power supply device for a battery charger according to an embodiment of the invention.

et le cas échéant, un circuit d'alimentation sur batterie 9 reliant la borne de connexion de batterie 2 au noeud Nl. The battery charger electrical supply device 1 shown in the drawing comprises: a battery connection terminal 2 connected to a rechargeable battery 3 (BATT.), For example a lithium-ion battery, an input terminal 4 connected to a DC power supply 5 (AC / DC) which can be connected to the mains to recharge the battery 3, a first rectifier device such as a diode Dl which connects the input terminal 4 to a first node Nl, this diode Dl being passed from the input terminal 4 to the node NI, - an output terminal 6 connected to the first node N1 and supplying a user device 7 (LD), such as a portable microcomputer, an electronic book, an assistant personal, a portable radiotelephone, or other, a battery charging circuit 8 connecting the node Nl to the connection terminal of the battery 2,

and if necessary, a battery supply circuit 9 connecting the battery connection terminal 2 to the node N1.

The battery supply circuit 9 only comprises a first switch constituted by a P-type FET1 field effect MOS transistor, the gate of which is connected to the input terminal 4 and the

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 source is connected to the battery connection terminal 2 or to another point of the circuit upstream of the diode Dl.

 Thus, when the electrical supply 5 of the input terminal is connected to the mains to recharge the battery 3, the gate of the transistor FET1 is at a high potential, so that this transistor then constitutes an open switch: the battery 3 is therefore recharged by the battery charging circuit 8.

 Furthermore, when the power supply 5 is not connected to the mains, the voltage at the input terminal 4 is zero, so that the transistor FET1 turns on and constitutes a closed switch: the battery supply circuit 9 then short-circuits the battery charging circuit 8, and directly supplies the user device 7.

 The battery charging circuit 8, for its part, comprises a step-down device which makes it possible to regulate the direct charging current sent to the battery 3 when the power supply 5 is connected to the mains.

 This step-down device comprises: a second switch FET2, in this case a second field effect MOS transistor, which is mounted between the aforementioned NI node and an N2 node, a second rectifier device such as a freewheeling diode D2 which is mounted in derivation between the node N2 and the ground and which is passing from the ground to the node N2, an inductance L mounted between the node N2 and an intermediate node N3 between the inductance L and the battery connection terminal 2 (this diode D2 could if necessary be connected in parallel with a MOS transistor with field effect controlled in phase opposition with the transistor FET2, and in this case, said diode D2 could be constituted if necessary by the diode integrated by

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 construction in this additional MOS transistor), and possibly, a capacitor Cl mounted in shunt between the node N3 and the ground.

 The transistor FET2 is controlled by the output M of a pulse-width modulation controller circuit 10 (PWM), which can be constituted for example by a circuit of the XC6365 type sold by the company TOREX SEMICONDUCTOR LIMITED, TOKYO, JAPAN. This controller 10 is also connected to ground and has an input E connected to the input terminal 4 or to another point of the circuit upstream of the diode Dl.

 The controller circuit 10 is adapted to alternately open and close the transistor FET2 operating as a switch, by modulating the closing cyclic ratio of this transistor so as to maintain the battery charging current near a value which is determined for example by a preprogrammed in the controller circuit 10. It will be noted that the controller 10 could be replaced by a pulse frequency modulation circuit, or by any other control circuit adapted to modulate the closing cyclic ratio of the transistor FET2.

 The controller circuit 10 receives on a FB input a return signal which is a function in particular of the battery charging current.

 Advantageously, this battery charging current is measured by taking advantage of the very low internal resistance of the inductor L (for example, about 20 mQ), by measuring the DC component of the voltage across said inductor L.

 To carry out this measurement, a current measurement device 11 has two inputs El, E2 connected to the terminals of the inductor L, and an output S which generates the return signal sent to the input FB of the controller circuit 10, which signal return is a linear function of the

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 DC component of the voltage across the inductor L.

To this end, the current measuring device 11 comprises a current mirror amplifier whose inputs and output are fitted with low-pass filters.

More particularly, this amplifier comprises: a first circuit Rl, Ql, R2 comprising a resistor Rl connected to the input El of the measurement device 11, a bipolar transistor Ql of PNP type mounted as a diode, the emitter of which is connected to the resistor Rl, the base of which is connected to the collector, and the collector of which is connected to ground by a resistor R2 (if necessary, the bipolar transistor Ql could be replaced by a field effect transistor, replacing the emitter by the source, the collector by the drain and the base by the gate), a mirror circuit comprising a second bipolar transistor Q2 of PNP type, the emitter of which is connected to the second input E2 of the device II, the base of which is connected to the base of transistor Ql and whose collector is connected to ground via a resistor R3 preferably equal to R2 (transistor Q2 could be replaced by a field effect transistor, like the first transistor Ql), a capacitor C2 connected in bypass between the emitter of the transistor Ql and the second input E2 of the measuring device 11, a capacitor C3 connected in bypass between the base of the transistor Ql and the second input E2 of the measuring device 11 , and a third bipolar transistor Q3 of PNP type (also replaceable by a field effect transistor) whose emitter is connected via a resistor R4 to the emitter of transistor Q2, whose collector is connected to the mass through a

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 resistance R5 advantageously equal to the resistances R2 and R3, and the base of which is connected to the collector of the transistor Q2, a capacitor C4 being advantageously mounted in parallel with the resistor R5 and the collector of the transistor Q3 being connected directly to the output S of the device measure It to generate the aforementioned return signal.

 Furthermore, the battery connection terminal 2 is connected to the input E 'of a comparator circuit 12 (ERR.) Whose output S is floating when the voltage at terminal 2 is less than a predetermined value, by example 4, 1 V, the output being forced against a positive current (which raises the voltage FB) proportional to the difference between the voltage at terminal 2 and the predetermined value, when said voltage at terminal 2 is greater than said predetermined value. The output S'can be connected to the base of a PNP transistor Q4 whose emitter is connected to terminal 2 and whose collector is connected to input FB of controller 10. The output S and the collector of transistor Q4 generate measurement signals in current form, so that the return signal received at the input FB of the controller 10 is the sum of the measurement signal generated at the output S and the error signal generated at the output of the transistor Q4.

 A voltage limitation is thus ensured at terminal 2 when the battery is charged, since too high a voltage increases the signal received at FB by the controller 10 and therefore decreases the closing cyclic ratio of the switch FET2.

 The controller circuit 10 is moreover deactivated when the supply 5 is not connected to the mains, that is to say in the absence of voltage at the input terminal 4. In this case, the transistor FET2 is kept closed by output M of controller 10, so that current from the battery can flow into the

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 circuit 8, with a very low voltage drop. Thanks to this arrangement, the battery supply circuit 9 can possibly be eliminated.

 It will be noted that, when the transistor FET1 is deleted, it would be possible to measure the current generated by the battery, by measuring the DC component of the potential difference across the inductance L. This measurement can be carried out by a second device current measurement analogous to the device 11 described above, but suitable for a flow of current from the battery to the output terminal 6, or again by the same device 11 as described above, provided that a current is then injected into the resistor Rl by means of a controlled current source.

Furthermore, although the above description has been made in the case where the mass represents the negative potential, it would of course be possible to provide that the mass represents the positive potential, in which case the P-type transistors should be replaced by N type transistors, N type transistors to be replaced by P type transistors, NPN type transistors to be replaced by PNP type transistors and PNP type transistors by NPN type transistors.
In this case, the passing direction of the diodes should also be reversed.

Claims (19)

 1. Battery charger power supply device, comprising: a battery connection terminal (2) intended to be connected to a rechargeable battery (3),

 an input terminal (4) adapted to be connected to a DC power supply (5) for charging the battery, a first rectifier device (Dl) which connects the input terminal (4) to a first node (NI) , an output terminal (6) adapted to electrically supply a user device (7), the output terminal (6) being connected to said first node (NI), and a battery charging circuit (8) connecting said first node ( Nl) to the battery connection terminal (2), characterized in that the battery charging circuit (8) comprises: a first switch (FET2) and an inductor (L) connected in series between the first node (Nl) and the battery connection terminal (2), said first switch (FET2) being close to the first node (Nl) and the inductance (L) being close to the battery connection terminal (2), the charging circuit for battery (8) comprising only the first switch (FET2) and the inductance (L) in series between the p remier node (Nl) and the battery connection terminal (2), at least a second rectifier device (D2) connecting the ground to a second node (N2) located between the first switch (FET2) and the inductor (L) , and a control device (10) adapted to alternately open and close the first switch (FET2), said control device having a first input (E) connected at a point of the device <Desc / Clms Page number 13>  battery charger located upstream of the first rectifier device (Dl) for detecting the input voltage, the control device being adapted to keep the first switch (FET2) closed when the input voltage is less than a predetermined value.  2. Device according to claim 1, in which the first switch is a first MOS transistor (FET2).  3. Device according to claim 1 or claim 2, further comprising a second switch (FET1) mounted in parallel with the battery charging circuit (8) between the battery connection terminal (2) and the first node (Nl) , this second switch (FET1) being controlled by a voltage measured upstream of the first rectifier device (Dl).  4. Device according to claim 3, in which the second switch is a second MOS transistor (FET1).  5. Device according to claim 4, in which the second switch is a PMOS transistor (FET1) whose gate is connected to the input terminal (4), whose drain is connected to the first node (Nl) and whose source is connected to the battery connection terminal (2).  6. Device according to any one of the preceding claims, in which the control device (10) is adapted to alternately open and close the second switch (FET2) by modulating its duty cycle as a function of a charging current flowing through the inductance (L) to the battery connection terminal (2) during charging of the battery, so as to maintain said charging current in the vicinity of a predetermined value.  7. Device according to claim 6, wherein the control device (10) comprises a second input (FB) adapted to receive a return signal generated at the <Desc / Clms Page number 14>  less by a current measuring device (11), which current measuring device is suitable for measuring the charging current and for generating a return signal dependent on the charging current.  8. Device according to claim 7, in which the current measuring device (11) comprises an amplifier provided with at least one low-pass input filter (RI, C2, C3), this amplifier being mounted in parallel with the inductor (L) and being sensitive to a direct component of the voltage across the inductors, the feedback signal being a function of said direct component of the voltage across the inductors.  9. Device according to claim 8, in which the current measuring device (11) comprises first and second inputs (El, E2) connected to the terminals of the inductor (L) respectively towards the second node (N2) and towards the battery connection terminal (2), and the amplifier is a current mirror circuit comprising: a first circuit mounted between the first input (El) and the ground, this first circuit comprising in series, a first resistor (Rl ), a first transistor (Ql) mounted as a diode and a current source (R2), the first transistor comprising an input connected to the first resistor (Rl), an output connected to the current source (R2) and a terminal control connected to said output of the first transistor, the current source generating in the first circuit a first derivative current, a current mirror connecting the second input (E2) to ground, this current mirror comprising a second transistor (Q2) which let pass er to ground a second derivative current equal to said first derivative current, this second transistor comprising an input connected to the second input (E2) of the current measurement device, an output connected to ground and a control terminal <Desc / Clms Page number 15>  connected to said control terminal of the first transistor, and a third transistor (Q3) controlled by the output of the second transistor and comprising an input connected to the input of the second transistor (Q2) and an output connected to ground via a second resistor (R5), the second input (E2) of the control device being connected to the output of the third transistor (Q3).  10. Device according to claim 9, wherein the input of the first transistor (Ql) is connected to the second input (E2) of the current measurement device by a first capacitor (C2).  11. Device according to claim 9 or claim 10, in which the control terminals of the first and second transistors (Ql, Q2) are connected to the second input (E2) of the current measurement device by a second capacitor (C3) .  12. Device according to any one of claims 9 to 11, wherein the current source consists of a third resistor (R2) connecting the output of the first transistor (Ql) to ground.  13. Device according to any one of claims 9 to 12, wherein the output of the second transistor (Q2) is connected to ground by a fourth resistor (R3).  14. Device according to any one of claims 9 to 13, wherein the input of the third transistor (Q3) is connected to the input of the second transistor (Q2) by a fifth resistor (R4).  15. Device according to claims 9,12 and 13, wherein the second, third and fourth resistors (R5, R2, R3) are equal.  16. Device according to any one of claims 9 to 15, in which the first, second and third transistors (Ql, Q2, Q3) are transistors <Desc / Clms Page number 16>  bipolar PNP.  17. Device according to any one of the preceding claims, in which the control device (10) is further connected to a voltage measuring device (12) measuring a battery charge voltage at the connection terminal of battery (2), the control device being adapted to reduce the duty cycle of the first switch (FET2) when said battery charge voltage is greater than a predetermined value.  18. Device according to claim 17, in which the control device (10) is connected to the voltage measurement device (12) by its second input (FB), which control device (10) is adapted to compare the voltage of battery charge with a predetermined value and for generating an error signal representative of the difference between said battery charge voltage and said predetermined value when the battery charge voltage is greater than the predetermined value, this error signal adding to the signal generated by the current measuring device (11) to form the return signal.  19. Device according to any one of the preceding claims, comprising a current measuring device (11) connected to the terminals of the inductor (L).