Search

CN-122026731-A - Zero-current-switch active clamp forward converter and control method and equipment thereof

CN122026731ACN 122026731 ACN122026731 ACN 122026731ACN-122026731-A

Abstract

The invention discloses a zero-current switching active clamping forward converter and a control method and equipment thereof, and relates to the technical field of converters, and the technical scheme is characterized in that a resonant current signal is sampled from the secondary side of a transformer T1, an adaptive on-time signal is generated by combining a pulse signal, and a complementary driving signal with a dead zone is generated based on the adaptive on-time signal so as to control the on-off of a primary side main power MOS tube Q1 and a reset MOS tube Q2 in a main power circuit; the pulse signal is used for triggering the operation of the zero-crossing detection control unit, so that the self-adaptive on time signal dynamically adjusts the on time of the primary side main power MOS transistor Q1, the zero-current switching of the zero-current switching active clamping forward converter in the full load range can be ensured, the turn-off loss of the full load range of the power device in the converter can be reduced, the efficiency of the converter is improved, the harmonic wave of the switching process is reduced, and the EMI characteristic of the converter is optimized.

Inventors

  • ZHANG SHAN
  • WANG QINGMING
  • YE TAO
  • SHI WENLONG
  • YE YONG
  • TANG XIAOFAN
  • WANG XINGYUN

Assignees

  • 成都雷电微力科技股份有限公司

Dates

Publication Date
20260512
Application Date
20260415

Claims (10)

  1. 1. A zero current switching active clamp forward converter comprising a main power circuit (1) and a control module, characterized in that the control module comprises: A loop compensation unit (2) configured to receive an output voltage feedback signal of the main power circuit (1) and perform compensation operation; -a PFM control unit (3) connected to the loop compensation unit (2) configured to generate a pulse signal based on a compensation output; A zero-crossing detection control unit (4) connected to the PFM control unit (3) and connected to a secondary side of the transformer T1 in the main power circuit (1) through a current sampling unit, configured to generate an adaptive on-time signal based on a resonance current signal sampled from the secondary side of the transformer T1 and the pulse signal; The dead zone setting unit (5) is connected to the zero-crossing detection control unit (4) and is configured to generate a complementary driving signal with a dead zone based on the self-adaptive on-time signal so as to control the on and off of the primary main power MOS tube Q1 and the reset MOS tube Q2 in the main power circuit (1); the pulse signal is used for triggering the operation of the zero-crossing detection control unit (4), so that the self-adaptive on-time signal dynamically adjusts the on time of the primary side main power MOS tube Q1, and zero current turn-off of a full load range is realized.
  2. 2. The zero current switching active clamp forward converter of claim 1, wherein the current sampling unit is configured to: proportional amplification processing is carried out on the resonance current signal; the amplified signal is input to a ZCD port of the zero-crossing detection control unit (4) for zero-crossing detection.
  3. 3. The zero current switching active clamp forward converter of claim 1, wherein the zero crossing detection control unit (4) comprises a comparator CP, an SR flip-flop K1, a minimum TON generator TON2, a maximum TON generator TON1, a logic gate not gate N0T, a first AND gate AND1, AND a second AND gate AND2, wherein: The pulse signals are input to the minimum TON generator TON2 and the maximum TON generator TON1 and are used for generating a minimum pulse width signal and a maximum pulse width signal; The comparator CP is configured to compare the resonant current signal with a reference value and output a zero-crossing detection signal; The output end of the minimum TON generator TON2 is connected to the input end of the logic gate NOT gate N0T and the S input end of the SR trigger K1; The output end of the logical gate NOT gate N0T AND the output end of the comparator CP are connected to the input end of the first AND gate AND 1; the output end of the first AND gate AND1 is connected to the R input end of the SR flip-flop K1; The output end of the maximum TON generator TON1 AND the Q output end of the SR trigger K1 are connected to the input end of the second AND gate AND 2; the output terminal of the second AND gate AND2 outputs the adaptive on-time signal.
  4. 4. A zero current switching active clamp forward converter according to claim 3, characterized in that the minimum pulse width set by the minimum TON generator TON2 is larger than the dead time of the dead zone setting unit (5) to ensure the normal turn-on of the primary side main power MOS transistor Q1.
  5. 5. A zero current switching active clamp forward converter as claimed in claim 3 wherein said maximum TON generator TON1 sets a maximum pulse width for limiting the output of said adaptive on-time signal when said resonant current signal is abnormally non-zero crossing for fault protection.
  6. 6. The zero current switching active clamp forward converter of claim 1, wherein the main power circuit (1) further comprises a reset capacitor C1, a clamp diode D1, a transformer T1, a secondary leakage inductance Lr, a rectifier diode D2, a resonant capacitor Cr, a freewheeling diode D3, an output filter inductance Lf, an output capacitor Co, and an output load LODA, wherein: the source electrode of the primary side main power MOS tube Q1 is connected with an input positive electrode, and the drain electrode is connected with the primary side winding first end of the transformer T1, the first end of the reset capacitor C1 and the positive electrode of the clamping diode D1; The source electrode of the reset MOS tube Q2 is connected with the second end of the reset capacitor C1 and the negative electrode of the clamping diode D1, and the drain electrode is connected with the input negative electrode and the second end of the primary winding of the transformer T1; the first end of the secondary winding of the transformer T1 is connected with the first end of the secondary leakage inductance Lr, and the second end of the secondary leakage inductance Lr is connected with the anode of the rectifier diode D2; The cathode of the rectifying diode D2 is connected with the first end of the resonant capacitor Cr, the cathode of the freewheeling diode D3 and the first end of the output filter inductor Lf; The positive electrode of the freewheel diode D3 is connected with the second end of the secondary winding of the transformer T1, the second end of the resonance capacitor Cr, the first end of the output capacitor Co and the first end of the LODA; The second end of the output filter inductor Lf is connected with the second end of the output capacitor Co and the second end of the output load LODA; The secondary side leakage inductance Lr and the resonance capacitor Cr form a resonance network, so that the resonance current crosses zero in a full load range.
  7. 7. The control method of the zero-current switching active clamp forward converter is characterized by comprising the following steps of: receiving an output voltage feedback signal of the main power circuit (1) through a loop compensation unit (2) and performing compensation operation to generate a compensation output; generating a pulse signal by a PFM control unit (3) based on the compensation output; Receiving the pulse signal as a trigger by a zero crossing detection control unit (4) and generating an adaptive on-time signal based on a resonance current signal sampled from the secondary side of the transformer T1 in the main power circuit (1); based on the self-adaptive on-time signal, a complementary driving signal with a dead zone is generated through a dead zone setting unit (5) so as to control the on and off of an original side main power MOS tube Q1 and a reset MOS tube Q2 in the main power circuit (1) and realize zero current turn-off in a full load range.
  8. 8. The method for controlling a zero current switching active clamp forward converter of claim 7, the method is characterized in that the generation of the self-adaptive on-time signal comprises the following steps: based on the pulse signals, triggering a minimum TON generator TON 2to generate a minimum pulse width signal and a maximum TON generator TON1 to generate a maximum pulse width signal; setting an S input end of an SR trigger K1 based on the minimum pulse width signal to start the conduction of the primary side main power MOS tube Q1; When the resonance current signal crosses zero, generating a zero crossing detection signal, and generating a turn-off signal to an R input end of the SR trigger K1 by combining an inverse value of the minimum pulse width signal; And generating the self-adaptive on-time signal based on the output of the SR trigger K1 and the maximum pulse width signal phase so as to dynamically adjust the on-time of the primary side main power MOS tube and realize zero-current turn-off.
  9. 9. The control method of a zero current switching active clamp forward converter according to claim 8, wherein a minimum pulse width set by the minimum TON generator TON2 is greater than a dead time of the dead zone setting unit (5) to ensure normal turn-on of the primary side main power MOS transistor Q1; And/or, the maximum pulse width set by the maximum TON generator TON1 is used for limiting the output of the self-adaptive on-time signal when the resonance current signal is abnormal and cannot pass through zero, so as to realize fault protection.
  10. 10. An electronic device comprising at least one zero current switching active clamp forward converter as claimed in any one of claims 1 to 6 for providing a power output for said electronic device.

Description

Zero-current-switch active clamp forward converter and control method and equipment thereof Technical Field The invention relates to the technical field of converters, in particular to a zero-current-switch active clamping forward converter, and a control method and equipment thereof. Background Zero Current Switching (ZCS) active clamp forward converter topologies are categorized as resonant converters. The gain function of the output and input of the converter depends on the switching frequency of the converter, namely, the larger the required gain is, the higher the switching frequency is, and the smaller the gain is, the lower the switching frequency is. The topology is suitably controlled using PFM (Pulse Frequency Modulation) pulse frequency modulation control methods. The zero current switching active clamp forward converter in the prior art generally comprises a main power circuit and a control module, and the control module comprises a loop compensation unit, a PFM control unit, a fixed pulse width TON (Timer ON Delay) unit and a dead zone setting unit. The control strategy is that the output voltage of the main power circuit is fed back to the loop compensation unit for operation, the operated value is used for controlling the PFM control unit to generate a frequency pulse signal, the frequency pulse signal generates a frequency pulse signal with a fixed width through the fixed pulse width TON unit, and then a complementary driving signal with a dead zone is generated through the dead zone setting unit to drive a primary side main power MOS transistor (metal oxide semiconductor field effect transistor) Q1 and a reset MOS transistor Q2 in the main power circuit, so that the output of the converter is controlled. According to the load change, the PFM control unit outputs frequency pulses with different frequencies corresponding to different loads, but the pulse width of the driving signal in the full load range Q1 is kept unchanged, and only the frequency of the driving signal is changed. However, when the topology works normally, the secondary side leakage inductance Lr of the transformer T1 in the main power circuit resonates with the secondary side resonance capacitor Cr, the resonance current shows sine wave change, the resonance time changes according to the change of the load, and if the PFM control mode of conducting in fixed time is adopted, zero current turn-off can only be realized at a single load point, and cannot be realized in a full load range. Because TON time is fixed time, after resonant current reaches zero, Q1 drive can not be turned off, and the current passing through Q1 and D2 is not zero when the drive is turned off, so that ZCS can not be realized, loss of a circuit is increased, and EMI (electromagnetic interference) characteristics of the circuit are deteriorated. Therefore, the research and design of a zero-current-switch active clamp forward converter capable of overcoming the defects and a control method and equipment thereof are the problems which are urgently needed to be solved at present. Disclosure of Invention In order to solve the defects in the prior art, the invention aims to provide the zero-current switching active clamping forward converter, the control method and the control equipment thereof, which can ensure that the zero-current switching active clamping forward converter can realize zero-current switching in a full-load range, reduce the switching loss of a power device in the converter in the full-load range, improve the efficiency of the converter, reduce the harmonic wave of a switching process and optimize the EMI characteristic of the converter. The technical aim of the invention is realized by the following technical scheme: in a first aspect, a zero current switching active clamp forward converter is provided, comprising a main power circuit and a control module, the control module comprising: the loop compensation unit is configured to receive an output voltage feedback signal of the main power circuit and perform compensation operation; a PFM control unit connected to the loop compensation unit configured to generate a pulse signal based on a compensation output; A zero crossing detection control unit connected to the PFM control unit and connected to a secondary side of the transformer T1 in the main power circuit through a current sampling unit, configured to generate an adaptive on-time signal based on a resonance current signal sampled from the secondary side of the transformer T1 and the pulse signal; The dead zone setting unit is connected to the zero-crossing detection control unit and is configured to generate a complementary driving signal with a dead zone based on the self-adaptive on-time signal so as to control the on and off of a primary side main power MOS tube Q1 and a reset MOS tube Q2 in the main power circuit; The pulse signal is used for triggering the operation of the zero-crossing detection control unit, so that the self-ad