CN205124089U - LED drive circuit and LED lamp - Google Patents

Abstract

The utility model provides an LED drive circuit and an LED lamp, wherein the LED drive circuit includes a rectifier, which has an input terminal and an output terminal, and the input terminal receives an AC input signal and rectifies it; the power conversion circuit, and the output terminal of the rectifier terminal connection, used to generate a constant current output to drive the LED load; the LED drive circuit also includes a frequency detection circuit, used to detect the frequency of the AC input signal; a switch circuit, the switch circuit is connected in parallel with the power conversion circuit, and the frequency The detection circuit controls the closing and opening of the switching circuit according to the frequency of the AC input signal.

Description

A kind of LED driving circuit and LED lamp

technical field

The utility model relates to an LED driving circuit and an LED lamp.

Background technique

With the development of LED technology, the luminous efficiency of lamps made of LEDs has been higher than that of traditional fluorescent lamps T8, T10 and T12. To achieve the same lumen output, the power of LED lights can be lower, so as to achieve the purpose of energy saving and emission reduction. Fluorescent lamps need ballasts to provide suitable power for them. Ballasts are mainly divided into inductive ballasts and electronic ballasts. Inductive ballasts output low-frequency AC signals, while electronic ballasts output high-frequency Frequency AC signal. Fluorescent lamps are generally located outside the lamp or inside the lamp mask, which is very convenient to replace. The ballast is generally installed inside the lamp and needs to be disassembled by tools, so it is not easy to replace.

There are already some manufacturers on the market that have introduced products to replace fluorescent lamps and LED lamps, but they are only aimed at replacing fluorescent lamps driven by magnetic ballasts or fluorescent lamps driven by electronic ballasts, and the driving circuits are also different. For example, the solution shown in Figure 1 is an LED lamp solution for replacing fluorescent lamps driven by magnetic ballasts. In Figure 1, the AC mains is powered by magnetic ballasts to output low-frequency AC voltage, and the LED lights first pass through rectifiers to realize AC and DC Transformation, the power conversion circuit is often added after the rectifier to achieve high input power factor and output constant current, so that the output can be directly connected to the LED load.

Due to the use of different drive circuits for magnetic ballasts and electronic ballasts in existing solutions, customers often need to clarify whether the fluorescent lamps to be replaced are powered by magnetic ballasts or electronic ballasts before purchasing. Once the wrong purchase is made, the LED lamp cannot be compatible with the original ballast, which will bring unnecessary trouble to the customer; at the same time, for the manufacturer, two different product types need to distinguish different production materials, which is very important for stocking. , Production, inventory and after-sales management will also bring a lot of inconvenience and increase the corresponding management costs.

Contents of the invention

In order to overcome the above technical problems, the purpose of this utility model is a new LED drive circuit and LED lamp, which can be compatible with magnetic ballasts and electronic ballasts at the same time, and can also be directly connected to commercial power input. LED lights are not only easy to install, but also bring convenience to production.

The utility model provides an LED driving circuit compatible with an inductance and an electronic ballast, comprising: a rectifier, which has an input terminal and an output terminal, and its input terminal receives an AC input signal and rectifies it; a power conversion circuit, and the rectifier The output terminal is connected to generate a constant current output for driving the LED load; the LED drive circuit also includes a frequency detection circuit for detecting the frequency of the AC input signal; a switch circuit, the switch circuit is connected in parallel with the power conversion circuit, the The frequency detection circuit controls the closing and opening of the switching circuit according to the frequency of the AC input signal.

Preferably, when the frequency detection circuit detects that the frequency of the AC input signal is within a first preset value range, the output control signal disconnects the switch circuit; the first preset value range corresponds to the magnetic ballast or AC mains The frequency range of the output voltage or current.

Preferably, when the frequency detection circuit detects that the frequency of the AC input signal is within the second preset value range, the output control signal closes the switch circuit to bypass the power conversion circuit; the second preset value range corresponds to the electronic ballast Frequency range of the output voltage or current of the rectifier.

Preferably, the AC input signal is a voltage or current signal.

Preferably, the frequency detection circuit includes a capacitor, a diode and a voltage regulator tube, one end of the capacitor is connected to the AC input signal, the other end of the capacitor is connected to the power ground through the voltage regulator tube, and the other end of the capacitor is also connected to the control terminal of the switch circuit through the diode .

Preferably, the switch circuit is integrated with the power conversion circuit.

The above-mentioned LED drive circuit can be compatible with the power supply of inductive ballasts, mains electricity, and electronic ballasts through the closing or opening of the switch circuit. Moreover, only one switch circuit is used, so that the design of the entire LED driving circuit is relatively simple.

The utility model also provides an LED driving circuit compatible with an inductance and an electronic ballast, comprising:

A rectifier has an input terminal and an output terminal, and its input terminal receives an AC input signal and rectifies it; a power conversion circuit includes a high-frequency switch, the input terminal of the power conversion circuit is connected to the output terminal of the rectifier, and the power conversion The circuit generates a constant current output to drive the LED load by controlling the high frequency switch;

The LED drive circuit also includes a frequency detection circuit for detecting the frequency of an AC input signal; an interface circuit, the input end of the interface circuit is connected to the output end of the frequency detection circuit, and the interface circuit outputs a control signal to control the high Turning on or off of the frequency switch.

Preferably, the interface circuit has a first input terminal and a second input terminal, and the power conversion circuit further includes a control circuit, and the output terminal of the frequency detection circuit and the output terminal of the control circuit are connected to the first input terminal and the output terminal of the interface circuit respectively. The second input terminal is connected, and the interface circuit generates a control signal to control the high frequency switch to be turned on or off.

Preferably, when the frequency detection circuit detects that the frequency of the AC input signal is within a first preset value range, the interface circuit generates a control signal according to the output of the control circuit to control the high frequency switch to be turned on and off.

Preferably, the first preset value range corresponds to the frequency range of the output voltage or current of the magnetic ballast or the AC mains.

Preferably, the control circuit is a high-frequency switching signal generating circuit.

Preferably, the interface circuit includes an OR gate and a driver amplifier circuit.

Preferably, the LED drive circuit further includes a second switch circuit connected between the high-frequency switch and the LED load, and the interface circuit also includes a second output terminal, and the interface circuit generates a second control signal through the second output The terminal controls the turn-on and turn-off of the second switch circuit.

Preferably, the drive circuit further includes a sampling resistor connected to the second switch circuit, the interface circuit further includes a third input terminal and a fourth input terminal, a reference voltage is preset on the fourth input terminal, and the voltage across the sampling resistor The feedback is connected to the third input terminal of the interface circuit, and is compared with a preset reference voltage value, and the output of the interface circuit is controlled according to the comparison result.

Preferably, when the frequency detection circuit detects that the frequency of the AC input signal is within the second preset value range, the interface circuit generates a control signal according to the output of the frequency detection circuit to control the high frequency switch to be turned on or off. The above-mentioned second preset value range is the frequency range of the output voltage or current of the electronic ballast.

Preferably, the AC input signal is a voltage or current input signal, and the control signal generated by the interface circuit is a voltage control signal.

Preferably, the frequency detection circuit includes a capacitor, a diode and a voltage regulator, one end of the capacitor is connected to an AC input signal, the other end of the capacitor is connected to the power ground through the voltage regulator, and the other end of the capacitor is connected to the input end of the interface circuit through a diode.

The above-mentioned LED driving circuit does not add additional switching circuits, but reuses the original high-frequency switches in the power conversion circuit. By controlling the high-frequency switches, the LED driving circuit is compatible with inductive ballasts or AC mains power and electronic ballasts. power supply. Moreover, the inductance in the power conversion circuit is also used to make the LED drive circuit more suitable for the power supply of the ballast in the constant power mode.

The utility model also provides an LED lamp, which includes an LED light source and the above-mentioned LED drive circuit so that the LED lamp can automatically adapt to the power supply of the AC mains/inductance ballast and the electronic ballast.

Since LED lamps automatically adapt to the power supply of magnetic ballasts, AC mains and electronic ballasts, customers do not need to clarify whether the fluorescent lamps to be replaced are powered by magnetic ballasts or electronic ballasts before purchasing. At the same time, for manufacturers, one LED lamp is compatible with electronic ballasts and magnetic ballasts at the same time, making stocking and production easier and saving management costs.

Description of drawings

Fig. 1 is a functional block diagram of an existing LED drive circuit compatible with magnetic ballasts;

Fig. 2 is the functional block diagram of the driving circuit of Embodiment 1 of the LED driving circuit of the present invention;

Fig. 3 is the principle block diagram of the driving circuit of Embodiment 2 of the LED driving circuit of the present invention;

Fig. 4 is the principle block diagram of the driving circuit of Embodiment 3 of the LED driving circuit of the present invention;

5 is a driving circuit diagram of Embodiment 1 of the LED driving circuit of the present invention;

Fig. 6 is a driving circuit diagram of Embodiment 2 of the LED driving circuit of the present invention;

Fig. 7 is another driving circuit diagram of Embodiment 2 of the LED driving circuit of the present invention;

FIG. 8 is a driving circuit diagram of Embodiment 3 of the LED driving circuit of the present invention.

detailed description

The advantages of the present utility model will be further elaborated below in conjunction with the accompanying drawings and specific embodiments.

FIG. 2 is a functional block diagram of the driving circuit of Embodiment 1 of the LED driving circuit of the present invention. The LED driving circuit 20 is a driving scheme compatible with inductors and electronic ballasts. Referring to FIG. 2 , the input AC mains power is supplied by magnetic ballasts or electronic ballasts 10 . In addition, the AC mains power AC can also directly supply power to LED lamps (not shown). The output of magnetic ballast or AC mains is low-frequency AC voltage or current signal, for example, the frequency is 50/60Hz AC voltage or current signal; the output of electronic ballast power supply is high-frequency AC voltage or current signal, such as the frequency is greater than 20kHz AC Voltage. The LED drive circuit 20 is connected to the output of the inductance ballast or the AC mains or the electronic ballast 10, and includes a rectifier 202, which has an input terminal and an output terminal, and the input terminal receives an AC input signal and rectifies it to realize AC. DC conversion; the power conversion circuit 203 is connected to the output terminal of the rectifier 202, and is used to generate a constant current output to drive the LED load; the frequency detection circuit 204 is used to detect the frequency of the AC input signal; the LED drive circuit 20 also includes a switch circuit K , in this embodiment, the switch circuit K can be a power triode, a field effect tube or other electronic switches; the switch circuit K is connected in parallel with the power conversion circuit 203, and is used to bypass the power conversion circuit 203 or make the power conversion circuit 203 access LED driving circuit, the above-mentioned frequency detection circuit 204 controls the closing and opening of the switch circuit K according to the frequency of the AC input signal, and when the frequency detection circuit 204 detects that the frequency of the AC input signal is within the first preset value range, then it is judged that the LED The front of the LED lamp used in the drive circuit 20 is directly connected to the AC mains or an inductive ballast, then the output control voltage or current signal is disconnected from the switch circuit K, so that the power conversion circuit 203 is connected to the circuit to provide constant current control for the LED load . The first preset value range can be set as the frequency range of the output voltage or current signal of the magnetic ballast, because the general output signal of the magnetic ballast is about 50/60Hz, the range of the first preset value can be set as below 100Hz, for example , of course, can also be set to other range values, the purpose of which is to enable the frequency detection circuit 204 to determine whether the input voltage is a low-frequency signal or a high-frequency signal; 60Hz or so, it is judged to be the output of the magnetic ballast, when the frequency detection circuit 204 detects that the frequency of the AC voltage or current input signal is within the second preset value range, the output control signal closes the switch circuit K, The power conversion circuit 203 is bypassed. The second preset value range is the frequency range of the voltage or current output signal of the electronic ballast. The voltage or current output of the electronic ballast is generally a high-frequency signal, such as a high-frequency AC signal with a frequency greater than 20kHz. Accordingly, the first The range of the second preset value can be set to 10kHz or above 20kHz, and can also be set to other range values. The purpose is that the frequency detection circuit 204 can judge whether the input voltage is a low-frequency signal or a high-frequency signal, that is, it can be set to distinguish whether it is an inductive ballast AC mains or electronic ballast power supply range value. If the frequency detection circuit 204 detects that the input voltage or current is a high-frequency signal and judges that an electronic ballast is connected in front of the LED lamp, the switch K is closed to bypass the power conversion circuit 203 and the LED load is directly connected to the rectifier 202 .

By controlling switching of the switch circuit K by the frequency detection circuit 204, the LED driving circuit 20 can automatically adapt to the magnetic ballast and the electronic ballast.

Embodiment 1 of the LED driving circuit in FIG. 2 also includes a filament simulation circuit 201 for simulating the filament of a fluorescent lamp. The filament simulation circuit 201 receives power from the magnetic ballast or electronic ballast 10 and outputs an AC signal to the rectifier 202. In this embodiment, the filament analog circuit is composed of analog resistors. After the filament analog resistor and before the input rectifier 202, the frequency detection circuit 204 detects the frequency of the AC signal output by the filament analog resistor, that is, the voltage passing through the filament analog resistor 201 Or the frequency of the current signal is detected.

Adding the analog resistance of the filament can be better compatible with the electronic ballast, and more effectively avoid triggering the protection of the electronic ballast 10 . The power conversion circuit 203 can be a high power factor AC/DC conversion circuit, so as to realize high input power factor and output constant current. The high power factor AC/DC can adopt boost, buck, buck-boost, flyback, Sepic, Cuk Wait for one or more isolated or non-isolated switching power supply topologies. The LED load can also be connected in series, parallel, or series-parallel. Generally, it will be connected in a low-voltage mode, such as below 100Vrms, and then select the appropriate LED current according to the power. Capacitors (not shown) are also connected in parallel to both ends of the LED load as needed to reduce current ripple.

Fig. 3 is a schematic block diagram of the principle of the LED driving circuit in Embodiment 2 of the present invention. The drive circuit scheme is also compatible with the drive schemes of inductors, AC mains and electronic ballasts. Referring to Fig. 3, the input alternating current mains AC is powered by the magnetic ballast or the electronic ballast 10; The output connection of the ballast 10 includes the rectifier 302, which receives the AC input signal and rectifies it to realize AC-DC conversion; the power conversion circuit 303 is connected to the output terminal of the rectifier 302, and the power conversion circuit includes a high-frequency switch S , the power conversion circuit controls the high-frequency switch to generate a constant current output to drive the LED load; the frequency detection circuit 304 is used to detect the frequency of the AC input signal. Since power conversion circuits such as high power factor AC/DC circuits already contain power triodes, field effect transistors or other electronic high-frequency switches S, the output of the frequency detection circuit 304 is used to control the high-frequency switch S, thereby realizing a bypass power conversion circuit 303 or to keep the power conversion circuit 303 working normally.

The LED drive circuit 30 also includes an interface circuit 305 , and the output signal of the frequency detection circuit 304 outputs a control signal through the interface circuit 305 . Referring to FIG. 6 , the interface circuit 305 is composed of an OR gate and a driver amplifier circuit. The output of the frequency detection circuit and the control circuit 3031 in the power conversion circuit participate in controlling the high-frequency switch S, wherein the control circuit 3031 is a high-frequency switch signal generating circuit, such as generating a PWM signal. In the embodiment of Fig. 6, the interface circuit includes a first input terminal I1, a second input terminal I2 and a first output terminal O1, and the output terminal of the frequency detection circuit 304 and the output terminal of the control circuit 3031 are connected with the first input terminal of the interface circuit 305 respectively. The terminal I1 is connected to the second input terminal I2, and the interface circuit 305 generates a control signal to control the high-frequency switch S to be turned on or off through the first output terminal O1; in this embodiment, the control circuit 3031 is a control chip that generates a PWM high The frequency switch signal is used to control the high frequency switch S.

When the frequency detection circuit 304 detects that the frequency of the AC input signal is within the first preset value range, the interface circuit 305 generates a control signal according to the output of the control circuit 3031 to control the high-frequency switch S to be turned on and off, so that the power conversion circuit 303 works fine. The first preset value range can be set to the frequency range of the output voltage or current signal of the magnetic ballast or AC mains, because the general output voltage or current signal of the magnetic ballast is about 50/60Hz, the first preset value The range can be set to be below 100 Hz, for example, and of course can also be set to other range values. The purpose is that the frequency detection circuit 304 can determine whether the input voltage is a low-frequency signal or a high-frequency signal. If the frequency detection circuit 304 detects that the input voltage or current signal is a low-frequency signal, For example, if the frequency is between 0 and 100HZ or about 50/60HZ, etc., it is judged that the front of the LED lamp is directly connected to AC mains or magnetic ballast, and the control signal output by the interface circuit 305 enables the original control chip of the power conversion circuit to directly drive The switch S provides constant current control for the LED, and the power conversion circuit in this embodiment is an AC/DC conversion circuit. When the frequency detection circuit detects that the frequency of the AC input signal is within the second preset range, the interface circuit 305 generates a control signal according to the output of the frequency detection circuit 304 to control the high frequency switch S to be turned on or off. The second preset value range is the frequency range of the voltage or current output signal of the electronic ballast. The output of the electronic ballast is generally a high-frequency AC voltage, such as a high-frequency AC signal with a frequency greater than 20kHz. The range of the second preset value It can be set to 10kHz or above 20kHz, or can be set to other range values. The purpose is that the frequency detection circuit 304 can judge whether the input voltage is a low-frequency signal or a high-frequency signal, that is, it can be set to distinguish whether it is an inductive ballast/AC mains or an electronic Range value for ballast power supply. If the frequency detection circuit 304 detects that the input voltage is a high-frequency signal, it is judged that an electronic ballast is connected to the front of the LED lamp, and the control signal output by the interface circuit 305 makes the power conversion circuit 303 no longer work in the high-frequency switching state, and the high-frequency switch S according to the power Different conversion circuit topologies are kept normally open or normally closed. For example, if the power conversion circuit 303 includes a boost topology, the high-frequency switch S remains normally closed, and if it includes a step-down topology, the switch circuit S remains normally open. In this way, the LED load is connected to the rectifier directly or through the AC/DC internal inductor L1.

Compared with the technical solution of the first embodiment, the solution of the second embodiment has no additional bypass switch, but uses the original high-frequency switch S in the power conversion circuit 303 to change the working state of the power conversion circuit 303 .

It should be noted that when an electronic ballast is connected in front of the LED lamp, if the LED load is connected to the rectifier through the internal inductance L1 of the power conversion circuit 303 (high power factor AC/DC in this embodiment), the inductance L1 will also Participate in the work, because the electronic transformer outputs high-frequency voltage and high-frequency current, the inductor L1 will change the working characteristics of the electronic ballast, when connected to some special electronic ballasts, such as constant power electronic ballasts, the inductor L1 Helps control the power delivered to the LED load.

Fig. 4 is the third embodiment of the LED driving circuit of the present invention, compared with Embodiment 2, this embodiment adds a second switch circuit K connected between the high-frequency switch and the LED load, the interface circuit 405 adds a second output port (not shown), and the interface circuit 405 generates a second control signal to control the turn-on and turn-off of the second switch circuit K2 through the second output port.

When the frequency detection circuit 404 detects that the input voltage or current is a low-frequency signal, such as an AC power supply or an inductive ballast directly connected to the front of the LED lamp, the second switch circuit K2 remains disconnected, and the control signal output by the interface circuit makes the power conversion circuit original Some control chips directly drive the high-frequency switch S to provide constant current control for the LED; if the frequency detection circuit 404 detects that the input voltage or current is a high-frequency signal, such as an electronic ballast connected to the front of the LED lamp, first the second switch circuit K2 maintains connected, the power conversion circuit is bypassed, and the LED load is directly connected to both ends of the rectifier 402 . The LED driving circuit also includes an LED load current detection circuit. In this embodiment, the LED load current detection circuit is a resistor Rs, but other circuits for detecting the LED load current are not excluded. If the LED load current does not exceed the predetermined value, then maintain the state that the LED load is directly connected to both ends of the rectifier 402, if the current exceeds the set threshold, then disconnect the second switch circuit K2, and the high-frequency switch S inside the power conversion circuit converts according to the power Different circuit topologies keep normally open or normally closed, for example, if it is a boost topology, the switch S remains normally closed, and if it is a buck topology, the switch S remains normally open, so that the LED load can pass through the internal power conversion circuit The inductance L is connected to both ends of the rectifier 401, and the power flowing into the LED load is controlled by connecting the inductance L inside the power conversion circuit in series. The power conversion circuit in this embodiment is a high-frequency power factor AC/DC circuit.

Fig. 5 is a drive circuit diagram of Embodiment 1 of the LED drive circuit 20 of the present invention, terminals 1 and 2 are one end interfaces of the simulated fluorescent lamp, terminals 3 and 4 are the other end interfaces of the simulated fluorescent lamp, and resistors Rf1, Rf2, Rf3 and Rf4 constitute Filament simulation circuit 201 for simulating fluorescent lamp filaments leads two wires from the midpoint of resistor Rf1 and resistor Rf2 and the midpoint of resistor Rf3 and resistor Rf4 respectively to the input of rectifier 202 . The rectifier 202 is composed of diodes D1, D2, D3 and D4. After the rectifier is a filter capacitor Cfil. The power conversion circuit is a high power factor AC/DC circuit 203, which is composed of a step-down circuit, wherein D5 is a freewheeling diode and L1 is Step-down inductor, Q2 is a high-frequency switch, Co is an output capacitor, the LED load is connected in parallel to both ends of the capacitor Co, and the control chip directly outputs a PWM signal to the control terminal of the high-frequency switch Q2. The LED drive circuit 20 of this embodiment also includes a switch circuit, the switch circuit is a bypass switch Q1, the high voltage end of the bypass switch Q1 is connected to the negative end of the output capacitor Co, and the low voltage end of the bypass switch Q1 is directly connected to the output capacitor after the rectifier. power ground. The control terminal of the bypass switch Q1 is controlled by the output of the frequency detection circuit. The frequency detection circuit 204 includes a capacitor Cs, a voltage regulator tube Vz, a diode Ds, and a circuit in which the capacitor C1 and the resistor R1 are connected in parallel. The frequency detection circuit 204 is connected to the rectifier 202 through the capacitor Cs. One end of the input accepts the AC input signal, and the back of the capacitor Cs is connected to the power ground through the voltage regulator Vz, connected to the capacitor C1 and the resistor R1 through the diode Ds, and connected to the control terminal of the bypass switch Q1 at the same time.

When the front of the LED lamp is connected to the mains or magnetic ballast, the low-frequency AC signal enters the rectifier 202 through the terminals 1~4 and the filament analog circuit 201, and at the same time the low-frequency AC current signal or voltage signal flows in through the capacitor Cs, because the capacitor Cs The working impedance at low frequency is very high, and the current flowing into C1 and R1 through diode Ds is very small, which is not enough to turn on the bypass switch Q1, which keeps the bypass switch Q1 off. The step-down circuit works normally, and the control chip outputs a PWM signal to control the bypass switch Q1, so that the step-down circuit realizes high power factor and output constant current. When the electronic ballast is connected in front of the LED lamp, the high-frequency AC voltage or current flows into the capacitor C1 and the resistor R1 through the capacitor Cs and the diode Ds. Since the high-frequency working impedance of the capacitor Cs is relatively low, the capacitor C1 and the resistor R1 terminal to establish a sufficiently high voltage to turn on the bypass switch Q1, so that the capacitor Co and the negative terminal of the LED are directly connected to the power ground of the rectifier 202, which is equivalent to short-circuiting the step-down circuit by the bypass switch Q1, and the high-frequency signal is directly sent to the LED load through the rectifier For power supply, the input filter capacitor Cfil and the output capacitor Co are connected in parallel to filter out high-frequency current. The function of the voltage regulator tube Vz can control the voltage amplitude of the control terminal of the input bypass switch Q1 when conducting in the forward direction, and provide a reset path for the capacitor Cs when conducting in the reverse direction.

FIG. 6 is a driving circuit diagram of Embodiment 2 of the LED driving circuit of the present invention. Referring to Figure 6, terminals 1 and 2 are one end interface of the simulated fluorescent lamp, terminals 3 and 4 are the other end interface of the simulated fluorescent lamp, resistors Rf1, Rf2, Rf3 and Rf4 form a filament analog circuit for simulating the filament of the fluorescent lamp, from the resistance Rf1 and the resistance Rf2 The midpoint and the midpoints of the resistors Rf3 and Rf4 respectively lead two wires to the input of the rectifier. The rectifier is composed of diodes D1, D2, D3 and D4. After the rectifier is the filter capacitor Cfil. The power conversion circuit is a high power factor AC/DC composed of a step-down circuit, where D5 is a freewheeling diode and L1 is a step-down inductor. , Q2 is a high-frequency switch, Co is an output capacitor, and the LED load is connected in parallel to both ends of the capacitor Co. The control chip 3031 is used to generate a high-frequency switching signal such as a PWM signal. The control chip directly outputs the PWM signal and inputs it to the interface circuit 305, and the interface circuit 305 It includes an OR gate and a driving amplifier circuit, the output of the interface circuit 305 is connected to the control terminal of the high frequency switch Q2, and the other input of the interface circuit 305 is from the output of the frequency detection circuit. The frequency detection circuit 304 includes a capacitor Cs, a diode Ds, and a voltage regulator tube Vz. The frequency detection circuit 304 is connected to one end of the input of the rectifier 302 through the capacitor Cs to receive an AC input signal, and then connected to the power ground through the voltage regulator tube Vz, and connected to the power ground through the diode Ds to the capacitor C1 and the resistor R1, and connected to an input terminal of the interface circuit 305 at the same time, wherein the capacitor C1 and the resistor R1 are connected in parallel. Compared with the drive circuit scheme of the first embodiment in Figure 5, the difference is that there is no bypass switch Q1 in the circuit diagram of the drive circuit of this embodiment, but a high-frequency switch in a high power factor AC/DC circuit composed of a multiplex step-down circuit. Q2, the PWM signal output by the control chip 3031 does not directly drive the high-frequency switch Q2 control terminal, but is input to the interface circuit 305. The interface circuit includes an OR gate and a driving amplifier circuit. The other input of the interface circuit comes from the output of the frequency detection circuit. When the front of the LED lamp is connected to AC mains or magnetic ballast, the current of the low-frequency AC voltage or current signal flowing through the capacitor Cs is very small, and the high level state cannot be established on the capacitor C1 and the resistor R1, which belongs to the low level In this way, the control chip 3031 outputs PWM and directly drives the high-frequency switch Q2 through the OR gate and drive amplification, and the step-down circuit works normally; A high level is established on the resistor R1. At this time, regardless of the state of the control chip output PWM, the high-frequency switch Q2 remains on after passing through the OR gate and driving the amplifier circuit. The output capacitor and LED load are connected to both ends of the rectifier through the step-down inductor L1. . The high-frequency AC signal from the electronic ballast flows in through the rectifiers D1~D4, flows through the output capacitor Co and the LED load, and returns through the inductor L1.

Fig. 7 is another driving circuit diagram of Embodiment 2 of the LED driving circuit of the present invention. Referring to Fig. 7, the structure of the drive circuit is similar to the circuit structure of Fig. 6, the difference is that the output of the frequency detection circuit is connected to a switch element Q3, Q3 can be a triode, a field effect transistor or other electronic switches, and the switch element Q3 is connected to the control chip Peak current detection Cs pin and power ground. When the front of the LED lamp is connected to AC mains or magnetic ballast, the current of the low-frequency AC voltage or current signal flowing through the Cs pin is very small, and the high-level state cannot be established on the capacitor C1 and the resistor R1, and the switching element Q3 Turn off, present a high-impedance state externally, the Cs pin works normally, and the power conversion circuit works normally. In this embodiment, the power conversion circuit is a step-down circuit; when the LED lamp is connected to an electronic ballast, the high-frequency AC Or the voltage signal passes through the capacitor Cs to establish a high level on the capacitor C1 and the resistor R1, the switching element Q3 is turned on, the CS pin is pulled low, and the control chip cannot detect the current signal through the CS pin, so the PWM circuit will always be High level is output, and the high frequency switch Q2 remains on, so that the output capacitor Co and LED are connected to both ends of the rectifier bridge through the inductor L1.

Fig. 8 is the driving circuit diagram of the third embodiment of the LED driving circuit of the present invention. Referring to Fig. 8, compared with the second embodiment, the LED driving circuit further includes a first connected between the high-frequency switch Q2 and the LED load. Two switch circuits, the second switch circuit in this embodiment is a bypass switch Q12; the control circuit is a control chip that can generate a high-frequency switch signal circuit, such as a PWM signal, and the interface circuit 305 also includes a second output terminal Q2Gate, the interface The circuit 305 generates a second control signal to control the turn-on and turn-off of the bypass switch Q12 through the second output terminal Q2Gate. The interface circuit 305, as shown in the dotted line box, includes an RS flip-flop U2, an AND gate U3, an OR gate U4, and an exclusive OR gate U5. At the same time, the current sampling resistor Rs is connected to the lower end of the bypass switch Q12, and the voltage Vcs of the current sampling resistor Rs is connected to The positive terminal of the comparator U1 and the negative terminal of the comparator U1 are the set threshold Vref, and the output signal of the frequency detection circuit 304 (the dotted box in the figure) is HF. When the front of the LED lamp is connected to the mains or magnetic ballast, the frequency detection circuit 304 outputs HF as a low-level signal, and the output of the AND gate U3 is also a low-level signal, the bypass switch Q12 is turned off, and the OR gate The output of U4 depends on the PWM output of the control chip. The AND gate U3 and the OR gate directly drive the high-frequency switch Q2 after passing through the XOR gate U5. Since the output of U3 is a low-level signal at this time, the output logic of the XOR gate U5 Same as the control chip PWM, so the power conversion circuit 303 works normally. In this embodiment, the power conversion circuit is a step-down circuit, as shown by the dotted box 304 in FIG. 8 . When an electronic ballast is connected in front of the LED lamp, the output HF of the frequency detection circuit 303 is high level, and the output of the OR gate U4 is also high level, and the output of the AND gate U3 depends on the output of the trigger U2, and the output of the trigger U2 When the circuit starts, there will be a start signal acting on the S terminal, and the output is high level, so that U3 also outputs high level, the bypass switch Q12 is turned on, and the high frequency switch Q2 is turned off under the action of the exclusive OR gate U5. The output capacitor Co and the LED load are directly connected across the rectifier 302 in parallel. As long as the current flowing through the LED load, that is, the current flowing through the sampling resistor Rs is lower than the set value, Vcs is lower than the set threshold Vref, the output of the comparator U1 is low, and the output of the trigger U2 remains high. , the bypass switch Q12 remains on and the high-frequency switch Q2 remains off; when the sampling voltage Vcs exceeds the set threshold Vref, for example, in the case of a constant power electronic ballast connected in front of the LED lamp, due to the comparator U1 inverts and outputs high level, and the output of trigger U2 also inverts and becomes low level. At this time, U3 outputs low level, and the bypass switch Q12 is turned off. At the same time, the high frequency switch Q2 is in the XOR gate U5 The output capacitor Co and the LED load are connected in parallel to the rectifier 302 through the inductor L1, and the series inductor L1 can reduce the current flowing into the LED load, thereby controlling the power input to the LED load. The interface circuit in the dotted line box can be realized by a logic circuit, a 555 timer or a single-chip microcomputer, and is not limited to the circuit structure in the embodiment.

The utility model also provides an LED lamp, which includes an LED light source and the above-mentioned LED drive circuit so that the LED lamp can automatically adapt to the power supply of an inductance ballast or an electronic ballast. The LED lamp detects the frequency of the input signal through the frequency detection circuit in the drive circuit to determine whether it is powered by an inductive ballast or mains input, or an electronic ballast, and automatically adjusts the LED drive circuit to be compatible with inductive ballasts. It can be used to replace fluorescent lamps in lamps with electronic ballasts or magnetic ballasts.

It should be noted that the embodiments of the present utility model have better implementability, and are not intended to limit the present utility model in any form. Any person familiar with the field may use the technical content disclosed above to change or modify the equivalent effective Embodiments, as long as they do not deviate from the content of the technical solution of the utility model, any modifications or equivalent changes and modifications made to the above embodiments according to the technical essence of the utility model still belong to the scope of the technical solution of the utility model.

Claims (23)

1. A LED drive circuit, comprising: a rectifier having an input terminal and an output terminal, the input terminal of which receives an alternating current input signal and rectifies it; A power conversion circuit, connected to the output terminal of the rectifier, used to generate a constant current output for driving the LED load; it is characterized in that, The LED drive circuit also includes a frequency detection circuit for detecting the frequency of the AC input signal; A switch circuit is connected in parallel with the power conversion circuit, and the frequency detection circuit controls the closing and opening of the switching circuit according to the frequency of the AC input signal. 2 . The LED drive circuit according to claim 1 , wherein when the frequency detection circuit detects that the frequency of the AC input signal is within a first preset value range, it outputs a control signal to disconnect the switch circuit. 3 . 3. The LED driving circuit according to claim 2, wherein the first preset value range corresponds to the frequency range of the output voltage or current of the magnetic ballast or the AC mains. 4. The LED drive circuit according to claim 1, wherein the frequency detection circuit outputs a control signal to close the switch circuit when the frequency detection circuit detects that the frequency of the AC input signal is within a second preset value range. 5. The LED driving circuit according to claim 4, wherein the second preset value range corresponds to the frequency range of the output voltage or current of the electronic ballast. 6. The LED driving circuit according to claim 1, wherein the AC input signal is a voltage or current signal. 7. The LED drive circuit according to claim 1, wherein the frequency detection circuit comprises a capacitor (Cs), a diode (Ds) and a voltage regulator tube (Vz), and one end of the capacitor (Cs) is connected to an AC input signal, The other end of the capacitor (Cs) is connected to the power ground through a voltage regulator (Vz), and the other end of the capacitor is also connected to the control end of the switch circuit through a diode (Ds). 8. The LED driving circuit according to claim 1, wherein the switch circuit and the power conversion circuit are integrated together. 9. The LED drive circuit according to claim 1, further comprising a filament simulation circuit for simulating the filament of a fluorescent lamp, the filament simulation circuit accepts the power of an inductive ballast or AC mains power or an electronic ballast Provides power and outputs an AC signal to the rectifier. 10. A LED drive circuit, comprising: a rectifier having an input terminal and an output terminal, the input terminal of which receives an alternating current input signal and rectifies it; The power conversion circuit includes a high-frequency switch, the input terminal of the power conversion circuit is connected to the output terminal of the rectifier, and the power conversion circuit generates a constant current output to drive the LED load by controlling the high-frequency switch; It is characterized in that, The LED drive circuit also includes a frequency detection circuit for detecting the frequency of the AC input signal; An interface circuit, the input end of which is connected to the output end of the frequency detection circuit, and the interface circuit outputs a control signal to control the turn-on or turn-off of the high-frequency switch. 11. The LED driving circuit according to claim 10, wherein the interface circuit has a first input terminal and a second input terminal, the power conversion circuit further comprises a control circuit, the output terminal of the frequency detection circuit and The output terminals of the control circuit are respectively connected to the first input terminal and the second input terminal of the interface circuit, and the interface circuit generates a control signal to control the high frequency switch to be turned on or off. 12. The LED drive circuit according to claim 11, wherein when the frequency detection circuit detects that the frequency of the AC input signal is within the first preset value range, the interface circuit generates a control signal according to the output of the control circuit and controlling the high frequency switch to be turned on and off. 13. The LED driving circuit according to claim 12, wherein the first preset value range corresponds to the frequency range of the output voltage or current of the magnetic ballast or the AC mains. 14. The LED driving circuit according to claim 11, wherein the control circuit is a high-frequency switching signal generating circuit. 15. The LED driving circuit according to claim 11, wherein the interface circuit comprises an OR gate and a driving amplifier circuit. 16. The LED drive circuit according to claim 15, further comprising a second switch circuit connected between the high-frequency switch and the LED load, the interface circuit further comprising a second output terminal, the The interface circuit generates a second control signal to control the turn-on and turn-off of the second switch circuit through the second output terminal. 17. The LED drive circuit according to claim 16, further comprising a sampling resistor connected to the second switch circuit, said interface circuit further comprising a third input terminal and a fourth input terminal, at the fourth input A reference voltage is preset on the terminal, and the voltage feedback at both ends of the sampling resistor is connected to the third input terminal of the interface circuit, and compared with the preset reference voltage value, and the output of the interface circuit is controlled according to the comparison result. 18. The LED drive circuit according to claim 10, characterized in that, when the frequency detection circuit detects that the frequency of the AC input signal is within the second preset value range, the interface circuit generates a control signal according to the output of the frequency detection circuit The signal controls the high frequency switch to be turned on or off. 19. The LED driving circuit according to claim 18, wherein the second preset value range is the frequency range of the output voltage or current of the electronic ballast. 20. The LED driving circuit according to claim 10, wherein the AC input signal is a voltage or current signal, and the control signal generated by the interface circuit is a voltage or current control signal. 21. The LED drive circuit according to claim 10, characterized in that, the frequency detection circuit includes a capacitor (Cs), a diode (Ds) and a voltage regulator tube (Vz), and one end of the capacitor (Cs) is connected to an AC input signal , the other end of the capacitor (Cs) is connected to the power ground through a voltage regulator (Vz), and the other end of the capacitor is also connected to the input end of the interface circuit through a diode (Ds). 22. The drive circuit according to claim 10, further comprising a filament simulation circuit for simulating the filament of a fluorescent lamp, the filament simulation circuit receives power from an inductance ballast or an electronic ballast and outputs an alternating current The signal is sent to the rectifier, and the frequency detection circuit detects the frequency of the AC signal output by the filament simulation circuit. 23. An LED lamp, comprising an LED light source, characterized in that it also includes an LED drive circuit according to any one of claims 1-22 to make the LED lamp automatically adapt to the AC mains/inductance ballast and electronic ballast device power supply.