TW201918117A - LED driving circuit using high voltage - Google Patents

Abstract

An LED driving circuit comprises an LED unit having a plurality of LEDs connected in series, coupled with a voltage charging and discharging unit and powered by a rectified AC voltage of an AC input voltage. A controllable current limiting unit or a current limiting unit in association with a switch connects the LED unit to ground. The voltage charging and discharging unit has first and second diodes connected to the LED unit, and a storage capacitor to form a charging path through the first diode and a discharging path through the second diode in order to provide a steady state capacitor voltage for reducing the number of LEDs connected in series in the LED unit.

Description

High-voltage LED driving circuit

The present invention relates to a lighting device based on a light-emitting diode (LED), and more particularly to a lighting device using a high input voltage, suitable for a lighting device based on a light-emitting diode, and a low-cost driving circuit.

In recent years, high-voltage LED lighting devices have been developed and deployed to replace traditional incandescent and fluorescent lamps because of their energy-saving advantages.

The current-to-voltage (IV) characteristic curve of the light-emitting diode is similar to that of a general ordinary diode. When the voltage applied to the light-emitting diode is less than the forward voltage of the diode, only a very small current flows through the light-emitting diode. body. When the voltage exceeds the forward voltage, the current through the light-emitting diode is greatly increased. In general, in most operating ranges, the illumination intensity of a lighting device based on a light-emitting diode is proportional to the current passed, but not at high currents. The driving devices, which are usually designed for lighting devices based on light-emitting diodes, are mainly designed to provide a constant current in order to emit stable light and extend the life of the light-emitting diode.

In order to improve the brightness of the illumination device based on the light-emitting diode, a plurality of light-emitting diodes are usually connected in series to form a lighting unit based on the light-emitting diode, and a plurality of lighting units based on the light-emitting diode can be further Further connected in series to form a lighting device. The operating voltage required for each illuminating device is usually determined by the forward voltage of the illuminating diode in the lighting unit, how many LEDs are in each lighting unit, and how each lighting unit is connected to each other. And how each lighting unit receives the voltage from the power source in the lighting device.

A number of techniques have been developed to enable illumination devices for light emitting diodes to use operating voltages such as 110 volts AC or 220 volts AC without the need for voltage conversion devices. Generally, the light-emitting diode in the illumination device includes one or more light-emitting diode illumination units, and each of the light-emitting diode illumination units is further divided into a plurality of light-emitting diode segments, and each of the light-emitting diode segments can be The switch or current source is controlled by the controller as the associated switch or current source is selectively turned "on" or "off" and as the operating AC voltage increases or decreases.

One of the disadvantages of a light-emitting diode driving circuit using a high voltage such as 110 volts alternating current voltage or 220 volts alternating voltage without using a voltage converting device is that the light emitting diodes connected in series in the light emitting diode driving circuit are The total number must be quite large so that the forward voltage across the light-emitting diodes is not much less than the applied high input voltage to maintain sufficient efficiency to avoid excessive power loss. In other words, the total number of light-emitting diodes connected in series in the light-emitting diode driving circuit is determined by the magnitude of the input high voltage, and the cost of the light-emitting diode device is also increased by the high voltage.

As more and more light-emitting diode-based lighting devices are used in high-intensity lighting devices with high input voltage power, a driving device is designed to reduce the total number of light-emitting diodes that must be connected in series, and can provide Good efficiency and low cost use of AC high voltages from power sources that are readily available on the wall as input voltages has created a strong need.

SUMMARY OF THE INVENTION The present invention provides a light emitting diode driving circuit capable of efficiently driving and connecting a small number of series-connected light-emitting diodes directly using a high AC input voltage to reduce cost. Therefore, the LED driving circuit of the present invention comprises a light emitting diode unit having a plurality of LEDs connected in series between the positive end and the negative end, coupling a voltage charging and discharging unit, and inputting an alternating voltage The rectified AC voltage is supplied.

According to the present invention, the voltage charging and discharging unit has a first diode whose positive terminal is connected to the negative terminal of the light emitting diode unit, and a negative terminal of the second diode is connected to the positive electrode of the light emitting diode unit. End, and a storage capacitor. Forming a charging path via the light emitting diode unit and the first diode, and forming a discharging path via the second diode, thereby providing a capacitor voltage of a stable state of the storage capacitor, and reducing the series connection to the light emitting diode unit The number of light-emitting diodes inside.

A controllable current limiting unit is used to control the current flowing through the light emitting diode unit and the storage capacitor. The storage capacitor has a charging phase and the above-described controllable current limiting unit should not be turned on during the charging phase. If the AC input voltage is 60 Hz, the time gap between the charging period of the storage capacitor and the conduction period of the controllable current limiting unit is at least 13.78 microseconds, and if the AC input voltage is 50 Hz, the time gap is at least 16.53 microseconds.

In a first preferred embodiment of the invention, the light emitting diode unit is connected in series with a controllable current limiting unit controlled by the controller. The positive terminal of the storage capacitor in the voltage charging and discharging unit is connected to the negative terminal of the first diode and the positive terminal of the second diode. In the voltage charging and discharging unit, a current limiting unit grounds the negative terminal of the storage capacitor. The current in the discharge path is discharged from the ground through the parasitic reverse current path of the current limiting unit.

In a second preferred embodiment of the invention, the positive terminal of the storage capacitor is connected to the positive terminal of the second diode and the negative terminal of the storage capacitor is grounded. In the voltage charging and discharging unit, the current limiting unit is connected between the negative terminal of the first diode and the positive terminal of the storage capacitor. Therefore, the current in the discharge path does not need to be discharged via the parasitic reverse current path of the current limiting unit.

In a third preferred embodiment of the present invention, the LED driving circuit has a third diode in addition to the voltage charging and discharging unit, the positive terminal is grounded and the negative terminal is connected to the negative terminal of the storage capacitor to discharge During the phase, current is bypassed beyond the current limiting unit, as in the first preferred embodiment. The current in the discharge path flows through the third diode instead of the parasitic reverse current path of the current limiting unit to reduce power loss.

In a fourth preferred embodiment of the invention, the light emitting diode drive circuit is similar to the third preferred embodiment. However, in the voltage charging and discharging unit, the negative terminal of the storage capacitor is connected to the above-described current limiting unit via the fourth diode so that the current in the discharge path does not flow through the current limiting unit at all.

In a fifth preferred embodiment of the present invention, the controllable current limiting unit connected to the light emitting diode unit is replaced by a switch and a first current limiting unit to turn the switch on or off with a controller. Further, in the voltage charging and discharging unit, a second current limiting unit is connected between the positive terminal of the storage capacitor and the positive terminal of the second diode, and the negative terminal of the storage capacitor is connected to the first current limiting unit. Not grounded. As a result, the current in the discharge path is discharged through a discharge circuit through the above-described switch, and does not pass through the ground.

In a sixth preferred embodiment of the invention, the controllable current limiting unit connected to the light emitting diode unit is also replaced by a switch and a first current limiting unit, similar to the fifth preferred embodiment. However, in the voltage charging and discharging unit, the second current limiting unit is removed, and the positive terminal of the above second diode is directly connected to the positive terminal of the storage capacitor.

Further, a third diode is connected from the ground terminal to the negative terminal of the storage capacitor, and a fourth diode is connected from the negative terminal of the storage capacitor to the first current limiting unit. In other words, in the sixth preferred embodiment, the charging and discharging paths share the first current limiting unit described above.

The present invention is provided with the accompanying drawings in which the invention may be further understood and The drawings illustrate embodiments of the invention and, together with

Fig. 1A is a block diagram showing a light-emitting diode driving circuit using a high input voltage according to a first preferred embodiment of the present invention. In the present embodiment, the LED driving circuit includes a light emitting diode unit 101 having a plurality of light emitting diodes connected in series and powered by a rectified AC voltage of an AC input voltage. The light emitting diode unit 101 has a positive terminal connected to the rectified AC voltage, and a negative terminal connected to a controllable current limiting unit 102 controlled by the controller 103 and connected to the ground.

The light emitting diode unit 101 is coupled to the voltage charging and discharging unit 100, and the voltage charging and discharging unit 100 includes at least two diodes D1 and D2 and a storage capacitor 104. As shown in Fig. 1A, the diode D1 has a positive terminal connected to the negative terminal of the LED unit 101, and a negative terminal connected to the positive terminal of the storage capacitor 104. The diode D2 has a negative terminal connected to the positive terminal of the light emitting diode unit 101, and a positive terminal connected to the positive terminal of the storage capacitor 104. In the voltage charging and discharging unit 100, the storage capacitor 104 has a negative terminal connected to a current limiting unit 105 connected to the ground.

FIG. 1B shows a charging path and a discharging path of the light emitting diode driving circuit. For the sake of simplicity, in the following description, it is assumed that both diodes D1 and D2 are ideal diodes with zero forward voltage. When the rectified AC voltage is greater than the forward voltage across the LED unit 101 plus the voltage of the storage capacitor 104, the storage capacitor 104 is charged, so the voltage of the storage capacitor 104 is increased. The charging current flows through a charging path formed by the light emitting diode unit 101, the diode D1, the storage capacitor 104, and the current limiting unit 105 that limits the magnitude of the charging current.

When the rectified AC voltage is less than the voltage of the storage capacitor 104, the voltage at the positive terminal of the LED unit 101 is the same as the capacitor voltage. At this time, if the controllable current limiting unit 10 2 is turned on, the storage capacitor 104 is discharged, and the capacitor voltage will drop as it discharges. The discharge current flows through the parasitic reverse current path including the current limiting unit 105, the discharge path of the storage capacitor 104, the diode D2, the light emitting diode unit 101, and the controllable current limiting unit 102. If the controllable current limiting unit 10 2 is turned off, the voltage of the storage capacitor 104 will remain unchanged.

In the present invention, as shown in FIG. 2, the storage capacitor 104 is charged and discharged in accordance with the on and off of the controllable current limiting unit 10 2, and thus the voltage of the storage capacitor 104 reaches a steady state. When the rectified AC voltage is increased to a point where its voltage value is greater than the forward voltage V _LED across the _LED unit 101 plus the voltage V _cap,low of the storage capacitor 104, the storage capacitor 104 enters charging. At the stage, until the rectified AC voltage is reduced to a point where the voltage value is less than the forward voltage across the LED unit 101 plus the voltage V _cap,high of the storage capacitor 104. At this time, the storage capacitor 104 enters the hold phase.

When the rectified AC voltage continues to drop to the voltage value at the positive terminal of the LED unit 101, which is the same as the C point of the voltage V _cap,high of the storage capacitor 104, the storage capacitor 104 enters the discharge phase until the rectified AC The voltage is increased to be greater than the capacitor voltage V _cap,low , which is point D. At this time, the voltage value on the positive terminal of the light-emitting diode unit 101 is the same as the rectified AC voltage.

From the steady state voltage map of the storage capacitor 104 shown in FIG. 2, it can be seen that if the controllable current limiting unit 102 is turned on when or after the rectified AC voltage reaches the C point, the storage capacitor 104 starts to discharge into the discharge. stage. If the controllable current limiting unit 102 is turned off when or after the rectified AC voltage reaches the D point, the storage capacitor 104 stops discharging and enters the holding phase.

FIG. 3 shows another steady state voltage map of the storage capacitor 104. 2 is different from the steady state voltage diagram of FIG. 3 in that the controllable current limiting unit 102 is turned on and off. As shown in FIG. 3, the controllable current limiting unit 102 is turned on after the rectified AC voltage reaches C point, causes the storage capacitor 104 to enter the discharge phase, and is turned off before the rectified AC voltage reaches the D point, so that the storage capacitor is turned off. 10 4 Enter the hold phase.

It can be understood that the controllable current limiting unit 102 can also be turned on when the rectified AC voltage reaches the C point or before, so that the storage capacitor 104 enters the discharge phase, and is turned off before the rectified AC voltage reaches the D point, so that The storage capacitor 10 4 enters the hold phase. Similarly, the controllable current limiting unit 102 can also be turned on after the rectified AC voltage reaches C point, so that the storage capacitor 104 enters the discharge phase, and is turned off when the rectified AC voltage reaches the D point or after, so that the storage Capacitor 10 4 enters the hold phase.

If the rectified AC voltage reaches C point, the controllable current limiting unit 102 is turned on, causing the storage capacitor 104 to enter the discharge phase, or the controllable current limiting unit 102 is turned off after the rectified AC voltage has reached D point. The storage capacitor 104 is brought into the hold phase because the conduction of the controllable current limiting unit 102 causes a higher voltage to straddle the controllable current limiting unit 102, that is, the negative terminal of the LED unit 10 1 High voltages, which also result in higher power losses. The advantage of the above higher power loss is that the circuit design of the controller 103 can be simplified.

According to the present invention, in order to satisfy the state of charge in the LED driving circuit shown in FIG. 1, the peak voltage V _{AC ,peak of the} rectified AC voltage must be greater than the forward voltage V _{LED of the LED} unit 101 plus The voltage V _{CAP of the} storage capacitor 104, that is, V _{AC , peak} >= V _LED + V _CAP . On the other hand, in order to satisfy the discharge state, the voltage V _{CAP of the} storage capacitor 104 must be larger than the forward voltage of the light-emitting diode unit 101, that is, V _CAP >= V _LED .

From the two voltage conditions described above, V _{AC , peak} >= V _LED + V _LED can be derived, that is, V _LED <= V _{AC , peak} / 2. It can be seen that, after the voltage charging and discharging unit 100 is coupled to the light emitting diode unit 101 according to the present invention, the number of light emitting diodes of the light emitting diode unit 101 in the light emitting diode driving circuit of FIG. Can be reduced. In other words, the rectified AC voltage is applied to the general-purpose LED driving circuit of the LED unit 101 compared to the voltage charging and discharging unit 100 of the present invention, and the present invention is in the LED unit 101. The number of light-emitting diodes inside is only half.

It is worth noting that if the number of light-emitting diodes in the light-emitting diode unit 10 1 is excessively reduced, two cases may occur. In the first case, the capacitor voltage V _CAP is slightly larger than the forward voltage V _{LED of the} light-emitting diode unit 101. In this case, the power loss during discharge is low, but charging causes excessive power loss. In order to reduce the power loss of charging, an additional light-emitting diode 401 may be connected in series between the rectified AC voltage and the light-emitting diode unit 101 as shown in FIG. 4A.

In the second case, the capacitor voltage V _CAP is slightly smaller than V _{AC , peak} -V _LED , in which case the storage capacitor 104 is charged to a higher voltage, the power loss due to charging is low, but the discharge is Will cause excessive power loss. In order to reduce the power loss of the discharge, an additional light-emitting diode 402 may be inserted in series between the negative terminal of the light-emitting diode unit 101 and the controllable current limiting unit 102 as shown in FIG. 4B.

In both cases, if the forward voltage of the additional _LED is V _{LED , extra} , the driver circuit needs to meet the condition V _LED + V _{LED , extra} <= V _{AC , peak} -V _LED . Additional cost is required because of the need to reduce power loss and maintain the efficiency of the LED driver circuit as additional LEDs as shown in Figures 4A and 4B. Therefore, excessively reducing the number of light-emitting diodes in the light-emitting diode unit 101 may increase rather than reduce the total cost of the light-emitting diode driving circuit.

In the present invention, in the worst case, the total number of light-emitting diodes connected in series in the light-emitting diode unit 101 and the additional light-emitting diodes is preferably in an optimum state, that is, as described above. When the V _LED <= V _{AC , peak} / 2, the number of light-emitting diodes is increased by no more than 80%. In other words, in the worst case conditions, it is best to comply with V _LED + V _{LED , extra} = 1.8 * V _{AC , peak} / 2 = 0.9 * V _{AC , peak} . Under these conditions, V _LED > = V _AC can be derived _{and peak} / 10 must be satisfied. Therefore, assuming that the forward voltage of each of the light-emitting diodes is V _{F ,} the number of light-emitting diodes N _LEDs connected in series in the light-emitting diode unit 101 must be within the range expressed as follows: <= N _LED <= , among them It is the lower limit integer of x .

According to the present invention, in order to avoid excessive power loss, when the voltage value on the negative terminal of the light-emitting diode unit 101 becomes too high, the controllable current limiting unit 102 must be turned off. Therefore, after the voltage of the storage capacitor 104 has reached a steady state, the operation of the controller 103 must satisfy two conditions of the control signal of the controllable current limiting unit 102 as shown in FIG.

The first condition is that the controllable current limiting unit 102 must be turned off during the charging phase of the storage capacitor 104. In other words, the switching time of the on and off of the controllable current limiting unit 102 must occur during the holding phase of the storage capacitor 104. As shown in Fig. 5, the control signal must turn off the controllable current limiting unit 102 before the rectified AC voltage reaches point A, and the rectified AC voltage reaches the point B and then turn on the controllable current limiting unit 102. It can be seen that the conduction period of the controllable current limiting unit 102 cannot overlap with the charging phase of the storage capacitor 104.

The second condition is that the above non-overlapping time must be large enough to reduce the power loss due to the holding phase of the capacitor 104. Based on the extra power loss caused by the worst condition that the non-overlapping time is zero, the non-overlap time in the present invention must be large enough to at least reduce the excess power loss caused by the worst-case condition above 10%. It is good.

Since the power loss caused by the holding phase of the storage capacitor 104 is proportional to the shaded area shown in FIG. 5, it can be seen that the lower the voltage of the storage capacitor 104, the shorter the hold phase time and the smaller the shadow area. The lower capacitor voltage also means that the number of light emitting diodes connected in series in the light emitting diode unit 101 can be small. Therefore, the lower limit of the non-overlapping time in the present invention is determined by V _CAP = V _LED = V _{AC , peak} / 10 .

For the sake of simplicity, the shaded area shown in Figure 5 can be approximated as a triangle. In the case of an AC input voltage of 60 Hz, the lower limit of the time of non-overlap is approximately equal to 13.78 microseconds. If the AC input voltage is 50 Hz, the lower limit of the time of non-overlap is approximately equal to 16.53 microseconds.

Fig. 6A is a block diagram showing a light emitting diode driving circuit using a high input voltage in accordance with a second preferred embodiment of the present invention. In this embodiment, the LED driving circuit includes a light emitting diode unit 610 having a plurality of light emitting diodes connected in series and powered by a rectified AC voltage of an AC input voltage. Similar to the first preferred embodiment shown in FIG. 1A, the LED unit 610 has a positive terminal connected to the rectified AC voltage, and a negative terminal connected to a controllable by the controller 603 and connected to the ground. Current limiting unit 602.

The positive and negative terminals of the LED unit 601 are connected to the two diodes D1 and D2. As shown in Fig. 6A, similar to Fig. 1A, the diode D1 has a positive terminal connected to the negative terminal of the light-emitting diode unit 601, and a negative terminal connected to one end of the current limiting unit 605. The diode D2 has a negative terminal connected to the positive terminal of the LED unit 601. The positive terminal of the storage capacitor 604 is connected to the positive terminal of the diode D2 and the other terminal of the current limiting unit 605, and the negative terminal of the storage capacitor 604 is connected to the ground.

As can be seen from Fig. 6A, in the voltage charging and discharging unit 600 of the second preferred embodiment, the current limiting unit 605 is connected between the negative terminal of the first diode D1 and the positive terminal of the storage capacitor 604. Therefore, the current in the discharge path does not need to flow through the parasitic reverse current path of the current limiting unit.

Fig. 6B shows the charging path and the discharging path of the light emitting diode driving circuit of the second preferred embodiment shown in Fig. 6A. As shown in FIG. 6B, the charging path of the storage capacitor 604 is formed by the light emitting diode unit 601, the diode D1, the current limiting unit 605, and the storage capacitor 604. The discharge path includes a storage capacitor 604, a diode D2, a light emitting diode unit 601, and a controllable current limiting unit 602.

This embodiment has the advantage that since the negative terminal of the storage capacitor 604 is grounded, the discharge path does not depend on the parasitic reverse current path of the current limiting unit 605, thereby reducing power loss in discharge.

Fig. 7A is a block diagram showing a light emitting diode driving circuit using a high input voltage in accordance with a third preferred embodiment of the present invention. In the present embodiment, the light emitting diode driving circuit is almost the same as the first preferred embodiment shown in Fig. 1A except for the diode D3 which is added in the voltage charging and discharging unit 700.

The LED driving circuit includes a light emitting diode unit 701 having a plurality of LEDs connected in series and powered by a rectified AC voltage of an AC input voltage, and a controllable current limiting unit 702 controlled by the controller 703, storing Capacitor 704 and current limiting unit 705. In addition to the diodes D1 and D2 of the first preferred embodiment shown in Fig. 1A, the diode D3 is connected from the ground terminal to the negative terminal of the storage capacitor 704 in parallel with the current limiting unit 705.

Fig. 7B shows the charging path and the discharging path of the light emitting diode driving circuit of the third preferred embodiment shown in Fig. 7A. As shown in Fig. 7B, the charging path of the storage capacitor 704 is the same as the charging path shown in Fig. 1B. However, the discharge path is composed of a diode D3, a storage capacitor 704, a diode D2, a light-emitting diode unit 701, and a controllable current limiting unit 702.

This embodiment has the advantage that since the diode D3 is present in the voltage charging and discharging unit 700, the discharge current flowing through the parasitic reverse current path of the current limiting unit 705 is reduced, thereby reducing the power loss in the discharge.

Fig. 8A is a block diagram showing a light emitting diode driving circuit using a high input voltage in accordance with a fourth preferred embodiment of the present invention. This embodiment is very similar except that a diode D4 is added between the negative terminal of the storage capacitor 804 and the current limiting unit 085 in the voltage charging and discharging unit 800, and the diode D3 is connected to the negative terminal of the storage capacitor 840. A third preferred embodiment shown in FIG.

Fig. 8B shows the charging path and the discharging path of the light emitting diode driving circuit of the fourth preferred embodiment shown in Fig. 8A. It can be seen that the charging path of the storage capacitor 840 is formed by the LED unit 801, the diode D1, the storage capacitor 804, the diode D4, and the current limiting unit 805. The discharge path of the storage capacitor 804 includes a diode D3, a storage capacitor 804, a diode D2, a light emitting diode unit 801, and a controllable current limiting unit 802. The controller 803 controls the controllable current limiting unit 802 to charge and discharge the storage capacitor 804. Diode D4 prevents the discharge current from flowing through the parasitic reverse current path of current limiting unit 850.

Fig. 9A is a block diagram showing a light emitting diode driving circuit using a high input voltage in accordance with a fifth preferred embodiment of the present invention. In this embodiment, the LED driving circuit includes a light emitting diode unit 901 having a plurality of light emitting diodes connected in series and powered by a rectified AC voltage of an AC input voltage. The light emitting diode unit 901 has a positive terminal connected to the rectified AC voltage, and a negative terminal connected to the first terminal of the switch 906 controlled by the controller 903, and the first current limiting unit 902 is connected to the second switch 906. Between the terminal and the ground.

The positive and negative terminals of the LED unit 901 are further connected to the negative terminal of the diode D2 and the positive terminal of the diode D1, respectively. In the voltage charging and discharging unit 900, a second current limiting unit 905 is connected between the positive terminal of the diode D2 and the negative terminal of the diode D1. The positive terminal of the storage capacitor 904 is connected to the negative terminal of the diode D1, and the negative terminal of the storage capacitor 904 is connected to the second terminal of the switch 906 connected to the current limiting unit 902.

Fig. 9B shows the charging path and the discharging path of the light emitting diode driving circuit shown in Fig. 9A. The charging path of the storage capacitor 904 is formed by the light emitting diode unit 901, the diode D1, the storage capacitor 904, and the first current limiting unit 902. The discharge path is formed by a second current limiting unit 905, a diode D2, a light emitting diode unit 901, a switch 906 and a storage capacitor 904. It should be noted that the discharge path in the fifth preferred embodiment is a discharge circuit, and the switch 906 is controlled by the controller 903 to form a discharge circuit without passing through the ground.

Fig. 10A is a block diagram showing a light emitting diode driving circuit using a high input voltage in accordance with a sixth preferred embodiment of the present invention. In the present embodiment, the LED driving circuit includes a light emitting diode unit 1001 having a plurality of light emitting diodes connected in series and powered by a rectified AC voltage of an AC input voltage. The light emitting diode unit 1001 has a positive terminal connected to the rectified AC voltage, and a negative terminal connected to the first terminal of the switch 1006 controlled by the controller 1003, and a current limiting unit 1002 connected to the second switch 1006. Between the terminal and the ground.

In the sixth preferred embodiment, the positive and negative ends of the light emitting diode unit 1001 are also connected to the negative terminal of the diode D2 and the positive terminal of the diode D1, respectively. However, in the voltage charging and discharging unit 1000 in this embodiment, the second current limiting unit 905 in FIG. 9A is removed, and the positive terminal of the diode D2 is directly connected to the positive terminal of the storage capacitor 1004 and the negative of the diode D1. end. The negative terminal of the storage capacitor 1004 is connected to the negative terminal of the diode D3 and the positive terminal of the diode D4. The negative terminal of diode D4 is coupled to the second terminal of switch 1006, and the positive terminal of diode D3 is coupled to ground.

Fig. 10B shows the charging path and the discharging path of the light emitting diode driving circuit shown in Fig. 10A. The charging path of the storage capacitor 1004 is formed by the light emitting diode unit 1001, the diode D1, the storage capacitor 1004, the diode D4, and the current limiting unit 1002. The discharge path is formed by a diode D3, a storage capacitor 1004, a diode D2, a light emitting diode unit 1001, a switch 1006, and a current limiting unit 1002. It should be noted that in the sixth preferred embodiment, the charging and discharging paths share the same current limiting unit 100 2 , and the controller 1003 controls the switch 1006 to form a discharge path.

Although the invention has been described above by way of a few preferred embodiments, it will be apparent to those skilled in the art that Within the scope of the patent application.

100:600:700:800:900:1000‧‧‧Voltage charging and discharging unit

101:601:701:801: 901:1001‧‧‧Lighting diode unit

102:602:702:802‧‧‧Controllable current limiting unit

103:603:703:803: 903:1003‧‧‧ controller

104:604:704:804: 904:1004‧‧‧ Storage capacitors

105:605:705:805:902:905:1002‧‧‧ Current Limit Unit

401:402‧‧‧Lighting diode

906:1006‧‧‧Switch

Fig. 1A is a block diagram showing a light emitting diode driving circuit using a high input voltage according to a first preferred embodiment of the present invention. Fig. 1B shows the charging and discharging paths of the light emitting diode driving circuit shown in Fig. 1A. Fig. 2 is a view showing a steady state voltage diagram of a storage capacitor in the light emitting diode driving circuit shown in Fig. 1A, including phases of charging, holding, and discharging. Fig. 3 is a view showing another steady state voltage diagram of the storage capacitor in the light emitting diode driving circuit shown in Fig. 1A, including stages of charging, holding, and discharging. 4A shows that an additional light-emitting diode can be added between the rectified AC voltage of the LED driving circuit shown in FIG. 1A and the positive terminal of the LED unit to reduce excessive charging. Power loss. FIG. 4B illustrates that an additional light emitting diode can be added between the negative terminal of the light emitting diode unit and the controllable current limiting unit of the light emitting diode driving circuit shown in FIG. 1A to reduce excessive discharge. Power loss. 5 is a steady state voltage diagram of the LED driving circuit shown in FIG. 1A, a control signal of the controllable current limiting unit, and a period between the conduction period of the controllable current limiting unit and the charging phase of the storage capacitor. The time of overlap. Fig. 6A is a block diagram showing a light emitting diode driving circuit using a high input voltage in accordance with a second preferred embodiment of the present invention. Fig. 6B shows the charging and discharging paths of the light emitting diode driving circuit shown in Fig. 6A. Fig. 7A is a block diagram showing a light emitting diode driving circuit using a high input voltage in accordance with a third preferred embodiment of the present invention. Fig. 7B shows the charging and discharging paths of the light emitting diode driving circuit shown in Fig. 7A. Fig. 8A is a block diagram showing a light emitting diode driving circuit using a high input voltage in accordance with a fourth preferred embodiment of the present invention. Fig. 8B shows the charging and discharging paths of the light emitting diode driving circuit shown in Fig. 8A. Fig. 9A is a block diagram showing a light emitting diode driving circuit using a high input voltage in accordance with a fifth preferred embodiment of the present invention. Fig. 9B shows the charging and discharging paths of the light emitting diode driving circuit shown in Fig. 9A. Fig. 10A is a block diagram showing a light emitting diode driving circuit using a high input voltage in accordance with a sixth preferred embodiment of the present invention. Fig. 10B shows the charging and discharging paths of the light emitting diode driving circuit shown in Fig. 10A.

Claims (18)

A light emitting diode driving circuit comprises: a light emitting diode unit, wherein a plurality of light emitting diodes are connected in series, wherein the light emitting diode unit has a positive end and a negative end; and a controllable current limiting unit has a first One end is connected to the negative end of the light emitting diode unit, and the second end is connected to the ground; a controller controls the controllable current limiting unit; a voltage charging and discharging unit is coupled to the light emitting diode unit, the voltage The charging and discharging unit at least includes: a storage capacitor having a positive terminal and a negative terminal; the first diode having a positive terminal and a negative terminal, the positive terminal of which is connected to the negative terminal of the light emitting diode unit; the second diode has a positive terminal connected to the positive terminal of the storage capacitor, and a negative terminal connected to the positive terminal of the light emitting diode unit; a charging path to the ground via the first diode and the storage capacitor; and a storage capacitor via the storage capacitor And a discharge path of the second diode; and an alternating current input voltage having a rectified alternating voltage connected to the positive terminal of the light emitting diode unit . The illuminating diode driving circuit of claim 1, wherein a negative terminal of the first diode is connected to a positive terminal of the storage capacitor, and a charging path of the voltage charging and discharging unit further includes a current The limiting unit has a first terminal connected to the negative terminal of the storage capacitor and a second terminal connected to the ground. The illuminating diode driving circuit of claim 2, wherein the discharge path of the voltage charging and discharging unit further comprises a third diode having a positive terminal connected to the ground and a negative terminal connected to the storage capacitor. Terminal. The illuminating diode driving circuit of claim 1, wherein the voltage charging and discharging unit further comprises a current limiting unit having a first end connected to the negative end of the first diode, and a second end Connected to the positive terminal of the storage capacitor, and in the above charging path, the negative terminal of the storage capacitor is connected to the ground. The illuminating diode driving circuit of claim 1, wherein a negative terminal of the first diode is connected to a positive terminal of the storage capacitor, and the voltage charging and discharging unit further comprises: a third diode The tube has a positive terminal connected to the ground, and a negative terminal connected to the negative terminal of the storage capacitor; the fourth diode has a positive terminal and a negative terminal, the positive terminal of which is connected to the negative terminal of the storage capacitor; and a current limiting unit has The first end is connected to the negative terminal of the fourth diode, and the second end is connected to the ground in the charging path. The illuminating diode driving circuit according to claim 1, wherein each of the illuminating diodes in the illuminating diode unit has a forward voltage of V _F and a peak voltage of the rectified AC voltage. V _{AC , peak} , and the total number of light-emitting diodes connected in series in the above-mentioned light-emitting diode unit is less than or equal to That is The lower bound of the integer. The illuminating diode driving circuit of claim 6, wherein the total number of the illuminating diodes connected in series in the illuminating diode unit is greater than or equal to That is The lower bound of the integer. The illuminating diode driving circuit of claim 1, wherein the storage capacitor has a charging phase, and the controllable current limiting unit is not turned on during the charging phase. The illuminating diode driving circuit of claim 8, wherein the AC input voltage is 60 Hz, and a time interval between a charging phase of the storage capacitor and a conducting period of the controllable current limiting unit is at least 13.78 microseconds. The illuminating diode driving circuit of claim 8, wherein the alternating current input voltage is 50 Hz, and a time interval between a charging phase of the storage capacitor and a conducting period of the controllable current limiting unit is at least 16.53 microseconds. A light emitting diode driving circuit comprises: a light emitting diode unit, wherein a plurality of light emitting diodes are connected in series, wherein the light emitting diode unit has a positive terminal and a negative terminal; and a switch has a first terminal and a first a second terminal having a first terminal connected to the negative terminal of the light emitting diode unit; a controller controlling the switch; the first current limiting unit having a first end connected to the second terminal of the switch, and the second end connected to a voltage charging and discharging unit coupled to the light emitting diode unit, wherein the voltage charging and discharging unit comprises at least: a storage capacitor having a positive terminal and a negative terminal; the first diode having a positive terminal connected to the light emitting diode a negative terminal of the body unit, and a negative terminal connected to the positive terminal of the storage capacitor; a second diode having a positive terminal and a negative terminal, the negative terminal of which is connected to the positive terminal of the light emitting diode unit; a diode, a storage capacitor, and a charging path grounded by the first current limiting unit; and a via the storage capacitor and the second diode Electrical path; and a positive AC input voltage having a rectified AC voltage terminal is connected to the light emitting diode units. The illuminating diode driving circuit of claim 11, wherein the voltage charging and discharging unit further comprises a second current limiting unit having a first terminal connected to the positive terminal of the storage capacitor, and the second end connected to the second terminal The positive terminal of the second diode, and in the charging path, the negative terminal of the storage capacitor is connected to the first end of the first current limiting unit. The illuminating diode driving circuit of claim 11, wherein a positive terminal of the second diode is connected to a positive terminal of the storage capacitor, and the voltage charging and discharging unit further comprises: a third diode The tube has a positive terminal connected to the ground, and a negative terminal connected to the negative terminal of the storage capacitor; and a fourth diode having a positive terminal connected to the negative terminal of the storage capacitor, and a negative terminal connected to the first current limiting unit First end. The illuminating diode driving circuit of claim 11, wherein each of the illuminating diodes in the illuminating diode unit has a forward voltage of V _F and a peak voltage of the rectified AC voltage V _{AC , peak} , and the total number of light-emitting diodes connected in series in the above-mentioned light-emitting diode unit is less than or equal to That is The lower bound of the integer. The illuminating diode driving circuit of claim 14, wherein the total number of the illuminating diodes connected in series in the illuminating diode unit is greater than or equal to That is The lower bound of the integer. The illuminating diode driving circuit of claim 11, wherein the storage capacitor has a charging phase, and the switch is not turned on during the charging phase. The illuminating diode driving circuit of claim 16, wherein the alternating current input voltage is 60 Hz, and the time interval between the charging phase of the storage capacitor and the conducting period of the switch is at least 13.78 microseconds. The illuminating diode driving circuit of claim 16, wherein the alternating current input voltage is 50 Hz, and a time interval between a charging phase of the storage capacitor and an on period of the switch is at least 16.53 microseconds.