TWI548305B - Led driving circuit - Google Patents

Description

Light-emitting diode driving circuit

The following description relates to a light-emitting diode driving circuit, and more particularly to a light-emitting diode driving circuit capable of providing a large capacitance storage function.

Please refer to FIG. 7 , which illustrates a schematic diagram of a light emitting diode driving circuit in the prior art. In the figure, the conventional LED driving circuit includes at least a rectifier 91, a switching unit 923, an inductor 922, a light-emitting diode 921, a diode 931, and a capacitor 932. The switch unit 923, the inductor 922 and the light-emitting diode 921 are connected in series to form a loop, and the current inflow point of the loop is electrically connected to the anode of the rectifier 91, and the current flowing out point of the loop is electrically connected to the cathode of the rectifier 91. The capacitor 932 is connected to the light-emitting diode 921, and the anode of the diode 931 is electrically connected to the first end of the capacitor, and the cathode of the diode 931 is electrically connected to the first end of the switch unit 923.

The rectifier 91 is connected to an alternating voltage for converting an output voltage. When the output voltage is present and the voltage value thereof is higher than a threshold value, the switch unit 923 can be set to an on state for the output voltage to supply the light emitting diode 921 via the switch unit 923 and the inductor 922 to emit light, and simultaneously to the capacitor 932. Charging.

When the output voltage does not exist or the voltage value thereof is lower than the threshold value, the switch unit 923 can be set to the off state, and the power stored in the capacitor 932 is supplied to the light emitting diode. 921. Thus, when the AC voltage suddenly drops or stops supplying, the LED 921 remains illuminated until the AC voltage returns above the threshold. Thereby, the light-emitting diode 921 can avoid the occurrence of flicker even in an environment where the alternating voltage is unstable.

Based on the above description, the more power stored in the capacitor 932, the more helpful it is to avoid flickering. However, in the conventional LED driving circuit, the capacitor 932 is connected to the LED 921 in parallel, so the maximum voltage across the capacitor 932 is limited by the voltage across the LED 921, which is usually about 0.7V, this voltage is not too high. In the case of limited cross-voltage, in order to increase the storage capacity of the capacitor 932, only the capacitance value of the capacitor 932 can be increased, for example, the area of the capacitor electrode is increased, but this method also increases the overall volume of the LED driving circuit. Increase its cost.

Because the problem that is urgently needed to be solved at present is how to increase the storage capacity of the capacitance of the light-emitting diode driving circuit without increasing the overall volume of the light-emitting diode driving circuit.

Based on the above object, the present invention provides a light emitting diode driving circuit including a rectifier, a first loop, a second loop, and a third loop. The rectifier is connected to an alternating voltage for converting an output voltage. The first loop may include an inductor in series, a first switching unit, and a light emitting diode. The second circuit includes at least a capacitor and a second body. The first end of the second body can be electrically connected to the first end of the first switch unit, and the second end of the second body can be connected to the first end of the capacitor. The second end of the capacitor is electrically coupled to the second end of the first switching unit. The third loop can be electrically connected to the first a current input end of the primary circuit and the first end of the capacitor, the third circuit includes at least a second switching unit and a second diode, and the first end of the second diode is electrically connected to the first capacitor The second end of the second diode is electrically connected to the first end of the second switch unit, and the second end of the second switch unit is electrically connected to the rectifier.

Preferably, when the first switching unit is turned on and the second switching unit is turned off, the rectifier and the first circuit form a first current path, and the output voltage is supplied to the light emitting diode to emit light, and the inductor is charged.

Preferably, when the first switching unit is turned off and the second switching unit is turned off, the rectifier, the inductor, the second loop, and the light emitting diode system form a second current path, and the output voltage is supplied to the light emitting diode to emit light, and the capacitor is charged. .

Preferably, when the first switching unit is turned on and the second switching unit is turned on, and the voltage across the capacitor is greater than the output voltage, the first loop, the third loop, and the capacitor form a third current path, and the electrical energy stored by the capacitor Supply LED light.

Preferably, the first end of the first switching unit is electrically connected to one end of the inductor, and the second end of the first switching unit is electrically connected to the anode of the LED, and the LED is The negative electrode can be connected to the negative electrode of the rectifier, and the LED driving circuit of the present invention can further include a third diode, and the first end of the third diode can be electrically connected to the negative electrode of the LED component. The second end of the triode body is electrically connected to the second end of the capacitor, and the second circuit further includes a fourth diode, and the first end of the fourth diode is electrically connected to the second end of the capacitor, and The second end of the fourth diode is electrically connected to the anode of the light emitting diode.

Preferably, the negative electrode of the LED is electrically connected to one end of the inductor, and the first end of the first switch unit is electrically connected to the other end of the inductor.

Preferably, the LED driving circuit of the present invention further comprises a third switching unit And a fifth diode, the first end of the third switching unit can be electrically connected to the positive pole of the rectifier, and the second end of the third switching unit can be electrically connected to the current input end of the first loop, the fifth The first end of the pole body is electrically connected to the current input end of the first circuit, and the second end of the fifth diode body is electrically connected to the negative pole of the rectifier.

Preferably, when the first switching unit, the second switching unit and the third switching unit are both turned off, the inductor, the second loop, the LED and the fifth diode form a fourth current path, which is stored by the inductor The electrical energy supply emits light emitting diodes.

Preferably, when the third switching unit is turned off, and the first switching unit and the second switching unit are both turned on, the first loop, the third loop, and the capacitor system form a fifth current path, and the power stored by the capacitor supplies the light. The diode emits light.

Preferably, when the second current path is formed and the voltage across the capacitor is greater than the output voltage, the current is still output by the rectifier due to the inductance, and the capacitor is charged.

11, 91‧‧‧Rectifier

121, 921‧‧‧Lighting diodes

122, 922‧‧‧Inductance

123‧‧‧First switch unit

142‧‧‧Second switch unit

131, 141, 151, 152, 22, 931 ‧ ‧ diodes

132, 932‧‧‧ capacitor

21‧‧‧ Third switch unit

The above and other features and advantages of the present invention will become more apparent from the detailed description of the exemplary embodiments illustrated in the appended claims 2A is a schematic diagram of operation of a light emitting diode driving circuit according to a first embodiment of the present invention in a first mode; FIG. 2B is a light emitting according to a first embodiment of the present invention 2 is a schematic diagram of the operation of the LED driving circuit in the second mode; FIG. 2C is a schematic diagram of the operation of the LED driving circuit according to the first embodiment of the present invention in the third mode; A schematic diagram of a light emitting diode driving circuit of a second embodiment of the invention; 4A is a schematic diagram of operation of a light emitting diode driving circuit according to a second embodiment of the present invention in a first mode; FIG. 4B is a light emitting diode driving circuit according to a second embodiment of the present invention; 2 is a schematic diagram of operation of a light emitting diode driving circuit according to a second embodiment of the present invention in a third mode; and FIG. 5 is a third embodiment according to the present invention. FIG. 6A is a schematic diagram of operation of a light emitting diode driving circuit according to a third embodiment of the present invention in a first mode; FIG. 6B is a third embodiment of the present invention FIG. 6C is a schematic diagram of operation of a light emitting diode driving circuit according to a third embodiment of the present invention in a third mode; FIG. 6D A schematic diagram of operation of the LED driving circuit according to the third embodiment of the present invention in the fourth mode; FIG. 6E is a fifth embodiment of the LED driving circuit according to the third embodiment of the present invention. under The schematic for; and FIG. 7 is a line schematic diagram conventional art light emitting diode drive circuits.

As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items. When the phrase "at least one of" is preceded by a list of elements, the entire list of elements is modified instead of the individual elements in the list.

1 and 2A to 2C are respectively a schematic diagram of a light emitting diode driving circuit according to a first embodiment of the present invention, a first mode operation diagram, a second mode operation diagram, and a third mode operation diagram.

In FIG. 1, the light emitting diode driving circuit includes a rectifier 11, a first circuit, a second circuit, and a third circuit. The first loop includes an inductor 122 connected in series, a first switch unit 123, and a light emitting diode 121, but the series sequence in FIG. 1 is merely an example, not a limitation; in other embodiments, it may be changed. The series order of the inductor 122, the first switching unit 123, and the light emitting diode 121.

The rectifier 11 is connected to an alternating voltage for converting an output voltage. The second circuit includes at least one capacitor 132 and one diode 131. The anode of the diode 131 can be electrically connected to one end of the first switching unit 123, and the cathode of the diode 131 can be connected to the anode of the capacitor 132. The cathode of the capacitor 132 can be electrically connected to the cathode of the rectifier 11.

The third circuit is electrically connected between the current input terminal of the first circuit and the positive electrode of the capacitor 132. The third circuit includes at least a second switch unit 142 and a diode 141. The anode of the diode 141 can be electrically connected. The anode of the diode 141 is electrically connected to the first end of the second switch unit 142, and the second end of the second switch unit 142 is electrically connected to the rectifier 11.

The above-mentioned switching units 123 and 142 can be realized by a switching transistor, such as an NMOS transistor or other switching elements of similar functions. Various modes of operation of the light emitting diode driving circuit will be described below.

In the first mode, as shown in FIG. 2A, when the first switching unit 123 is turned on and the second switching unit 142 is turned off, the rectifier 11 forms a current path P1 with the first loop. Since the first switching unit 123 is turned on, the anode of the diode 131 is The potential of the terminal is almost equal to the ground potential, and the potential of the negative terminal of the diode 131 is equal to the potential of the positive electrode of the capacitor 132. Since the potential of the negative terminal of the diode 131 is higher than that of the positive terminal, the diode is in the first mode. 131 is in the off state. Therefore, in the first mode, current flows along the current path P1, the light-emitting diode 121 is supplied to emit light, and the inductor 122 is charged.

In the second mode, as shown in FIG. 2B, when the first switching unit 123 is turned off and the second switching unit 142 is turned off, the rectifier 11, the inductor 122, the second loop, and the light-emitting diode 121 form a current path P2. . Based on the characteristics of the components of the inductor, the current on the inductor does not change instantaneously, so when the first switching unit 123 is turned off, the current continues to flow to the diode 131. In other words, if the output voltage of the rectifier 11 is greater than the voltage value of the anode of the capacitor 132 when the first switching unit 123 is turned off, the diode 131 is turned on to cause current to flow into the capacitor 132; if the first switching unit 123 is turned off, the rectifier 11 The output voltage is lower than the voltage of the positive pole of the capacitor 132. Because the current on the inductor cannot be changed instantaneously, the positive terminal voltage of the diode 131 is pulled up by the inductor, so the current still flows to the diode 131, and the current still flows into the capacitor 132. The positive voltage of 132 will still gradually increase. In short, in the second mode, the output voltage converted by the rectifier 11 supplies the light-emitting diode 121 to emit light, and simultaneously charges the capacitor 132, and the voltage value of the positive terminal of the capacitor 132 can be greater than that of the rectifier 11 with charging. The output voltage.

In the third mode, as shown in FIG. 2C, when the first switching unit 123 is turned on and the second switching unit 142 is turned on, and the voltage across the capacitor 132 is greater than the output voltage, the diode 141 is in an on state, then the first The circuit, the third circuit and the capacitor 132 form a current path P3, and the power stored by the capacitor 132 supplies the light-emitting diode 121 to emit light; conversely, if the voltage across the capacitor 132 is less than the output voltage, the diode 141 is turned off. State, still output power from the output voltage according to the current path P1 The photodiode 121 emits light.

It can be seen from the above three modes that, unlike the case where the voltage across the capacitor is limited by the on-voltage of the light-emitting diode, the energy stored in the capacitor 132 of the first embodiment of the present invention is not illuminated. The voltage across the pole 121 is limited, and in the second mode, even if the output voltage of the rectifier 11 is lower than the voltage at the positive terminal of the capacitor 132, the capacitor 132 can be continuously charged by the output voltage of the rectifier 11 to make the positive end of the capacitor 132. The voltage rises. Therefore, in the LED driving circuit of the first embodiment of the present invention, the voltage across the capacitor can be effectively increased without being limited by the conduction voltage of the LED, and the amount of stored electricity is also increased. In the conventional art, the present invention can increase the storage capacity of the capacitor 132 without increasing the size of the capacitor.

Please refer to FIG. 3 and FIG. 4A to FIG. 4C, which are respectively a schematic diagram of a light emitting diode driving circuit according to a second embodiment of the present invention, a first mode operation diagram, a second mode operation diagram, and a third mode operation diagram. .

The second embodiment is different from the first embodiment in that the series connection order of the inductor 122, the first switching unit 123, and the light-emitting diode 121 in the first loop is different, and two diodes 151 are added in the second embodiment. With 152.

The first end of the first switch unit 123 is electrically connected to one end of the inductor 122, and the second end of the first switch unit 123 is electrically connected to the anode of the light-emitting diode 121, and the light-emitting diode 121 The negative electrode can be connected to the negative electrode of the rectifier 11.

The anode of the diode 131 can be electrically connected to the first end of the first switching unit 123, and the cathode of the diode 131 can be electrically connected to the anode of the capacitor 132.

The second circuit further includes a diode 151. The anode of the diode 151 is electrically connected to the cathode of the capacitor 132, and the cathode of the diode 151 is electrically connected to the second end of the first switch unit 123. The positive electrode of the diode 152 is electrically connected to the light emitting diode 121 The negative electrode, and the negative electrode of the diode 152 is electrically connected to the negative electrode of the capacitor 132.

Similar to the first embodiment, in the second embodiment, when the first switching unit 123 is turned on and the second switching unit 142 is turned off, the LED driving circuit enters the first mode, and the rectifier 11 forms a current with the first loop system. Path P4, as shown in Figure 4A. The current flows along the current path P4, and the light-emitting diode 121 is supplied to emit light, and the inductor 122 is charged.

When the first switching unit 123 is turned off and the second switching unit 142 is turned off, the LED driving circuit enters the second mode, and the rectifier 11, the inductor 122, the second loop, and the LED 121 form a current path P5. The current flows along the current path P5, and the output voltage converted by the rectifier 11 supplies the light-emitting diode 121 to emit light while charging the capacitor 132.

When the first switching unit 123 is turned on and the second switching unit 142 is turned on, and the voltage across the capacitor 132 is greater than the output voltage, the LED driving circuit enters the third mode, and the first loop, the third loop, the capacitor 132, and the second The polar body 152 forms a current path P6, and the electrical energy stored by the capacitor 132 supplies the light-emitting diode 121 to emit light.

In the second embodiment, the operating principles of the LED driving circuit in the first mode, the second mode, and the third mode are the same as those in the second embodiment, and thus are not described herein again.

Please refer to FIG. 5 and FIGS. 6A to 6E , which are respectively a schematic diagram of a light emitting diode driving circuit according to a third embodiment of the present invention, a first mode, a second mode, a third mode, a fourth mode, and a Schematic diagram of the operation of the five modes.

The third embodiment is different from the second embodiment in that the third embodiment further includes a third switching unit 21 and a diode 22. The first end of the third switch unit 21 can be electrically connected to the anode of the rectifier 11 , and the second end of the third switch unit 21 can be electrically connected to the current input end of the first loop, and the cathode of the diode 22 can be electrically connected. Sexual connection The current input terminal of the first circuit, the positive electrode of the diode 22 can be electrically connected to the negative electrode of the rectifier 11.

When the third switching unit 21 is turned on, the first switching unit 123 is turned on, and the second switching unit 142 is turned off, the LED driving circuit enters the first mode, and the rectifier 11 and the third switching unit 21 form a current with the first circuit system. Path P7, as shown in Figure 6A. The current flows along the current path P7, the light-emitting diode 121 is supplied to emit light, and the inductor 122 is charged.

When the third switching unit 21 is turned on, the first switching unit 123 is turned off, and the second switching unit 142 is turned off, the LED driving circuit enters the second mode, the rectifier 11, the third switching unit 21, the inductor 122, the second loop, and The light-emitting diode 121 forms a current path P8 as shown in FIG. 6B. The current flows along the current path P8, and the output voltage converted by the rectifier 11 supplies the light-emitting diode 121 to emit light while charging the capacitor 132.

When the third switching unit 21 is turned on, the first switching unit 123 is turned on, and the second switching unit 142 is turned on, and the voltage across the capacitor 132 is greater than the output voltage, the LED driving circuit enters the third mode, and the first loop, the first The three circuits, the capacitor 132 and the diode 152 form a current path P9. As shown in FIG. 6C, the energy stored by the capacitor 132 supplies the light emitting diode 121 to emit light. In addition, when the third switching unit 21 is turned off, the first switching unit 123 is turned on, and the second switching unit 142 is turned on, the LED driving circuit also enters the third mode, and the electric energy stored by the capacitor 132 supplies the LED 201. Glowing.

In the third embodiment, the operating principles of the LED driving circuit in the first mode, the second mode, and the third mode are the same as those in the second embodiment, and thus are not described herein again.

When the third switching unit 21, the first switching unit 123 and the second switching unit 142 When both are off, the diode 22, the inductor 122, the second loop, and the diode 121 form a current path P10, and the LED driving circuit enters the fourth mode, as shown in FIG. 6D. The third switching unit 21 is turned off to stop receiving the current from the rectifier 11, and the current on the inductor 122 cannot be changed instantaneously. Therefore, the voltage of the negative terminal of the diode 22 is lowered by the inductor 122 to make the diode 22 turn on, and the output current continues. Flow to capacitor 132. Therefore, in the fourth mode, the capacitor 122 is discharged, the capacitor 132 is charged, and the power is supplied to the light-emitting diode 121 to emit light.

When the third switching unit 21 is turned off, and the first switching unit 123 is turned on and the second switching unit 142 is turned off, the diode 22 and the first circuit form a current path P11, and the LED driving circuit enters the fifth mode, such as Figure 6E shows. The third switching unit 21 is turned off to cause the current from the rectifier 11 to stop receiving, and the current on the inductor 122 cannot be instantaneously changed, so the inductor 122 continues to output current to the LED 121, and the diode 22 is turned on. Therefore, in the fifth mode, the inductor 122 is discharged, and the power is supplied to the light-emitting diode 121 to emit light.

In the third embodiment, the advantage of increasing the storage capacity of the capacitor 132 without increasing the size of the capacitor is still maintained, and the state of the off and the conduction of the third switching unit 21 is further manipulated to further fine-tune the LED driving circuit. Power factor (PF). When the voltage of the AC power source is high, the third switching unit 21 can be turned on, and the LED driving circuit is controlled to perform the first mode to directly receive a large current from the AC power source to the LED 201.

When the voltage of the AC power source is lowered, the third switching unit 21 can be turned on, and the LED driving circuit is controlled to perform the second mode, and the current is continuously supplied from the AC power source to the LED 121, and the capacitor 132 is charged. . In the second mode, the current received from the AC power source is less than the current in the first mode.

When the voltage of the AC power source is too low or does not exist, the third switch unit 21 may be turned off, and the LED driving circuit may be controlled to perform the third, fourth or fifth mode, and the capacitor 132 or the inductor 122 is powered to emit light. The diode 121 emits light.

Thus, when the voltage of the AC power source is too low or does not exist, the LED driving circuit does not receive current from the AC power source; when the voltage of the AC power source is low, the LED driving circuit receives a smaller current from the AC power source; When the voltage of the AC power source is high enough, the LED driving circuit receives a large current from the AC power source, and the operation can effectively fine-tune the power factor of the LED driving circuit.

The specific embodiments of the present invention are intended to be illustrative only and not to limit the invention to the above embodiments, without departing from the spirit of the invention and the following claims. The scope of the invention and the various changes made are within the scope of the invention.

11‧‧‧Rectifier

121‧‧‧Lighting diode

122‧‧‧Inductance

123‧‧‧First switch unit

131, 141‧‧ ‧ diode

142‧‧‧Second switch unit

132‧‧‧ Capacitance

Claims (10)

An LED driving circuit comprises: a rectifier connected to an AC voltage for converting an output voltage; and a first circuit comprising an inductor connected in series, a first switching unit and a light emitting diode a second circuit comprising a capacitor and a first diode, the first end of the first diode being electrically connected to the first end of the first switching unit, the first diode The second end is connected to the first end of the capacitor, the second end of the capacitor is electrically coupled to the second end of the first switching unit; and a third circuit is electrically connected to the first circuit Between the current input terminal and the first end of the capacitor, the third circuit includes at least a second switch unit and a second diode, and the first end of the second diode is electrically connected The second end of the second diode is electrically connected to the first end of the second switch unit, and the second end of the second switch unit is electrically connected to the rectifier. The illuminating diode driving circuit of claim 1, wherein when the first switching unit is turned on and the second switching unit is turned off, the rectifier forms a first current path with the first circuit. The output voltage supplies the light emitting diode to emit light and charges the inductor. The illuminating diode driving circuit of claim 1, wherein when the first switching unit is turned off and the second switching unit is turned off, the rectifier, the inductor, the second loop, and the illuminating diode system are formed. A second current path is provided by the output voltage to illuminate the LED and charge the capacitor. The illuminating diode driving circuit of claim 1, wherein when the first switching unit is turned on and the second switching unit is turned on, and the voltage across the capacitor is greater than the output voltage, the first loop, The third loop and the capacitor form a third current path, and the electrical energy stored by the capacitor supplies the light emitting diode to emit light. The illuminating diode driving circuit of claim 1, wherein the first end of the first switching unit is electrically connected to one end of the inductor, and the first switching unit is The two ends are electrically connected to the positive electrode of the light emitting diode, and the negative electrode of the light emitting diode is connected to the negative electrode of the rectifier; wherein the light emitting diode driving circuit further comprises a third diode, the third diode The first end of the body is electrically connected to the negative electrode of the light emitting diode element, and the second end of the third diode is electrically connected to the second end of the capacitor; and wherein the second circuit further comprises a a fourth diode, the first end of the fourth diode is electrically connected to the second end of the capacitor, and the second end of the fourth diode is electrically connected to the anode of the LED . The illuminating diode driving circuit of claim 1, wherein the negative electrode of the illuminating diode is electrically connected to one end of the inductor, and the first end of the first switching unit is electrically connected to the The other end of the inductor. The illuminating diode driving circuit of claim 1, further comprising a third switching unit and a fifth diode, wherein the first end of the third switching unit is electrically connected to the anode of the rectifier And the second end of the third switching unit is electrically connected to the current input end of the first circuit, and the first end of the fifth diode The second end of the fifth diode is electrically connected to the current input end of the first circuit. The illuminating diode driving circuit of claim 7, wherein the inductor, the second loop, and the illuminating when the first switching unit, the second switching unit, and the third switching unit are both turned off The diode and the fifth diode system form a fourth current path, and the electrical energy stored by the inductor supplies the light emitting diode to emit light. The illuminating diode driving circuit of claim 7, wherein the first circuit and the third circuit are turned off when the third switching unit is turned off, and the first switching unit and the second switching unit are both turned on. The loop and the capacitor form a fifth current path, and the electrical energy stored by the capacitor supplies the light emitting diode to emit light. The illuminating diode driving circuit of claim 3, wherein when the second current path is formed and the voltage across the capacitor is greater than the output voltage, current is still output by the rectifier due to the inductance. Charge the capacitor.