TW201422045A - High stability LED control circuit - Google Patents

Abstract

A high stability LED control circuit for driving and adjusting the luminance of at least an LED, which is provided with a control chip, a current switch, a sense resistor, a first resistor and a second resistor. The LED is serially connected to the current switch and the sense resistor, wherein one end of the said first resistor is coupled to the LED and the current switch. Another end of the said first resistor is coupled to one end of the second resistor and the control chip. Another end of the said second resistor is coupled to the current switch and the sense resistor. When the voltage across the two terminals of the LED increases, the voltage across the second resistor will increase to compensate the voltage across the sense resistor for reduceing the drive current and achieving the constant power state.

Description

High stability LED control circuit

The invention belongs to the technical field of Light Emitting Diode (LED) power supply devices, in particular to a high stability LED control circuit for supporting TRI-electrode AC switch (TRIAC) dimming. The power is compensated by the external bypass resistor to achieve the power of the LED.

Since LEDs have been used in the lighting market with low power consumption and high efficiency, how to optimize the illumination brightness, illumination uniformity, work efficiency, service life and dimming control of LED lamps has become the goal of various manufacturers. At present, the control circuit of the LED lamp mostly adopts a constant current structure to connect the LED in series with a current switch and a sensing resistor, and adjusts the conduction angle of an external power source by adjusting a brightness of the LED by using a TRIAC. The sensing resistor detects a driving current flowing through the LED to form a voltage drop and feeds back to a control chip to compare the voltage drop and the input external power source to output a high level voltage or a low level voltage to the current switch In order to turn on or off the current switch in time to adjust the space-to-space ratio of the Pulse Width Modulation (PWM) signal, the magnitude of the drive current and the brightness of the LED can be controlled.

However, according to the current/voltage (I/V) characteristic curve of the LED, the LED is not a linear component, that is, the ratio of voltage to current is not proportional. Therefore, the aforementioned dimming method will make the dimming effect inaccurate and cause virtual power consumption due to the inconsistency between the driving voltage and the driving current. And, limited by the working characteristics of the TRIAC, if the pressure of the external power source has passed When the current flowing through the TRIAC is low, the TRIAC will repeatedly switch to the working state, causing the LED to flicker and reduce the illumination quality.

In view of this, how to achieve LED power compensation and TRIAC current support simultaneously with the simplest circuit architecture without additional adjustment of the module, to stabilize the TRIAC dimming effect and limit the LED luminous power to a certain range to enhance the work of the luminaire Quality and stability are the subjects explored by the present invention.

In view of the problems of the prior art, the object of the present invention is to provide a high stability LED control circuit with a simple structure, which uses an external resistor to set a maximum allowable LED current to avoid the influence of noise when the LED is switched by the dimming switch. Improve work quality while reducing costs.

According to the purpose of the present invention, the high-stability LED control circuit is adapted to drive and adjust the brightness of at least one of the light-emitting diodes, and has a rectifier module, a control module and a driving module, and the rectifier module telecommunications An external power supply is connected, the driving module is connected to the rectifier module and the LED, and the control module is connected to the driving module and the LED, and the control module has a control chip and a control chip. a current switch and a sensing resistor, the LED is connected in series with the current switch and the sensing resistor, so that the sensing resistor senses a driving current flowing through one of the LEDs to form a feedback to the control chip a sensing voltage is characterized in that the control module of the high-stability LED control circuit has a first resistor and a second resistor, and the first resistor is coupled to the LED and coupled to the other end. One end of the second resistor and the control chip, and the other end of the second resistor is coupled to the current switch and the sensing resistor. When the voltage across the LED is increased, the voltage across the second resistor will be across. Increase with it The voltage across the sensing resistor is compensated to reduce the driving current to a constant power state.

The rectifier module is coupled to the external power source through a bidirectional three-pole thyristor for receiving and adjusting the phase conduction angle of the external power source to change the driving current of the LED to adjust the illuminating brightness. The control chip is provided with a voltage regulator, a voltage generator, a selector and an operational amplifier, and the voltage regulator is coupled to the output end of the rectifier module, the selector is coupled to the voltage generator, the operational amplifier The positive input terminal is coupled to the selector, the negative input terminal is coupled to the second resistor, and the output terminal is coupled to the current switch.

The high-stability LED control circuit further includes a linear dimming module coupled to the output end of the rectifying module and the selector for detecting the rectified external power source and outputting a detecting voltage to the selector When the detection voltage is greater than an upper limit value, the selector receives a reference voltage of the voltage generator output. When the detection voltage is within the upper limit value and the lower limit value, the drive current will be linear with the detection voltage, so the selector outputs one half of the detection voltage to adjust the drive. Current and linear dimming function. Moreover, when the detection voltage is less than the lower limit value, the selector outputs a shutdown signal to maintain a basic brightness of the LED, thereby enhancing the dimming effect of the bidirectional triode fluid. In other words, the high-stability LED control circuit further includes a holding current module having a third resistor, a fourth resistor, a holding switch and a holding capacitor, and the holding switch is an N-type MOSFET. a N Type Metal Oxide Semiconductor Field Effect Transistor (N-MOSFET), and the third resistor is coupled to the rectifier module at one end and the other The terminal is coupled to the drain of the holding switch, and the source of the holding switch is coupled to the fourth resistor, and the gate is coupled to the voltage regulator and the holding capacitor. When the voltage regulator receives the rectified external power source to generate a hold signal, and the hold switch is received and turned on, the third resistor and the fourth resistor receive the rectified external power source to form at the two ends of the fourth resistor. Dividing pressure for the holding capacitor to charge and discharge to form and output a holding current to the bidirectional triode thyristor fluid, to prevent the TRIAC from repeatedly switching the working state due to insufficient basic current, thus ensuring the normal operation of the bidirectional triode thyristor fluid Avoid the problem of LED flicker, which improves the compatibility of the luminaire with the TRIAC dimmer.

In order to enhance the anti-noise capability of the circuit, the driving module is provided with a voltage stabilizing capacitor, which is connected to the light emitting diode to charge and discharge the driving current.

In summary, the present invention utilizes the external resistor to form a bypass detection point of the LED to instantly adjust the driving current with the input AC signal of the external power source, so that the LED power of the fixed LED is fixed. In the range, the LED's luminous power is prevented from damaging the life of the product as the input AC signal is excessively changed. In addition, the circuit component can be prevented from being damaged due to abnormal large current, forming a short circuit protection. Furthermore, the present invention supports both TRIAC dimming and linear dimming functions, which can greatly improve the lighting quality and meet the needs of use.

In order for your review board to have a clear understanding of the contents of the present invention, please refer to the following description for matching drawings.

1 to 3 are respectively a circuit diagram, a block diagram and a circuit diagram of a first embodiment of the preferred embodiment of the present invention. As shown in the figure, the control circuit 1 of the high stability LED is suitable for use in an LED lamp for driving and adjusting the brightness of the illumination of at least one of the light-emitting diodes 2. The control circuit 1 is provided with a rectifying module 10, a driving module 11, a linear dimming module 12, a holding current module 13 and a control module 14. The rectifier module 10 can be composed of a TRIAC 100 and a bridge rectifier 101. The bridge rectifier 101 is coupled to an external power source 3 via the TRIAC 100 to receive and rectify the external power source 3 to form a half-wave input voltage (V _in ). The driving module 11 is coupled to the bridge rectifier 101 through a diode 111, and is connected to the LED 2 through a voltage stabilizing capacitor 110 to charge and discharge the driving current to enhance the anti-noise capability of the circuit.

The linear dimming module 12 is composed of two voltage dividing resistors 120 and a voltage storage capacitor 121. The holding current module 13 has a third resistor 130 , a fourth resistor 131 , a holding switch 132 , and a holding capacitor 133 . The control module 14 has a control chip 140, a current switch 141, a sensing resistor 142, a first resistor 143 and a second resistor 144, and the control chip 140 has at least VH, VDD, LD, CS, GATE. A 6-signal pin, such as GND, is provided with a high voltage linear one regulator 1400, a voltage generator 1401, a selector 1402, an operational amplifier 1403, and an overvoltage protector 1404. The pair of voltage dividing resistors 120 are connected in series with each other and coupled to the bridge rectifier 101. The series connection is coupled to the voltage storage capacitor 121 and the LD pin of the control chip 140 is coupled to the selector 1402. The holding switch 132 is an N-MOSFET, and the drain is connected in series with the third resistor 130 and coupled to the bridge rectifier 101. The source of the holding switch 132 is coupled to the fourth resistor 131, and the gate is coupled to the gate. The capacitor 133 and the VDD pin of the control chip 140 are coupled to the regulator 1400.

The current switch 141 is an N-MOSFET, and the drain is coupled to the LED 2 and the first resistor 143. The source is coupled to the sensing resistor 142 and the second resistor 144, and the gate thereof is transmitted through the control. The GATE pin of the chip 140 is coupled to the operational amplifier 1403 and the overvoltage protector 1404. The first resistor 143 is connected in series with the second resistor 144, and the serial connection is coupled to the negative input terminal of the operational amplifier 1403 through the CS pin of the control chip 140. The voltage regulator 1400 is connected to the driver module 11 through the VH pin. The selector 1402 is coupled to the voltage generator 1401, and the positive input terminal of the operational amplifier 1403 is coupled to the selector 1402. Thus, a negative feedback circuit is formed.

When the user adjusts the illumination brightness of the LED lamp, the TRIAC 100 changes the phase conduction angle of the external power source 3, and changes the signal waveform outputted by the bridge rectifier 101 to affect the driving current. And the voltage regulator 1400 receives the rectified external power source 3, and then steps down and stabilizes the external power source 3 to generate a high voltage level one of the hold signals for triggering the remaining internal circuits of the control chip 140 and the The current module 13 is used. When the holding current module 13 receives the holding signal, the holding switch 132 is turned on, so that the third resistor 130 and the fourth resistor 131 receive the input voltage, and a voltage is divided across the fourth resistor 131. The holding capacitor 133 is charged and discharged to form a holding current, and is output to the TRIAC 100 to ensure normal operation and improve the working stability of the LED lamp. Incidentally, in order to satisfy different specifications of the TRIAC 100, it is applicable to various types of LED lamps, and the current (I _TRIAC ) of the TRIAC 100 can be adjusted through the fourth resistor 131, and the actual measurement is shown in FIG. 4A. When the current is 5 mA when the fourth resistor 131 is used, and the current is 8 mA when the voltage is 0.9 KΩ, the smaller the resistance of the fourth resistor 131 is, the larger the current of the TRIAC 100 is.

Furthermore, the linear dimming module 12 detects the input voltage and outputs a detection voltage (LD) to the selector 1402, and the voltage generator 1401 generates a reference voltage of 0.75V to the selector. 1402. Since the detection voltage is affected by the original or dimming of the external power source 3, as shown in FIG. 5, when the detection voltage is greater than an upper limit value such as 1.5V, the selector The 1402 outputs the reference voltage such that the across-voltage (VS) across the sense resistor 142 is fixed at 0.75 V to stabilize the drive current. When the detection voltage is within the upper limit value and the lower limit value of 0.3V, one half of the detection voltage is outputted for linearly adjusting the light-emitting brightness of the light-emitting diode 2 to reinforce and retouch the TRIAC 100. The dimming effect. Moreover, when the detection voltage is less than the lower limit value, the TRIAC 100 enters a closed state, and the selector 1402 outputs a shutdown signal to fix the VS to a voltage value of 0.1 V, so that the driving current retains a basic value while maintaining The basic brightness of the LED 2 makes the dimming effect of the TRIAC 100 softer.

The sensing resistor 142 senses the driving current flowing through the LED 2 to form a feedback voltage to the sensing amplifier 1403 at both ends, so that the control chip 140 turns on or off according to the sensing voltage. The current switch 123 regulates the drive current. In this embodiment, when the number of strings of the LEDs 2 changes or the external power source 3 is pulled up to 70 V of FIG. 6B as shown in FIG. 6A, the voltage across the LEDs 2 increases. And the driving current is increased to increase the voltage across the current switch 141 and the sensing resistor 142 (VD). At this time, the control wafer 140 is still working normally and the VS is fixed at 0.75 V, so that the driving current flowing through the first resistor 143 and the second resistor 144 is increased, and the voltage across the second resistor 144 is increased across the voltage. The VS voltage value is reduced by compensating for the voltage of the sensing voltage. Ikeshoff's law V=I. R knows that when the resistance of the sense resistor 142 is fixed and the VS voltage value is lowered, the drive current (I _Rcs ) flowing through the sense resistor is reduced. In other words, when the voltage across the LED 2 rises, the driving current actually drops, so that the control circuit 1 achieves the power compensation effect, and the actual power supply 3 is pulled up by 70V. At 90V, the total power consumption of the LED luminaire is only slightly increased from 1.7W to 1.8W, reaching a constant power state.

Further, it is inferred from the above that when the light-emitting diode 2 is short-circuited and the current switch 141 and the sensing resistor 142 are momentarily subjected to a high voltage, the cross-voltages of the second resistor 144 and the sensing resistor 142 are also The increase is such that the operational amplifier 1403 outputs a low voltage because the voltage of the negative input terminal is greater than the reference voltage of the positive input terminal thereof, so as to cut off the current switch to form a short circuit protection, so that the LED lamp can be avoided. The abnormality of the external power source 3 causes damage.

The above description is only illustrative of preferred embodiments and not limiting. Any equivalent modifications or alterations to the spirit and scope of the invention are intended to be included in the scope of the appended claims.

1‧‧‧Control circuit

10‧‧‧Rectifier Module

100‧‧‧TRIAC

101‧‧‧Bridge rectifier

11‧‧‧Drive Module

110‧‧‧Steady capacitor

111‧‧‧ diode

12‧‧‧Linear dimming module

120‧‧‧voltage resistor

121‧‧‧Pressure capacitor

13‧‧‧Main current module

130‧‧‧ Third resistor

131‧‧‧fourth resistor

132‧‧‧ keep switch

133‧‧‧Retaining capacitance

14‧‧‧Control Module

140‧‧‧Control chip

1400‧‧‧ Voltage Regulator

1401‧‧‧Voltage generator

1402‧‧‧Selector

1403‧‧‧Operational Amplifier

1404‧‧‧Overvoltage protector

141‧‧‧current switch

142‧‧‧Sensor resistance

143‧‧‧First resistance

144‧‧‧second resistance

2‧‧‧Lighting diode

3‧‧‧External power supply

Figure 1 is a block diagram of a first embodiment of the preferred embodiment of the present invention.

Figure 2 is a block diagram of a second embodiment of the preferred embodiment of the present invention.

Figure 3 is a circuit diagram of a second embodiment of the preferred embodiment of the present invention.

Figure 4 is a waveform diagram showing the relationship between the fourth resistor and the TRIAC current in accordance with a preferred embodiment of the present invention.

Figure 5 is a waveform diagram showing the relationship between the detected voltage and the voltage across the sensing resistor in accordance with a preferred embodiment of the present invention.

Figure 6 is a waveform diagram of a preferred embodiment of the present invention.

1‧‧‧Control circuit

10‧‧‧Rectifier Module

100‧‧‧TRIAC

101‧‧‧Bridge rectifier

11‧‧‧Drive Module

110‧‧‧Steady capacitor

111‧‧‧ diode

12‧‧‧Linear dimming module

120‧‧‧voltage resistor

121‧‧‧Pressure capacitor

13‧‧‧Main current module

130‧‧‧ Third resistor

131‧‧‧fourth resistor

132‧‧‧ keep switch

133‧‧‧Retaining capacitance

14‧‧‧Control Module

140‧‧‧Control chip

1400‧‧‧ Voltage Regulator

1401‧‧‧Voltage generator

1402‧‧‧Selector

1403‧‧‧Operational Amplifier

1404‧‧‧Overvoltage protector

141‧‧‧current switch

142‧‧‧Sensor resistance

143‧‧‧First resistance

144‧‧‧second resistance

2‧‧‧Lighting diode

3‧‧‧External power supply

Claims (10)

A high-stability LED control circuit is adapted to drive and adjust the brightness of at least one of the light-emitting diodes, and has a rectifier module, a control module and a driving module, and the rectifier module is connected to an external power source by a telecommunication system. The driving module is connected to the rectifier module and the LED, the control module is electrically connected to the driving module and the LED, and the control module has a control chip, a current switch and a sense Measuring the resistance, the light-emitting diode is connected in series with the current switch and the sensing resistor, so that the sensing resistor senses a driving current flowing through one of the light-emitting diodes to form a feedback voltage to the sensing voltage of the control chip. The control module of the high-stability LED control circuit has a first resistor and a second resistor. The first resistor is coupled to the LED and the other end is coupled to the second resistor. And the control chip, and the other end of the second resistor is coupled to the current switch and the sensing resistor. When the voltage across the two ends of the LED is increased, the voltage across the second resistor is increased and compensated. The sensing resistor two Voltage across, in order to reduce the driving current of the constant power state. The high stability LED control circuit according to claim 1, wherein the rectifier module is coupled to the external power source through a bidirectional three-pole thyristor for receiving and adjusting a phase conduction angle of the external power source to change The driving current of the light emitting diode adjusts the light emitting brightness. The high stability LED control circuit of claim 2, wherein the control chip is provided with a voltage regulator, a voltage generator, a selector and an operational amplifier, and the voltage regulator is coupled to the The output of the rectifier module is coupled to the voltage generator. The positive input terminal of the operational amplifier is coupled to the selector, the negative input terminal is coupled to the second resistor, and the output terminal is coupled to the current switch. The high-stability LED control circuit as described in claim 3, further comprising a linear dimming module coupled to the output end of the rectifying module and the selector for detecting the rectified external power source And a detection voltage is output to the selector. The high stability LED control circuit according to claim 4, wherein when the detection voltage is greater than an upper limit value, the selector receives a reference voltage of the voltage generator output; when the detection voltage When the value is between the upper limit value and the lower limit value, the selector outputs a half pressure value of the detection voltage; when the detection voltage is less than the lower limit value, the selector outputs a shutdown signal to maintain the The basic brightness of the light-emitting diode enhances the dimming effect of the bidirectional triode fluid. The high stability LED control circuit as described in claim 5, further comprising a holding current module coupled to the output end of the rectifying module and the output end of the voltage regulator, and the voltage regulator After receiving the rectified external power source, a hold signal is generated, so that the hold current module is triggered to output a holding current to the bidirectional triode thyristor to ensure the normal operation of the bidirectional triode thyristor fluid. The high stability LED control circuit according to claim 6, wherein the holding current module has a third resistor, a fourth resistor, a holding switch and a holding capacitor, and the holding switch is N-type gold oxide. a half field effect transistor, and the third resistor is coupled to the rectifier module at one end and coupled to the drain of the holding switch at the other end. The source of the switch is coupled to the fourth resistor, and the gate is coupled to the regulator and the holding capacitor. The high stability LED control circuit of claim 7, wherein the third resistor and the fourth resistor receive the rectified external power source when the holding switch receives the hold signal and is turned on. A divided voltage is formed across the four resistors for charging and holding the holding capacitor to form the holding current. The high stability LED control circuit according to claim 8 , wherein the driving module is provided with a voltage stabilizing capacitor, which is connected to the light emitting diode to charge and discharge the driving current to enhance the circuit anti-noise. ability. The high stability LED control circuit according to claim 9, wherein the second resistor and the sensing resistor are short-circuited when the current switch and the sensing resistor are subjected to a high voltage instantaneously. The voltage across the terminals also increases, so that the voltage at the negative input of the operational amplifier is greater than the reference voltage at its positive input and the current switch is turned off to form a short circuit protection.