A multi-output isolated resonant gate drive circuit

Abstract

The application provides a multi-output isolated resonant gate drive circuit, which comprises a PWM generator, a MOS drive network, a multi-winding isolation transformer and a clamping circuit; wherein the gate control signals of the first PMOS tube and the second PMOS tube serving as drive tubes in the MOS drive network are respectively provided by the first PWM generator and the second PWM generator and the first gate driver and the second gate driver connected in sequence, the output of the MOS drive network is output to the clamping circuit through the multi-winding isolation transformer, the output signal of the clamping circuit serves as the gate drive signal of the primary side switch tube and the secondary side synchronous rectifier tube of LLC-DCX, and drives the primary side switch tube and the secondary side synchronous rectifier tube of LLC-DCX. The excitation inductance of the multi-winding isolation transformer in the isolated resonant gate drive circuit and the gate capacitance of the primary side power switch tube and the secondary side rectifier tube of LLC-DCX are utilized to generate resonance, recover the energy stored in the gate capacitance of the power switch tube and the rectifier tube, so as to reduce the loss of the gate drive circuit.

Description

Technical Field

[0001] This invention relates to the gate drive circuit of a DC transformer, and more particularly to a multi-output isolated resonant gate drive circuit. Background Technology

[0002] Switching power supplies are trending towards higher frequencies, higher efficiency, and smaller sizes. However, as switching frequencies increase, gate losses also increase. In converters with switching frequencies reaching the MHz level, gate drive losses have become a non-negligible issue. Therefore, reducing gate drive losses is crucial for improving converter efficiency and driving the development of high-frequency and high-power-density switching power supplies.

[0003] LLC-DCX features soft-switching characteristics, enabling ZVS and ZVS / ZCS for both primary-side and secondary-side MOSFETs, making it suitable for high-frequency, high-efficiency, and high-power-density applications. However, as switching frequencies increase, conventional voltage-source drivers lead to increased gate power losses independent of gate resistance. Past research has shown that resonant gate drive circuits are only suitable for single MOSFET drivers, requiring the addition of isolation or bootstrap circuitry to drive the high-side MOSFETs in the half-bridge arm. This typically increases component count and reduces system reliability. Another technique can provide two isolated complementary drive signals, but requires additional resonant inductor and large magnetic field designs, which are difficult to implement and miniaturize in high-frequency planes.

[0004] To address these issues, it is necessary to design a high-efficiency, high-reliability, miniaturized gate drive circuit capable of providing multiple complementary drive signals and suitable for high frequencies. This novel circuit should offer advantages such as reduced gate drive losses, improved efficiency, smaller size, and applicability to LLC resonant bridge DC-DC converters. Summary of the Invention

[0005] Technical Problem: This invention addresses the shortcomings of existing LLC-DCX gate drive circuits by proposing a multi-output isolated resonant gate drive circuit to provide multiple sets of isolated complementary drive signals. This reduces the number of components, lowers the drive loss of the LLC-DCX, thereby improving the overall efficiency of the LLC-DCX and enhancing system stability.

[0006] Technical solution:

[0007] A multi-output isolated resonant gate drive circuit includes a PWM generator, a MOS drive network, a multi-winding isolation transformer, and a clamping circuit.

[0008] The PWM generator includes a first PWM generator and a second PWM generator;

[0009] The MOS driving network includes a first PMOS transistor and a second PMOS transistor:

[0010] The sources of both the first PMOS transistor and the second PMOS transistor are connected to the power supply Vcc. The drain of the first PMOS transistor is connected to the same-name terminal of the first primary winding of the multi-winding isolation transformer, and the drain of the second PMOS transistor is connected to the opposite-name terminal of the third primary winding of the multi-winding isolation transformer.

[0011] The gate control signal of the first PMOS transistor is provided by the first PWM generator and its subsequent first gate driver; the gate control signal of the second PMOS transistor is provided by the second PWM generator and its subsequent second gate driver.

[0012] The output of the MOS driving network is output to the clamping circuit through a multi-winding isolation transformer. The output signal of the clamping circuit serves as the gate drive signal for the primary-side first switch, second switch, third switch, and fourth switch of the LLC-DCX and the secondary-side first synchronous rectifier, second synchronous rectifier, third synchronous rectifier, and fourth synchronous rectifier, driving the primary-side first switch, second switch, third switch, and fourth switch of the LLC-DCX and the secondary-side first synchronous rectifier, second synchronous rectifier, third synchronous rectifier, and fourth synchronous rectifier.

[0013] The magnetizing inductance of the multi-winding isolation transformer in the isolated resonant gate drive circuit and the gate capacitance of the primary-side power switch and the secondary-side rectifier of the LLC-DCX are used to generate resonance, thereby restoring the energy stored in the gate capacitance of the power switch and the rectifier, thus reducing the loss of the gate drive circuit.

[0014] The multi-winding isolation transformer has a primary winding comprising a first primary winding, a second primary winding, and a third primary winding.

[0015] The same-name terminal of the first primary winding is connected to the drain of the first PMOS transistor, and the opposite-name terminal of the first primary winding is connected to the gate of the fourth clamping transistor, the drain of the third clamping transistor, the second capacitor, and the same-name terminal of the second primary winding; the same-name terminal of the second primary winding is connected to the gate of the fourth clamping transistor, the drain of the third clamping transistor, the second capacitor, and the opposite-name terminal of the first primary winding, and the opposite-name terminal of the second primary winding is connected to the drain of the fourth clamping transistor, the gate of the third clamping transistor, the fourth capacitor, and the same-name terminal of the third primary winding; the same-name terminal of the third primary winding is connected to the drain of the fourth clamping transistor, the gate of the third clamping transistor, the fourth capacitor, and the opposite-name terminal of the second primary winding, and the opposite-name terminal of the third primary winding is connected to the drain of the second PMOS transistor;

[0016] The multi-winding isolation transformer has a secondary winding comprising a first winding, a second winding, and a third winding: the first winding is connected in parallel with a third capacitor; the second winding is connected in parallel with a first capacitor; the same-name terminal of the third winding is connected to the gate of a fifth clamping transistor, the drain of a sixth clamping transistor, and the gate equivalent capacitance; the opposite-name terminal of the third winding is connected to the drain of a fifth clamping transistor, the gate of a sixth clamping transistor, and the gate equivalent capacitance.

[0017] The clamping circuit includes a third clamping transistor, a fourth clamping transistor, a fifth clamping transistor, and a sixth clamping transistor:

[0018] The drain of the third clamping transistor is connected to the gate of the fourth clamping transistor, the second capacitor, the opposite terminal of the first primary winding and the same terminal of the second primary winding, and its gate is connected to the drain of the fourth clamping transistor, the fourth capacitor, the opposite terminal of the second primary winding and the same terminal of the third primary winding, and its source is grounded.

[0019] The source of the fourth clamping transistor is grounded, and its gate is connected to the drain of the third clamping transistor, the second capacitor, the opposite terminal of the first primary winding and the same terminal of the second primary winding. Its drain is connected to the gate of the third clamping transistor, the fourth capacitor, the opposite terminal of the second primary winding and the same terminal of the third primary winding.

[0020] The source of the fifth clamping transistor is grounded, and its gate is connected to the drain of the sixth clamping transistor, the same-name terminal of the third winding, and the equivalent capacitance of the second gate. Its drain is connected to the opposite-name terminal of the third winding, the gate of the sixth clamping transistor, and the equivalent capacitance of the first gate.

[0021] The source of the sixth clamping transistor is grounded, and its gate is connected to the drain of the fifth clamping transistor, the opposite terminal of the third winding, and the first gate equivalent capacitance. Its drain is connected to the same terminal of the third winding, the gate of the fifth clamping transistor, and the second gate equivalent capacitance.

[0022] Preferably, the primary side of the LLC-DCX is a series topology of resonant inductor, magnetizing inductor and resonant capacitor at the resonant frequency; wherein the LLC topology is a series topology of resonant inductor, magnetizing inductor and resonant capacitor.

[0023] Beneficial effects: The advantages of this invention are as follows:

[0024] 1) This invention is applicable to all bridge converters. It utilizes the magnetizing inductance of the multi-winding isolation transformer in the isolated resonant gate drive circuit and the gate capacitance of the primary-side power switch and the secondary-side rectifier of the bridge converter to generate resonance, thereby restoring the energy stored in the gate capacitance of the power switch and the rectifier, thus reducing the loss of the gate drive circuit and improving the overall efficiency of the circuit.

[0025] 2) This invention can operate within MHz frequency range. The gate drive signal provided can realize ZVS of the primary MOSFET and ZVS and ZCS of the secondary MOSFET of LLC-DCX, reducing switching losses and facilitating the miniaturization of power switches.

[0026] 3) This invention can provide multiple sets of complementary gate drive signals, which can provide all the signals required to drive the full-bridge converter, unlike other drive circuits that can only provide one or a set of gate drive signals.

[0027] 4) The present invention uses a small number of components, requiring only two PMOS driver transistors, two or four NMOS clamping transistors, and one multi-winding isolation transformer, resulting in low cost and high reliability;

[0028] 5) The driving circuit has a simple control timing. The two PMOS driving transistors require two complementary square wave signals, and the other clamping transistors do not require additional control signals to drive them. Attached image description:

[0029] Figure 1 This is the circuit diagram of the present invention;

[0030] Figure 2 This is the non-clamping circuit diagram of the circuit of this invention;

[0031] Figure 3 This is an LLC-DCX to which this invention applies;

[0032] Figure 4 This is a timing waveform diagram of the main driving signals of the circuit of this invention;

[0033] Figure 5 This is a timing waveform diagram of the main driving signals of the non-clamping structure of the circuit of this invention;

[0034] Figure 6 This is the actual output waveform of the gate drive circuit of this invention;

[0035] Figure 7 This is a comparison of the driving losses of traditional driver ICs and the driving losses of the circuit of this invention. Detailed implementation method:

[0036] like Figure 1The isolated resonant gate drive circuit includes a PWM generator, a MOS drive network, a multi-winding isolation transformer, and a clamping circuit. The PWM generator receives control signals PWM1 and PWM2 generated by the gate driver to control PMOS power transistors Q1 and Q2, respectively. PWM1 and PWM2 are two signals with a 180-degree phase difference. By changing their duty cycles, the required gate drive signal can be generated. The two PMOS drive transistors transmit the signals to the multi-winding isolation transformer. The signal on the primary winding P2 drives the low-side MOS transistors of the full-bridge converter, the signals on the secondary windings B1 and B2 drive the high-side MOS transistors, and the signal on the secondary winding B3 drives the synchronous rectifier. The drive signal and the drive voltage of the power switches in the full-bridge converter can be matched by changing the turns ratio of each winding and the number of secondary windings. The magnetizing inductance of the multi-winding isolation transformer in the isolated resonant gate drive circuit and the gate capacitance of the primary-side power switch and the secondary-side rectifier of the LLC-DCX are used to generate resonance, thereby restoring the energy stored in the gate capacitance of the power switch and the rectifier, thus reducing the loss of the gate drive circuit.

[0037] like Figure 2 ,right Figure 1 The changes made to the gate drive circuit removed clamping transistors Q5 and Q6 and added secondary winding B4, yet it still works... Figure 1 The circuits perform the same function.

[0038] like Figure 3 This is an LLC-DCX to which this invention applies. The multi-output drive signal of this invention can provide suitable gate drive signals for the primary-side switching transistors and secondary-side synchronous rectifier transistors of the full-bridge converter, so that they can function normally. Figure 1 or Figure 2 The output signals Vgs2, Vgs4, Vgs3, VHB2, Vgs1, VHB1, Vgsr1, Vgsr2 and Figure 3 Corresponding to the gate signal, MOSFETs S1, S2, S3, and S4 form a full-bridge topology. Lr1 and Lr2 are the leakage inductances of the transformer, Lm1 and Lm2 are the magnetizing inductances of the transformer, Cr is the resonant capacitor, SR1, SR2, SR3, and SR4 are the secondary-side synchronous rectifier diodes, Co is the output capacitor, and RL is the load. The drive signal provided by the isolated resonant gate drive circuit can achieve ZVS of the primary-side MOSFETs and ZVS and ZCS of the secondary-side MOSFETs in the LLC full-bridge converter, which is suitable for high-frequency, high-efficiency, and high-power-density applications.

[0039] like Figure 4 ,This is Figure 1The timing waveforms of the main drive signals in the circuit include control signals, current signals, and output voltage signals. The first and second rows, PWM1 and PWM2, represent the control signals for the MOS drive networks Q1 and Q2. The third and fourth rows, Vgs4 / Vgsr1, Vgs2 / Vgsr2, Vgs1-VHB3, and Vgs3-VHB2, represent the output signals of the gate drive circuit. The section marked with fast switching in the diagram represents the LC resonance stage. The energy for switching states is transferred through resonance, eliminating the need to absorb energy from the power supply and reducing energy consumption for drive losses. During the excitation stage, energy is recovered and released from the power supply without being released to ground, which is beneficial for energy circulation. The fifth, sixth, and seventh rows show the current waveforms on the primary and secondary windings of the multi-winding isolation transformer, illustrating the resonance and excitation processes.

[0040] like Figure 5 ,This is Figure 2 The timing waveforms of the main driving signals in the circuit include control signals, current, and output voltage signals. Figure 4 Basically the same, but the clamping transistors Q5 and Q6 are removed from the secondary winding, and a secondary winding B4 is added. Therefore, Vgsr2 and Vgsr1 are no longer clamped and are under negative voltage in half of the cycle, while the resonance time is doubled.

[0041] like Figure 6 This is the waveform of the output signal of the resonant gate drive circuit of the present invention, and... Figure 4 The output waveforms are consistent, and the output waveforms can be changed by adjusting the frequency and duty cycle of PWM1 and PWM2, thereby meeting the requirements of the converter control signal.

[0042] like Figure 7 This is a line graph comparing the driving losses of the isolated resonant gate driving circuit of this invention and the traditional IC driving circuit for driving LLC-DCX with varying switching frequencies. As can be seen from the graph, the driving losses of the circuit of this invention are much smaller than those of the traditional circuit. Furthermore, the higher the switching frequency, the greater the reduction in driving losses of the circuit of this invention, and the more obvious the advantages.

[0043] The working process of this invention is as follows:

[0044] During the period t0-t1, the initial voltages on Cg4, Cg1, and Cgsr1 are high, clamping MOSFETs Q3 and Q6 are turned on, all other MOSFETs are turned off, and Cg4, Cg1, Cgsr1, and the transformer's magnetizing inductor resonate. Cg4, Cg1, and Cgsr1 discharge resonantly, while the resonant inductor charges resonantly. The gate-source voltage decreases, and the current on the resonant inductor increases. Energy is transferred from the gate capacitor to the resonant inductor until the gate capacitor is fully discharged.

[0045] During the period t1-t2, the inductor current is continuous. The resonant inductor charges the gate capacitors Cg2, Cg3, and Cgsr2 until the clamping transistors Q4 and Q5 are turned on. The clamping MOSFETs Q4 and Q5 achieve ZVS. Cg2, Cg3, Cgsr2 and the transformer inductor resonate to form a circuit. The energy of the resonant inductor is transferred to the gate capacitor, and the gate voltage continues to rise until the voltages of Vgs2, Vgs3-VHB2 and Vgsr2 are clamped by Vcc.

[0046] During the period t2-t3: the current in the transformer flows upward through the body diode of PMOS Q1 into the power supply, and the gate voltage is clamped by Vcc. At this time, Q1 conducts, achieving ZVS. During this process, the energy in the transformer is recovered, and the current in the transformer flows into the power supply until the current is zero.

[0047] During the period t3-t4, drive transistor Q1 and clamping transistor Q4 are turned on, the power supply excites the magnetizing inductor, and the current direction is opposite to that during t3-t4, until Q1 is turned off, and the first half of the cycle ends.

[0048] The resonance and excitation processes from t4 to t8 in the second half of the cycle are similar to those from t0 to t4 in the first half of the cycle. Together, they constitute a complete cycle and form a loop.

[0049] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A multi-output isolated resonant gate drive circuit, characterized in that, Includes PWM generator, MOS drive network, multi-winding isolation transformer, and clamping circuit: The PWM generator includes a first PWM generator and a second PWM generator; The MOS driving network includes a first PMOS transistor and a second PMOS transistor: The sources of both the first PMOS transistor and the second PMOS transistor are connected to the power supply Vcc. The drain of the first PMOS transistor is connected to the same-name terminal of the first primary winding of the multi-winding isolation transformer, and the drain of the second PMOS transistor is connected to the opposite-name terminal of the third primary winding of the multi-winding isolation transformer. The gate control signal of the first PMOS transistor is provided by the first PWM generator and its subsequent first gate driver; the gate control signal of the second PMOS transistor is provided by the second PWM generator and its subsequent second gate driver. The output signal of the clamping circuit serves as the gate drive signal for the primary-side first switch, second switch, third switch, and fourth switch of the LLC-DCX, and the secondary-side first synchronous rectifier, second synchronous rectifier, third synchronous rectifier, and fourth synchronous rectifier. The multi-winding isolation transformer has a primary winding comprising a first primary winding, a second primary winding, and a third primary winding. The same-name terminal of the first primary winding is connected to the drain of the first PMOS transistor, and the opposite-name terminal of the first primary winding is connected to the gate of the fourth clamping transistor, the drain of the third clamping transistor, the second capacitor, and the same-name terminal of the second primary winding; the same-name terminal of the second primary winding is connected to the gate of the fourth clamping transistor, the drain of the third clamping transistor, the second capacitor, and the opposite-name terminal of the first primary winding, and the opposite-name terminal of the second primary winding is connected to the drain of the fourth clamping transistor, the gate of the third clamping transistor, the fourth capacitor, and the same-name terminal of the third primary winding; the same-name terminal of the third primary winding is connected to the drain of the fourth clamping transistor, the gate of the third clamping transistor, the fourth capacitor, and the opposite-name terminal of the second primary winding, and the opposite-name terminal of the third primary winding is connected to the drain of the second PMOS transistor; The multi-winding isolation transformer has a secondary winding comprising a first winding, a second winding, and a third winding; the first winding and the third capacitor are connected in parallel; the second winding and the first capacitor are connected in parallel. The clamping circuit includes a third clamping transistor, a fourth clamping transistor, a fifth clamping transistor, and a sixth clamping transistor: The drain of the third clamping transistor is connected to the gate of the fourth clamping transistor, the second capacitor, the opposite terminal of the first primary winding and the same terminal of the second primary winding, and its gate is connected to the drain of the fourth clamping transistor, the fourth capacitor, the opposite terminal of the second primary winding and the same terminal of the third primary winding, and its source is grounded. The source of the fourth clamping transistor is grounded, and its gate is connected to the drain of the third clamping transistor, the second capacitor, the opposite terminal of the first primary winding and the same terminal of the second primary winding. Its drain is connected to the gate of the third clamping transistor, the fourth capacitor, the opposite terminal of the second primary winding and the same terminal of the third primary winding. The source of the fifth clamping transistor is grounded, and its gate is connected to the drain of the sixth clamping transistor, the same-name terminal of the third winding, and the equivalent capacitance of the second gate. Its drain is connected to the opposite-name terminal of the third winding, the gate of the sixth clamping transistor, and the equivalent capacitance of the first gate. The source of the sixth clamping transistor is grounded, and its gate is connected to the drain of the fifth clamping transistor, the opposite terminal of the third winding, and the first gate equivalent capacitance. Its drain is connected to the same terminal of the third winding, the gate of the fifth clamping transistor, and the second gate equivalent capacitance.

2. The multi-output isolated resonant gate drive circuit as described in claim 1, characterized in that, The primary side of the LLC-DCX is a series topology of resonant inductor, magnetizing inductor and resonant capacitor at the resonant frequency.

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