LED DRIVER

• US 20170079098A1
• Filed: 02/05/2015
• Published: 03/16/2017
• Est. Priority Date: 03/06/2014
• Status: Active Grant

• Current Assignee: Tridonic GmbH & Co. KG (Zumtobel Group AG)
• Original Assignee: Tridonic GmbH & Co. KG (Zumtobel Group AG)
• Inventors: Makwana, Deepak, Mitterbacher, Andre, Dalby, Paul, Bell, Wayne
• Granted Patent: US 10,172,195 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H02M 3/33507 with automatic control of the output voltage or current, e.g. flyback converters H02M3/33561, H02M3/33569 take precedence
• CPC Class Codes: H02M 3/33523 with galvanic isolation between input and output of both the power stage and the feedback loop
• CPC Class Codes: H05B 45/382 with galvanic isolation between input and output
• CPC Class Codes: H05B 45/385 using flyback topology

Abstract

The invention relates to an operating device (1) for operating lighting means, in particular LEDs, comprising: a potential-isolated clocked converter (3), having a transformer (T), which has a primary winding (N1) and a seconding winding (N2), and having a controllable switch (M1) arranged on the primary side, wherein the converter (3) can be supplied with a supply voltage converter (3); means (4) for directly or indirectly sensing the output voltage (Vout); and a control unit (ST) for controlling the switch (M1), wherein the secondary current (I2) through the secondary winding (N2) linearly drops, starting from a position value (I2max), which the switch (M1) is switched off, wherein the control unit (ST) is designed to adaptively sense a discharge duration (Tdischarge) between a switch-off of the switch (M1) and a subsequent drop in the secondary current (12) to zero in order to control the secondary current (I2).

Claims

1. An operating device (1) for operating LED lighting means, comprising:

a potential-isolated clocked converter (3), having a transformer (T), which has a primary winding (N1) and a secondary winding (N2), and having a controllable switch (M1) arranged on the primary side, wherein the converter (3) is supplied with a supply voltage on the primary side and the lighting means is supplied on the secondary side by means of an output voltage (Vout) of the converter (3),

means (4) for directly or indirectly detecting the output voltage (Vout), and

a control unit (ST) for controlling the switch (M1),

wherein while the switch (M1) is turned off, the secondary current (I2) through the secondary winding (N2) drops linearly, starting from a positive value,

wherein the control unit (ST) is configured to detect adaptively a discharge duration (Tdischarge) between turning off the switch (M1) and a subsequent drop of the secondary voltage (I2) to zero.

2. An operating device (1) according to claim 1, wherein the discharge duration (Tdischarge) is determined by taking into account the detection of the steady output voltage (Vout) which results from turning off the switch (M1).

3. An operating device (1) according to claim 1, wherein the discharge duration (Tdischarge) is determined depending on a comparison between the detected output voltage and an adaptive threshold value (Vref_hi).

4. An operating device (1) according to claim 3, wherein the adaptive threshold value (Vref_hi) depends on a value of the steady output voltage (Vout) after the switch (M1) has been turned off.

5. An operating device (1) according to claim 4, wherein the control unit (ST) is configured to select the threshold value (Vref_hi) as a specific percentage below the value of the steady output voltage (Vout) available after the switch (M1) has been turned off.

6. An operating device (1) according to claim 1, wherein, to detect the discharge duration (Tdischarge), first the point of time (t4) of falling below a fixed threshold value (Vref_lo) can be determined by means of the detected output voltage (Vout), and then this point of time (t4) can be corrected by means of an adaptive time period (Δ

T).

7. An operating device (1) according to claim 6, wherein the adaptive time period (Δ

T) depends on a detected value of the steady output voltage (Vout) available after the switch (M1) has been turned off.

8. An operating device (1) according to claim 1 further comprising:

an analog-to-digital converter for converting the analogously acquired output voltage (Vout) into digital values, and

wherein the control unit (ST) is configured to detect the discharge duration (Tdischarge) between turning off the switch (M1) and the subsequent drop of the secondary voltage (I2) to zero, depending on the digital values.

9. A control unit (ST) for controlling an operating device (1) for LED lighting means, wherein the operating device (1) comprises a potential-isolated clocked converter (3), having a transformer (T) for a galvanic isolation between a primary side and a secondary side,

wherein the control unit (ST) comprises:

an output for transmitting a control signal (S/M1) to control a switch (M1) arranged in the converter (3) on the primary side, wherein, while the switch (M1) is turned off, the secondary current (I2) on the secondary side of the transformer (T) drops linearly, starting from a positive value (I2max),

an input for directly or indirectly detecting the output voltage (Vout) of the converter (3), and

wherein the control unit (ST) is configured to detect adaptively a discharge duration (Tdischarge) between a switch-off of the switch (M1) and a subsequent drop in the secondary current (I2) to zero in order to control the secondary current (I2).

10. A method for operating LED lighting means, by means of a potential-isolated clocked converter (3) having a transformer (T), which comprises a primary winding (N1) and a secondary winding (N2) and a controllable switch (M1) arranged on the primary side, wherein, while the switch (M1) is turned off, the secondary current (I2) through the secondary winding (N2) drops linearly, starting from a positive value I2max), wherein on the primary side, the converter (3) is supplied with a supply voltage, and the lighting means are supplied by means of an output voltage (Vout) of the converter (3), wherein a discharge duration (Tdischarge) is adaptively determined between a switch-off of the switch (M1) and a subsequent drop in the secondary current (I2) to zero in order to control the secondary current (I2).