Isolated converter and LED driver using said isolated converter

Abstract

The isolated converter includes a transformer having a primary winding (in a primary side circuit) and a secondary winding magnetically coupled to the primary winding. A first Y capacitor is electrically connected between the primary side circuit and the secondary winding. A detection circuit is for detecting primary side information, preferably information about an input power source received at an input, more preferably whether the input power source is an alternating current (AC) power source or a direct current (DC) power source, and the detection circuit includes the first Y capacitor. The detection circuit enables the detected information to be directly supplied to a secondary side controller without the need for an optoisolator or other isolated data transmission. The detection circuit 20 includes a capacitor divider including the first Y capacitor C5 and further including a second impedance and a third capacitor C7 connected in series with the first Y capacitor C5, with the first Y capacitor C5, the second impedance C6 and the third capacitor C7 in series between the primary side ground PGND and the input 12, and the detection circuit is for detecting the voltage across the second impedance to obtain a signal indicative of the primary side information. Preferably, the second impedance includes a second capacitor C6.

Description

[Technical Field]

[0001] The present invention relates to an isolated converter, for example for use in an LED driver. [Background technology]

[0002] Isolated converters, such as flyback converters, are used for both AC / DC and DC / DC conversion with galvanic isolation provided between the input and any output. A flyback converter functions as a buck-boost converter with the inductor split to form a transformer, thus multiplying the voltage ratio and providing the added benefit of isolation.

[0003] In the on-state of the converter, energy is transferred from the input voltage source to the transformer, during which time the output capacitor supplies energy to the output load. In the off-state, energy is transferred from the transformer to the output load (and output capacitor). This is called the freewheeling phase.

[0004] Isolated topologies such as flyback topology are widely used in LED drivers. For various reasons, such as precise output current control at deep dimming levels, a microcontroller unit (MCU) is typically configured on the secondary side of the converter to achieve smart or digital control. Here, "configured on the secondary side" typically means that the MCU is electrically connected to the secondary winding or shares the same ground and secondary winding as the LED. This prevents any level shift or inaccuracy in current sensing and control.

[0005] Some applications require the driver to be able to function on a backup power source to protect against mains problems, for example for emergency lighting applications or for diagnostic functions. In such cases it is desirable to detect information about the input supply and configure the MCU to behave differently according to the detected information.

[0006] The challenge is to detect the input, e.g., mains power, signal and communicate the information about the input signal to the secondary MCU. There are several existing solutions, but the circuits are rather cumbersome or can only cover a part of the functional requirements.

[0007] A first known approach is to use an additional MCU to measure all mains-related information directly on the primary side. Here, "on the primary side" means that the MCU shares the input signal and the ground of the primary winding, and no level shifting is used. An isolated optical coupling is then used to transmit the information to the secondary-side MCU. For this purpose, an optocoupler is used to bridge the primary and secondary sides. This solution requires a considerable amount of additional circuitry.

[0008] A second known approach utilizes a high-voltage capacitor on the primary side to detect the mains input. If the input power is an AC voltage, a sinusoidal voltage signal can be generated, and again an optocoupler is used to transmit the signal to the secondary side. If the input power is a DC voltage, a constant voltage signal can be generated, so that the MCU on the secondary side can distinguish between AC and DC input power. This solution also requires additional circuitry and has limitations in detecting different input characteristics. Summary of the Invention [Problem to be solved by the invention]

[0009] Therefore, there is a need for a low-cost, simple isolated converter circuit that allows for sensing input power supply characteristics and providing this information to the secondary side of the isolated converter circuit. [Means for solving the problem]

[0010] US20150109832A1 discloses a flyback converter including a sending unit for sending control information to a primary side, the sending unit including a Y capacitor that provides an EMI noise path between the primary side and the secondary side.

[0011] JP2016163537A discloses a capacitor C15 connected across the primary and secondary sides.

[0012] US20150103568A1 discloses a power converter with a buffer capacitor across the input rather than across the primary and secondary sides.

[0013] The concept of the present invention is to provide a capacitor between the primary and secondary sides of the transformer of an isolated converter and use this capacitor as part of a detection circuit to detect whether the input is receiving AC or DC power. In this case, the detection circuit can be on the secondary side, thus providing information directly to a controller on the secondary side. The capacitor may already exist in the isolated converter as a well-known Y capacitor, and the concept of the present invention is to reuse the Y capacitor as part of the detection circuit that detects information on the primary side, with the detection circuit on the secondary side. More broadly, the detection circuit including the Y capacitor can detect various information about the input power source other than whether the input power source is AC or DC.

[0014] The invention is defined by the claims.

[0015] According to an example according to an aspect of the present invention, an input adapted to receive input power; output, a transformer including a primary winding connected to the input and a secondary winding magnetically coupled to the primary winding and connected to the output, the primary winding being connected in a primary side circuit; and an isolated converter having a first Y capacitor electrically connected between the primary side circuit and the secondary winding, The converter is An isolated converter is provided, further comprising a detection circuit for detecting information on the primary side, the detection circuit including the first Y capacitor.

[0016] Preferably, the detection circuit comprises a capacitor divider including the first Y capacitor and further including a second impedance and a third capacitor connected in series with the first Y capacitor, with the first Y capacitor, the second impedance and the third capacitor in series between primary side ground and the input, and the detection circuit is for detecting the voltage across the second impedance to obtain a signal indicative of information about the primary side.

[0017] Here, "connected" means directly electrically connected, as distinguished from magnetic coupling. The transformer has a capacitor between the primary side (e.g., primary ground) and the secondary side (e.g., secondary ground), the capacitor forming part of a detection circuit for detecting the nature of the signal at the input. The main circuit of the detection circuit is located at least on the secondary side, allowing the detected information to be directly supplied to a secondary-side controller without the need for an optoisolator or other isolated data transmission. In short, the first Y capacitor performs two functions: transmitting primary-side information across the transformer's isolation barrier and controlling EMI, a function of a (known) Y capacitor.

[0018] Preferably, the information is about the input power source received at the input. More preferably, the information is whether the input power source is an AC power source or a DC power source. The primary winding is part of a primary side circuit, e.g., having a main switch, and the transformer transfers power when the main switch is turned on and off. Commutate In another example, some high frequency modulated signals, such as power line communication signals encoded at high frequency in the input power supply, can also be transmitted across the isolation barrier via the Y capacitor. Going a step further, if the input power supply is an AC power supply, embodiments allow for determining the frequency of the AC input mains signal.

[0019] The converter may be, for example, a switch-mode power converter, and the main switch is a power switch of the switch-mode power converter. Many different topologies are possible. For example, the converter may comprise a flyback converter.

[0020] The detection circuit is preferably electrically connected to the secondary side ground terminal.

[0021] In one preferred embodiment, the second impedance comprises a second capacitor, which also provides good isolation and frequency selection / filtering functionality. In other examples, the second impedance could be a resistor, if the first Y capacitor and the third capacitor are already sufficient for frequency selection.

[0022] In one embodiment of the capacitor divider and the detection circuit, a first interconnection of the first Y capacitor and the second capacitor is connected to secondary side ground, and a second interconnection of the second capacitor and the third capacitor to the secondary side ground is adapted to provide a signal indicative of whether the input is receiving an AC power source or a DC power source.

[0023] The detection circuit is thus a series capacitor network, one of whose nodes provides the detection signal. The first Y capacitor not only enables detection of the input characteristic, but also provides a bridge between the primary ground and the secondary ground. The third capacitor provides a bridge between the detection circuit (especially the second interconnection) and the input on the primary side.

[0024] A resistor may also be provided in series with the first capacitor, the second capacitor, and the third capacitor, the resistor being connected between the input and the third capacitor, which provides improved electromagnetic interference performance.

[0025] Preferably, the first capacitor and the third capacitor each comprise one or more Y capacitors, and the second capacitor comprises one or more capacitors (which may be of any type) in series.

[0026] The first and third capacitors both bridge between the primary and secondary sides, hence the use of a Y-capacitor. The second capacitor may take other forms.

[0027] The detection circuit may, for example, determining that the input is receiving AC power when the voltage on the second interconnect varies periodically; The input is adapted to determine that it is receiving a DC power source when the voltage on the second interconnect does not vary periodically.

[0028] The nature of the signal on the second interconnection thus indicates the type of input that is received. The second interconnection may be considered to define a detection node. The detection circuitry is used to, among other things, distinguish between an AC mains input and a DC input, for example from an emergency backup power source.

[0029] The detection circuit may further comprise, for example, a transistor circuit connected to the second interconnect for processing the voltage.

[0030] In one example, the transistor circuit includes a diode-connected transistor between a transistor circuit input and the secondary-side ground, a pull-up resistor connected to a voltage reference, and a pull-down transistor connected to the secondary-side ground, the diode-connected transistor being between a control gate of the pull-down transistor and the secondary-side ground, and the junction between the pull-up resistor and the pull-down transistor having a detection output.

[0031] The diode-connected transistor prevents excessive negative voltage in the circuit. The detection output can be considered to be a binary signal that is pulled up to a high voltage rail or pulled down to the secondary side ground.

[0032] In response to a DC input, the three capacitors act as a voltage divider, so the second interconnect is at a constant voltage and therefore the input to the transistor circuit is at a constant voltage. The pull-down transistor is turned off, so the detection output is pulled high. In response to an AC input, the voltage at the second interconnect varies periodically, causing the pull-down transistor to be turned on and off periodically. This generates a PWM detection output.

[0033] Therefore, the detection output can be interpreted as resulting from an AC or DC input. The circuit can also distinguish between an AC input and a rectified AC input in that the PWM signals have different duty cycles.

[0034] Alternatively, an analog detection signal (rather than a PWM signal) is possible by using more complex circuitry such as a voltage follower circuit rather than a pull-down transistor.

[0035] The transistors may be packaged on a single chip / IC with six pins, with each set of three pins for each transistor.

[0036] The converter may further comprise a resistor between the control gate of the pull-down transistor and the secondary-side ground, and a resistor between the input of the transistor circuit and the second interconnect.

[0037] The resistor acts as a resistive divider to set the appropriate control voltage level for the pull-down transistor.

[0038] A secondary side control circuit may be provided to which the detection output is supplied and adapted to control the output of the converter in accordance with the detection output, the secondary side control circuit being electrically connected to the secondary side ground.

[0039] In another embodiment of the capacitor divider and the detection circuit, a second interconnection of the second capacitor and the third capacitor is adapted to be connected to a secondary side ground, and a first interconnection of the first Y capacitor and the second capacitor to the secondary side ground is adapted to provide a signal indicative of the frequency of the AC input mains signal. This embodiment provides an alternative circuit of the capacitor divider and the detection circuit to the secondary side ground. It can be understood that the location of the ground is not limited and can be selected according to requirements by those skilled in the art.

[0040] The input is typically equivalent to ground.

[0041] The converter may further comprise a rectifier between the input and the primary winding, a capacitor across the input of the rectifier, and a capacitor across the output of the rectifier, the third capacitor being connected to the input before the rectifier.

[0042] The present invention also provides an LED driver having an isolation converter as defined above, the isolation converter including an input for connecting to an external power supply and an output for connecting to an LED load.

[0043] The present invention also provides a lighting device comprising an LED driver as defined above and an LED load connected to the LED driver.

[0044] These and other aspects of the invention will be elucidated and elucidated with reference to the following embodiments. [Brief explanation of the drawings]

[0045] For a better understanding of the present invention, and to show more clearly how the same may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings, in which: [Figure 1] 1 shows a generic isolated converter with an example of a detection circuit according to the present invention; [Figure 2] 2 shows the circuit of FIG. 1 with an example of an implementation of the primary side circuit. [Figure 3] The detection circuit is shown in more detail, among other things, with example component values. [Figure 4] 1 shows a first set of graphs illustrating circuit operation in response to an AC input. [Figure 5] 10 shows a second set of graphs to illustrate circuit operation in response to a 230V DC input. [Figure 6] 10 shows a third set of graphs illustrating circuit operation in response to a rectified AC input. DETAILED DESCRIPTION OF THE INVENTION

[0046] The present invention will be described with reference to the drawings.

[0047] It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the devices, systems, and methods, are for purposes of illustration only and are not intended to limit the scope of the invention. These and other features, aspects, and advantages of the devices, systems, and methods of the present invention will become better understood from the following description, appended claims, and accompanying drawings. It should be understood that the figures are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the figures to indicate the same or similar parts.

[0048] The present invention provides an isolated converter having a transformer with a primary winding (in a primary side circuit) and a secondary winding magnetically coupled to the primary winding. A first Y capacitor is electrically connected between the primary side circuit and the secondary winding. The detection circuit is for detecting primary side information, such as information about the input power source of the converter, more preferably whether the input is receiving AC power or DC power, or a high frequency modulated signal on the input power source. Importantly, the detection circuit includes the first Y capacitor. The detection circuit allows the detected information to be directly supplied to a secondary side controller without the need for an optoisolator or other isolated data transmission.

[0049] FIG. 1 shows a generalized isolated converter 10 with an example of a detection circuit according to the present invention.

[0050] Isolated converter 10 has an AC input 12 and an output Vbus, the output being isolated from the input by a transformer circuit shown generally as 14. The transformer circuit has a primary winding 16 connected to the input and a secondary winding 18 magnetically coupled to primary winding 16 and connected to the output Vbus. The primary winding is connected in a primary side circuit not shown in FIG. 1. Transformer circuit 14 can take a variety of forms depending on the converter topology.

[0051] The AC input is connected to the inputs of full-bridge rectifiers D1-D4 through an EMI filter and smoothing capacitor arrangement C1, C2, L1. For the purposes of this description, the "input" to the converter can be considered to be the EMI filtered signal supplied to the rectifier, or any pre-rectified signal, such as the AC input 12 before the EMI filter. The example of Figure 1 uses the input to the rectifier as the signal that should be coupled to the secondary to convey information about the input 12.

[0052] A smoothing capacitor C3 is provided across the output of the rectifier between the primary ground PGND and the primary rectified output PRECT. The rectifier output is fed to the primary circuit of the transformer circuit 14.

[0053] The output of the transformer circuit 14 defines the circuit output between the secondary ground SGND and the DC output line Vbus. A smoothing capacitor C4 is provided across the output.

[0054] The present invention provides a detection circuit 20 for detecting the characteristics of the power supply to the AC input 12, and in particular for determining whether the input is an AC mains signal or a DC signal, for example from a backup power supply. The detection circuit preferably also makes it possible to determine the frequency of the AC input mains signal. Optimally, the circuit can also be designed to distinguish between an AC input and a rectified AC input.

[0055] The detection circuit 20 is on the secondary side and connects to the secondary side ground SGND. The detection circuit 20 is also coupled to the primary side through two Y capacitors.

[0056] A first Y capacitor element C5 is electrically connected between the primary side, specifically the primary side PGND, and the secondary winding, specifically the secondary side ground SGND. This capacitor is known to improve EMI performance. This first Y capacitor has been proposed by the inventor as part of a novel detection circuit, and the Y capacitor can transmit information from the primary side to the secondary side.

[0057] The first Y capacitor is part of a capacitor divider including the first Y capacitor C5 and further including a second capacitor C6 and a third capacitor C7 connected in series with the first Y capacitor C5. The first Y capacitor C5, the second capacitor C6, and the third capacitor C7 are in series between the primary-side ground PGND and, in this example, the input to the rectifier (after the EMI filter). A first interconnection of the first Y capacitor C5 and the second capacitor C6 is connected to the secondary-side ground. A second interconnection 22 of the second capacitor C6 and the third capacitor C7 provides a signal indicating whether the input is receiving AC or DC power. This second interconnection 22 functions as a detection node. While the above embodiment takes the second capacitor as an example, it should be understood that the second capacitor is essentially an impedance and that a resistor can also be used. Because the principles are similar, this specification will not describe the invention in terms of a resistor as the second impedance.

[0058] The third capacitor C7 is another Y capacitor that, like the first Y capacitor C5, is electrically connected between the primary side, specifically the input to the rectifier, and the detection node of the detection circuit 20.

[0059] The first Y capacitor C5 of the series network is a first Y capacitor. The second capacitor C6 of the series network has one or more series capacitors that do not have to be Y capacitors. The third capacitor C7 of the capacitor network is a second Y capacitor.

[0060] The detection node provides a signal indicating whether the input is receiving an AC or DC power source, which may be interpreted to determine that the input is receiving a rectified AC signal.

[0061] The detection circuit therefore comprises a series capacitor network, with nodes connected to the input, the primary ground and the secondary ground, and the bridging capacitor between the primary and secondary is a Y-capacitor.

[0062] The first Y capacitor C5 not only forms part of the detection circuit but also improves EMI performance. The first Y capacitor C5 has a low capacitance value such as 3.3 nF.

[0063] The second capacitor C6 is the main detection element of the detection circuit. To account for voltage surges (4 kV) and bursts, capacitor C6 has a capacitance of, for example, 1 nF and is rated at 1 kV. The voltage drop across C6 is the voltage processed by the detection circuit. The second capacitor C6 allows the voltage at the detection node to vary rather than being tied to the secondary side ground SGND.

[0064] A third capacitor C7 provides coupling of the input voltage to the detection circuit.

[0065] The detection circuit is adapted to determine that the input is receiving an AC power source when the voltage at the detection node changes periodically, and to determine that the input is receiving a DC power source when the voltage at the detection node does not change periodically, for example, when the DC power source charges the capacitor only once and the voltage changes only during the charging period.

[0066] For this determination, the detection circuit comprises a transistor circuit connected to the detection node (ie, the second interconnect 22 between the second and third capacitors) for processing the detection node voltage.

[0067] The transistor circuit includes a diode-connected transistor Q1 between the transistor circuit input 24 and secondary-side ground SGND, a pull-up resistor R4 connected to a voltage reference Vref_3V3 (e.g., 3.3V IC power supply voltage), and a pull-down transistor Q2 connected to secondary-side ground SGND. The diode-connected transistor Q1 is between the base (i.e., control gate) of the pull-down transistor Q2 and secondary-side ground SGND. The junction between the pull-up resistor R4 and the pull-down transistor Q2 includes a detection output 26. This detection output 26 is supplied to a microcontroller unit (not shown) on the secondary side. The 3.3V IC power supply is, for example, the power supply for the microcontroller. The microcontroller is adapted to control the converter output according to the detection output and is electrically connected to secondary-side ground SGND.

[0068] The diode-connected transistor Q1 prevents excessive negative voltages in the circuit, and in particular has a very low leakage current, such as 110 nA, which is less than the allowable I / O leakage current of, for example, a microcontroller.

[0069] The sense output 26 can be considered to be a binary signal that is pulled up to the high voltage rail Vref_3V3 or pulled down to the secondary side ground SGND.

[0070] In response to a DC input, the three capacitors act as a voltage divider, so the detection node is at a constant voltage, and therefore the input node 24 to the transistor circuit is at a constant voltage. The voltage level (depending on the capacitor size) is such that the pull-down transistor Q2 is turned off so that the detection output 26 is pulled high. In response to an AC input, the voltage at the detection node (second interconnect 22) varies periodically, causing the pull-down transistor to be turned on and off periodically. This produces a PWM detection output.

[0071] The detection output can therefore be interpreted as resulting from an AC or DC input. The circuit can also distinguish between AC and rectified AC inputs in that the PWM signals have different duty cycles. Alternatively, an analog detection signal (rather than a PWM signal) is possible by using more complex circuitry, such as a voltage follower circuit rather than a pull-down transistor.

[0072] Resistor R3 is connected between the control gate of pull-down transistor Q2 and secondary ground SGND, and resistor R2 is between the input of the transistor circuit and the detection node. These resistors function as a resistor divider to set the appropriate control voltage level for the pull-down transistor. Notably, in response to a DC input, the voltage developed by the capacitor divider and resistor divider is less than the turn-on voltage of the pull-down transistor.

[0073] FIG. 2 shows the circuit of FIG. 1 with an example of an implementation of the primary side circuit.

[0074] The primary circuit includes a main switch M1 in series with the primary winding 16. The transformer transfers power as the main switch is turned on and off in a known manner. Commutate Figure 2 also shows the current sensing resistor R1.

[0075] Thus, FIG. 2 shows an embodiment of a switched mode power converter, in particular in the form of a flyback converter, where the main switch M1 is the power switch of the converter.

[0076] 2 further shows that another resistor R5 is in series with the first capacitor C5, the second capacitor C6, and the third capacitor C7 and is connected between the rectifier input and the first capacitor C5, the second capacitor C6, and the third capacitor C7, which provides improved electromagnetic interference performance.

[0077] Figure 3 shows the detection circuit in more detail, particularly with example component values, which are merely to indicate an order of magnitude and are in no way intended to be limiting.

[0078] FIG. 4 shows a first set of graphs to illustrate circuit operation in response to an AC input.

[0079] The top graph shows the sensed output at node 26, the middle graph shows the sensed input at transistor circuit input node 24, and the bottom graph shows input 12.

[0080] The detection output is a PWM signal.

[0081] FIG. 5 shows a second set of graphs to illustrate circuit operation in response to a 230V DC input.

[0082] Again, the top graph shows the sense output at node 26, the middle graph shows the sense input at transistor circuit input node 24, and the bottom graph shows input 12. The sense input remains near zero so that pull-down transistor Q2 is not turned on. The sense output is a constant 3.3V signal.

[0083] FIG. 6 shows a third set of graphs illustrating circuit operation in response to a rectified AC input.

[0084] Again, the top graph shows the sensed output at node 26, the middle graph shows the sensed input at transistor circuit input node 24, and the bottom graph shows input 12.

[0085] The graph is similar to Figure 4, but the duty cycle of the detector output is changed (increased), so it is possible to distinguish between an AC input signal and a rectified AC input signal.

[0086] The present invention is interesting for all isolated LED drivers with mains protection or for emergency lighting applications. The present invention is for example interesting for radio drivers where the control circuit on the secondary side receives a radio control signal. The present invention can be used for example in the design of a 36W radio driver with a flyback (PFC) converter and a DC / DC buck converter. The controller is preferably on the secondary side, so the output side is isolated from the mains input by a flyback transformer and a Y capacitor.

[0087] In the above embodiment, it is the first interconnection between the Y capacitor C5 and the second capacitor C6 that connects to the secondary side ground (SGND). Below, an alternative embodiment is presented in which the second interconnection between the second and third capacitors is connected to the secondary side ground, but the voltage across the second capacitor is still sensed to determine the primary side information.

[0088] Figure 7 shows this embodiment, and for ease of understanding, capacitors C3, C5, and C4 in Figure 7 correspond to capacitors C5, C6, and C7, respectively. In Figure 7, the interconnection between capacitors C5 and C4 is connected to the secondary side ground. The voltage across capacitor C5 is used to detect primary side information, more specifically, the frequency of the AC input. The other end of capacitor C4 is connected to ground, which is also the AC input.

[0089] The main elements of the present invention are as follows:

[0090] That is, add a lower voltage, higher value capacitor C5 (compared to the original Y capacitor C3 across the isolation barrier) in series with the Y capacitor C3 across the isolation barrier, and then measure the voltage signal of the added capacitor C5 with respect to secondary side ground. This is shown diagrammatically in Figure 7.

[0091] An MCU on the secondary isolated side (already present in LED drivers with diagnostics) can be used to measure the signal across the capacitor across the isolation barrier and detect the frequency of this signal. Some signal shaping can be used to keep the upper and lower voltages at the MCU supply voltage and ground to put a kind of square wave into the MCU pin, making frequency determination easier. In this case even a simple I / O pin can be used and there is no need to use the ADC input of the MCU.

[0092] Figure 7 shows the boost PFC first and flyback DC / DC converter / stages, the primary rectifiers (D1-D4), capacitor C3 bridging the isolation from the primary side to the secondary side of the LED driver, and capacitor C4 connecting the output stage to ground. Additionally, a 3.3V voltage source V2 provides power to the microprocessor circuitry on the secondary side. Additional circuitry added as part of this invention includes R3, C5, D5, and D6. C5 is added in series with C3 (C3 and a 1:10 divider capacitor). The voltage between C3 and C5 is then sensed directly at the MCU pin via R3. Clamping diodes D5 and D6 are added to limit the voltage at the MCU pin to common ground and Vdd.

[0093] In Figure 8, the simulation shows the resulting waveform observed by the MCU at "Vsense", or the voltage across D6 in the circuit diagram of Figure 7. As can be seen, the frequency measured in this waveform is 60Hz, which is exactly the frequency of the mains voltage. This shows that by simply adding a simple low-voltage circuit on the isolated secondary side, the frequency of the mains voltage can be accurately measured without any additional components across the isolation barrier, making this circuit a very simple and cost-effective way to measure the frequency of the mains voltage from the isolated secondary side of an LED driver.

[0094] Those skilled in the art can understand and effect modifications to the disclosed embodiments in practicing the claimed invention from a study of the drawings, the specification, and the appended claims. While the above embodiment focuses on whether the input power is AC or DC as the information to be detected, in alternative embodiments, the information may be a high-frequency modulated signal in the input power, or some high frequency injected by the primary-side circuit itself. In the claims, the word "comprising" does not exclude other elements or steps, and the singular does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. It should be noted that when the term "adapted to" is used in the claims or the description, the term "adapted to" is intended to be equivalent to the term "configured to." Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. an input adapted to receive input power; output, a transformer including a primary winding connected to the input and a secondary winding connected to the output, the secondary winding magnetically coupled to the primary winding and adapted to connect to an LED load, the primary winding being connected in a primary side circuit; an isolated converter having a first Y capacitor electrically connected between the primary side circuit and the secondary winding, The isolation converter is a detection circuit for detecting information on the primary side, the detection circuit including the first Y capacitor; the detection circuit includes a capacitor divider including the first Y capacitor, and further including a second impedance and a third capacitor connected in series with the first Y capacitor, with the first Y capacitor, the second impedance, and the third capacitor in series between primary side ground and the input; The isolation converter, wherein the detection circuit is for detecting a voltage across the second impedance to obtain a signal indicative of information on the primary side.

2. the detection circuit is for detecting information about the input power source received at the input; 2. The isolated converter of claim 1, wherein the primary side circuit has a main switch, and the transformer is used to commutate power when the main switch is turned on and off.

3. The detection circuit the input is for detecting whether it is receiving AC power or DC power; The isolated converter of claim 2 , wherein the isolated converter comprises a flyback converter.

4. The detection circuit for detecting whether the input is receiving a radio frequency encoded signal on the input power source; The isolated converter of claim 2 , wherein the isolated converter comprises a flyback converter.

5. The detection circuit to enable the frequency of the AC voltage of the input power source to be determined, The isolated converter of claim 2 , wherein the isolated converter comprises a flyback converter.

6. 6. The isolated converter according to claim 1, wherein the detection circuit is electrically connected to a secondary side ground, the secondary side ground being at a current input terminal of the secondary winding, and the primary side ground being electrically connected to a current output terminal of the primary winding.

7. The isolation converter according to claim 1 , wherein the second impedance comprises a second capacitor or a resistor.

8. 8. The isolated converter of claim 7, wherein a first interconnection of the first Y capacitor and the second capacitor is connected to a secondary side ground, and a second interconnection of the second capacitor and the third capacitor to the secondary side ground is adapted to provide a signal indicative of whether the input is receiving an AC power source or a DC power source.

9. further comprising a resistor in series with the first Y capacitor, the second capacitor, and the third capacitor, the resistor being connected between the input and the third capacitor; 8. The isolated converter of claim 7, wherein the first Y-capacitor and the third capacitor each comprise one or more Y-capacitors, and the second capacitor comprises one or more capacitors in series.

10. The detection circuit determining that the input is receiving AC power when the voltage on the second interconnect varies periodically; 9. The isolated converter of claim 8, adapted to determine that the input is receiving a DC power source when the voltage on the second interconnect does not vary periodically.

11. 11. The isolated converter of claim 10, wherein the detection circuit further comprises a transistor circuit connected to the second interconnect for processing the voltage.

12. 12. The isolated converter of claim 11, wherein the transistor circuit comprises a diode-connected transistor between a transistor circuit input and the secondary-side ground, a pull-up resistor connected to a voltage reference, and a pull-down transistor connected to the secondary-side ground, the diode-connected transistor being between a control gate of the pull-down transistor and the secondary-side ground, a junction between the pull-up resistor and the pull-down transistor comprising a detection output, and a resistor between the control gate of the pull-down transistor and the secondary-side ground and a resistor between the input of the transistor circuit and the second interconnection.

13. 13. The isolated converter of claim 12, further comprising a secondary-side control circuit supplied with the detection output and adapted to control the output of the isolated converter according to the detection output, the secondary-side control circuit electrically connected to the secondary-side ground.

14. a second interconnection of the second capacitor and the third capacitor adapted to be connected to a secondary side ground; 8. The isolated converter of claim 7, wherein a first interconnection of the first Y capacitor and the second capacitor to the secondary side ground is adapted to provide a signal indicative of a frequency of the AC voltage of the input power source.

15. 15. The isolated converter of claim 1, further comprising a rectifier between the input and the primary winding, a capacitor across the input of the rectifier, and a capacitor across the output of the rectifier, the third capacitor being connected to the input before the rectifier, and the primary side ground being at a negative output terminal of the rectifier.

16. 16. An LED driver comprising an isolation converter according to any one of claims 1 to 15, the isolation converter including an input for connection to an external power supply and an output for connection to an LED load.

17. 17. A lighting device comprising the LED driver of claim 16 and the LED load connected to the LED driver.

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