CN204046881U - A kind of LED dimming power supply - Google Patents

Abstract

An LED dimming power supply includes a PWM signal generating module, a switch control module electrically connected to the PWM signal generating module, and a DC/DC converter electrically connected to the switch control module. The PWM signal generation module includes a comparison operator. The switch control module is used for turning off the DC/DC converter before the voltage amplitude of the output terminal of the comparison operator reaches a steady-state constant voltage point. Since the LED dimming power supply includes the PWM signal generation module and the switch control module, before the voltage amplitude at the output terminal of the comparison operator of the PWM signal generation module reaches the steady-state constant voltage point, the The DC/DC converter is always in the off state, so that the load will not have current flow before the voltage amplitude of the output terminal of the comparison operator does not reach the steady-state constant voltage point, thereby avoiding the LED lamp load There is flickering phenomenon, which improves the experience of using LED lamps.

Description

A kind of LED dimming power supply

technical field

The utility model relates to lighting system equipment, in particular to an LED dimming power supply.

Background technique

In general daily life, various lighting devices can be seen everywhere, for example, fluorescent lamps, street lamps, table lamps, art lamps and the like. Among the above-mentioned lighting devices, traditionally most of them use tungsten filament bulbs as light sources. In recent years, light-emitting diodes (LEDs) have been used as a source of light due to advances in technology. What's more, in addition to lighting equipment, for general traffic signs, billboards, car lights, etc., light-emitting diodes are also used as light-emitting light sources instead. As mentioned above, the advantage of using light-emitting diodes as a light source is that it saves power and has higher brightness, so it has gradually become popular in use.

With the popularization of LED lamps, LED lamps are used in more and more occasions, such as shopping malls, hotels, and homes. Especially for the use of hotel lamps, guests put forward more stringent requirements for the use of their lights, such as uniform illumination, no glare, and no flicker. As for the flickering problem of LED lamps, most of them are caused by the characteristics of the power supply of LED lamps. For example, the inconsistency between the charge and discharge time of capacitors and the climb time of other electronic components, such as operational amplifiers, is inevitable. The flickering problem of the LED lamp will reduce the user's experience of using the lamp.

Utility model content

In view of this, it is necessary to provide an LED dimming power supply that prevents LED lamps from flickering, so as to overcome the above-mentioned shortcomings.

An LED dimming power supply, comprising a PWM signal generating module, a switch control module electrically connected to the PWM signal generating module, a DC/DC converter electrically connected to the switch control module, and a The PWM signal generation module, the switch control module and the internal power supply module powered by the DC/DC converter. The PWM signal generation module includes a comparison operator. The switch control module is used for turning off the DC/DC converter before the voltage amplitude of the output terminal of the comparison operator reaches a steady-state constant voltage point.

Compared with the prior art, since the LED dimming power supply includes the PWM signal generation module and the switch control module, the voltage amplitude at the output terminal of the comparison operator of the PWM signal generation module does not reach a steady state Before the constant voltage point, the DC/DC converter is always in the off state, so that no current will flow through the load until the voltage amplitude at the output terminal of the comparison operator reaches the steady-state constant voltage point , thereby avoiding the flickering phenomenon of the LED lamp load, and improving the use experience of the LED lamp.

Description of drawings

Describe embodiments of the present utility model below in conjunction with accompanying drawing, wherein.

Fig. 1 is a schematic circuit diagram of an LED dimming power supply provided by the first embodiment of the present invention.

FIG. 2 is one of the circuit diagrams of the LED dimming power supply in FIG. 1 .

FIG. 3 is the second circuit diagram of the LED dimming power supply in FIG. 1 .

Fig. 4 is a circuit diagram of an LED dimming power supply provided by the second embodiment of the present invention.

Detailed ways

The specific embodiments of the present utility model will be described in further detail below based on the accompanying drawings. It should be understood that the specific embodiments described here are only examples, and are not intended to limit the protection scope of the present utility model.

Please refer to FIG. 1 , which is a schematic circuit diagram of an LED dimming power supply 100 according to a first embodiment of the present invention. The LED dimming power supply 100 includes a PWM signal generating module 10, a signal isolation module 11 electrically connected to the PWM signal generating module 10, a switch control module 12 electrically connected to the signal isolation module 11, and a The switch control module 12 is electrically connected to a DC/DC converter 13, and an internal power supply module for supplying power to the PWM signal generation module 10, the signal isolation module 11, the switch control module 12 and the DC/DC converter 13 14. Of course, it is conceivable that the LED dimming power supply 100 is used to provide a constant voltage or constant current power supply for an LED lamp load. The LED lamp load includes at least one LED lamp. At the same time, the LED dimming power supply 100 also includes some other functional modules, such as EMI filter circuit, rectifier circuit, transformer, etc., which are the functional modules of general power supplies, and will not be described in detail here.

As shown in Figure 2, the PWM signal generating module 10 includes a comparison operator N1A, a triangular wave generating circuit 101 electrically connected to the non-inverting input of the comparison operator N1A, and an inverting input to the comparison operator N1A The constant voltage conversion circuit 102 electrically connected to the terminals. The output of the triangular wave generating circuit 101 is a triangular wave, and the output of the constant voltage conversion circuit 102 is a constant voltage of 0 to 10V. After the comparison operation of the comparison operator N1A, the comparison operator The output of N1A is a square wave with a certain amplitude. By adjusting the output voltage value of the constant voltage conversion circuit 102 , the duty cycle of the output square wave of the comparison operator N1A can be adjusted, that is, a PWM signal with a certain duty cycle. Therefore, the output of the PWM signal generating module 10 is a PWM signal with a certain duty ratio, and when the PWM signal with a certain duty ratio is transmitted to the DC/DC converter 13, the output of the DC/DC converter 13 The voltage or current is adjusted by the PWM signal, and then the brightness of the LED lamp electrically connected to the DC/DC converter 13 is adjusted to achieve the purpose of dimming. The PWM signal generating module 10 also includes a capacitor C3. The capacitor C3 is electrically connected between the inverting input terminal of the comparison operator N1A and ground. The reason for setting the capacitor C3 is because the rising speed of the triangular wave voltage at the non-inverting input terminal is lower than the rising speed of the constant voltage at the inverting input terminal, so in order to make the voltage rising speed at the inverting input terminal slower, this capacitor is set between it and the ground. Capacitor C3, to ensure that the output of the comparison operator N1A has a long enough high level time.

The function of the signal isolation module 11 is to isolate the PWM signal generation module 10 and the DC/DC converter 13 , so that the PWM signal generation module 10 and the DC/DC converter 13 are basically insulated. This is because the quality of the PWM signal generating modules 10 on the market is uneven, and the insulation is difficult to guarantee, and in order to protect the quality of the entire LED dimming power supply 100, it is necessary to make the DC/DC converter 13 and the PWM signal generating module 10 reach Basic insulation. In this embodiment, the signal isolation module 11 includes an optocoupler N2 and a resistor R2. The optical coupler N2 includes a diode and a phototransistor. The cathode of the diode is electrically connected to the output end of the comparator N1A, and the anode is electrically connected to the resistor R2. The collector of the phototransistor is electrically connected to the switch control module 12, and the emitter is grounded. The resistor R2 is electrically connected between the anode of the diode and the power input terminal Vcc of the comparator N1A. The isolation principle of the optocoupler N2 is obvious, because there is no direct electrical connection, so the PWM signal generating module 10 and the DC/DC converter 13 can be insulated from each other to meet safety requirements. The function of the signal isolation module 11 in preventing the LED light load from flickering is to invert the high and low levels output by the signal isolation module 11 . Because of the existence of the phototransistor, it inverts the high and low levels of the output, that is, if there is no R2, when the output of the comparison operator N1A is at a high level, the phototransistor is turned on, and the output is at a low level, while the comparison operator When the output of N1A is low level, the phototransistor is cut off, and the output is high level. With the resistor R2, when the output of the comparison operator N1A is at a high level, under the action of its input terminal Vcc and the resistor R2, the voltage applied to the diode is at a low level, the diode is cut off, and the photosensitive Transistor cut off, the output is high level. Similarly, when the output of the comparison operator N1A is at high level, the output of the signal isolation module 11 is at low level. So as to achieve the purpose of high and low level inversion. It is conceivable that, as shown in FIG. 3 , the resistor R2 can also be electrically connected between the cathode of the diode and the ground, and its function is the same, which is to make the high and low voltage output by the signal isolation module 11 Flat to invert. However, at this time, the anode of the diode should be electrically connected to the output terminal of the comparator N1A of the PWM signal generating module 10 .

The internal power module 14 includes a transformer TR1, two capacitors C1, C2 connected in parallel to the primary and secondary of the transformer TR1, and two diodes D1, C2 respectively connected in series to the primary and secondary of the transformer TR1, D2. The function of the capacitors C1 and C2 is to filter, and the purpose is to reduce the fluctuation of the voltage input to the transformer TR1 and output from the transformer TR1, so as to achieve the purpose of voltage stabilization. The function of the diodes D1 and D2 is unidirectional conduction to cooperate with the capacitors C1 and C2 for filtering. Because if the voltages across the capacitors C1 and C2 are not unidirectional, they will lose their function.

The switch control module 12 includes two resistors R3 and R4 connected in series, and a MOS transistor Q2. The resistors R3 and R4 are electrically connected in series to the output end of the internal power module 14 . The MOS transistor Q2 can be an N-channel MOS transistor, or a P-channel MOS transistor. In this embodiment, the MOS transistor Q2 is an N-channel MOS transistor, its source is grounded, its gate is electrically connected to the collector of the phototransistor and is electrically connected between the resistors R3 and R4, and its drain It is electrically connected with the EN pin of the DC/DC converter 13 . Since the two resistors R3 and R4 are connected in series at both ends of the high and low levels of the internal power supply module 14, different voltage values at both ends of the resistor R3 and the resistor R4 can be collected by selecting the resistance values of the resistor R3 and the resistor R4 , and at the same time as the output voltage of the internal power module 10 rises, the voltage values across the resistors R3 and R4 also change. At this time, the ratio of the resistance values of the resistor R3 and the resistor R4 becomes the switch threshold of the switch control module 12 , which determines the switch of the MOS transistor Q2 . When the LED dimming power supply 100 is powered on, the internal power supply module 14 works immediately, so that the two ends of the two resistors R3 and R4 of the switch control module 12 are loaded with voltage, and the drive of the MOS transistor Q2 is driven by the resistors R3 and R4. R4 controls, so the MOS transistor Q2 is turned on, and the level of the EN pin of the DC/DC converter 13 is pulled down, so the DC/DC converter 13 has no output and does not work. At this time, because the capacitors C1 and C2 of the internal power supply module 14 need to be charged, the triangular wave waveform of the non-inverting input terminal of the comparison operator N1A is slowly climbing, and the voltage at the inverting input terminal is also slowly climbing, so the output terminal of the comparison operator N1A is also slowly rising. Under the action of the input Vcc terminal and the resistor R2, the high level is maintained, the internal diode of the signal isolation module 11 is cut off, and no current is fed back to the secondary phototransistor. As time goes by, the voltages on the capacitors C1 and C2 of the internal power module 14 gradually increase, and the triangular wave waveform on the non-inverting input terminal of the comparator N1A tends to be stable, that is, the voltage tends to be stable. The voltage on the inverting input terminal will also tend to be stable. At this time, the output terminal of the comparator N1A is a stable PWM waveform with increasing amplitude, that is, the voltage amplitude has reached the steady-state constant voltage point. Of course, it is conceivable that when the output voltage of the constant voltage conversion circuit 102 of the PWM signal generating module changes between 0 and 10 volts, the amplitude of the output terminal of the comparison operator N1A also changes, but at a fixed moment, its amplitude is constant, rather than a rising slope wave. That is, the PWM signal is changing, thereby controlling the output voltage of the DC/DC converter 13 , and further controlling the brightness change of the LED lamp load. When the voltage amplitude of the output terminal of the comparison operator N1A reaches the steady-state constant voltage point, the output voltage value switches between high and low levels along with the PWM signal, only when the output voltage of the constant voltage conversion circuit 102 is between 0 and 10 Its duty cycle changes as it changes between volts. When the voltage amplitude of the output terminal of the comparison operator N1A reaches the steady-state constant voltage point and is at a low level, the internal diode of the signal isolation module 11 is turned on, and a current is fed back to the secondary phototransistor, that is, the phototransistor is turned on, The MOS transistor Q2 is turned off, so that the EN pin of the DC/DC converter 13 is at a high level, the output terminal of the DC/DC converter 13 has a voltage output, and then both ends of the load are loaded with voltage, and the LED lamp load starts to work. And when the voltage amplitude of the output terminal of the comparison operator N1A reaches the steady-state constant voltage point and is at a high level, the internal diode of the signal isolation module 11 is cut off, and no current is fed back to the secondary phototransistor, that is, the phototransistor is cut off, and the MOS The transistor Q2 is turned on, so that the EN pin of the DC/DC converter 13 is at low level, and the output terminal of the DC/DC converter 13 has no voltage output.

The DC/DC converter 13 is a switching power supply chip, which uses the energy storage characteristics of capacitors and inductors to perform high-frequency switching actions through controllable switches (MOSFET, etc.), and stores the input electric energy in capacitors (inductors, etc.) ), when the switch is turned off, the electric energy is released to the load to provide energy. Its output power or voltage capability is related to the duty cycle (the ratio of the switch on time to the entire switch cycle). When the switch control module 12 is turned on, that is, the source and drain of the MOS transistor Q2 are turned on, thereby reducing to a low level, and then pulling down the voltage of the EN pin of the DC/DC converter 13, the DC/DC The output end of the DC converter 13 has no output, and the load does not work. And when the switch control module 12 is cut off, the drain of the MOS transistor Q2 and the output terminal of the DC/DC converter 13 are both at high level, and then the output terminal of the DC/DC converter 13 has a voltage output, and then the voltage is output between the two load terminals. There is a voltage load on the terminal, and the load 14 starts to work.

Please refer to FIG. 4 , which is a circuit diagram of an LED dimming power supply 200 according to a second embodiment of the technology of the present invention. The LED dimming power supply 200 includes a PWM signal generating module 20, a signal isolation module 21 electrically connected to the PWM signal generating module 20, a switch control module 22 electrically connected to the signal isolation module 21, and a A DC/DC converter 23 connected to the switch control module 22, an internal power supply module 24 for supplying power to the PWM signal generating module 20, the signal isolation module 21, the switch control module 22 and the DC/DC converter 23 , and an undervoltage protection circuit 25 electrically connected between the output terminal of the internal power supply module 24 and the EN pin of the DC/DC converter 23 . Meanwhile, in the first embodiment, the LED dimming power supply 200 is used to provide a constant voltage or constant current power supply for an LED lamp load. The LED lamp load includes at least one LED lamp. At the same time, the LED dimming power supply 200 also includes some other functional modules, such as EMI filter circuit, rectifier circuit, transformer, etc., which are the functional modules of general power supplies, and will not be described in detail here.

When the rated voltage of the LED lamp load is very low, for example, there is only one LED lamp, its rated voltage is only 3.6 volts, and there is a minimum operating voltage requirement inside the DC/DC converter 23 , on the entire LED dimming power supply 200 After power on, when the output voltage rises to 6 volts, because the load is small, and the switch control module 22 is not working yet, the EN pin of the DC/DC converter 23 has not been pulled to a low level and there is an output , the LED light with only one light will be on for a while, and then the switch control module 22 will start to work, and the LED light will go out, resulting in a flickering phenomenon. Therefore, the purpose of adding the undervoltage protection circuit 25 is to turn off the DC/DC converter 23 when the output voltage of the internal power module 24 is greater than the threshold voltage of the undervoltage protection circuit 25, so that when the switch is controlled When the module 22 is not working, the DC/DC converter 23 is turned off, that is, the EN pin of the DC/DC converter 23 is pulled to a low level.

Compared with the prior art, since the LED dimming power supply 100 includes the PWM signal generation module 10, the signal isolation module 11, and the switch control module 12, the comparison operator of the PWM signal generation module 10 Before the voltage amplitude of the output terminal reaches the steady-state constant voltage point, the DC/DC converter is always in the off state, so that the voltage amplitude of the load at the output terminal of the comparison operator does not reach the steady-state constant voltage point. There will be no current flowing before the pressure point, which can avoid the flickering phenomenon of the LED lamp load, and provide the user experience of the LED lamp.

As shown in FIG. 4 , the undervoltage protection circuit 25 includes two resistors R5 and R6 connected in series, a Zener diode D3 electrically connected between the resistors R5 and R6, and a Zener diode D3 electrically connected between the resistors R5 and R6. A transistor Q3 at the positive pole of D3, and a transistor Q4 electrically connected to the collector of the transistor Q3. The cathode of the Zener diode D3 is connected to the resistors R5 and R6. The base of the triode Q3 is connected to the anode of the Zener diode D3, and the emitter is grounded. The collector of the transistor Q3 is connected in series with a resistor R8 to the output terminal of the internal power module 24 to supply power to the transistors Q3 and Q4. The base of the transistor Q4 is connected in series with a resistor R9 to the collector of the transistor Q3, and the emitter is grounded. The collector of the transistor Q4 is electrically connected to the EN pin of the DC/DC converter 23 .

The working principle of the undervoltage protection circuit 25 is as follows. When the output voltage of the internal power supply module 24 is greater than the breakdown voltage of the Zener diode D3 but lower than the operating voltage of the switch control module 22, the Zener diode D3 is broken down and turned on, and the transistor Q3 is turned off at this time. . Driven by the voltage of the EN pin of the DC/DC converter 23, the triode Q4 conducts between the collector and the emitter of the triode Q4, thereby pulling the voltage of the EN pin of the DC/DC converter 23 to low level, and then turn off the DC/DC converter 23, preventing it from supplying power to the load. And as the output voltage of the internal power supply module 24 further increases, the switch control module 22 starts to work. After this, the working principle of the LED dimming power supply 200 is the same as that of the LED investigation light power supply 200 of the first embodiment, and No more details.

The above descriptions are only preferred embodiments of the present utility model, and are not intended to limit the present utility model. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present utility model shall be included in this utility model. within the scope of protection of utility models.

Claims (10)

1. a LED dimming power source, it is characterized in that: described LED dimming power source comprises a pwm signal generation module, a switch control module be electrically connected with this pwm signal generation module, and a DC/DC transducer be electrically connected with this switch control module, described pwm signal generation module comprises a comparison operation device, and described switch control module is used for turning off described DC/DC transducer before the voltage magnitude of the output of described comparison operation device reaches the constant pressure point of stable state.

2. LED dimming power source as claimed in claim 1, it is characterized in that: described pwm signal generation module also comprises a triangle wave generating circuit be electrically connected with the in-phase input end of comparison operation device, and a constant voltage change-over circuit be electrically connected with the inverting input of arithmetic unit, the output voltage of described constant voltage change-over circuit is constant voltage.

3. LED dimming power source as claimed in claim 1, is characterized in that: described pwm signal generation module also comprises an electric capacity, between the inverting input that this electric capacity is electrically connected at described comparison operation device and ground.

4. LED dimming power source as claimed in claim 1; it is characterized in that: described LED dimming power source also comprises a under-voltage protecting circuit; described under-voltage protecting circuit is electrically connected between described internal electric source module and switch control module, and described under-voltage protecting circuit is used for turning off described switch control module when the output voltage of internal electric source module is less than its threshold voltage.

5. LED dimming power source as claimed in claim 4, it is characterized in that: described under-voltage protecting circuit comprises a voltage stabilizing didoe, the puncture voltage of this voltage stabilizing didoe is described threshold voltage.

6. LED dimming power source as claimed in claim 1, it is characterized in that: described LED dimming power source also comprises a signal isolation module, this signal isolation module to be electrically connected between described pwm signal generation module and switch control module and for isolating described pwm signal generation module and DC/DC transducer to make to insulate between this pwm signal generation module and DC/DC transducer.

7. LED dimming power source as claimed in claim 6, it is characterized in that: described signal isolation module comprises an optical coupler, and a resistance R2, described optical coupler comprises a diode and a phototriode, the positive pole of described diode is connected with the output electric property of comparison operation device, minus earth, the collector electrode of described triode and switch control module are electrically connected, grounded emitter, described resistance R2 is electrically connected between the positive pole of described diode and the power input of comparison operation device.

8. LED dimming power source as claimed in claim 7, it is characterized in that: described switch control module comprises resistance R3, R4 of two series connection, with a metal-oxide-semiconductor, described resistance R3, R4 are electrically connected at the output of internal electric source module, described metal-oxide-semiconductor is N-channel MOS pipe, its source ground, the collector electrode of grid and phototriode is electrical connected and is electrically connected at described between resistance R3, R4, and drain electrode is electrically connected with the EN pin of described DC/DC transducer.

9. LED dimming power source as claimed in claim 1, it is characterized in that: described signal isolation module comprises an optical coupler, and a resistance R2, described optical coupler comprises a diode and a phototriode, the positive pole of described diode is connected with the output electric property of comparison operation device, minus earth, and the collector electrode of described triode and switch control module are electrically connected, grounded emitter, between the negative pole that described resistance R2 is electrically connected at described diode and ground connection.

10. LED dimming power source as claimed in claim 1, is characterized in that: described LED dimming power source also comprises an internal electric source module for powering for described pwm signal generation module, switch control module and DC/DC transducer.