Selective power supply device for incandescent lamp or light-emitting diode

Abstract

The power supply device comprises a supply transistor commanded by a command signal and providing electric power to a lighting module, and a driving means configured to selectively generate, depending on an instruction signal representative of the structure of said at least one lighting module, a first command signal able to command the supply transistor into an ohmic regime, a second command signal able to command the supply transistor into a pulse width modulation regime involving an alternation of ohmic regimes and blocked regimes, and a third command signal able to command the supply transistor into a saturated regime.

Claims

1. A power supply device, comprising: a supply transistor having a control electrode that is configured to receive a command signal and conduction electrodes that are respectively coupled to a supply terminal configured to receive a supply voltage and to an output terminal configured to provide electric power to at least one lighting module having a structure corresponding to one of an incandescent lamp structure or a light-emitting diode structure, and a driving circuit configured to selectively generate, depending on an instruction signal representative of the structure of said at least one lighting module, a first command signal causing the supply transistor to operate in an ohmic regime, a second command signal causing the supply transistor to operate in a pulse width modulation regime involving an alternation of ohmic regimes and blocked regimes, and a third command signal causing the supply transistor to operate in a saturated regime.

2. The power supply device according to claim 1, wherein the driving circuit is configured, depending on the instruction signal, to first generate one of the second command signal or the third command signal over the course of a startup phase of the power supply device, and then second generate the first command signal over the course of a steady-state phase following the startup phase.

3. The power supply device according to claim 2, wherein the driving circuit is configured to generate the second command signal if the instruction signal is representative of an incandescent lamp structure of said at least one lighting module, and to generate the third command signal, if the instruction signal is representative of the light-emitting diode structure, over the course of said startup phase of the power supply device.

4. The power supply device according to claim 2, wherein the driving circuit is configured, depending on said instruction signal, to determine parameters of the startup phase, said parameters comprising a duration of the startup phase, a sampling frequency of the pulse width modulation and a magnitude of a saturation current in the saturated regime of the supply transistor.

5. The power supply device according to claim 1, wherein the driving circuit includes a first diode and a second diode having first terminals that are coupled to a source of the supply transistor and second terminals that are coupled to a switch configured to couple the gate of the supply transistor to the second terminal of the first diode in a first position, or to the second terminal of the second diode in a second position.

6. The power supply device according to claim 5, wherein the first diode operates in response to a current to generate a first voltage between the gate and the source of the supply transistor that puts the supply transistor into the ohmic regime.

7. The power supply device according to claim 5, wherein the second diode operates in response to a current to generate a second voltage between the gate and the source of the supply transistor that puts the supply transistor into the saturated regime.

8. The power supply device according to claim 5, wherein the driving circuit includes a first on/off switch and a second on/off switch that are commanded jointly into a first position, allowing a current to flow, or into a second position, imposing a zero voltage between the gate and the source of the supply transistor to put the supply transistor into a blocked state.

9. The power supply device according to claim 8, wherein the driving circuit includes an input interface configured to receive said instruction signal and to command the positions of the first on/off switch, of the second on/off switch and of the switch, depending on the instruction signal.

10. The power supply device according to claim 8, wherein the driving circuit is configured to generate the first command signal by putting the first and second on/off switches into their first position and by putting the switch into its first position.

11. The power supply device according to claim 8, wherein the driving circuit is configured to generate the second command signal by alternately putting the first and second on/off switches into their first position and into their second position in accordance with a sampling frequency of the pulse width modulation, and by putting the switch into its first position.

12. The power supply device according to claim 11, wherein the driving circuit is configured to generate the third command signal by putting the first and second on/off switches into their first position and by putting the switch into its second position.

13. The power supply device according to claim 5, wherein the driving circuit includes an internal power supply stage comprising a current generator and a switch-mode voltage generator configured to generate a voltage at least equal to the supply voltage plus a threshold voltage of the first diode.

14. The power supply device according to claim 5, wherein said first and second diodes are Zener diodes having anodes linked to the source of the supply transistor.

15. A lighting system, comprising: a power supply device, and at least one lighting module having an incandescent lamp structure or a light-emitting diode structure, wherein the at least one lighting module is coupled to an output of the power supply device, and wherein the power supply device comprises: a supply transistor having a control electrode that is configured to receive a command signal and conduction electrodes that are respectively coupled to a supply terminal configured to receive a supply voltage and to an output terminal configured to provide electric power to at least one lighting module having a structure corresponding to one of an incandescent lamp structure or a light-emitting diode structure, and a driving circuit configured to selectively generate, depending on an instruction signal representative of the structure of said at least one lighting module, a first command signal causing the supply transistor to operate in an ohmic regime, a second command signal causing the supply transistor to operate in a pulse width modulation regime involving an alternation of ohmic regimes and blocked regimes, and a third command signal causing the supply transistor to operate in a saturated regime.

16. The lighting system of claim 15, wherein the lighting system is a component of a motor vehicle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other advantages and features of the invention will become apparent on examining the detailed description of wholly non-limiting embodiments and modes of implementation, and the appended drawings in which:

(2) FIGS. 1A, 1B, 2A, and 2B, described previously, show existing systems.

(3) FIG. 3 shows a lighting system;

(4) FIG. 4 shows an exemplary embodiment of an analog generator;

(5) FIGS. 5 and 6 show two power supply modes corresponding to an incandescent lamp LMP power supply and to an LED block power supply;

(6) FIG. 7 shows an example of an application of the system within a vehicle.

DETAILED DESCRIPTION

(7) FIG. 3 shows a lighting system SYS including two lighting modules MECL having different structures, and a power supply device DALM capable of supplying power to one or the other of said lighting modules MECL.

(8) A first lighting module has a conventional incandescent lamp structure LMP, connected on the one hand to a ground terminal GND and on the other hand to a terminal PW configured to receive electric power enabling light to be generated.

(9) The second lighting module, for its part, has a light-emitting diode block structure MLED, the block including lighting management means, for example on a printed circuit board of the kind described in relation to FIG. 2B. The second lighting module thus includes, for example, a supply terminal PW, a ground terminal GND and a control bus terminal BLED.

(10) The commands delivered on the bus terminal BLED make it possible, for example, to manage the lighting mode by means, for example, of a bus interface and of a local microcontroller.

(11) A decoupling capacitor Cdec is arranged, in a conventional manner, between the supply terminal and the ground terminal GND. The decoupling capacitor Cdec generally has a capacitance of the order of 1 microfarad.

(12) The power supply device includes a coupling circuit MCPL making it possible to couple an output terminal OUT, configured to deliver electric power to the lighting modules MECL from a supply voltage Vbat and in accordance with power supply modes adapted to each structure of said lighting modules MECL.

(13) A driving circuit MPLT generates power supply command signals ALMi, commanding the coupling circuit MCPL into various power supply modes.

(14) The driving circuit MPLT is configured to receive an instruction signal INS, for example by means of an I.sup.2C or SPI bus interface BUS. The instruction signal INS makes it possible to communicate an order to on/off switch on or to on/off switch off said lighting modules. The instruction signal INS may also be representative of the structure of the lighting module MECL to be supplied with power.

(15) The interface BUS generates signals COM1-COM3, depending on the instruction signal INS, making it possible to command an analog generator that is included in the driving circuit MPLT and configured to generate the power supply command ALMi in accordance with various power supply modes.

(16) The exemplary power supply device DALM described in relation to FIG. 3 is of the high-side kind, that is to say that the coupling circuit MCPL makes it possible to link, on request, the supply voltage terminal BAT to the lighting modules MECL that are linked, on their part, to the reference voltage terminal GND.

(17) That being said, the principle behind the creation and the operation of this example applies perfectly to a low-side power supply device, that is to say the coupling circuit (MCPL) of which makes it possible to link, on request, the reference voltage terminal GND to the lighting modules MECL that are linked, on their part, to the supply voltage terminal BAT.

(18) FIG. 4 shows an exemplary embodiment in particular of such an analog generator belonging to the driving circuit MPLT of the power supply device DALM.

(19) This embodiment is suitable in particular for a coupling circuit MCPL including a supply transistor T1 connected at its drain to a supply voltage source BAT, at its source to the output terminal OUT, and at its gate to a gate node NG to which a variety of power supply command signals ALMi are applied.

(20) More precisely, it is the voltage between the gate and the source (gate-source voltage) of the supply transistor T1 that will command it into an ohmic regime, a blocked regime or a saturated regime.

(21) In this example, a first diode Z1 and a second diode Z2 are coupled on the one hand to the source of the supply transistor T1 and on the other hand to a switch SW3, commanded by a signal COM3 issued from the bus interface BUS.

(22) The switch SW3 is configured to couple the gate of the supply transistor T1 to the first diode Z1 in a first position C, and the second diode Z2 in a second position D.

(23) The diode Z1 has a threshold voltage VZ1 such that, when this threshold voltage is reached, the supply transistor T1 is put into an ohmic regime, by this threshold voltage VZ1 impacting on the gate-source voltage of the supply transistor T1.

(24) The diode Z2, for its part, has a threshold voltage VZ2 such that, when this threshold voltage is reached, the supply transistor T1 is put into a saturated regime, delivering a constant saturation current (Idssat).

(25) In this example, the diodes Z1, Z2 are Zener diodes, the respective anodes of which are coupled to the source of the supply transistor T1, and the previously introduced threshold voltages VZ1, VZ2 are the reverse threshold voltages (or Zener voltages) of said Zener diodes Z1, Z2.

(26) That being said, other configurations making it possible to set the gate-source voltage of the supply transistor may be envisaged, such as current mirrors or junction diodes.

(27) Moreover, the power supply device DALM includes an internal power supply stage GEN, able to generate an internal voltage VDD sufficient to unblock said diodes Z1, Z2, that is to say an internal voltage VDD at least equal to the supply voltage Vbat plus the highest threshold voltage VZ1 or VZ2 of said first or second diodes Z1, Z2.

(28) For example, the internal power supply stage GEN may include a switch-mode voltage generator generating said internal voltage VDD from the supply voltage Vbat.

(29) Furthermore, a current I1 generator makes it possible to regulate the current flowing in one of the forward-biased diodes Z1, Z2 to a reasonable magnitude.

(30) The driving circuit MPLT also includes a first on/off switch SW1 and a second on/off switch SW2 that are commanded by the signals COM1 and COM2 that are issued from the bus interface BUS, respectively.

(31) The signals COM1, COM2 are transmitted jointly in order to put said first and second on/off switches SW1, SW2 into a first position AA allowing a current I1 to flow in the switch SW3, or into a second position BB coupling the gate node NG to the source of the supply transistor T1, imposing a zero voltage between the gate and the source of the supply transistor T1, thus putting it into a blocked state.

(32) Thus, in this example, the driving circuit MPLT is configured to generate the first command signal ALM1 (commanding the supply transistor T1 into an ohmic regime) by putting the first and second on/off switches SW1, SW2 into their first position AA and by putting the switch SW3 into its first position C.

(33) Specifically, the voltage VDD is sufficient to forward-bias the diode Z1, and thus a set voltage VZ1 is generated between the gate and the source of the supply transistor T1 and puts it into an ohmic regime.

(34) Advantageously, the supply transistor T1 and the first diode Z1 are dimensioned so as to be optimized to supply power to a load corresponding to an incandescent lamp LMP in the stable regime (the consumption of a lamp in the stable regime generally being greater than the consumption of an LED block in the stable regime).

(35) The driving circuit MPLT is also configured to generate the second command signal ALM2 (commanding the supply transistor T1 into a pulse width modulation regime) by alternately putting the first and second on/off switches SW1, SW2 into their first position AA and into their second position BB, and by putting the switch SW3 into its first position C.

(36) As a result, the transistor T1 is put alternately into the ohmic regime (position AA) and into the blocked regime (position BB), making it possible to supply power to an incandescent lamp, for example, using a pulse width modulation PWM technique.

(37) The alternation of the joint positions AA and BB of said on/off switches SW1, SW2 is implemented in accordance with conventional PWM technique parameters that are chosen so as to be optimal, in particular for the incandescent lamp lighting module LMP, depending on the supply transistor T1. Said parameters are for example the sampling frequency f.sub.PWM of the pulse width modulation and the duration t.sub.PWM of the implementation of the pulse width modulation regime.

(38) For example, the frequency f.sub.PWM is chosen such that the duration for which the on/off switches SW1, SW2 are kept in position AA is sufficiently short that the current peak passing through the supply transistor T1 over this duration does not destroy it.

(39) The driving circuit MPLT is configured to generate the third command signal ALM3 (commanding the supply transistor into a saturated regime) by putting the first and second on/off switches SW1, SW2 into their first position AA, and by putting the switch SW3 into its second position D.

(40) The voltage VDD is thus sufficient to forward-bias the diode Z2, and thus a set voltage VZ2 is generated between the gate and the source of the supply transistor T1 and puts it into a saturated regime.

(41) Although not shown in FIG. 3, it is also possible for other second diodes having different threshold voltages to be coupled to the switch SW3, in as many other positions of the switch SW3.

(42) In this case, the positions of the switch SW3 other than the first position D make it possible to choose a gate-source voltage that puts the supply transistor T1 into a desired saturated regime. This makes it possible to be able to choose the value of the set current in the saturated regime Idssat applied on the output terminal OUT, in order for example to adapt one and the same power supply device DALM to various LED blocks having different restrictions.

(43) Moreover, in this example, reverse-biased Zener diodes Z1, Z2 make it possible to set the gate-source voltage of the supply transistor T1 to a given value. That being said, this function may also be achieved by creating, for example, an assembly of simple resistors, or an assembly of forward-biased diodes, or combinations of elementary components such as diodes, resistors, transistors, etc.

(44) FIGS. 5 and 6 show two power supply modes corresponding to an incandescent lamp LMP power supply and to an LED block power supply, respectively, implemented by the power supply device DALM.

(45) When the instruction signal INS orders a lighting module having an incandescent lamp structure to be switched on, the driving circuit MPLT generates the second command signal ALM2 over the course of a startup phase of the power supply device P1, for a duration t.sub.PWM. The second command signal ALM2 puts the supply transistor T1 into an alternation of ohmic regimes and blocked regimes, generating pulse width modulation PWM pulses on the output node OUT.

(46) The sampling frequency of these pulses f.sub.PWM and the duration t.sub.PWM of the first phase P1 may be commanded by the instruction signal INS, depending on the structure of the incandescent lamp supplied with power.

(47) For example, a table contained in a register RGTB of the power supply device DALM may make it possible to translate a command from the instruction signal INS into an analog command adapted to the architecture of the device DALM.

(48) During what is termed a steady-state phase P2 following the startup phase P1, the driving circuit MPLT then generates the first command signal ALM1 for as long as the lamp needs to be switched on.

(49) The first command signal ALM1 puts the supply transistor into an ohmic regime, allowing a current Iout to flow in the lamp. In the ohmic regime, the current Iout depends on the load R1-R2 connected to the output node OUT, in accordance with equation (eq1): Iout*(Ri+Rdson)=Vbat; where Ri is the load connected to the terminal OUT, Rdson is the resistance of the ohmic regime of the supply transistor T1, and Vbat is the supply voltage provided on the terminal BAT.

(50) The supply transistor T1 is dimensioned such that Rdson satisfies equation (eq1) for Iout=Istab, Istab being the current necessary for the lamp to operate correctly in the stable regime.

(51) When the instruction signal INS orders a lighting module having a light-emitting diode block structure to be switched on, the driving circuit MPLT generates the third command signal ALM3 over the course of a startup phase P1 of the power supply device, for a duration tsat. The third command signal ALM3 puts the supply transistor T1 into a saturated regime, limiting the current Tout on the output node OUT to a set saturation current value Idssat.

(52) With the current Iout being restricted to a maximum value Idssat, the decoupling capacitor Cdec present on the supply terminal of the LED block thus charges monotonically and linearly, as shown by the curve of the voltage Vout on the output terminal OUT during the startup phase P1.

(53) The value of this saturation current Idssat and the duration tsat of the first phase P1 may be commanded by the instruction signal INS, depending on the structure of the LED module, and in particular depending on the capacitance of the decoupling capacitor Cdec (generally of the order of 1 microfarad).

(54) For example, a table contained in a register RGTB of the power supply device DALM may make it possible to translate a command from the instruction signal INS into an analog command adapted to the architecture of the device DALM.

(55) Next, during a steady-state phase P2 following the startup phase P1, the driving circuit MPLT then generates the first command signal ALM1 for as long as the lamp needs to be switched on.

(56) The first command signal ALM1 puts the supply transistor into an ohmic regime, allowing the current necessary to supply power to the LED block to flow, this current generally being lower than the current Istab consumed by an incandescent lamp in the stable regime.

(57) FIG. 7 shows an example of an application, within a vehicle VEH, of a system SYS such as described previously in relation to FIGS. 3 to 6, furthermore including a control circuit CMD configured to generate the instruction signal INS, and a power supply circuit MALM configured to provide said supply voltage Vbat.

(58) In this kind of application, for example in a motor vehicle, the power supply circuit MALM is generally a 12 V-45 Ah battery.

(59) The control circuit CMD may be, for example, a microcontroller dedicated to the use of the vehicle passenger compartment lights and/or the vehicle headlights. More generally, the control circuit CMD is included in a smart element of the vehicle, generally referred to as an on-board computer.

(60) The control circuit CMD is thus configured to transmit an instruction signal INS to such a power supply device DALM such that it generates a supply of power that is optimized for each structure of the various lighting modules MECL of the vehicle VEH.

(61) The instruction signal is for example communicated on an I.sup.2C bus or on an SPI bus, transmitting standard commands or commands that are encoded specifically for the power supply device DALM described previously in relation to FIGS. 3 to 6.

(62) Moreover, the invention is not limited to these embodiments, but incorporates all variants thereof; for example, the structure of the LED block, other than the decoupling capacitor Cdec, has been given by way of example. The embodiment of the power supply device described in relation to FIG. 4 may also support various variants and additions that are useful to the hardware implementation.