DCM-based double-transistor flyback converter of integrated buck converter
By integrating the buck converter into the dual-transistor flyback converter and controlling the switching of the switching transistors with pulse width modulation signals, zero-voltage turn-on is achieved, solving the problems of multiple component configurations and high losses, and improving the reliability and efficiency of the system.
Patent Information
- Application Number
- CN202421696909.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-16
- Publication Date
- 2025-12-16
- Estimated Expiration
- 2034-07-16
AI Technical Summary
In scenarios requiring both dual-tube flyback converters and buck converters, there is a problem of a large number of components and high losses and costs.
By integrating the buck converter into the dual-transistor flyback converter, the number of components is reduced by sharing the first switching transistor and the second diode, and zero-voltage turn-on is achieved by controlling the switching transistor with a pulse width modulation signal.
It reduces the number of components, lowers circuit losses, improves overall efficiency, and increases system reliability and lifespan.
Smart Images
Figure CN223680942U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of switching power supply, and particularly relates to a dual-tube flyback converter of an integrated step-down converter based on DCM. BACKGROUND
[0002] The dual tubes of the dual-tube flyback converter refer to two switching tubes in the converter circuit, including a first switching tube and a second switching tube. The circuit loop of the flyback converter is composed of a direct-current power supply, the first switching tube, the second switching tube, a transformer and a clamping diode, and the circuit loop of the step-down converter is composed of a power supply, a switching tube and a freewheeling diode.
[0003] The two switching tubes in the dual-tube flyback converter can share voltage and current evenly, thereby reducing the stress of each switching tube and improving the overall reliability and service life of the system. The dual-tube flyback converter can obtain energy transmission and be isolated from dangerous high voltage. The step-down converter usually has high efficiency, simple structure, easy control and fast dynamic response capability, and can rapidly adjust the output voltage to cope with load changes. However, in the scenario requiring both the dual-tube flyback converter and the step-down converter, there are problems of a large number of component configurations and high loss cost. SUMMARY
[0004] The application aims to provide a dual-tube flyback converter of an integrated step-down converter based on DCM to solve the problems in the background.
[0005] To achieve the above-mentioned purpose, the application provides the following technical scheme: a dual-tube flyback converter of an integrated step-down converter based on DCM, characterized in that it comprises a dual-tube flyback converter and a step-down converter, the first switching tube Q1 and the second diode D2 are used in common to integrate the step-down converter into the dual-tube flyback converter, so as to reduce the number of components; the dual-tube flyback converter is used for an external load with isolation requirement; the secondary winding Ns in the dual-tube flyback converter is one or more than one winding; and the step-down converter is used for an external load without isolation requirement.
[0006] The double-tube flyback converter comprises a switching unit 100, a high-frequency transformer, a rectification and filtering unit 200 and a load R1; the switching unit 100 of the double-tube flyback converter is composed of a first switch tube Q1, a second switch tube Q2, a first diode D1 and a second diode D2; the high-frequency transformer T is used for storing and transferring energy, the primary winding Np of the high-frequency transformer T is connected between the connection point of the first switch tube Q1 and the second diode D2 and the connection point of the second switch tube Q2 and the first diode D1, and the secondary winding Ns of the high-frequency transformer T is connected to the rectification and filtering unit 200; the rectification and filtering unit 200 comprises a rectification diode D3 and a filtering capacitor C1; the energy stored in the high-frequency transformer T is transferred to a direct-current output Vo1 through the rectification and filtering unit 200, thereby providing energy for the load R1.
[0007] The buck converter comprises a switching unit 300, an inductor L2, an output filtering unit 400 and a load R2; the switching unit 300 is composed of a first switch tube Q1 and a second diode D2; the inductor L2 is used for storing and transferring energy; the output filtering unit 400 is composed of a filtering capacitor C2; the positive electrode of the inductor L2 is connected to the connection point of the first switch tube Q1 and the second diode D2, and the negative electrode of the inductor L2 is connected to the positive electrode of the filtering capacitor C2; the energy stored in the inductor L2 is transferred to a direct-current output Vo2 through the filtering capacitor C2, thereby providing energy for the load R2.
[0008] The positive electrode of the direct-current input Vin is connected to the cathode of the first diode D1, the anode of the first diode D1 is connected to the source of the second switch tube Q2, and the drain of the second switch tube Q2 is connected to the cathode of the direct-current input Vin, thereby forming a loop; the positive electrode of the direct-current input Vin is connected to the source of the first switch tube Q1, the drain of the first switch tube Q1 is connected to the cathode of the second diode D2, and the anode of the second diode D2 is connected to the negative electrode of the direct-current input Vin, thereby forming a loop; the same end of the primary winding Np of the high-frequency transformer T is connected to the connection point of the drain of the first switch tube Q1 and the cathode of the second diode D2, and the different end of the primary winding Np of the high-frequency transformer T is connected to the connection point of the source of the second switch tube Q2 and the anode of the first diode D1; the different end of the secondary winding Ns of the high-frequency transformer T is connected to the anode of the rectification diode D3, the cathode of the rectification diode D3 is connected to the positive electrode of the filtering capacitor C1, the negative electrode of the filtering capacitor C1 is connected to the same end of the secondary winding Ns of the high-frequency transformer T, thereby forming a loop; the positive electrode of the load R1 is connected to the positive electrode of the filtering capacitor C1, and the negative electrode of the load R1 is connected to the negative electrode of the filtering capacitor C1, thereby forming a loop; the above loops form the double-tube flyback converter.
[0009] The positive pole of the direct current input Vin is connected to the source of the first switch tube Q1, the drain of the first switch tube Q1 is connected to the negative pole of the second diode D2, and the positive pole of the direct current input Vin is connected to the negative pole of the second diode D2 to form a loop; the positive pole of the inductor L2 is connected to the connection point of the drain of the first switch tube Q1 and the negative pole of the second diode D2, the negative pole of the inductor L2 is connected to the positive pole of the filter capacitor C2, the positive pole of the filter capacitor C2 is connected to the negative pole of the direct current input Vin to form a loop; the positive pole of the load R2 is connected to the positive pole of the filter capacitor C2, and the negative pole of the load R2 is connected to the positive pole of the filter capacitor C2 to form a loop; the above loop forms a step-down converter.
[0010] The pulse width modulation signal input into the control end of the first switch tube Q1 controls the switch of the first switch tube Q1, and further controls the output of the step-down converter; the period of the pulse width modulation signal input into the control end of the first switch tube Q1 is of a set length, and the duty cycle of the pulse width modulation signal input into the control end of the first switch tube Q1 is less than 0.5; the second switch tube Q2 is controlled by the pulse width modulation signal input into the control end of the second switch tube Q2; the period of the pulse width modulation signal input into the control end of the second switch tube Q2 is the same as the period of the pulse width modulation signal input into the control end of the first switch tube Q1; the duty cycle of the pulse width modulation signal input into the control end of the second switch tube Q2 is less than or equal to the duty cycle of the pulse width modulation signal input into the control end of the first switch tube Q1. The effective duty cycle of the first switch tube Q1 and the second switch tube Q2 controls the output of the double-tube flyback converter, and the effective duty cycle refers to the duty cycle of the pulse width modulation signal when the first switch tube Q1 and the second switch tube Q2 are turned on at the same time.
[0011] The converter has the following beneficial effects: the zero-voltage turn-on of the second switch tube Q2 is realized, and the switching loss of the power switch tube is reduced. The integrated step-down converter reduces the number of components and reduces the cost. The circuit loss is reduced, and the overall efficiency is increased. BRIEF DESCRIPTION OF DRAWINGS
[0012] Figure 1 is a structural schematic diagram of the double-tube flyback converter circuit of the integrated step-down circuit adopted by the present application;
[0013] Figure 2 is a working mode diagram when the voltage between the second switch tube Q2 is zero. DETAILED DESCRIPTION
[0014] The present application will be further described in detail below with reference to the accompanying drawings.
[0015] Figure 1is a structural schematic diagram of the integrated step-down converter of the present application, which comprises a switching unit 100, a high-frequency transformer T, a rectification and filtering unit 200, an inductor coil L2, an output filtering unit 400; the switching unit 100 is composed of a first switch tube Q1, a second switch tube Q2, a first diode D1 and a second diode D2; the switching unit 100 contains a switching unit 300; the rectification and filtering unit 200 is composed of a rectification diode D3 and a filtering capacitor C1; the high-frequency transformer T is used for storing and transferring energy, the primary winding Np of the high-frequency transformer T is one winding, and the secondary winding Ns is one or more windings; the energy stored by the high-frequency transformer T is transferred to a direct current output Vo1 through the rectification and filtering unit 200 to provide energy for a load R1; the output filtering unit 400 is composed of a filtering capacitor C2; the inductor coil L2 is used for storing and transferring energy; the energy stored by the inductor coil L2 is transferred to a direct current output Vo2 through the output filtering unit 400 to provide energy for a load R2.
[0016] The specific connection mode is as follows: the positive pole of the direct current input Vin is connected to the cathode of the first diode D1, the anode of the first diode D1 is connected to the source of the second switch tube Q2, the drain of the second switch tube Q2 is connected to the cathode of the direct current input Vin to form a loop; the positive pole of the direct current input Vin is connected to the source of the first switch tube Q1, the drain of the first switch tube Q1 is connected to the cathode of the second diode D2, and the anode of the second diode D2 is connected to the negative pole of the direct current input Vin to form a loop; the same-named end of the primary winding Np of the high-frequency transformer T is connected to the connection point of the drain of the first switch tube Q1 and the cathode of the second diode D2, and the different-named end of the primary winding Np of the high-frequency transformer T is connected to the connection point of the source of the second switch tube Q2 and the anode of the first diode D1; the different-named end of the secondary winding Ns of the high-frequency transformer T is connected to the anode of the rectification diode D3, the cathode of the rectification diode D3 is connected to the positive pole of the filtering capacitor C1, the negative pole of the filtering capacitor C1 is connected to the same-named end of the secondary winding Ns of the high-frequency transformer T to form a loop; the positive pole of the load R1 is connected to the positive pole of the filtering capacitor C1, and the negative pole of the load R1 is connected to the positive and negative poles of the filtering capacitor C1 to form a loop; the positive pole of the inductor coil L2 is connected to the connection point of the drain of the first switch tube Q1 and the cathode of the second diode D2, the negative pole of the inductor coil L2 is connected to the positive pole of the filtering capacitor C2, and the negative pole of the filtering capacitor C2 is connected to the negative pole of the direct current input Vin to form a loop; the positive pole of the load R2 is connected to the positive pole of the filtering capacitor C2, and the negative pole of the load R2 is connected to the positive and negative poles of the filtering capacitor C2 to form a loop.
[0017] The pulse width modulation signal inputted to the control end of the first switch tube Q1 controls the switch of the first switch tube Q1, and further controls the output of the voltage reduction converter; the period of the pulse width modulation signal inputted to the control end of the first switch tube Q1 is set length, and the duty cycle of the pulse width modulation signal inputted to the control end of the first switch tube Q1 is less than 0.5; the second switch tube Q2 is controlled by the pulse width modulation signal inputted to the control end of the second switch tube Q2; the period of the pulse width modulation signal inputted to the control end of the second switch tube Q2 is the same as the period of the pulse width modulation signal inputted to the control end of the first switch tube Q1; the duty cycle of the pulse width modulation signal inputted to the control end of the second switch tube Q2 is less than or equal to the duty cycle of the pulse width modulation signal inputted to the control end of the first switch tube Q1. The effective duty cycle of the first switch tube Q1 and the second switch tube Q2 controls the output of the double switch tube flyback converter, and the effective duty cycle refers to the duty cycle of the pulse width modulation signal when the first switch tube Q1 and the second switch tube Q2 are simultaneously turned on.
[0018] Figure 2 The circuit is the working mode diagram when the voltage across the second switch tube Q2 of the present application is zero, Figure 2 In the circuit, the pulse width modulation signals inputted to the control ends of the first switch tube Q1 and the second switch tube Q2 are all low level, the first switch tube Q1 and the second switch tube Q2 are in the off state, the second diode is turned on, and the energy stored in the inductor L2 is transferred to the direct current output Vo2; the first diode D1 and the rectifier diode D3 bear the reverse voltage and are in the off state; the parasitic capacitance of the second switch tube Q2 and the parasitic capacitance of the first diode resonate with the excitation inductance, so that the voltage across the second switch tube Q2 drops to zero, and thus the second switch tube Q2 will realize zero voltage turn-on in the next period.
Claims
1. A dual-transistor flyback converter based on a DCM-integrated buck converter, characterized in that, The system includes a dual-transistor flyback converter and a buck converter. The dual-transistor flyback converter includes a switching unit (100), a high-frequency transformer T, a rectifier and filter unit (200), and a load R1. The switching unit (100) of the dual-transistor flyback converter consists of a first switch Q1, a second switch Q2, a first diode D1, and a second diode D2. The high-frequency transformer T includes a primary winding Np and a secondary winding Ns. The two ends of the primary winding Np are connected between the connection point of the first switch Q1 and the second diode D2 and the connection point of the second switch Q2 and the first diode D1. The two ends of the secondary winding Ns are connected to the rectifier and filter unit (200). The rectifier and filter unit (200) includes a rectifier diode D3 and a filter capacitor C1. The energy stored in the high-frequency transformer T is transferred to the DC output Vo1 through the rectifier and filter unit (200) to provide energy for the load R1. The buck converter includes a switching unit (300), an inductor L2, an output filter unit (400), and a load R2. The switching unit (300) consists of a first switching transistor Q1 and a second diode D2. The inductor L2 is used to store and transfer energy. The output filter unit (400) consists of a filter capacitor C2. The positive terminal of the inductor L2 is connected to the connection point between the first switching transistor Q1 and the second diode D2, and the negative terminal is connected to the positive terminal of the filter capacitor C2. The energy stored in the inductor L2 is transferred to the DC output Vo2 through the output filter unit (400) to provide energy for the load R2. The positive terminal of the DC input Vin is connected to the cathode of the first diode D1, the anode of the first diode D1 is connected to the source of the second switch Q2, and the drain of the second switch Q2 is connected to the negative terminal of the DC input Vin, forming a circuit. The positive terminal of the DC input Vin is also connected to the source of the first switch Q1, the drain of the first switch Q1 is connected to the cathode of the second diode D2, and the anode of the second diode D2 is connected to the negative terminal of the DC input Vin, forming a circuit. The corresponding terminal of the primary winding Np of the high-frequency transformer T is connected to the drain of the first switch Q1 and the second diode D2. At the cathode connection point, the opposite terminal of the primary winding Np of the high-frequency transformer T is connected to the connection point between the source of the second switching transistor Q2 and the anode of the first diode D1; the opposite terminal of the secondary winding Ns of the high-frequency transformer T is connected to the anode of the rectifier diode D3, the cathode of the rectifier diode D3 is connected to the positive terminal of the filter capacitor C1, and the negative terminal of the filter capacitor C1 is connected to the same terminal of the secondary winding Ns of the high-frequency transformer T, forming a loop; the positive terminal of the load R1 is connected to the positive terminal of the filter capacitor C1, and the negative terminal of the load R1 is connected to the negative terminal of the filter capacitor C1, forming a loop; the above loop constitutes a two-transistor flyback converter. The positive terminal of the DC input Vin is connected to the source of the first switching transistor Q1, the drain of the first switching transistor Q1 is connected to the cathode of the second diode D2, and the anode of the second diode D2 is connected to the negative terminal of the DC input Vin, forming a circuit. The positive terminal of the inductor L2 is connected to the junction of the drain of the first switching transistor Q1 and the cathode of the second diode D2, and the negative terminal of the inductor L2 is connected to the positive terminal of the filter capacitor C2. The negative terminal of the filter capacitor C2 is connected to the negative terminal of the DC input Vin, forming a circuit. The positive terminal of the load R2 is connected to the positive terminal of the filter capacitor C2, and the negative terminal of the load R2 is connected to the negative terminal of the filter capacitor C2, forming a circuit. The above circuit constitutes the buck converter.
2. The dual-transistor flyback converter according to claim 1, characterized in that, The primary winding Np of the high-frequency transformer T is a single winding, and the secondary winding NS is one or more windings.