CN206533573U - A kind of power supply adjusting control circuit and power supply - Google Patents

Abstract

The utility model relates to a power supply dimming control circuit and a power supply, comprising a first switch, a second switch, a detection control circuit, a feedback circuit and a PWM control circuit, the first switch is connected with an external dimming circuit that provides dimming voltage, and the second The second switch is connected between the output terminal of the power supply and the detection control circuit, the feedback circuit is connected to the detection control circuit, receives the detection control signal output by the detection control circuit and outputs the feedback signal to the PWM control circuit, and the PWM control circuit turns off the power supply according to the feedback signal . When this solution is applied to the LED field, it can quickly turn off the LED light without flickering, effectively reduce power consumption, and benefit the long-term reliable operation of the power supply. There is no flickering in the middle of the fast turn-off and turn-on process, and it can also be adjusted in the LED light. From the minimum brightness to the maximum brightness during the light process, the purpose of slowly starting the LED lamp is realized, and the life of the LED lamp is effectively improved.

Description

A power dimming control circuit and power supply

technical field

The utility model relates to the technical field of power supply drive, in particular to a power supply dimming control circuit and a power supply.

Background technique

In the field of LED street lamp driving power supply, many occasions will need to turn off the LED lamp after dimming to a certain brightness. The existing technology is to use the driver IC controlled by light control to make the DC-DC converter work intermittently. When the voltage on the LED lamp does not reach the turn-on voltage, the LED lamp can be turned off; or on the output terminal of the power supply An electronic switch is connected in series, and the electronic switch is turned off when the dimming circuit needs to be turned off. However, there are following defects in existing conventional designs:

1. The PWM IC is in the intermittent working state through the optocoupler control, which has the following disadvantages in the application:

While controlling the PWM IC, the VCC voltage is also changing. It may be that the IC cannot work when it reaches the shutdown voltage of the IC. In addition, the output voltage will have a process of rushing up during intermittent operation, causing the LED light to flash quickly.

2. The method of connecting electronic switches in series at the output end has the following disadvantages in practical application:

During the shutdown process, the DC-DC converter is always working, which increases the standby loss and cannot meet the consumption reduction standard; adding an electronic switch increases the cost of the electronic switch, and the electronic switch will increase the loss during normal operation, making the The efficiency of the whole machine is reduced.

Utility model content

The technical problem to be solved by the utility model is to provide a power supply dimming and shutdown control circuit and a power supply for the above-mentioned defects of the prior art.

The technical solution adopted by the utility model to solve the technical problem is: to construct a kind of power supply dimming shut-off control circuit, comprising:

A first switch connected to an external dimming circuit that provides a dimming voltage, a second switch connected to the first switch and the output end of the power supply, a detection control circuit connected to the second switch, and the detection control circuit A feedback circuit connected to the circuit, and a PWM control circuit connected to the feedback circuit;

The first switch is turned on or off according to the dimming voltage;

When the second switch is turned on, the output voltage of the output terminal of the power supply supplies power to the detection control circuit through the second switch, and at the same time, the detection control circuit outputs a detection control signal to the feedback according to the output voltage. circuit, the feedback circuit outputs a feedback signal to the PWM control circuit to turn off the power supply according to the detection control signal; the second switch is turned on when the first switch is turned off.

In the power supply dimming and shutdown control circuit described in the present invention, preferably, a sampling circuit is also included, and the sampling circuit is connected to the external dimming circuit, and is used to collect the dimming signal provided by the external dimming circuit. voltage and output the collection voltage to the first switch, and the first switch is turned on or off according to the collection voltage.

In the power supply dimming and shutdown control circuit described in the utility model, preferably, a voltage dividing circuit is further included, and the voltage dividing circuit is connected between the output terminal of the power supply and the detection control circuit for receiving The output voltage and a divided voltage signal are output to the second switch to turn on the second switch.

In the power dimming and shutdown control circuit of the present invention, preferably, the first switch is a transistor Q3, and the second switch is a transistor Q1.

In the power supply dimming and shutdown control circuit described in the present invention, preferably, the sampling circuit includes a resistor R4 and a resistor R21, and the resistor R4 and the resistor R21 are connected in series between the external dimming circuit and the reference ground, and the node between the resistor R4 and the resistor R21 is also connected to the base of the transistor Q3;

The resistor R2 and the resistor R21 collect the dimming voltage output by the external dimming circuit and output the collected voltage to the base of the transistor Q3, and the collected voltage is lower than the turn-on voltage of the base of the transistor Q3 , the transistor Q3 is turned off.

In the power supply dimming and shutdown control circuit described in the present invention, preferably, the voltage divider circuit includes a resistor R56 and a resistor R3, the first end of the resistor R56 is connected to the output end of the power supply, and the The second end of the resistor R56 is connected to the first end of the resistor R3, the second end of the resistor R3 is connected to the base of the transistor Q1, and the node between the resistor R3 and the transistor Q1 is also connected to to the collector of the transistor Q3; the node between the resistor R56 and the resistor R3 is also connected to the collector of the transistor Q1;

If the transistor Q3 is turned off, the resistor R56 and the resistor R3 divide the output voltage and output a divided signal to the base of the transistor Q1 to turn on the transistor Q1.

In the power supply dimming shutdown control circuit described in the present invention, preferably, it further includes a resistor R2, a diode D3, and a capacitor CE1, the anode of the diode D3 is connected to the emitter of the triode Q1, and the diode The cathode of D3 is connected to the positive pole of the capacitor CE1, the negative pole of the capacitor CE1 is connected to the reference ground, and the node where the cathode of the diode D3 is connected to the positive pole of the capacitor CE1 is also connected to the detection control circuit; the resistor A first end of R2 is connected to the anode of the diode D3, and a second end of the resistor R2 is connected to the detection control circuit.

In the power dimming and shutdown control circuit described in the present invention, preferably, the detection control circuit includes a control chip and a resistor R6;

The control chip includes detection pins, control pins, and power supply pins;

The second end of the resistor R2 is connected to the detection pin of the control chip, the first end of the resistor R6 is connected to the control pin of the control chip, and the second end of the resistor R6 is connected to the Feedback circuit; the power supply pin is connected to the node between the cathode of the diode D3 and the anode of the capacitor CE1;

The output voltage generates an instantaneous voltage to the detection pin of the control chip through the resistor R2, and the detection pin outputs a detection control signal to the resistor R6 according to the instantaneous voltage, and the control signal is transmitted to the resistor R6 through the resistor R6. sending to the feedback circuit to turn on the feedback circuit;

The output voltage charges the capacitor CE1 through the diode D3 when the transistor Q1 is turned on, and discharges the power supply pin of the control chip through the capacitor CE1 when the power supply is turned off. The control chip is powered.

In the power supply dimming and shutdown control circuit described in the present invention, preferably, the feedback circuit includes a common anode diode D1 and a photocoupler U1, and the common anode diode D1 includes a first terminal, a second terminal and a second terminal. Three terminals, the first end of the common anode diode D1 is an anode, the second end of the common anode diode D1 is a first cathode, and the third end of the common anode diode D1 is a second cathode; the photocoupler The device U1 includes a primary light-emitting diode U1-A and a secondary receiving source U1-B;

The first cathode of the common anode diode D1 is connected to the second end of the resistor R6, the anode of the common anode diode D1 is connected to the primary light-emitting diode U1-A of the photocoupler U1, and the secondary receiving The output end of the source U1-B is connected to the PWM control circuit;

The first cathode of the common anode diode D1 receives the detection control signal transmitted by the resistor R6 and turns on the primary light-emitting diode U1-A of the photocoupler U1 to generate a light source. The photocoupler U1-B The secondary receiving source outputs a feedback signal to the PWM control circuit according to the turning on of the light source, and the PWM control circuit turns off the power supply according to the feedback signal.

The utility model also provides a power supply, including the above-mentioned dimming and shutting-off control circuit.

Implementing the power supply dimming and shutdown control circuit and power supply of the utility model has the following beneficial effects: the power supply dimming and shutdown control circuit includes a first switch connected to an external dimming circuit that provides a dimming voltage, respectively connected to the first switch A second switch connected to the output end of a switch, a detection control circuit connected to the second switch, a feedback circuit connected to the detection control circuit, and a PWM regulation circuit connected to the feedback circuit; the first A switch is turned on or off according to the dimming voltage; the output voltage of the output terminal of the power supply supplies power to the detection control circuit through the second switch when the second switch is turned on, and the detection control circuit The circuit outputs a detection control signal to the feedback circuit according to the output voltage, and the feedback circuit outputs a feedback signal to the PWM regulation circuit according to the control signal to turn off the power supply; the second switch is on the first switch On when off. The utility model transfers the output voltage of the power supply to the detection control circuit to supply power to the detection control circuit through the functions of the first switch and the second switch, and makes the output voltage rapidly drop below the cut-off voltage of the LED lamp. The detection and control circuit keeps working, avoiding the phenomenon that the LED light will not flicker when it is turned off, and it can be turned off reliably and stably without adding additional space, with high reliability. Realize rapid shutdown of LED lights without flickering, effectively reduce power consumption, and help the power supply to work reliably for a long time, and there is no flickering in the middle process of fast shutdown and turn-on, and it can also be adjusted from minimum brightness to maximum during the dimming process of LED lights Brightness realizes the purpose of slowly starting the LED lamp and effectively improves the life of the LED lamp.

Description of drawings

The utility model will be further described below in conjunction with accompanying drawing and embodiment, in the accompanying drawing:

Fig. 1 is a structural schematic diagram of the power supply dimming shut-off control circuit of the present invention;

Fig. 2 is a schematic circuit diagram of an embodiment of the power supply dimming and shutdown control circuit of the present invention.

detailed description

In order to make the purpose, technical solution and advantages of the utility model clearer, the utility model will be further described in detail below in conjunction with the accompanying drawings and embodiments.

For the technical problems existing in the prior art, the utility model proposes a power supply dimming shut-off control circuit, the power supply dimming shut-off control circuit is provided with a second switch at the output end of the power supply, and an external dimming voltage is provided. The dimming circuit is provided with a first switch, through the functions of the first switch and the second switch, the output voltage at the output terminal of the power supply can be quickly reduced to turn off the output, and at the same time, the power supply can be quickly turned off, which effectively reduces the power consumption of the power supply and improves the The efficiency, reliability and stability of the power supply are high.

It can be understood that the power supply dimming and shutdown control circuit of the present invention can be applied to the technical field of LED driving power supply, the load can be connected to LED lights, and the connected LED lights can be single lights, string lights, etc. Practical applications need to be selected, and the utility model does not limit this. For example, in the power supply field of LED street lamps, when the LED lights are too bright, the brightness of the LED lights needs to be adjusted, that is, dimming, and the LED lights need to be turned off after the dimming reaches a certain brightness. The dimming and shutdown control circuit of the power supply of the utility model can quickly turn off the LED lights without flickering, and can turn off the LED lights reliably. In the off state, there will be no flickering phenomenon, high reliability and good stability. During the dimming process, the LED light can be turned from the minimum brightness to the maximum brightness, realizing the effect of slowly starting the LED light, and avoiding the instantaneous lighting of the LED The lamp makes the LED lamp reach the maximum brightness in an instant and affects the use of the LED lamp, greatly improving the life of the LED lamp.

As shown in FIG. 1 , in the structure schematic diagram of the power supply dimming and shutdown control circuit of the present invention, the power supply dimming and shutdown control circuit includes a first switch 20 connected to an external dimming circuit that provides a dimming voltage, respectively The second switch 40 connected to the first switch 20 and the output end of the power supply, the detection control circuit 50 connected to the second switch, the feedback circuit 60 connected to the detection control circuit 50 , and the PWM regulation circuit 70 connected to the feedback circuit 60 . Wherein, the first switch 20 is turned on or off according to the magnitude of the dimming voltage; when the output voltage of the power supply output terminal is turned on, the detection control circuit 50 is powered through the second switch, and the detection control circuit 50 is output according to the output voltage. The voltage outputs a detection control signal to the feedback circuit 60, and the feedback circuit 60 outputs a feedback signal to the PWM control circuit 70 according to the detection control signal, and the PWM control circuit 70 adjusts the input terminal of the power supply to turn off the power supply. Preferably, in this embodiment, the second switch 40 is turned on when the first switch 20 is turned off, and when the first switch 20 is turned on, the second switch 40 is turned off, that is, the second switch 40 is in the off state and cannot Work.

Further, the power supply dimming and shutdown control circuit further includes a sampling circuit 10 and a voltage dividing circuit 30 . The sampling circuit 10 is connected between the external dimming circuit and the first switch 10 , and the voltage dividing circuit 30 is connected between the second switch 40 and the output terminal of the power supply.

In this embodiment, the first switch 20 and the second switch 40 are preferably triodes.

specifically:

The sampling circuit 10 is used for sampling the dimming voltage provided by the external dimming circuit, and outputting the sampled voltage to the first switch 20 . It can be understood that the sampling voltage is used as an indication signal for the first switch 20 to be turned on or off. When the sampling voltage reaches the turn-on voltage of the first switch 20, the first switch 20 is turned on. When the sampling voltage is lower than the first switch 20 When the turn-on voltage is , the first switch 20 is turned off. Preferably, in this embodiment, the sampling circuit 10 can be composed of resistors with different resistance values in series, and the number and negative value of the resistors used can be selected and determined according to actual product requirements, which is not limited by the present invention.

The first switch 20 , preferably a triode, is used to turn on or off according to the sampling voltage output by the sampling circuit 10 . Preferably, the sampling voltage is sent to the control terminal of the first switch 20, and the control terminal of the first switch 20 is the base of the triode. At the same time, the first switch 20 can also be used to control the turn-on or turn-off of the second switch 40 . In this embodiment, preferably, when the first switch 20 is turned on, the second switch 40 is turned off; when the first switch 20 is turned off, the second switch 40 is turned on.

The voltage dividing circuit 30 is used to divide the output voltage of the output terminal of the power supply. The output voltage is divided by the voltage dividing circuit 30. When the second switch 40 is turned on, the voltage drop on the second switch 40 can be reduced. Therefore, the second switch 40 is effectively protected when the second switch 40 is turned on, and the second switch 40 is prevented from being damaged due to an over-high output voltage at the moment of turn-on. Preferably, the voltage divider circuit 30 may be composed of resistors with different resistances connected in series, and the resistance value and quantity of the resistors in the voltage divider circuit 30 may be determined according to actual circuit design requirements. In addition, after receiving the output voltage, the voltage dividing circuit 30 can divide the output voltage and output a divided signal to the second switch 40 to turn on the second switch 40 .

The second switch 40 , preferably a triode, is used to turn on according to the voltage dividing signal output by the voltage dividing circuit 30 when the first switch 20 is turned off. Preferably, the second switch 40 is a triode. It can be understood that the divided voltage signal output by the voltage dividing circuit 30 is sent to the control terminal of the second switch 40 (ie, the base of the triode) so as to turn on the second switch 40 . In this embodiment, the turn-on or turn-off of the second switch 40 is controlled by the first switch 20 , and the second switch 40 is turned on only when the first switch 20 is turned off, otherwise it is not turned on.

The detection control circuit 50 is mainly used for monitoring the output voltage of the output terminal of the power supply, and at the same time starting the feedback circuit 60 . That is, when the second switch 40 is turned on, the detection control circuit 50 quickly detects the output voltage according to the output voltage and compares the instantaneous voltage at which the output voltage acts on the detection control circuit 50 with the internal reference voltage of the detection control circuit 50, and outputs The control signal is detected to the feedback circuit 60 to turn on the feedback circuit 60 . It can be understood that when the detected instantaneous voltage is greater than the internal reference voltage of the detection control circuit 50 , the detection control circuit 50 outputs a detection control signal. Preferably, the internal reference voltage of the detection control circuit 50 may be 2.5V. In this embodiment, the detection control signal is a low level signal. Further, when the second switch 40 is turned on, the output voltage of the output terminal of the power supply is also connected to the power supply terminal of the detection control circuit 50 through the second switch 40 to supply power to the detection control circuit 50, so that the detection control circuit 50 always ensures At the working voltage, the detection control circuit 50 is always in the working state, and at the same time, the output voltage quickly drops below the cut-off voltage of the LED lamp, so that the LED lamp can be turned off reliably without flickering. When the output voltage is connected to the detection control circuit 50 through the second switch 40 to supply power to the detection control circuit 50 , the output voltage continues to drop until the working voltage of the detection control circuit 50 remains stable. Preferably, in this embodiment, when the detection control circuit 50 is always in the working state, the detection control circuit 50 continues to output the detection control signal to the feedback circuit 60, and the feedback circuit 60 is always controlled by the detection control circuit. During this process, the power supply Due to the effect of the feedback circuit 60, the input end is always in the off state, and no new energy (that is, no voltage at the input end of the power supply) is delivered to the output end of the power supply.

Further, the detection control circuit 50 includes a control chip, the control chip includes a detection pin and a control pin, and the detection pin is used to detect the output voltage when the second switch 40 is turned on, and the reference voltage set on the detection pin performs In comparison, when the detected voltage is greater than the reference voltage, the control chip control pin outputs a detection control signal to the feedback circuit 60 to start the feedback circuit 60 .

The feedback circuit 60 is configured to be activated when the detection control circuit 50 outputs a detection control signal, and at the same time output a feedback signal to the PWM regulation circuit 70 in the power input terminal after activation. Preferably, the feedback circuit 60 may include a photocoupler. Due to its unique structural characteristics, the optocoupler has the ability to completely isolate the signal field from the main control terminal electrically in actual use, and can transmit electrical signals between different potentials and different impedances, with fast switching speed and small size. It is convenient. Therefore, in this embodiment, the optocoupler is selected as the feedback circuit, which will not affect the work of the load, and can also quickly feed back the signal to the control circuit to reflect the status of the power supply in time when the power supply is overvoltage.

The PWM control circuit 60 is used to control the input terminal of the power supply according to the feedback signal and then turn off the power supply in time, so that the input terminal of the power supply no longer generates a voltage signal, so that no new energy enters the output terminal of the power supply, ensuring that the LED lamp can be reliable. Permanently off without blinking.

As shown in Figure 2, in the circuit schematic diagram of the power supply dimming shutdown control circuit of the present invention:

The sampling circuit 10 includes a resistor R4 and a resistor R21, the resistor R4 and the resistor R21 are connected in series between the external dimming circuit and the reference ground, and the node between the resistor R4 and the resistor R21 is also connected to the first switch 20 . The first switch 20 is a transistor Q3, therefore, the node between the resistor R4 and the resistor R21 is also connected to the base of the first switch 20 and the transistor Q3. Understandably, the resistor R4 and the resistor R21 are connected in series to the external dimming circuit for collecting the dimming voltage output by the external dimming circuit and outputting the collected voltage to the base of the transistor Q3, and when the collected voltage is lower than the base of the transistor Q3 When the turn-on voltage is higher, the transistor Q3 is turned off. Preferably, the collection voltage is the node voltage between the resistor R4 and the resistor R21. In this embodiment, preferably, the resistance values of the resistor R21 and the resistor R4 can be selected and determined according to product requirements.

The first switch 20 is a transistor Q3, the base of the transistor Q3 is connected to the node between the resistors R4 and R21, the collector of the transistor Q3 is connected to the second switch 40, and the emitter of the transistor Q3 is connected to the reference ground. Understandably, the base of the transistor Q3 receives the node voltage between the resistor R4 and the resistor R21, and the transistor Q3 is turned on or off according to the node voltage. In this embodiment, the turn-on voltage of the base of the transistor Q3 may be 0.6V. When the node voltage between the resistor R4 and the resistor R21 is less than 0.6V, the transistor Q3 is turned off, and when the node voltage between the resistor R4 and the resistor R21 is higher than 0.6V, the transistor Q3 is turned on.

The second switch 40 is a transistor Q1, the collector of the transistor Q1 is connected between the resistor R56 and the resistor R3, and the base of the transistor Q1 is connected to the collector of the transistor Q3. Preferably, the turn-on voltage of the base of the transistor Q3 may be 0.6V. In this embodiment, when the first switch 20, that is, the transistor Q3 is turned off, the second switch 40 can be turned on, that is, the emitter and the collector of the transistor Q1 are turned on. R56 is connected to the detection control circuit 50 through the transistor Q1.

The divided voltage 30 includes a resistor R56 and a resistor R3, the first end of the resistor R56 is connected to the output end of the power supply, the second end of the resistor R56 is connected to the first end of the resistor R3, the second end of the resistor R3 is connected to the base of the transistor Q1 The node between the resistor R3 and the transistor Q1 is also connected to the collector of the transistor Q3; the node between the resistor R56 and the resistor R3 is also connected to the collector of the transistor Q1. In this embodiment, if the first switch 20, that is, the transistor Q3 is turned off, the resistor R56 and the resistor R3 divide the output voltage and output the divided signal to the base of the transistor Q1, so that the transistor Q1 is turned on, that is, the first The second switch 40 is turned on. Preferably, the resistance values of the resistor R56 and the resistor R3 are adjustable and can be determined according to actual circuit requirements.

In this embodiment, the power supply dimming and shutdown control circuit further includes a resistor R2, a diode D3, and a capacitor CE1, the anode of the diode D3 is connected to the emitter of the transistor Q1, the cathode of the diode D3 is connected to the positive electrode of the capacitor CE1, and the capacitor The cathode of CE1 is connected to the reference ground, and the node where the cathode of the diode D3 is connected to the anode of the capacitor CE1 is also connected to the detection control circuit 40; the first end of the resistor R2 is connected to the anode of the diode D3, and the second end of the resistor R2 is connected to Detection control circuit 40. Specifically, when the transistor Q1 is turned on, the output voltage at the output terminal of the power supply is connected to the capacitor CE1 through the resistor R56 through the transistor Q1 to charge the capacitor CE1.

The detection control circuit 50 includes a control chip U2 and a resistor R6. The control chip U2 includes a detection pin (PIN2 pin), a control pin (PIN1 pin), and a power supply pin (PIN8 pin). The second end of the resistor R2 is connected to the detection pin of the control chip U2, the first end of the resistor R6 is connected to the control pin of the control chip U2, and the second end of the resistor R6 is connected to the feedback circuit 60; the power supply pin is connected to the diode D3 The node between the cathode of and the anode of capacitor CE1 is connected. Understandably, the output voltage generates an instantaneous voltage through the resistor R2 to the detection pin of the control chip U2, and the detection pin outputs a detection control signal to the resistor R6 according to the instantaneous voltage, and the detection control signal is transmitted to the feedback circuit 60 through the resistor R6 so that the feedback circuit conduction; the output voltage charges the capacitor CE1 through the diode D3 when the transistor Q1 is turned on, and discharges the power supply pin of the control chip U2 through the capacitor CE1 to supply power to the control chip U2 when the power supply is turned off. Specifically, when the transistor Q1 is turned on, the output voltage acts on the detection pin of the control chip U2 through the resistor R2, and the detection pin of the control chip U2 combines the voltage applied by the resistor R2 with the internal reference voltage (2.5 V) for comparison, at this time the voltage is greater than the reference voltage, the control chip U2 controls the control pin to output a detection control signal to the feedback circuit 60 to start the feedback circuit 60, and the feedback circuit 60 outputs the feedback signal to the input end of the power supply to turn off the power source The current on the side turns off the primary side, and the input terminal of the power supply no longer transmits energy to the output terminal of the power supply, and then the control chip U2 is discharged by the capacitor CE1 to supply power to the power supply pin (that is, the PIN8 pin) to provide VCC voltage. In other words, when the triode Q1 is turned on, the output voltage is connected to the VCC power supply pin of the control chip U2 through the triode Q1 to supply power to the control chip U2, so that the VCC power supply pin of the control chip U2 always has an operating voltage. Keep control chip U2 running. That is to say, at this time, the control chip U2 is provided with the VCC voltage (that is, the operating voltage) by the output voltage of the output terminal of the power supply, and the input terminal of the power supply no longer has an effect on the control chip U2. During this process, the output voltage at the output terminal of the power supply continues to drop, that is, the capacitor CE1 is continuously charged until the output voltage reaches below the turn-off voltage of the LED light, and the LED light is reliably turned off, and at the same time the control chip U2 is powered by the output voltage to keep working , that is, the capacitor CE1 is discharged to the power supply pin of the control chip U2 to ensure that the control chip U2 can work normally. Since the control chip U2 is in the normal working state, the control chip U2 continues to output the detection control signal to control the feedback circuit 60 to be in the conduction state, so that no voltage is generated at the input end of the power supply. That is, when the control chip U2 is still working, the primary side of the power supply is always in the off state, and no energy is transmitted to the output terminal of the power supply. Furthermore, it is ensured that the LED light can be turned off reliably without flickering, and since the primary side of the power supply is always in the off state, the energy consumption of the power supply is effectively saved, and the overall efficiency, reliability and stability of the power supply are improved.

Preferably, in this embodiment, the normal working voltage of the control chip U2 is lower than the turn-on voltage of the load LED lamp. Therefore, when the output voltage of the output terminal of the power supply drops to the turn-off voltage of the LED lamp and the LED lamp has been turned off, The output voltage of the output terminal of the power supply can still provide the working voltage for the control chip U2 to keep the control chip U2 working. For example, the LED light is a string of lights, its working voltage is 30V, and 15V is the turn-on voltage of the LED light; and the working voltage of the control chip U2 is generally 5-10V. When the output voltage at the output terminal drops to 15V, the LED light is turned off. At this time, it is still much higher than the operating voltage of the control chip U2. Therefore, the output voltage continues to supply power to the control chip U2 through Q1 (that is, to charge the capacitor CE1, the capacitor CE1 supplies power to the control chip U2), so that the control chip U2 keeps working until the output voltage of the output terminal of the power supply drops to the minimum reliable working voltage of the control chip U2, and the output voltage of the output terminal is stable near the minimum reliable working voltage of the control chip.

The feedback circuit 60 includes a photocoupler U1 and a common anode diode D1, the common anode diode D1 includes a first end, a second end and a third end, the first end of the common anode diode D1 is an anode, and the second end of the common anode diode D1 The first cathode, the third end of the common anode diode D1 is the second cathode; the photocoupler U1 includes a primary light-emitting diode U1-A (not shown in the figure) and a secondary receiving source U1-B (not shown in the figure) ; The first cathode of the common anode diode D1 is connected to the second end of the resistor R6, the anode of the common anode diode D1 is connected to the primary light-emitting diode U1-A of the photocoupler U1, and the output terminal of the secondary receiving source U1-B It is connected with the PWM control circuit 70 . The common anode diode D1 receives the detection control signal transmitted by the resistor R6 and turns on the primary light-emitting diode U1-A of the optocoupler U1 to generate a light source, and the secondary receiving source of the optocoupler U1-B outputs a feedback signal according to the conduction of the light source To the PWM regulation circuit 70, the PWM regulation circuit 70 turns off the power supply according to the feedback signal.

The specific principle of dimming by the dimming and shutting down control circuit of the power supply will be further described below according to FIG. 2 .

In this embodiment, the power supply dimming and shutdown control circuit is applied in the technical field of LED power supplies, and the load is an LED lamp. Assuming that the load is a LED lamp in series, its operating voltage is 30V, its turn-on voltage is 15V, the operating voltage of the control chip U2 is 5V, and the reference voltage of the detection pin of the control chip U2 is 2.5V.

When the LED lamp needs to be dimmed to a certain brightness and then the LED lamp is turned off, the dimming voltage provided to the sampling circuit 10 is adjusted through the external dimming circuit, and the resistor R4 and the resistor R21 in the sampling circuit 10 sample the dimming voltage , output the sampling voltage (ie, the node voltage between the resistor R4 and the resistor R21 ) to the base of the transistor Q3, and when the sampling voltage is lower than 0.6V, the transistor Q3 is turned off. The output voltage of the power supply output terminal (LEDOUT+) outputs a divided signal to the transistor Q1 through the resistor R56 and the resistor R3 to make the transistor Q1 turn on, and the output voltage of LEDOUT+ is transferred to the capacitor CE1 through the transistor Q1 to charge the capacitor CE1, and then the output of LEDOUT+ The voltage quickly drops below the turn-on voltage (i.e. turn-off voltage) of the LED light, the LED light is turned off, and the output voltage of LEDOUT+ acts on the detection pin of the control chip U2 through the resistor R2 when the transistor Q1 is turned on, and the control chip U2 controls its control pin to output a detection control signal after the detection pin detects the action signal, that is, a low-level signal to the resistor R6 to reduce the terminal voltage of the resistor R6, and further lower the voltage drop of the first cathode of the common anode diode D1 The common anode diode D1 is turned on, and then the primary light source U1-A of the photocoupler U1 is turned on to generate a light source, and the secondary receiving source U1-B of the photocoupler U1 is turned on according to the intensity of the light source, and the level of the output terminal is pulled Low, send a low-level feedback signal to the PWM control circuit 70 through the output terminal. After receiving the feedback signal, the PWM control circuit 70 immediately shuts off the primary current at the input terminal of the power supply, so that the input terminal of the power supply stops working and no longer transmits energy to the output of the power supply. Since the primary side of the power supply has been turned off, the control chip U2 cannot receive the power supply voltage provided by the primary side, so the capacitor CE1 discharges to the power supply pin of the control chip U2 to supply power to the control chip U2, that is, the output voltage of LEDOUT+ is transferred to the control chip. The chip U2 supplies power to the control chip U2, so that the control chip U2 keeps working. When the control chip U2 is in the working state, because the photocoupler U1 is always controlled by the control chip U2, the primary side is always turned off, and no energy is delivered to LEDOUT+. Therefore, the LED lamp is reliably turned off and will not be lit (ie There will be no flickering). When the output voltage of LEDOUT+ drops to the VCC voltage of the control chip U2, the output voltage of LEDOUT+ is stable near the VCC voltage of the control chip U2.

It can be understood that the process that the control chip U2 outputs the detection control signal to control the photocoupler U1 to output the feedback signal to the PWM control circuit to turn off the primary side of the power supply is a fast shutdown process. Therefore, the power dimming switch of the utility model The off control circuit can quickly turn off the LED light without flickering problem, and at the same time, after the LED light is turned off, the LED light can be turned off reliably and will not be lit again, and due to the control function of the control chip U2, when the control When the chip U2 is always working, the primary side is always in the off state and will not be started, until the voltage on the capacitor CE1 is lower than the operating voltage of the control chip U2, the photocoupler U1 no longer outputs a feedback signal, and the primary side will restart Send energy to LEDOUT+, when the voltage on LEDOUT+ is slightly higher than the operating voltage of the control chip U2, the control chip U2 regains power to start working and then output the detection control signal again to turn off the primary side, at this time the voltage on LEDOUT+ is still low Due to the turn-on voltage of the LED lamp, the LED lamp is still in the off state, so that the LED lamp can be turned off reliably for a long time.

When it is not necessary to dim or turn off the LED lamp, the dimming voltage is controlled by an external dimming circuit so that the base voltage of the transistor Q3 is higher than 0.6V, and the transistor Q3 is turned on. At this time, Q1 is turned off, and the output voltage of LEDOUT+ The power supply pin and detection pin of the control chip U2 are no longer affected, and the LED lamp is in a normal lighting state, and the power dimming and shutdown control circuit has no effect on the circuit.

The utility model has the advantages of small volume, low cost, high reliability and good stability of the control circuit for power dimming and shutting off of the power supply. Not only can the LED lights be turned off quickly without flickering, but also the LED lights can be turned off reliably for a long time. Effectively prolong the life of LED. In addition, this circuit does not need to add additional occupied space, wiring and control nodes. It uses a full hardware control method with high efficiency and high reliability. When the LED light is turned off, the primary side of the power supply does not work, reducing the The standby loss further improves the efficiency of the product, and has high practicability and productivity.

The utility model also provides a power supply, which includes the aforementioned power supply dimming and shutdown control circuit, the power supply can effectively improve the reliability, stability and practicability of the power supply by applying the power supply dimming and shutdown control circuit, and at the same time It also prolongs the life of the power supply.

The above embodiments are only to illustrate the technical concept and characteristics of the present utility model, and its purpose is to allow those familiar with this technology to understand the content of the present utility model and implement it accordingly, and cannot limit the protection scope of the present utility model. All equivalent changes and modifications made in accordance with the scope of the claims of the utility model shall fall within the scope of the claims of the utility model.

It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should belong to the protection scope of the appended claims of the present utility model.

Claims (10)

1. a kind of power supply light modulation switches off control circuit, it is characterised in that including：

With provide dimmer voltage external dimmer circuit be connected first switch, respectively with the first switch and power output end The second switch of connection, the detection control circuit being connected with the second switch, the feedback being connected with the detection control circuit Circuit and the PWM circuit for regulating and controlling being connected with the feedback circuit；

The first switch is according to the dimmer voltage on or off；

The output voltage of the power output end is controlled when the second switch is turned on by the second switch to the detection Circuit processed is powered, while the detection control circuit is according to output voltage output detection control signal to the feedback electricity Road, the feedback circuit is according to the detection control signal output feedback signal to the PWM circuit for regulating and controlling with power cutoff；Institute Second switch is stated to turn on when the first switch is turned off.

2. power supply light modulation according to claim 1 switches off control circuit, it is characterised in that described also including sample circuit Sample circuit is connected with the external dimmer circuit, and the dimmer voltage and output for gathering the external dimmer circuit offer are adopted Current collection is depressed into the first switch, and the first switch is according to the collection voltages on or off.

3. power supply light modulation according to claim 2 switches off control circuit, it is characterised in that described also including bleeder circuit Bleeder circuit is connected between the output end of the power supply and detection control circuit, for receiving the output voltage and defeated Going out voltage division signal to the second switch turns on the second switch.

4. power supply light modulation according to claim 3 switches off control circuit, it is characterised in that the first switch is triode Q3, the second switch is triode Q1.

5. power supply light modulation according to claim 4 switches off control circuit, it is characterised in that the sample circuit includes resistance R4 and resistance R21, the resistance R4 and the resistance R21 are connected in series between the external dimmer circuit and reference ground, and Node between the resistance R4 and the resistance R21 is additionally coupled to the base stage of the triode Q3；

The resistance R4 and resistance R21 gathers the dimmer voltage of the external dimmer circuit output and exports collection voltages extremely The base stage of the triode Q3, and the collection voltages be less than the triode Q3 base stages cut-in voltage when, the triode Q3 is turned off.

6. power supply light modulation according to claim 4 switches off control circuit, it is characterised in that the bleeder circuit includes resistance R56 and resistance R3, the first end of the resistance R56 is connected with the output end of the power supply, the second end of the resistance R56 and institute State resistance R3 first end connection, the second end of the resistance R3 is connected with the base stage of the triode Q1, the resistance R3 and Node between the triode Q1 is additionally coupled to the colelctor electrode of the triode Q3；The resistance R56 and the resistance R3 it Between node be additionally coupled to the colelctor electrode of the triode Q1；

If the triode Q3 shut-offs, the resistance R56 and resistance R3 carries out partial pressure to the output voltage and exported to divide Press signal to the base stage of the triode Q1, turn on the triode Q1.

7. power supply light modulation according to claim 4 switches off control circuit, it is characterised in that also including resistance R2, diode D3 and electric capacity CE1, the anode of the diode D3 is connected with the emitter stage of the triode Q1, the moon of the diode D3 Pole is connected with the positive pole of the electric capacity CE1, the negative pole connection reference ground of the electric capacity CE1, the negative electrode of the diode D3 and institute The node for stating electric capacity CE1 positive pole connection is additionally coupled to the detection control circuit；The first end of the resistance R2 and described two Pole pipe D3 anode connection, the second end of the resistance R2 is connected to the detection control circuit.

8. power supply light modulation according to claim 7 switches off control circuit, it is characterised in that the detection control circuit includes Control chip and resistance R6；

The control chip includes detection pin, controlling switch and energization pins；

The second end of the resistance R2 is connected with the detection pin of the control chip, the first end of the resistance R6 and the control The controlling switch connection of coremaking piece, the second end of the resistance R6 is connected to the feedback circuit；The energization pins with it is described Node connection between diode D3 negative electrode and the electric capacity CE1 positive pole；

The output voltage produces transient voltage to the detection pin of the control chip by the resistance R2, and the detection is drawn Heel outputs control signals to the resistance R6 according to the transient voltage, is passed the detection control signal by the resistance R6 Delivering to the feedback circuit turns on the feedback circuit；

The output voltage is charged and described when the triode Q1 is turned on by the diode D3 to the electric capacity CE1 When power supply is turned off, the energization pins of the control chip are discharged by the electric capacity CE1 and supplied to the control chip Electricity.

9. power supply light modulation according to claim 8 switches off control circuit, it is characterised in that the feedback circuit includes common anode Diode D1 and photoelectrical coupler U1, the common anode diode D1 include first end, the second end and the 3rd end, the pole of common anode two Pipe D1 first end is anode, and the second end of the common anode diode D1 is the first negative electrode, the 3rd of the common anode diode D1 the Hold as the second negative electrode；The photoelectrical coupler U1 includes first level led U1-A and secondary reception source U1-B；

The first negative electrode of the common anode diode D1 is connected with the second end of the resistance R6, the anode of the common anode diode D1 Be connected with the first level led U1-A of the photoelectrical coupler U1, the output end of the secondary reception source U1-B with it is described PWM circuit for regulating and controlling is connected；

The detection control signal that the first negative electrode of the common anode diode D1 receives the resistance R6 transmission turns on and makes the light Electric coupler U1 first level led U1-A conductings produce light source, the secondary reception source U1-B roots of the photoelectrical coupler U1 Output feedback signal is turned on to the PWM circuit for regulating and controlling according to the light source, and the PWM circuit for regulating and controlling is closed according to the feedback signal Power-off source.

10. a kind of power supply, it is characterised in that switch off control circuit including the light modulation as described in any one of claim 1 to 9.