Flyback switching power supply input voltage detection circuit

Abstract

The application discloses a flyback switching power supply input voltage detection circuit, which comprises a voltage sampling module, the positive electrode of a diode D2 is connected to the input end of the voltage sampling module, the output end of the voltage sampling module is connected to the input end of an integration module, the drain electrode of a power tube M1 is connected to a transformer primary winding inductance L P , the gate electrode of the power tube M1 is connected to a controller, the output end of the integration module is connected to the input end of a power-on detection module and the input end of a power-off detection module, the output end of the power-on detection module and the output end of the power-off detection module are connected to the input end of a voltage judgment module, and the output end of the voltage judgment module is connected to the controller. The flyback switching power supply input voltage detection circuit converts high-voltage input voltage into low-voltage internal integration voltage when the transformer primary power tube is turned on, realizes the detection and judgment of fast and accurate input voltage every cycle, and samples the output voltage when the transformer primary power tube is turned off, thereby reducing the overall cost and power consumption.

Description

Technical Field

[0001] This invention belongs to the field of power supply detection circuit technology, and relates to a flyback switching power supply input voltage detection circuit. Background Technology

[0002] In recent years, due to the increasing global demand for switching power supplies, flyback switching power supplies have seen rapid development and application in the small and medium power switching power supply sector due to their advantages of low cost, simple structure, high conversion efficiency, low standby power loss, and input-output isolation. Conversion efficiency is one of the most important performance indicators of a switching power supply, closely related to input voltage and current, as well as output voltage and current. Various electronic devices and systems require a certain input voltage to function properly. However, since the power supply to the system is not continuously stable, a drop in input voltage to a certain value can cause system problems and even affect output stability. For the purpose of regulating the output voltage and protecting the circuit system, flyback switching power supplies typically detect the input voltage to check for undervoltage or overvoltage that could affect the output voltage and the circuit system. Since the input voltage is usually very high, direct detection of the input voltage requires high-voltage devices and corresponding protection circuits, increasing the overall circuit cost and power consumption. Indirect detection of the input voltage usually requires additional isolation devices and detection ports, and the detection circuit is complex, costly, and consumes more power.

[0003] In summary, existing technologies suffer from problems such as complex input voltage detection circuits and high power consumption in flyback switching power supplies. Summary of the Invention

[0004] The purpose of this invention is to provide a flyback switching power supply input voltage detection circuit, which solves the problems of complexity and high power consumption in existing flyback switching power supply input voltage detection circuits.

[0005] The technical solution adopted in this invention is a flyback switching power supply input voltage detection circuit, including a voltage sampling module, the input terminal of which is connected to the positive terminal of diode D2, the output terminal of which is connected to the input terminal of an integration module, and a power transistor M1, the drain of which is connected to the primary winding inductance L of a transformer. P The gate of power transistor M1 is connected to the controller, and the source of power transistor M1 is grounded. The output of the integration module is connected to the input of the power-on detection module and the input of the power-off detection module. The output of the power-on detection module and the output of the power-off detection module are connected to the input of the voltage judgment module. The output of the voltage judgment module is connected to the controller.

[0006] The invention is further characterized by:

[0007] The voltage sampling module includes an auxiliary winding inductor LA Auxiliary winding inductance L A One end is grounded, and the other end is connected to one end of resistor R1. The other end of resistor R1 is connected to one end of resistor R2 and one end of capacitor C3. The other ends of resistor R2 and capacitor C3 are grounded. The positive terminal of diode D2 is connected to the auxiliary winding inductance L. A Connect the ungrounded end, and connect the ungrounded end of the integrating module and resistor R2.

[0008] The integration module includes MOSFETs M2 and M3. The sources of MOSFETs M2 and M3 are connected to the power supply. The gates and drains of MOSFETs M2 and M3 are interconnected. The drain of MOSFET M2 is connected to the source of MOSFET M4. The drain of MOSFET M3 is connected to the source of MOSFET M5. The gates and drains of MOSFETs M4 and M5 are interconnected. The drain of MOSFET M4 is connected to the drain of MOSFET M6. The gate of MOSFET M6 is connected to the drive voltage V. GATE The source of MOSFET M6 is connected to the drain of MOSFET M8, and the gate of MOSFET M8 is connected to current source I. REF One end of the circuit connects to the drain and gate of MOSFET M7, while the source of MOSFET M7 is grounded. The source of MOSFET M8 and one end of resistor R2 are not grounded. One end of capacitor C4 is connected to the drain of MOSFET M9, and the other end of capacitor C4 and the source of MOSFET M9 are grounded. The gate of MOSFET M9 is connected to the output of inverter INV1. The input of inverter INV1 is connected to the drive voltage V. GATE Connect the ungrounded end of capacitor C4 to the input terminal of the power-on detection module and the input terminal of the power-off detection module.

[0009] The power-on detection module includes comparator A1. The non-inverting input of comparator A1 is connected to the ungrounded end of capacitor C4, and the inverting input of comparator A1 is connected to the power-on detection threshold voltage V. th_in The output of comparator A1 is connected to a first timer, which is connected to a voltage judgment module.

[0010] The power failure detection module includes comparator A2. The inverting input of comparator A2 is connected to the ungrounded end of capacitor C4, and the non-inverting input of comparator A2 is connected to the power failure detection threshold voltage V. th_out The output of comparator A2 is connected to a second timer, which is connected to the voltage judgment module.

[0011] The voltage judgment module includes an RS flip-flop, the set terminal of the RS flip-flop is connected to the first timer, the reset terminal of the RS flip-flop is connected to the second timer, and the output terminal of the RS flip-flop is connected to the controller.

[0012] The beneficial effects of this invention are as follows: The flyback switching power supply input voltage detection circuit converts the high-voltage input voltage into a low-voltage internal integrated voltage when the power transistor on the primary side of the transformer is turned on, thus eliminating the need for high-voltage devices. It also judges whether the input voltage is powered on normally and whether a power failure has occurred, enabling rapid and accurate detection and judgment of the input voltage per cycle. At the same time, the voltage sampling module can also sample the output voltage when the power transistor on the primary side of the transformer is turned off, making one port dual-purpose and eliminating the need for a dedicated input voltage detection port, thereby reducing overall cost and power consumption. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the input voltage detection circuit for the flyback switching power supply of the present invention.

[0014] In the diagram, 1 is the voltage sampling module; 2 is the integration module; 3 is the power-on detection module; 4 is the power-off detection module; 5 is the voltage judgment module; 6 is the controller; 7 is the first timer; and 8 is the second timer. Detailed Implementation

[0015] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0016] Flyback switching power supply input voltage detection circuit, such as Figure 1 As shown, the flyback switching power supply input voltage detection circuit includes a voltage sampling module 1, whose input terminal is connected to the positive terminal of diode D2, and whose output terminal is connected to the input terminal of integration module 2. It also includes a power transistor M1, whose drain is connected to the primary winding inductance L of a transformer. P The gate of power transistor M1 is connected to controller 6, and the source of power transistor M1 is grounded. The output of integration module 2 is connected to the input of power-on detection module 3 and power-off detection module 4. The output of power-on detection module 3 and power-off detection module 4 are connected to the input of voltage judgment module 5. The output of voltage judgment module 5 is connected to controller 6.

[0017] Voltage sampling module 1 includes auxiliary winding inductor L A Auxiliary winding inductance L A One end is grounded, and the other end is connected to one end of resistor R1. The other end of resistor R1 is connected to one end of resistor R2 and one end of capacitor C3. The other ends of resistor R2 and capacitor C3 are grounded. The positive terminal of diode D2 is connected to the auxiliary winding inductance L. A Connect the ungrounded end to the integrator module 2 and the ungrounded end to the resistor R2.

[0018] Integration module 2 includes MOSFETs M2 and M3. The sources of MOSFETs M2 and M3 are connected to a power supply. The gates and drains of MOSFETs M2 and M3 are interconnected. The drain of MOSFET M2 is connected to the source of MOSFET M4. The drain of MOSFET M3 is connected to the source of MOSFET M5. The gates and drains of MOSFETs M4 and M5 are interconnected. The drain of MOSFET M4 is connected to the drain of MOSFET M6. The gate of MOSFET M6 is connected to a driving voltage V. GATE The source of MOSFET M6 is connected to the drain of MOSFET M8, and the gate of MOSFET M8 is connected to current source I. REF One end of the circuit connects to the drain and gate of MOSFET M7, while the source of MOSFET M7 is grounded. The source of MOSFET M8 and one end of resistor R2 are not grounded. One end of capacitor C4 is connected to the drain of MOSFET M9, and the other end of capacitor C4 and the source of MOSFET M9 are grounded. The gate of MOSFET M9 is connected to the output of inverter INV1. The input of inverter INV1 is connected to the drive voltage V. GATE Connect the ungrounded end of capacitor C4 to the input terminal of power-on detection module 3 and the input terminal of power-off detection module 4.

[0019] The power-on detection module 3 includes a comparator A1. The non-inverting input of comparator A1 is connected to the ungrounded end of capacitor C4, and the inverting input of comparator A1 is connected to the power-on detection threshold voltage V. th_in The output of comparator A1 is connected to the first timer 7, and the first timer 7 is connected to the voltage judgment module 5.

[0020] The power failure detection module 4 includes a comparator A2. The inverting input of comparator A2 is connected to the ungrounded end of capacitor C4, and the non-inverting input of comparator A2 is connected to the power failure detection threshold voltage V. th_out The output of comparator A2 is connected to a second timer 8, which is connected to the voltage judgment module 5.

[0021] The voltage judgment module 5 includes an RS flip-flop, the set terminal of the RS flip-flop is connected to the first timer 7, the reset terminal of the RS flip-flop is connected to the second timer 8, and the output terminal of the RS flip-flop is connected to the controller 6.

[0022] Voltage sampling module 1 is used to sample the input voltage signal every cycle. When power transistor M1 is turned on, the input voltage signal passes through the transformer primary winding inductance L. P Coupled to auxiliary winding inductor L A The voltage across the two ends is divided by resistors R1 and R2 to obtain a sampling voltage V that is proportional to the input voltage. VS The relationship is as follows:

[0023]

[0024] Among them, V DC N is the DC input voltage signal after the AC input voltage is rectified by the rectifier bridge. P N represents the number of turns in the primary winding of the transformer. A This refers to the number of turns in the auxiliary winding of the transformer.

[0025] Integrator module 2 is used to integrate the sampled voltage V VS The signal is converted into a current signal and then integrated. MOSFETs M7 and M8 form a current mirror structure to convert the fixed current I... REF The source and drain currents of MOSFET M8 are replicated proportionally to the gate voltage V of power transistor M1. GATE When the voltage is high, power transistor M1 is on, MOSFET M6 is on, and MOSFET M9 is off. At this time, the current flowing through MOSFETs M2 and M4 is the same as the source-drain current of MOSFET M8, which is consistent with the sampling voltage V. VS The relevant current I1 is then replicated proportionally into the source-drain current I2 of MOSFETs M3 and M5 through a current mirror structure composed of MOSFETs M2, M3, M4, and M5. At this point, the current I2 is related to the sampling voltage V. VS Relatedly, the current I2 is then integrated across capacitor C4 to obtain the result related to the sampled voltage V. VS The relevant integral voltage V ON Current I1 and sampling voltage V VS The relationship is:

[0026]

[0027] Among them, K P For transconductance, The aspect ratio of M7, For the aspect ratio of M8, V TH8 This is the threshold voltage of M8.

[0028] Current I2 and sampling voltage V VS The relationship is:

[0029]

[0030] Among them, K P For transconductance, The aspect ratio of M2 is... The aspect ratio of M7, The aspect ratio of M8.

[0031] Integral voltage V ON The relationship with current I2 is as follows:

[0032] The gate voltage V of power transistor M1 GATE When the voltage is low, power transistor M1 is off, MOSFET M6 is off, and MOSFET M9 is on. The integration module releases the charge integrated on capacitor C4 during the current cycle when power transistor M1 is on through MOSFET M9, and no input voltage detection is performed at this time.

[0033] Power-on detection module 3 is used to determine whether the input voltage has been successfully powered on. If the integrating voltage V of integrating module 2... ON Voltage greater than the power-on detection threshold V th_in Start the first timer 7, and when it is detected that the integral voltage V is continuously satisfied within the time t1 set by the first timer 7, ON Voltage greater than the power-on detection threshold V th_in If the input voltage is successfully powered on, it is determined that the power-on is successful; if the integrating voltage V of integrating module 2 is... ON Voltage greater than the power-on detection threshold V th_in However, it was not continuously satisfied within the time t1 set by the first timer 7, or the integration voltage V of the integration module 2 was not met. ON Less than the power-on detection threshold voltage V th_in If so, it can be determined that the input voltage has not been successfully applied.

[0034] Power failure detection module 4 is used to determine whether a power failure has occurred in the input voltage. If the integrating voltage V of integrating module 2... ON Voltage less than the power failure detection threshold V th_out Start the second timer 8, and when it is detected that the integral voltage V is continuously satisfied within the time t2 set by the second timer 8, ON Voltage less than the power failure detection threshold V th_out If the input voltage drops, it is determined that a power failure has occurred; if the integrating voltage V of integrating module 2... ON Voltage less than the power failure detection threshold V th_ou However, it was not continuously satisfied within the time t2 set by the second timer 8, or the integration voltage V of the integration module 2 was not met. ON Voltage greater than the power failure detection threshold V th_out If so, it can be determined that the input voltage has not been lost.

[0035] The voltage judgment module 5 is used to determine whether the input voltage has been successfully powered on or has been lost, and outputs a total input voltage judgment signal to the controller 6.

[0036] The flyback switching power supply input voltage detection circuit, based on the operating mode of the flyback switching power supply, converts the high-voltage input voltage into a low-voltage internal integrated voltage when the power transistor on the primary side of the transformer is turned on. It simultaneously performs power-on and power-off detection, and logically judges the output signals of both, ultimately outputting a total input voltage judgment signal to controller 6. When the input voltage is normal under power-on conditions, controller 6 controls the system to operate normally; when the input voltage is lost, controller 6 shuts down the system. Regardless of the situation, a judgment signal is output to controller 6, enabling rapid and accurate detection and judgment of the input voltage per cycle.

[0037] Example 1

[0038] like Figure 1 As shown, this embodiment proposes a flyback switching power supply input voltage detection circuit, including a voltage sampling module 1. The input terminal of the voltage sampling module 1 is connected to the positive terminal of diode D2, and the output terminal of the voltage sampling module 1 is connected to the input terminal of the integration module 2. It also includes a power transistor M1, the drain of which is connected to the primary winding inductance L of a transformer. P The gate of power transistor M1 is connected to controller 6, and the source of power transistor M1 is grounded. The output of integration module 2 is connected to the input of power-on detection module 3 and power-off detection module 4. The outputs of power-on detection module 3 and power-off detection module 4 are connected to the input of voltage judgment module 5, and the output of voltage judgment module 5 is connected to controller 6. Voltage sampling module 1 includes auxiliary winding inductor L. A Auxiliary winding inductance L A One end is grounded, and the other end is connected to one end of resistor R1. The other end of resistor R1 is connected to one end of resistor R2 and one end of capacitor C3. The other ends of resistor R2 and capacitor C3 are grounded. The positive terminal of diode D2 is connected to the auxiliary winding inductance L. A Connect the ungrounded end to the integrator module 2 and the ungrounded end to the resistor R2.

[0039] Example 2

[0040] like Figure 1 As shown, this embodiment proposes a flyback switching power supply input voltage detection circuit, including a voltage sampling module 1. The input terminal of the voltage sampling module 1 is connected to the positive terminal of diode D2, and the output terminal of the voltage sampling module 1 is connected to the input terminal of the integration module 2. It also includes a power transistor M1, the drain of which is connected to the primary winding inductance L of a transformer. PThe gate of power transistor M1 is connected to controller 6, and the source of power transistor M1 is grounded. The output of integration module 2 is connected to the input of power-on detection module 3 and power-off detection module 4. The outputs of power-on detection module 3 and power-off detection module 4 are connected to the input of voltage judgment module 5, and the output of voltage judgment module 5 is connected to controller 6. Voltage sampling module 1 includes auxiliary winding inductor L. A Auxiliary winding inductance L A One end is grounded, and the other end is connected to one end of resistor R1. The other end of resistor R1 is connected to one end of resistor R2 and one end of capacitor C3. The other ends of resistor R2 and capacitor C3 are grounded. The positive terminal of diode D2 is connected to the auxiliary winding inductance L. A The ungrounded end of the integrator module 2 is connected to the ungrounded end of the resistor R2. Integrator module 2 includes MOSFETs M2 and M3. The sources of MOSFETs M2 and M3 are connected to the power supply. The gates and drains of MOSFETs M2 and M3 are interconnected. The drain of MOSFET M2 is connected to the source of MOSFET M4. The drain of MOSFET M3 is connected to the source of MOSFET M5. The gates and drains of MOSFETs M4 and M5 are interconnected. The drain of MOSFET M4 is connected to the drain of MOSFET M6. The gate of MOSFET M6 is connected to the drive voltage V. GATE The source of MOSFET M6 is connected to the drain of MOSFET M8, and the gate of MOSFET M8 is connected to current source I. REF One end of the circuit connects to the drain and gate of MOSFET M7, while the source of MOSFET M7 is grounded. The source of MOSFET M8 and one end of resistor R2 are not grounded. One end of capacitor C4 is connected to the drain of MOSFET M9, and the other end of capacitor C4 and the source of MOSFET M9 are grounded. The gate of MOSFET M9 is connected to the output of inverter INV1. The input of inverter INV1 is connected to the drive voltage V. GATE Connect the ungrounded end of capacitor C4 to the input terminal of power-on detection module 3 and the input terminal of power-off detection module 4.

[0041] Example 3

[0042] like Figure 1 As shown, this embodiment proposes a flyback switching power supply input voltage detection circuit, including a voltage sampling module 1. The input terminal of the voltage sampling module 1 is connected to the positive terminal of diode D2, and the output terminal of the voltage sampling module 1 is connected to the input terminal of the integration module 2. It also includes a power transistor M1, the drain of which is connected to the primary winding inductance L of a transformer. PThe gate of power transistor M1 is connected to controller 6, and the source of power transistor M1 is grounded. The output of integration module 2 is connected to the input of power-on detection module 3 and power-off detection module 4. The output of power-on detection module 3 and power-off detection module 4 are connected to the input of voltage judgment module 5. The output of voltage judgment module 5 is connected to controller 6.

[0043] Voltage sampling module 1 includes auxiliary winding inductor L A Auxiliary winding inductance L A One end is grounded, and the other end is connected to one end of resistor R1. The other end of resistor R1 is connected to one end of resistor R2 and one end of capacitor C3. The other ends of resistor R2 and capacitor C3 are grounded. The positive terminal of diode D2 is connected to the auxiliary winding inductance L. A The ungrounded end of the integrator module 2 is connected to the ungrounded end of the resistor R2. Integrator module 2 includes MOSFETs M2 and M3. The sources of MOSFETs M2 and M3 are connected to the power supply. The gates and drains of MOSFETs M2 and M3 are interconnected. The drain of MOSFET M2 is connected to the source of MOSFET M4. The drain of MOSFET M3 is connected to the source of MOSFET M5. The gates and drains of MOSFETs M4 and M5 are interconnected. The drain of MOSFET M4 is connected to the drain of MOSFET M6. The gate of MOSFET M6 is connected to the drive voltage V. GATE The source of MOSFET M6 is connected to the drain of MOSFET M8, and the gate of MOSFET M8 is connected to current source I. REF One end of the circuit connects to the drain and gate of MOSFET M7, while the source of MOSFET M7 is grounded. The source of MOSFET M8 and one end of resistor R2 are not grounded. One end of capacitor C4 is connected to the drain of MOSFET M9, and the other end of capacitor C4 and the source of MOSFET M9 are grounded. The gate of MOSFET M9 is connected to the output of inverter INV1. The input of inverter INV1 is connected to the drive voltage V. GATE Connect the ungrounded end of capacitor C4 to the input terminal of power-on detection module 3 and the input terminal of power-off detection module 4.

[0044] The power-on detection module 3 includes a comparator A1. The non-inverting input of comparator A1 is connected to the ungrounded end of capacitor C4, and the inverting input of comparator A1 is connected to the power-on detection threshold voltage V. th_in The output of comparator A1 is connected to a first timer 7, which is connected to the voltage judgment module 5. The power-down detection module 4 includes comparator A2. The inverting input of comparator A2 is connected to the ungrounded end of capacitor C4, and the non-inverting input of comparator A2 is connected to the power-down detection threshold voltage V. th_outThe output of comparator A2 is connected to a second timer 8, which is connected to a voltage judgment module 5. The voltage judgment module 5 includes an RS flip-flop, the set terminal of which is connected to a first timer 7, the reset terminal of which is connected to the second timer 8, and the output of which is connected to a controller 6.

Claims

1. A flyback switching power supply input voltage detection circuit, characterized by, The application relates to a power-on / off detection circuit, which comprises a voltage sampling module (1), the positive pole of a diode D2 being connected to the input end of the voltage sampling module (1), the output end of the voltage sampling module (1) being connected to the input end of an integration module (2), a power tube M1, the drain of the power tube M1 being connected to a transformer primary winding inductor L P , the gate of the power tube M1 being connected to a controller (6), the source of the power tube M1 being grounded, the output end of the integration module (2) being connected to the input end of a power-on detection module (3) and the input end of a power-off detection module (4), the output end of the power-on detection module (3) and the output end of the power-off detection module (4) being connected to the input end of a voltage judgment module (5), and the output end of the voltage judgment module (5) being connected to the controller (6). The voltage sampling module (1) comprises an auxiliary winding inductance L A , one end of which is grounded, and the other end is connected with one end of a resistor R1 A , one end of a resistor R2 and one end of a capacitor C3, the other end of the resistor R2 and the other end of the capacitor C3 are grounded, the positive electrode of a diode D2 is connected with one end of the auxiliary winding inductance L A which is not grounded, and the integral module (2) and the other end of the resistor R2 are connected with the auxiliary winding inductance L which is not grounded. The integral module (2) comprises MOS tube M2 and MOS tube M3, the source of the MOS tube M2 and the source of the MOS tube M3 are connected to the power supply, the gate of the MOS tube M2, the drain of the MOS tube M2 and the gate of the MOS tube M3 are connected to each other, the drain of the MOS tube M2 is connected to the source of the MOS tube M4, the drain of the MOS tube M3 is connected to the source of the MOS tube M5, the gate of the MOS tube M4, the drain of the MOS tube M4 and the gate of the MOS tube M5 are connected to each other; the drain of the MOS tube M4 is connected to the drain of the MOS tube M6, the gate of the MOS tube M6 is connected to the driving voltage V GATE , the source of the MOS tube M6 is connected to the drain of the MOS tube M8, the gate of the MOS tube M8 is connected to the current source I REF one end, the drain of the MOS tube M7 and the gate of the MOS tube M7, the source of the MOS tube M7 is grounded, the source of the MOS tube M8 and one end of the resistor R2 are not connected to the ground; the drain of the MOS tube M5 is connected to one end of the capacitor C4, the drain of the MOS tube M9, the other end of the capacitor C4 and the source of the MOS tube M9 are grounded, the gate of the MOS tube M9 is connected to the output end of the inverter INV1, the input end of the inverter INV1 is connected to the driving voltage V GATE , one end of the capacitor C4 is connected to the input end of the power-on detection module (3) and the input end of the power-off detection module (4).

2. The flyback switching power supply input voltage detection circuit according to claim 1, characterized by The power-on detection module (3) comprises a comparator A1, the same phase input end of the comparator A1 is connected with the non-ground end of a capacitor C4, the opposite phase input end of the comparator A1 is connected with a power-on detection threshold voltage V th_in , the output end of the comparator A1 is connected with a first timer (7), and the first timer (7) is connected with a voltage judgment module (5).

3. The flyback switching power supply input voltage detection circuit according to claim 2, characterized in that, The power-down detection module (4) comprises a comparator A2, the inverting input end of the comparator A2 is connected with the non-ground end of a capacitor C4, the non-inverting input end of the comparator A2 is connected with a power-down detection threshold voltage V th_out , the output end of the comparator A2 is connected with a second timer (8), and the second timer (8) is connected with the voltage judging module (5).

4. The flyback switching power supply input voltage detection circuit according to claim 3, characterized by The voltage judging module (5) comprises an RS flip-flop, the setting end of the RS flip-flop is connected with a first timer (7), the resetting end of the RS flip-flop is connected with a second timer (8), and the output end of the RS flip-flop is connected with a controller (6).

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