TWI683598B - Light-emitting module and light-emitting diode driving circuit - Google Patents

Abstract

A light-emitting module and a light-emitting diode (LED) driving circuit are provided. The light-emitting module includes a LED string and the LED driving circuit. The LED driving circuit includes a power circuit, an energy storage element, a switching circuit, an output diode, and a protection circuit. The power circuit provides a power voltage to an anode terminal of the LED string. The energy storage element is coupled between a cathode terminal of the LED string and a first node. The switching circuit is coupled between the first node and a ground terminal. A cathode terminal of the output diode is coupled to the anode terminal of the LED string. The protection circuit provides an electrical path between the first node and the anode terminal of the output diode. When the switching circuit is turned on, the protection circuit provides a reference voltage to the anode terminal of the output diode to reduce the voltage difference between the cathode terminal and the anode terminal of the output diode.

Description

Light emitting module and light emitting diode driving circuit

The invention relates to a light-emitting diode driving technology, and in particular to a light-emitting module and a light-emitting diode driving circuit which can reduce the cross-voltage of the output diode of the light-emitting diode driving circuit.

FIG. 1 is a circuit schematic diagram of a conventional light-emitting module. Referring to FIG. 1, the light emitting module 100 includes a light emitting diode string 110, an inductor L1, a power switch Q1, and an output diode D1. The light emitting diode string 110 has a plurality of light emitting diodes LD connected in series. The anode end of the light emitting diode string 110 receives a DC voltage VDC. The cathode end of the LED string 110 is coupled to the first end of the inductor L1. The power switch Q1 is coupled between the second end of the inductor L1 and the ground GND. The anode terminal of the output diode D1 is coupled to the second terminal of the inductor L1. The cathode end of the output diode D1 is coupled to the anode end of the light emitting diode string 110.

When the power switch Q1 is turned on, the DC voltage VDC, the light-emitting diode string 110, the inductor L1, the power switch Q1 and the ground GND form a closed loop, so that the light-emitting diode string 110 emits light due to current flow, and the inductor L1 stores electrical energy. In addition, when the power switch Q1 is turned off, the electric energy stored in the inductor L1 discharges the light emitting diode string 110 through the output diode D1.

Furthermore, when the power switch Q1 is turned on, the cross voltage VD1 across the output diode D1 is equal to the sum of the cross voltage VLD1 of the light emitting diode string 110 and the cross voltage VL1 of the inductor L1. In particular, the greater the number of light-emitting diodes LD in the light-emitting diode string 110, the greater the cross-voltage VLD1 of the light-emitting diode string 110. In this way, the larger the cross-voltage VD1 across the output diode D1 is, the easier the output diode D1 is damaged due to long-term overvoltage.

In view of this, the present invention provides a light-emitting module and a light-emitting diode drive circuit, which can reduce the voltage across the output diode of the light-emitting diode drive circuit to prevent the output diode from being overvoltage for a long time And damaged.

The light-emitting diode drive circuit of the present invention is used to drive a light-emitting diode string. The light emitting diode driving circuit includes a power supply circuit, an energy storage element, a switching circuit, an output diode, and a protection circuit. The power circuit is coupled to the anode end of the light-emitting diode string to provide a power supply voltage to the anode end of the light-emitting diode string. The first end of the energy storage element is coupled to the cathode end of the light emitting diode string, and the second end of the energy storage element is coupled to the first node. The switching circuit is coupled between the first node and the ground, and controlled by the control signal to open and close. The cathode end of the output diode is coupled to the anode end of the light-emitting diode string. The protection circuit is coupled to the light emitting diode string, the first node, and the anode end of the output diode to provide an electrical path between the first node and the anode end of the output diode. When the switching circuit is turned on, the protection circuit provides a reference voltage to the anode terminal of the output diode to reduce the voltage difference between the cathode terminal and the anode terminal of the output diode.

In an embodiment of the invention, when the switching circuit is turned on, the output diode is reverse biased. When the switching circuit is turned off, the output diode is turned on.

In an embodiment of the invention, the above protection circuit includes a voltage divider circuit, a first resistor, and a comparator. The voltage dividing circuit is coupled between the anode end and the cathode end of the light emitting diode string, and is used to divide the cross-voltage between the anode end and the cathode end of the light emitting diode string to generate a divided voltage. The first resistor is coupled between the anode terminal of the output diode and the first node. The comparator is coupled to the voltage divider circuit, the first node and the anode terminal of the output diode to compare the divided voltage and the node voltage of the first node to generate and output a reference voltage to the anode terminal of the output diode .

In an embodiment of the invention, the voltage divider circuit described above includes a first capacitor and a second capacitor. The first end of the first capacitor is coupled to the anode end of the light emitting diode string. The first terminal of the second capacitor is coupled to the second terminal of the first capacitor to provide a divided voltage, and the second terminal of the second capacitor is coupled to the cathode terminal of the light emitting diode string. The capacitance value of the first capacitor is greater than the capacitance value of the second capacitor.

In an embodiment of the invention, the above protection circuit further includes a second resistor and a voltage stabilizing diode. The second resistor is coupled between the inverting input terminal of the comparator and the first node. The cathode end of the voltage stabilizing diode is coupled to the first end of the second capacitor, and the anode end of the voltage stabilizing diode is coupled to the second end of the second capacitor.

The light emitting module of the present invention includes a light emitting diode string and the above light emitting diode driving circuit.

Based on the above, the light emitting module and the light emitting diode driving circuit provided by the embodiments of the present invention can provide a reference voltage to the anode end of the output diode when the switching circuit is turned on, so as to reduce the cathode end of the output diode and The voltage difference between the anode terminals prevents the output diode from being damaged due to long-term overvoltage.

In order to make the above-mentioned features and advantages of the present invention more obvious and understandable, the embodiments are specifically described below in conjunction with the accompanying drawings for detailed description as follows.

In order to make the content of the present invention easier to understand, the following specific examples are given as examples on which the present invention can indeed be implemented. In addition, wherever possible, elements/components/steps with the same reference numerals in the drawings and embodiments represent the same or similar components.

2 is a block diagram of a light emitting module according to an embodiment of the invention. Please refer to FIG. 2, the light emitting module 200 can be applied to an e-sports desktop computer, an e-sports laptop or an all-in-one computer, so that the e-sports desktop computer, e-sports laptop or The all-in-one computer has dazzling lighting effects, but the invention is not limited to this. The light emitting module 200 includes a light emitting diode string 210 and a light emitting diode driving circuit 220. The light-emitting diode string 210 has a plurality of light-emitting diodes LD, wherein the light-emitting diodes LD are connected in series. The light emitting diode driving circuit 220 is coupled to the light emitting diode string 210 for driving the light emitting diode string 210. In detail, the light emitting diode driving circuit 220 may include a power circuit 221, an energy storage element 222, a switching circuit 223, an output diode D21, and a protection circuit 224, but the present invention is not limited thereto.

The power circuit 221 is coupled to the anode end of the light emitting diode string 210 to provide a power supply voltage VIN to the anode end of the light emitting diode string 210. The first end of the energy storage element 222 is coupled to the cathode end of the light emitting diode string 210. The second end of the energy storage element 222 is coupled to the first node N1. The switching circuit 223 is coupled between the first node N1 and the ground GND, and controlled by the control signal CS to open and close. The cathode end of the output diode D21 is coupled to the anode end of the light emitting diode string 210. The protection circuit 224 is coupled to the light emitting diode string 210, the first node N1, and the anode terminal of the output diode D21 to provide an electrical path between the first node N1 and the anode terminal of the output diode D21. In particular, when the switching circuit 223 is turned on, the protection circuit 224 may provide the reference voltage VR1 to the anode terminal of the output diode D21 to reduce the voltage difference V21 between the cathode terminal and the anode terminal of the output diode D21.

In detail, when the switching circuit 223 is turned on, the power supply voltage VIN, the light emitting diode string 210, the energy storage element 222, the switching circuit 223 and the ground GND form a closed loop and current flows, resulting in the light emitting diode string 210 emits light due to current flow, and the energy storage element 222 stores electrical energy, where VLD2 is the voltage across the anode and cathode terminals of the light emitting diode string 210, and V22 is the voltage across the energy storage element 222. At this time, the protection circuit 224 provides the reference voltage VR1 to the anode terminal of the output diode D21, where the reference voltage VR1 is a positive voltage less than the power supply voltage VIN. In this case, the output diode D21 is reverse biased, and the voltage difference V21 between the cathode end and the anode end of the output diode D21 is as shown in equation (1). According to equation (1), the reference voltage VR1 can reduce the voltage difference V21 between the cathode end and the anode end of the output diode D21 to prevent the output diode D21 from being damaged due to overvoltage.

V21=VIN－VR1=VLD2+V22－VR1 formula (1)

In addition, when the switching circuit 223 is turned off, the electrical energy stored in the energy storage element 222 can pass through the electrical path between the first node N1 and the anode end of the output diode D21 and the output diode D21 to the light emitting diode The string 210 releases electrical energy. At this time, the output diode D21 is in a forward conducting state, and the absolute value of the voltage difference V21 between the cathode end and the anode end of the output diode D21 is the forward bias value of the output diode D21 (for example, 0.7 V, but not limited to this).

In an embodiment of the present invention, the power circuit 221 may be, for example, an AC to DC converter with power factor correction function, but the present invention is not limited to this.

In an embodiment of the invention, the energy storage element 222 may be implemented by an inductor, but the invention is not limited thereto.

In an embodiment of the present invention, the switching circuit 223 may be implemented by a power transistor, but the present invention is not limited to this.

In an embodiment of the present invention, the LED driving circuit 220 may further include a pulse width modulation signal generator (not shown) for generating the control signal CS and adjusting the duty cycle of the control signal CS To control the brightness of the light emitting diode string 210, but the invention is not limited thereto.

In an embodiment of the invention, the protection circuit 224 of FIG. 2 may be implemented by a micro controller, but the invention is not limited thereto.

In an embodiment of the present invention, the protection circuit 224 of FIG. 2 may use a hardware circuit such as an application specific integrated circuit (ASIC) or a complex programmable logic device (CPLD) or a field programmable gate array (FPGA). Implementation, but the invention is not limited to this.

3 is a schematic circuit block diagram of the protection circuit of FIG. 2 according to an embodiment of the invention. For ease of description, FIG. 3 also illustrates the light-emitting diode string 210, the energy storage element 222, the switching circuit 223, and the output diode D21 of FIG. Referring to FIG. 3, the protection circuit 224 may include a voltage divider circuit 3242, a first resistor R1, a second resistor R2, a voltage stabilizing diode ZD, and a comparator 3244, but the invention is not limited thereto. In another embodiment of the present invention, the protection circuit 224 can also omit the second resistor R2 and the voltage stabilizing diode ZD to reduce the hardware cost.

The voltage dividing circuit 3242 is coupled between the anode end and the cathode end of the light emitting diode string 210 to divide the cross-voltage VLD2 between the anode end and the cathode end of the light emitting diode string 210 to generate a voltage divider Voltage VDIV. In an embodiment of the invention, the voltage dividing circuit 3242 may include a first capacitor C1 and a second capacitor C2, where the capacitance value of the first capacitor C1 is greater than the capacitance value of the second capacitor C2. The first end of the first capacitor C1 is coupled to the anode end of the light emitting diode string 210. The first terminal of the second capacitor C2 is coupled to the second terminal of the first capacitor C1 to provide a divided voltage VDIV. The second terminal of the second capacitor C2 is coupled to the cathode terminal of the light emitting diode string 210. In another embodiment of the present invention, a resistor may be used instead of the first capacitor C1 and the second capacitor C2. If a resistor is used to replace the first capacitor C1 and the second capacitor C2, the resistance value of the resistor used to replace the first capacitor C1 is smaller than the resistance value of the resistor used to replace the second capacitor C2, but it is not limited thereto.

In addition, the first resistor R1 is coupled between the anode terminal of the output diode D21 and the first node N1 to serve as an electrical path between the first node N1 and the anode terminal of the output diode D21. The second resistor R2 is coupled between the inverting input terminal of the comparator 3244 and the first node N1. The cathode terminal of the voltage stabilizing diode ZD is coupled to the first terminal of the second capacitor C2 and the non-inverting input terminal of the comparator 3244. The anode terminal of the voltage stabilizing diode ZD is coupled to the second terminal of the second capacitor C2. The voltage-stabilizing diode ZD is used to stabilize the divided voltage VDIV. The comparator 3244 is coupled to the voltage divider circuit 3242, the first node N1, and the anode terminal of the output diode D21 to compare the divided voltage VDIV with the node voltage VN1 of the first node N1 to generate and output the reference voltage VR1 To the anode end of output diode D21.

In detail, when the switching circuit 223 is turned on, the node voltage VN1 of the first node N1 is equal to the voltage of the ground terminal GND (for example, 0 volts), so that the voltage of the inverting input terminal of the comparator 3244 is equal to the voltage of the ground terminal GND. In addition, the voltage at the non-inverting input terminal of the comparator 3244 is equal to the divided voltage VDIV, where the divided voltage VDIV is as shown in equation (2).

)=(VIN－V22)×(

)         式(2) VDIV=VLD2×(

)=(VIN－V22)×(

) Formula (2)

According to equation (2), the voltage of the non-inverting input terminal of the comparator 3244 is greater than the voltage of the inverting input terminal of the comparator 3244, so the comparator 3244 can output the reference voltage VR1 of a logic high level to the anode terminal of the output diode D21. The reference voltage VR1 at the logic high level may be, for example, the positive saturation output voltage of the comparator 3244. Since the node voltage VN1 is equal to the voltage of the ground terminal GND, the comparator 3244 establishes a crossover voltage (ie, the reference voltage VR1) across the first resistor R1. In this way, the voltage difference V21 between the cathode end and the anode end of the output diode D21 is VLD2+V22-VR1 (as shown in equation (1)). It can be seen that the reference voltage VR1 can reduce the voltage difference V21 between the cathode end and the anode end of the output diode D21 to avoid the output diode D21 being damaged due to overvoltage.

On the other hand, when the switching circuit 223 is turned off, based on Lenz's law, the voltage across V22 of the inductor in the energy storage element 222 is inverted, so the node voltage VN1 of the first node N1 (ie, the comparator The voltage at the inverting input of 3244) is shown in equation (3). In addition, the voltage at the non-inverting input terminal of the comparator 3244 is equal to the divided voltage VDIV (as shown in equation (2)).

VN1=VIN－VLD2－(－V22)= VIN－VLD2+ V22 (3)

In general, the power supply voltage VIN is greater than the voltage across VLD2 between the anode end and the cathode end of the LED string 210. Therefore, when the switching circuit 223 is turned off, the voltage of the non-inverting input terminal of the comparator 3244 is less than the voltage of the inverting input terminal of the comparator 3244, so the comparator 3244 outputs the reference voltage VR1 of a logic low level to the output diode D21. The anode terminal of, where the reference voltage VR1 of a logic low level may be 0 volts, for example. In this case, the electric energy stored in the energy storage element 222 releases the electric energy to the light emitting diode string 210 through the first resistor R1 and the output diode D21, so the output diode D21 is in the forward conducting state, and the output two The absolute value of the voltage difference V21 between the cathode end and the anode end of the pole body D21 is equal to the forward bias value of the output diode D21 (for example, 0.7V, but not limited thereto).

In summary, the light-emitting module and the light-emitting diode driving circuit provided in the embodiments of the present invention can provide a reference voltage to the anode end of the output diode when the switching circuit is turned on, so as to reduce the cathode of the output diode The voltage difference between the extreme terminal and the anode terminal (ie, reverse bias voltage), thus avoiding damage to the output diode due to long-term overvoltage.

Although the present invention has been disclosed as above with examples, it is not intended to limit the present invention. Any person with ordinary knowledge in the technical field can make some changes and modifications without departing from the spirit and scope of the present invention. The scope of protection of the present invention shall be subject to the scope defined in the appended patent application.

200‧‧‧Lighting module 210‧‧‧ LED string 220‧‧‧ LED driving circuit 221‧‧‧Power circuit 222‧‧‧Energy storage element 223‧‧‧Switch circuit 224‧‧‧Protection circuit 3242‧‧‧Voltage dividing circuit 3244‧‧‧Protection circuit C1‧‧‧First capacitor C2‧‧‧Second capacitor CS‧‧‧Control signal D21‧‧‧output diode GND‧‧‧Ground terminal LD‧‧‧ LED N1‧‧‧First node R1‧‧‧ First resistor R2‧‧‧Second resistor VDIV‧‧‧Voltage voltage VIN‧‧‧Power supply voltage VLD2, V22‧‧‧cross pressure VN1‧‧‧ Node voltage VR1‧‧‧Reference voltage V21‧‧‧voltage difference ZD‧‧‧ Voltage stabilizing diode

FIG. 1 is a circuit schematic diagram of a conventional light-emitting module. 2 is a block diagram of a light emitting module according to an embodiment of the invention. 3 is a schematic circuit block diagram of a protection circuit according to an embodiment of the invention.

200‧‧‧Lighting module

210‧‧‧ LED string

220‧‧‧ LED driving circuit

221‧‧‧Power circuit

222‧‧‧Energy storage element

223‧‧‧Switch circuit

224‧‧‧Protection circuit

CS‧‧‧Control signal

D21‧‧‧output diode

GND‧‧‧Ground terminal

LD‧‧‧ LED

N1‧‧‧First node

VIN‧‧‧Power supply voltage

VLD2, V22‧‧‧cross pressure

VR1‧‧‧Reference voltage

V21‧‧‧voltage difference

Claims (10)

A light emitting diode driving circuit is used to drive a light emitting diode string. The light emitting diode driving circuit includes: A power supply circuit, coupled to the anode end of the light-emitting diode string, for providing a power supply voltage to the anode end of the light-emitting diode string; An energy storage element, the first end of the energy storage element is coupled to the cathode end of the light-emitting diode string, and the second end of the energy storage element is coupled to a first node; A switching circuit, coupled between the first node and a ground terminal, and controlled by a control signal to open and close; An output diode, the cathode end of the output diode is coupled to the anode end of the light emitting diode string; and A protection circuit coupled to the LED string, the first node and the anode end of the output diode to provide an electrical path between the first node and the anode end of the output diode , When the switching circuit is turned on, the protection circuit provides a reference voltage to the anode terminal of the output diode to reduce the voltage difference between the cathode terminal and the anode terminal of the output diode. The light emitting diode driving circuit as described in item 1 of the patent application range, wherein when the switching circuit is turned on, the output diode is reverse biased, and when the switching circuit is turned off, the output diode is Follow through. The light emitting diode driving circuit as described in item 1 of the patent application scope, wherein the protection circuit includes: A voltage divider circuit, coupled between the anode end and the cathode end of the light-emitting diode string, is used to divide the cross-voltage between the anode end and the cathode end of the light-emitting diode string to generate a Divided voltage A first resistor coupled between the anode end of the output diode and the first node; and A comparator, coupled to the voltage divider circuit, the first node and the anode terminal of the output diode, for comparing the divided voltage and a node voltage of the first node to generate and output the reference The voltage is applied to the anode terminal of the output diode. The light emitting diode driving circuit as described in item 3 of the patent application scope, wherein the voltage dividing circuit includes: A first capacitor, the first end of the first capacitor is coupled to the anode end of the light emitting diode string; and A second capacitor, the first end of the second capacitor is coupled to the second end of the first capacitor to provide the divided voltage, and the second end of the second capacitor is coupled to the light emitting diode string Cathode side, The capacitance value of the first capacitor is greater than the capacitance value of the second capacitor. The light emitting diode driving circuit as described in item 4 of the patent application scope, wherein the protection circuit further includes: A second resistor coupled between an inverting input terminal of the comparator and the first node; and A voltage stabilizing diode, the cathode end of the voltage stabilizing diode is coupled to the first end of the second capacitor, and the anode end of the voltage stabilizing diode is coupled to the second end of the second capacitor. A light emitting module includes: A string of light-emitting diodes; and A light-emitting diode drive circuit, including: A power supply circuit, coupled to the anode end of the light-emitting diode string, for providing a power supply voltage to the anode end of the light-emitting diode string; An energy storage element, the first end of the energy storage element is coupled to the cathode end of the light-emitting diode string, and the second end of the energy storage element is coupled to a first node; A switching circuit, coupled between the first node and a ground terminal, and controlled by a control signal to open and close; An output diode, the cathode end of the output diode is coupled to the anode end of the light emitting diode string; and A protection circuit coupled to the LED string, the first node and the anode end of the output diode to provide an electrical path between the first node and the anode end of the output diode , When the switching circuit is turned on, the protection circuit provides a reference voltage to the anode terminal of the output diode to reduce the voltage difference between the cathode terminal and the anode terminal of the output diode. The light emitting module of claim 6 of the patent application scope, wherein when the switching circuit is turned on, the output diode is reverse biased, and when the switching circuit is turned off, the output diode is turned on . The light emitting module according to item 6 of the patent application scope, wherein the protection circuit includes: A voltage divider circuit, coupled between the anode end and the cathode end of the light-emitting diode string, is used to divide the cross-voltage between the anode end and the cathode end of the light-emitting diode string to generate a Divided voltage A first resistor coupled between the anode end of the output diode and the first node; and A comparator, coupled to the voltage divider circuit, the first node and the anode terminal of the output diode, for comparing the divided voltage and a node voltage of the first node to generate and output the reference The voltage is applied to the anode terminal of the output diode. The light emitting module according to item 8 of the patent application scope, wherein the voltage dividing circuit includes: A first capacitor, the first end of the first capacitor is coupled to the anode end of the light emitting diode string; and A second capacitor, the first end of the second capacitor is coupled to the second end of the first capacitor to provide the divided voltage, and the second end of the second capacitor is coupled to the light emitting diode string Cathode side, The capacitance value of the first capacitor is greater than the capacitance value of the second capacitor. The light emitting module as described in item 9 of the patent application scope, wherein the protection circuit further includes: A second resistor coupled between an inverting input terminal of the comparator and the first node; and A voltage stabilizing diode, the cathode end of the voltage stabilizing diode is coupled to the first end of the second capacitor, and the anode end of the voltage stabilizing diode is coupled to the second end of the second capacitor.

Images