T 1449/05 26-09-2006

1. The appeal is admissible.

2. Main request - Inventive step - (Article 56 EPC)

2.1 The opposed patent relates to an arrangement for two wire dimming of fluorescent lamps using a DC-power supply. Since lamps are often located in places that are difficult to reach, such as the ceiling, the control device for dimming the lamp cannot be placed close to the lamp, but has to be located at the light switch. This means that in addition to the normal two current feed wires a third control wire is required for transmitting the dimming information to the lamp's ballast. The need for a third wire is onerous and does not allow for easy replacement of incandescent lamps by fluorescent ones in existing installations (paragraph [0004] of the opposed patent).

2.2 The patent further discloses under the heading "Background of the invention" that when dimming incandescent lamps "Direct current arrangements employ pulsed, i.e. pulse-width-modulated (PWM), direct current in order to keep the efficiency of the control device good. A mean value of the pulsed direct current is formed according to a pulse ratio, i.e. a 50% pulse ratio corresponds to about a 50% voltage value. When pulse frequency is sufficiently high (e.g. 50 Hz), the human eye perceives light as unflickering. This is due to the slowness of the eye and to the thermal mass of an incandescent filament, which makes the temperature of the incandescent filament slow to change. In control arrangements for incandescent lamps, the control may be located separately from the incandescent lamp; most typically, it is installed in connection with a light switch" (paragraph [0003] of the patent).

2.3 At oral proceedings before the board the respondent proprietor denied that the prior art cited in the said paragraph [0003] had been made available to the public before the priority date of the opposed patent. He referred to this prior art as being internal knowledge of the patent proprietor and maintained that, in fact, reference should have been made in this passage to an AC arrangement in which phase clipping control was employed for dimming the brightness of incandescent lamps and that in the conventional systems the voltage controller was not remote from the lamp.

2.4 The appellant opponent, however, stated repeatedly in the opposition procedure that the Volvo Bus Corporation, a big manufacturer of buses, had informed them that since 1999 it had used a two wire PWM controlled power supply for halogen lamps and had invited the appellant opponent to submit a design for an option to replace the halogen lamps by fluorescent lamps compatible with that power supply (page 3 of the opponent's letter dated 27 April 2004, page 4 of the letter dated 13 December 2004, page 2 of the letter dated 12 May 2005). These allegations were not contested by the patent proprietor during the opposition procedure.

2.5 In the statement of grounds of appeal, the appellant opponent argued again that it had been common practice to use PWM control devices for dimmable halogen lamps in applications where a low voltage DC power supply was available, such as in buses. This prior art was explained in the patent specification at column 1, paragraph [0003] which was further supported by the disclosure of document D7. He further referred again to the order by the Volvo Bus Corporation mentioned in the statement of grounds of opposition (pages 5 and 8 of the letter dated 19 January 2006). These allegations were not contested by the patent proprietor prior to the oral proceedings before the board.

2.6 According to the Rules of Procedure of the Boards of Appeal (RPBA), the statement of grounds of appeal and the reply of the other party shall contain a party's complete case and should inter alia specify expressly or by specific reference all the facts, arguments and evidence relied on (Article 10a(2) RPBA). Amendment to a party's case after it has filed its grounds of appeal or reply may be admitted and considered at the Board's discretion. The discretion shall be exercised in view of inter alia the complexity of the new subject-matter submitted, the current state of the proceedings and the need for procedural economy (Article 10b(1) RPBA). Amendments sought to be made after oral proceedings have been arranged shall not be admitted if they raise issues which the Board or the other party or parties cannot reasonably be expected to deal with without adjournment of the oral proceedings (Article 10b(3) RPBA).

2.7 The resilement of the respondent proprietor at a very late stage of the appeal procedure, viz nearly the end of the oral proceedings, from the acknowledgement in the opposed patent of remote PWM dimming of incandescent lamps presented in the background information of the invention deprives the appellant opponent of the possibility of searching a corresponding published document disclosing this prior art (see also T 87/01, point 5.2).

2.8 Admitting this resilement would require in all fairness the adjournment of the oral proceedings to allow the appellant opponent to search for adequate evidence that substantiates his allegations. This could have been done at an earlier stage of the proceedings if the respondent proprietor had timely contested these allegations. Making use of its discretionary power to admit amendments to a party's case (Article 10b(1) and (3) RPBA) the board does not permit the resilement of the respondent proprietor at such a late stage of the proceedings. The same applies to the allegation of the appellant opponent concerning the public nature of the technology used in the Volvo buses, an allegation that was contested by the respondent proprietor only at the oral proceedings.

2.9 The appellant opponent may well have been lulled into a feeling of false security by the respondent proprietor's failure to traverse the factual basis of the appellant's submissions. The board in exercising its discretionary power under Article 10b(1) RPBA against the respondent proprietor is, in effect, applying the generally recognized procedural principle: Qui tacet consentire videtur ubi loqui debuit (Justinian's Digest 19, 2, 13 § 11) ("He who is silent when he ought to have spoken is deemed to consent"). The board is conscious of the fact that this is not an absolute principle to be applied without exception, cf G 1/88, OJ 1989, 189 (points 2.1 to 2.4 of the reasons), but nevertheless regards it as applicable in the circumstances of this case as consonant with the legislative purpose of the RPBA.

2.10 Document D7 discloses a monolithic integrated circuit working in a pulse width modulation (PWM) mode as a controller of an external power MOS transistor for direct current (DC) applications (page 1/12). The maximum DC supply voltage (Vs) for this circuit is 26V (page 2/12). This allows it to be used eg in vehicles with a 24V DC-power supply such as public buses. In one of the disclosed application circuits the average voltage applied to an incandescent lamp can be continuously varied by the potentiometer Rp (page 8/12; Figure 4). A second application circuit discloses its use to control the brightness of vehicle headlamps using H4 type lamps (Figure 5).

2.11 The first application disclosed in document D7, ie the continuous dimming of incandescent lamps, corresponds to the acknowledgement of the prior art in paragraph [0003] of the opposed patent, although document D7 does not explicitly disclose that the controller is located remotely from the lamp. This is however an obvious option when one controller is employed for dimming several lamps, as it is the case in a bus. The board considers consequently that under the present circumstances the assessment of inventive step should start, as alleged by the appellant opponent, from the state of the art instanced by the Volvo buses in which incandescent lamps are dimmed by a remote voltage controller.

2.12 The problem addressed by the opposed patent having regard to this prior art is therefore the replacement in the known buses of the incandescent lamps by fluorescent lamps, while maintaining as far as possible the PWM-DC controller and the two wire power supply to the lamps, so that modifications to the existent equipment are kept at a minimum.

2.13 Document D11 discloses an arrangement for remote dimming of fluorescent lamps with AC power supplies. A remote voltage control device, which is not shown in Figure 1, encodes a dimming signal on the AC voltage. The AC power with the encoded signal is transmitted over the power feed wires to the filter A and rectifier B. The dimming signal is separated from the AC power by the pre-conditioner C and passed to the dimming interface I, from which a PWM-DC control signal is generated and transmitted to the ballast controller G for controlling the luminosity level of the fluorescent tubes (Figure 1; column 5, line 65 to column 10, line 14; column 17, line 15 to column 18, line 21).

The dimming interface I handles three different types of control signals received at the power line inputs 1', 2'. These signals are provided by: (i) a phase angle dimmer; (ii) a step dimmer and (iii) a coded continuous-type dimmer (column 17, lines 16 to 27 and Figures 12 to 14). Although the preferred control signal is the coded dimmer signal (iii) in which only a small perturbation is superimposed to the AC voltage to indicate the increase or decrease of the light level by a pre-selected incremental amount, the dimming interface also handles the other two control signals (i) and (ii) for backward compatibility with existing controllers.

2.14 The skilled person understands that the output of the controller of document D7 is a PWM-DC control signal and power supply at the same time. This output is thus similar to the rectified phase angle clipping control signal (i) fed into the pre-conditioner C of document D11, which also includes a power component. The electronic ballast disclosed in this document is thus in principle compatible with the voltage controller disclosed in document D7. Although the voltage levels employed in the AC and DC applications are different, the skilled person has no difficulty in adapting the circuit disclosed in document D11 to the voltage levels found in a DC environment. As argued by the appellant opponent, the pre-conditioner stage of D11 makes the electronic ballast look resistive to the power lines (column 8, lines 32 to 34) and the controller of D7 is designed for driving resistive loads as shown in the application circuits of Figures 4 and 5. When the output from the voltage controller of document D7 is fed into the pre-conditioner C of document D11, the power component is separated from the control signal and forwarded to the inverter E, while the PWM control signal is fed into the dimming interface I, as done previously with the phase angle clipping control signal (i). The dimming interface I can handle the PWM control signal without substantial modifications (column 20, lines 6 to 37, Figure 2c).

2.15 The board is not persuaded by the argument of the respondent proprietor that this adaptation would involve a major redesign of the electronic circuits of document D11 which would be beyond the skill of the normal practitioner of the art. The person skilled in the art has to have the same degree of skill when implementing the invention disclosed in the patent and when interpreting or modifying the state of the art. The opposed patent, however, does not disclose any detailed circuits suitable for implementing the claimed arrangement and discloses the invention by reference to a schematic block diagram (Figure 1). The board is therefore of the view that a skilled person able to implement and design the required electronic circuits for the claimed arrangement on the basis of the schematic block diagram of the patent would have no difficulty in redesigning the circuit of D11 to make it compatible with the voltage levels of the controller of document D7.

2.16 For the above reasons, the arrangement specified in claim 1 of the main request is not considered as involving an inventive step within the meaning of Article 56 EPC.

3. First and second auxiliary claim requests

3.1 The claims of the main, first and second auxiliary requests were filed by the respondent proprietor at the start of the oral proceedings before the board. In contrast to the amendment made to claim 1 of the main request, viz the specification of a DC supply voltage, which was a response to the novelty objection raised by the appellant opponent in his last reply before the oral proceedings and even anticipated by the appellant opponent in his last submissions, the amendments made to claim 1 of the first and second auxiliary request were made, according to the respondent proprietor, to distinguish the invention more clearly from the prior art.

3.2 Claim 1 of the first auxiliary request requires in addition to the features of the main request essentially that the voltage controller is a PWM pulse modulator. This feature however does not distinguish the voltage controller of the invention from the one disclosed in document D7.

3.3 Claim 1 of the second auxiliary request specifies in addition to the features of the first auxiliary request essentially that the arrangement is for controlling the fluorescent lamps in a vehicle having a low voltage DC power supply. However, as discussed previously with respect to the main request, the board considers that Volvo buses having a PWM-DC dimming control for incandescent lamps were part of the prior art, as maintained by the appellant opponent. Consequently, this feature also fails to distinguish the invention from the prior art.

3.4 The first and second auxiliary claim requests are therefore not admitted, being belated and not clearly allowable.