CN217543223U - Detection circuit, drive device and light-emitting device - Google Patents

Abstract

The application relates to an electronic circuit, and provides a detection circuit, a driving device and a light-emitting device, wherein the detection circuit comprises a rectifier, a first rectifying branch, a second rectifying branch and a third rectifying branch; load terminals for connection to a load to couple the output of the rectifier to the load; and a sensing element for sensing an output current at the rectifier; wherein the rectifying branch comprises a silicon diode and a silicon carbide diode connected in series. The detection circuit is used for cutting off reverse current generated by reverse recovery effect of the silicon diode in the rectifying branch by replacing the silicon diode in the rectifying branch with the silicon carbide diode, and keeping the conduction loss consumption possibly small, thereby avoiding the problem of influencing the detection precision of the sensing element on the output current.

Description

Detection circuit, drive device and light-emitting device

Technical Field

The application belongs to the technical field of power supply circuits, and particularly relates to a detection circuit, a driving device and a light-emitting device.

Background

LED (light emitting diode) technology is widely used in lighting applications, and most outdoor lighting fixtures are beginning to be replaced by LED fixtures. LED lamps usually comprise a lighting unit and an LED driver, which is required to improve its performance, especially efficiency and miniaturization, the switching frequency of which becomes high, and conventional silicon components begin to be defective at a frequency of 200 kHz. Taking the full bridge LLC output rectifier as an example, at 200kHz, even the best silicon diodes have significant reverse recovery problems in Discontinuous Conduction Mode (DCM), which is worse and gets worse after system warm-up, which may lead to high power loss, especially in high output voltage applications.

In LED drivers, one sensing element is often used to sense the current flowing through. For example, as shown in fig. 1, a sensing element a is placed in a diode-based rectifier bridge for sensing the current flowing/output by the rectifier bridge. However, such a sensing element a is typically insensitive to current polarity, i.e. it will respond to current flowing through the sensing element a from the opposite direction. For example, when the input voltage at the input terminal in is negative, the upper left and lower right silicon diodes are turned on, the negative rectifying branch of the rectifier bridge is turned on, and the current flowing through the upper left sensing element (inductor) is the normal output current. However, when the input voltage returns to near zero crossing, the upper left and lower right silicon diodes will be biased off, and these two silicon diodes will generate reverse recovery current (see reverse current Ion shown in fig. 1), which is not normal output current and should not be sensed by the sensing element a, but since the sensing element a is not sensitive to polarity, the reverse recovery current will still be detected by the sensing element a and generate an error signal to the control part, which error signal deteriorates with the temperature or dimming condition, even though the fastest recovering silicon diode is used, and the error still seriously affects the detection accuracy. When a current transformer is used as the sensing element a, this reverse recovery current also accumulates magnetic flux in the current transformer and causes an error in the sensing of the normal operating current by the current transformer.

SUMMERY OF THE UTILITY MODEL

The application aims to provide a detection circuit, a driving device and a light-emitting device, and aims to solve the problem that the accuracy of detection current is influenced by the reverse recovery effect of a silicon diode in a traditional rectifier.

The basic idea of the utility model is that: a silicon carbide diode is utilized to replace a silicon diode on at least one rectifying branch of the rectifier to cut off reverse current generated by reverse recovery effect of the silicon diode, so that the reverse recovery current is prevented from flowing through a sensing element, the problem of influencing the accuracy of the detection current is solved, and the conduction loss can be kept to be small. And furthermore, a parallel branch is provided at two ends of the silicon carbide diode and the sensing element which are connected in series, a path for reverse recovery current to flow through is provided for the silicon diode on the rectifying branch with the opposite phase, the silicon diode is ensured to be closed before the phase of the input voltage changes at the next moment, and the silicon diode is prevented from being in a conducting state to cause the input voltage to be short-circuited.

A first aspect of an embodiment of the present application provides a detection circuit, including:

a rectifier having an input, at least one rectifying branch, and an output;

a load terminal for connection to a load to couple an output of the rectifier to the load; and

a sensing element for sensing an output current at the rectifier;

wherein the rectifying branch comprises a silicon diode and a silicon carbide diode connected in series.

The detection circuit is used for stopping the reverse current generated by the reverse recovery effect of another silicon diode in the rectifying branch to generate errors in the sensing element by replacing the traditional silicon diode of the rectifying branch on the rectifier by one silicon carbide diode, and keeps the possibility of small conduction loss, so that the reverse recovery current is prevented from flowing through the sensing element, and the problem of influencing the detection precision of the sensing element on the output current is solved. And, for using two carborundum diodes in a rectification branch, the utility model discloses only use a carborundum diode and a silicon diode in a rectification branch, saved the cost.

In one embodiment, the silicon carbide diode and the silicon diode are in series with the sensing element, the silicon carbide diode for blocking a reverse recovery current of the silicon diode from flowing through the sensing element.

Because the silicon carbide diode has almost no reverse recovery effect and can rapidly block a reverse current, the silicon carbide diode can play a role in rectifying and blocking the reverse recovery current of the silicon diode by replacing a traditional silicon diode, so that the sensing element is prevented from detecting the reverse recovery current to influence the detection precision.

In one embodiment, the detection circuit comprises two rectifying branches conducting in opposite phases, each rectifying branch comprising a silicon diode and a silicon carbide diode connected in series, respectively, and the sensing element comprises a current transformer.

Two rectification branches constitute the rectifier bridge of a full-bridge, all connect in series the carborundum diode that can block reverse recovery current on every rectification branch to no matter make the rectifier bridge be the normal phase and switch on or reverse phase switches on, can both not produce reverse recovery current, thereby avoid current transformer to detect and influence the detection precision.

It will be appreciated that the rectifier bridge may alternatively be a half-bridge rectifier bridge, that rectifier bridge requiring only a single rectifying branch, which accordingly has a series connection of one silicon diode and one silicon carbide diode.

In one embodiment, the current transformer comprises:

a first sensing coil and a second sensing coil respectively disposed in two of the rectifying branches, the first and second sensing coils for sensing a forward conducting current of the rectifying branch in which each is located; and

a feedback coil magnetically coupled to the first and second sensing coils for obtaining a signal related to the forward conduction current;

the silicon carbide diode is used to prevent the reverse recovery current from flowing through the respective first or second sensing coil to prevent the reverse recovery current from generating an error signal in the feedback coil.

This embodiment provides an implementation of a current transformer in which the forward conduction current of each rectifying branch can be accurately detected by the current transformer due to the provision of a silicon carbide diode capable of blocking the reverse recovery current, and the reverse recovery current can be prevented from generating and accumulating an error signal in the feedback coil due to the blocking of the reverse recovery current of each rectifying branch.

In one embodiment, the sensing element and the silicon carbide diode are connected in series on at least one of the rectifying branches between the input and the output of the rectifier for sensing the current of the corresponding phase of the rectifying branch. Alternatively, the sensing element is located between the output of the rectifier and the load terminal, and thus a single sensing element can sense two output currents of opposite phases, which can save one sensing element. In both cases, since the silicon carbide diode and the sensing element are connected in series, the silicon carbide diode can be effectively used to block the reverse recovery current of the silicon diode for the sensing element from flowing through the sensing element.

In one embodiment, the sensing element and the silicon carbide diode are connected in series in a rectifying branch, which further comprises a discharge resistor connected in parallel with the series connected sensing element and silicon carbide diode for allowing a reverse recovery current of the silicon diode of the other rectifying branch to flow through the discharge resistor.

The discharge resistor can switch off the silicon diode with enough current path to flow the reverse recovery current of the silicon diode to change the silicon diode from forward bias (on) to reverse bias (off), ensure to switch off the silicon diode before the voltage phase changes, avoid the transient short circuit of the rectifier bridge, and bypass the silicon carbide diode and the sensing element through the current path, and still avoid the error signal generated by the reverse recovery current flowing through the sensing element.

In one embodiment, the discharge resistor has a resistance value greater than 5 × 10 ⁵ Ohm. Through the simulation and the experiment, the method has the advantages that, this embodiment provides an effective threshold value for the discharge resistor. However, this is merely an example and is not limited to other embodiments in which the threshold value must be used, and the threshold value may be adjusted as the operating frequency and device parameters of the rectifier change.

In one embodiment, the load circuit further comprises a load capacitor connected between the output of the rectifier and the load terminal.

The load capacitor is used for filtering the ripple of the output of the rectifier, and can ensure that stable power supply voltage can be provided for the load.

A second aspect of the embodiments of the present application provides a driving apparatus including a resonant converter including a half-bridge inverter generating a high-frequency alternating-current signal, a power converter converting the high-frequency alternating-current signal, and the above-mentioned detection circuit, wherein an output of the power converter is connected to the rectifier for rectifying and outputting the converted high-frequency alternating-current signal to the load;

the driving apparatus further comprises a control circuit connected to the sensing element for controlling the operation of the half-bridge inverter and the power converter in accordance with the sensed output current.

Based on the detection circuit capable of accurately detecting the output current, the driving device can control the work of the half-bridge inverter and the power converter according to the accurately detected output current without being influenced by the error of the reverse recovery current of the silicon diode, so that accurate power is provided for a load, and the requirement of a high-frequency switching power supply is met.

In one embodiment, the method further comprises the following steps: the reference current supply circuit is used for supplying a reference current;

the control circuit is configured to control operation of the half-bridge inverter and the power converter such that the output current coincides with the reference current.

In this embodiment, the reference current provides a circuit arrangement in a feedback loop of the driving apparatus, which provides a reference current, and receives and compares the output current sensed by the detection circuit with the reference current, and when the two are different, the control circuit controls the operation of the half-bridge inverter and the power converter so that the output current matches the reference current, so as to eliminate the difference and realize accurate closed-loop control of automatic adjustment.

A third aspect of the embodiments of the present application provides a light emitting device, including the driving device described above and a light source as the load, the light source being, for example, an LED.

The above-mentioned and non-mentioned advantages of the present application will be described in the detailed description section or will be understood by those of ordinary skill in the art with reference to the following drawings.

Drawings

FIG. 1 is a circuit diagram of a conventional detection circuit;

fig. 2 is a circuit diagram of a detection circuit according to an embodiment of the present application;

fig. 3 is a circuit diagram of a detection circuit according to a second embodiment of the present application;

fig. 4 is a circuit diagram of a detection circuit according to a third embodiment of the present application;

fig. 5 is a circuit diagram of a driving device according to an embodiment of the present disclosure.

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects to be solved by the present application clearer, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.

It will be understood that when an element is referred to as being "secured to" or "disposed on" another element, it can be directly on the other element or be indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or be indirectly connected to the other element.

It will be understood that the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like, refer to an orientation or positional relationship illustrated in the drawings for convenience in describing the present application and to simplify description, and do not indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and thus should not be construed as limiting the present application.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or to implicitly indicate the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present application, "a plurality" means two or more, and "several" means one or more unless specifically limited otherwise. The terms "part", "another part" are used only to describe that two features are different and are not otherwise limited to mean that the symbol "/" means "or".

Referring to fig. 2 and 3, a detection circuit 10 according to a first aspect of an embodiment of the present disclosure includes a rectifier 11, a load terminal 12, and a sensing element 13.

The rectifier 11 has an input in, at least one rectifying branch and an output out; in this example, the rectifier 11 is a full-bridge (wave) rectifier circuit, which includes two rectifying branches. Load terminals 12 for connection to a load to couple the output of the rectifier 11 to the load; the sensing element 13 is used to sense the output current at the rectifier 11; wherein the rectifying branch comprises a silicon diode 111/112 and a silicon carbide diode 113/114 connected in series. Typically, a load capacitor 14 is also included, connected between the output of the rectifier 11 and the load terminal 12. The load capacitor 14 is used to filter out the ripple in the output of the rectifier 11, ensuring that clean power can be supplied to the load.

The load terminal 12 includes a positive electrode and a negative electrode. In one embodiment, referring to fig. 2, the rectifier 11 comprises two rectifying branches, with the upper end of the input (terminal) in being positive and the lower end being negative, and the rectifying branch conducting the positive phase input voltage comprises a silicon diode 111 and a silicon carbide diode 113 connected in series across the load; the rectifying branch conducting the negative phase input voltage comprises a silicon diode 112 and a silicon carbide diode 114 connected in series across the load, wherein the silicon diode 112 is connected in series across the positive pole of the load terminal 12 and the silicon carbide diode 114 is connected in series across the negative pole of the load terminal 12. In another embodiment, referring to fig. 3, the rectifying branch of the rectifier 11 conducting positive phase input voltage is the same as the rectifying branch conducting positive phase input voltage of fig. 2, except that the silicon diode 112 in the rectifying branch conducting negative phase input voltage is connected in series with the negative terminal of the load terminal 12 and the silicon carbide diode 114 is connected in series with the positive terminal of the load terminal 12. In other embodiments, such as where the rectifier 11 is a half-bridge (wave) rectifier circuit, only one rectifying branch is required, which includes a silicon diode and a silicon carbide diode in series.

Since the sic diode has no significant reverse recovery effect and is capable of rapidly blocking reverse current, by replacing one of the silicon diodes of the rectifying branch with one of the sic diodes 113/114, the conduction loss depletion can be kept small (the use of the sic diode for all of the rectifying branch would result in excessive conduction loss). And the sensing element 13 is connected in series at one side of the silicon carbide diode 113/114, the silicon carbide diode 113/114 can play a role of rectification and can block the reverse recovery current of the silicon diode 111/112 from flowing through the sensing element 13. Referring to fig. 3, assuming that the rectifier bridge is turned on when the positive phase input voltage is applied, the sic diode 113 and the si diode 111 are turned on, and the sensing coil L1/L3 in the sensing element 13 will sense the output current. When the input voltage is near the zero crossing point, one path of the reverse recovery current Ioff of the silicon diode 111 will be blocked by the silicon carbide diode 113 (the reverse recovery current Ioff in fig. 3 is not actually present), so that the sensing element 13, such as the sensing coil L1/L3, will not detect or accumulate the reverse recovery current to affect the detection accuracy. Based on similar principles, in the rectifying branch where the negative phase input voltage is conducting, the sic diode 114 will block the reverse recovery current of the si diode 112, which the sensing coil L2/L3 does not detect or accumulate to affect the detection accuracy.

As mentioned above, the detection circuit 10 comprises rectifying branches conducting in opposite phases, each comprising one silicon diode 111/112 and one silicon carbide diode 113/114 respectively connected in series, while the sensing element 13 comprises a current transformer to be connected in series with the silicon carbide diodes 113/114. The two rectifying branches form a full-bridge rectifying bridge, and each rectifying branch is connected with a silicon carbide diode 113 and 114 capable of blocking reverse recovery current in series, so that no matter the rectifying bridge is connected with positive phase input voltage or negative phase input voltage, reverse recovery current can not be generated, and detection accuracy is prevented from being influenced by detection of a current transformer.

In one embodiment, a current transformer comprises: a first sensing coil L1, a second sensing coil L2 and a feedback coil L3, the first and second sensing coils L1, L2 being respectively placed in the two rectifying branches, the first and second sensing coils L1, L2 being used to sense the forward conducting current of the respective rectifying branch in which they are located; the feedback coil L3 is magnetically coupled to the first and second sensing coils L1, L2 for obtaining a signal related to the forward conduction current in each sensing coil L1, L2. The silicon carbide diodes 113/114 serve to prevent reverse recovery current of the silicon diodes 111/112 from flowing through the respective first sensing coil L1 or second sensing coil L2 to prevent the reverse recovery current from generating an error signal in the feedback coil L3. Therefore, the forward conduction current of each rectifying branch can be accurately detected by the current transformer, and since the reverse recovery current of each rectifying branch is blocked, the reverse recovery current can be prevented from generating an error signal in the feedback coil L3.

The sensing element 13 and the silicon carbide diodes 113/114 are connected in series on at least one rectifying branch between the input and the output of the rectifier 11 for sensing the current of the corresponding phase of this rectifying branch. In particular, the provision of the sensing element 13 inside the rectifier 11 ensures that the silicon carbide diode can block a reverse recovery current or an external disturbance current thereto, and can ensure detection accuracy of the output current of the rectifier 11. Alternatively, the sensing element 13 is located between the output in of the rectifier 11 and the load terminal 12, and thus a single sensing element 13 may sense two output currents of opposite phases, which can save one sensing element. In both cases, since the silicon carbide diodes 113/114 and the sensing element 13 are connected in series, the silicon carbide diodes 113/114 can be effectively used to block the reverse recovery current of the silicon diodes 111/112 for the sensing element 13 from flowing through the sensing element 13.

Through further simulations and experiments, another problem was found: since the reverse recovery current Ioff of the silicon diode is blocked by the silicon carbide diode, the charge of the silicon diode is not discharged and is not completely biased off. Taking fig. 2 and 3 as an example, assuming that the rectifier bridge is turned on when a positive phase input voltage is applied, the silicon carbide diode 113 and the silicon diode 111 are turned on, and the sensing coil L1/L3 in the sensing element 13 will sense the output current. When the input voltage is switched from positive phase to negative phase, the silicon carbide diode 114 shown in fig. 2 and the silicon diode 112 shown in fig. 3 are turned on, the reverse recovery current Ion1 of the silicon diode 111 shown in fig. 2 flows from the anode thereof to the input through the silicon carbide diode 114, the reverse recovery current Ion2 shown in fig. 3 flows from the anode thereof to the input through the silicon diode 112 and to the cathode thereof through the input current, the cathode to the anode of the silicon diode 111 are turned on, and this causes the anode and the cathode of the input voltage to be approximately short-circuited, and the reverse recovery current of the silicon diode 111 is not turned off until the reverse recovery current is completely discharged. As indicated by the dashed lines Ion1, ion2 of the response. Such a short circuit may result in increased power consumption.

To solve this problem, the present application proposes a further improvement. Referring to fig. 4, each rectifying branch further includes a discharge resistor 116, the discharge resistor 116 being connected in parallel with the series-connected sensing element 13 and the sic diode 113/114 for allowing the reverse recovery current of the si diode 111/112 to flow through the discharge resistor.

The discharge resistor 116 can form a current path for passing a sufficient reverse recovery current to turn the silicon diode 111/112 from forward bias to reverse bias during the process of turning off the silicon diode 111/112, ensure that the silicon diode is turned off before the voltage phase changes, and ensure that the silicon diode 111/112 is turned off before the voltage phase changes, thereby avoiding transient short circuit of the rectifier bridge. And bypasses the current of the silicon carbide diode 113/114 and the inductive element 13 through this current path, thereby preventing the reverse recovery current Ion3 from generating an error signal in the feedback coil L3. Specifically, also taking the foregoing scenario as an example, when the input voltage reaches from the positive phase near the zero crossing, the reverse recovery current Ion3 of the silicon diode 111 flows from the load capacitance 14 to the discharge resistor 116 that is in parallel with the sensing coil L2 and the silicon carbide diode 114, and flows back to the anode of the silicon diode 111, discharging and turning off, as shown by the dashed line Ion3 in fig. 4. The reverse recovery current Ion3 does not flow through any of the sensing coils L3/L2. When the input voltage reaches the negative phase and the silicon diode 112 is turned on, the silicon diode 111 is already turned off, and thus the input voltage is not short-circuited.

In one embodiment, the discharge resistor 116 has a resistance value greater than 5 × 10 ⁵ Ohm. Here only the effective threshold of one discharge resistor 116 is provided; this is merely an example and is not intended to limit the threshold value that must be used in other embodiments, but rather the threshold value may be adjusted as the operating frequency and device parameters of rectifier 11 change.

Referring to fig. 5, a driving apparatus according to a second aspect of the embodiment of the present application includes a resonant converter, which includes a half-bridge inverter 20 generating a high-frequency ac signal, a power converter 30 converting the high-frequency ac signal, and the above-mentioned detection circuit 10, wherein an output of the power converter 30 is connected to a rectifier 11, and the rectifier 11 is configured to rectify and output the converted high-frequency ac signal to a load; the driving apparatus further comprises a control circuit 101 connected to the sensing element 13 for controlling the operation of the half-bridge inverter 20 and the power converter 30 in dependence of the sensed output current. Wherein the power converter 30 is an LLC resonant converter.

The operation of the driving device comprises controlling power switches M1 and M2 of a half-bridge inverter 20 to carry out switch switching control and on-off duration control according to a control signal output by a control circuit 101, so as to invert the input direct current into a high-frequency alternating current signal; and, the LLC resonant circuit in the power converter 30 performs power conversion on the high-frequency ac signal and outputs the high-frequency ac signal to the rectifier 11. Specifically, the driving apparatus is based on the detection circuit 10 capable of accurately detecting the output current, and then the operation of the half-bridge inverter 20 and the power converter 30 in the DCM mode or the CCM mode can be controlled according to the accurately detected output current, so as to provide accurate input power to the load and meet the load requirement.

The driving apparatus further includes a reference current providing circuit 102, and the reference current providing circuit 102 is used for providing a reference current. The control circuit 101 is used to control the operation of the half-bridge inverter 20 and the power converter 30 so that the output current coincides with the reference current. The reference current providing circuit 102 is disposed in a feedback loop of the driving apparatus, and provides a reference current, which can be set by a user according to a load requirement, and when the output current sensed by the receiving and detecting circuit 10 is compared with the reference current, and there is a difference therebetween, the control circuit 101 can control the resonant converter to adjust the output current to conform to the reference current based on the accurate detection of the detecting circuit 10, so as to eliminate the difference and realize accurate closed-loop control of automatic adjustment.

A third aspect of the embodiments of the present application provides a light emitting device including the driving device described above and a light source, such as an LED, as a load.

The above-mentioned embodiments are only used for illustrating the technical solutions of the present application, and not for limiting the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not depart from the spirit and scope of the embodiments of the present application, and they should be construed as being included in the present application.

Claims (11)

1. A detection circuit (10) comprising:

a rectifier (11) having an input (in), at least one rectifying branch, and an output (out); and

-load terminals (12) for connection to a load for coupling an output (out) of the rectifier (11) to the load;

it is characterized by also comprising:

-a sensing element (13) for sensing an output current at said rectifier (11);

wherein the rectifying branch comprises a silicon diode (111, 112) and a silicon carbide diode (113, 114) connected in series.

2. The detection circuit (10) according to claim 1, wherein the silicon carbide diode (113, 114) and the silicon diode (111, 112) are in series with the sensing element (13), the silicon carbide diode (113, 114) being configured to block a reverse recovery current of the silicon diode (111, 112) from flowing through the sensing element (13).

3. The detection circuit (10) according to claim 2, comprising two said rectifying branches conducting in opposite phases, each of said rectifying branches comprising respectively one silicon diode (111, 112) and one silicon carbide diode (113, 114) connected in series, said sensing element (13) comprising a current transformer.

4. The detection circuit (10) according to claim 3, wherein the current transformer comprises:

a first sensing coil (L1) and a second sensing coil (L2) respectively placed in both said rectifying branches, said first sensing coil (L1) and said second sensing coil (L2) being intended to sense the forward conducting current of the rectifying branch in which they are each located, and

a feedback coil (L3) magnetically coupled to the first sensing coil (L1) and the second sensing coil (L2) for obtaining a signal related to the forward conduction current,

the silicon carbide diodes (113, 114) are used to prevent the reverse recovery current from flowing through the respective first or second sensing coil (L1, L2) to prevent the reverse recovery current from generating an error signal in the feedback coil (L3).

5. The detection circuit (10) according to claim 1, wherein the sensing element (13) and the silicon carbide diode (113, 114) are connected in series on at least one of the rectifying branches between an input (in) and an output (out) of the rectifier (11), or

The sensing element (13) is located between the output (out) of the rectifier and the load terminal (12).

6. The detection circuit (10) according to claim 5, wherein the rectifying branch further comprises a discharge resistor (116), the discharge resistor (116) being connected in parallel with the series connection of the sensing element (13) and the silicon carbide diode (113, 114) for allowing a reverse recovery current of the silicon diode (111, 112) to flow through the discharge resistor (116).

7. The detection circuit (10) of claim 6, wherein the discharge resistor (116) has a resistance value greater than 5 x 10 ⁵ Ohm.

8. The detection circuit (10) according to any one of claims 1 to 5, further comprising a load capacitance (14) connected between an output (out) of the rectifier (11) and the load terminal (12).

9. A drive apparatus (100) comprising a resonant converter including a half-bridge inverter (20) generating a high-frequency alternating-current signal and a power converter (30) converting the high-frequency alternating-current signal, and the detection circuit (10) according to any one of claims 1 to 8, wherein an output of the power converter (30) is connected to the rectifier (11), and the rectifier (11) is configured to rectify and output the converted high-frequency alternating-current signal to a load,

the driving arrangement (100) further comprises a control circuit (101) connected to the sensing element (13) for controlling the operation of the half-bridge inverter (20) and the power converter (30) in dependence of the sensed output current.

10. The drive device according to claim 9, further comprising:

a reference current providing circuit (102) for providing a reference current;

the control circuit (101) is configured to control the operation of the half-bridge inverter (20) and the power converter (30) such that the output current coincides with the reference current.

11. A light emitting device, characterized by comprising the driving device (100) of claim 9 or 10 and a light source as a load.

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