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EP-4736303-A1 - EXTENDING THE OUTPUT VOLTAGE RANGE OF A CONVERTER

EP4736303A1EP 4736303 A1EP4736303 A1EP 4736303A1EP-4736303-A1

Abstract

A converter comprising a transformer. A secondary winding of the transformer is split into two secondary winding portions. A switch arrangement selectively connects these two secondary winding portions in series or in parallel. The converter is configured such that the secondary winding portions contribute to an output voltage of the converter in different half cycles of an alternating current or voltage provided to the transformer.

Inventors

  • ELFERICH, REINHOLD

Assignees

  • Signify Holding B.V.

Dates

Publication Date
20260506
Application Date
20240624

Claims (8)

  1. 1. A converter for providing an output voltage (Vo), the converter comprising: a transformer comprising a primary winding (Lp) and a secondary winding (Lsl, Ls2) magnetically coupled together, the secondary winding being sub-divided into a first secondary winding (Lsl) and a second secondary winding (Ls2), wherein a voltage (Vo) between a first end (Lsl A) of the first secondary winding and a first end (Ls2A) of the second secondary winding defines the output voltage; and a switch arrangement comprising a switch (SI) having a first switch end (s) connected to a second end (LslB) of the first secondary winding and a second switch end (d) connected to a second end (Ls2B) of the second secondary winding and wherein the switch arrangement is configured to controllably switch the first secondary winding and the second secondary winding between being connected in parallel and being connected in series, a first diode (DI) connected from the second end (Ls2B) of the second secondary winding to the switch (SI); a second diode (D2) connected from the switch (SI) to the second end (LslB) of the first secondary winding (Lsl); a third diode (D3) connected from the first end (Ls2A) of the second secondary winding (Ls2) to the second end (LslB) of the first secondary winding (Lsl); a fourth diode (D4) connected from the second end (Ls2B) of the second secondary winding (Ls2) to the first end (Lsl A) of the first secondary winding (Lsl); a first capacitor (Co 12) connected between the first switch end (s) and the first end (Lsl A) of the first secondary winding (Lsl), and a second capacitor (Co22) connected between the second switch end (d) and the first end (Ls2A) of the second secondary winding (Ls2), wherein, when an alternating current flows through the primary winding, the first secondary winding and second secondary winding are configured to alternately contribute to the output voltage.
  2. 2. The converter of claim 1, wherein the first end of the second secondary winding is connected to a ground or reference voltage (GND).
  3. 3. The converter of any of claims 1 or 2, further comprising an output capacitor (Co) connected between the first end (Lsl A) of the first secondary winding (Lsl) and the first end (Ls2A) of the second secondary winding (Ls2).
  4. 4. The converter of any of the preceding claims, further comprising a switch controller configured to control the operation of the switch arrangement, wherein the switch controller is configured to: monitor the output voltage; responsive to the output voltage exceeding a first voltage level, control the switch arrangement to connect the first secondary winding and the second secondary winding in parallel; and responsive to the output voltage falling below a second voltage level, control the switch arrangement to connect the first secondary winding and the second secondary winding in series.
  5. 5. The converter of claim 4, wherein the first voltage level is greater than the second voltage level.
  6. 6. The converter of any of the preceding claims comprising a resonant tank.
  7. 7. The converter of claim 6, wherein the resonant tank is an LLC resonant tank.
  8. 8. The converter of any of claims 6 or 7 comprising a switch network configured to controllably connect a DC power to the resonant tank.

Description

EXTENDING THE OUTPUT VOLTAGE RANGE OF A CONVERTER FIELD OF THE INVENTION The present invention relates to the field of converters. BACKGROUND OF THE INVENTION A converter is an electronic arrangement configured to convert a voltage and/or current of an (input) electrical power. Converters are generally designed to drive a load, such as an LED or LED arrangement. It is typical for a converter to comprise a transformer, formed of a pair of magnetically coupled windings. This achieves safety isolation. A resonant converter is a particular type of electrical power converter that contains an arrangement of inductors and capacitors configured to resonate at particular frequencies. The windings of any transformer in such a resonant converter can form part of the resonant circuit, as well as performing the function of safety isolation. One known type of resonant converter is an LLC converter. This shows a higher efficiency than an LCC converter and benefits from wide bandgap transistor technologies in terms of the potential size and loss reductions. There is an ongoing desire to increase the output voltage range of a converter. For instance, an LLC converter can exhibit a hard limit for the minimum output voltage below which it cannot supply any load. One way to obtain a wide output voltage range is to use a further power stage. It would be desirable to increase the output voltage range of a converter without the need for an additional and/or separate component or power stage, to provide a compact device and reduce material usage. SUMMARY OF THE INVENTION The invention is defined by the claims. According to examples in accordance with an aspect of the invention, there is provided a converter for providing an output voltage. The converter comprises: a transformer comprising a primary winding and a secondary winding magnetically coupled together, the secondary winding being sub-divided into a first secondary winding and a second secondary winding, wherein a voltage between a first end of the first secondary winding and a first end of the second secondary winding defines the output voltage; and a switch arrangement configured to controllably switch the first secondary winding and the second secondary winding between being connected in parallel and being connected in series. When an alternating current flows through the primary winding, the first secondary winding and second secondary winding are configured to alternately contribute to the output voltage. The present invention provides a converter with an AC -DC portion that performs bidirectional rectification using separate portions of the secondary winding of a transformer. In particular the secondary winding of a transformer is sub-divided or split into two portions, with the connection(s) being appropriately configured such that the two portions of the secondary winding contribute to the output voltage during different halfcycles of the alternating current. The present invention also advantageously allows for an increase in the voltage range of the output voltage. The voltage range for the output voltage, when the two parts of the secondary winding are connected in series, is different to when the two parts of the secondary winding are connected in parallel. By facilitating the selective connection of the two parts of the secondary winding (between being in series and being in parallel), an improved overall voltage range can be achieved. In some examples, the first end of the second secondary winding is connected to a ground or reference voltage. The switch arrangement may comprise a switch having: a first switch end connected to a second end of the first secondary winding and; a second switch end connected to a second end of the second secondary winding. In the context of the present invention, a first end and a second end of a winding are opposite ends of the winding. Thus, the first end of each winding is different to the second end of each winding. The connection between the switch and the end(s) of the first/secondary winding(s) may be via one or more further electrical components, such as diodes. The converter may further comprise a first diode connected from the second end of the second secondary winding to the switch. The converter may further comprise a second diode connected from the switch to the second end of the first secondary winding. The converter may further comprise a third diode connected from the first end of the second secondary winding to the second end of the first secondary winding. The converter may further comprise a fourth diode connected from the second end of the second secondary winding to the first end of the first secondary winding. The converter may further comprise a first capacitor connected between the first switch end and the first end of the first secondary winding. The converter may further comprise a second capacitor connected between the second switch end and the first end of the second secondary winding. The converte