CN209805958U - active dummy load circuit and electronic equipment - Google Patents

Abstract

The utility model discloses an active dummy load circuit and electronic equipment, include: the first switch module is used for being conducted after receiving a power supply signal of the main board, so that the first output end of the switching power supply circuit is grounded through the first dummy load module, and the second switch module is used for being conducted after receiving a backlight starting signal and controlling the first switch module to be disconnected, so that the first output end of the switching power supply circuit is disconnected with the first dummy load module. The utility model discloses after receiving the opening signal that is shaded for switching power supply circuit's first output can solve the problem that output voltage is high through a dummy load ground connection, and after receiving the TV set opening signal, switching power supply circuit's first output disconnection and first dummy load are connected, and switching power supply circuit gives the load power supply. The utility model discloses in, only solved output voltage through two switch module and wafted high problem, and the device lectotype is simple, and is with low costs, has reduced switching power supply circuit's loss.

Description

Active dummy load circuit and electronic equipment

Technical Field

The embodiment of the utility model provides a relate to power control technical field, especially relate to an active dummy load circuit and electronic equipment.

Background

The conventional switching power supply in the backlight power circuit of the television generally has two paths of outputs, one path of output is sent to a mainboard of the television to supply power to the mainboard, and the other path of output is constant-current voltage to drive an LED lamp of the television. In such a switching power supply, the feedback control circuit generates a feedback voltage by collecting one of the output voltages, thereby realizing control of the switching power supply. And the other path of output voltage is coupled through a winding of the transformer to realize stabilization. Due to the cross-tuning feature, especially in the case of a tv not being turned on, if the main board has extra load, such as: the leisure listening function is turned on, namely the backlight is turned off, and the user listens to music. The voltage output to the LED lamp will be high, so that the LED lamp in the television is already on without starting up, which seriously affects the user experience.

In order to avoid the voltage output to the LED lamp from floating, an active dummy load is conventionally added between the output terminal of the switching power supply and the ground, and cross regulation is realized by connecting a plurality of voltage-stabilizing tubes in series with a resistor. When the output voltage of the switching power supply is floated to be broken down by the voltage stabilizing tube, the output voltage of the switching power supply is clamped through the voltage stabilizing tube and the resistor, and the output voltage of the switching power supply is prevented from floating. The active dummy load needs to select devices of different models according to different backlight specifications, so that the cost is increased, and the leakage current of the voltage regulator tube causes certain loss of the switching power supply regardless of standby or normal operation.

SUMMERY OF THE UTILITY MODEL

in view of this, the utility model provides an active dummy load circuit and electronic equipment to solve current dummy load circuit device model selection difficulty, with high costs, and increase the problem of switching power supply loss.

In a first aspect, an embodiment of the present invention provides an active dummy load circuit, including: the first dummy load module is externally connected with a switching power supply circuit; wherein the content of the first and second substances,

the first switch module is connected with the first dummy load module and used for being conducted after a mainboard power supply signal is received, so that a first output end of the switch power supply circuit is grounded through the first dummy load module;

the second switch module is connected with the first switch module and used for being switched on after receiving a backlight starting signal and controlling the first switch module to be switched off, so that the first output end of the switching power supply circuit is disconnected with the first dummy load module.

Further, the first switch module includes: a first filtering unit and a first transistor unit, wherein,

The first end of the first transistor unit is externally connected with a second output end of the switching power supply circuit, the second end of the first transistor unit is connected with the first end of the first filtering unit and the second switch module respectively, the third end of the first transistor unit is connected with the first dummy load module, and the fourth end of the first transistor unit is connected with the second end of the first filtering unit.

Further, the first transistor unit includes: a first transistor and a first resistor; wherein the content of the first and second substances,

A first end of the first transistor is connected with a first end of the first resistor, a first end of the first filtering unit and the second switch module respectively, a second end of the first transistor is connected with the first dummy load module, and a third end of the first transistor is connected with a second end of the first filtering unit;

and the second end of the first resistor is externally connected with the second output end of the switching power supply circuit.

Further, the second switch module includes: a second filtering unit and a second transistor unit, wherein,

The first end of the second transistor unit is externally connected with a backlight starting circuit, the second end of the second transistor unit is connected with the first end of the second filtering unit, the third end of the second transistor unit is connected with the first end of the first transistor, and the fourth end of the second transistor unit is connected with the second end of the second filtering unit.

Further, the second transistor unit includes: a second transistor and a second resistor; wherein the content of the first and second substances,

a first end of the second transistor is respectively connected with a first end of the second resistor and a first end of the second filtering unit, a second end of the second transistor is connected with a first end of the first transistor, and a third end of the second transistor is connected with a second end of the second filtering unit;

And the second end of the second resistor is externally connected with a backlight starting circuit.

Further, the circuit further comprises: a second dummy load module; wherein the content of the first and second substances,

the second dummy load module is respectively connected with the first transistor and the second transistor, and is used for enabling the first output end of the switching power supply circuit to be grounded after being connected in series with the second transistor through the second dummy load module after the second transistor is conducted.

Further, the second dummy load module includes: a third resistor and a first diode; wherein the content of the first and second substances,

The first end of the third resistor is externally connected with the first output end of the switching power supply circuit, and the second end of the third resistor is respectively connected with the cathode of the first diode and the second end of the second transistor;

an anode of the first diode is connected to a first terminal of the first transistor.

Further, the first switch module includes: a third filtering unit and a third transistor unit, wherein,

The first end of the third transistor unit is externally connected with the second output end of the switching power supply circuit, the second end of the third transistor unit is connected with the first end of the third filtering unit, the third end of the third transistor unit is connected with the first dummy load module, and the fourth end of the third transistor unit is connected with the second switch module.

further, the third transistor unit includes: a third transistor and a fourth resistor; wherein the content of the first and second substances,

a first end of the third transistor is respectively connected with a first end of the fourth resistor and a first end of the third filtering unit, a second end of the third transistor is connected with the first dummy load module, and a third end of the third transistor is connected with the second switch module;

And the second end of the fourth resistor is externally connected with the second output end of the switching power supply circuit.

Further, the second switch module includes: a fourth filtering unit and a fourth transistor unit, wherein,

The first end of the fourth transistor unit is externally connected with a backlight starting circuit, the second end of the fourth transistor unit is connected with the first end of the fourth filtering unit, the third end of the fourth transistor unit is connected with the second end of the fourth filtering unit, and the fourth end of the fourth transistor unit is connected with the third end of the third transistor.

further, the fourth transistor unit includes: a fourth transistor and a fifth resistor; wherein the content of the first and second substances,

a first end of the fourth transistor is respectively connected with a first end of the fifth resistor and a first end of the fourth filtering unit, a second end of the fourth transistor is connected with a second end of the fourth filtering unit, and a third end of the fourth transistor is connected with a third end of the third transistor;

And the second end of the fifth resistor is externally connected with the backlight starting circuit.

In a second aspect, the present invention further provides an electronic device, which includes the active dummy load circuit according to any one of the first aspect.

The embodiment of the utility model provides a pair of active dummy load circuit and electronic equipment, include: the first switch module is connected with the first dummy load module and used for being conducted after a mainboard power supply signal is received, so that the first output end of the switching power supply circuit is grounded through the first dummy load module, the second switch module is connected with the first switch module and used for being conducted after a backlight starting signal is received, the first switch module is controlled to be disconnected, and the first output end of the switching power supply circuit is disconnected with the first dummy load module. According to the technical scheme, after the backlight starting signal is received, the first switch module is switched on, the first output end of the switching power supply circuit is grounded through the first dummy load module, the problem that the voltage of the output end is high can be solved, after the television starting signal is received, the first switch module is switched off, the first output end of the switching power supply circuit is disconnected from the first dummy load module, power is supplied to a load, and the switching power supply circuit is normally used. In the embodiment, the problem of high voltage at the output end can be solved only by the two switch modules, the device is simple in type selection and low in cost, and the loss of the switch power supply circuit is reduced.

Drawings

Fig. 1 is a schematic block diagram of an active dummy load circuit according to a first embodiment of the present invention;

Fig. 2 is a topology diagram of an active dummy load circuit according to a second embodiment of the present invention;

fig. 3 is a topology diagram of an optimized active dummy load circuit according to a second embodiment of the present invention;

fig. 4 is a topology diagram of another active dummy load circuit according to a third embodiment of the present invention.

Detailed Description

the present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures. In addition, the embodiments and features of the embodiments in the present invention may be combined with each other without conflict.

Example one

Fig. 1 is a schematic block diagram of an active dummy load circuit according to a first embodiment of the present invention; the present embodiment is applicable to a case where the output voltage of the switching power supply circuit, which is disposed in the switching power supply device, is suppressed from floating high.

Specifically, as shown in fig. 1, the active dummy load circuit mainly includes: the first switch module 110, the second switch module 120 and the first dummy load module 130, the first dummy load module 130 is externally connected with a switch power circuit 140.

the first switch module 110 is connected to the first dummy load module 130, and is configured to be turned on after receiving the motherboard power supply signal, so that the first output terminal of the switching power supply circuit 140 is grounded through the first dummy load module 130.

The second switch module 120 is connected to the first switch module 110, and configured to be turned on after receiving the backlight-on signal, and control the first switch module 110 to be turned off, so that the first output terminal of the switching power supply circuit 140 is disconnected from the first dummy load module.

The switching power supply circuit 140 controls the output voltage and stabilizes the output by controlling the on-time of the switching tube, that is, the duty ratio of the PWM signal for controlling the on-time of the switching tube determines the magnitude of the output voltage. However, when the output voltage of the switching power supply circuit 140 is high during idling, a resistor similar to a load, which is usually called a dummy load, is connected in parallel to the output terminal in order to make the output voltage reach a stable value.

in this embodiment, the first dummy load module 130 may be understood as a dummy load connected in parallel to the output terminal of the switching power supply circuit. Further, the first dummy load module 130 may include a first dummy load resistor, and the resistance value of the first dummy load resistor is preferably 10 kilo-ohms. In this embodiment, one end of the first dummy load module 130 is connected to the first output terminal of the switching power supply circuit, and the other end is connected to the first switch module 110.

one end of the first switch module 110 is grounded and is used for being turned on when the switching power supply circuit 140 is in a no-load state, and at this time, the other end of the first dummy load module 130 is grounded through the first switch module 110, so that the switching power supply circuit 140 and the first dummy load module 130 form a loop, and the problem that the first output voltage is higher when the first output end of the switching power supply circuit 140 is in a no-load state is solved.

further, the second switch module 120 is connected to the first switch module 110, and is configured to control the first switch module 110 to be turned off when the switching power supply circuit 140 needs to supply power to the load, and cut off a loop among the switching power supply circuit 140, the first switch module 110, and the first dummy load module 130, so that the switching power supply circuit 140 can normally operate to provide a constant output voltage to the load.

First, it should be noted that the switching power supply circuit 140 in this embodiment has two output terminals, and the first output terminal is used for outputting the first output voltage to supply power to the LED lamp of the television. The second output end is used for outputting a second output voltage and supplying power to a mainboard of the television. Wherein the first output voltage is greater than the second output voltage.

In this embodiment, the motherboard power supply signal may be understood as a signal generated when the motherboard of the television is powered on and starts to operate, but the display screen of the television is not turned on. For example: the television is in a leisure listening mode, namely, the backlight display of the television is turned off, and only music is listened.

Since the second output terminal of the switching power supply circuit 140 needs to supply power to the motherboard, the motherboard operates in the easy listening mode. The switching power supply circuit 140 starts to work, wherein the second output terminal outputs the second output voltage to the tv motherboard to generate a motherboard power supply signal. At this time, the television turns off the backlight display, and the first output terminal of the switching power supply circuit 140 is idle, so that the first output voltage outputted by the first output terminal of the switching power supply circuit 140 is high. At this time, the first switch module 110 is turned on after receiving the main board power supply signal, so that the first output terminal of the switching power supply circuit 140 and the first dummy load module 130 form a loop, thereby avoiding the problem of high output voltage when the switching power supply circuit 140 is idle.

When the television is turned on, the first output terminal of the switching power supply circuit 140 needs to provide a stable power supply voltage to the LED lamp. That is, when the television is turned on, the switching power supply circuit 140 generates a first output voltage and outputs the first output voltage to the LED lamp. Further, when the television is turned on, a backlight turn-on signal is generated, and the second switch module 120 is turned on after receiving the backlight turn-on signal, so as to control the first switch module 110 to be turned off, and to cut off a loop among the switching power supply circuit 140, the first switch module 110, and the first dummy load module 130, so that the switching power supply circuit 140 can normally operate to provide a constant first output voltage for the LED lamp.

it should be noted that, in this embodiment, only the first switch module and the second switch module are described, but not limited to these, and the specific topologies of the first switch module and the second switch module may be designed according to actual situations.

the embodiment of the utility model provides an active dummy load circuit, include: the first switch module is connected with the first dummy load module and used for being conducted after a mainboard power supply signal is received, so that the first output end of the switching power supply circuit is grounded through the first dummy load module, the second switch module is connected with the first switch module and used for being conducted after a backlight starting signal is received, the first switch module is controlled to be disconnected, and the first output end of the switching power supply circuit is disconnected with the first dummy load module. According to the technical scheme, after the backlight starting signal is received, the first switch module is switched on, the first output end of the switching power supply circuit is grounded through the first dummy load module, the problem that the voltage of the output end is high can be solved, after the television starting signal is received, the first switch module is switched off, the first output end of the switching power supply circuit is disconnected from the first dummy load module, power is supplied to a load, and the switching power supply circuit is normally used. In the embodiment, the problem of high voltage at the output end can be solved only by the two switch modules, the device is simple in type selection and low in cost, and the loss of the switch power supply circuit is reduced.

example two

On the basis of the above embodiments, the present embodiment provides a specific topology structure of an active dummy load circuit, and fig. 2 is a topology structure diagram of an active dummy load circuit in the second embodiment of the present invention.

as shown in fig. 2, the first switching module includes: the first filter unit 112 and the first transistor unit 111, wherein a first end of the first transistor unit 111 is externally connected to the second output terminal STB of the switching power supply circuit 140, a second end of the first transistor unit 111 is respectively connected to the first end of the first filter unit 112 and the second switch module 120, a third end of the first transistor unit 111 is connected to the first dummy load module 130, and a fourth end of the first transistor unit 111 is connected to the second end of the first filter unit 112.

Further, the first transistor unit 111 includes: a first transistor Q1 and a first resistor R1, wherein a first end of the first transistor Q1 is respectively connected to a first end of the first resistor R1, a first end of the first filtering unit 112 and the second switching module 120, a second end of the first transistor Q2 is connected to the first dummy load module 130, and a third end of the first transistor Q1 is connected to the second end of the first filtering unit 112 and grounded; a second terminal of the first resistor R1 is externally connected to a second output terminal STB of the switching power supply circuit 140.

In this embodiment, the first dummy load module 130 is preferably a first dummy load resistor R01, one end of the first dummy load resistor R01 is connected to the first output terminal LED + of the switching power supply circuit 140, and the other end of the first dummy load resistor R01 is connected to the second end of the first transistor Q1.

in this embodiment, the first transistor Q1 is preferably an NPN transistor, the first terminal of the first transistor Q1 is a base of the NPN transistor, the second terminal of the first transistor Q1 is a collector of the NPN transistor, and the third terminal of the first transistor Q1 is an emitter of the NPN transistor. In the present embodiment, only the first transistor Q1 is described, but not limited thereto, and other transistors may be selected as appropriate.

Further, the first resistor R1 is a current limiting resistor of the first transistor Q1, and is used to prevent the current flowing into the base of the first transistor Q1 from being too large and burning out the first transistor Q1.

Further, the first filtering unit 112 includes a first capacitor C1 and a sixth resistor R6, one end of the first capacitor C1 is connected to the first end of the first transistor Q1, and the other end of the first capacitor C1 is connected to the third end of the first transistor Q1. One end of the sixth resistor R6 is connected to the first end of the first transistor Q1, and the other end of the sixth resistor R6 is connected to the third end of the first transistor Q1.

in this embodiment, the sixth resistor R6 is a voltage dividing resistor of the first transistor Q1, and is used to form a base voltage dividing resistor with the first resistor R1, so as to stabilize the base bias voltage, reduce the influence of temperature on the operating quiescent point, and suppress the drift of the zero point. The first capacitor C1 is used for filtering the interference signal flowing into the first transistor Q1, so as to improve the anti-interference capability of the system.

The switching power supply circuit 140 starts to work, the second output end STB outputs a second output voltage to the tv main board, and generates a main board power supply signal, which is input to the first end of the first transistor Q1 through the first resistor R1 to trigger the first transistor Q1 to be turned on, so that the first output end LED + of the switching power supply circuit 140, the first dummy load resistor R01 and the first transistor Q1 form a loop, and the problem of high output voltage when the first output end LED + of the switching power supply circuit 140 is idle is avoided.

Further, the second switch module 120 includes: a second filtering unit 122 and a second transistor unit 121, wherein a first end of the second transistor unit 121 is externally connected to the backlight starting circuit 150, a second end of the second transistor unit 121 is connected to a first end of the second filtering unit 122, a third end of the second transistor unit 121 is connected to a first end of the first transistor Q1, and a fourth end of the second transistor unit 121 is connected to a second end of the second filtering unit 122.

Further, the second transistor unit 121 includes: a second transistor Q2 and a second resistor R2; a first end of the second transistor Q2 is connected to a first end of the second resistor R2 and a first end of the second filter unit 121, respectively, a second end of the second transistor Q2 is connected to a first end of the first transistor Q1, and a third end of the second transistor Q2 is connected to a second end of the second filter unit 122; the second end of the second resistor R2 is externally connected to the backlight-on circuit 150.

It should be noted that the backlight turning-on circuit 150 is used for turning on a backlight power supply of the television, so that the display screen of the television is started.

in this embodiment, the second transistor Q2 is preferably an NPN transistor, the first end of the second transistor Q2 is a base of the NPN transistor, the second end of the second transistor Q2 is a collector of the NPN transistor, and the third end of the second transistor Q2 is an emitter of the NPN transistor. In the present embodiment, only the second transistor Q2 is described, but not limited thereto, and other transistors may be selected according to actual circumstances.

Further, the second resistor R2 is a current limiting resistor of the second transistor Q2, and is used to prevent the current flowing into the base of the second transistor Q2 from being too large and burning out the second transistor Q2.

further, the second filtering unit 122 includes a second capacitor C2 and a seventh resistor R7, one end of the second capacitor C2 is connected to the first end of the second transistor Q2, and the other end of the second capacitor C2 is connected to the third end of the second transistor Q2. One end of the seventh resistor R7 is connected to the first end of the second transistor Q2, and the other end of the seventh resistor R7 is connected to the third end of the second transistor Q2.

In this embodiment, the seventh resistor R7 is a voltage dividing resistor of the second transistor Q2, and is used to form a base voltage dividing resistor with the second resistor R2, so as to stabilize the base bias voltage, reduce the influence of temperature on the operating quiescent point, and suppress the drift of the zero point. The second capacitor C2 is used for filtering interference signals of the signal flowing into the second transistor Q2, so that the interference rejection of the signal is improved.

when the television is turned on, the backlight turn-on circuit 150 generates a backlight turn-on signal, and inputs the backlight turn-on signal to the base of the second transistor Q2 through the second resistor R2 to trigger the second transistor Q2 to be turned on, at this time, the base of the first transistor Q1 is grounded through the second transistor Q2, that is, the base voltage of the first transistor Q1 is pulled low, the first transistor Q1 is turned off, and the loop formed by the first output terminal LED + of the switching power supply circuit 140 and the first transistor Q1 is turned off, so that the first output terminal of the switching power supply circuit 140 supplies power to the LED lamp.

On the basis of the above embodiments, the present embodiment optimizes the above active dummy load circuit. Fig. 3 is a topology diagram of an optimized active dummy load circuit according to a second embodiment of the present invention. As shown in fig. 3, a second dummy load module 160 is added on the basis of the above active dummy load circuit; the second dummy load module 160 is respectively connected to the first transistor Q1 and the second transistor Q2, and is configured to enable the first output terminal of the switching power supply circuit 140 to be grounded after the second transistor Q2 is turned on and is connected in series with the second dummy load module 160 and the second transistor Q2.

Specifically, the second dummy load module 160 includes: a third resistor R3 and a first diode D1; a first end of the third resistor R3 is externally connected to the first output end LED + of the switching power supply circuit 140, and a second end of the third resistor R3 is connected to a cathode of the first diode D1 and a second end of the second transistor Q2, respectively; an anode of the first diode D1 is connected to a first terminal of a first transistor Q1.

In this embodiment, when the television is turned on, the backlight turning-on circuit 150 generates a backlight turning-on signal, and inputs the backlight turning-on signal to the base of the second transistor Q2 through the second resistor R2 to trigger the second transistor Q2 to turn on, at this time, the base of the first transistor Q1 is grounded through the second transistor Q2, that is, the base voltage of the first transistor Q1 is pulled low, the first transistor Q1 is turned off, the loop formed by the first output terminal LED + of the switching power supply circuit 140 and the first transistor Q1 is disconnected, and at the same time, the first output terminal LED + of the switching power supply circuit 140 is grounded through the third resistor R3 and the second transistor Q2. The first output voltage output by the first output terminal LED + of the switching power supply circuit 140 can be adjusted by the third resistor R3, so as to avoid the problem that the first output voltage output by the first output terminal LED + is higher when the load of the second output terminal is too heavy and the load of the first output terminal is light.

Further, the first diode D1 is used to solve the problem that when the first output terminal LED + of the power-off circuit 140 is grounded through the third resistor R3, the first transistor Q1 is triggered to turn on by mistake.

EXAMPLE III

On the basis of the above embodiments, the present embodiment provides a specific topology structure of an active dummy load circuit, and fig. 4 is a topology structure diagram of another active dummy load circuit in the third embodiment of the present invention.

As shown in fig. 4, the first switch module 110 includes: a third filtering unit 114 and a third transistor unit 113, wherein a first end of the third transistor unit 113 is externally connected to the second output terminal STB of the switching power supply circuit 140, a second end of the third transistor unit 113 is connected to the first end of the third filtering unit 114, a third end of the third transistor unit 113 is connected to the first dummy load module 130, and a fourth end of the third transistor unit 113 is connected to the second switching module 120.

further, the third transistor unit 113 includes: a third transistor Q3 and a fourth resistor R4; a first end of the third transistor Q3 is connected to the first end of the fourth resistor R4 and the first end of the third filtering unit 114, respectively, a second end of the third transistor Q3 is connected to the first dummy load module 130, and a third end of the third transistor Q3 is connected to the second switch module 120; a second terminal of the fourth resistor R4 is externally connected to the second output terminal STB of the switching power supply circuit 140.

in this embodiment, the third transistor Q3 is preferably an NPN type triode, the first end of the third transistor Q3 is a base of the NPN type triode, the second end of the third transistor Q3 is a collector of the NPN type triode, and the third end of the third transistor Q3 is an emitter of the NPN type triode. In the present embodiment, only the third transistor Q3 is described, but not limited thereto, and other transistors may be selected as appropriate.

Further, the fourth resistor R4 is a current limiting resistor of the third transistor Q3, and is used to prevent the current flowing into the base of the third transistor Q3 from being too large and burning out the third transistor Q3.

Further, the third filtering unit 114 includes a third capacitor C3 and an eighth resistor R8, one end of the third capacitor C3 is connected to the first end of the third transistor Q3, and the other end of the third capacitor C3 is connected to the third end of the third transistor Q3. One end of the eighth resistor R8 is connected to the first end of the third transistor Q3, and the other end of the eighth resistor R8 is connected to the third end of the third transistor Q3.

In this embodiment, the eighth resistor R8 is a voltage dividing resistor of the third transistor Q3, and is used to form a base voltage dividing resistor with the fourth resistor R4, so as to stabilize the base bias voltage, reduce the influence of temperature on the operating quiescent point, and suppress the drift of the zero point. The third capacitor C3 is used for filtering interference signals of the signal flowing into the third transistor Q3, so as to improve the interference rejection of the signal.

Further, the second switch module 122 includes: a fourth filtering unit 124 and a fourth transistor unit 123, wherein a first end of the fourth transistor unit 123 is externally connected to the backlight starting circuit, a second end of the fourth transistor unit 123 is connected to the first end of the fourth filtering unit 124, a third end of the fourth transistor unit 123 is connected to the second end of the fourth filtering unit 124, and a fourth end of the fourth transistor unit 123 is connected to the third end of the third transistor Q3.

Further, the fourth transistor unit 123 includes: a fourth transistor Q4 and a fifth resistor R5; a first end of the fourth transistor Q4 is connected to the first end of the fifth resistor R5 and the first end of the fourth filtering unit 124, respectively, a second end of the fourth transistor Q2 is connected to the second end of the fourth filtering unit 124, and a third end of the fourth transistor Q4 is connected to the third end of the third transistor Q3; the second end of the fifth resistor R5 is externally connected to the backlight-on circuit 150.

In this embodiment, the fourth transistor Q4 is preferably a PNP transistor, the first terminal of the fourth transistor Q4 is a base of the PNP transistor, the second terminal of the fourth transistor Q4 is a collector of the PNP transistor, and the third terminal of the fourth transistor Q4 is an emitter of the PNP transistor. In the present embodiment, only the fourth transistor Q4 is described without limitation, and other transistors may be selected as appropriate.

the switching power supply circuit 140 starts to operate, the second output terminal outputs STB second output voltage to the tv main board, and generates a main board power supply signal, which is input to the first terminal of the third transistor Q3 through the fourth resistor R4 to trigger the third transistor Q3 to be turned on, and at the same time, the fourth transistor Q4 is turned on, so that the first output terminal LED + of the switching power supply circuit 140 sequentially passes through the first dummy load resistor R01, the third transistor Q3 and the fourth transistor Q4 and then is grounded. Therefore, the problem of high output voltage when the first output end LED + of the switching power supply circuit 140 is idle can be avoided.

When the television is turned on, the backlight turn-on circuit 150 generates a backlight turn-on signal, and inputs the backlight turn-on signal to the base of the fourth transistor Q4 through the fifth resistor R5 to trigger the turn-off of the fourth transistor Q4, at this time, the first output terminal LED + of the switching power supply circuit 140 is disconnected from the circuit grounded through the first dummy load resistor R01, so that the first output terminal of the switching power supply circuit 140 supplies power to the LED lamp.

An embodiment of the present invention further provides an electronic device, which includes the active dummy load circuit as provided in the above embodiments.

Above-mentioned equipment is executable the utility model discloses the power control circuit that arbitrary embodiment provided possesses corresponding functional module of executive circuit and beneficial effect.

It should be noted that the foregoing is only a preferred embodiment of the present invention and the technical principles applied. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail with reference to the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the scope of the present invention.

Claims (12)

1. An active dummy load circuit, comprising: the first dummy load module is externally connected with a switching power supply circuit; wherein the content of the first and second substances,

The first switch module is connected with the first dummy load module and used for being conducted after a mainboard power supply signal is received, so that the first output end of the switch power supply circuit is grounded through the first dummy load module;

The second switch module is connected with the first switch module and used for being switched on after receiving a backlight starting signal and controlling the first switch module to be switched off, so that the first output end of the switching power supply circuit is disconnected with the first dummy load module.

2. The active dummy load circuit of claim 1 wherein the first switch module comprises: a first filtering unit and a first transistor unit, wherein,

The first end of the first transistor unit is externally connected with a second output end of the switching power supply circuit, the second end of the first transistor unit is connected with the first end of the first filtering unit and the second switch module respectively, the third end of the first transistor unit is connected with the first dummy load module, and the fourth end of the first transistor unit is connected with the second end of the first filtering unit.

3. The active dummy load circuit of claim 2, wherein the first transistor unit comprises: a first transistor and a first resistor; wherein the content of the first and second substances,

A first end of the first transistor is connected with a first end of the first resistor, a first end of the first filtering unit and the second switch module respectively, a second end of the first transistor is connected with the first dummy load module, and a third end of the first transistor is connected with a second end of the first filtering unit;

and the second end of the first resistor is externally connected with the second output end of the switching power supply circuit.

4. The active dummy load circuit of claim 3 wherein the second switch module comprises: a second filtering unit and a second transistor unit, wherein,

The first end of the second transistor unit is externally connected with a backlight starting circuit, the second end of the second transistor unit is connected with the first end of the second filtering unit, the third end of the second transistor unit is connected with the first end of the first transistor, and the fourth end of the second transistor unit is connected with the second end of the second filtering unit.

5. The active dummy load circuit of claim 4, wherein the second transistor unit comprises: a second transistor and a second resistor; wherein the content of the first and second substances,

A first end of the second transistor is respectively connected with a first end of the second resistor and a first end of the second filtering unit, a second end of the second transistor is connected with a first end of the first transistor, and a third end of the second transistor is connected with a second end of the second filtering unit;

And the second end of the second resistor is externally connected with the backlight starting circuit.

6. The active dummy load circuit of claim 5 wherein the circuit further comprises: a second dummy load module; wherein the content of the first and second substances,

The second dummy load module is respectively connected with the first transistor and the second transistor, and is used for enabling the first output end of the switching power supply circuit to be grounded after being connected in series with the second transistor through the second dummy load module after the second transistor is conducted.

7. The active dummy load circuit of claim 6 wherein the second dummy load module comprises: a third resistor and a first diode; wherein the content of the first and second substances,

the first end of the third resistor is externally connected with the first output end of the switching power supply circuit, and the second end of the third resistor is respectively connected with the cathode of the first diode and the second end of the second transistor;

An anode of the first diode is connected to a first terminal of the first transistor.

8. The active dummy load circuit of claim 1 wherein the first switch module comprises: a third filtering unit and a third transistor unit, wherein,

The first end of the third transistor unit is externally connected with the second output end of the switching power supply circuit, the second end of the third transistor unit is connected with the first end of the third filtering unit, the third end of the third transistor unit is connected with the first dummy load module, and the fourth end of the third transistor unit is connected with the second switch module.

9. The active dummy load circuit of claim 8, wherein the third transistor unit comprises: a third transistor and a fourth resistor; wherein the content of the first and second substances,

A first end of the third transistor is respectively connected with a first end of the fourth resistor and a first end of the third filtering unit, a second end of the third transistor is connected with the first dummy load module, and a third end of the third transistor is connected with the second switch module;

And the second end of the fourth resistor is externally connected with the second output end of the switching power supply circuit.

10. The active dummy load circuit of claim 9, wherein the second switching module comprises: a fourth filtering unit and a fourth transistor unit, wherein,

the first end of the fourth transistor unit is externally connected with a backlight starting circuit, the second end of the fourth transistor unit is connected with the first end of the fourth filtering unit, the third end of the fourth transistor unit is connected with the second end of the fourth filtering unit, and the fourth end of the fourth transistor unit is connected with the third end of the third transistor.

11. the active dummy load circuit of claim 10, wherein the fourth transistor unit comprises: a fourth transistor and a fifth resistor; wherein the content of the first and second substances,

A first end of the fourth transistor is respectively connected with a first end of the fifth resistor and a first end of the fourth filtering unit, a second end of the fourth transistor is connected with a second end of the fourth filtering unit, and a third end of the fourth transistor is connected with a third end of the third transistor;

and the second end of the fifth resistor is externally connected with the backlight starting circuit.

12. An electronic device, characterized in that it comprises an active dummy load circuit according to any of claims 1 to 11.