TWI584674B - Led driving circuit - Google Patents

Description

Light-emitting diode driving circuit

The invention relates to a light-emitting diode driving circuit, in particular to a light-emitting diode driving circuit with a protection function.

Please refer to the first figure, which is a circuit diagram of a conventional LED driving circuit disclosed in U.S. Patent Publication No. 20120049741. The light emitting diode driving circuit includes a power supply unit 302. The power supply unit 302 has a dimming output terminal DIM, a feedback terminal FB and an output terminal OUT. The feedback terminal FB is used to receive a minimum feedback signal. The power supply unit 302 generates a driving voltage at the output terminal OUT based on an input voltage and a minimum feedback signal to drive a plurality of LED strings. A current balancing circuit 301 has an input and a plurality of outputs. The input end is configured to receive a reference voltage, and each output end is coupled to one of the negative ends of the LED string to regulate a current of the LED string. A feedback selector 303 has a plurality of input terminals and an output terminal, and the input terminals are respectively coupled to the negative terminals of the LED strings to receive a feedback signal representing a voltage drop of the LED strings. Based on the received feedback signal, the feedback selector 303 generates a minimum feedback signal at the output.

The power supply unit 302 regulates the driving voltage based on the lowest feedback signal, whereby the driving voltage has a voltage value that is sufficient to drive a plurality of LED strings. The current balancing circuit 301 has a plurality of current sources CS, each of which is coupled to the negative terminal of the LED string to provide and regulate the current of the LED string. A first end of a current setting resistor Rset is coupled to each current source CS and a second terminal is grounded. The current supplied by the current source CS can be adjusted by the resistance of the current setting resistor Rset. The dimming output terminal DIM of the power supply unit 302 is configured to provide a dimming signal to each current source CS.

A protection circuit 304 is coupled between the negative terminal of the LED string and the current balancing circuit 301 to protect the current balancing circuit 301 from being damaged by overvoltage. The protection circuit 304 has a plurality of transistors T, each of which has a first end, a second end, and a control end. The control terminal is coupled to a predetermined voltage Vg. The first end is coupled to the negative terminal of the LED string, and the second terminal is coupled to the current balancing circuit 301. The voltage withstand capability of the transistor T is higher than the driving voltage generated by the power supply unit 302. The protection circuit 304 withstands most of the voltage of the driving voltage when the LED string is short-circuited, and protects the current balancing circuit 301 from being directly coupled to the driving voltage.

However, since the current balancing circuit 301 is still operating normally, this causes the transistor T of the protection circuit 304 to pass through a predetermined current of the LED string while being subjected to a voltage almost equal to the driving voltage. This causes the transistor T to generate excessive power consumption and cause the temperature to be too high to be destroyed. Once the transistor T is damaged, the original protection function will not be exerted and the current balancing circuit 301 will be further caused. damage. As a result, the expected protection function may not be achieved.

The above summary and the following detailed description are exemplary in order to further illustrate the scope of the claims. Other objects and advantages of the present invention will be described in the following description and drawings.

In view of the problem that the protection circuit in the prior art may be damaged due to excessive temperature, the LED driving circuit provided by the present invention detects the voltage across the transistor, and reduces or cuts off the light emission when it is judged that the voltage is too high. The current of the pole string is used to protect the transistor from over-temperature damage.

To achieve the above objective, the present invention provides a light emitting diode driving circuit including at least one light emitting unit and a protection detecting circuit. Each of the light emitting units includes a light emitting diode string, a current stabilizing circuit, and a transistor. The LED string is coupled to a driving voltage. The steady current circuit is coupled to the LED string to control the current flowing through the LED string. The transistor is coupled between the LED string and the current stabilizing circuit. The protection detection circuit is coupled to one of the transistor and the LED string in each of the illumination units to detect a connection point and receive a dimming signal, where the dimming signal represents a first state and any of the detection connection points When a voltage is higher than a predetermined protection value, a protection signal is generated. When the dimming signal represents a second state and the voltage of any of the detection connection points is higher than a predetermined protection value, the protection signal is stopped. Wherein, at least the transistor or the current stabilizing circuit whose voltage corresponding to the connection point is higher than the predetermined protection value reduces or cuts off the current of the LED string when the protection signal is generated.

The invention also provides a light emitting diode driving circuit comprising at least one light emitting unit and a protection detecting circuit. Each of the light emitting units includes a light emitting diode string, a current stabilizing circuit, and a transistor. The LED string is coupled to a driving voltage. The steady current circuit is coupled to the LED string to control the current flowing through the LED string. The transistor is coupled between the LED string and the current stabilizing circuit. The protection detection circuit generates a clamp reference signal to one of the control terminals of each transistor, and couples one of the transistor and the LED string in each of the illumination units to detect the connection point. When one of the measured connection points is higher than a predetermined protection value, the voltage drop clamps one of the reference level signals to lower or cut off the current of the LED string.

The invention further provides a light emitting diode driving circuit comprising a plurality of light emitting diode strings, a steady current circuit, a plurality of transistors and a plurality of protection detecting circuits. A plurality of LED strings are coupled to a driving voltage. The steady current circuit is coupled to the LED string to control the current flowing through the LED string. A plurality of transistors are coupled between the corresponding LED strings and the current stabilizing circuit. The plurality of protection detection circuits are coupled to a detection connection point of the corresponding LED string and the corresponding transistor and receive a dimming signal. Each protection detection circuit represents a first state and corresponds to the dimming signal. When the voltage of one of the detection connection points is higher than a predetermined protection value, a protection signal is generated, so that the corresponding transistor or the corresponding steady current circuit reduces or cuts the current of the corresponding LED string when the protection signal is generated. Each protection detection circuit stops production when the dimming signal represents a second state and the voltage of the corresponding detection connection point is higher than a predetermined protection value. Health protection signal.

The above summary and the following detailed description are exemplary in order to further illustrate the scope of the claims. Other objects and advantages of the present invention will be described in the following description and drawings.

Prior art:

301‧‧‧ Current balancing circuit

302‧‧‧Power supply unit

303‧‧‧Responsible selector

304‧‧‧Protection circuit

CS‧‧‧current source

DIM‧‧‧ dimming output

FB‧‧‧reporting end

OUT‧‧‧ output

Rset‧‧‧ current setting resistor

T‧‧‧O crystal

Vg‧‧‧Preset voltage

this invention:

100, I1, I2‧‧‧ steady current circuit

110, 210‧‧ ‧ clamp protection circuit

120, 220‧‧‧Protection detection circuit

130‧‧‧Lighting diode strings

200, 300, 400‧‧‧ current sharing circuit

230‧‧‧Multiple LED strings

410‧‧‧Safe operation detection circuit

420‧‧‧Safe operation protection circuit

C‧‧‧ output capacitor

C1‧‧‧ capacitor

Cn, Cn1, Cn2‧‧‧Detect connection points

D‧‧‧Rectifying diode

D1, D2‧‧‧ diode

CRn, CRn1, CRn2‧‧‧ steady current connection

I‧‧‧current source

L‧‧‧Inductance

M‧‧‧ power switch

M1‧‧‧Photoelectric crystal

M2, Q, Q1, Q2‧‧‧ transistors

OP‧‧‧Operational Amplifier

R1, R2, R3, R4‧‧‧ resistance

Sd, Sd1, Sd2‧‧ ‧ level detection signals

Sdim‧‧‧ dimming signal

Sm1‧‧‧ control signal

Sq, Sq1, Sq2‧‧‧ clamp reference level signal

Sp‧‧‧protection signal

VOUT‧‧‧ drive voltage

VIN‧‧‧ input voltage

Vr‧‧‧ reference signal

Vref‧‧‧reference voltage

ZD‧‧‧Zina diode

The first figure is a circuit diagram of a conventional LED driving circuit disclosed in U.S. Patent Publication No. 20120049741.

The second figure is a circuit diagram of a light emitting diode driving circuit according to a first preferred embodiment of the present invention.

The third figure is a circuit diagram of a light emitting diode driving circuit according to a second preferred embodiment of the present invention.

The fourth figure is a circuit diagram of a light emitting diode driving circuit according to a third preferred embodiment of the present invention.

Figure 5 is a circuit diagram of a light-emitting diode driving circuit according to a fourth preferred embodiment of the present invention.

Figure 6 is a circuit diagram of a light emitting diode driving circuit in accordance with a fifth preferred embodiment of the present invention.

Figure 7 is a circuit diagram of a protection detection circuit in accordance with a first preferred embodiment of the present invention.

Figure 8 is a circuit diagram of a protection detection circuit in accordance with a second preferred embodiment of the present invention.

Figure 9 is a circuit diagram of a protection detecting circuit in accordance with a third preferred embodiment of the present invention.

2 is a circuit diagram of a light emitting diode driving circuit according to a first preferred embodiment of the present invention. The LED driving circuit comprises a current stabilizing circuit 100, a clamping protection circuit 110, a protection detecting circuit 120 and a light emitting diode string 130. The LED string 130 is coupled to a driving voltage VOUT to receive the current required for illumination. The drive voltage VOUT is provided by a switching converter circuit. In this embodiment, the switching conversion circuit is a DC-DC conversion circuit including an inductor L, a power switch M, a rectifying diode D, and an output capacitor C. The power switch M is periodically turned on and off according to the control of a control signal Sm1, so that the power of an input voltage VIN is rectified and filtered by the inductor L, the rectifying diode D, and the output capacitor C to provide a driving voltage VOUT. In practical application, the present invention can be applied to provide a DC output switching conversion circuit, such as a forward conversion circuit, a flyback conversion circuit, a DC to DC buck conversion circuit, a half bridge conversion circuit, and a full bridge. Conversion circuit, etc.

The current stabilizing circuit 100 is coupled to the LED string 130 via a steady current connection terminal CRn to control the current flowing through the LED string 130, so that the current flowing through the LED string 130 is stabilized at a predetermined current value. . In this embodiment, the current stabilizing circuit 100 includes a current source I. The current source I can be a fixed current source or a controllable current source for the user to adjust the LED string according to actual needs. The current size. The steady current circuit 100 generates the control signal Sm1 to the power switch M according to the current or voltage of the LED string 130, so that the power provided by the DC-DC conversion circuit can maintain the current of the LED string 130 at a predetermined current value. .

The clamp protection circuit 110 is coupled between the LED string 130 and the current stabilizing circuit 100. The clamp protection circuit 110 includes a transistor Q having a first end, a second end, and a control end. The first end of the transistor Q is coupled to the LED string 130, the second end is coupled to the current stabilizing circuit 100, and the control terminal receives a clamp reference signal Sq. When the LED driving circuit is abnormal due to any circuit, a voltage at the second end of the transistor Q rises to a voltage equal to or lower than a threshold voltage of the transistor Q, the transistor Q The voltage at the second end of the transistor Q is cut off, that is, a voltage of the steady current connection terminal CRn of the steady current circuit 100 and the transistor Q continues to rise. In this way, the voltage of the steady current connection terminal CRn of the current stabilizing circuit 100 can be clamped to a level lower than the clamp reference level signal Sq, and the voltage of the steady current connection terminal CRn is prevented from exceeding the withstand voltage limit of the steady current circuit 100. The damage of the steady current circuit 100 is caused. The withstand voltage of the transistor Q must be higher than the driving voltage VOUT to achieve the above clamping function without being damaged.

The protection detection circuit 120 is coupled to the detection diode C of one of the LED array 130 and the transistor Q to receive a level detection signal Sd representing the detection connection point Cn, and generates a clamp reference signal. Sq to transistor Q. When detecting a voltage of the connection point Cn is lower than a predetermined protection value, clamping the reference level signal Sq The level of the clamp is a preset clamp pressure level. When the voltage of the detection connection point Cn is higher than the predetermined protection value, the level of the clamped reference level signal Sq is lowered, so that the transistor Q is turned off. At this time, the current drop of the LED string 130 is zero. In this way, the problem that the transistor Q is damaged due to over temperature can be avoided.

3 is a circuit diagram of a light emitting diode driving circuit according to a second preferred embodiment of the present invention. In the present embodiment and the following embodiments, the technical features of the present invention will be more clearly described, and the drawings and corresponding descriptions of the conversion circuits will be omitted.

The LED driving circuit includes a current sharing circuit 200, a clamping protection circuit 210, a protection detecting circuit 220, and a plurality of LED strings 230. For convenience of description, it is redefined as a plurality of light-emitting units, each light-emitting unit includes a corresponding light-emitting diode string of the plurality of light-emitting diode strings 230, and a corresponding transistor in the transistors Q1 to Q2 of the clamp protection circuit 210. And corresponding steady current circuits I1~I2 in the current sharing circuit 200. Each of the LED strings of the plurality of LED strings 230 is connected in parallel with each other and coupled to a driving voltage VOUT. The steady current circuits I1~I2 are coupled to the corresponding LED strings to control the current flowing through the LED strings, so that each LED string of the plurality of LED strings 230 flows through substantially the same Current. The transistors Q1 to Q2 are coupled between the corresponding LED strings of the plurality of LED strings 230 and the corresponding current stabilizing circuits of the current stabilizing circuits I1 to I2. The current sharing circuit 200 generates a control signal Sm1 to a conversion circuit (not shown) according to the current or voltage of the plurality of LED strings 230, so that the power provided by the conversion circuit can maintain the plurality of LED strings 230. Electricity The flow is stabilized at a predetermined current value.

The protection detection circuit 220 is coupled to the detection connection points Cn1 to Cn2 of the transistor and the LED string in the plurality of light-emitting units to receive the level detection signal Sd1 representing the level of the detection connection points Cn1 to Cn2. ~Sd2, and generate clamp reference level signals Sq1~Sq2 to transistors Q1~Q2. The protection detection circuit 220 in this embodiment may include a plurality of protection detection circuits 120 as shown in the second figure to detect and protect each of the transistors Q1 to Q2. The level of the clamp reference level signals Sq1~Sq2 can be set according to the actual application, and is preferably set to the same level of the clamp reference level signals Sq1~Sq2, and both are at a first voltage value. At this time, the light emitting diode driving circuit can operate normally and cause a plurality of light emitting diode strings 230 to flow through substantially the same current. Based on the level detection signals Sd1 to Sd2, the protection detecting circuit 220 determines whether the level of the detection connection points Cn1 to Cn2 is higher than a predetermined protection value. When the level of any of the detection connection points Cn1~Cn2 is higher than the predetermined protection value, at least the level of the corresponding clamp reference level signal is lowered to a second voltage value. In this way, the transistor corresponding to the detection connection point where the abnormal rise in the level is turned off, and the current flowing through is reduced to zero. In addition, when any of the detection connection points Cn1~Cn2 is higher than the predetermined protection value, the protection detection circuit 220 can simultaneously lower all the clamp reference level signals Sq1~Sq2 to the second voltage value, so that The LED driver circuit enters a protection mode.

The protection detection circuit 220 can additionally receive a dimming signal Sdim. The dimming signal Sdim switches between a first level and a second level. When the dimming signal Sdim is at the first level, the representative LED driving circuit operates in a first state, and at this time, the plurality of LED strings 230 emit light; when the dimming signal Sdim is at the second level, The representative LED driving circuit operates in a second state, at which time a plurality of LED strings 230 stop emitting light. By adjusting the length of the first state and the second state, dimming effects of different dimming ratios can be obtained. In the second state, the plurality of LED strings 230 stop emitting light. At this time, a voltage across the plurality of LED strings 230 is lowered to increase the level of the detection connection points Cn1 to Cn2. In order to avoid the misjudgment of the protection detection circuit 220 at this time, when the dimming signal Sdim represents the second state and the level of any of the detection connection points Cn1 C Cn2 is higher than the predetermined protection value, the protection detection circuit 220 stops the down clamp. Press the reference level signal Sq1~Sq2 to clamp the reference level signal. When the dimming signal Sdim represents the first state and the voltage of any of the detection connection points Cn1~Cn2 is detected to be higher than the predetermined protection value, the protection detection circuit 220 reduces all or the corresponding clamp reference level signal. The level is to cut off the current of all the LED strings or the abnormal LED strings.

Please refer to the fourth figure, which is a circuit diagram of a light emitting diode driving circuit according to a third preferred embodiment of the present invention. Compared with the embodiment shown in the third figure, the main difference is that the plurality of diodes D1 to D2 are used in the embodiment, and one of the positive ends of each of the diodes is coupled to the corresponding one of the detection connection points Cn1 to Cn2. The detection connection point and the negative terminal are coupled to each other and coupled to a protection detection circuit 120. The diodes D1~D2 receive the level detection signals Sd1~Sd2, and generate a level detection signal Sd to the protection detection according to a highest level in the level detection signals Sd1~Sd2. Circuit 120. Therefore, when any of the level detecting signals Sd1 to Sd2 exceeds a predetermined protection value, the protection detecting circuit 120 can determine the level detecting signal Sd. The protection detection circuit 120 of the present embodiment can use the protection detection circuit 120 shown in the second figure by the use of the diodes D1 to D2, without the protection detection circuit 220 as shown in the third figure. A plurality of protection detection circuits 120 are required to detect and protect all the illumination units.

Of course, the protection detection circuit 120 can receive an additional dimming signal Sdim as shown in the third embodiment, and the dimming signal Sdim represents a second state and any of the connection points Cn1 C Cn2 are detected. When the protection value is higher than the predetermined protection value, the protection detection circuit 120 stops the adjustment of one of the clamped reference level signals Sq, and turns off the transistors Q1 to Q2 to stop the current flow.

Referring to FIG. 5, it is a circuit diagram of a light emitting diode driving circuit according to a fourth preferred embodiment of the present invention. Compared with the embodiment shown in FIG. 4, the protection detection circuit 120 of this embodiment is modified to control a current sharing circuit 300 to achieve a protection effect. The control terminals of the transistors Q1~Q2 of the clamp protection circuit 210 are coupled to a clamp reference level signal Sq. In this embodiment, the clamped reference level signal Sq is a fixed level signal, regardless of whether the detection connection points Cn1 C Cn2 are too high. The protection detecting circuit 120 determines whether any of the level detecting signals Sd1 to Sd2 exceeds a predetermined protection value according to a level detecting signal Sd. If so, the protection detection circuit 120 generates a protection signal Sp. The current sharing circuit 300 has a plurality of current stabilizing circuits I1~I2, which are respectively coupled to corresponding light emitting diode strings of the plurality of LED strings 230, so that the plurality of light emitting diode strings 230 emit light The polar body stream flows through a predetermined current. The current sharing circuit 300 is coupled to the protection detecting circuit 120. When the protection signal Sp is generated, the current stabilizing circuits I1~I2 reduce the current flowing through the LED string, and may even drop to zero. In this way, it is ensured that the heat generated by the transistors Q1 to Q2 of the clamp protection circuit 210 is within the specifications of the transistor without being overheated and burned.

6 is a circuit diagram of a light emitting diode driving circuit according to a fifth preferred embodiment of the present invention. Compared with the embodiment shown in FIG. 5, a current sharing circuit 400 further includes a security operation detecting circuit 410 and a security operation protection circuit 420. The protection detection circuit 120 of the present embodiment uses the safety operation detection circuit 410 and the safety operation protection circuit 420 of the current sharing circuit 400 to achieve the protection effect. The safety operation detecting circuit 410 is coupled to the current stabilizing circuits I1 to I2, and when a voltage or a current of any of the current stabilizing circuits in the current stabilizing circuits I1 to I2 exceeds a predetermined safety upper limit value (for example, a steady current circuit) An abnormal signal is generated when the current is too high, too low, and the voltage at either end of the current stabilizing circuit is higher or lower than a normal operating voltage range. When the safety operation protection circuit 420 continuously receives the abnormal signal for a first predetermined length of time, enters a protection mode to reduce the current of the steady current circuit or the entire steady current circuit (ie, the current of the LED string) in which the circuit abnormality occurs or cutoff. Since the setting of the first predetermined time length of the general safe operation protection circuit 420 is considered to be a long time due to possible misjudgment. However, in the case where the transistors Q1 to Q2 of the clamp protection circuit 210 to be protected by the present invention are overheated, the time may be too long and the transistors Q1 to Q2 may not be protected and burned. Therefore, when the protection detection circuit 120 is based on a standard When the bit detection signal Sd determines that any of the level detection signals Sd1 to Sd2 exceeds a predetermined protection value, a protection signal Sp is generated to the safety operation protection circuit 420 to shorten the first predetermined time length to a second predetermined time length (ie, The second predetermined time length is shorter than the first predetermined time length). When the level of any of the detection connection points Cn1~Cn2 is higher than the predetermined protection value, the voltages of the steady current connection terminals CRn1~CRn2 of the steady current circuits I1~I2 also rise simultaneously and are detected by the safety operation detection circuit 410. An abnormal signal is generated when an exception occurs. Therefore, the safe operation protection circuit 420 enters the protection mode immediately after the second predetermined time length elapses. Alternatively, the security operation protection circuit 420 can also shorten the first predetermined time length to the second predetermined time length and start the countdown to the protection mode when receiving the protection signal Sp, regardless of whether the security operation detection circuit 410 can be correct. Detecting an abnormal situation in which the steady current connection terminals CRn1 to CRn2 rise.

In addition, the embodiments shown in the fifth and sixth figures are all illustrated by taking a plurality of LED strings as an example, and can be applied to a single string of LED strings in practical applications without affecting the protection of the present invention. effect.

Figure 7 is a circuit diagram of a protection detection circuit in accordance with a first preferred embodiment of the present invention. The embodiment of the present invention and the following protection detection circuit can be directly or simply adjusted as the protection detection circuit 120 in the above embodiment. The protection detection circuit comprises a voltage divider, a dimming crystal M1, a filter circuit and a protection signal generating circuit. The voltage divider includes resistors R1 and R2 connected in series. The resistor R1 is coupled to a level detecting signal Sd, and the resistor R2 is grounded, and generates a voltage dividing signal of the level detecting signal Sd at a voltage dividing point. Dimming The transistor M1 is coupled to the voltage divider and the protection signal generating circuit, and a control terminal thereof receives a dimming signal Sdim. When the dimming signal Sdim represents a first state, the dimming crystal M1 is turned on. At this point, the protection detection circuit operates normally. When the dimming signal Sdim represents a second state, the dimming crystal M1 is turned off, and no matter what the level of the voltage dividing signal is, no transistor M2 is turned on to stop the protection and avoid the adjustment. The possible protection of the light process is misjudged. The dimming crystal M1 can be omitted when there is no doubt that the actual application has no dimming signal or dimming. The filter circuit includes a capacitor C1 and a resistor R3 connected in parallel to filter out noise in the voltage divider signal of the voltage divider, which can be omitted in practical applications. The protection signal generating circuit includes a resistor R4 and a transistor M2 connected in series for generating a clamp reference signal Sq. One end of the resistor R4 is coupled to a reference voltage Vref, and one end is coupled to the transistor M2. The other end of the transistor M2 is grounded, and a control terminal is coupled to the voltage dividing point of the voltage divider. When a level of the level detecting signal Sd represents a voltage detecting a connection point lower than a predetermined protection value, the level of the voltage dividing signal is lower than a conducting threshold voltage of the transistor M2. At this time, a level of the clamp reference level signal Sq is equal to the reference voltage Vref. In other words, when the protection detecting circuit of the embodiment is applied to the LED driving circuit shown in the second to fourth embodiments, a level of the reference voltage Vref is determined according to the withstand voltage capability of the current stabilizing circuit; When applied to the LED driving circuit shown in FIG. 5 to FIG. 6 , the level of the reference voltage Vref is determined according to a logic judgment level of the steady current circuit.

When the level of the level detecting signal Sd represents that the voltage of the detecting connection point is higher than the predetermined protection value, the level of the voltage dividing signal is higher than the conduction of the transistor M2. Threshold voltage. At this time, the transistor M2 is turned on to lower the level of the clamp reference level signal Sq to almost zero. Thereby, the reference voltage signal Sq is clamped off the transistors Q1 Q Q2 of the clamp protection circuit 210, the current of the steady current circuit is reduced or cut, or the safe operation protection circuit in the current sharing circuit is triggered.

Referring to FIG. 8, a circuit diagram of a protection detecting circuit according to a second preferred embodiment of the present invention. Compared with the embodiment shown in the seventh figure, this embodiment replaces the filter circuit with an operational amplifier OP. The voltage divider of the voltage divider is coupled to a non-inverting input of the operational amplifier OP, and an inverting input of the operational amplifier OP is coupled to a reference signal Vr. When the level of the voltage dividing signal is higher than a level of the reference signal Vr, the operational amplifier OP conducts the crystal M2. With the operational amplifier OP, the transistor M2 can be accurately turned on to avoid the problem of different protection points caused by different conduction threshold voltages between different transistors.

Referring to FIG. 9, a circuit diagram of a protection detection circuit according to a third preferred embodiment of the present invention. Compared with the embodiment shown in the seventh figure, this embodiment replaces the voltage divider with a Zener diode ZD and omits the filter circuit. When the level of the level detecting signal Sd represents that the voltage of the detecting connection point is higher than the predetermined protection value, the level of the level detecting signal Sd is higher than a breakdown voltage of the Zener diode ZD, so that Zener II When the polar body ZD is turned on and further touches the transistor M2, the protection detecting circuit generates a low-level clamped reference level signal Sq for protection.

As described above, the present invention fully complies with the three requirements of the patent: novelty, advancement, and industrial applicability. The present invention has been better in the above It is to be understood by those skilled in the art that the present invention is not intended to limit the scope of the invention. It should be noted that variations and permutations equivalent to those of the embodiments are intended to be included within the scope of the present invention. Therefore, the scope of the invention is defined by the scope of the following claims.

100‧‧‧ steady current circuit

110‧‧‧ clamp protection circuit

120‧‧‧Protection detection circuit

130‧‧‧Lighting diode strings

C‧‧‧ output capacitor

Cn‧‧‧Detecting connection points

D‧‧‧Rectifying diode

I‧‧‧current source

L‧‧‧Inductance

M‧‧‧ power switch

Q‧‧‧Optocrystal

Sd‧‧ ‧ level detection signal

Sm1‧‧‧ control signal

Sq‧‧‧ clamp reference level signal

VOUT‧‧‧ drive voltage

VIN‧‧‧ input voltage

CRn‧‧‧ steady flow connection

Claims (10)

A light-emitting diode driving circuit comprising: at least one light-emitting unit, each of the light-emitting units comprising: a light-emitting diode string coupled to a driving voltage; and a current stabilizing circuit coupled to the light-emitting diode string Controlling a current flowing through the LED string; and a transistor coupled between the LED string and the current stabilizing circuit; and a protection detecting circuit coupled to each of the lighting units The transistor and one of the LED strings detect a connection point and receive a dimming signal, wherein the dimming signal represents a first state and a voltage of one of the detection connection points is higher than a predetermined protection When the value is a value, a protection signal is generated. When the dimming signal represents a second state and the voltage of the detection connection point is higher than the predetermined protection value, the protection signal is stopped; wherein at least the connection point is corresponding The transistor or the current stabilizing circuit having the voltage higher than the predetermined protection value reduces or cuts off the current of the LED string when the protection signal is generated. The illuminating diode driving circuit of claim 1, further comprising at least one diode, wherein a positive terminal of each of the diodes is coupled to the detecting connection point and a negative terminal The protection detection circuit is coupled and coupled. The illuminating diode driving circuit of claim 1 or 2, wherein one of the control terminals of the transistor receives a clamp reference level signal, and the current stabilizing circuit has a first current The value is stably flowing through the corresponding LED string, and when receiving the protection signal, the second current value is stably passed through the corresponding LED string. The illuminating diode driving circuit of the first or the second aspect of the invention further includes a safety operation detecting circuit and a safety operation protection circuit, wherein the safety operation detecting circuit is coupled to the at least one steady current And generating an abnormal signal when the voltage or a current of the at least one current stabilizing circuit exceeds a predetermined safety upper limit value, and the safe operation protection circuit continuously receives the abnormal signal for a first predetermined For a length of time, entering a protection mode causes the at least one current stabilizing circuit to reduce or cut the current of the LED string. The illuminating diode driving circuit of claim 4, wherein the security operation protection circuit enters the protection mode when receiving the protection signal or continuously receiving for a second predetermined length of time, wherein the second predetermined The length of time is shorter than the first predetermined length of time. A light-emitting diode driving circuit comprising: at least one light-emitting unit, each of the light-emitting units comprising: a light-emitting diode string coupled to a driving voltage; a steady current circuit, correspondingly coupled to the LED string to control the current flowing through the LED string; and a transistor coupled between the LED string and the current stabilizing circuit; And a protection detection circuit for generating a clamped reference level signal to one of the control terminals of each of the transistors, and coupling the transistor in each of the light-emitting units to one of the LED strings for detecting connection And, when one of the detected connection points is higher than a predetermined protection value, the one of the clamped reference level signals is lowered to lower or cut the current of the LED string. The illuminating diode driving circuit of the sixth aspect of the invention, wherein the protection detecting circuit further receives a dimming signal, and determining the voltage of the detecting connection point when the dimming signal represents a first state Whether it is higher than a predetermined protection value, when the dimming signal represents a second state, the judgment is stopped. The illuminating diode driving circuit of the sixth or seventh aspect of the invention, further comprising at least one diode, wherein a positive end of each of the diodes is coupled to the detecting connection point, A negative terminal is coupled to each other and coupled to the protection detection circuit. An LED driving circuit comprising: a plurality of LED strings coupled to a driving voltage; a current stabilizing circuit coupled to the light emitting diode strings to control a current flowing through the light emitting diode strings; and a plurality of transistors coupled to the corresponding light emitting diode strings and the steady current And a plurality of protection detection circuits coupled to the corresponding detection connection point of the corresponding LED string and the corresponding transistor and receiving a dimming signal; wherein each of the protection detection circuits When the dimming signal represents a first state and the voltage of one of the detecting connection points is higher than a predetermined protection value, a protection signal is generated, so that the corresponding transistor or the corresponding current stabilizing circuit is protected. When the signal is generated, the current corresponding to the LED string is reduced or cut off, and each of the protection detection circuits is higher than the voltage corresponding to the detection connection point when the dimming signal represents a second state When the protection value is predetermined, the protection signal is stopped. The illuminating diode driving circuit of claim 9, wherein when the protection detecting circuit generates the protection signal, the other protection detecting circuits respectively reduce or cut off the current corresponding to the LED string.