T 0294/89 25-10-1990

1. The appeal is admissible.

2. There is no objection to the claims of the main and auxiliary requests as far as Article 123(2) EPC is concerned.

3. Novelty - Main and Auxiliary Requests

3.1. From document D1 or D2 only the features defined by the identical wording of the preambles of Claims 1 of the main and auxiliary requests and the features defined by the identical wording of the preambles of Claim 3 of the main request and Claim 2 of the auxiliary request are known; see for instance document D2, Figure 1 with regard to full-wave rectifier 22, alternating current supply 20, 21, load 30, switching means 25, control means 34, 35, 36 and Figures 2 and 3 and page 4 with regard to the claimed effects of the reference signal in the control means. The essential difference of the subject-matter claimed in all said claims with regard to the switched mode power supply known from documents D1 or D2 is the fact that the claimed switching means are located "in parallel to a capacitance across the output", i.e. in parallel to the load and "do not break the input current path", whereas the known switching means are located in series with the load and break the input current path.

3.2. From Figure 7 of document D3 there is known a switch mode power supply according to the features of the characterising parts of Claims 1 and 3 of the main request. However, document D3 is silent about control means for controlling the known switching means and where the input current is derived from.

3.3. The above facts have not been contested by the Appellant.

3.4. The remaining documents cited in the Search Report or mentioned by the Appellant do not come closer to the subject-matter of the independent claims of the main and auxiliary requests.

3.5. For these reasons, the subject-matter of Claim 1 and Claim 3 of the main request and the subject-matter of Claim 1 and Claim 2 of the auxiliary request is considered novel within the meaning of Article 54 EPC.

4. Inventive step - Main Request

4.1. It is in accord with that expressed in a host of decisions of the Boards of Appeal that the problem has to be determined objectively by comparing what is achieved by the subject-matter of a claim under consideration with that achieved by the nearest prior art.

Starting from the nearest prior art as disclosed for instance in document D2, the objective technical problem solved by the essential identical technical means defined in independent Claims 1 and 3 of the main request is, in the Board's view, to provide from a specific AC supply voltage a smoothed unidirectional voltage output at a level appropriate to the load to be supplied in such a way that either less switch-operation generated harmonics are fed back to the mains or that feedback is held at an acceptable level without the use of the filters employed in the power supply known from document D2.

The problem to prevent harmonics from getting back into a mains is well known in the art, see for instance document D1, page 4, lines 106 to 110. Thus, no contribution to inventive step is to be found in the recognition of the above-stated objective problem underlying the claimed subject-matter.

4.2. The above problem is solved by the technical means defined by the wording of the characterising parts of independent Claims 1 and 3. Both said claims describe with different words the circuit arrangement known from Figure 7 of document D3. This fact was not contested by the Appellant.

4.3. However, the Board is not able to see in the arguments presented by the Appellant - in particular those stated in points VI-a - any concrete points why the redesign of the step-down converter known for instance from Figure 1 of document D2 according to the teaching of Figure 7 of document D3 would surpass the routine capabilities of a skilled person. Due to the fact that there is nothing in the present application to indicate that any serious difficulties had in practise to be solved, and that in the cited prior art documents there is no suggestion of a problem going beyond the routine in redesigning a series type converter into a parallel-type converter, the Board takes the view that there exists no intellectual impedement of the skilled person in realising technically the teaching of document D3 in the supply of document D2. The skilled man could not have failed to realise that the parallel circuit of document D3 maintains its essential functions as a chopper circuit with as well a DC input (such as present in documents A to F cited by the Appellant) as an AC input (such as present in document D2). In particular, the Board is convinced that a skilled person will be able to verify that the control of the input current "within a predetermined range of the instantaneous magnitude of the reference signal" - such as presented in Figure 2 of document D2 - is also possible when the known control means 34, 35, 36 in Figure 1 of document D2 are reorganised to deliver their control signal to a switching means not in series but in parallel with the load without influencing the feedback properties of the circuit known from document D3.

4.4. The Board is not able to follow the Appellant's view that a skilled person will attribute the advantage mentioned in document D3, page 30, middle column, last paragraph, i.e. no retroaction back to the mains, to the input-output voltage relationship, i.e. to the fact that Figure 3 of document D3 is a step-down converter. In the Board's view the skilled person is able to recognise that said advantages are caused by the parallel position of the switching means, which he finds again in Figure 7 of document D3. At any rate, a skilled person would recognise that a parallel circuit is a better means to prevent harmonics from getting back into the mains, in particular because the HF current would have an alternative path through the known diode-capacitor series circuit, whereas the series circuit includes the inductor (29 in Figure 1 of D2). Hence, in the Board's view, a skilled person would be incited to make use of the above-mentioned advantageous properties of the parallel circuit according to Figure 7 of document D3 in the closely analogous situation of the power supply known from Figure 1 of document D2.

4.5. The argument according to point VI-c in support of inventive step, based on the fact that although the circuit of Figure 7 of document D3 had been known for a long time it had not been used by the authors of document D2, is unconvincing in the absence of any solid evidence that these circuits were generally regarded as unsatisfactory or that others had tried without success to find a solution to the problems solved by the present application.

4.6. For the above reasons, the subject-matter of independent Claims 1 and 3 of the main request is not considered to involve an inventive step within the meaning of Article 56 EPC.

5. Therefore, independent Claims 1 and 3 of the main request are not allowable under Article 52(1) EPC. Claim 2 of the main request is dependent on Claim 1 and Claims 4 to 9 of the main request are dependent on Claim 3 and, therefore, also not allowable. Hence, the Appellant's main request has to be rejected.

6. Inventive step - Auxiliary Request

6.1. For the reasons set out in point 4.1 above, the objective problem underlying Claims 1 and 2 of the auxiliary request remains the prevention of harmonics from getting back into the supply, which is regarded not to contribute to inventive step.

6.2. The feature stated in point V, which distinguishes the auxiliary Claim 1 from main Claim 1 - and which was present in the version of Claim 1 on which the refusal of the Examining Division was based - is regarded as being an alternative way of deriving the reference voltage (see document D2, page 2, lines 8-23), which way is deemed to be an obvious one for a skilled person wishing to simplify the control circuits according to Figures 11 and 14 of document D2. Moreover, said additional feature provides no surprising advantage and, above all, it does not make any contribution to solving the problem indicated in point 6.1 above. Hence, said additional feature of Claim 1 of the auxiliary request is not relevant for assessing the inventive step of the combination of features claimed in auxiliary Claim 1 (see also decision T 37/82, OJ EPO 1984, 71). hus, the reasoning of lack of inventive step as set out in detail in points 4.1 to 4.5 above applies also to auxiliary Claim 1.

6.3. The feature stated in point V, which distinguishes Claim 2 of the auxiliary request from Claim 3 of the main request, is known from document D2, page 2, lines 30 to 35 and page 4, lines 98 to 102 in conjunction with Figure 3. In particular, Figure 3 of document D2 clearly shows that in the known power supply the waveform of the input current is matched to the input voltage. The Appellant has not challenged this fact nor has he argued why it should be inventive to incorporate the known waveform-matching additionally in a power supply having the features of Claim 3 of the main request. In the Board's view, no inventive step is involved in applying said additional feature to the power supply of Claim 3 of the main request. It is basic knowledge that an undistorted current waveform increases the power factor. Hence, the effects of said additional features are foreseeable to a skilled person.

6.4. For the reasons set out in points 6.1 to 6.3 above, Claims 1 and 2 of the auxiliary request lack inventive step within the meaning of Article 56 EPC.

7. For the above reasons, independent Claims 1 and 2 of the auxiliary request are not allowable under Article 52(1) EPC. Claims 3 to 7 of the auxiliary request depend on Claims 1 and 2 and are, therefore, also not allowable. Hence, the Appellant's auxiliary request has to be rejected as well.