LED driving circuit and method

Abstract

The present invention discloses an LED driving circuit and method, which can be applied to a switching power supply driving circuit and a linear driving circuit. The LED driving circuit includes an adjustment tube and a driving control circuit thereof. The adjustment tube receives an input voltage and adjusts the adjustment tube through a driving control circuit to output an expected output current; a reference generating circuit samples the output voltage to obtain an output voltage sampling signal, and obtains a corresponding reference current signal according to the output voltage sampling signal; a current regulating circuit is connected to the control end of the adjustment tube, samples the output current to obtain an output current sampling signal, receives a corresponding reference current signal, and controls the conduction state of the adjustment tube according to the output current sampling signal and the reference current signal to adjust the current flowing through the adjustment tube. The present invention can achieve fast startup through a large current reference in deep dimming and low brightness conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, and in particular to an LED driving circuit and method. Background Art

[0002] Smart lighting applications are becoming more and more widespread. Combined with different scenarios, users want lamps to have different brightness, and dimming needs have begun to become a basic user demand. However, when deep dimming is used, the startup speed is relatively slow when the brightness is low. The reason is that the reference voltage is relatively small when the current is small. For high power factor applications, the output capacitor is usually large. Therefore, when starting up, the output capacitor must be charged to the forward voltage drop of the LED lamp bead before the load can be lit, resulting in a slow startup speed. The smaller the steady-state current, the slower the startup speed. Summary of the invention

[0003] In view of this, an object of the present invention is to provide an LED driving circuit and method that can achieve rapid startup in deep dimming applications, so as to solve the technical problem of difficulty in achieving rapid startup in the prior art.

[0004] The technical solution of the present invention is to provide an LED driving circuit of the following structure, including an adjustment tube and a driving control circuit thereof, wherein the adjustment tube receives an input voltage and is adjusted by the driving control circuit to output a desired output current; the driving control circuit includes:

[0005] A reference generating circuit samples the output voltage to obtain an output voltage sampling signal, and obtains a corresponding reference current signal according to the output voltage sampling signal;

[0006] The current regulating circuit is connected to the control end of the adjusting tube, samples the output current, obtains the output current sampling signal, receives the corresponding reference current signal, and controls the conduction state of the adjusting tube according to the output current sampling signal and the reference current signal to adjust the current flowing through the adjusting tube.

[0007] Optionally, the reference current signal is a continuous analog signal or a discrete analog value; when the reference current signal is a continuous analog signal, the smaller the output voltage is, the larger the reference current signal is; when the reference current signal is a discrete analog value, the reference current signal of the corresponding value is selected according to the size of the output voltage.

[0008] Optionally, the reference current signal includes a first reference signal and a second reference signal, and the second reference signal is greater than the first reference signal; when the output voltage sampling signal is less than the first reference signal, the second reference signal is selected to be connected to the current regulation circuit; when the output voltage sampling signal is greater than the first reference signal, the first reference signal is selected to be connected to the current regulation circuit.

[0009] Optionally, the reference generating circuit includes an output voltage sampling circuit and a comparison circuit, the output voltage sampling circuit samples the output voltage to obtain the output voltage sampling signal, the comparison circuit receives the output voltage sampling signal and a first reference signal, and outputs the comparison result.

[0010] Optionally, the current regulating circuit is an operational amplifier, two input terminals of the operational amplifier receive the reference current signal and the output current sampling signal respectively, and the output terminal of the operational amplifier is connected to the control terminal of the adjustment tube.

[0011] Optionally, the linear LED driving circuit also includes an adjustment tube voltage detection circuit, which samples the voltage across the adjustment tube and compares the obtained adjustment tube voltage sampling signal with a set threshold voltage. When the adjustment tube voltage sampling signal is greater than the set threshold voltage, the current regulation circuit forces and maintains access to the first reference signal or forces the adjustment tube to be turned off.

[0012] The present invention also provides an LED driving circuit, including a switching power supply and a driving control circuit thereof, wherein the switching power supply receives an input voltage and adjusts the switching power supply through the driving control circuit to output an expected output current; the driving control circuit includes:

[0013] A reference generating circuit samples the output voltage to obtain an output voltage sampling signal, and obtains a corresponding reference current signal according to the output voltage sampling signal;

[0014] The current regulating circuit is connected to the control end of the switch tube of the switching power supply, samples the output current, obtains the output current sampling signal, receives the corresponding reference current signal, and controls the conduction state of the switch tube of the switching power supply according to the output current sampling signal and the reference current signal to adjust the output current of the switching power supply.

[0015] Another technical solution provided by the present invention is to provide an LED driving method, based on an LED driving circuit, wherein the LED driving circuit includes an adjustment tube and a driving control circuit thereof, wherein the adjustment tube receives an input voltage and adjusts the adjustment tube through the driving control circuit to output an expected output current; the method includes the following steps:

[0016] Sampling the output voltage to obtain an output voltage sampling signal, and obtaining a corresponding reference current signal according to the output voltage sampling signal;

[0017] The output current is sampled to obtain an output current sampling signal, and the conduction state of the adjustment tube is controlled according to the output current sampling signal and the reference current signal to adjust the current flowing through the adjustment tube.

[0018] Optionally, the reference current signal is a continuous analog signal or a discrete analog value; when the reference current signal is a continuous analog signal, the smaller the output voltage is, the larger the reference current signal is; when the reference current signal is a discrete analog value, the reference current signal of the corresponding value is selected according to the size of the output voltage.

[0019] Another technical solution provided by the present invention is to provide an LED driving method based on an LED driving circuit, wherein the LED driving circuit includes a switching power supply and a driving control circuit thereof, wherein the switching power supply receives an input voltage and adjusts the switching power supply through the driving control circuit to output an expected output current; the method includes the following steps:

[0020] Sampling the output voltage to obtain an output voltage sampling signal, and obtaining a corresponding reference current signal according to the output voltage sampling signal;

[0021] The output current is sampled to obtain an output current sampling signal, a corresponding reference current signal is received, and the conduction state of the switch tube of the switching power supply is controlled according to the output current sampling signal and the reference current signal to adjust the output current of the switching power supply.

[0022] Compared with the prior art, the present invention has the following advantages: in the present invention, different reference current signals can be selected under different output voltages through the reference generating circuit, and the first reference signal and the second reference signal can be set. In deep dimming, under low brightness conditions, fast startup can be achieved through a large current reference; whether the fast startup is enabled is controlled by the adjustment tube voltage detection circuit, so that the stress of the adjustment tube is moderate. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a circuit structure diagram of a first embodiment of an LED driving circuit of the present invention;

[0024] Figure 2 This is a circuit structure diagram of the second embodiment of the LED driving circuit of the present invention. DETAILED DESCRIPTION

[0025] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, but the present invention is not limited to these embodiments. The present invention covers any substitution, modification, equivalent method and scheme made within the spirit and scope of the present invention.

[0026] In order to make the public have a thorough understanding of the present invention, specific details are described in detail in the following preferred embodiments of the present invention, but those skilled in the art can fully understand the present invention without these detailed descriptions.

[0027] The present invention is described in more detail in the following paragraphs by way of example with reference to the accompanying drawings. It should be noted that the accompanying drawings are all simplified and not in exact proportion, and are only used for the purpose of conveniently and clearly assisting in explaining the embodiments of the present invention.

[0028] like Figure 1 As shown, the circuit structure of the first embodiment of the LED driving circuit of the present invention is illustrated.

[0029] The LED driving circuit is a linear driving circuit, including an adjusting tube Q1 and a driving control circuit thereof. The adjusting tube Q1 receives an input voltage Vin and adjusts the adjusting tube Q1 through the driving control circuit to output a desired output current. The driving control circuit includes:

[0030] The reference generation circuit samples the output voltage to obtain an output voltage sampling signal, and obtains a corresponding reference current signal according to the output voltage sampling signal. The reference current signal is a continuous analog signal or a discrete analog value; when the reference current signal is a continuous analog signal, the smaller the output voltage is, the larger the reference current signal is. By setting the upper and lower limits, the above conditions are met between the upper and lower limits of the output voltage, and a fixed reference current signal can be used outside the upper and lower limits; when the reference current signal is a discrete analog value, the reference current signal of the corresponding value is selected according to the size of the output voltage. The embodiment of the present invention takes the reference current signal as a discrete analog value as an example for detailed explanation.

[0031] The current regulating circuit is connected to the control end of the adjusting tube Q1, samples the output current, obtains the output current sampling signal, receives the corresponding reference current signal, and controls the conduction state of the adjusting tube according to the output current sampling signal and the reference current signal to adjust the current flowing through the adjusting tube Q1.

[0032] The reference current signal includes a first reference signal Vref1 and a second reference signal Vref2, and the second reference signal Vref2 is greater than the first reference signal Vref1; when the output voltage sampling signal is less than the first reference signal V1, the second reference signal Vref2 is selected to be connected to the current regulation circuit; when the output voltage sampling signal is greater than the first reference signal V1, the first reference signal Vref1 is selected to be connected to the current regulation circuit.

[0033] The output voltage is sampled to obtain an output voltage sampling signal, and the output voltage sampling signal is compared with a first reference signal V1, and a comparison result is output, and a corresponding reference current signal is selected according to the comparison result; the reference generation circuit includes an output voltage sampling circuit and a comparison circuit U1, the output voltage sampling circuit samples the output voltage to obtain the output voltage sampling signal, the comparison circuit U1 receives the output voltage sampling signal and the first reference signal U1, and outputs the comparison result.

[0034] The current regulating circuit is an operational amplifier U2. Two input terminals of the operational amplifier U2 receive the reference current signal and the output current sampling signal respectively. The output terminal of the operational amplifier is connected to the control terminal of the adjustment tube Q1.

[0035] The LED driving circuit also includes an adjustment tube voltage detection circuit, which samples the voltage at both ends of the adjustment tube Q1 and compares the obtained adjustment tube voltage sampling signal with a set threshold voltage. When the adjustment tube voltage sampling signal is greater than the set threshold voltage, the current regulation circuit forces and maintains the first reference signal Vref1 or forces the adjustment tube to be turned off. The adjustment tube voltage detection circuit can be connected to the control end of the adjustment tube Q1 to turn off the adjustment tube Q1, or it can be connected to the reference generation circuit (indicated by a dotted line in the figure) to force the first reference signal Vref1 to be connected.

[0036] The present invention also provides an LED driving method, based on an LED driving circuit, wherein the LED driving circuit includes an adjustment tube and a driving control circuit thereof, wherein the adjustment tube Q1 receives an input voltage and adjusts the adjustment tube Q1 through the driving control circuit to output an expected output current; the method includes the following steps:

[0037] Sampling the output voltage to obtain an output voltage sampling signal, comparing the output voltage sampling signal with a first reference signal, outputting a comparison result, and selecting a corresponding reference current signal according to the comparison result;

[0038] The output current is sampled to obtain an output current sampling signal, and the conduction state of the adjustment tube is controlled according to the output current sampling signal and the reference current signal to adjust the current flowing through the adjustment tube.

[0039] The reference current signal includes a first reference signal Vref1 and a second reference signal Vref2, the second reference signal Vref2 is greater than the first reference signal Vref1; when the output voltage sampling signal is less than the first reference signal V1, the second reference signal Vref2 is selected as the reference current signal; when the output voltage sampling signal is greater than the first reference signal V1, the first reference signal Vref1 is selected as the reference current signal.

[0040] like Figure 2 The figure shows the circuit structure of the second embodiment of the LED driving circuit of the present invention. The LED driving circuit includes a switching power supply and a driving control circuit thereof. The switching power supply receives an input voltage Vin and adjusts the switching power supply through the driving control circuit to output a desired output current. The driving control circuit includes:

[0041] The reference generation circuit samples the output voltage to obtain an output voltage sampling signal, and obtains a corresponding reference current signal according to the output voltage sampling signal. The reference current signal is a continuous analog signal or a discrete analog value; when the reference current signal is a continuous analog signal, the smaller the output voltage is, the larger the reference current signal is; when the reference current signal is a discrete analog value, the reference current signal of the corresponding value is selected according to the magnitude of the output voltage. The embodiment of the present invention takes the reference current signal as a discrete analog value as an example for detailed description. The output voltage is sampled to obtain an output voltage sampling signal, and the output voltage sampling signal is compared with the first reference signal V1, and the comparison result is output, and the corresponding reference current signal is selected according to the comparison result.

[0042] The current regulating circuit is connected to the control end of the switch tube of the switching power supply, samples the output current, obtains the output current sampling signal, receives the corresponding reference current signal, and controls the conduction state of the switch tube of the switching power supply according to the output current sampling signal and the reference current signal to adjust the output current of the switching power supply.

[0043] The present invention also provides an LED driving method based on an LED driving circuit, wherein the LED driving circuit includes a switching power supply and a driving control circuit thereof, wherein the switching power supply receives an input voltage and adjusts the switching power supply through the driving control circuit to output an expected output current; the method includes the following steps:

[0044] The output voltage is sampled, and an output voltage sampling signal is obtained. According to the output voltage sampling signal, a corresponding reference current signal is obtained. The reference current signal is a continuous analog signal or a discrete analog value. When the reference current signal is a continuous analog signal, the smaller the output voltage is, the larger the reference current signal is. When the reference current signal is a discrete analog value, the reference current signal of the corresponding value is selected according to the size of the output voltage.

[0045] The output current is sampled to obtain an output current sampling signal, a corresponding reference current signal is received, and the conduction state of the switch tube of the switching power supply is controlled according to the output current sampling signal and the reference current signal to adjust the output current of the switching power supply.

[0046] The above-described implementation methods do not constitute a limitation on the protection scope of the technical solution. Any modification, equivalent replacement and improvement made within the spirit and principle of the above-described implementation methods shall be included in the protection scope of the technical solution.

Claims

1. An LED driving circuit, comprising an adjusting tube and a driving control circuit thereof, wherein the adjusting tube receives an input voltage and is regulated by the driving control circuit to output a desired output current; characterized in that: The drive control circuit comprises: A reference generating circuit samples the output voltage to obtain an output voltage sampling signal, and obtains a corresponding reference current signal according to the output voltage sampling signal; A current regulating circuit is connected to the control end of the adjusting tube, samples the output current, obtains an output current sampling signal, receives a corresponding reference current signal, and controls the conduction state of the adjusting tube according to the output current sampling signal and the reference current signal to adjust the current flowing through the adjusting tube; Wherein, the reference current signal is a continuous analog signal or a discrete analog value; when the reference current signal is a continuous analog signal, the smaller the output voltage is, the larger the reference current signal is; When the reference current signal is a discrete analog value, the reference current signal of a corresponding value is selected according to the output voltage. The smaller the output voltage, the larger the value of the selected reference current signal.

2. The LED driving circuit according to claim 1, characterized in that: When the reference current signal is a discrete analog value, the reference current signal includes a first reference signal and a second reference signal, and the second reference signal is greater than the first reference signal; When the output voltage sampling signal is smaller than the first reference signal, the second reference signal is selected to be connected to the current regulating circuit; When the output voltage sampling signal is greater than the first reference signal, the first reference signal is selected to be connected to the current regulating circuit.

3. The LED driving circuit according to claim 2, characterized in that: The reference generation circuit includes an output voltage sampling circuit and a comparison circuit. The output voltage sampling circuit samples the output voltage to obtain the output voltage sampling signal. The comparison circuit receives the output voltage sampling signal and a first reference signal and outputs a comparison result.

4. The LED driving circuit according to claim 2 or 3, characterized in that: The current regulating circuit is an operational amplifier, two input terminals of the operational amplifier receive the reference current signal and the output current sampling signal respectively, and the output terminal of the operational amplifier is connected to the control terminal of the adjustment tube.

5. The LED driving circuit according to claim 2, characterized in that: The LED driving circuit also includes an adjustment tube voltage detection circuit, which samples the voltage across the adjustment tube and compares the obtained adjustment tube voltage sampling signal with a set threshold voltage. When the adjustment tube voltage sampling signal is greater than the set threshold voltage, the current regulation circuit forces and maintains access to the first reference signal or forces the adjustment tube to be turned off.

6. An LED driving circuit, comprising a switching power supply and a driving control circuit thereof, wherein the switching power supply receives an input voltage and adjusts the switching power supply through the driving control circuit to output a desired output current; characterized in that: The drive control circuit comprises: A reference generating circuit samples the output voltage to obtain an output voltage sampling signal, compares the output voltage sampling signal with a first reference signal, outputs a comparison result, and selects a corresponding reference current signal according to the comparison result; A current regulating circuit is connected to the control end of the switch tube of the switching power supply, samples the output current, obtains an output current sampling signal, receives a corresponding reference current signal, and controls the conduction state of the switch tube of the switching power supply according to the output current sampling signal and the reference current signal to adjust the output current of the switching power supply; Wherein, the reference current signal is a continuous analog signal or a discrete analog value; when the reference current signal is a continuous analog signal, the smaller the output voltage is, the larger the reference current signal is; When the reference current signal is a discrete analog value, the reference current signal of a corresponding value is selected according to the output voltage. The smaller the output voltage, the larger the value of the selected reference current signal.

7. An LED driving method, based on an LED driving circuit, wherein the LED driving circuit comprises an adjustment tube and a driving control circuit thereof, wherein the adjustment tube receives an input voltage and is adjusted by the driving control circuit to output a desired output current; characterized in that: The following steps are involved: Sampling the output voltage to obtain an output voltage sampling signal, and obtaining a corresponding reference current signal according to the output voltage sampling signal; Sampling the output current to obtain an output current sampling signal, and controlling the conduction state of the adjustment tube according to the output current sampling signal and the reference current signal to adjust the current flowing through the adjustment tube; Wherein, the reference current signal is a continuous analog signal or a discrete analog value; when the reference current signal is a continuous analog signal, the smaller the output voltage is, the larger the reference current signal is; When the reference current signal is a discrete analog value, the reference current signal of a corresponding value is selected according to the output voltage. The smaller the output voltage, the larger the value of the selected reference current signal.

8. An LED driving method, based on an LED driving circuit, wherein the LED driving circuit comprises a switching power supply and a driving control circuit thereof, wherein the switching power supply receives an input voltage and adjusts the switching power supply through the driving control circuit to output a desired output current; characterized in that: The following steps are involved: Sampling the output voltage to obtain an output voltage sampling signal, and obtaining a corresponding reference current signal according to the output voltage sampling signal; Sampling the output current to obtain an output current sampling signal, receiving a corresponding reference current signal, and controlling the conduction state of the switch tube of the switching power supply according to the output current sampling signal and the reference current signal to adjust the output current of the switching power supply; Wherein, the reference current signal is a continuous analog signal or a discrete analog value; when the reference current signal is a continuous analog signal, the smaller the output voltage is, the larger the reference current signal is; When the reference current signal is a discrete analog value, the reference current signal of a corresponding value is selected according to the output voltage. The smaller the output voltage, the larger the value of the selected reference current signal.

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