Flyback ACDC switching power supply circuit

Abstract

The utility model provides a flyback ACDC switching power supply circuit. The flyback ACDC switching power supply circuit comprises a transformer, an MOS tube and a control module, one end of an output voltage detection circuit of the control module is connected with bus voltage, the other end is directly connected with the second end of the primary winding of the transformer, output voltage can be obtained according to the bus voltage and the second end voltage of the primary winding, an auxiliary winding does not need to be arranged, independent output wire drawing is not needed, and circuit complexity and cost are reduced. And more compact power supply design can be realized, the circuit is suitable for application scenes with limited space, and fault risks caused by loosening, damage and the like of connecting wires or interfaces can be reduced at the same time.

Description

Technical Field

[0001] The present application relates to the field of AC / DC converters, and in particular to a flyback ACDC switching power supply circuit. Background Art

[0002] The flyback AC / DC switching power supply circuit is a commonly used power conversion circuit that can convert alternating current (AC) into direct current (DC) and has the advantages of high efficiency and small size.

[0003] A flyback AC / DC switching power supply circuit primarily consists of an input rectifier and filter circuit, a power switch, a high-frequency transformer, an output rectifier and filter circuit, a PWM controller, and a feedback circuit. The input rectifier and filter circuit converts the input AC power to DC and performs filtering to reduce voltage fluctuations and noise. The power switch, typically a high-speed switching device such as a MOSFET or IGBT, controls the on / off state of the circuit, achieving voltage conversion. The high-frequency transformer, a key component in energy conversion, transfers the input energy to the output and provides electrical isolation. The output rectifier and filter circuit rectifies the high-frequency pulse voltage output by the high-frequency transformer into a smooth DC voltage for supply to the load. The PWM controller generates a drive signal with a fixed frequency and adjustable pulse width, controlling the on and off times of the power switch, thereby regulating the output voltage. The feedback circuit detects the output voltage or current, compares it with the set value, and maintains a stable output voltage or current by adjusting the output pulse width of the PWM controller.

[0004] In ACDC applications, monitoring the output voltage is crucial for the system. For example, achieving constant voltage output and output voltage overvoltage protection both require output voltage detection. Typically, in schemes for detecting the output voltage of flyback AC / DC switching power supply circuits, an auxiliary winding is provided on the transformer to detect the output voltage, requiring a separate wire to be drawn from the output, increasing circuit complexity and cost. Utility Model Content

[0005] The purpose of the embodiments of the present application is to provide a flyback ACDC switching power supply circuit to solve the problem that in the prior art solution of detecting the output voltage of the flyback AC / DC switching power supply circuit, an auxiliary winding is set on the transformer to detect the output voltage, which requires a separate wire to be pulled from the output, increasing the circuit complexity and cost.

[0006] The embodiment of the present application provides a flyback ACDC switching power supply circuit, including a transformer, a MOS transistor, and a control module; the control module is used to send a PWM signal to the MOS transistor, which stores energy when it is turned on and transfers energy to the output side when it is turned off;

[0007] The control module includes an output voltage detection circuit, a first end of the output voltage detection circuit is connected to the bus voltage, and a second end of the output voltage detection circuit is connected to the second end of the primary winding of the transformer. The output voltage detection circuit is used to obtain the output voltage based on the bus voltage and the voltage at the second end of the primary winding.

[0008] In the above technical solution, the flyback ACDC switching power supply circuit includes a transformer, a MOS tube and a control module; one end of the output voltage detection circuit of the control module is connected to the bus voltage, and the other end is directly connected to the second end of the primary winding of the transformer. The output voltage can be obtained according to the bus voltage and the voltage of the second end of the primary winding. There is no need to set up an auxiliary winding, and there is no need to pull a wire separately from the output, which reduces the circuit complexity and cost, and helps to achieve a more compact power supply design, which is suitable for application scenarios with limited space. At the same time, it reduces the risk of failure caused by loose or damaged connecting wires or interfaces.

[0009] In some optional implementations, the output voltage detection circuit includes: a first voltage-to-current module, a second voltage-to-current module, and a current difference module;

[0010] The first voltage-to-current module is used to convert the bus voltage into a first current and output the first current to the first end of the current difference module; the second voltage-to-current module is used to convert the voltage at the second end of the primary winding into a second current and output the second current to the second end of the current difference module; the current difference module outputs a third current to the first end of the sampling resistor, and the second end of the sampling resistor is grounded; wherein the current value of the third current is the difference between the second current and the first current; and the voltage value of the output voltage is the product of the voltage at the first end of the sampling resistor and the corresponding coefficient.

[0011] In some optional embodiments, the control module further includes an error amplifier;

[0012] The control module is further configured to compare the output voltage with a reference voltage using an error amplifier to adjust the output voltage.

[0013] In the above technical solution, the error amplifier accurately measures the difference between the output voltage and the reference voltage. By adjusting the output of the control chip, it precisely controls the on-time of the switch in the flyback circuit, thereby achieving precise regulation of the output voltage. When the load changes or the bus voltage fluctuates, the error amplifier quickly responds and adjusts the output voltage, keeping it near the set value, thereby improving system stability and reliability. By precisely regulating the output voltage, the error amplifier helps the flyback circuit operate at the optimal operating point, reducing unnecessary power loss and improving overall system efficiency.

[0014] In some optional implementations, the first end of the sampling resistor is further connected to the positive input end of the error amplifier, and the negative input end of the error amplifier is used to input a reference voltage.

[0015] In some optional embodiments, the control module further includes a comparator;

[0016] The control module is further configured to: use a comparator to compare the output voltage with a set maximum voltage to perform overvoltage detection.

[0017] In the above technical solution, the comparator's real-time monitoring function allows the system to quickly respond to changes in output voltage and take immediate protective measures if an overvoltage condition occurs. This rapid response capability improves the system's reliability and stability.

[0018] In some optional implementations, the second end of the sampling resistor is grounded, the first end of the sampling resistor is further connected to the positive input end of the comparator, and the negative input end of the comparator is used to input a set maximum voltage.

[0019] In some optional implementations, the sampling resistor is a built-in resistor of the control module, and the sampling resistor, the resistor in the first voltage-to-current module, and the resistor in the second voltage-to-current module are resistors of the same type.

[0020] In the above technical solution, the sampling resistor is a resistor built into the control module, and the sampling resistor, the resistor in the first voltage-to-current module, and the resistor in the second voltage-to-current module are resistors of the same type, so that the temperature coefficient can be offset, and the final voltage obtained is a voltage with zero temperature coefficient.

[0021] In some optional implementations, the sampling resistor is an external resistor of the control module, and the sampling resistor is a zero temperature coefficient resistor; the output voltage detection circuit further includes: a ZTC module;

[0022] The ZTC module is used to convert the third current into a fourth current with a zero temperature coefficient in both the first voltage-to-current module and the second voltage-to-current module, and output the fourth current to the first end of the sampling resistor.

[0023] In the above technical solution, the sampling resistor is a resistor with a zero temperature coefficient, and the third current is converted into a fourth current with a zero temperature coefficient by the ZTC module, so that a voltage with a zero temperature coefficient is finally obtained.

[0024] In some optional embodiments, the device further comprises: a first diode, a second capacitor, and a fifth resistor;

[0025] The second end of the primary winding of the transformer is connected to the input end of the first diode, the output end of the first diode is connected to the second end of the second capacitor and the second end of the fifth resistor, the first end of the second capacitor is connected to the bus voltage, and the first end of the fifth resistor is connected to the bus voltage.

[0026] In some optional embodiments, the device further comprises: a second diode, a fourth capacitor, and a sixth resistor;

[0027] The first end of the secondary winding of the transformer is connected to the input end of the second diode, the output end of the second diode is connected to the first end of the fourth capacitor and the first end of the sixth resistor, the second end of the fourth capacitor is connected to the second end of the secondary winding of the transformer, and the second end of the sixth resistor is connected to the second end of the secondary winding of the transformer. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0029] Figure 1 A circuit diagram of a flyback ACDC switching power supply provided in an embodiment of the present application;

[0030] Figure 2 A schematic diagram of an output voltage detection circuit provided in the first embodiment of the present application;

[0031] Figure 3 A schematic diagram of the control module circuit structure provided in the first embodiment of the present application;

[0032] Figure 4 A schematic diagram of an output voltage detection circuit provided in the second embodiment of the present application;

[0033] Figure 5 This is a schematic diagram of the control module circuit structure provided in the second embodiment of the present application. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application.

[0035] Please refer to Figure 1 , Figure 1A structure diagram of a flyback ACDC switching power supply circuit provided in an embodiment of the present application includes a transformer, a MOS tube M1 and a control module; the control module is used to send a PWM signal to the MOS tube M1, store energy when the MOS tube M1 is turned on, and transfer energy to the output side when the MOS tube M1 is turned off; the control module includes an output voltage detection circuit, a first end of the output voltage detection circuit is connected to the bus voltage VM, and a second end of the output voltage detection circuit is connected to the second end of the primary winding of the transformer, and the output voltage detection circuit is used to obtain the output voltage based on the bus voltage VM and the voltage at the second end of the primary winding.

[0036] In an embodiment of the present application, a flyback ACDC switching power supply circuit includes a transformer, a MOS tube M1 and a control module; one end of the output voltage detection circuit of the control module is connected to the bus voltage VM, and the other end is directly connected to the second end of the primary winding of the transformer. The output voltage can be obtained according to the bus voltage VM and the voltage of the second end of the primary winding. There is no need to set up an auxiliary winding, and there is no need to pull a wire separately from the output, which reduces the circuit complexity and cost, and helps to achieve a more compact power supply design, which is suitable for application scenarios with limited space. At the same time, it reduces the risk of failure caused by loose or damaged connecting wires or interfaces.

[0037] The flyback ACDC switching power supply circuit of this embodiment further includes: a rectifier bridge, a first diode, a second capacitor, a fifth resistor, a second diode, a fourth capacitor and a sixth resistor.

[0038] The rectifier bridge rectifies the AC input voltage Vin_ac and outputs it. The positive output terminal of the rectifier bridge is connected to the first terminal of the first capacitor, and the second terminal of the first capacitor is connected to the negative output terminal of the rectifier bridge. The second terminal of the primary winding of the transformer is connected to the input terminal of the first diode, the output terminal of the first diode is connected to the second terminal of the second capacitor and the second terminal of the fifth resistor, the first terminal of the second capacitor is connected to the bus voltage VM, and the first terminal of the fifth resistor is connected to the bus voltage VM. The first terminal of the secondary winding of the transformer is connected to the input terminal of the second diode, the output terminal of the second diode is connected to the first terminal of the fourth capacitor and the first terminal of the sixth resistor, the second terminal of the fourth capacitor is connected to the second terminal of the secondary winding of the transformer, and the second terminal of the sixth resistor is connected to the second terminal of the secondary winding of the transformer.

[0039] The control module of this embodiment uses a control chip, which has an HV terminal, a ZCD terminal, a ROUT terminal, a VDD terminal, a TADJ terminal, a GND terminal, a CS terminal and a DRV terminal. The HV terminal is connected to the bus voltage VM, the ZCD terminal is connected to the second terminal of the primary winding of the transformer, the ROUT terminal is grounded through the sampling resistor ROUT, the TADJ terminal is grounded through the resistor R1, the CS terminal is connected to the first terminal of the resistor R3 through the resistor R2, and the second terminal of the resistor R3 is grounded, the VDD terminal is grounded through the capacitor C3, the GND terminal is grounded, the DRV terminal is connected to the gate of the MOS tube M1, the source of the MOS tube M1 is grounded through the resistor R3, and the drain of the MOS tube M1 is connected to the second terminal of the primary winding of the transformer.

[0040] Please refer to Figure 2 , Figure 2 This is a schematic diagram of an output voltage detection circuit provided in the first embodiment of the present application. The output voltage detection circuit includes: a first voltage-to-current module, a second voltage-to-current module, and a current difference module.

[0041] Among them, the first voltage-to-current module is used to convert the bus voltage VM into a first current and output the first current to the first end of the current difference module; the second voltage-to-current module is used to convert the voltage at the second end of the primary winding into a second current and output the second current to the second end of the current difference module; the current difference module outputs a third current to the first end of the sampling resistor ROUT, and the second end of the sampling resistor ROUT is grounded; wherein the current value of the third current is the difference between the second current and the first current; the voltage value of the output voltage is the product of the voltage at the first end of the sampling resistor ROUT and the corresponding coefficient.

[0042] In this embodiment, the sampling resistor ROUT is a built-in resistor of the control module, and the sampling resistor ROUT, the resistor in the first voltage-to-current module, and the resistor in the second voltage-to-current module are resistors of the same type.

[0043] In the embodiment of the present application, the sampling resistor ROUT is a resistor built into the control module, and the sampling resistor ROUT, the resistor in the first voltage-to-current module, and the resistor in the second voltage-to-current module are resistors of the same type, so that the temperature coefficient can be offset, and the final voltage obtained is a voltage with zero temperature coefficient.

[0044] Specifically, refer to Figure 2 The derivation process of the circuit of this embodiment to obtain the zero temperature coefficient output voltage Vo is as follows:

[0045] V1=ZCD×R12 / (R11+R12)

[0046] V2=HV×R22 / (R21+R22)

[0047] I1=V1 / R13

[0048] I2=V2 / R23

[0049] I3=I1-I2=ZCD×R12 / (R11+R12) / R13-HV×R22 / (R21+R22) / R23

[0050] VFB=I3×ROUT

[0051] VFB=ZCD×R12 / (R11+R12) / R13×ROUT-HV×R22 / (R21+R22) / R23×ROUT;

[0052] In the above formula, R13, R23, and ROUT are resistors of the same type with the same temperature coefficient. Dividing them can cancel out the temperature coefficients. Therefore, the obtained VFB is a voltage with zero temperature coefficient.

[0053] Set the resistance ratio k = R12 / (R11+R12) / R13×ROUT = R22 / (R21+R22) / R23×ROUT, then VFB = k(ZCD-HV);

[0054] Since the output voltage Vo = (ZCD-HV) / NPS, it can be deduced that ZCD-HV = Vo×NPS;

[0055] Substituting the voltage VFB into the expression, VFB = k(ZCD-HV) = k×NPS×Vo; where k and NPS are constants, VFB is proportional to Vo. By detecting VFB, the output voltage Vo can be detected.

[0056] Please refer to Figure 3 , Figure 3 This is a schematic diagram of the control module circuit structure provided in the first embodiment of the present application.

[0057] In some optional implementations, the control module further includes an error amplifier EA; the control module is further configured to: compare the output voltage with a reference voltage using the error amplifier EA to adjust the output voltage.

[0058] In the embodiments of the present application, the error amplifier EA can precisely measure the difference between the output voltage and the reference voltage and, by adjusting the output of the control chip, precisely control the on-time of the switch in the flyback circuit, thereby achieving precise regulation of the output voltage. When the load changes or the bus voltage VM fluctuates, the error amplifier EA can quickly respond and adjust the output voltage, keeping it fluctuating near the set value, thereby improving system stability and reliability. By precisely regulating the output voltage, the error amplifier EA helps the flyback circuit operate at the optimal operating point, reducing unnecessary power loss and improving overall system efficiency.

[0059] In some optional implementations, the first end of the sampling resistor ROUT is further connected to the positive input end of the error amplifier EA, and the negative input end of the error amplifier EA is used to input a reference voltage.

[0060] In some optional implementations, the control module further includes a comparator COMP; the control module is further configured to: utilize the comparator COMP to compare the output voltage with a set maximum voltage to perform overvoltage detection.

[0061] In the embodiment of the present application, the real-time monitoring function of the comparator COMP allows the system to quickly respond to changes in the output voltage and take immediate protective measures if an overvoltage condition occurs. This rapid response capability improves the reliability and stability of the system.

[0062] In some optional implementations, the second end of the sampling resistor ROUT is grounded, the first end of the sampling resistor ROUT is further connected to the positive input end of the comparator COMP, and the negative input end of the comparator COMP is used to input a set maximum voltage.

[0063] Please refer to Figure 4 , Figure 4 The output voltage detection circuit schematic diagram provided for the second embodiment of the present application differs from the first embodiment in that: the sampling resistor ROUT is an external resistor of the control module, and the sampling resistor ROUT is a zero temperature coefficient resistor; the output voltage detection circuit also includes: a ZTC module; the ZTC module is used to convert the third current into a fourth current with a zero temperature coefficient in both the first voltage-to-current module and the second voltage-to-current module, and output the fourth current to the first end of the sampling resistor ROUT.

[0064] In the embodiment of the present application, the sampling resistor ROUT is a resistor with a zero temperature coefficient, and the third current is converted into a fourth current with a zero temperature coefficient by the ZTC module, so that a voltage with a zero temperature coefficient is finally obtained.

[0065] Please refer to Figure 5 , Figure 5 A schematic diagram of the control module circuit structure provided in the second embodiment of the present application;

[0066] In some optional implementations, the control module further includes an error amplifier EA, the first end of the sampling resistor ROUT is further connected to the positive input end of the error amplifier EA, and the negative input end of the error amplifier EA is used to input a reference voltage.

[0067] The control module is also used to: use the error amplifier EA to compare the output voltage with the reference voltage to adjust the output voltage. In the embodiment of the present application, the error amplifier EA can measure the difference between the output voltage and the reference voltage with high precision, and accurately control the conduction time of the switch tube in the Flyback circuit by adjusting the output of the control chip, thereby achieving precise regulation of the output voltage. When the load changes or the bus voltage VM fluctuates, the error amplifier EA can respond quickly and adjust the output voltage to keep it fluctuating around the set value, thereby improving the stability and reliability of the system. By accurately adjusting the output voltage, the error amplifier EA can help the Flyback circuit operate at the optimal operating point, reduce unnecessary power loss, and improve the overall efficiency of the system.

[0068] In some optional embodiments, the control module further includes a comparator COMP; the second end of the sampling resistor ROUT is grounded, the first end of the sampling resistor ROUT is also connected to the positive input end of the comparator COMP, and the negative input end of the comparator COMP is used to input a set maximum voltage.

[0069] The control module is further configured to use a comparator COMP to compare the output voltage with a set maximum voltage for overvoltage detection. In the embodiments of the present application, the real-time monitoring function of the comparator COMP enables the system to rapidly respond to changes in the output voltage and, if an overvoltage condition occurs, immediately take protective measures. This rapid response capability improves the reliability and stability of the system.

[0070] In the embodiments provided in this application, it should be understood that the disclosed devices and methods can be implemented in other ways. The device embodiments described above are merely schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some communication interface, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0071] In addition, the units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0072] Furthermore, the functional modules in each embodiment of the present application can be integrated together to form an independent part, or each module can exist independently, or two or more modules can be integrated to form an independent part.

[0073] In this document, relational terms such as first and second, etc. are used merely to distinguish one entity or operation from another entity or operation, but do not necessarily require or imply any actual relationship or order between these entities or operations.

[0074] The above description is merely an embodiment of the present application and is not intended to limit the scope of protection of the present application. For those skilled in the art, various modifications and variations of the present application are possible. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A flyback ACDC switching power supply circuit, characterized in that: It includes a transformer, a MOS tube and a control module; the control module is used to send a PWM signal to the MOS tube, the MOS tube stores energy when it is turned on, and transfers energy to the output side when the MOS tube is turned off; The control module includes an output voltage detection circuit, a first end of the output voltage detection circuit is connected to the bus voltage, a second end of the output voltage detection circuit is connected to the primary winding of the transformer, and the output voltage detection circuit is used to obtain the output voltage based on the bus voltage and the voltage at the second end of the primary winding.

2. The circuit according to claim 1, wherein The output voltage detection circuit includes: a first voltage-to-current module, a second voltage-to-current module and a current difference module; The first voltage-to-current module is used to convert the bus voltage into a first current and output the first current to the first end of the current difference module; the second voltage-to-current module is used to convert the voltage at the second end of the primary winding into a second current and output the second current to the second end of the current difference module; the current difference module outputs a third current to the first end of the sampling resistor, and the second end of the sampling resistor is grounded; wherein the current value of the third current is the difference between the second current and the first current; and the voltage value of the output voltage is the product of the voltage at the first end of the sampling resistor and the corresponding coefficient.

3. The circuit according to claim 2, wherein: The control module also includes an error amplifier; The control module is further configured to use the error amplifier to compare the output voltage with a reference voltage to adjust the output voltage.

4. The circuit according to claim 3, wherein: The first end of the sampling resistor is also connected to the positive input end of the error amplifier, and the negative input end of the error amplifier is used to input a reference voltage.

5. The circuit according to claim 2, wherein: The control module further includes a comparator; The control module is further configured to use the comparator to compare the output voltage with a set maximum voltage to perform overvoltage detection.

6. The circuit according to claim 5, wherein: The second end of the sampling resistor is grounded, the first end of the sampling resistor is also connected to the positive input end of the comparator, and the negative input end of the comparator is used to input a set maximum voltage.

7. The circuit according to claim 2, wherein: The sampling resistor is a built-in resistor of the control module, and the sampling resistor, the resistor in the first voltage-to-current module, and the resistor in the second voltage-to-current module are resistors of the same type.

8. The circuit according to claim 2, wherein: The sampling resistor is an external resistor of the control module, and the sampling resistor is a zero temperature coefficient resistor; the output voltage detection circuit further includes: a ZTC module; The ZTC module is used to convert the third current into a fourth current with a zero temperature coefficient in both the first voltage-to-current module and the second voltage-to-current module, and output the fourth current to the first end of the sampling resistor.

9. The circuit according to claim 1, wherein: Also includes: a first diode, a second capacitor, and a fifth resistor; The second end of the primary winding of the transformer is connected to the input end of the first diode, the output end of the first diode is connected to the second end of the second capacitor and the second end of the fifth resistor, the first end of the second capacitor is connected to the bus voltage, and the first end of the fifth resistor is connected to the bus voltage.

10. The circuit according to claim 1, wherein Also includes: a second diode, a fourth capacitor, and a sixth resistor; The first end of the secondary winding of the transformer is connected to the input end of the second diode, the output end of the second diode is connected to the first end of the fourth capacitor and the first end of the sixth resistor, the second end of the fourth capacitor is connected to the second end of the secondary winding of the transformer, and the second end of the sixth resistor is connected to the second end of the secondary winding of the transformer.

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