TWM518453U - LED dimming circuit of front-end power factor correction - Google Patents

Description

LED dimming circuit for pre-function correction

This creative system belongs to the technical field of electric light source driving circuit, in particular to a preamplifier LED dimming circuit, which stabilizes TRIAC by using a boost converter (Boost Converter) as a pre-stage circuit of the driving circuit. -Electrode AC Switch, two-way three-pole thyristor), and the controller in the pre-stage circuit realizes the functions of voltage regulation and maximum power limitation.

It is generally known that LED (Light Emitting Diode) lamps use control circuits that use phase-controlled switching elements such as SCR (Silicon Controlled Rectifier) or TRIAC to change the voltage phase of the input supply. The size of the driving voltage outputted by the control circuit is changed by switching the conduction angle of the voltage phase, thereby adjusting the amount of driving current flowing into the LED light source to realize the dimming effect. However, although such a dimming setting has the advantages of simple control and easy installation, the input power waveform will be in a distorted state, causing problems such as a decrease in power factor (PF) and an increase in voltage harmonics. Moreover, according to the current/voltage (I/V) characteristic curve of the LED, the LED and the nonlinear component, that is, the ratio of the voltage to the current is not proportional, therefore, the dimming method will change the driving voltage and the driving current. Inconsistent, making the dimming effect inaccurate and causing virtual power consumption. Furthermore, due to the component characteristics of the TRIAC, if the operating voltage flowing into the control circuit is too low and the current flowing through the TRIAC is insufficient for the required operating current, the TRIAC will repeatedly switch to the operating state, resulting in no driving current. Continuously flashes the LED, which reduces the quality of the illumination.

In order to solve the above problem, the LED lamp 1 having a dimmer 10 can be additionally provided with a compensation circuit 12 adjacent to a control circuit 11 as shown in FIG. 1. The compensation circuit 12 is mainly composed of a reference voltage generator 120. a voltage sampler 121, a comparator 122, and a control switch 123. The comparator 122 compares a reference voltage generated by the reference voltage generator 120 with a sample voltage formed by the voltage sampler 121. And outputting a control voltage to the control switch 123 when the sampling voltage is lower than the reference voltage, so that the compensation circuit 12 forms a loop with the control circuit 11 and provides a holding current to the control circuit 11 through the control switch 123. The operational stability of the dimmer 10 can be ensured to avoid problems such as stroboscopic flashing of the LED lamp 1. The compensation circuit 12, which is additionally added, can stabilize the working quality of the dimmer 10, but at the same time, it has a certain power loss and seriously affects the overall efficiency of the system.

In view of this, how to realize the PF improvement and the TRIAC current support function of the control circuit 11 by using the simplest controllable current source without additionally adding the compensation circuit 12, to stabilize the TRIAC dimming effect and improve the overall circuit The power conversion efficiency enhances the working quality and stability of the LED lamp 1, which is the subject of the research.

In view of the problems of the prior art, the purpose of the present invention is to provide an LED dimming circuit for pre-function correction, which realizes the voltage regulation function by controlling the output power of the IC controller in the pre-stage conversion circuit. PF correction effect.

According to the purpose of the present invention, the pre-stage power-correcting LED dimming circuit is provided for ensuring the stability of the dimming function and improving the power factor of the overall circuit, and has a dimming module, a rectifying module, a conversion module and a driving module, the rectifying module is electrically connected to the dimming module and the conversion module, and the driving module is electrically connected to the conversion module and at least one LED to utilize the rotation One of the output voltages of the module output drives at least one LED illumination, wherein the conversion module is provided with a current source, a detector, a controller and a power switch, and the current source is electrically connected to the rectifier mode The controller, the controller, the power switch and the driving module, the controller is electrically connected to the power switch and the detector; the current source is switched after receiving an input voltage of the rectifier module output Forming the stable output voltage, and the detector detects the magnitude of the output voltage and feeds back a sensed value to the controller, so that the controller turns off the power switch when the sensed value reaches a limit value to keep the The maximum power output by the conversion module to the drive module.

The current source is an inductor, and the power switch is a transistor, and the detector is provided with a sensing resistor electrically connected to the controller and coupled to the transistor to receive the output of the current source. The output voltage is sensed at both ends to form the sensed value. The detector is provided with a feedback resistor electrically connected to the controller and the driving module to receive the output voltage of the conversion module and form a feedback value at both ends, and then feedback to the controller.

Moreover, the controller is provided with an error amplifier, an on-period limiter, an arithmetic unit and an RS flip-flop. The positive input terminal of the error amplifier receives a reference value, and the negative input is coupled to the feedback resistor to receive the a feedback value, the output end of which is electrically connected to one input end of the on-period limiter, and the other input end of the on-period limiter is coupled to the sensing resistor to receive the sensing value, and the output end is coupled to the output end The RS flip-flop resets the pin, and the RS flip-flop is coupled to the output of the operator, and the positive input of the operator is provided with a zero voltage value and the negative input is electrically connected. The output of the current source.

In summary, the previous stage circuit of the present invention adopts a boost (Boost) conversion circuit to make the TRIAC work stably, and the working period of the power switch and the current source through the chip controller provided in the pre-stage circuit. Switch when the output current reaches the maximum tolerance The N-MOSFET is activated to achieve both power factor correction and maximum power limiting.

Prior art

1‧‧‧LED lamps

10‧‧‧Dimmer

11‧‧‧Control circuit

12‧‧‧Compensation circuit

120‧‧‧reference voltage generator

121‧‧‧Voltage Sampler

122‧‧‧ comparator

123‧‧‧Control switch

This creation

2‧‧‧LED dimming circuit

20‧‧‧ dimming module

21‧‧‧Rectifier Module

22‧‧‧Transition module

220‧‧‧current source

221‧‧‧Detector

2210‧‧‧Sensor resistance

2211‧‧‧Responsive resistance

222‧‧‧ Controller

2220‧‧‧Error amplifier

2221‧‧‧ On-period limiter

2222‧‧‧Operator

2223‧‧‧RS forward and reverse

223‧‧‧Power switch

224‧‧‧Slow boot unit

23‧‧‧Drive Module

3‧‧‧LED

Figure 1 is a schematic diagram of a dimming circuit of a conventional LED lamp.

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

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

Figure 4 is a waveform diagram of a preferred embodiment of the present invention.

Figure 5 is a circuit diagram of an embodiment of a preferred embodiment of the present invention.

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

Figure 7 is a circuit diagram of a third embodiment of the preferred embodiment of the present invention.

In order for your review board to have a clear understanding of the content of this creation, please use the following instructions to match the drawings.

Please refer to FIG. 2 to FIG. 4 for the block diagram, circuit diagram and waveform diagram of the preferred embodiment. As shown in the figure, the pre-stage power-correcting LED dimming circuit 2 adopts a Boost voltage regulator circuit structure and is suitable for being followed by a self-excited conversion circuit, a Flyback conversion circuit or a SEPIC as shown in FIGS. 5, 6, and 7. The conversion circuit and the like are provided with a dimming module 20, a rectifying module 21, a converting module 22 and a driving module 23. The rectifying module 21 is electrically connected to an external power source through the dimming module 20 ( The power of the external power source is intercepted and converted to form an input voltage (V _b ), and the input voltage is affected by the dimming effect of the dimming module 20 to have different phase angles. The conversion module 22 is electrically connected to the rectifier module 21 to receive the input voltage and then converted to form an output voltage (V _o ), and to ensure the stability of the operation of the dimming module 20 and improve the power factor of the overall circuit. The conversion module 22 is provided with a current source 220, a detector 221, a controller 222 and a power switch 223 for performing power factor control and limiting the maximum output power through the controller 222. Moreover, the driving module 23 is electrically connected to the conversion module 22 and the at least one LED 3 to drive the LED 3 to emit light by using the output voltage.

The current source 220 can be an inductor, the power switch 223 can be a transistor, and the detector 221 can be provided with a sensing resistor 2210 and a feedback resistor 2211. The inductor is electrically connected to the rectifier module 21, the controller 222, the feedback resistor 2211 and the transistor. The controller 222 is coupled to the gate of the transistor, the sensing resistor 2210 and the feedback resistor 2211. The feedback resistor 2211 is electrically connected to the driving module 23 . The inductor receives one input voltage of the rectifier module 21 and converts to form a stable output voltage, and the sensing resistor 2210 detects the output voltage and senses the sensing value at both ends, and the feedback is performed. The resistor 2211 detects the magnitude of the output voltage and detects the formation of the feedback value at both ends.

Moreover, the controller 222 can be a chip having 8 pins of VIN, VDD, COMP, GND, ZCD, OUT, CS, and FB, and is provided with an error amplifier 2220, a conduction period limiter 2221, and an operator 2222. And an RS flip-flop 2223, the positive input terminal of the error amplifier 2220 receives a reference value (V _ref ), and the negative input is coupled to the feedback resistor 2211 through the FB pin to receive the feedback value, and the output end is electrically connected. One of the input terminals of the on-period limiter 2221 is connected. The other input end of the on-time limiter 2221 receives the sensed value through the CS pin coupled to the sense resistor 2210, and the output end is coupled to the reset pin of the RS flip-flop 2223, and the RS is positive. The set pin of the counter 2223 is coupled to the output end of the operator 2222, and the output pin is electrically connected to the gate of the transistor through the OUT pin. The positive input terminal of the computing device 2222 is provided with a zero voltage value (V _zcd ) and the negative input terminal is electrically connected to the output terminal of the current source 220 through the ZCD pin. The error amplifier 2220 compares the feedback value and the reference value to adjust the operation state of the power switch 223 by controlling the output time of the reset signal of the RS flip-flop 2223 through the on-period limiter 2221. At the same time, the operator 2222 uses the zero voltage value to determine whether the inductor has completely released energy, as the conduction basis of the next cycle of the power switch 223, so that the voltage stabilization effect and the power factor control are achieved. characteristic. Moreover, the conduction period limiter 2221 drives the RS flip-flop 2223 to turn off the transistor when the sensed value reaches a limit value, so as to limit the maximum value of the output power (P _o ) of the conversion module 22, such as As shown in FIG. 4, when the input voltage is a constant value, the LED dimming circuit 2 has a linear relationship with the duty cycle of the input voltage due to the operating mechanism characteristic of the maximum power limitation, in other words, After the AC sine wave of the external power source is controlled by the dimming module 20 to form an input voltage having different phase angles, the magnitude of the output power also changes with the magnitude of the phase angle.

In this embodiment, the controller 222 further has a Soft-Start unit 224 connected between the VIN pin and the COMP pin to determine the degree of change of the input voltage and instantaneously change in voltage. When the power switch is turned on slowly, the magnetic components in the driving module 23 can be prevented from being saturated to avoid low frequency noise.

However, the above descriptions are only for the preferred embodiment of the present invention and are not intended to limit the scope of the present invention; therefore, the equivalent changes and modifications made without departing from the spirit and scope of the present invention should be Within the scope of this creation's patent.

2‧‧‧LED dimming circuit

20‧‧‧ dimming module

21‧‧‧Rectifier Module

22‧‧‧Transition module

220‧‧‧current source

221‧‧‧Detector

2210‧‧‧Sensor resistance

2211‧‧‧Responsive resistance

222‧‧‧ Controller

2220‧‧‧Error amplifier

2221‧‧‧ On-period limiter

2222‧‧‧Operator

2223‧‧‧RS forward and reverse

223‧‧‧Power switch

224‧‧‧Slow boot unit

23‧‧‧Drive Module

3‧‧‧LED

Claims (5)

A pre-stage power-correcting LED dimming circuit for ensuring the stability of the dimming function while improving the power factor of the overall circuit, and providing a dimming module, a rectifying module, a converting module and a driving module The rectifier module is electrically connected to the dimming module and the conversion module, and the driving module is electrically connected to the conversion module and the at least one LED to output at least one LED by using the output voltage of the conversion module. The illuminating device is characterized in that: the conversion module is provided with a current source, a detector, a controller and a power switch, the current source is electrically connected to the rectifier module, the detector, the controller, the a power switch and the driving module, the controller is electrically connected to the power switch and the detector; the current source receives an input voltage of the rectifier module and is converted to form a stable output voltage, and the detector Detecting the output voltage and feeding back a sensing value to the controller, so that the controller turns off the power switch when the sensing value reaches a limit value, so as to constant the maximum power output by the conversion module to the driving module. . The LED dimming circuit of the prior art power factor correction according to claim 1, wherein the current source is an inductor, and the power switch is a transistor. The LED dimming circuit of the prior art power factor correction according to the second aspect of the patent application, wherein the detector is provided with a sensing resistor electrically connected to the controller and coupled to the transistor to receive the current The output voltage of the source output is sensed at both ends to form the sensed value. The LED dimming circuit of the prior art power factor correction according to claim 3, wherein the detector is provided with a feedback resistor electrically connected to the controller and the driving module to receive the conversion mode The output voltage of the group output forms a feedback value at both ends, and is fed back to the controller. The LED dimming circuit of the prior art power correction according to claim 4, wherein the controller is provided with an error amplifier, a conduction period limiter, an arithmetic unit and an RS flip-flop, the error amplifier The positive input terminal receives a reference value, the negative input is coupled to the feedback resistor to receive the feedback value, and the output end is electrically connected to one input end of the conduction period limiter, and the other input end of the conduction period limiter The sensing resistor is coupled to receive the sensing value, the output end of the RS is coupled to the reset pin of the RS flip-flop, and the set pin of the RS flip-flop is coupled to the An output end of the computing unit, the positive input end of the computing device is provided with a zero voltage value and the negative input terminal is electrically connected to the output end of the current source.