A resonant ZVS isolation boost circuit and a control method thereof

Abstract

The application discloses a resonant ZVS isolation boost circuit and a control method thereof, and belongs to the field of power supply technology.The resonant ZVS isolation boost circuit comprises an improved Royer resonance and voltage transformation rectifier circuit, a current hysteresis mode control circuit and a half-bridge switching circuit.The drain of the fifth and sixth NMOS tubes in the half-bridge switching circuit is led out to one end of the fourth inductor of the improved Royer resonance and voltage transformation rectifier circuit; the output capacitor of the improved Royer resonance and voltage transformation rectifier circuit is connected to two input ends of a feedback control module of the current hysteresis mode control circuit; the source of the first and second NMOS tubes of the improved Royer resonance and voltage transformation rectifier circuit is connected to one end of a current detection resistor of the current hysteresis mode control circuit; the positive output end of an RS latch of the current hysteresis mode control circuit is connected to the positive input end of a half-bridge driving module of the half-bridge switching circuit; and the negative output end is connected to the negative input end of the half-bridge driving module.The application can realize stable boost output under constant voltage input.

Description

Technical Field

[0001] The present invention relates to the technical field of isolated boost circuits, and in particular to a resonant ZVS isolated boost circuit and a control method thereof. Background Art

[0002] The traditional resonant ZVS isolated boost circuit has been around for a long time. Versions using MOSFETs as switching devices cleverly exploit the current excitation characteristics of the LC parallel resonant circuit, resulting in a sinusoidal half-wave drain voltage waveform. When the voltage crosses zero, the switching transistor alternates, allowing the MOSFET to operate in a ZVS state. This offers advantages such as a simple circuit, low losses, high oscillation frequency, and low interference. However, the traditional resonant ZVS isolated boost circuit's circuit topology lacks voltage regulation capabilities, making it incapable of stabilizing the output voltage, limiting its application. Furthermore, traditional resonant ZVS isolated boost circuits exhibit a slow response to input voltage and suffer from a volt-second imbalance across the transformer, potentially leading to core saturation. Summary of the Invention

[0003] The purpose of the present invention is to overcome the shortcomings and deficiencies of the prior art and to provide a compact, reliable and efficient resonant ZVS isolated boost circuit and a control method thereof.

[0004] To achieve the above objectives, the present invention provides a technical solution: a resonant ZVS isolated boost circuit, comprising an improved Royer resonant and transformer rectifier circuit, a current hysteresis mode control circuit, and a half-bridge switch circuit; the source of the fifth NMOS transistor and the drain of the sixth NMOS transistor in the half-bridge switch circuit are connected to one end of the fourth inductor of the improved Royer resonant and transformer rectifier circuit, the two ends of the output capacitor of the improved Royer resonant and transformer rectifier circuit are connected to the two input ends of the feedback control module of the current hysteresis mode control circuit, the sources of the first and second NMOS transistors of the improved Royer resonant and transformer rectifier circuit are connected to one end of the current sensing resistor of the current hysteresis mode control circuit, the positive output end of the RS latch of the current hysteresis mode control circuit is connected to the positive input end of the half-bridge drive module in the half-bridge switch circuit, and the negative output end is connected to the negative input end of the half-bridge drive module;

[0005] The improved Royer resonance and transformer rectification circuit includes first to fourth NMOS transistors, a resonant capacitor, first and second inductors on the primary side of the transformer, a third and fourth inductors on the secondary side of the transformer, first to fourth diodes for rectification, an output capacitor, and an external first power supply; wherein, the sources of the first and second NMOS transistors are connected, the gate of the first NMOS transistor is connected to the source of the fourth NMOS transistor, the drain of the first NMOS transistor is respectively connected to the drain of the third NMOS transistor and one end of the resonant capacitor, the gate of the second NMOS transistor is connected to the source of the third NMOS transistor, and the drain of the second NMOS transistor is respectively connected to the drain of the fourth NMOS transistor and the resonant capacitor The other end of the output capacitor is connected to the external first power supply, the gates of the third and fourth NMOS transistors are respectively connected, the two opposite-name ends of the first and second inductors are respectively connected to the two ends of the resonant capacitor, the other two opposite-name ends of the first and second inductors are connected and connected to the other end of the fourth inductor, the positive electrode of the first diode and the cathode of the third diode are connected to one end of the third inductor, the positive electrode of the second diode and the negative electrode of the fourth diode are connected to the other end of the third inductor, the cathodes of the first diode and the second diode are connected, and the positive electrodes of the third diode and the fourth diode are connected; the cathodes of the first diode and the second diode are connected to one end of the output capacitor, and the positive electrodes of the third diode and the fourth diode are connected to the other end of the output capacitor.

[0006] Furthermore, the current hysteresis mode control circuit includes a feedback control module, a current sensing resistor, a current sensing amplifier, a high-end comparator, a low-end comparator and an RS latch; the positive output end of the feedback control module is connected to the positive input end of the high-end comparator, and the negative output end is connected to the negative input end of the low-end comparator; the negative input end of the current sensing amplifier is grounded, and the positive input end is connected to the non-grounded end of the current sensing resistor; the R pin of the RS latch is connected to the output of the high-end comparator, the S pin is connected to the output of the low-end comparator, the positive output Q pin is connected to the positive input end of the half-bridge drive module in the half-bridge switch circuit, and the negative output / Q pin is connected to the negative input end of the half-bridge drive module.

[0007] Furthermore, the half-bridge switching circuit includes an external second power supply, a half-bridge driving module, and fifth and sixth NMOS tubes; the drain of the fifth NMOS tube is connected to the external second power supply, the gate is connected to the positive output of the half-bridge driving module, the source is connected to the drain of the sixth NMOS tube, the gate of the sixth NMOS tube is connected to the negative output of the half-bridge driving module, and the drain is grounded.

[0008] The present invention also provides a control method for the above-mentioned resonant ZVS isolation boost circuit, the specific process is as follows:

[0009] Since the transformer resonance peak voltage of the improved Royer resonance and transformer rectification circuit is positively correlated with the current source current equivalent to the fourth inductor, in order to stabilize the output voltage of the improved Royer resonance and transformer rectification circuit, the current hysteresis mode control circuit and the half-bridge switch circuit need to effectively control the average current of the fourth inductor. For the improved Royer resonance and transformer rectification circuit, the current flows into one side of the fourth inductor and flows out from the ground terminals of the first and second NMOS tubes. For this reason, the current detection resistor in the current hysteresis mode control circuit is connected to the original ground terminals of the first and second NMOS tubes. The voltage at both ends of the resistor is amplified by the current detection amplifier and enters the high and low end comparators to compare with the high and low end comparators from the feedback control module in the current hysteresis mode control circuit. The two current threshold signals of the low-end comparator are compared; when the current detection signal output by the current detection amplifier reaches the current upper limit set by the feedback control module and the high-end and low-end comparators, the high-end comparator outputs a low level to the R pin of the RS latch, and the RS latch is reset, so that the half-bridge driver module in the half-bridge switch circuit controls the fifth NMOS transistor to turn off and the sixth NMOS transistor to turn on, at which time the current of the fourth inductor decreases; when the current detection signal output by the current detection amplifier reaches the current lower limit set by the feedback control module and the high-end and low-end comparators, the low-end comparator outputs a low level to the S pin of the RS latch, and the RS latch is set, so that the half-bridge driver module in the half-bridge switch circuit controls the fifth NMOS transistor to turn on and the sixth NMOS transistor to turn off, at which time the current of the fourth inductor increases;

[0010] The above process is repeated continuously, so that the current of the fourth inductor can be maintained between the upper and lower current limits set by the feedback control module and the high-side and low-side comparators.

[0011] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0012] By improving upon the traditional Royer oscillator circuit, the present invention effectively increases the switching rate of the NMOS transistor in the improved Royer resonant and transformer-rectifier circuit, significantly reducing the switching losses of the NMOS transistor. Furthermore, compared to conventional voltage-mode control circuits, the current hysteresis mode control circuit of the present invention incorporates a current-sense amplifier, allowing the input current to fluctuate within a set range. This solves the problem of magnetic saturation of the inductor at both ends of the transformer's primary intermediate tap and improves the response speed of the output voltage of the improved Royer resonant and transformer-rectifier circuit to the input voltage.

[0013] The improved Royer resonant and transformer-rectifier circuit replaces the diode and resistor power supply method with a source-follower NMOS transistor power supply method, significantly increasing the conduction rate of the NMOS switch and reducing switching losses. The current hysteresis mode control circuit uses a detection circuit to add current feedback to the original voltage feedback method, improving the circuit's response rate to input voltage. This invention can achieve stable boosted output under constant voltage input conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a schematic diagram of the resonant ZVS isolation boost circuit of the present invention.

[0015] Figure 2 This is the schematic diagram of the classic resonant Royer oscillator circuit.

[0016] Figure 3 This is the schematic diagram of the improved Royer resonance and transformer rectification circuit.

[0017] Figure 4 This is an explanatory schematic diagram of the classic resonant Royer oscillator circuit.

[0018] Figure 5 This is the S-domain equivalent block diagram of the center-tapped parallel resonant circuit.

[0019] Figure 6 This is the tapped LC resonant circuit current source excitation waveform.

[0020] Figure 7 This is a working waveform diagram of the resonant ZVS isolation boost circuit of the present invention.

[0021] Figure 8 This is the specific implementation principle diagram of the feedback control module.

[0022] Figure 9 This is a specific circuit diagram for practical applications. DETAILED DESCRIPTION

[0023] The present invention will be described in further detail below with reference to the embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0024] like Figure 1 As shown, this embodiment discloses a resonant ZVS isolated boost circuit, including an improved Royer resonant and transformer rectifier circuit I, a current hysteresis mode control circuit II, and a half-bridge switch circuit III. The source of the fifth NMOS transistor M5 and the drain of the sixth NMOS transistor M6 in the half-bridge switch circuit III are connected to one end of the fourth inductor L4 of the improved Royer resonant and transformer rectifier circuit I, and the output capacitor C of the improved Royer resonant and transformer rectifier circuit I is connected to the output capacitor C of the improved Royer resonant and transformer rectifier circuit I. outThe two ends are connected to the two input ends of the feedback control module of the current hysteresis mode control circuit II, and the sources of the first and second NMOS tubes M1 and M2 of the improved Royer resonance and transformer rectifier circuit I are connected to the current sensing resistor R of the current hysteresis mode control circuit II. s One end of the RS latch U1 of the current hysteresis mode control circuit II is connected to the positive input end of the half-bridge driving module in the half-bridge switching circuit III, and the negative output end is connected to the negative input end of the half-bridge driving module.

[0025] First use Figure 2 Explain the working process of the classic resonant Royer oscillator circuit: In the classic resonant Royer oscillator circuit, after the power source V2 is connected in series with the fourth inductor L4, its properties are similar to those of a current source because the inductor current cannot change suddenly. After the power supply is turned on, the voltage V1 passes through R c 、R d This causes the gate voltages of NMOS transistors M1 and M2 to rise, causing them to alternately conduct. Because components in actual circuits rarely have identical performance, the two NMOS transistors' conduction levels increase at different rates. When the conduction level of one NMOS transistor reaches a sufficient level, it pulls down the gate voltage of the other NMOS transistor through one of the diodes, D1 or D2. This puts the two NMOS transistors in a state where one is fully on and the other is fully off. Once the circuit stabilizes, M1 and M2 alternately conduct.

[0026] The classic resonant Royer oscillator circuit has some defects. In the stable oscillation state, the diode here can be equivalent to a resistor under the AC oscillation voltage. Because the diode and the resistor R connected to the anode of the diode are c 、R d , the equivalent input capacitance C of the first and second NMOS tubes M1 and M2 iss Together with the external first power supply V1, they form a first-order resistance-capacitance circuit. Therefore, in the classic resonant Royer oscillation circuit, the resonant capacitor C R When the voltage rises rapidly, the gate voltage of the NMOS transistors M1 and M2 rises very slowly, resulting in a slow conduction rate. This may cause voltage and current to coexist between the drain and source of the NMOS transistors, increasing power consumption and damaging the device. The most direct improvement method is to reduce the resistance between the gates of the NMOS transistors M1 and M2 and the power supply. However, if the resistance is directly reduced, the voltage at the gates of the NMOS transistors M1 and M2 may not be sufficient to drop to 0V, making it impossible to shut down. Therefore, the present invention further improves the gate drive circuit based on the classic resonant Royer oscillator circuit to obtain an improved Royer resonance and transformer rectifier circuit I.

[0027] The improved Royer resonance and transformer rectification circuit I includes the first to fourth NMOS tubes M1, M2, M3, M4, the resonant capacitor C R , the first and second inductors L1 and L2 on the primary side of the transformer, the third inductor L3 and the fourth inductor L4 on the secondary side of the transformer, the first to fourth diodes D1, D2, D3, D4 for rectification, and the output capacitor C out And the external first power supply V1; wherein, the source of the first and second NMOS tubes M1 and M2 are connected, the gate of the first NMOS tube M1 is connected to the source of the fourth NMOS tube M4, and the drain of the first NMOS tube M1 is respectively connected to the drain of the third NMOS tube M3 and the resonant capacitor C R The gate of the second NMOS tube M2 is connected to the source of the third NMOS tube M3, and the drain of the second NMOS tube M2 is connected to the drain of the fourth NMOS tube M4 and the resonant capacitor C R The other end of the external first power supply V1 is connected to the gate of the third and fourth NMOS tubes M3 and M4 respectively, and the two opposite-name ends of the first and second inductors L1 and L2 are connected to the resonant capacitor C R The other two opposite-name terminals of the first and second inductors L1 and L2 are connected and connected to the other end of the fourth inductor L4. The positive electrode of the first diode D1 and the cathode of the third diode D3 are connected to one end of the third inductor L3. The positive electrode of the second diode D2 and the cathode of the fourth diode D4 are connected to the other end of the third inductor L3. The cathodes of the first diode D1 and the second diode D2 are connected, and the positive electrodes of the third diode D3 and the fourth diode D4 are connected. The cathodes of the first diode D1 and the second diode D2 are connected to the output capacitor C out One end of the third diode D3 and the anode of the fourth diode D4 are connected to the output capacitor C out the other end.

[0028] The improved Royer resonance and transformer rectifier circuit I adds a pair of fourth and third NMOS transistors M4 and M3 working in source follower state to control the gate voltages of the first and second NMOS transistors M1 and M2 respectively. Figure 3As shown in the figure. From the perspective of the gate of NMOS transistor M1 (or M2), when the voltage at point B (or A) rises rapidly, due to the source-follower nature of NMOS transistor M4 (or M3), the gate of NMOS transistor M1 (or M2) is equivalent to being directly connected to the external first power supply V1. When the voltage at point B (or A) is zero, a parallel equivalent diode in the NMOS transistor equivalent model pulls down the gate voltage of NMOS transistor M1 (or M2). The turn-off process of NMOS transistor M1 (or M2) is consistent with that of a classic resonant Royer oscillator circuit. Based on the above analysis, it can be concluded that the improved circuit reduces the resistance in the first-order RC circuit while allowing the gate voltages of the first and second NMOS transistors M1 and M2 to be pulled down normally. This circuit greatly improves the switching speed of M1 and M2 and further reduces their switching losses.

[0029] Next, under stable conditions, the oscillation process of the improved Royer resonance and transformer rectifier circuit I is qualitatively explained.

[0030] First, at the moment D is fully turned on and C is fully turned off: the current IB flowing through L2 reaches its maximum sinusoidal value, and the current IA flowing through L1 reaches its minimum sinusoidal value. Current IA (>0) flows from the middle capacitor to the right, charging it. VA starts to rise from 0, and VD rises accordingly (stopping rising when VD = Vdd). Current IB (<0) flows from the middle capacitor to the right, charging it. Since D is fully turned on, VB = 0, which turns C off.

[0031] IA rises and IB falls until IA=IB=0: the voltage VA reaches its maximum, which makes VD reach its maximum and the D tube remains in the on state.

[0032] IA continues to rise, and IB continues to fall until transistor D begins to cut off. Voltage VA begins to fall, and voltage VD begins to fall, causing the capacitor to discharge in the opposite direction. Transistor D begins to cut off, causing VB to rise, which in turn causes VC to rise, eventually bringing the voltage across the capacitor to zero. Due to the capacitor's charging direction, VB rises, and transistor C begins to conduct.

[0033] IA continues to rise and IB continues to fall until IA reaches its maximum sinusoidal value and IB reaches its minimum value. At this point, C is fully turned on and D is fully turned off, forming a half cycle.

[0034] According to the qualitative analysis of the alternating switching process of the transistors in the above stabilization process, it can be found that the improved Royer resonance and transformer rectifier circuit I flips over just when the absolute value of the current IA or IB reaches a maximum value, so that the current source can continuously input energy to the improved Royer resonance and transformer rectifier circuit I at the appropriate position in each half cycle, and finally the output voltage can be continuously increased.

[0035] Since the first and second NMOS tubes M1 and M2 are turned on alternately, each turn-on alternation is equivalent to the improved Royer resonance and transformer rectification circuit I, the transformer primary is measured by the first and second inductors L1 and L2, the resonant capacitor C R The tapped LC resonant circuit is excited by the step current source, so the improved Royer resonance and transformer rectifier circuit I can be equivalent to Figure 4 To explain, R eq Used to equalize the load effect produced by the secondary of the transformer.

[0036] Next, we will quantitatively analyze the improved Royer resonance and transformer rectifier circuit I. Figure 4 After the circuit is linearized, the circuit is analyzed from the Laplace transform domain (hereinafter referred to as the s domain, s is the complex number of the Laplace transform complex frequency domain), and the following equation can be obtained, where the voltage v1 is the voltage at the non-grounded point at both ends of L1 and L2, and the voltage V M is the voltage of the middle tap of L1 and L2, L1 is the inductance value of inductor L1, L2 is the inductance value of inductor L2, M is the mutual inductance value between inductors L1 and L2, C R is the inductor C R The inductance value, R eq is the equivalent resistance R eq The resistance value, I in For the equivalent input current, the voltage v1 can be calculated using equation (1):

[0037]

[0038] Solving the above equation, we can get Figure 5 The block diagram of linear representation in the s-domain is shown. K is the inductance proportional coefficient. The algebraic expression of the voltage v1 in the s-domain is calculated. Then, the time domain expression function of the voltage v1 under the step response current can be obtained based on the Laplace transform table. According to the time domain expression function of the voltage v1, it is found that the voltage v1 is exactly a decaying sine wave. For the convenience of representation, let C = C R , R=R eq , L = L2 + M, V = v1, t is the time in seconds. The time domain expression function V(t) for voltage V = v1 can be obtained as follows.

[0039]

[0040] Under the excitation of the step current source, due to the characteristics of the LC parallel resonant circuit, the voltage at the ungrounded end will show a decaying sinusoidal resonant waveform, starting from 0 voltage and rising according to the sinusoidal waveform, returning to zero after passing the highest point of the resonant voltage, such as Figure 6As shown. In the improved Royer resonance and transformer rectifier circuit I, taking M2 turned on and M1 turned off as an example, the drain voltage waveform of M1 will experience a process of rising from 0V to the resonant voltage peak and then to 0V. However, when the drain voltage of M1 drops to 0V, the gate of M2 is pulled down, turning it off. At the same time, M2 releases the other end of the LC resonant circuit, and the gate of M1 is no longer pulled down, allowing M1 to be fully turned on and enter the next cycle, so that the oscillation is maintained. The actual waveform is shown in the figure Figure 7 As shown, V(vc) is the control voltage waveform of the half-bridge driving module in the half-bridge switching circuit III, I(L5) is the current waveform flowing through the fourth inductor L4, V(vo) is the output voltage waveform of the improved Royer resonance and transformer rectifier circuit I, V(d1) is the drain waveform of the first NMOS transistor M1, V(d2) is the drain waveform of the second NMOS transistor M2, V(g1) is the gate waveform of the first NMOS transistor M1, and V(g2) is the gate waveform of the second NMOS transistor M2.

[0041] The current hysteresis mode control circuit II includes a feedback control module, a current sensing resistor R S , current-sense amplifier CsAmp, high-end comparator cmpH, low-end comparator cmPL and RS latch U1; the positive output of the feedback control module is connected to the positive input of the high-end comparator cmpH, the negative output is connected to the negative input of the low-end comparator cmPL, the negative input of the current-sense amplifier CsAmp is grounded, and the positive input is connected to the current-sense resistor R s The non-grounded end of the RS latch U1 is connected to the R pin of the RS latch U1, which is connected to the output of the high-side comparator cmpH, the S pin is connected to the output of the low-side comparator cmPL, the positive output Q pin is connected to the positive input of the half-bridge driver module in the half-bridge switch circuit III, and the negative output / Q pin is connected to the negative input of the half-bridge driver module.

[0042] The half-bridge switching circuit III includes an external second power supply V2, a half-bridge driving module, and fifth and sixth NMOS transistors M5 and M6; the drain of the fifth NMOS transistor M5 is connected to the external second power supply V2, the gate is connected to the positive output of the half-bridge driving module, the source is connected to the drain of the sixth NMOS transistor M6, the gate of the sixth NMOS transistor M6 is connected to the negative output of the half-bridge driving module, and the drain is grounded.

[0043] Because the transformer resonant peak voltage of the improved Royer resonance and transformer-rectifier circuit I is positively correlated with the current source current equivalent to L4, circuits II and III must be able to effectively control the average current of L4 to stabilize the output voltage of circuit I. For circuit I, the current flows into one side of inductor L4 and must flow out from the ground terminals of the first and second MOS transistors. Therefore, a low-cost and easy-to-implement low-side current sensing solution can be adopted. To this end, the current sensing resistor R in the current hysteresis mode control circuit II is connected to the original ground terminals of the first and second NMOS transistors M1 and M2 in circuit I. s The voltage across the L4 is amplified by the current-sense amplifier CsAmp and then enters the high-side and low-side comparators CmpH and CmpL, where it is compared with the two current threshold signals from the feedback control module and the high-side and low-side comparators CmpH and CmpL in Circuit II. When the current-sense signal output by the current-sense amplifier CsAmp reaches the upper current limit set by the feedback control module and the high-side and low-side comparators CmpH and CmpL, CmpH outputs a low level to the R terminal of the RS latch U1, resetting U1 and causing the half-bridge driver module in Circuit III to control M5 to turn off and M6 to turn on, resulting in a decrease in the current of L4. When the current-sense signal output by the CsAmp reaches the lower current limit set by the feedback control module and the high-side and low-side comparators CmpH and CmpL, CmpL outputs a low level to the S terminal of the RS latch U1, setting U1 and causing the half-bridge driver module in Circuit III to control M5 to turn on and M6 to turn off, resulting in an increase in the current of L4. Repeating the above process maintains the current in L4 within the upper and lower limits set by the feedback control module and the high- and low-side comparators CmpH and CmpL. Compared to conventional voltage-mode control circuits, this current hysteresis mode control circuit II incorporates a current-sense amplifier to prevent excessive peak current. To ensure a constant output voltage, conventional voltage-mode control circuits use output voltage feedback to adjust the voltage, while a feedback circuit connected from the output to the input adjusts the constant current in the Royer oscillator circuit. This current hysteresis mode control circuit II improves the output voltage response of the improved Royer resonant and transformer-rectifier circuit I to input voltage changes. If a voltage-mode control circuit is used, when the input voltage fluctuates, the input voltage change must wait until the output changes before being fed back to the half-bridge driver. With the current-sense comparator CsAmp, an increase in input voltage causes the input current slope to increase. This change in current slope is then fed back to the half-bridge switching circuit III, improving the system's response speed.

[0044] The feedback control module in the current hysteresis mode control circuit II can be composed of Figure 8 given. Figure 8 In, V outRepresents the voltage output by the circuit. This voltage is a constant value when the circuit is stable. R2 and R3 are voltage divider resistors. Generally, R2 is much larger than R3. The voltage on R2 provides a voltage reference for the controllable precision voltage regulator D5. According to the description in the TL431A data sheet, this controllable precision voltage regulator has a built-in 2.5V reference voltage. When the reference voltage of the right-side measured by D5 is greater than 2.5V, the cathode voltage of D5 becomes 0, thereby turning on the optocoupler circuit on the left, reducing the positive and negative output voltages V of the feedback control module. fbH 、V fbL , reduce the current in the Royer oscillation circuit, so that the voltage V out When the reference voltage of the right side of D5 is less than 2.5V, the cathode voltage of D5 becomes 5V, which turns on the left side of the optocoupler circuit and increases V fbH 、V fbL , reduce the current in the Royer oscillation circuit, so that the voltage V out Therefore, the voltage V can be divided by resistors R2 and R3. out The control formula of the output voltage by the resistor is as follows, where V ref The internal reference voltage of the voltage regulator. Figure 8 The feedback control module uses V ref The value is 2.5V.

[0045]

[0046] Figure 8 The feedback control module given will V out The voltage divided to the reference voltage of the controllable precision voltage regulator D5 is transmitted to the circuit on the left through the optocoupler. out When the voltage reaches the lower limit below 400V, the optocoupler turns on and V fbH 、V fbL The high-side comparator cmpH of the current hysteresis mode control circuit II outputs a high level, the low-side comparator cmPL outputs a low level, the RS latch is set, and the half-bridge driver module starts to provide energy to the improved Royer resonance and transformer rectifier circuit I, and the output voltage rises; when the output voltage V out When the voltage reaches the upper limit of 400V, the optocoupler is turned off and V fbH 、V fbL When the output voltage V out When the target output voltage is near, the optocoupler is partially turned on, V fbH 、V fbLThe value of causes the high-side and low-side comparators cmpH and cmpl to output high levels simultaneously, and the RS latch maintains the previous state. In this way, the circuit can output a stable DC voltage.

[0047] Finally, the actual circuit schematic is as follows Figure 9 shown.

[0048] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A resonant ZVS isolated boost circuit, characterized by: The invention comprises an improved Royer resonance and transformer rectification circuit (I), a current hysteresis mode control circuit (II) and a half-bridge switch circuit (III); the source of the fifth NMOS tube (M5) and the drain of the sixth NMOS tube (M6) in the half-bridge switch circuit (III) are led to one end of the fourth inductor (L4) of the improved Royer resonance and transformer rectification circuit (I), and the output capacitor (C out ) are connected to the two input ends of the feedback control module of the current hysteresis mode control circuit (II), and the source of the first and second NMOS tubes (M1, M2) of the improved Royer resonance and transformer rectification circuit (I) are connected to the current detection resistor (R s ), the positive output end of the RS latch (U1) of the current hysteresis mode control circuit (II) is connected to the positive input end of the half-bridge driving module in the half-bridge switching circuit (III), and the negative output end is connected to the negative input end of the half-bridge driving module; The improved Royer resonance and transformer rectification circuit (I) comprises first to fourth NMOS tubes (M1, M2, M3, M4), a resonant capacitor (C R ), the first and second inductors (L1, L2) on the primary side of the transformer, the third inductor (L3), the fourth inductor (L4) on the secondary side of the transformer, the first to fourth diodes (D1, D2, D3, D4) for rectification, the output capacitor (C out ) and an external first power supply (V1); wherein the sources of the first and second NMOS transistors (M1, M2) are connected, the gate of the first NMOS transistor (M1) is connected to the source of the fourth NMOS transistor (M4), and the drain of the first NMOS transistor (M1) is respectively connected to the drain of the third NMOS transistor (M3) and the resonant capacitor (C R ), the gate of the second NMOS transistor (M2) is connected to the source of the third NMOS transistor (M3), and the drain of the second NMOS transistor (M2) is connected to the drain of the fourth NMOS transistor (M4) and the resonant capacitor (C R ), the other end of the external first power supply (V1) is connected to the gate of the third and fourth NMOS transistors (M3, M4), and the two opposite-name ends of the first and second inductors (L1, L2) are connected to the resonant capacitor (C R ), the other two opposite-named ends of the first and second inductors (L1, L2) are connected and connected to the other end of the fourth inductor (L4), the positive electrode of the first diode (D1) and the negative electrode of the third diode (D3) are connected to one end of the third inductor (L3), the positive electrode of the second diode (D2) and the negative electrode of the fourth diode (D4) are connected to the other end of the third inductor (L3), the negative electrodes of the first diode (D1) and the second diode (D2) are connected, and the positive electrodes of the third diode (D3) and the fourth diode (D4) are connected; the negative electrodes of the first diode (D1) and the second diode (D2) are connected to the output capacitor (C out ), the anodes of the third diode (D3) and the fourth diode (D4) are connected to the output capacitor (C out ) at the other end.

2. The resonant ZVS isolated boost circuit according to claim 1, characterized in that: The current hysteresis mode control circuit (II) includes a feedback control module, a current detection resistor (R s ), a current-sense amplifier (CsAmp), a high-end comparator (cmpH), a low-end comparator (cmpL) and an RS latch (U1); the positive output of the feedback control module is connected to the positive input of the high-end comparator (cmpH), and the negative output is connected to the negative input of the low-end comparator (cmpL); the negative input of the current-sense amplifier (CsAmp) is grounded, and the positive input is connected to the current-sense resistor (R s ) non-grounded end; the R pin of the RS latch (U1) is connected to the output of the high-side comparator (cmpH), the S pin is connected to the output of the low-side comparator (cmpL), the positive output Q pin is connected to the positive input end of the half-bridge driver module in the half-bridge switch circuit (III), and the negative output / Q pin is connected to the negative input end of the half-bridge driver module.

3. The resonant ZVS isolated boost circuit according to claim 2, characterized in that: The half-bridge switch circuit (III) comprises an external second power supply (V2), a half-bridge drive module, and fifth and sixth NMOS transistors (M5, M6); the drain of the fifth NMOS transistor (M5) is connected to the external second power supply (V2), the gate is connected to the positive output of the half-bridge drive module, the source is connected to the drain of the sixth NMOS transistor (M6), the gate of the sixth NMOS transistor (M6) is connected to the negative output of the half-bridge drive module, and the drain is grounded.

4. The control method of the resonant ZVS isolated boost circuit according to any one of claims 1 to 3, characterized in that: The specific process is as follows: Since the transformer resonance peak voltage of the improved Royer resonance and transformer rectification circuit (I) is positively correlated with the current source current equivalent to the fourth inductor (L4), in order to stabilize the output voltage of the improved Royer resonance and transformer rectification circuit (I), the current hysteresis mode control circuit (II) and the half-bridge switch circuit (III) need to effectively control the average current of the fourth inductor (L4). For the improved Royer resonance and transformer rectification circuit (I), the current flows into one side of the fourth inductor (L4) and flows out from the ground terminals of the first and second NMOS transistors (M1, M2). Therefore, the current detection resistor (R s ), the voltage across it is amplified by the current-sense amplifier (CsAmp) and then enters the high-side and low-side comparators (CmpH, CmpL) to be compared with the two current threshold signals from the feedback control module and the high-side and low-side comparators (CmpH, CmpL) in the current hysteresis mode control circuit (II); when the current-sense signal output by the current-sense amplifier (CsAmp) reaches the current upper limit set by the feedback control module and the high-side and low-side comparators (CmpH, CmpL), the high-side comparator (CmpH) outputs a low level to the R pin of the RS latch (U1), and the RS latch (U1) is reset, so that the half-bridge switch circuit (III) The half-bridge driving module controls the fifth NMOS tube (M5) to turn off and the sixth NMOS tube (M6) to turn on, at which time the current of the fourth inductor (L4) decreases; when the current detection signal output by the current detection amplifier (CsAmp) reaches the current lower limit set by the feedback control module and the high-end and low-end comparators (CmpH, CmpL), the low-end comparator (CmpL) outputs a low level to the S terminal of the RS latch (U1), and the RS latch (U1) is set, so that the half-bridge driving module in the half-bridge switch circuit (III) controls the fifth NMOS tube (M5) to turn on and the sixth NMOS tube (M6) to turn off, at which time the current of the fourth inductor (L4) increases; The above process is repeated continuously to maintain the current of the fourth inductor (L4) between the upper and lower current limits set by the feedback control module and the high and low side comparators (CmpH, CmpL).

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