SUPPLEMENTAL INDENTURE

THIS SUPPLEMENTAL INDENTURE dated as of May 8, 2009 (the “ Supplemental Indenture ”) among POWER-ONE, INC., a Delaware corporation (the “ Company ”), and THE BANK OF NEW YORK MELLON TRUST COMPANY, N.A., a national banking association, as Trustee (the “ Trustee ”) under the Indenture dated as of June 17, 2008 (the “ Indenture ”) between the Company and the Trustee, pursuant to which the Company issued its 8% Senior Secured Convertible Notes due 2013 (the “ Notes ”).

WHEREAS, the Company issued Notes in an aggregate principal amount of $80,000,000 under the Indenture, of which $63,000,000 are outstanding.

WHEREAS, Section 12.01 of the Indenture provides that the Indenture or the Notes may be amended with the consent of Holders of at least a majority of the principal amount of the Notes then outstanding (including consents obtained in connection with a purchase of the Notes).

WHEREAS, the Company has obtained the written consent to the proposed amendments to the Indenture from the Holders of at least a majority in aggregate outstanding principal amount of the Notes.

NOW, THEREFORE, for and in consideration of the foregoing premises, it is mutually covenanted and agreed, for the equal and proportionate benefit of all Holders of the Notes, as follows:

ARTICLE ONE

                Section 1.1.            Amendments to the Indenture .

(a)            The following sections of the Indenture are deleted in their entirety and, in the case of each such section, replaced with the phrase “[Intentionally Omitted.]”, and any and all references to such sections, whether direct or indirect, in any term, condition, limitation or other provision in the Indenture, are deleted, and such sections and references shall be of no further force or effect:

All corresponding provisions of the Notes are deleted in their entirety and such provisions shall be of no further force or effect.

(b)            Section 3.08 of the Indenture shall be amended and restated in its entirety to read as follows:

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“ Section 3.08        RESTRICTED PAYMENTS .

The Company shall not, and shall not permit any of its Subsidiaries to, directly or indirectly, redeem, defease, repurchase, repay or make any payments in respect of, by the payment of cash or Cash Equivalents (in whole or in part, whether by way of open market purchases, tender offers, private transactions or otherwise), all or any portion of any unsecured Subordinated Indebtedness (or any extension, refinancing or renewal thereof), whether by way of payment in respect of principal of (or premium, if any) or interest on such Indebtedness if at the time such payment is due or otherwise made or, after giving effect to such payment, an Event of Default pursuant to Sections 7.01(a) , (b) , (c) , (d)  or (h)  has occurred and is continuing.

(c)            Section 3.10 of the Indenture shall be amended and restated in its entirety to read as follows:

“ Section 3.10        LIENS .

The Company shall not, and shall not permit any of its Subsidiaries to, directly or indirectly, allow or suffer to exist any Lien upon or in any property or assets (including accounts and contract rights) owned by the Company or any of its Subsidiaries other than (i) Permitted Liens and (ii) Liens securing Indebtedness permitted under Section 3.11.”

(d)            Section 3.11 of the Indenture shall be amended and restated in its entirety to read as follows:

“ Section 3.11        INDEBTEDNESS .

The Company shall not, and shall not permit any of its Subsidiaries to, directly or indirectly, create, incur, issue, assume, guarantee or otherwise become directly or indirectly liable, contingently or otherwise (collectively, “incurrence”; provided that accretion or amortization of original issue discount shall not constitute an incurrence), with respect to any Indebtedness unless, in each case, (x) no Default or Event of Default shall have occurred and be continuing at the time of or as a consequence of such incurrence of Indebtedness, and (y) at the time of the incurrence of such Indebtedness the aggregate principal amount of all outstanding Indebtedness of the Company and its Subsidiaries (taking into account such incurrence of additional Indebtedness) shall not exceed the Permitted Indebtedness Amount.

(e)            Section 3.12(b)  of the Indenture shall be amended and restated in its entirety to read as follows:

“ At the end of each fiscal quarter, cash and Cash Equivalents shall not be less than the lesser of (i) $20 million and (ii) 50% of the aggregate principal amount of the Outstanding Securities. ”

(f)             The following is hereby added as a new Section 4.15 of the Indenture:

“ Section 4.15        ASSET SALES.

(a)           (i)            If the Company or a Pledged Subsidiary sells a material portion of the property and assets (other than a sale that constitutes a Permitted Disposition) of the Company and its Subsidiaries, taken as a whole, and such sale does not constitute a Fundamental Change (an “ Asset Sale ”), then within 360 calendar days after the receipt of the consideration therefor, the

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Company or a Subsidiary, at its option, may apply the net cash and Cash Equivalents received in respect of such Asset Sale (the “ Net Proceeds ”) (x) to make capital expenditures in the ordinary course of business of the Company and its Subsidiaries, (y) otherwise to acquire capital assets that are used or useful in the business of the Company or any of its Subsidiaries or (z) to make a Permitted Investment; provided that a binding commitment to make such expenditure or investment that is made not later than such 360th day shall be treated as such a permitted application of the Net Proceeds as of the date of such commitment so long as the Company or a Subsidiary enters into such commitment with the good faith expectation that such Net Proceeds will be applied to satisfy such commitment within 180 calendar days after the date such commitment is made and, in the event any such Net Proceeds are not actually so invested in accordance with this subsection (a)(i) by such 180th day, then such remaining Net Proceeds shall be applied in accordance with subsection (a)(ii) below.

(ii)           Any Net Proceeds that are not applied as provided in subsection (a)(i) above shall constitute “ Excess Proceeds ”.  When the aggregate amount of Excess Proceeds exceeds $1.0 million, the Company shall make an offer to all Holders of Securities (an “ Asset Sale Repurchase Offer ”) and, if required by the terms of any other Indebtedness that ranks equally with the Notes in right of payment (“ Pari Passu Indebtedness ”), to all holders of Pari Passu Indebtedness, to purchase the maximum principal amount of Securities and such other Pari Passu Indebtedness that can be purchased with the Excess Proceeds, pro rata in proportion to the respective outstanding principal amounts (together with premium, if any) of the Securities and such other Pari Passu Indebtedness.  The offer price in respect of Securities in any Asset Sale Repurchase Offer shall be 100% of the aggregate principal amount of such Securities plus accrued and unpaid interest to the date of purchase, subject to the right of the Holders of record on a Record Date to receive interest on the relevant Interest Payment Date in accordance with the procedures set forth in this Indenture and the Notes.

(b)           (i)            If the Company makes an Asset Sale Repurchase Offer pursuant to subsection (a) above, the Company shall provide to all Holders and the Trustee a notice (the “ Asset Sale Notice ”) with the following information (if applicable):

(A)           the occurrence of an Asset Sale;

(B)           that an Asset Sale Repurchase Offer is being made pursuant to this Section 4.15 and the maximum principal amount of the Securities that may be purchased by the Company pursuant to the Asset Sale Repurchase Offer;

(C)           the purchase price and the purchase date with respect to Securities purchased by the Company pursuant to the Asset Sale Repurchase Offer, which will be no earlier than 20 Business Days nor later than 35 calendar days from the date such notice is mailed (the “ Asset Sale Payment Date ”); provided that the Asset Sale Payment Date may be extended in accordance with applicable law;

(D)           the name and address of the Paying Agent and the Conversion Agent;

(E)           the then current Conversion Rate;

(F)           that the Holder shall have the right to withdraw any tendered Securities and the Holder’s election to require the Company to purchase such Securities; provided

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that the Paying Agent receives, not later than the close of business on the expiration date of the Asset Sale Repurchase Offer, a facsimile transmission or letter setting forth the name of the Holder, the principal amount of Securities tendered for purchase, and a statement that such Holder is withdrawing its tendered Securities and its election to have such Securities purchased;

(G)           that unless the Company defaults in the payment of the purchase price therefor, all Securities accepted for payment pursuant to the Asset Sale Repurchase Offer will cease to accrue interest on the Asset Sale Payment Date;

(H)           if the Securities to be repurchased are certificated, that the Holders electing to have any Securities purchased pursuant to the Asset Sale Repurchase Offer will be required to surrender such Securities to the Paying Agent at the address specified in the notice prior to the close of business on the third Business Day preceding the Asset Sale Payment Date;

(I)            if the Securities to be repurchased are represented by a Global Security, that the Holders electing to have any Securities purchased pursuant to the Asset Sale Repurchase Offer will be required to comply with the appropriate procedures of the Depositary; and

(J)            any other instructions, as determined by the Company, consistent with the provisions of this Section 4.15 , that a Holder must follow.

(ii)           The Company shall comply with the requirements of Rule 14e-1 under the Exchange Act and any other securities laws and regulations thereunder to the extent such laws or regulations are applicable in connection with the repurchase of Securities pursuant to a Asset Sale Repurchase Offer.  To the extent that the provisions of any securities laws or regulations conflict with the provisions of this Indenture, the Company will comply with the applicable securities laws and regulations and shall not be deemed to have breached its obligations described in this Indenture by virtue thereof.

(iii)          On the Asset Sale Payment Date, the Company shall

(A)           accept for payment such principal amount of the Securities required to be purchased under the Asset Sale Repurchase Offer or portions thereof properly tendered pursuant to the Asset Sale Repurchase Offer,

(B)           at or prior to 11:00 a.m., New York City time, deposit with the Paying Agent an amount equal to the aggregate Asset Sale Payment in respect of all Securities accept