Search

US-12628254-B2 - Operating MOSFET in linear mode for multi-group LEDs

US12628254B2US 12628254 B2US12628254 B2US 12628254B2US-12628254-B2

Abstract

An LED driver configured to control a LED fixture comprising a plurality of LED groups is described, each LED group comprising at least one LED forming a series connection with a switch, wherein the plurality of LED groups are arranged in a parallel connection, the LED fixture further comprising a capacitor arranged in a parallel connection to the plurality of LED groups, the LED driver comprising: a power converter for converting an input power from a power source to a current which is provided to the plurality of LED groups; a control unit configured to control the power converter to provide the current to the plurality of LED groups, and wherein the control unit is further configured to control an operation mode of the switch of the LED group between a nominal mode, wherein the switch operates in a closed nominal state or an open nominal state, and a transition mode, wherein the switch operates in a semi-closed state, wherein a gate to source voltage of the switch of the LED group is lower than the gate to source voltage of the respective switch when operated in the nominal mode, switch the current from flowing through a first LED group to flowing through a second LED group, wherein the first LED group has a higher forward voltage than the second LED group, by switching the switch of the first LED group in the open nominal state and the switch of the second LED group in the semi-closed state during a transient period.

Inventors

  • Machiel Slot
  • Franciscus Bernardus Marie Van Horck

Assignees

  • ELDOLAB HOLDING B.V.

Dates

Publication Date
20260512
Application Date
20230117
Priority Date
20220118

Claims (13)

  1. 1 . An LED driver configured to control a LED fixture comprising a plurality of LED groups, each LED group comprising at least one LED forming a series connection with a switch, wherein the plurality of LED groups are arranged in a parallel connection, the LED fixture further comprising a capacitor arranged in a parallel connection to the plurality of LED groups, the LED driver comprising: a power converter for converting an input power from a power source to a current which is provided to the plurality of LED groups; a control unit configured to control the power converter to provide the current to the plurality of LED groups, and wherein the control unit is further configured to: control an operation mode of the switch of the LED group between a nominal mode, wherein the switch operates in a closed nominal state or an open nominal state, and a transition mode, wherein the switch operates in a semi-closed state, wherein a gate to source voltage of the switch of the LED group is lower than the gate to source voltage of the respective switch when operated in the nominal mode, and switch the current from flowing through a first LED group to flowing through a second LED group, wherein the first LED group has a higher forward voltage than the second LED group, by switching the switch of the first LED group in the open nominal state and the switch of the second LED group in the semi-closed state during a transient period.
  2. 2 . The LED driver according to claim 1 , wherein the control unit is further configured to switch the switch of the second LED group in the closed nominal state after the transient period.
  3. 3 . The LED driver according to claim 2 , wherein the control unit is further configured to increase the gate to source voltage of the switch of the second LED group when switching from the semi-closed state to the closed nominal state after the transient period.
  4. 4 . The LED driver according to claim 1 , wherein the LED driver further comprises a first resistor comprising: an input connectable to the control unit, and an output connectable to the gate of the switch of the second LED group to arrange the first resistor in a serial connection with the gate of the switch of the second LED group, wherein the gate to source voltage of the switch decreases when switching the switch of the second LED group in the transition mode by transmitting a control signal from the control unit to the input of the first resistor.
  5. 5 . The LED driver according to claim 4 , wherein the LED driver comprises a first resistor switch which is arranged in a parallel connection with the first resistor, wherein the control unit is configured to control the first resistor switch, wherein the first resistor is arranged in a serial connection with the gate of the switch of the second LED group when the first resistor switch is switched open by the control unit.
  6. 6 . The LED driver according to claim 1 , wherein the LED driver further comprises a second resistor which is arrangeable in a serial connection with the LED fixture of the LED driver.
  7. 7 . The LED driver according to claim 6 , wherein a second resistor switch is arranged in a parallel connection with the second resistor, wherein the control unit is configured to control the second resistor switch.
  8. 8 . The LED driver according to claim 7 , wherein the control unit is configured to control the second resistor switch to an open state during the transient period.
  9. 9 . The LED driver according to claim 1 , wherein the control unit is configured to simultaneously control the switch of the first LED group in the open nominal state and the switch of the second LED group in the transition mode during the transient period.
  10. 10 . The LED driver according to claim 1 , wherein the transient period is between 1-10 microseconds, preferably between 1-5 microseconds, more preferably between 1-3 microseconds.
  11. 11 . The LED driver according to claim 1 , wherein the control unit comprises configuration data of the plurality of LED groups of the LED fixture, wherein the configuration data includes the nominal forward voltage of each LED group.
  12. 12 . An LED system comprising the LED driver according to claim 1 and a LED fixture comprising a plurality of LED groups, each LED group comprising at least one LED forming a series connection with a switch, wherein the plurality of LED groups are arranged in a parallel connection, the LED fixture further comprising a capacitor arranged in a parallel connection to the plurality of LED groups, and wherein the LED fixture further comprising a resistor arranged in a serial connection with the plurality of LED groups and a resistor switch arranged in a parallel connection with the resistor, wherein the control unit is configured to control the resistor switch.
  13. 13 . A method of controlling a LED fixture comprising a plurality of LED groups, each LED group comprising at least one LED forming a series connection with a switch, wherein the plurality of LED groups are arranged in a parallel connection, the LED fixture further comprising a capacitor arranged in a parallel connection to the plurality of LED groups, the method comprising: controlling the operation mode of the switch of the LED group between a nominal mode, wherein the switch operates in a closed nominal state or an open nominal state, and a transition mode, wherein the gate to source voltage of the switch of the LED group is lower than the gate to source voltage of the respective switch when operated in the closed nominal state, and switching the current from flowing through a first LED group to flowing through a second LED group, wherein the first LED group has a higher forward voltage than the second LED group, by switching the switch of the first LED group in the open nominal state and the switch of the second LED group in the transition mode during a transient period.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a 371 Application of International Application No. PCT/EP2023/050995, filed Jan. 17, 2023, which claims priority to Netherlands Application No. 2030587, filed Jan. 18, 2022, the disclosures of which are incorporated herein by reference in their entirety for all purposes. FIELD OF THE INVENTION The technical field of the present invention relates to the operation mode of switches for multi-group LEDs, which may in particular be used for or be part of an LED driver. BACKGROUND OF THE INVENTION In general, an LED based product, e.g. a LED fixture, is driven by an LED driver. The LED fixture in general comprises multi-group LEDs, i.e. groups of LEDs which are arranged in a parallel connection. Based on the color characteristics of the multi-group LEDs applied, a color by each LED group can be generated. When the LED driver switches between the different LED groups, e.g. to generate a color pattern, only one particular LED group is powered on and the other LED groups are powered off. The switching on/off of a LED group occurs by controlling a switch, e.g. a MOSFET, which is placed in serial connection with the LED group. Problems may arise when switching between two LED groups, wherein the forward voltage of each LED group is different. When switching from a LED group with a higher forward voltage to another LED group with a lower forward voltage, the LED driver experiences an unwanted peak-current, which may damage the switched LED group. SUMMARY OF THE INVENTION It is an object of the present invention to provide an improved LED driver, in particular being less prone to peak-currents, or at least to provide an alternative for known solutions. This object is achieved by providing an LED driver configured to control a LED fixture comprising a plurality of LED groups, each LED group comprising at least one LED forming a series connection with a switch, wherein the plurality of LED groups are arranged in a parallel connection, the LED fixture further comprising a capacitor arranged in a parallel connection to the plurality of LED groups, the LED driver comprising: a power converter for converting an input power from a power source to a current which is provided to the plurality of LED groups;a control unit configured to control the power converter, as such the power converter provides current to plurality of LED groups, and wherein the control unit is further configured to control the operation mode of the switch of the LED group between a nominal mode, wherein the switch operates in a closed nominal state or an open nominal state, and a transition mode, wherein the switch operates in a semi-closed state, wherein the gate to source voltage of the switch of the LED group is lower than the gate to source voltage of the respective switch when operated in the nominal mode, switch the current from flowing through a first LED group to flowing through a second LED group, wherein the first LED group has a higher forward voltage than the second LED group, by switching the switch of the first LED group in the open nominal state and the switch of the second LED group in the semi-closed state during a transient period. In accordance with the present invention, an LED driver is, in general, applied for powering an LED fixture. The LED fixture comprises a plurality of LED groups. Each LED group comprises at least one LED forming a series connection with a switch. The switch may be any kind of suitable switch, e.g. a MOSFET such as a Si MOSFET, a GaN MOSFET, or a Sic MOSFET, or a bipolar transistor. An LED group may e.g. comprise one or more LED(s), arranged in series and/or parallel to each other. The plurality of LED groups, or also defined as multi-group LEDs, are arranged in a parallel connection. For example, the multi-group LEDs may comprise a first LED group including one red LED, a second LED group including one blue LED and one green LED and a third LED group including one white LED. The different LED groups may e.g. be adapted to emit light with the same or different colour, temperature and/or intensity. Further, the LED fixture comprises a capacitor arranged in a parallel connection to the plurality of LED groups. Such a capacitor is applied in order to reduce a high frequency which may occur on the current supplied to the LED groups otherwise. The LED driver is adapted to be powered by a single main power source. The LED driver comprises a power converter, e.g. an AC/DC converter, adapted to convert an input power provided by the power source to a current which is provided to the plurality of LED groups. The power converter may e.g. comprise a buck/boost converter, a flyback converter, a power factor corrector (PFC) flyback converter, or another PFC-converter such as a PFC boost converter or an LLC converter. A control unit is configured to control the power converter, as such the power converter provides current to plurality