TWI455639B - High-frequency led device driving circuit - Google Patents

Description

High frequency light emitting diode light source driving circuit

The invention relates to the technical field of power sources, in particular to a high frequency light emitting diode light source driving circuit.

Light-emitting diodes (LEDs) are the principle of directly converting electrical energy into light energy. Voltage is applied to the two terminals of the positive and negative electrodes in the semiconductor. When the current passes, the electrons are combined with the holes, and the remaining energy is in the form of light. Release, depending on the material used, its energy level causes the photon energy to produce light of different wavelengths, and the human eye can receive light of various colors.

The principle of illumination of a light-emitting diode is to utilize the inherent characteristics of a semiconductor, which is different from the principle of illumination of an incandescent lamp, so that the light-emitting diode is called a cold light. The light-emitting diode has the advantages of high durability, long life, light weight, low power consumption, and the like, and does not contain harmful substances such as mercury. Therefore, the lighting market today has great expectations for the illumination of the LED.

1 is a voltage-current characteristic curve of a light-emitting diode. As shown in FIG. 1, when the forward voltage Vf applied to the light-emitting diode is greater than 2.5 volts, the light-emitting diode is turned on, and the forward voltage Vf is less than 2.0 volts. Does not shine. As can be seen from FIG. 1, the forward voltage Vf is preferably 2.5 to 3.0 volts, and the current of the light emitting diode is 20 mA to 30 mA. At the same time, as can be seen from FIG. 1, when the voltage applied to the light-emitting diode is too large, the light-emitting diode is damaged. Therefore, when the light-emitting diode is used, a plurality of light-emitting diodes are often connected in series such that the forward voltage Vf of each of the light-emitting diodes is between 2.5 and 3.0 volts. Due to the voltage and current and the plurality of light-emitting diodes connected in series, when applied, the applied external voltage needs to be greater than a so-called starting voltage, and the entire series of light-emitting diodes emit light.

Figure 2 is a schematic illustration of the use of a conventional light emitting diode. An AC power source 21, a first group of LEDs 22, and a second group of LEDs 23 are provided, and the first group of LEDs 22 and the second group of LEDs 23 have a starting voltage of 90 volts. .

When the output AC voltage output by the AC power source 21 is equal to or greater than 90 volts, the lighting of the first group of LEDs 22 is started. When the output AC voltage continues to rise and drops back to 90 volts, the first group of LEDs 22 is turned off. Similarly, when the output AC voltage is equal to or less than -90 volts, the second group of LEDs 23 is started to be turned on. When the output AC voltage continues to drop and rises to -90 volts, the second group of LEDs 23 is turned off.

Referring to FIG. 3, the current waveform diagram of FIG. 2 is shown, wherein the horizontal axis is time, which is displayed in voltage phase, and the vertical axis is current in mA (milliampere). As shown in FIG. 3, at a phase of about 30 degrees, the voltage begins to be greater than 90V, and the first group of LEDs 220 are illuminated. At a phase of about 90 degrees, the voltage is turned to a maximum value, and the current flowing through the first group of light-emitting diodes 22 is about 5.2 mA. When the phase is 150 degrees to 210 degrees, the voltage is less than 90V and greater than -90V. At this time, the first group of LEDs 220 and the second group of LEDs 23 are turned off, so the current is 0 mA. At a phase of about 210 degrees, the voltage begins to be less than -90V, and the second group of light-emitting diodes 23 is illuminated. At a phase of about 270 degrees, the voltage is turned to a minimum value, and the current flowing through the second group of light-emitting diodes 23 is about -5.2 mA. When the phase is 330 degrees to 360 degrees, the voltage is less than 90V and greater than -90V. At this time, the first group of LEDs 22 and the second group of LEDs 23 are turned off, so the current is 0 mA.

Figure 4 is a schematic illustration of another conventional use of a light emitting diode. A 60 Hz alternating current is passed through a bridge rectifier 41 to produce an input DC voltage that is passed through the full bridge rectification, the input DC voltage having a ripple of about 120 Hz. The input DC voltage is output to a transformer 42. A controller 43 is coupled to the transformer 42 having a switch (not shown) for turning the transformer 42 on or off. The control waveform of the switch is a square wave to reduce switching loss. Since the transformer 42 can only accept an AC input, the switch is turned on or off, which would make the input DC voltage equivalent to an AC for the transformer 42. A diode 44 is coupled to the transformer 42 to rectify the output voltage of the transformer 42.

During the period T1, the diode 44 is turned off, about 0 volts. At this time, the transformer 42 stores energy. During the period T2, the diode 44 is turned on, about 12 volts, at which time the transformer 42 is discharged.

When the switch is turned on or off to on, since the control waveform of the switch is a square wave, a large instantaneous current is generated on the primary side of the transformer 42, so that a large instantaneous voltage is generated on the switch. Therefore, when designing the controller 43, a high pressure resistant process is required, which not only increases the cost, but also easily causes electromagnetic radiation problems. At the same time, the conventional technology uses magnetic components such as the transformer 42 and the inductor 45 to not only increase the cost, but also has the disadvantages of large volume, heavy weight, low efficiency, and easy heat generation, and the transformer 42 is also easy to transmit the transient clutter on the primary side. To the secondary side. The driving technology of the conventional light-emitting diodes still has many defects and needs to be improved.

The object of the present invention is mainly to provide an LED light source driving circuit, which does not need to use magnetic components such as a transformer and an inductor, thereby reducing the cost, and can solve the problem that the magnetic component is bulky, heavy, inefficient, and easy to generate heat in the prior art. At the same time, since no magnetic element such as a transformer is used, when switching, the switching device of the present invention does not need to withstand the back electromotive force of the transformer, so that it can be manufactured by a general process, and it is not necessary to use a high-pressure process manufacturing, thereby further reducing the cost.

According to a feature of the present invention, the present invention provides a high frequency light emitting diode light source driving circuit including a rectifying circuit, a current limiting resistor, a feedback amplifier circuit, a voltage clamping circuit, and a light emitting diode load. , a switching device, and a controller. The rectifier circuit receives an AC power source and rectifies the AC power source into a rectified power source. The current limiting resistor is coupled to the rectifier circuit to receive the rectified power supply to limit the magnitude of the rectified power supply current to generate a current limiting power supply synchronized with the output. The feedback amplifying circuit is connected to the current limiting resistor, and according to the current limiting power source, a feedback voltage is generated. The light-emitting diode load is connected to the rectifier circuit at one end thereof to receive the rectified power source as a driving power source for the light-emitting diode load. The switching device is connected to the other end of the LED load to control whether the driving power source passes the LED load. The controller is connected to the feedback amplification circuit, the voltage clamping circuit and the switching device to control whether the switching device is turned on or not. One end of the voltage clamping circuit is connected to the current limiting resistor and the feedback amplifier circuit, and the other end thereof is connected to a power supply end of the controller, when the current limiting power output of the current limiting resistor is lower than a predetermined voltage The voltage clamping circuit is not turned on, and the power supply to the controller is cut off to make the voltage and current phases the same and the load is approximately resistive, thereby generating the function of the power factor correction.

According to another feature of the present invention, the present invention provides a high frequency light emitting diode light source driving circuit including a rectifying circuit, a light emitting diode load, a voltage dividing circuit, and a controller. The rectifier circuit receives an AC power source and rectifies the AC power source into a rectified power source. The LED load is connected to the rectifier circuit at one end to receive the rectified power source as a driving power source for the LED load. The voltage dividing circuit is coupled to the light emitting diode load to receive a current flowing through the light emitting diode load and generate a divided voltage. The controller is connected to the rectifier circuit, the LED load and the voltage dividing circuit to receive the divided voltage and to control the LED load.

FIG. 5 is a circuit diagram of a high frequency LED light source driving circuit 50 for driving a light emitting diode, a plurality of light emitting diodes, or a light emitting diode module. The LED light source driving circuit 50 includes a rectifying circuit 51, a current limiting resistor 52, a feedback amplifying circuit 53, a light emitting diode load 54, a switching device 55, a controller 56, a sensing circuit 57, and A voltage clamping circuit 58.

The rectifier circuit 51 receives an AC power source and rectifies the AC power source into a rectified power source. The rectifier circuit is a full bridge rectifier circuit and is composed of a first to fourth diodes D1 to D4.

The current limiting resistor 52 is coupled to the rectifier circuit 51 for receiving the rectified power supply to limit the magnitude of the rectified power supply current to generate a current limiting power supply.

The feedback amplifying circuit 53 is connected to the current limiting resistor 52, and generates a feedback voltage Vfb according to the current limiting power supply.

One end of the LED load 54 is connected to the rectifier circuit 51 via a resistor R2 to receive the rectified power source, and the rectified power source is used as a driving power source for the LED load 54.

The switching device 55 is coupled to the other end of the LED load 54 to control whether the driving power source passes through the LED load 54.

In this embodiment, the switching device 55 is an enhanced field effect transistor, which is preferably an N-channel enhancement type field effect transistor (enhanced N-channel FET). When the AC power source is 220 volts, the rectified power supply generated by the rectifier circuit 51 has a peak value of about 264 volts, so most of the voltage falls on the LED load 54, and the voltage on the switching device 55 is very high. It is small, so there is no need to use a high pressure resistant process like the conventional technology. In contrast, conventional techniques, due to the use of the transformer 42, when switched, conventionally known switches are required to withstand the back electromotive force of the transformer 42, and therefore require high pressure manufacturing.

The controller 56 is connected to the feedback amplifying circuit 53, the voltage clamping circuit 58, the switching device 55 and the sensing circuit 57 to control whether the switching device 55 is turned on or not. The feedback voltage waveform should be a DC level. This level passes through the controller 56 to determine the width of the output pulse of the controller 56 pin GATE to provide a stable output energy. The feedback voltage higher than 2.4V indicates that it operates at a fixed frequency, and the feedback voltage is lower than 2.4V to start frequency reduction. If the feedback voltage is lower than 1.4V, it starts to enter a burst mode state. The feedback voltage is usually connected in parallel with a small capacitor C4 to filter out noise so that the controller 56 can obtain a normal comparison level. When the feedback voltage is lower than 1.2V, the controller 56 pin GATE will turn off no output.

The sensing circuit 57 is coupled to the controller 56 and the switching device 55 to sense current flowing through the switching device 55 and to generate a sensing voltage. The sensing circuit is composed of a fourth resistor R4 and a third capacitor C3 to sense the current flowing through the switching device 55 and generate the sensing voltage. The SENSE pin of the controller 56 is mainly used as a closed loop current feedback input pin. The fourth resistor R4 is used to detect the current flowing through the switching device 55, and the sensing voltage is obtained and transmitted to the controller 56. Comparison. The controller 56 switches the conduction of the switching device 55 according to the sensing voltage. One end of the voltage clamping circuit 58 is connected to the current limiting resistor 52 and the feedback amplifying circuit 53, and the other end thereof is connected to the power supply terminal (VDD) of the controller 56. The voltage clamping circuit 58 is preferably a Zener diode.

When the current limiting power output of the current limiting resistor 52 is lower than the breakdown voltage of the Zener diode 58, the Zener diode 58 is not turned on, and the power to the controller 56 is cut off. Supply, so that the voltage and current phases are the same and the load is approximately resistive, and the function of power factor correction (PFC) is generated, because the power supply of the power supply terminal (VDD) of the controller 56 is It is cut off, so the entire controller 56 does not consume power at all. This not only improves the power factor (PF) but also saves power. That is to say, the circuit structure of the present case and the Zener diode 58 can achieve the function of improving the power factor (PF). It can be replaced by a voltage divider resistor or the like.

6 is a schematic diagram of voltage and current measured by the LED load 54 of the present invention. As shown, the AC power source is 60 Hz, 220 volts, and the LED 56 is applied to the LED load. The root-mean-square value (RMS) voltage of 54 is about 177 volts. As shown in the figure, between the line 1 (L1) and the line 2 (L2), the range of the direct current operating voltage of the light-emitting diode load 54 is specified, and the present invention provides a slight increase in the load of the light-emitting diode 54 as shown in the figure. The area marked as A in 6 makes the light generated by the operation of the light-emitting diode load 54 more saturated, and reaches the saturation of the human eye, so even if the light-emitting diode load 54 is not working, as shown in the figure In the area marked 6 in B, the human eye will not feel flickering.

FIG. 7 is a circuit diagram of another embodiment of a high frequency light emitting diode light source driving circuit according to the present invention, comprising a rectifier circuit 71, a light emitting diode load 72, a voltage dividing circuit 73, and a controller 74.

The controller rectifier circuit 71 receives an AC power source and rectifies the AC power source into a rectified power source.

The LED load 72 has one end connected to the rectifier circuit 71 for receiving the rectified power source as a driving power source for the LED load 72. The voltage dividing circuit 73 is connected to the light emitting diode load 72 to receive a current flowing through the light emitting diode load and generate a divided voltage. The controller 74 is connected to the rectifier circuit 71, the LED load 72 and the voltage dividing circuit 73 to receive the divided voltage and to control the LED load 72.

In summary, the present invention does not require the use of magnetic components such as the transformer 42 and the inductor 45 as in the prior art, thereby reducing the cost and solving the conventional method of being bulky, heavy, inefficient, and prone to heat generation. problem. Since the magnetic element such as the transformer 42 and the inductor 45 is not used, the radiation intensity generated is low, and it is easy to pass the radiation test in the EMI test. At the same time, since the transformer 42 is not used, the switching device 55 of the present invention does not need to withstand the counter electromotive force of the transformer 42 when switching, and thus it is not necessary to use a high pressure resistant process.

From the above, it can be seen that the present invention is extremely useful in terms of its purpose, means, and efficacy, both of which are different from those of the prior art. It should be noted that the various embodiments described above are merely illustrative for ease of explanation, and the scope of the invention is intended to be limited by the scope of the claims.

twenty one. . . AC power

twenty two. . . First group of light-emitting diodes

twenty three. . . Second group of light-emitting diodes

41. . . Bridge rectifier

42. . . transformer

43. . . Controller

44. . . Dipole

45. . . inductance

50. . . LED light source driving circuit

51. . . Rectifier circuit

52. . . Current limiting resistor

53. . . Feedback amplifier circuit

54. . . Luminous diode load

55. . . Switching device

56. . . Controller

57. . . Sense circuit

58. . . Voltage clamp circuit

71. . . Rectifier circuit

72. . . Luminous diode load

73. . . Voltage dividing circuit

74. . . Controller

Fig. 1 is a graph showing voltage and current characteristics of a light-emitting diode.

Figure 2 is a schematic illustration of the use of a conventional light emitting diode.

Figure 3 is a diagram showing the current waveform of Figure 2.

Figure 4 is a schematic illustration of another conventional use of a light emitting diode.

Fig. 5 is a circuit diagram of an LED light source driving circuit of the present invention.

Fig. 6 is a schematic view showing the voltage and current of the present invention in the measurement of the load of the light-emitting diode.

Fig. 7 is a circuit diagram showing another embodiment of a light-emitting diode light source driving circuit of the present invention.

50. . . LED light source driving circuit

51. . . Rectifier circuit

52. . . Current limiting resistor

53. . . Feedback amplifier circuit

54. . . Luminous diode load

55. . . Switching device

56. . . Controller

57. . . Sense circuit

58. . . Voltage clamp circuit

Claims (8)

A high frequency light emitting diode light source driving circuit comprises: a rectifying circuit, receiving an alternating current power source, and rectifying the alternating current power source into a rectifying power source; and a current limiting resistor connected to the rectifying circuit to receive the rectifying power source, To limit the magnitude of the rectified power supply current to generate a current limiting power supply; a feedback amplifier circuit connected to the current limiting resistor, according to the current limiting power supply to generate a feedback voltage; a voltage clamping circuit; a pole load, one end of which is connected to the rectifier circuit for receiving the rectified power source as a driving power source for the LED load; a switching device connected to the other end of the LED load to control the driving Whether the power source passes the light emitting diode load; and a controller connected to the feedback amplifying circuit, the voltage clamping circuit and the switching device to control whether the switching device is turned on or not; wherein the voltage clamping circuit One end is connected to the current limiting resistor and the feedback amplifying circuit, and the other end is connected to a power supply end of the controller, when the current limiting resistor outputs the limit When the power supply is lower than a predetermined voltage, the voltage clamping circuit is not turned on, and the power supply to the controller is cut off, so that the phase of the voltage and the current are the same and the load is approximated to the resistance, thereby generating the function of the power factor correction. . The high frequency light emitting diode light source driving circuit according to claim 1, wherein the method further comprises: A sensing circuit is coupled to the controller and the switching device to sense a current flowing through the switching device and generate a sensing voltage. The high frequency light emitting diode light source driving circuit according to claim 2, wherein the controller switches the conduction of the switching device according to the sensing voltage. The high frequency light emitting diode light source driving circuit according to claim 3, wherein the switching device is an enhanced field effect transistor. The high frequency light emitting diode light source driving circuit according to claim 4, wherein the switching device is an N channel enhanced field effect transistor. The high frequency light emitting diode light source driving circuit according to claim 4, wherein the rectifier circuit is a full bridge rectifier circuit and is composed of a first to fourth diode. The high frequency light emitting diode light source driving circuit of claim 4, wherein the sensing circuit is composed of a fourth resistor and a third capacitor to sense a current flowing through the switching device, And generating the sensing voltage. The high frequency light emitting diode light source driving circuit according to claim 2, wherein the voltage clamping circuit is a Zener diode, and the predetermined voltage is a breakdown voltage of the Zener diode.