CN110167227B

CN110167227B - Open-circuit protection circuit, power supply circuit, open-circuit protection method and lighting device

Info

Publication number: CN110167227B
Application number: CN201810152315.6A
Authority: CN
Inventors: 邹昌刚
Original assignee: Panasonic Intellectual Property Management Co Ltd
Current assignee: Panasonic Intellectual Property Management Co Ltd
Priority date: 2018-02-14
Filing date: 2018-02-14
Publication date: 2022-09-09
Anticipated expiration: 2038-02-14
Also published as: CN110167227A

Abstract

The invention relates to an open circuit protection circuit, an open circuit protection method, a power supply circuit and a lighting device. The open-circuit protection circuit is used in a power supply circuit with an LED load module and a switch element, the open-circuit protection circuit comprises a control circuit and a Vf spike level detector for detecting the open-circuit condition of the LED load module, the Vf spike level detector comprises a transistor, a clamping element and a first resistor, an emitter of the transistor is connected with the LED load module, a collector of the transistor is connected with a GND terminal of the control circuit through the first resistor and a second resistor and is connected with a DIM terminal of the control circuit through a connecting point of the first resistor and the second resistor, a base of the transistor is connected with a cathode of the clamping element, and a positive pole of the clamping element is connected with the GND terminal of the control circuit; the switching element is connected to an OUT terminal of the control circuit. The invention can reduce the probability of damaging the LED load and the control circuit in the power supply circuit even when the LED load module is in poor contact, reduces the circuit load and can be effectively used for the daily maintenance of the lighting device.

Description

Open-circuit protection circuit, power supply circuit, open-circuit protection method and lighting device

Technical Field

The invention relates to an open circuit protection circuit, a power supply circuit and an open circuit protection method. The open circuit protection circuit, the power supply circuit and the open circuit protection method are particularly suitable for lighting devices comprising Light Emitting Diodes (LEDs).

Background

Currently, it is a common practice to integrate a load open circuit protection circuit portion into a control module of a lighting device, so that an LED power conversion device of the lighting device has an open circuit protection function when an LED is detached or damaged.

However, there are still many LED power conversion devices for lighting devices in the industry, which do not have an output open circuit protection function. Fig. 1(a) shows a single-winding connection circuit of a transformer without an open-circuit protection function, the transformer is in a single-winding mode, and has no detection winding and no Vf spike voltage detector, therefore, even if the LED load is open, the open signal cannot be detected, and therefore the SW switch section cannot be stopped, fig. 1(b) shows a transformer winding same phase access method without open circuit protection function, which adopts a transformer winding same phase access circuit, even if the LED load is open, the open signal cannot be detected, so that the SW switch section cannot be stopped, fig. 1(c) shows an inter-winding anti-phase connection method of a transformer without an open circuit protection function, which adopts an inter-winding anti-phase winding method of a transformer, but cannot transmit a detection signal to the SW switch block in real time, even if the LED load is open, the abnormality cannot be detected, and therefore the SW switch member cannot be stopped. The schemes of fig. 1(a) -1 (c) do not take into account that the LED power conversion device usually supplies the set current to the LED load, and the LED load can clamp the load voltage just, so the voltage applied across the load by the power conversion device is safe, however, once the load is opened, the circuit will continue to supply the set current to the LED load, and the voltage at the output port (across the load) rises abnormally due to the absence of clamping action of the LED, the output capacitor is always in a charged state, and there is no charge leakage path, the voltage may become very high, and thus the voltage at the output terminal may become very high, which is potentially dangerous and may cause damage to the electronic components. It becomes no longer safe. On one hand, the faults of the LED power converter can be further expanded, so that internal components are damaged, and finally the faults are invalid; on the other hand, when the LED load is momentarily connected to the output port of the LED power converter again, the LED load may be broken down by an abnormally high voltage.

Disclosure of Invention

In view of the above-mentioned problems, an object of the present invention is to provide a simple circuit configuration to be superimposed on a control circuit of a conventional LED power conversion device not having an output open circuit protection function, to provide the control circuit with the open circuit protection function, and to extend the service lives of the control circuit of the LED power conversion device and the lighting device at a low cost.

In one aspect, the present invention provides an open circuit protection circuit for use in a power supply circuit having an LED load module and a switching element, the open circuit protection circuit comprising: the open circuit protection circuit comprises a control circuit and a Vf spike level detector for detecting the open circuit condition of the LED load module, wherein the Vf spike level detector comprises a transistor (Q1), a clamping element and a first resistor (R3), an emitter of the transistor (Q1) is connected with the LED load module, a collector of the transistor is connected with a GND terminal of the control circuit through the first resistor (R3) and a second resistor (R4) and is connected with a DIM terminal of the control circuit through a connecting point of the first resistor (R3) and the second resistor (R4), a base of the transistor is connected with a cathode of the clamping element, and an anode of the clamping element is connected with the GND terminal of the control circuit; the switching element is connected to the OUT terminal of the control circuit.

Another aspect of the present invention provides an open circuit protection circuit for use in a power supply circuit having an LED load module and a switching element, the open circuit protection circuit comprising: the open-circuit protection circuit comprises a control circuit and a Vf spike level detector for detecting the open-circuit condition of the LED load module, wherein the Vf spike level detector comprises a transistor (Q1), a clamping element and a first resistor (R3), an emitter of the transistor (Q1) is connected to a VCC terminal of the control circuit, a collector of the transistor is connected with a DIM terminal of the control circuit through the first resistor (R3) and is connected with a GND terminal of the control circuit through the first resistor (R3) and a second resistor (R4), a base of the transistor is connected with a cathode of the clamping element, and an anode of the clamping element is connected with the GND terminal of the control circuit; the switching element is connected to the OUT terminal of the control circuit.

Further, the power supply circuit further comprises a first voltage supply circuit for supplying power to the LED load module, the Vf spike level detector detects a voltage state of the first voltage supply circuit, the control circuit controls the switching element to normally supply power to the first voltage supply circuit if the voltage does not exceed a first threshold, and the control circuit controls the switching element to turn off and stop supplying power to the first voltage supply circuit if the voltage exceeds the first threshold, and the control circuit controls the switching element to turn on and off by changing a voltage applied to a gate of the switching element.

Further, the power supply circuit further includes a first voltage supply circuit for supplying power to the LED load module, and a second voltage supply circuit for supplying power to a VCC terminal of the control circuit, the Vf spike level detector detects a voltage state of the second voltage supply circuit, the control circuit controls the switching element to normally supply power to the first voltage supply circuit if the voltage does not exceed a second threshold, and controls the switching element to turn off to stop supplying power to the first voltage supply circuit if the voltage exceeds the second threshold, and the control circuit controls the switching element to turn on and off by changing a voltage applied to a gate of the switching element.

Further, the power supply circuit further comprises a transformer, and a primary coil and a secondary coil of the transformer are reverse windings.

Further, the transistor (Q1) is a PNP transistor, the clamping element is a zener diode, and the first threshold value is a normal clamping value of the clamping element.

Another aspect of the present invention provides a power supply circuit, including: the open circuit protection circuit, the LED load module and the switch element are provided.

Further, the power supply circuit further includes: an alternating current power supply; a rectifier filter circuit that rectifies alternating current supplied from the alternating current power supply; a transformer including a primary coil and a secondary coil; a first voltage supply circuit that supplies a voltage between both ends of the primary coil to the LED load module; and a second voltage supply circuit configured to supply a voltage induced in the secondary coil to a VCC terminal of the control circuit when the switching element is in an on state.

Further, the rectification filter circuit comprises a rectification circuit, a first capacitor (C3) connected between the output ends of the rectification circuit, and a third resistor (R7) connected between the rectification circuit (DB1) and the alternating current power supply; the first voltage supply circuit comprises a first diode (D2) and a second capacitor (C2) which are connected in series between two ends of a primary coil, and a fifth resistor (R5) which is connected with the second capacitor (C2) in parallel, wherein the positive pole of the first diode (D2) is connected with the connection point between the primary coil and a switch element, the negative pole of the first diode is connected with the second capacitor (C2), and two ends of the second capacitor (C2) are connected with two ends of an LED load module; the second voltage supply circuit includes a third capacitor (C1) connected between the VCC terminal of the control circuit and the output terminal on the low potential side of the rectifying/smoothing circuit, and a second diode (D1) having a positive electrode connected to one end side of the secondary coil of the transformer via a sixth resistor (R1) and a negative electrode connected to the VCC terminal of the control circuit, and the other end of the secondary coil is connected to the GND terminal of the control circuit.

Another aspect of the present invention provides an open protection method for an open protection circuit, including the steps of: detecting whether the LED load module is open-circuited; when the LED load module is not detected to have the open-circuit fault, the control circuit controls the switch element to normally supply power to the first voltage supply circuit in the power supply circuit, and if the LED load module is detected to have the open-circuit fault, the control circuit controls the switch element to stop normally supplying power to the first voltage supply circuit in the power supply circuit.

Another aspect of the present invention provides an open circuit protection circuit for a power supply circuit having an LED load module, an inductor (T2), and a VCC power supply module, wherein: the open-circuit protection circuit comprises a control circuit and a Vf spike level detector for detecting the open-circuit condition of the LED load module, wherein the Vf spike level detector comprises a transistor (Q2) and a clamping element (VT), an emitter of the transistor is connected to a GND terminal of the control circuit, a collector of the transistor is connected with a COMP terminal of the control circuit, a base of the transistor is connected with an anode of the clamping element, a cathode of the clamping element is connected with a connection point of an inductor and a VCC power module, and the other end of the inductor supplies power to a VCC terminal of the control circuit through the VCC power module; the control circuit includes an internal switching element.

Further, the power supply circuit further comprises a voltage supply circuit for supplying power to the LED load module, the Vf spike level detector detects a voltage state of the voltage supply circuit, if the voltage does not exceed a first threshold, the control module controls the internal switching element to normally supply power to the voltage supply circuit, and if the voltage exceeds the first threshold, the control circuit controls the internal switching element to be turned off to stop supplying power to the voltage supply circuit.

Furthermore, the open-circuit protection circuit also comprises a current detection unit connected between the inductor and a CS terminal of the control circuit, the control circuit detects the state of the Vf spike level detector according to the voltage of the COMP terminal, and controls the power supply output through the internal switch element by combining the state of the current detection unit.

Furthermore, the power supply circuit further comprises an electronic switch flicker prevention unit and a shaping filter circuit, wherein two ends of the electronic switch flicker prevention unit are respectively connected with the output end of the shaping filter circuit, and the controlled end of the electronic switch flicker prevention unit is connected with the connection point of the inductor and the LED load module.

Further, the transistor is an NPN transistor, the clamping element is a zener diode, and the first threshold is a normal clamping value of the clamping element; and/or the inductor is a tapped inductor, and one end of the VCC power supply module and the clamping element is connected to the center tap of the inductor.

Another aspect of the present invention provides a power supply circuit, including: the open circuit protection circuit and the LED load module are provided.

Further, the power supply circuit is characterized by further comprising: an alternating current power supply; a rectifier filter circuit that rectifies alternating current supplied from the alternating current power supply; the inductor is used for supplying power to a VCC terminal of the control circuit and the LED load module; a voltage supply circuit supplying a voltage generated by the inductor to the LED load module; and/or, an electronic switch flicker prevention unit for preventing abnormal flicker of the LED load module.

Further, the rectification filter circuit comprises a rectification circuit, an LC filter and a third capacitor (C3) which are connected between the output ends of the rectification circuit, and a third resistor (R7) which is connected between the rectification circuit and the alternating current power supply, wherein the LC filter and the third capacitor are connected in parallel; and/or the voltage supply circuit comprises a fourth capacitor (C4) and a fifth resistor (R9) which are respectively connected with the LED load module in parallel; and/or two ends of the electronic switch flicker prevention unit are respectively connected with the output end of the shaping filter circuit, and the controlled end of the electronic switch flicker prevention unit is connected with the connection point of the inductor and the LED load module.

Another aspect of the present invention provides an open circuit protection method for an open circuit protection circuit, including the steps of: detecting whether the LED load module is open-circuited; when the LED load module is not detected to have an open-circuit fault, the control module controls the internal switching element to normally supply power to the voltage supply circuit in the power supply circuit, and if the LED load module is detected to have the open-circuit fault, the control module controls the internal switching element to stop normally supplying power to the voltage supply circuit in the power supply circuit.

Another aspect of the present invention is to provide a lighting device, wherein the open circuit protection circuit or the power supply circuit is used as a control unit of the lighting device.

According to the scheme of the invention, the probability of damaging the LED load and the control circuit in the power supply circuit can be reduced even when the LED load module is in poor contact, the circuit load is reduced, and the LED load module can be effectively used for daily maintenance of the lighting device.

The foregoing description is only an overview of the technical solutions of the present invention, and in order to make the technical solutions of the present invention more clearly understood and to implement them in accordance with the contents of the description, the following detailed description is given with reference to the preferred embodiments of the present invention and the accompanying drawings.

Drawings

FIG. 1(a) is a prior art single winding connection circuit of a transformer without open circuit protection function;

fig. 1(b) is a connection circuit of the same phase connection mode of a transformer winding without an open circuit protection function in the prior art;

fig. 1(c) is a connection circuit of a reverse phase connection mode between transformer windings without an open circuit protection function in the prior art;

FIG. 2 is a protection circuit outputting open sampling points;

FIG. 3 is a protection circuit for the reverse sampling of the inductor auxiliary winding;

FIG. 4 is a protection circuit for inductive single winding inductive sampling;

FIG. 5 is a circuit diagram of a power supply circuit according to an embodiment of the invention;

FIG. 6 is a circuit diagram of a power supply circuit according to an embodiment of the present invention;

FIG. 7 is a circuit diagram of a power supply circuit according to an embodiment of the invention;

FIG. 8 is a schematic diagram of an electronic switch flicker prevention unit;

fig. 9 is a schematic diagram of a tapped inductor.

Detailed Description

Because the end voltage of the output end LED load module is increased inevitably after the output end LED load module is opened, abnormal voltage sampling can be carried out through various ways, and only the proportional relation between the voltage of a sampling point and the voltage of an output port is required (the direct proportional relation or the inverse proportional relation is not limited). Namely, the output voltage is abnormally increased, the voltage of the sampling point is also abnormally increased or decreased, and only a certain change rule is met and circuit judgment is easy to realize. Fig. 2 is a protection circuit for outputting an open-circuit sampling point, as shown in fig. 2, in the protection circuit of this scheme, one end of the sampling point is an output terminal positive terminal, and the other end is a ground terminal; fig. 3 is a protection circuit for reverse phase sampling of an inductance auxiliary winding, which is a further optimization of the scheme shown in fig. 2, and the scheme is that Lp and Ls windings in a transformer winding are connected into a circuit in a reverse phase mode and are set according to a certain turn ratio; fig. 4 is a protection circuit for inductor single winding inductor sampling, as shown in fig. 4, in the protection circuit of this scheme, one end of a sampling point is one side of an inductor, and the other end is the other side of the inductor.

The invention further arranges a Vf spike level detector, the signal collected from the sampling point is processed by the Vf spike level detection circuit, and then output by high level or low level, and transmitted to the control module of the switch component through a certain path, thus realizing the function of LED load open circuit abnormal protection.

Next, the power supply protection circuit, the power supply circuit, and the lighting device according to the present invention will be further described with reference to specific examples.

Implementation mode one

Fig. 5 shows a circuit diagram of the power supply circuit according to the present embodiment.

The power supply circuit comprises a rectifying filter circuit, a transformer T1, a switching element 4, a first voltage supply circuit, a second voltage supply circuit, a Vf spike level detector serving as a protection circuit, an LED load module 2 and a control circuit (control module) U1.

The LED load module 2 is obtained by connecting a plurality of LEDs in series/parallel. When power is supplied from the ac power supply 1 to each LED load via the power supply circuit, each LED load is turned on. The LED load module may be formed by connecting a plurality of series-connected bodies in which a plurality of LEDs are connected in series in parallel, or may be formed by connecting a plurality of parallel-connected bodies in which a plurality of LEDs are connected in parallel in series.

The rectifying-smoothing circuit includes a rectifying circuit DB1, a capacitor C3 connected between the output terminals of the rectifying circuit DB1, and a resistor R7 connected between the rectifying circuit DB1 and the ac power supply 1. The voltage across the capacitor C3 is output as the output voltage of the rectifying/smoothing circuit. The rectifying circuit DB1 may be a diode or a bridge.

One end of the primary winding Lp of the transformer T1 is connected to the output terminal on the high potential side of the rectifying/smoothing circuit, and the other end is connected to the drain of the switching element 4. The primary coil Lp supplies power to the LED load module together with the switching element 4 and the first voltage supply circuit. In addition, the secondary coil Ls is connected to a second voltage supply circuit.

The switching element 4 is an N-channel MOS transistor, and has a gate G electrically connected to the OUT terminal of the control circuit U1, a drain D connected to the primary winding Lp of the transformer T1, and a source S connected to the low-potential-side output terminal of the rectifying/smoothing circuit via a resistor R6. The resistor R6 is used to limit the current flowing through the switching element 4 when the switching element 4 is in the on state.

The first voltage supply circuit supplies the voltage across the primary coil Lp to the LED load block via the output terminals TL1, TL 2. The first voltage supply circuit includes a diode D2 and an electrolytic capacitor C2 connected in series between both ends of the primary coil Lp, and a resistor R5 connected in parallel to the electrolytic capacitor C2. The diode D2 has a positive electrode connected to a connection point between the primary coil Lp and the switching element 4, and a negative electrode connected to the electrolytic capacitor C2. Both ends of the electrolytic capacitor C2 are connected to output terminals TL1 and TL 2. The pulsating current voltage generated across the primary coil Lp is smoothed by the electrolytic capacitor C2 and then output from the output terminals TL1 and TL 2.

The second voltage supply circuit supplies the voltage induced in the secondary coil Ls to the power supply terminal VCC. The second voltage supply circuit includes a capacitor C1 connected between the power supply terminal VCC of the control circuit U1 and the low-potential-side output terminal of the rectifier filter circuit, and a diode D1 having a positive electrode connected to one end side of the secondary coil Ls (voltage supply coil Ls) of the transformer T1 via a resistor R1, and a negative electrode connected to the power supply terminal VCC of the control circuit U1. The other end of the secondary coil Ls is connected to a GND terminal of the control circuit U1.

The Vf spike level detector is composed of a PNP transistor Q1, a clamping element (or clamping circuit) VT, and a resistor R3, and is used for detecting a rise in voltage when the LED load module is open and preventing an excessive voltage from being applied to the power supply terminal VCC of the control circuit U1. An emitter E of the transistor Q1 is connected to a connection point of the diode D2, the electrolytic capacitor C2, the resistor R5, and the LED load module, a collector C is connected to a GND terminal of the control circuit U1 through the resistor R3 and a dimming external resistor R4 of the control circuit U1, a DIM terminal of the control circuit U1 through a connection point of the resistors R3 and R4, a base B is connected to a negative electrode of the clamp element VT, and a positive electrode of the clamp element is connected to a GND terminal of the control circuit. The resistor R8 is connected to the VCC terminal and the GND terminal of the control circuit, respectively. In a preferred embodiment, the clamping element is a zener diode.

The control circuit U1 controls the switching element 4 to be turned on and off by changing a voltage applied to the gate of the switching element 4. The components making up the control circuit U1 may be embedded in an IC package.

The Vf spike level detector detects the voltage state of the first voltage supply circuit in real time, if the voltage does not exceed the normal clamping value of the clamping device VT, the DIM terminal of the control circuit U1 is in a low level state, the control module U1 controls the switching device 4 to normally provide voltage to the first voltage supply circuit, and at this time, the DIM terminal of the control module U1 can normally receive the DIM dimming signal. If the voltage exceeds the normal clamping value of the clamping device VT, the DIM terminal of the control circuit U1 is in a high level state, and the internal processing of the control circuit U1 controls the switching element 4 to be turned off, so as to disconnect the output of the transformer T1 to the output terminals TL1 and TL2, thereby realizing the protection function when the load is open-circuited.

The specific working process is as follows:

when the LED load is normally connected, the AC power supply 1 supplies power to the primary winding Lp of the transformer T1 through the rectifier filter circuit, the secondary winding Ls of the transformer T1 supplies working voltage to the control circuit U1 through the resistor R1 and the diode D1, a Vf spike level detector as a component of the protection circuit detects the voltage state of the first voltage supply circuit in real time, if the voltage does not exceed the normal clamping value of the clamping element VT, a current path passing through the clamping element VT is not generated, the BE junction and the BC junction of the transistor Q1 are both in an off state, the DIM terminal of the control circuit U1 is connected with the GND terminal of the control circuit U1 through the resistor R4 and is in a low level state, the DIM terminal of the U1 can normally receive DIM dimming signals, the control module U1 controls the switching element 4 to BE in a normal working state, and normally supplies voltage to the first voltage supply circuit (TL1, TL 52, TL 3552, TL, and the controller U4 controls the current source to BE connected to the control circuit U1, TL2), at this time, assume that the voltage between the output terminals TL1, TL2 is a volts, e.g., a is about 207 Vpk.

During abnormal operation (i.e. there is an LED open circuit error in the LED load module), since there is no discharge loop after the load is open, the transformer T1 reverses instantaneously, resulting in a voltage increase at the output terminals TL1 and TL2, and when it is assumed that the voltage between the output terminals TL1 and TL2 is a volt during normal operation, the voltage between the output terminals TL1 and TL2 during abnormal operation is ≧ YYY% × a volt (the peak voltage value is the sum of the bus voltage, the primary winding voltage, and the secondary winding reflected voltage), for example, 150% × a (v) or more. Depending on the turns ratio, the value of YYY% will vary, and when a is about 207Vpk, YYY% a is about 308 Vpk. At this time, the abnormal voltage exceeds the normal clamping value, P, of the clamping element VTThe BE junction of NP transistor Q1 turns on, the CE junction also turns on, and current I _CE The current flowing through the resistors R3 and R4 pulls the level of the DIM terminal of the control circuit U1 high, and the control circuit U1 controls the switching element 4 to be in an off state, so that the LED driving circuit has no output, and a protection function is realized when the load is open.

Second embodiment

In view of the fact that the clamp device VT or the transistor Q1 in the first embodiment is required to have a high withstand voltage and is easily damaged, resulting in an increase in cost, the second embodiment is an improvement on the circuit of the first embodiment.

Fig. 6 shows a circuit diagram of the power supply circuit according to the present embodiment. The circuit follows the same reference numerals as before.

The power supply circuit includes circuit elements similar to those of the first embodiment in the rectifier filter circuit, the transformer T1, the switching element 4, the first voltage supply circuit, and the second voltage supply

The circuit, Vf spike level detector as a protection circuit, LED load module 2, and control circuit U1.

The rectifying-smoothing circuit includes a rectifying circuit DB1, a capacitor C3 connected between the output terminals of the rectifying circuit DB1, and a resistor R7 connected between the rectifying circuit DB1 and the ac power supply 1. The voltage across the capacitor C3 is output as the output voltage of the rectifying/smoothing circuit.

One end of the primary winding Np of the transformer T1 is connected to the output terminal on the high potential side of the rectifying/smoothing circuit, and the other end is connected to the drain of the switching element 4. The primary coil Np supplies power to the LED load module together with the switching element 4 and the first power supply circuit. In addition, the secondary coil Ns is connected to the second power supply circuit. The primary winding Np and the secondary winding Ns of the transformer T1 are arranged in opposite phases, and they are set according to a certain turn ratio. The output voltage Uout sample is thus sampled by the secondary winding Ns of the transformer T1, and the sampled voltage Us varies in direct proportion to the output voltage Uout between the output terminals TL1, TL2, Us ═ Ns/Np × Uout, where Ns/Np < 1. The Ns/Np proportional relation can be reasonably set, so that the normal power supply of the control circuit U1 can be ensured.

The switching element 4 is an N-channel MOS transistor, and has a gate G electrically connected to the OUT terminal of the control circuit U1, a drain D connected to the primary winding Np of the transformer T1, and a source S connected to the low-potential-side output terminal of the rectifying/smoothing circuit via a resistor R6. The resistor R6 is used to limit the current flowing through the switching element 4 when the switching element 4 is in the on state.

The first voltage supply circuit supplies a voltage between both ends of the primary coil Np to the LED load module via the output terminals TL1, TL 2. The first voltage supply circuit includes a diode D2 and an electrolytic capacitor C2 connected in series between both ends of the primary coil Np, and a resistor R5 connected in parallel to the electrolytic capacitor C2. The diode D2 has a positive electrode connected to a connection point between the primary coil Lp and the switching element 4, and a negative electrode connected to the electrolytic capacitor C2. Both ends of the electrolytic capacitor C2 are connected to output terminals TL1 and TL 2. The pulsating current voltage generated across the primary coil Np is smoothed by the electrolytic capacitor C2 and then output from the output terminals TL1 and TL 2.

The second voltage supply circuit supplies the voltage induced in the secondary coil Ns to the power supply terminal VCC. The second voltage supply circuit includes a capacitor C1 connected between the power supply terminal VCC of the control circuit U1 and the low-potential-side output terminal of the rectifier filter circuit, and a diode D1 having a positive electrode connected to one end side of the secondary coil Ns of the transformer T1 via a resistor R1 and a negative electrode connected to the power supply terminal VCC of the control circuit U1. The other end of the secondary coil Ns is connected to the GND terminal of the control circuit U1.

The Vf spike level detector is composed of a PNP transistor Q1, a clamping element (or clamping circuit, which is a zener diode in a preferred embodiment) VT, and resistors R2, R3, and is used for detecting a rise in voltage when the LED load module is open and preventing an excessive voltage from being applied to the power supply terminal VCC of the control circuit U1. The transistor Q1 has an emitter E connected to the power supply terminal VCC of the control circuit U1, a collector C connected to the DIM terminal of the control circuit U1 via a resistor R3, a GND terminal of the control circuit U1 via resistors R3 and R4, a base B connected to the negative electrode of the clamp element VT, and a positive electrode connected to the GND terminal of the control circuit U1 via a resistor R2.

The Vf spike level detector detects the voltage status of the second voltage supply circuit in real time, and if the voltage does not exceed the normal clamping value of the clamping device VT, the control module U1 controls the switching device 4 to normally provide the voltage to the first voltage supply circuit, and at this time, the DIM terminal of the control module U1 can normally receive the DIM dimming signal. If the voltage exceeds the normal clamping value of the clamping element VT, the DIM terminal of the control circuit U1 is in a high level state, and the control circuit U1 performs internal processing to control the switching element 4 to be turned off, so as to turn off the output of the transformer T1 to the TL1 and TL2, thereby realizing the protection function when the load is open-circuited.

The specific working process is as follows:

when the LED light-emitting diode (LED) load works normally (namely, the LED load is connected normally), the alternating current power supply 1 supplies power to the primary winding Np of the transformer T1 through the rectifier filter circuit, the secondary winding Ns of the transformer T1 supplies working voltage to the control circuit U1 through the resistor R1 and the diode D1, a Vf spike level detector which is a component of the protection circuit detects the voltage state of the second voltage supply circuit in real time, if the voltage does not exceed the normal clamping value of the clamping element VT, a current path passing through the clamping element VT is not generated, the BE junction and the BC junction of the transistor Q1 are both in an off state, the DIM terminal of the control circuit U1 is connected with the GND terminal of the control circuit U1 through the resistor R4, and at the moment, the DIM terminal of the control module U1 can normally receive DIM dimming signals. The control module U1 controls the switching element 4 to be in a normal operating state to normally supply the voltage Uout to the first voltage supply circuit, which assumes that the output voltage of the first voltage supply circuit is H volts. For example, H is about 207 Vpk.

When the load is in abnormal operation (namely the LED load module has an LED open circuit error), the first voltage supply circuit is increased to the ground voltage because the circuit has no discharge loop after the load is opened, and the abnormal operation is performed under the condition that the ground voltage of the first voltage supply circuit is H V during normal operationIn operation, the first voltage supply circuit is connected to a ground voltage ≧ YYY% × H volts (the peak voltage is the sum of the bus voltage, the primary winding voltage, and the secondary winding reflected voltage), for example, 150% × H (v) or more, the value of yy% varies depending on the turn ratio, the sampled voltage Us varies in direct proportion to Uout, Us ═ Ns/Np) Uout, and yy% × H is about 308Vpk when H is about 207 Vpk. At this time, the abnormal sampling voltage Us causes the two ends of the clamping element VT to exceed the normal clamping value, the BE junction of the PNP transistor Q1 is conducted, the CE junction is conducted along with the conduction, and the current I _CE The level of the DIM terminal of the control circuit U1 is pulled high by the flow resistors R3 and R4, and the control circuit U1 controls the switching element 4 to be in an off state, thereby disconnecting the output of the transformer T1 to the TL1 and TL2 ports, and realizing a protection function when the load is open.

Third embodiment

Fig. 7 shows a circuit diagram of the power supply circuit according to the present embodiment. The same circuit elements in this circuit as in the first embodiment have been given the same reference numerals as before.

The power supply circuit comprises a rectifying filter circuit, an electronic switch flicker prevention unit 9, a control circuit U1, a current detection unit 7, a VCC power supply module 8, an inductor T2, a Vf spike level detector serving as a protection circuit, an LED load module 2 and a voltage supply circuit.

The rectifying and smoothing circuit includes a rectifying circuit DB1, an LC filter 3 and a capacitor C3 connected between the output terminals of the rectifying circuit DB1, and a resistor R7 connected between the rectifying circuit DB1 and the ac power supply 1, and the LC filter 3 and the capacitor C3 are connected in parallel. The alternating current power supply is rectified by the rectifying circuit DB1, filtered by the LC filter 3 and then output to the whole power supply circuit.

The electronic switch flicker prevention unit 9 is connected to the output terminal of the LC filter 3, and the controlled terminal 5 thereof is connected to the terminal of the inductor T2 connected to the LED load module 2. The electronic switch flicker prevention unit 9 is grounded at one end connected to the low potential side of the rectification filter circuit. The current required for the normal operation of the electronic switch is provided by selecting the resistor Rd with a suitable resistance value. The electronic switch flicker prevention unit 9 is configured to prevent abnormal flicker of the LED load module 2 caused by a weak current flowing through the electronic switch in the off state.

Fig. 8 is a schematic diagram of an electronic switch flicker prevention unit. The electronic switch flicker prevention unit includes resistors Ra, Rb, Rc, Rd, and transistors Q3, Q4. The collector of the transistor Q4 is connected with the resistor Rd, the emitter of the transistor Q4 is connected with the emitter of the transistor Q3 and the resistor Rb and then is grounded, the base of the transistor Q4 is connected with the connection point of the resistor Rc and the collector of the transistor Q3, the base of the transistor Q3 is connected with the connection point of the resistors Ra and Rb, the other ends of the resistors Rd and Rc are connected with the other output end of the LC filter, and the resistor Ra is connected with one end of the inductor T2 connected with the LED load module 2.

Whether the voltage at two ends of the LED load module is used as a judgment condition for the conduction of the transistor Q4 switch or not is used, when the electronic switch is in a standby state, the voltage at two ends of the LED load module is low, the transistor Q3 is cut off, the transistor Q4 is conducted, and the branch of the resistor Rd and the electronic switch form a loop, so that the LED load module is prevented from repeatedly flickering an LED bulb; after the electronic switch is normally turned on, the voltage at two ends of the LED load module is established, the transistor Q3 is turned on, the transistor Q4 is turned off, the resistor Rd branch and the electronic switch cannot form a loop, the electronic loop and the LED load form a loop, and at the moment, the Rd does not consume electric energy any more. One end of the coil of the inductor T2 is connected to one end of the current detection unit 7, and the other end is connected to a connection point between the voltage supply circuit and the output terminal TL1, and at this end, power is supplied to the VCC terminal of the control circuit U1 through the VCC power supply module 8. The current detection unit can be implemented by using two resistors connected in parallel.

One end of the VCC power supply module 8 is connected to a connection point between the inductor T2 and the voltage supply circuit, and the other end is connected to a VCC terminal of the control module U1, so as to provide a working voltage for the control module U1 in a normal operating state.

And a voltage supply circuit for supplying a voltage between output terminals thereof to the LED load module via output terminals TL1 and TL 2. The voltage supply circuit includes an electrolytic capacitor C4 connected in parallel to the output terminals TL1 and TL2, and a resistor R9 connected in parallel to the electrolytic capacitor C4. One end of the electrolytic capacitor C4 and one end of the resistor R9 are connected with the anode of the LED load module, the other end of the resistor R9 are connected with the cathode of the LED load module and then grounded, and the pulsating current voltage generated at one end of the inductor T2 is smoothed by the electrolytic capacitor C4 and then is output from the output terminals TL1 and TL 2.

The Vf spike level detector is composed of an NPN transistor Q2, a clamping element (or clamping circuit, which is a zener diode in a preferred embodiment) VT, and a resistor R3, and is used for detecting a voltage rise when the LED load module is open-circuited and preventing an excessive voltage from being applied to the power supply terminal VCC of the control circuit U1. The emitter E of the transistor Q2 is connected to the GND terminal of the control circuit U1, the collector C is connected to the COMP terminal of the control circuit U1, the base B is connected to the positive electrode of the clamp element VT, and the negative electrode of the clamp element VT is connected to the connection point of the inductor T2 and the VCC power supply. The base of the transistor Q2 is connected to the connection point between the clamp element VT and the resistor R3, and the other end of the resistor R3 is connected to the emitter of the transistor Q2 and to the GND terminal of the control circuit U1.

The Vf spike level detector detects the voltage state of the voltage supply circuit in real time, if the voltage does not exceed the normal clamping value of the clamping element VT, the power supply circuit normally provides the voltage Uout under the control of the current detection unit 7 and the control module U1, and if the voltage exceeds the normal clamping value of the clamping element VT, the output of the inductor T2 to the LED load module is cut off under the control of the current detection unit and the control module U1, so that the protection function when the load is open-circuited is realized.

The control circuit U1 includes an internal switch (not shown). The D terminal of the control circuit U1 is connected with the rectifying filter circuit and the electronic switch flicker prevention unit, the VCC terminal is connected with one end of the inductor through a VCC power supply and is connected with the voltage supply module and the voltage output terminal TL1, the CS terminal is connected with the current detection module and is reversely grounded through the freewheeling diode D3, when the internal switch of the control circuit U1 is turned off, the inductive potential of the inductor T2 is reversed, and the reverse potential continues to provide a current path for the reverse potential through the freewheeling diode D3, so that power is supplied to the LED load module.

The control circuit U1 is used to monitor the Vf spike level detector status according to the different COMP terminal voltages, and assist the current detector status at the CS terminal to control the power output via the internal switch.

The control circuit U1 controls the output by controlling the on and off of internal switching elements. The components making up the control circuit U1 may be embedded in one IC package.

The current detection unit 7 has one end connected to the CS end of the control circuit U1, and the other end connected to one end of the inductor T2 and to the GND terminal of the control circuit U1. The power supply current to the LED load module is detected in real time and fed back to the control circuit U1.

The specific working process is as follows:

during normal operation (i.e. normal access of the LED load module), the ac power supply 1 supplies power to the output terminals TL1 and TL2 through the rectifier filter circuit, the control circuit U1, the current detection module 7, and the inductor T2, and the Vf spike level detector as the protection circuit detects the voltage state of the voltage supply circuit in real time, if the voltage does not exceed the normal clamped value of the clamping element VT, the BE junction and BC junction of the transistor Q2 are both in an off state, and the COMP terminal of the control circuit U1 is disconnected from the GND terminal, so that the COMP terminal is in a high level state, and under the control of the current detection unit and the control module U1, the switching element 4 is in a normal operation state, and normally supplies the output voltage Uout, and at this time, it is assumed that the voltage between the output terminals TL1 and TL2 is a volt.

During abnormal operation (namely, there is an LED open circuit error in the LED load module), since there is no discharge loop after the load is open circuit, the inductance T2 is instantaneously reversed, so that the voltages of the output terminals TL1 and TL2 are abnormally increased, under the assumption that the voltage between the output terminals TL1 and TL2 is a v during normal operation, the voltage between the output terminals TL1 and TL2 during abnormal operation is ≧ yy% × a v, for example, 150% × a (v) or more, at this time, the abnormal voltage exceeds the normal clamping value of the clamping element VT, the BE junction of the transistor Q2 is turned on, the CE junction is also turned on along with the same, and the current I is turned on _CE Directly flows into the ground terminal of the control circuit U1, the COMP terminal of the control circuit U1 is connected with the GND terminal, and finally the COMP terminal (the compensation port of the internal error amplifier) is pulled to be low level L, so that the COMP terminal is in a low level state and is controlled by the current detection unit and the control module U1The output of the disconnection inductor T2 to the LED load module is controlled, and the protection function when the load is open-circuited is realized.

Further, the inductor T2 may be center-tapped, and as shown in fig. 9, one end of the VCC power supply module 8 and the clamping element VT of the Vf spike level detector may be connected to the center-tapped inductor T2.

When the abnormal operation is performed (i.e. there is an LED open circuit error in the LED load module), since there is no discharge loop after the load is open circuit, the voltage of the output terminals TL1 and TL2 is abnormally increased due to the instant reverse of the inductance T2, and under the condition that the voltage between the output terminals TL1 and TL2 is assumed to BE a v during the normal operation, the voltage between the output terminals TL1 and TL2 during the abnormal operation is not less than YYY% a v, for example, more than 150% a (v), the value of yy% is different according to the difference of the turns ratio of the two ends of the center tap of the inductance T2, and at this time, the abnormal voltage exceeds the normal clamping value of the clamping element VT, the BE junction of the transistor Q2 is turned on, the CE junction is also turned on, the current ICE directly flows into the ground terminal of the control circuit U1, the COMP terminal of the control circuit U1 is turned on with the GND terminal, and the COMP terminal (the internal error amplifier compensation port) is finally pulled down to a low level L, so that the COMP terminal is in a low level state, under the control of the current detection unit and the control module U1, the output of the inductor T2 to the LED load module is cut off, and the protection function when the load is open is realized.

Embodiment IV

According to a fourth embodiment of the present invention, there is also provided a lighting device, which can use the open protection circuit or the power supply circuit as described in the previous embodiments as a control section of the lighting device.

In summary, the present invention can reduce the probability of damaging the LED load and the control circuit in the power supply circuit even when the LED load module is in poor contact, reduce the circuit load, and can be effectively used for the daily maintenance of the lighting device.

It will be appreciated by those of ordinary skill in the art that in the embodiments described above, numerous technical details are set forth in order to provide a better understanding of the present application. However, the technical solutions claimed in the claims of the present application can be basically implemented without these technical details and various changes and modifications based on the above-described embodiments. Accordingly, in actual practice, various changes in form and detail may be made to the above-described embodiments without departing from the spirit and scope of the invention.

Claims

1. An open circuit protection circuit for use in a power supply circuit having an LED load module and a switching element, characterized in that:

the open circuit protection circuit comprises a control circuit and a Vf spike level detector for detecting an open circuit condition of the LED load module,

the Vf spike level detector comprises a transistor (Q1), a clamping element and a first resistor (R3), wherein an emitter of the transistor (Q1) is connected with the LED load module, a collector of the transistor is connected with a GND terminal of the control circuit through the first resistor (R3) and a second resistor (R4) and is connected with a DIM terminal of the control circuit through a connecting point of a first resistor (R3) and a second resistor (R4), a base of the transistor is connected with a negative electrode of the clamping element, and a positive electrode of the clamping element is connected with the GND terminal of the control circuit;

the switching element is connected with an OUT terminal of the control circuit, and two ends of the switching element are respectively connected with the LED load module and a GND terminal of the control circuit;

the power supply circuit also comprises a first voltage supply circuit used for supplying power to the LED load module, the Vf spike level detector detects the voltage state of the first voltage supply circuit, if the voltage does not exceed a first threshold value, the control circuit controls the switch element to normally supply power to the first voltage supply circuit, if the voltage exceeds the first threshold value, the control circuit controls the switch element to be disconnected to stop supplying power to the first voltage supply circuit,

the control circuit controls the switching element to be turned on and off by changing a voltage applied to a gate of the switching element.

2. The open-circuit protection circuit of claim 1, wherein:

the transistor (Q1) is a PNP transistor,

the clamping element is a zener diode and,

the first threshold is a normal clamping value of the clamping element.

3. An open circuit protection circuit for use in a power supply circuit having an LED load module and a switching element, characterized in that:

the Vf spike level detector comprises a transistor (Q1), a clamping element and a first resistor (R3), wherein an emitter of the transistor (Q1) is connected with a VCC terminal of the control circuit, a collector of the transistor is connected with a DIM terminal of the control circuit through the first resistor (R3), a collector of the transistor is connected with a GND terminal of the control circuit through the first resistor (R3) and a second resistor (R4), a base of the transistor is connected with a negative pole of the clamping element, and a positive pole of the clamping element is connected with a GND terminal of the control circuit;

the switching element is connected with an OUT terminal of a control circuit, and two ends of the switching element are respectively connected with the LED load module and a GND terminal of the control circuit;

the power supply circuit further comprises a first voltage supply circuit used for supplying power to the LED load module and a second voltage supply circuit used for supplying power to a VCC terminal of the control circuit, the Vf spike level detector detects the voltage state of the second voltage supply circuit, if the voltage does not exceed a second threshold value, the control circuit controls the switch element to normally supply power to the first voltage supply circuit, if the voltage exceeds the second threshold value, the control circuit controls the switch element to be disconnected, and the power supply to the first voltage supply circuit is stopped,

4. The open-circuit protection circuit according to claim 1 or 3, wherein:

the power supply circuit further comprises a transformer, and a primary coil and a secondary coil of the transformer are reverse windings.

5. A power supply circuit, comprising:

the open circuit protection circuit, the LED load module, and the switching element according to any one of claims 1 to 4.

6. The power supply circuit of claim 5, further comprising:

an alternating current power supply;

a rectifier filter circuit that rectifies the alternating current supplied from the alternating current power supply;

a transformer including a primary coil and a secondary coil;

a first voltage supply circuit that supplies a voltage between both ends of the primary coil to the LED load module;

and a second voltage supply circuit configured to supply a voltage induced in the secondary coil to a VCC terminal of the control circuit when the switching element is in an on state.

7. The power supply circuit of claim 6, wherein:

the rectification filter circuit comprises a rectification circuit, a first capacitor (C3) connected between the output ends of the rectification circuit, and a third resistor (R7) connected between the rectification circuit (DB1) and an alternating current power supply;

the first voltage supply circuit comprises a first diode (D2) and a second capacitor (C2) which are connected in series between two ends of the primary coil, and a fifth resistor (R5) which is connected with the second capacitor (C2) in parallel, wherein the anode of the first diode (D2) is connected with the connection point between the primary coil and the switch element, the cathode of the first diode is connected with the second capacitor (C2), and two ends of the second capacitor (C2) are connected with two ends of the LED load module;

the second voltage supply circuit includes a third capacitor (C1) connected between the VCC terminal of the control circuit and the output terminal on the low potential side of the rectifying/smoothing circuit, and a second diode (D1) having a positive electrode connected to one end side of the secondary coil of the transformer via a sixth resistor (R1) and a negative electrode connected to the VCC terminal of the control circuit, and the other end of the secondary coil is connected to the GND terminal of the control circuit.

8. An open protection method of the open protection circuit according to any one of claims 1 to 4, comprising the steps of:

detecting whether the LED load module is open-circuited;

when the LED load module is not detected to have open-circuit fault, the control circuit controls the switch element to normally supply power to the first voltage supply circuit in the power supply circuit,

and if the LED load module is detected to have open-circuit fault, the control circuit controls the switching element to stop normally supplying power to the first voltage supply circuit in the power supply circuit.

9. An open circuit protection circuit for use in a power supply circuit having an LED load module, an inductor (T2), a VCC power module, characterized by:

the Vf spike level detector comprises a transistor (Q2) and a clamping element (VT), wherein an emitter of the transistor is connected to a GND terminal of the control circuit, a collector of the transistor is connected with a COMP terminal of the control circuit, a base of the transistor is connected with an anode of the clamping element, a cathode of the clamping element is connected with a connection point of an inductor, an LED load module and a VCC power supply module, and the other end of the inductor is connected with a CS terminal of the control circuit through a current detection unit;

the control circuit includes an internal switching element.

10. The open-circuit protection circuit of claim 9, wherein:

the power supply circuit further comprises a voltage supply circuit used for supplying power to the LED load module, the Vf spike level detector detects the voltage state of the voltage supply circuit, if the voltage does not exceed a first threshold value, the control module controls the internal switch element to normally supply power to the voltage supply circuit, and if the voltage exceeds the first threshold value, the control circuit controls the internal switch element to be disconnected and stops supplying power to the voltage supply circuit.

11. The open circuit protection circuit of claim 10,

the control circuit detects the state of the Vf spike level detector according to the voltage of the COMP terminal, and controls the power supply output through the internal switch element in combination with the state of the current detection unit.

12. The open-circuit protection circuit of claim 11, wherein:

the power supply circuit further comprises an electronic switch flicker prevention unit and a shaping filter circuit, wherein two ends of the electronic switch flicker prevention unit are respectively connected with the output end of the shaping filter circuit, and the controlled end of the electronic switch flicker prevention unit is connected with the connection point of the inductor and the LED load module.

13. The open-circuit protection circuit of claim 12, wherein:

the transistor is an NPN transistor which is,

the clamping element is a zener diode and,

the first threshold is a normal clamping value of the clamping element;

and/or the presence of a gas in the gas,

the inductor is a tapped inductor that connects one end of the VCC power supply module and the clamping element to the inductor center tap.

14. A power supply circuit, comprising:

the open circuit protection circuit according to any one of claims 9-13, and an LED load module.

15. The power supply circuit of claim 14, further comprising:

an alternating current power supply;

the inductor is used for supplying power to a VCC terminal of the control circuit and the LED load module;

a voltage supply circuit supplying a voltage generated by the inductor to the LED load module;

and/or the presence of a gas in the gas,

and the electronic switch flicker prevention unit is used for preventing abnormal flicker of the LED load module.

16. The power supply circuit of claim 15, wherein:

the rectification filter circuit comprises a rectification circuit, an LC filter and a third capacitor (C3) which are connected between the output ends of the rectification circuit, and a third resistor (R7) which is connected between the rectification circuit and an alternating current power supply, wherein the LC filter and the third capacitor are connected in parallel;

and/or the presence of a gas in the gas,

the voltage supply circuit comprises a fourth capacitor (C4) and a fifth resistor (R9) which are respectively connected with the LED load modules in parallel;

and/or the presence of a gas in the atmosphere,

and two ends of the electronic switch flicker prevention unit are respectively connected with the output end of the shaping filter circuit, and the controlled end of the electronic switch flicker prevention unit is connected with the connection point of the inductor and the LED load module.

17. An open protection method of an open protection circuit according to any one of claims 9 to 13, comprising the steps of:

detecting whether the LED load module is open-circuited;

when the LED load module is not detected to have open-circuit fault, the control module controls the internal switching element to normally supply power to the voltage supply circuit in the power supply circuit,

and if the LED load module is detected to have open-circuit fault, the control module controls the internal switch element to stop normally supplying power to the voltage supply circuit in the power supply circuit.

18. An illumination device, characterized in that the open protection circuit according to any one of claims 1-4, 9-13 or the power supply circuit according to any one of claims 5-7, 14-16 is used as a control part of the illumination device.