A circuit for reducing standby power consumption of a PFC circuit

Abstract

The present invention relates to the field of LED control device circuits, and provides a circuit for reducing the standby power consumption of a PFC circuit, comprising a PFC control chip, a PFC circuit, a load circuit and a PFC standby power consumption circuit, wherein the input end of the PFC circuit is connected to a DC power input, and the output end supplies power to an LED load through the load circuit to improve the overall power factor, the PFC control chip is connected to the PFC circuit to control the working state of the PFC circuit, and the output end of the PFC standby power consumption circuit is connected to an FB pin of the PFC control chip, so that when standby is required, a voltage higher than 2.5V is provided to the FB pin of the PFC control chip, so that an internal error amplifier of the PFC control chip outputs a low level, and an internal PWM control output of the PFC control chip is turned off; the present invention turns off the boost of the PFC circuit through the FB pin, meets low standby power consumption, avoids the timing problem caused by the restart of the PFC power supply, and enables the LED control device whose power supply adopts the circuit structure to effectively reduce the standby power consumption.

Description

Technical Field

[0001] The present invention relates to the field of LED control device circuits, and in particular to a circuit for reducing the standby power consumption of a PFC circuit. Background Art

[0002] With the development of society and the demand for energy conservation, the use of LED lamps is becoming more and more widespread. In order to improve the power factor, the power supply of LED lamps usually adds a PFC circuit to improve the power factor and meet the requirements of industry standards.

[0003] At present, various countries require the standby power consumption of standard LED devices to be less than 0.5W. Due to the large number of LED lamps and the large base, even if the standby power consumption of each lamp is less than 0.5W, the comprehensive loss is still large, which is contrary to low carbon emissions. Therefore, standby power consumption less than 0.3W has become an industry trend. The traditional circuit design with PFC has a large standby power consumption, which is not conducive to energy conservation and emission reduction. Therefore, it is necessary to optimize the design of PFC standby. The common measure in the LED control device industry is to turn off the Vcc power supply of the PFC chip to shut down the PFC circuit to achieve the purpose of reducing the standby function. However, after the power supply of the PFC chip is cut off, the power-on timing problem needs to be considered when restarting. The circuit design is relatively complex and the stability is poor. Summary of the invention

[0004] The problem solved by the present invention is how to provide a circuit for reducing the standby power consumption of the PFC circuit by turning off the boost of the PFC circuit through the FB pin to meet the low standby power consumption and avoid the timing problem caused by the power restart of the PFC.

[0005] To solve the above problems, the present invention provides a circuit for reducing the standby power consumption of a PFC circuit, comprising: a PFC control chip, a PFC circuit, a load circuit and a PFC standby power consumption circuit, wherein the input end of the PFC circuit is connected to a DC power input, and the output end supplies power to an LED load through the load circuit to improve the overall power factor, the PFC control chip is connected to the PFC circuit to control the working state of the PFC circuit, and the output end of the PFC standby power consumption circuit is connected to the FB pin of the PFC control chip to provide a voltage higher than 2.5V to the FB pin of the PFC control chip when standby is required, so that the internal error amplifier of the PFC control chip outputs a low level, and the internal PWM control output of the PFC control chip is turned off.

[0006] Furthermore, the PFC standby power consumption circuit includes an MCU chip and a first diode, a switch output end of the MCU chip is connected to the anode of the first diode, and a cathode of the first diode is connected to the FB pin of the PFC control chip. When in standby mode, the switch output end of the MCU chip outputs a high-level signal to the FB pin of the PFC control chip through the first diode, and when working, the switch output end of the MCU chip outputs a low-level signal to the FB pin of the PFC control chip through the first diode.

[0007] Further, the PFC circuit includes a first energy storage inductor, a second diode, a first capacitor and a voltage feedback loop, wherein a first end of the first energy storage inductor is connected to a DC power supply input, a second end is connected to a first end of the first capacitor via the second diode, a second end of the first capacitor is grounded, the second end of the first energy storage inductor is connected to a switch tube inside the PFC control chip, and grounding is controlled by the PFC control chip to implement PFC control, a detection end of the voltage feedback loop is connected to the first end of the first capacitor, and an output end is connected to an FB pin of the PFC control chip.

[0008] Further, the voltage feedback loop includes a voltage-dividing resistor group, the voltage-dividing resistor group includes a plurality of resistors connected in series, a first end of the voltage-dividing resistor group is connected to a first end of the first capacitor, a second end is grounded, and a voltage-dividing node of the voltage-dividing resistor group is connected to an FB pin of the PFC control chip.

[0009] Furthermore, the PFC circuit also includes a third diode, an anode of the third diode is connected to the first end of the first energy storage inductor, and a cathode is connected to the cathode of the second diode, and the third diode plays a role of shunt protection.

[0010] Furthermore, the PFC circuit also includes a second capacitor, a first end of the second capacitor is connected to the first end of the first energy storage inductor, and a second end of the second capacitor is connected to the cathode of the second diode.

[0011] Furthermore, it also includes a pre-protection rectifier module, the input end of the pre-protection rectifier module is connected to the external AC mains, and the output end is connected to the input end of the PFC circuit, for providing a DC input to the PFC circuit.

[0012] Furthermore, the pre-protection rectifier module includes a protection circuit, an EMC filter circuit and a rectifier bridge circuit, the input end of the protection circuit is connected to the AC mains input port for input overcurrent and overvoltage protection, the input end of the EMC filter circuit is connected to the output end of the protection circuit for reducing electromagnetic interference, the input end of the rectifier bridge circuit is connected to the output end of the EMC filter circuit, and the output end is connected to the input end of the PFC circuit for converting the AC power input to provide a DC power supply for the PFC circuit.

[0013] Furthermore, the pre-protection rectifier module also includes a third capacitor, and the third capacitor is connected in parallel between two output ends of the rectifier bridge circuit.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] When standby mode is required, the PFC standby power consumption circuit provides a voltage higher than 2.5V to the FB pin of the PFC control chip, so that the internal error amplifier of the PFC control chip outputs a low level. After the PFC internal control center receives the low level signal, its control logic will turn off the internal PWM control output, and the PFC is equivalent to not working. At the same time, the internal voltage of the system is reduced, thereby achieving the purpose of reducing power consumption and avoiding the timing problem caused by the restart of the PFC VCC power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the overall structure of an embodiment of the present invention;

[0017] Figure 2 It is a schematic diagram of the overall circuit principle of an embodiment of the present invention;

[0018] Figure 3 FIG. 4 is a partial internal schematic diagram of a PFC control chip according to an embodiment of the present invention. DETAILED DESCRIPTION

[0019] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0020] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0021] In the description of this specification, the description with reference to the terms "embodiment", "one embodiment" and "one implementation" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or implementation are included in at least one embodiment or implementation of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or implementation. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or implementations in a suitable manner.

[0022] like Figure 1 As shown, the present invention provides a circuit for reducing the standby power consumption of a PFC circuit, comprising: a PFC control chip, a PFC circuit, a load circuit and a PFC standby power consumption circuit, wherein the input end of the PFC circuit is connected to a DC power input, and the output end supplies power to an LED load through the load circuit to improve the overall power factor, the PFC control chip is connected to the PFC circuit to control the working state of the PFC circuit, and the output end of the PFC standby power consumption circuit is connected to the FB pin of the PFC control chip to provide a voltage higher than 2.5V to the FB pin of the PFC control chip when standby is required, so that the internal error amplifier of the PFC control chip outputs a low level, and the internal PWM control output of the PFC control chip is turned off.

[0023] It should be noted that, generally speaking, there is an energy storage inductor inside the PFC circuit. By controlling the charging and discharging of the inductor, the input current to the load can track the changes in the input voltage, thereby improving the power factor. This is generally achieved by controlling the grounding of the inductor through a switch tube. There are many types of PFC control chips, including built-in switch tubes and external switch tubes. Regardless of the type, the control center inside the PFC control chip outputs a PWM signal to the switch tube to achieve on-off control of the switch tube, such as Figure 2 The chip U1 in the figure is a PFC control chip with a built-in switch tube. All types of PFC control chips have an FB pin, i.e., a feedback receiving pin. This pin is generally used to receive the voltage feedback signal output by the PFC. The control center inside the PFC control chip adjusts the PWM signal output to the switch tube according to the voltage feedback to control the operation of the PFC circuit.

[0024] The local circuit situation at the FB pin inside the PFC control chip can be shown as follows Figure 3As shown, the FB pin inside various types of PFC control chips is connected to the negative input terminal of the internal error amplifier of the PFC control chip. The positive input terminal of the error amplifier is provided with a 2.5V reference voltage by the inside of the PFC control chip. In this way, during the PFC voltage control process, the error is output to the internal control center based on the comparison between the feedback voltage sampling and the reference voltage, so as to obtain the voltage information output to the load, and then adjust the PWM signal output to the switch tube.

[0025] In the present embodiment, when standby is required, the PFC standby power consumption circuit provides a voltage higher than 2.5V to the FB pin of the PFC control chip, that is, higher than the 2.5V reference voltage of the error amplifier, so that the internal error amplifier of the PFC control chip outputs a low level. After the PFC internal control center receives the low level signal, its control logic will turn off the internal PWM control output, and the PFC is equivalent to not working. At the same time, the internal voltage of the system is reduced to achieve the purpose of reducing power consumption. Compared with the method of turning off the Vcc power supply of the PFC chip to shut down the PFC circuit, the timing problem caused by restarting the PFC power supply is also avoided.

[0026] In one embodiment of the present invention, the PFC standby power consumption circuit includes an MCU chip and a first diode, a switch output terminal of the MCU chip is connected to the anode of the first diode, and the cathode of the first diode is connected to the FB pin of the PFC control chip. When in standby mode, the switch output terminal of the MCU chip outputs a high level signal to the FB pin of the PFC control chip through the first diode, and when working, the switch output terminal of the MCU chip outputs a low level signal to the FB pin of the PFC control chip through the first diode.

[0027] It should be noted that the MCU chip can adopt a common low-power single-chip chip, etc. The MCU chip has a switch output terminal for outputting high and low level signals. Usually, the low level is a 0V signal, and the high level output is 3.3V or 5V according to the MCU model;

[0028] In this embodiment, Figure 2 As shown, through the first diode DD1:

[0029] When the MCU chip UM1 gives a high level of 3.3V or 5V, it is connected to the FB pin of the PFC control chip U1 through the diode DD1. Since the diode has a tube voltage drop of 0.7V, the voltage of the FB pin will be higher than 2.5V after 3.3V or 5V has a voltage drop of 0.7V. The internal error amplifier of the PFC control chip U1 outputs a low level. After the internal logic of the PFC receives the low level, the internal PWM control output is turned off. The PFC is equivalent to not working, and the internal voltage of the system is reduced to achieve the purpose of reducing power consumption.

[0030] When the MCU chip UM1 gives a low level, the presence of the diode DD1 prevents the noise signal from flowing from the MCU chip UM1 to the FB pin of the PFC control chip U1. In the closed-loop control process of the PFC voltage feedback, the FB pin of the PFC control chip U1 will not be affected by external factors, the internal error amplifier will adjust and operate normally, and the PFC internal PWM will control the PFC output normally, thus ensuring the stable and accurate operation of the PFC.

[0031] In one embodiment of the present invention, the PFC circuit includes a first energy storage inductor, a second diode, a first capacitor and a voltage feedback loop, wherein a first end of the first energy storage inductor is connected to a DC power supply input, a second end is connected to a first end of the first capacitor via the second diode, a second end of the first capacitor is grounded, the second end of the first energy storage inductor is connected to a switch tube inside the PFC control chip, and grounding is controlled by the PFC control chip to implement PFC control, a detection end of the voltage feedback loop is connected to the first end of the first capacitor, and an output end is connected to an FB pin of the PFC control chip.

[0032] It should be noted that if Figure 2 As shown, the first capacitor EC1 is a large-capacity energy storage filter capacitor, and the second diode D2 is a boost diode. When working, the first energy storage inductor L1 stores energy when the internal switch tube of the PFC control chip U1 is turned on, and discharges when the internal switch tube of the PFC control chip U1 is turned off. The energy stored when it is turned on is charged to the first capacitor EC1 through the second diode D2 to achieve PFC boost, wherein the upper end voltage of the first capacitor EC1 is the output voltage to the subsequent load circuit, and the voltage feedback loop can collect the output voltage to the subsequent load circuit and feed it back to the FB pin of the PFC control chip U1 to form a feedback loop.

[0033] In one embodiment of the present invention, the voltage feedback loop includes a voltage-dividing resistor group, the voltage-dividing resistor group includes a plurality of resistors connected in series, a first end of the voltage-dividing resistor group is connected to a first end of the first capacitor, a second end is grounded, and a voltage-dividing node of the voltage-dividing resistor group is connected to the FB pin of the PFC control chip.

[0034] It should be noted that if Figure 2As shown, the voltage-dividing resistor group includes resistors R1, R2, R3, R4 and R7 connected in series, wherein the resistors R1, R2, R3 and R4 are connected in series to form an upper voltage-dividing resistor, and the resistor R7 forms a lower voltage-dividing resistor. The connection point of the upper and lower voltage-dividing resistors is the voltage-dividing node of the voltage-dividing resistor group. The upper end of the upper voltage-dividing resistor is connected to the upper end of the first capacitor EC1, and the lower end of the lower voltage-dividing resistor is grounded, so as to realize sampling of the terminal voltage of the first capacitor EC1, that is, the output voltage of the subsequent load circuit. The sampled voltage is fed back to the FB pin of the PFC control chip U1, so that the PFC control chip U1 can adjust the output PWM signal accordingly, control the energy storage or release of the first energy storage inductor L1, and realize PFC boost regulation.

[0035] In one embodiment of the present invention, the PFC circuit further includes a third diode, an anode of the third diode is connected to the first end of the first energy storage inductor, and a cathode is connected to the cathode of the second diode, and the third diode plays a role of shunt protection.

[0036] It should be noted that if Figure 2 As shown, the third diode D1 is a parallel protection shunt diode, which is used to protect the boost diode and reduce the impact of surge current on the first energy storage inductor L1 and the second diode D2; at the same time, the third diode D1 can also be a switch tube inside the PFC control chip U1. At the moment of power on, due to the need to charge the large-capacity energy storage filter capacitor, namely the first capacitor EC1, the current passing through the first energy storage inductor L1 is relatively large. If the moment the power switch is turned on is when the sine wave is at its maximum value, the first energy storage inductor L1 may be magnetically saturated during the charging process of the first capacitor EC1. In the case of magnetic saturation, the current flowing through the PFC The current of the switch tube inside the control chip U1 will be too high and burn out the switch tube. By connecting the third diode D1 in parallel with the first energy storage inductor L1 and the second diode D2 as a bypass, another branch is provided for the charging circuit of the first capacitor EC1 at the moment of startup to prevent large current from flowing through the first energy storage inductor L1 to cause saturation and overcurrent damage to the switch tube inside the PFC control chip U1; in addition, the addition of the third diode D1 speeds up the charging process of the large capacitor. The voltage on it is established in time, and the voltage feedback loop of the PFC circuit can also work in time, reducing the conduction time of the PFC switch tube when starting up, so that the PFC circuit can work normally as soon as possible.

[0037] In one embodiment of the present invention, the PFC circuit further includes a second capacitor, a first end of the second capacitor is connected to the first end of the first energy storage inductor, and a second end of the second capacitor is connected to the cathode of the second diode.

[0038] It should be noted that the second capacitor C1 is connected in parallel with the first energy storage inductor L1 to improve the output waveform.

[0039] In one embodiment of the present invention, a pre-protection rectifier module is further included, wherein the input end of the pre-protection rectifier module is connected to the external AC mains, and the output end is connected to the input end of the PFC circuit, so as to provide a DC input to the PFC circuit.

[0040] It should be noted that the pre-protection rectifier module is used to protect and filter the AC input power and convert it into a DC power.

[0041] In one embodiment of the present invention, the pre-protection rectifier module includes a protection circuit, an EMC filter circuit and a rectifier bridge circuit, the input end of the protection circuit is connected to the AC mains input port for input overcurrent and overvoltage protection, the input end of the EMC filter circuit is connected to the output end of the protection circuit for reducing electromagnetic interference, the input end of the rectifier bridge circuit is connected to the output end of the EMC filter circuit, and the output end is connected to the input end of the PFC circuit for converting the AC power input to provide a DC power supply for the PFC circuit.

[0042] It should be noted that if Figure 2 As shown, in the protection circuit, the fuse F1 is connected in series with the varistor MOV1 and is arranged between the live wire and the neutral wire port of the AC incoming line. The fuse F1 can be blown when the AC power supply is overcurrent to provide protection. The varistor is used for overvoltage protection. The bypass resistor RS is connected to the live wire port through the fuse F1 and is the current sensing resistor of the AC incoming line; the EMC filter circuit adopts a combination of common-mode inductor LF1 and capacitor CX1 to reduce electromagnetic interference. The two input ends of the common-mode inductor LF1 are respectively connected to the AC incoming line, and the two output ends are respectively connected to the rectifier bridge circuit. The capacitor CX1 is connected in parallel between the two input ends of the common-mode inductor LF1; the rectifier bridge circuit is composed of four diodes to form a rectifier bridge, which converts the AC power input into a DC power supply.

[0043] In one embodiment of the present invention, the pre-protection rectifier module further includes a third capacitor, and the third capacitor is connected in parallel between two output ends of the rectifier bridge circuit.

[0044] It should be noted that if Figure 2 As shown, the third capacitor CBB1 is a high-frequency bypass filter capacitor, which is used to ensure the stability of the DC power supply to the subsequent PFC control circuit.

[0045] Although the disclosure is disclosed as above, the protection scope of the disclosure is not limited thereto. Those skilled in the art may make various changes and modifications without departing from the spirit and scope of the disclosure, and these changes and modifications will fall within the protection scope of the present invention.

Claims

1. A circuit for reducing the standby power consumption of a PFC circuit, characterized in that: include: A PFC control chip, a PFC circuit, a load circuit and a PFC standby power consumption circuit, wherein the input end of the PFC circuit is connected to a DC power supply input, and the output end supplies power to an LED load through a load circuit to improve the overall power factor, the PFC control chip is connected to the PFC circuit to control the working state of the PFC circuit, and the output end of the PFC standby power consumption circuit is connected to the FB pin of the PFC control chip to provide a voltage higher than 2.5V to the FB pin of the PFC control chip when standby is required, so that the internal error amplifier of the PFC control chip outputs a low level, and the internal PWM control output of the PFC control chip is turned off; The PFC standby power consumption circuit includes an MCU chip and a first diode, a switch output end of the MCU chip is connected to the anode of the first diode, and a cathode of the first diode is connected to the FB pin of the PFC control chip. When in standby mode, the switch output end of the MCU chip outputs a high-level signal to the FB pin of the PFC control chip through the first diode, and when in operation, the switch output end of the MCU chip outputs a low-level signal to the FB pin of the PFC control chip through the first diode.

2. The circuit for reducing the standby power consumption of a PFC circuit according to claim 1, characterized in that: The PFC circuit includes a first energy storage inductor, a second diode, a first capacitor and a voltage feedback loop, wherein a first end of the first energy storage inductor is connected to a DC power supply input, a second end is connected to a first end of the first capacitor via the second diode, a second end of the first capacitor is grounded, the second end of the first energy storage inductor is connected to a switch tube inside the PFC control chip, and grounding is controlled by the PFC control chip to implement PFC control, a detection end of the voltage feedback loop is connected to a first end of the first capacitor, and an output end is connected to an FB pin of the PFC control chip.

3. The circuit for reducing the standby power consumption of a PFC circuit according to claim 2, characterized in that: The voltage feedback loop includes a voltage-dividing resistor group, which includes a plurality of resistors connected in series, a first end of the voltage-dividing resistor group is connected to a first end of the first capacitor, a second end is grounded, and a voltage-dividing node of the voltage-dividing resistor group is connected to an FB pin of the PFC control chip.

4. The circuit for reducing the standby power consumption of a PFC circuit according to claim 3, characterized in that: The PFC circuit also includes a third diode, an anode of the third diode is connected to the first end of the first energy storage inductor, and a cathode is connected to the cathode of the second diode, and the third diode plays a role of shunt protection.

5. The circuit for reducing the standby power consumption of a PFC circuit according to claim 4, characterized in that: The PFC circuit further includes a second capacitor, a first end of the second capacitor is connected to the first end of the first energy storage inductor, and a second end of the second capacitor is connected to the cathode of the second diode.

6. The circuit for reducing the standby power consumption of a PFC circuit according to claim 1, characterized in that: It also includes a pre-protection rectifier module, the input end of which is connected to the external AC mains, and the output end is connected to the input end of the PFC circuit, so as to provide a DC input to the PFC circuit.

7. The circuit for reducing the standby power consumption of a PFC circuit according to claim 6, characterized in that: The pre-protection rectifier module includes a protection circuit, an EMC filter circuit and a rectifier bridge circuit. The input end of the protection circuit is connected to the AC mains input port for input overcurrent and overvoltage protection. The input end of the EMC filter circuit is connected to the output end of the protection circuit for reducing electromagnetic interference. The input end of the rectifier bridge circuit is connected to the output end of the EMC filter circuit, and the output end is connected to the input end of the PFC circuit for converting the AC power input to provide a DC power supply for the PFC circuit.

8. The circuit for reducing the standby power consumption of a PFC circuit according to claim 7, characterized in that: The pre-protection rectifier module also includes a third capacitor, which is connected in parallel between the two output ends of the rectifier bridge circuit.

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