Isolated driver

1. An isolated driver comprising a converter module realized to provide voltage and current output to a load; a feedback arrangement realized to monitor voltage and/or current during operation of the driver; and a converter controller for providing converter control signals (Cl, CF, VCON) to the converter module, and characterized in that the converter controller comprises

a single optocoupler connected by input terminals to the feedback arrangement, wherein the optocoupler is not conducting for indicating a fault condition; and

a switching circuit arrangement connected to output terminals of the optocoupler, comprising a number of semiconductor switches (Q 20 , . . . , Q 25 , Q 30 , . . . , Q 34 ) arranged to generate a converter control signal (Cl, CF, VCON) for placing the converter module of the driver into a low-output mode (M LO ) when a voltage across the optocoupler output terminals indicates a fault condition.

2. An isolated driver according to claim 1 , wherein the feedback arrangement is arranged in the secondary side (SS) of the isolated driver and the converter controller is arranged in the primary side (PS) of the isolated driver.

3. An isolated driver according to claim 1 , wherein the switching circuit arrangement is realized to latch a converter control signal (Cl, CF, VCON) in response to a fault condition.

4. An isolated driver according to claim 1 , wherein the switching circuit arrangement comprises a delay element (C delay ) realized to delay the fault condition response by a predefined duration (t delay ).

5. An isolated driver according to claim 1 , wherein the optocoupler is connected to the feedback arrangement such that a first output terminal of the optocoupler is at a low potential during normal operation and at a high potential during a fault condition.

6. An isolated driver according to claim 1 , wherein the converter module comprises an integrated circuit, and the switching circuit arrangement is realized to generate a converter control signal (Cl, CF, VCON) for connecting to a corresponding pin of the integrated circuit.

7. An isolated driver according to claim 1 , wherein a first converter control signal (Cl, CF) is generated in response to a first fault condition resulting in an increased voltage across the output terminals of the optocoupler, and a second converter control signal (VCON) is generated in response to a second fault condition resulting in a decreased voltage across the output terminals of the optocoupler.

8. An isolated driver according to claim 1 , realized as a UL class 2driver.

9. An LED lighting arrangement comprising an isolated driver according to claim 1 for driving an LED lighting load from a mains power supply.

10. An isolated driver comprising a converter module realized to provide voltage and current output to a load; a feedback arrangement realized to monitor voltage and/or current during operation of the driver; and a converter controller for providing converter control signals (CI, CF, VCON) to the converter module, and characterized in that the converter controller comprises

a single optocoupler connected by input terminals to the feedback arrangement, wherein the optocoupler is not conducting for indicating a fault condition; and

a switching circuit arrangement connected to output terminals of the optocoupler, comprising a number of semiconductor switches (Q 20 , . . . , Q 25 , Q 30 , . . . , Q 34 ) arranged to generate a converter control signal (CI, CF, VCON) for placing the converter module of the driver into a low-output mode (M LO ) when a voltage across the optocoupler output terminals indicates a fault condition,

wherein a converter control signal (CF) increases the switching frequency of the converter module in response to a fault condition.

11. A converter controller for an isolated driver, comprising

a single optocoupler comprising input terminals for connecting to a feedback arrangement of the isolated driver, wherein the optocoupler is not conducting for indicating a fault condition; and

a switching circuit arrangement connected to output terminals of the optocoupler, comprising a number of semiconductor switches (Q 20 , . . . , Q 25 , Q 30 , . . . , Q 34 ) arranged to generate a converter control signal (Cl, CF, VCON) for placing a converter module of the driver into a low-output mode (M LO ) when a voltage across the optocoupler output terminals indicates a fault condition.

12. A method of operating an isolated driver comprising a converter module to provide voltage and current output to a load, which method comprises the steps of

providing a feedback signal (SS_FB) from a feedback arrangement to monitor voltage and/or current during operation of the isolated driver; and

transferring said feedback signal through an optocoupler to a switching arrangement controlling the converter module;

characterized in that it further comprises the steps of:

providing a feedback signal (SS_FB) that causes the optocoupler not to be conducting for indicating a fault condition; and

placing the converter module of the driver into a low-output mode (M LO ) when a voltage across the optocoupler output terminals indicates a fault condition.

13. A method according to claim 12 , comprising the step of disabling the switching circuit arrangement during a startup and/or shutdown interval of the isolated driver.