Active clamping parameter design method for full-wave rectification circuit

Abstract

The invention discloses an active clamping absorption circuit parameter design method, which is applied to a full-wave rectification circuit of a phase-shifted full-bridge converter, is used for absorbing leakage inductance and voltage spike and oscillation generated by parasitic capacitance resonance of a rectification tube, and comprises the following steps: acquiring output filter inductance current, calculating the primary side resonant inductance peak current of the transformer according to the filter inductance current; calculating the charging time of the clamping capacitor; the absorption circuit parameters are calculated according to the relation between the absorption circuit parameters and the transformer primary side resonant inductance current peak value and the clamping capacitor charging time; according to the active clamping absorption circuit parameter design method, the parameter design process can be simplified, and voltage spike and oscillation can be effectively suppressed.

Description

Technical Field

[0001] The present invention relates to the field of rectifier circuits of power converters, and particularly to a method for designing active clamping parameters of a full-wave rectifier circuit of a phase-shifted full-bridge DC / DC converter. Background Art

[0002] In a switching power supply with low-voltage and large-current output, the rectifier circuit on the secondary side of the transformer generally adopts synchronous rectification technology to reduce losses, and mostly uses a full-wave rectifier circuit. However, when the voltage on the secondary side of the transformer changes, the leakage inductance of the transformer and the stray inductance in the circuit will resonate with the parasitic capacitance of the switching tube, generating very large voltage oscillations, which is more serious in the scenario of large-current output. In severe cases, the peak value of this voltage spike can reach twice the voltage on the secondary side of the transformer. Excessively high voltage spikes will, on the one hand, cause a large voltage stress on the rectifier tube, reducing reliability, and on the other hand, will also bring electromagnetic compatibility problems.

[0003] In the current absorption circuits, the active clamping circuit is more widely used due to its good voltage spike absorption effect and low loss. However, when designing the device parameters of the active clamping circuit, they are usually selected based on experience and actual debugging results. Since actual debugging is relatively complex, there will be problems of reducing work efficiency and extending the product development cycle. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for designing active clamping circuit parameters.

[0005] The technical solution for achieving the purpose of the present invention is as follows:

[0006] The first step: Installation of the phase-shifted full-bridge DC / DC converter

[0007] 1.1 The phase-shifted full-bridge DC / DC converter mainly consists of a power unit, a signal acquisition unit, a control unit, and an external environment unit. Among them, the power unit includes an input filter capacitor C1(1), a DC high-voltage module (2), a resonant inductor L r (3), a high-frequency isolation transformer T(4), a rectification module (5), an active clamping absorption circuit (6), an output filter inductor L f (7), and an output filter capacitor C2(8); the signal acquisition unit includes a clamping capacitor voltage detector (9), an output filter capacitor voltage detector (10), and an output filter inductor current detector (11); the control unit includes an embedded microprocessor (12); the external environment unit includes a DC power supply (13) and a load (14);

[0008] 1.2 According to the structural relationship in step 1.1, install and arrange the phase-shifted full-bridge DC / DC converter:

[0009] The DC high-voltage module (1) is of a full-bridge structure and consists of fully-controlled devices S1 to S4; the positive pole of the DC high-voltage module (1) is connected to the positive pole of the input filter capacitor C1 and the positive pole of the DC power supply, and the negative pole is connected to the negative pole of C1 and the negative pole of the DC power supply (14); the midpoints of the two bridge arms of the DC high-voltage module are connected to the primary side of the transformer T(5) through the resonant inductor L(4);

[0010] The rectification module a(6) is of a full-wave rectification structure and consists of N-channel metal-oxide-semiconductor field-effect transistors S5 and S6. The S poles of S5 and S6 are respectively connected to both ends of the secondary side winding of the transformer, and the D poles are connected to the output filter inductor; the active clamp absorption circuit consists of an N-channel metal-oxide-semiconductor field-effect transistor S7 and an absorption capacitor C s which is composed of, S7 is connected to the D poles of S5 and S6, and the absorption capacitor C s is connected to the negative pole of the output filter capacitor C2(8), and both ends of the output filter inductor are respectively connected to the D poles of S5 and S6 and the positive pole of the output filter capacitor;

[0011] Step 2: Collect the high-voltage side voltage V1, the output filter capacitor voltage V2, the clamping capacitor voltage V C and the output filter inductor current I o through the signal sampling unit, and set the turns ratio of the primary and secondary sides of the high-frequency isolation transformer T(5) to N;

[0012] Step 3: Input the output filter inductor current I o and the clamping capacitor voltage V C into the embedded microprocessor (14), and obtain the peak value of the primary side resonant inductor current through formula (1):

[0013]

[0014] In the formula, Lr is the inductance value of the resonant inductor, and C S is the capacitance value of the clamping capacitor;

[0015] The duration of the clamping diode body diode conduction to charge the absorption capacitor can be estimated by the following formula:

[0016]

[0017] In the formula, C n is the parasitic capacitance of the switching tube;

[0018] Step 4: According to the peak value of the resonant inductor current and the duration t of the clamping diode body diode conduction to charge the absorption capacitor obtained in the fourth step, the absorption capacitor parameters can be calculated through the following formula:

[0019]

[0020] Where Δv is the allowable change in the voltage of the absorption capacitor.

[0021] Step 5: Apply the drive signal PWM7 to the switching device in the active absorption circuit through the embedded microprocessor (14), and control the conduction and cutoff of S7 to realize the charging and discharging of the absorption capacitor, thereby achieving the purpose of suppressing the voltage spike of the rectifier diode. Description of the Drawings

[0022] Figure 1 It is the topological structure diagram of the phase-shifted full-bridge DC / DC converter with active clamping of the present invention.

[0023] Figure 2 It is the implementation flowchart of the present invention.

[0024] Figure 3 It is the drive signal diagram of the present invention. Detailed Implementation Manner

[0025] The present invention will be further described below with reference to the drawings.

[0026] Figure 1 It is the topological structure diagram of the phase-shifted full-bridge DC / DC converter with active clamping of the present invention. And it can be combined with Figure 2 the shown implementation flowchart to determine the absorption capacitor parameters, achieve the purpose of suppressing the voltage spike at both ends of the rectifier diode, reduce the voltage stress of the rectifier diode, improve the power density of the converter, and its usage method includes the following content:

[0027] Step 1: Installation of the phase-shifted full-bridge DC / DC converter

[0028] 1.1 The phase-shifted full-bridge DC / DC converter mainly consists of a power unit, a signal acquisition unit, a control unit, and an external environment unit. Among them, the power unit includes an input filter capacitor C1(1), a DC high-voltage module (2), a resonant inductor L r (3), a high-frequency isolation transformer T(4), a rectification module (5), an active clamping absorption circuit (6), an output filter inductor L f (7), and an output filter capacitor C2(8); the signal acquisition unit includes a clamping capacitor voltage detector (9), an output filter capacitor voltage detector (10), and an output filter inductor current detector (11); the control unit includes an embedded microprocessor (12); the external environment unit includes a DC power supply (13) and a load (14);

[0029] 1.2 According to the structural relationship in step 1.1, install and arrange the phase-shifted full-bridge DC / DC converter:

[0030] The DC high-voltage module (1) has a full-bridge structure and is composed of fully-controlled devices S1 to S4; the positive electrode of the DC high-voltage module (1) is connected to the positive electrode of the input filter capacitor C1 and the positive electrode of the DC power supply, and the negative electrode is connected to the negative electrode of C1 and the negative electrode of the DC power supply (14); the midpoints of the two bridge arms of the DC high-voltage module are connected to the primary side of the transformer T(5) through the resonance inductor L(4);

[0031] The rectification module a(6) has a full-wave rectification structure and is composed of N-channel metal oxide semiconductor field effect transistors S5 and S6. The S electrodes of S5 and S6 are respectively connected to both ends of the secondary side winding of the transformer, and the D electrodes are connected to the output filter inductor; the active clamp absorption circuit is composed of the N-channel metal oxide semiconductor field effect transistor S7 and the absorption capacitor C s where S7 is connected to the D electrodes of S5 and S6, and the absorption capacitor C s is connected to the negative electrode of the output filter capacitor C2(8), and both ends of the output filter inductor are respectively connected to the D electrodes of S5 and S6 and the positive electrode of the output filter capacitor;

[0032] Step 2: Collect the high-voltage side voltage V1, the output filter capacitor voltage V2, the clamp capacitor voltage V C and the output filter inductor current I o through the signal sampling unit, and set the turns ratio of the primary and secondary sides of the high-frequency isolation transformer T(5) to N;

[0033] Step 3: Input the output filter inductor current I o and the clamp capacitor voltage V C into the embedded microprocessor (14), and obtain the peak value of the primary side resonance inductor current through formula (1):

[0034]

[0035] In the formula, Lr is the inductance value of the resonance inductor, and C S is the capacitance value of the clamp capacitor;

[0036] The duration of the clamp tube body diode conduction to charge the absorption capacitor can be estimated by the following formula:

[0037]

[0038] In the formula, C n is the parasitic capacitance of the switching tube;

[0039] Step 4: According to the peak value of the resonance inductor current obtained in Step 4 and the duration t of the clamp tube body diode conduction to charge the absorption capacitor, the absorption capacitor parameters can be calculated through the following formula:

[0040]

[0041] Where Δv is the allowable change in the voltage of the absorption capacitor.

[0042] Step 5: Apply the drive signal PWM7 to the switching device in the active absorption circuit through the embedded microprocessor (14), and realize the charging and discharging of the absorption capacitor by controlling the conduction and cut-off of S7, so as to achieve the purpose of suppressing the voltage spike of the rectifier diode.

Claims

1. An active clamping parameter design method for a full-wave rectifier circuit to improve the parameter design efficiency of an active absorption circuit, characterized in that parameters are obtained through theoretical calculation, avoiding multiple debugging, including the following steps: The first step: Installation of a phase-shifted full-bridge DC / DC converter 1.1 The phase-shifted full-bridge DC / DC converter mainly consists of a power unit, a signal acquisition unit, a control unit, and an external environment unit. Among them, The power unit includes an input filter capacitor C1(1), a DC high-voltage module (2), a resonant inductor L r (3), a high-frequency isolation transformer T(4), a rectification module (5), an active clamp absorption circuit (6), an output filter inductor L f (7) and an output filter capacitor C2(8); the signal acquisition unit includes a clamp capacitor voltage detector (9), an output filter capacitor voltage detector (10), and an output filter inductor current detector (11); the control unit includes an embedded microprocessor (12); the external environment unit includes a DC power supply (13) and a load (14); 1.2 According to the structural relationship in step 1.1, install and arrange the phase-shifted full-bridge DC / DC converter: The DC high-voltage module (1) is of a full-bridge structure and consists of fully controlled devices S1 to S4; the positive pole of the DC high-voltage module (1) is connected to the positive pole of the input filter capacitor C1 and the positive pole of the DC power supply, and the negative pole is connected to the negative pole of C1 and the negative pole of the DC power supply (14); the midpoints of the two bridge arms of the DC high-voltage module are connected to the primary side of the transformer T(5) through the resonant inductor L(4); The rectification module a (6) is a full-wave rectification structure, which is composed of N-channel metal-oxide-semiconductor field-effect transistors S5 and S6. The S poles of S5 and S6 are respectively connected to both ends of the secondary side winding of the transformer, and the D poles are connected to the output filter inductor; The active clamp absorption circuit is composed of an N-channel metal-oxide-semiconductor field-effect transistor S7 and an absorption capacitor C s and S7 is connected to the D poles of S5 and S6, and the absorption capacitor C s is connected to the negative pole of the output filter capacitor C2 (8), and both ends of the output filter inductor are respectively connected to the D poles of S5 and S6 and the positive pole of the output filter capacitor; Step 2: Collect the high-voltage side voltage V1, the output filter capacitor voltage V2, the clamping capacitor voltage V C and the output filter inductor current I o , and set the turns ratio of the primary and secondary sides of the high-frequency isolation transformer T(5) to N; Step 3: Input the output filter inductor current I o and the clamping capacitor voltage V C into the embedded microprocessor (14), and obtain the peak value of the primary resonant inductor current through Equation (1): where Lr is the inductance value of the resonant inductor, and C S is the capacitance value of the clamping capacitor; The duration for the clamping body diode to conduct and charge the absorption capacitor can be estimated by the following formula: where C n is the parasitic capacitance of the switching transistor; Step 4: According to the peak value of the resonant inductor current obtained in the fourth step and the duration t for the clamping body diode to conduct and charge the absorption capacitor, the absorption capacitor parameters can be calculated by the following formula: In the formula, Δv is the allowable voltage change of the absorption capacitor. Step 5: Apply the drive signal PWM7 to the switching device in the active absorption circuit through the embedded microprocessor (14), and realize the charging and discharging of the absorption capacitor by controlling the conduction and cutoff of S7, so as to achieve the purpose of suppressing the voltage spike of the rectifier diode.

Images