A synchronous rectification drive modulation circuit for RSCC and method thereof

Abstract

A synchronous rectification drive modulation circuit for RSCC and a method thereof, relate to the field of power electronics. In the circuit, the instrument amplifier is used to receive the resonant inductance L r of the resonant switched capacitor converter Lr_m , amplify the voltage at both ends and output v Lr_m ; the high-speed operational amplifier integration circuit is used to receive the v Lr_m , perform inverse integration operation, and obtain i Lr_m ; the inverse integration circuit outputs the calculated value of the inductor current, and sends the i Lr_m to the high-speed comparator; the high-speed comparator is used to compare the received i Lr_m with V TH+ and V TH‑ respectively, and obtain the drive signals v gs3 and v gs4 of the low-side synchronous rectification half-bridge switch S3 and S4 respectively. The problem of premature turn-off of the rectifier tube when using the traditional drain-source voltage detection method to control the IC to realize synchronous rectification in RSCC is solved.

Description

Technical Field

[0001] This invention relates specifically to the field of power electronics, and in particular to a synchronous rectification drive modulation circuit and method for RSCC. Background Technology

[0002] To improve power density and reduce losses in data center power architectures, 48V DC buses are gradually becoming the mainstream solution. Resonant switched capacitor converters (RSCCs) are characterized by high efficiency, high power density, and low EMI, making them ideal for use as 48-12V converters in 48V architectures. Gallium nitride (GaN) power switching devices are characterized by low switching losses, making them suitable for high-frequency, high-power-density power electronic converters, but they also suffer from a significant reverse conduction voltage drop. This drawback is particularly pronounced when used as rectifier diodes. To mitigate this drawback and improve converter efficiency, precise modulation methods are required for the drive signals of synchronous rectifier diodes.

[0003] Traditional synchronous rectification technology (using fully controlled switching devices to rectify AC current into DC current) can be divided into two categories: resonant current detection and drain-source voltage detection. The former, resonant current detection, uses a current sensor in the resonant circuit to detect the zero-crossing moment of the resonant current, but this method requires a bulky current transformer, leading to additional core losses. Furthermore, while using a surface-mount Hall current sensor to detect the zero-crossing point of the resonant current avoids the use of a current transformer, it requires a large chip area due to the Hall effect, hindering integration. The latter, drain-source voltage detection, uses MOSFET drain-source voltage detection technology, avoiding complex current sensors and auxiliary circuits, significantly improving the converter's power density without additional power loss. However, because GaN devices have very low on-resistance, the detection threshold for GaN device drain-source voltage is very low. However, the parasitic inductance of GaN devices and the PCB generates a large induced voltage during switching, which is transmitted to other GaN devices through the circuit. This causes the drain-source voltage to be superimposed with the induced voltage, resulting in false turn-on / turn-off of the drain-source voltage detection method. This problem is particularly serious for RSCCs operating at high switching frequencies.

[0004] like Figure 1 The diagram shows the topology of a 2:1 step-down RSCC and its two operating modes. Figure 2 For use V DS Synchronous rectification is achieved by using a detection method to control the IC, where v gs1 and v gs3 These are the drive signals for switching transistors S1 and S3, respectively, and iLr is the resonant inductor current. SD3This represents the current flowing from the source to the drain in S3. Due to the parasitic inductance, when S1 in operating mode 2 is turned off, V3... DS There is a significant rise in voltage, exceeding the preset turn-off threshold voltage, although at this time i Lr Although it did not cross zero, S3 still prematurely and erroneously turned off. The current in the red area continued to flow through S3 in reverse, resulting in extremely high losses and failing to achieve synchronous rectification. Figure 3 For using traditional V DS A schematic diagram of a complete working cycle of a 2:1 step-down RSCC when synchronous rectification is achieved using the detection method, where v gs2 and v gs4 By examining the drive signals for switches S2 and S4, we can observe that rectifier diodes S3 and S4 exhibit varying degrees of premature turn-off. This phenomenon leads to reduced converter efficiency and, in severe cases, even thermal breakdown of the rectifier diodes, resulting in significant instability.

[0005] Figure 4 To use V DS The waveform diagram of the 2:1 buck RSCC experiment using the detection method for the synchronous rectifier controller shows that one channel is driven by the S3 signal v. gs3 The three channels are S4 drive signals v gs4 The four channels are resonant current i Lr It is not difficult to see that due to the large di / dt effect, S3 exhibits premature turn-off. At this time, the current of the S3 switch conducts in reverse, and the reverse conduction voltage drop of the S3 switch is large, causing the S3 switch to heat up severely and making it very prone to thermal breakdown.

[0006] Therefore, when using the traditional drain-source voltage detection method to control semiconductor devices (ICs) for synchronous rectification in RSCC, there is a problem of premature turn-off of the rectifier diodes. This problem is mainly caused by the drain-source voltage of the GaN device. V DS This is caused by parasitic inductance in the detection circuit. Because GaN devices switch extremely fast, there is a large di / dt when they are turned off. The rapidly changing current will generate a non-negligible voltage drop across the parasitic inductance, which is captured by the drain-source voltage detection circuit, thus affecting the correct turn-off of the rectifier drive signal.

[0007] Therefore, how to solve the problem of premature turn-off of rectifier tubes when using traditional drain-source voltage detection method to control ICs for synchronous rectification in RSCC, and the resulting problem of overheating and breakdown of switching transistors, is an urgent problem to be solved. Summary of the Invention

[0008] This invention aims to solve the problems of premature turn-off of rectifier diodes and resulting overheating and breakdown of switching transistors when using traditional drain-source voltage detection method to control ICs for synchronous rectification in RSCC. It provides a synchronous rectification drive modulation circuit and method for RSCC.

[0009] The technical solution adopted in this invention is:

[0010] A synchronous rectification drive modulation circuit for a resonant switched capacitor converter, the circuit being used in the resonant switched capacitor converter, the resonant switched capacitor converter including a voltage V in The high-side half-bridge switches S1 and S2, the low-side synchronous rectifier half-bridge switches S3 and S4, and the parasitic inductance L of the switches. S1 ~L S4 Resonant inductor L r and resonant capacitor C r ;

[0011] The circuit includes an instrumentation amplifier, a high-speed operational amplifier integrating circuit, and a high-speed comparator;

[0012] The instrumentation amplifier is used to receive the resonant inductance L in the resonant switched capacitor converter. r The voltage across the terminals, i.e., v L+ Resonant inductor L r The positive terminal voltage and v L -Resonant inductor L r The negative terminal voltage, and the received v L+ and v L - After differential amplification, the output v Lr_m Inverting inductor voltage, and v Lr_m The signal is sent to the high-speed operational amplifier integrating circuit;

[0013] The high-speed operational amplifier integrator circuit is used to integrate the received v Lr_m After performing inverse integration, i is obtained Lr_m The inductor current calculated from the output of the inverting integrator circuit, and the i Lr_m The signal is sent to the high-speed comparator.

[0014] The high-speed comparator is used for receiving i Lr_m respectively with V TH+ and V TH - After comparison, the corresponding drive signals v of the low-side synchronous rectifier half-bridge switches S3 and S4 are obtained. gs3 and v gs4 ;where V TH- and V TH+ It is the turn-on threshold voltage of the low-side synchronous rectifier half-bridge switches S4 and S3 in the resonant switched capacitor converter.

[0015] Preferably, the instrumentation amplifier includes two resistor networks (1) and a first amplifier (2), the two resistor networks being used to receive the resonant inductance L in the resonant switched capacitor converter. r The voltage across the terminals, i.e., v L+ Resonant inductor L r The positive terminal voltage and v L- Resonant inductor L r The negative terminal voltage is divided by a resistor divider network and then sent to amplifier (2) for differential amplification, resulting in the output voltage V. Lr_m Inverting inductor voltage.

[0016] Preferably, the high-speed operational amplifier integrating circuit includes resistor R1, resistor R2, capacitor C1, resistor R4 and amplifier 2 (3); one end of resistor R1 is grounded and the other end is connected to the positive input terminal of amplifier 2 (3); one end of resistor R2 is connected to the output terminal of amplifier 1 (2) in the instrumentation amplifier, and the other end is connected to the negative input terminal of amplifier 2 (3), one end of capacitor C1 and one end of resistor R4; the output terminal of amplifier 2 (3) is connected to the other end of capacitor C1 and the other end of resistor R4.

[0017] Preferably, the high-speed operational amplifier integrating circuit includes resistors R6, R2, and R3, capacitors C1 and C2, resistor R4, and a second amplifier (3); one end of resistor R2 is connected to the V in the resonant switched capacitor converter. L+ Resonant inductor L r The positive terminal voltage, the other end of resistor R2 is simultaneously connected to the negative input terminal of amplifier (3), one end of capacitor C1 and one end of resistor R4, the output terminal of amplifier (3) is simultaneously connected to the other end of capacitor C1 and the other end of resistor R4; one end of resistor R6 is connected to the V in the resonant switched capacitor converter. L- Resonant inductor L r The negative terminal voltage of the resistor R6 is connected to one end of the capacitor C2, one end of the resistor R3 and the positive input terminal of the second amplifier (3), and the other end of the capacitor C2 and the other end of the resistor R3 are grounded.

[0018] Preferably, the high-speed comparator includes a third amplifier (4) and a fourth amplifier (5); the negative input terminal of the third amplifier (4) is connected to the positive input terminal of the fourth amplifier (5); the positive input terminal of the third amplifier (4) is connected to the on-threshold voltage V of the low-side synchronous rectifier half-bridge switch S4 in the resonant switched capacitor converter. TH- The negative input terminal of amplifier 4 (5) is connected to the on-threshold voltage V of the low-side synchronous rectifier half-bridge switch S3 in the resonant switched capacitor converter. TH+Amplifier 3 (4) outputs the drive signal v of the low-side synchronous rectifier half-bridge switch S4 in the resonant switched capacitor converter. gs4 Amplifier 4 (5) outputs the drive signal v of the low-side synchronous rectifier half-bridge switch S3 in the resonant switched capacitor converter. gs3 .

[0019] A modulation method based on a synchronous rectification drive modulation circuit for a resonant switched capacitor converter, the method comprising:

[0020] For receiving the resonant inductor L in the resonant switched capacitor converter r The voltage across the terminals, i.e., v L+ Resonant inductor L r The positive terminal voltage and v L- Resonant inductor L r The negative terminal voltage, and the received v L+ and v L- After differential amplification, the output v Lr_m Inverting inductor voltage, and v Lr_m The method of sending the signal to the high-speed operational amplifier integrating circuit;

[0021] For receiving the v Lr_m After performing inverse integration, i is obtained Lr_m The inductor current calculated from the output of the inverting integrator circuit, and the i Lr_m The method of sending to the high-speed comparator;

[0022] Used for receiving i Lr_m respectively with V TH+ and V TH- After comparison, the corresponding drive signals v of the low-side synchronous rectifier half-bridge switches S3 and S4 are obtained. gs3 and v gs4 Among them, V TH- and V TH+ It is the turn-on threshold voltage of the low-side synchronous rectifier half-bridge switches S4 and S3 in the resonant switched capacitor converter.

[0023] A modulation method based on a synchronous rectification drive modulation circuit for a resonant switched capacitor converter includes the following steps:

[0024] Step 1: Resonant inductor L r Voltage v across the terminals L+ and v L- The voltage is divided by two resistor voltage divider networks and then fed into the first amplifier (2) of the instrumentation amplifier for differential calculation. The differential calculation eliminates the voltage difference. L+ and v L- The common-mode voltage;

[0025] Step 2: The output voltage of the instrument amplifier is shown in equation (1):

[0026] v L+ : Resonant inductance L r The positive terminal voltage;

[0027] v L- : Resonant inductance L r The negative terminal voltage;

[0028] v Lr : Resonant inductance L r The voltage across the two ends;

[0029] K res Gain of the resistor divider network;

[0030] K ina Voltage gain of the instrumentation amplifier;

[0031] v Lr_m =K res K ina (v L+ -v L- ) = K res K ina v Lr (1)

[0032] Step 3:

[0033] The resonant inductor Lr and the resonant capacitor Cr are connected in series and carry the same current i. Lr That is, the inductor current output by the inverting integrator circuit;

[0034] The differential equations for the voltage and current of the resonant inductor Lr are v Lr (t)=L r di Lr Integrating both sides of (t) / dt, under the condition that the initial inductor current is 0, we can obtain the integral relationship between the inductor current and the inductor voltage (2).

[0035]

[0036] In order to utilize the above integral relationship, the high-speed operational amplifier integrator circuit performs the integration operation function of equation (3), where v in (t) represents the input voltage of the integrating circuit, v out (t) represents the output voltage of the integrator circuit;

[0037]

[0038] Specifically, the measured value v of the resonant inductor voltage output by the instrumentation amplifier is... Lr_m(t) is the input voltage v in equation (3). in (t), and correspondingly, the output value of the integral operation in equation (3) can be calculated using the inductor current i. Lr_m (t) represents the expression, which gives equation (4);

[0039]

[0040] From equation (1) v Lr_m (t)=K res K ina v Lr (t), in equation (3) Substituting it into equation (4), we get equation (5);

[0041] R2C1: Integral time constant;

[0042] v Lr_m (t): Amplifier output voltage;

[0043] K res :Gain of the resistor divider network;

[0044] K ina Voltage gain of the instrumentation amplifier;

[0045] K int Voltage gain of the integrating circuit;

[0046]

[0047] Arrange equation (2) to obtain Substituting into equation (5) can be further transformed into equation (6), which illustrates the linear proportional relationship between the calculated inductor current and the actual inductor current.

[0048] i Lr_m (t)=K res K ina K int L r i Lr (t) (6)

[0049] Step 4: In the high-speed comparator, i Lr_m (t) and the set threshold voltage V TH- and V TH+ Compare;

[0050] Step 5: If i Lr_m (t) is greater than V TH+ This indicates that the inductor current has changed from negative to positive, and S3 is turned on; if i Lr_m (t) is less than V TH- Then the inductor current has changed from positive to negative, and S4 is turned on.

[0051] Beneficial effects: The technology of this invention belongs to the drive signal modulation technology of fully controllable switching devices for synchronous rectification. It is applied to resonant converters containing half-bridge synchronous rectification structures, such as resonant switched capacitor converters (RSCC). It can solve the problem of premature turn-off of rectifier tubes in traditional drain-source voltage detection type synchronous rectification drive modulation, improve the efficiency and stability of the converter, and support faster switching devices (such as GaN and SiC), thereby increasing the switching frequency and power density of the converter. Moreover, the modulation circuit proposed in this invention is designed based on the volt-second balance law of inductors, and can be used in converters that rectify the resonant inductor current, making it highly versatile. Attached Figure Description

[0052] Figure 1 This is a schematic diagram of the topology and two operating modes of a 2:1 step-down RSCC;

[0053] (a) represents mode 1, i.e., the main charging mode of the resonant capacitor;

[0054] (b) represents mode 2, i.e., the secondary charging mode of the resonant capacitor;

[0055] Figure 2 yes Figure 1 A schematic diagram of the early turn-off waveform of S3 in mode 2;

[0056] Figure 3 Is using traditional V DS Schematic diagram of the waveform indicating early shutdown of the rectifier tube using the detection method;

[0057] Figure 4 Is using traditional V DS Schematic diagram of the 2:1 step-down RSCC experimental waveform of the detection method;

[0058] Figure 5 This is a schematic diagram of a synchronous rectification drive modulation circuit for RSCC; it can also be called a 2:1 buck RSCC with parasitic inductance and a synchronous rectification drive signal modulation circuit with resonant inductor voltage integration.

[0059] Figure 6 This is a schematic diagram of a synchronous rectification drive signal modulation circuit without an instrumentation amplifier in a synchronous rectification drive modulation circuit for RSCC.

[0060] Figure 7 This is a schematic diagram of a typical working waveform of a 2:1 buck RSCC synchronous rectifier under heavy load;

[0061] Figure 8 This is a schematic diagram of a typical working waveform of a 2:1 buck RSCC synchronous rectifier under light load.

[0062] Figure 9This is an experimental schematic diagram of a synchronous rectification drive modulation circuit for RSCC proposed in this invention applied to a 2:1 buck RSCC. Detailed Implementation

[0063] Terminology Explanation:

[0064] Synchronous rectification: Uses fully controlled switching devices to rectify AC current into DC current; RSCC: Resonant switched capacitor converter; GaN: Gallium nitride power switching device; V DS : Drain-source voltage of GaN device; V DS Detection: Drain-Source Voltage Detection Technology

[0065] Detailed Implementation Method 1, Refer to Figures 5 to 9 This embodiment describes a synchronous rectification drive modulation circuit for RSCC and a synchronous rectification drive modulation circuit for a resonant switched capacitor converter. The circuit is used in a resonant switched capacitor converter, which includes an input voltage V. in The high-side half-bridge switches S1 and S2, the low-side synchronous rectifier half-bridge switches S3 and S4, and the parasitic inductance L of the switches. S1 ~L S4 Resonant inductor L r and resonant capacitor C r ;

[0066] The circuit includes an instrumentation amplifier, a high-speed operational amplifier integrating circuit, and a high-speed comparator;

[0067] The instrumentation amplifier is used to receive the resonant inductance L in the resonant switched capacitor converter. r The voltage across the terminals, i.e., v L+ Resonant inductor L r The positive terminal voltage and v L- Resonant inductor L r The negative terminal voltage, and the received v L+ and v L - After differential amplification, the output v Lr_m Inverting inductor voltage, and v Lr_m The signal is sent to the high-speed operational amplifier integrating circuit;

[0068] The high-speed operational amplifier integrator circuit is used to integrate the received v Lr_m After performing inverse integration, i is obtained Lr_m The inductor current calculated from the output of the inverting integrator circuit, and the i Lr_m The signal is sent to the high-speed comparator.

[0069] The high-speed comparator is used to compare the received i Lr_m respectively with V TH+ and VTH - After comparison, the corresponding drive signals v of the low-side synchronous rectifier half-bridge switches S3 and S4 are obtained. gs3 and v gs4 Among them, V TH- and V TH+ It is the turn-on threshold voltage of the low-side synchronous rectifier half-bridge switches S4 and S3 in the resonant switched capacitor converter.

[0070] Specific Implementation Method Two: This implementation method is a further description of the synchronous rectification drive modulation circuit for a resonant switched capacitor converter described in Implementation Method One. The instrumentation amplifier includes two resistor networks (1) and a first amplifier (2). The two resistor networks are used to receive the resonant inductance L in the resonant switched capacitor converter. r The voltage across the terminals, i.e., v L+ Resonant inductor L r The positive terminal voltage and v L- Resonant inductor L r The negative terminal voltage is divided by a resistor divider network and then sent to amplifier (2) for differential amplification, resulting in the output voltage V. Lr_m Inverting inductor voltage.

[0071] Specific Implementation Method 3: This implementation method is a further description of the synchronous rectification drive modulation circuit for a resonant switched capacitor converter described in Implementation Method 1. The high-speed operational amplifier integrating circuit includes resistor R1, resistor R2, capacitor C1, resistor R4, and amplifier number 2 (3). One end of resistor R1 is grounded, and the other end is connected to the positive input terminal of amplifier number 2 (3). One end of resistor R2 is connected to the output terminal of amplifier number 1 (2) in the instrumentation amplifier, and the other end is simultaneously connected to the negative input terminal of amplifier number 2 (3), one end of capacitor C1, and one end of resistor R4. The output terminal of amplifier number 2 (3) is simultaneously connected to the other end of capacitor C1 and the other end of resistor R4.

[0072] Specific Implementation Method Four: This implementation method is a further description of the synchronous rectification drive modulation circuit for a resonant switched capacitor converter described in Implementation Method One. The high-speed operational amplifier integrating circuit includes resistors R6, R2, and R3, capacitors C1 and C2, resistor R4, and amplifier number two (3); one end of resistor R2 is connected to the V in the resonant switched capacitor converter. L+ Resonant inductor L r The positive terminal voltage, the other end of resistor R2 is simultaneously connected to the negative input terminal of amplifier (3), one end of capacitor C1 and one end of resistor R4, the output terminal of amplifier (3) is simultaneously connected to the other end of capacitor C1 and the other end of resistor R4; one end of resistor R6 is connected to the V in the resonant switched capacitor converter. L- Resonant inductor Lr The negative terminal voltage of the resistor R6 is connected to one end of the capacitor C2, one end of the resistor R3 and the positive input terminal of the second amplifier (3), and the other end of the capacitor C2 and the other end of the resistor R3 are grounded.

[0073] Specific Implementation Method 5: This implementation method is a further description of the synchronous rectification drive modulation circuit for a resonant switched capacitor converter described in Implementation Method 1. The high-speed comparator includes a third amplifier (4) and a fourth amplifier (5); the negative input terminal of the third amplifier (4) is connected to the positive input terminal of the fourth amplifier (5); the positive input terminal of the third amplifier (4) is connected to the on-threshold voltage V of the low-side synchronous rectifier half-bridge switch S4 in the resonant switched capacitor converter. TH- The negative input terminal of amplifier 4 (5) is connected to the on-threshold voltage V of the low-side synchronous rectifier half-bridge switch S3 in the resonant switched capacitor converter. TH+ Amplifier 3 (4) outputs the drive signal v of the low-side synchronous rectifier half-bridge switch S4 in the resonant switched capacitor converter. gs4 Amplifier 4 (5) outputs the drive signal v of the low-side synchronous rectifier half-bridge switch S3 in the resonant switched capacitor converter. gs3 ...

[0074] Specific Implementation Method Six: A modulation method for a synchronous rectification drive modulation circuit of a resonant switched capacitor converter, based on Implementation Method One, comprising:

[0075] For receiving the resonant inductor L in the resonant switched capacitor converter r The voltage across the terminals, i.e., v L+ Resonant inductor L r The positive terminal voltage and v L- Resonant inductor L r The negative terminal voltage, and the received v L+ and v L- After amplification, the output v Lr_m Inverting inductor voltage, and v Lr_m The method of sending the signal to the high-speed operational amplifier integrating circuit;

[0076] For receiving the v Lr_m After performing inverse integration, i is obtained Lr_m The inductor current calculated from the output of the inverting integrator circuit, and the i Lr_m The method of sending to the high-speed comparator;

[0077] Used for receiving i Lr_m respectively with V TH- and V TH+After comparison, the corresponding drive signals v of the low-side synchronous rectifier half-bridge switches S4 and S3 are obtained. gs4 and v gs3 The method; where V TH- and V TH+ It is the turn-on threshold voltage of the low-side synchronous rectifier half-bridge switches S4 and S3 in the resonant switched capacitor converter.

[0078] Specific Implementation Method Seven: A modulation method for a synchronous rectification drive modulation circuit of a resonant switched capacitor converter, based on Implementation Methods One, Two, Three, Four, or Five, comprising the following steps:

[0079] Step 1: Resonant inductor L r Voltage v across the terminals L+ and v L- The voltage is divided by two resistor voltage divider networks and then fed into the first amplifier (2) of the instrumentation amplifier for differential calculation. The differential calculation eliminates the voltage difference. L+ and v L- The common-mode voltage;

[0080] Step 2: The output voltage of the instrument amplifier is shown in equation (1):

[0081] v L+ : Resonant inductance L r The positive terminal voltage;

[0082] v L- : Resonant inductance L r The negative terminal voltage;

[0083] v Lr : Resonant inductance L r The voltage across the two ends;

[0084] K res Gain of the resistor divider network;

[0085] K ina Voltage gain of the instrumentation amplifier;

[0086] v Lr_m =K res K ina (v L+ -v L- ) = K res K ina v Lr (1)

[0087] Step 3:

[0088] The resonant inductor Lr and the resonant capacitor Cr are connected in series and carry the same current i. Lr That is, the inductor current output by the inverting integrator circuit;

[0089] The differential equations for the voltage and current of the resonant inductor Lr are v Lr (t)=L r di Lr Integrating both sides of (t) / dt, under the condition that the initial inductor current is 0, we can obtain the integral relationship between the inductor current and the inductor voltage (2).

[0090]

[0091] In order to utilize the above integral relationship, the high-speed operational amplifier integrator circuit performs the integration operation function of equation (3), where v in (t) represents the input voltage of the integrating circuit, v out (t) represents the output voltage of the integrator circuit;

[0092]

[0093] Specifically, the measured value v of the resonant inductor voltage output by the instrumentation amplifier is... Lr_m (t) is the input voltage v in equation (3). in (t), and correspondingly, the output value of the integral operation in equation (3) can be calculated using the inductor current i. Lr_m (t) represents the expression, which gives equation (4);

[0094]

[0095] From equation (1) v Lr_m (t)=K res K ina v Lr (t), in equation (3) Substituting it into equation (4), we get equation (5);

[0096] R2C1: Integral time constant;

[0097] v Lr_m (t): Amplifier output voltage;

[0098] K res :Gain of the resistor divider network;

[0099] K ina Voltage gain of the instrumentation amplifier;

[0100] K int Voltage gain of the integrating circuit;

[0101]

[0102] Arrange equation (2) to obtain Substituting into equation (5) can be further transformed into equation (6), which illustrates the linear proportional relationship between the calculated inductor current and the actual inductor current.

[0103] i Lr_m (t)=K res K ina K int L r i Lr (t) (6)

[0104] Step 4: In the high-speed comparator, i Lr_m (t) and the set threshold voltage V TH- and V TH+ Compare;

[0105] Step 5: If i Lr_m (t) is greater than V TH+ This indicates that the inductor current has changed from negative to positive, and S3 is turned on; if i Lr_m (t) is less than V TH - Then the inductor current has changed from positive to negative, and S4 is turned on.

[0106] This method demonstrates that the synchronous rectification drive modulation circuit described in this invention can solve the problem of premature turn-off of the rectifier tube when using the traditional drain-source voltage detection method to control the IC for synchronous rectification in RSCC, and indirectly solves the problem of overheating and breakdown of the switching tube caused by this, with significant effect.

[0107] 1. This patent introduces a novel synchronous rectification drive modulation circuit that utilizes the volt-second balance principle of a resonant inductor to obtain the resonant current waveform. When the converter is in steady state, the inductor exhibits volt-second balance characteristics: the voltage across the inductor integrates over one switching cycle, and the result is zero. Using this characteristic, the waveform of the inductor current in each switching cycle can be estimated, and the estimated inductor current waveform i Lr_m (t) Since there is no DC bias, the zero-crossing time of the inductor current can be accurately determined. Therefore, the synchronous rectification drive modulation circuit proposed in this patent can achieve accurate synchronous rectification of the resonant converter and has the characteristic of adaptive dead time of the rectifier tube.

[0108] A 2:1 buck RSCC with synchronous rectified GaN transistors and parasitic inductance, such as Figure 5 As shown. S1 and S2 are the high-side half-bridge switches, and S3 and S4 are the low-side synchronous rectifier half-bridge switches. L S1 ~L S4 L is the parasitic inductance of the switching transistor. r With C r These are the resonant inductor and resonant capacitor.

[0109] The synchronous rectification drive modulation circuit proposed in this patent mainly consists of an instrumentation amplifier, a high-speed operational amplifier integrator circuit, and a high-speed comparator. Among them, v L+ It is the positive terminal voltage of the inductor, v L- It is the voltage across the negative terminal of the inductor. Lr_m This is the inverting inductor voltage output by the instrumentation amplifier. Lr_m It is the "inductor current" output by the inverting integrator circuit, which is proportional to the actual inductor current i. Lr V TH- and V TH+ It is the rectifier diode's on-threshold current, v gs3 and v gs4 These are the drive signals for rectifier diodes S3 and S4.

[0110] The instrumentation amplifier included in the synchronous rectification drive modulation circuit proposed in this patent is used to increase the input impedance of the detection circuit. If a high-speed operational amplifier with a higher input impedance is selected as the subsequent stage, the instrumentation amplifier can be omitted. The corresponding circuit structure diagram is shown below. Figure 6 As shown.

[0111] In non-isolated resonant converters like RSCC, the inverting integrator circuit constructed using an operational amplifier can obtain information about the zero-crossing of the inductor current. The inductor current reference waveform i estimated by the method of this invention... Lr_m (t), as shown in equations (5) and (6). Equation (6) represents the overall gain of this synchronous rectification drive modulation circuit. And i Lr_m (t) and the actual inductor current i Lr (t) have the same shape.

[0112] Invention effects:

[0113] like Figure 7 As shown, when the proposed synchronous rectification drive modulation circuit with a 2:1 step-down RSCC operates under heavy load current, its resonant inductor current is continuous. The drive signals of rectifier diodes S3 and S4 are delayed compared to S1 and S2, where t d This refers to the dead time of rectifier diodes S3 and S4.

[0114] like Figure 8 As shown, when the RSCC circuit operates under a light load current, the inductor current may be discontinuous, where td is the dead time of rectifier diodes S3 and S4. When the rectifier diodes are not conducting, their parasitic capacitance participates in resonance, and a resonant current will exist in the resonant circuit. The proposed synchronous rectification drive modulation circuit allows setting a current threshold voltage (V). TH+ and V TH- This can prevent the rectifier from turning on incorrectly due to resonant current, thus improving the stability and efficiency of the circuit.

[0115] 3. Variable dead time is achieved through a current threshold. The synchronous rectification drive modulation circuit proposed in this patent processes the resonant inductor current and the current threshold voltage (V). TH+ and V TH- The output signal is obtained by comparison. For fixed current threshold voltages VTH+ and VTH-, the peak resonant current under heavy load is greater than that under light load, and the rate of change of the resonant current at zero crossing is also greater. The value of the resonant current can exceed the set conduction threshold voltage more quickly, and the dead time t... d The dead time is also correspondingly shorter. Since GaN has a large reverse conduction voltage drop, shortening the dead time can significantly reduce the reverse conduction loss of GaN devices and improve the power conversion efficiency of the converter.

[0116] like Figure 9 As shown, using the synchronous rectification scheme proposed in this patent in a 2:1 step-down RSCC can achieve precise turn-on and turn-off of the rectifier tube, which is superior to the traditional V... DS Synchronous rectification using detection method. Channels 1 and 2 are driven by S1 and S2 signals v. gs1 v gs2 Channels 3 and 4 are the "inductor current waveforms" i′ output by the integrating circuit. Lr The actual inductor current waveform iLr, and channels 5 and 6 are the drive signals v for rectifier diodes S3 and S4. gs3 v gs4 .

[0117] Depending on the cost and operating frequency, practical applications can be divided into... Figure 5 , Figure 6 Choose either of the two options. Figure 5 Differential operations are performed using an instrumentation amplifier, and integration operations are then performed using a high-speed operational amplifier. Figure 6 Differential and integral operations can be performed simultaneously using only one high-speed operational amplifier.

[0118] In practical applications, the voltage of the resonant inductor is relatively high. Therefore, a resistor network should be used to divide the voltage before connecting it to the instrumentation amplifier. A suitable instrumentation amplifier should be selected (considering bandwidth, slew rate, and gain). The subsequent integrator circuit should use a high-speed operational amplifier with low input bias voltage, and a suitable integration time constant should be calculated to avoid saturation of the integrator circuit. The comparator should be a high-speed comparator with low delay and high bandwidth to reduce drive signal delay.

[0119] The following is a design scheme for a 2:1 buck RSCC with synchronous rectification drive modulation circuit. The specific component selection is shown in Table 1:

[0120] Table 1

[0121]

[0122] This invention has been illustrated through several specific embodiments. Those skilled in the art will understand that various modifications and equivalent substitutions can be made to this invention without departing from its scope. Furthermore, various modifications can be made to this invention for specific situations or circumstances without departing from its scope. Therefore, this invention is not limited to the specific embodiments disclosed, but should include all embodiments falling within the scope of the claims.

Claims

1. A synchronous rectification drive modulation circuit for a resonant switched-capacitor converter, the circuit being used in the resonant switched-capacitor converter, the resonant switched-capacitor converter including an input voltage V. in The high-side half-bridge switches S1 and S2, the low-side synchronous rectifier half-bridge switches S3 and S4, and the parasitic inductance L of the switches. S1 ~L S4 Resonant inductor L r and resonant capacitor C r ; Its features are, The circuit includes an instrumentation amplifier, a high-speed operational amplifier integrating circuit, and a high-speed comparator; The instrumentation amplifier is used to receive the resonant inductance L in the resonant switched capacitor converter. r The voltage across the terminals, i.e., v L+ Resonant inductor L r The positive terminal voltage and v L- Resonant inductor L r The negative terminal voltage, and the received v L+ and v L- After differential amplification, the output v Lr_m Inverting inductor voltage, and v Lr_m The signal is sent to the high-speed operational amplifier integrating circuit; The high-speed operational amplifier integrator circuit is used to integrate the received v Lr_m After performing inverse integration, i is obtained Lr_m The inductor current calculated from the output of the inverting integrator circuit, and the i Lr_m The signal is sent to the high-speed comparator. The high-speed comparator is used to compare the received i Lr_m respectively with V TH+ and V TH- After comparison, the corresponding drive signals v of the low-side synchronous rectifier half-bridge switches S3 and S4 are obtained. gs3 and v gs4 ; Among them, V TH- and V TH+ It is the turn-on threshold voltage of the low-side synchronous rectifier half-bridge switches S4 and S3 in the resonant switched capacitor converter; The instrumentation amplifier includes two resistor networks (1) and a first amplifier (2), the two resistor networks being used to receive the resonant inductance L in the resonant switched capacitor converter. r The voltage across the terminals, i.e., v L+ Resonant inductor L r The positive terminal voltage and v L- Resonant inductor L r The negative terminal voltage is divided by a resistor divider network and then sent to amplifier (2) for differential amplification, outputting v. Lr_m Inverting inductor voltage; The high-speed operational amplifier integrating circuit includes resistor R1, resistor R2, capacitor C1, resistor R4 and amplifier 2 (3); one end of resistor R1 is grounded and the other end is connected to the positive input terminal of amplifier 2 (3); one end of resistor R2 is connected to the output terminal of amplifier 1 (2) in the instrumentation amplifier, and the other end is connected to the negative input terminal of amplifier 2 (3), one end of capacitor C1 and one end of resistor R4; the output terminal of amplifier 2 (3) is connected to the other end of capacitor C1 and the other end of resistor R4.

2. The synchronous rectification drive modulation circuit for a resonant switched capacitor converter according to claim 1, characterized in that, The high-speed operational amplifier integrating circuit includes resistors R6, R2, R3, capacitors C1 and C2, resistor R4, and amplifier number 2 (3); one end of resistor R2 is connected to the V in the resonant switched capacitor converter. L+ Resonant inductor L r The positive terminal voltage, the other end of resistor R2 is simultaneously connected to the negative input terminal of amplifier (3), one end of capacitor C1 and one end of resistor R4, the output terminal of amplifier (3) is simultaneously connected to the other end of capacitor C1 and the other end of resistor R4; one end of resistor R6 is connected to the V in the resonant switched capacitor converter. L- Resonant inductor L r The negative terminal voltage of the resistor R6 is connected to one end of the capacitor C2, one end of the resistor R3 and the positive input terminal of the second amplifier (3), and the other end of the capacitor C2 and the other end of the resistor R3 are grounded.

3. The synchronous rectification drive modulation circuit for a resonant switched capacitor converter according to claim 1, characterized in that, The high-speed comparator includes a third amplifier (4) and a fourth amplifier (5); the negative input terminal of the third amplifier (4) is connected to the positive input terminal of the fourth amplifier (5); the positive input terminal of the third amplifier (4) is connected to the on-threshold voltage V of the low-side synchronous rectifier half-bridge switch S4 in the resonant switched capacitor converter. TH- The negative input terminal of amplifier 4 (5) is connected to the on-threshold voltage V of the low-side synchronous rectifier half-bridge switch S3 in the resonant switched capacitor converter. TH+ Amplifier 3 (4) outputs the drive signal v of the low-side synchronous rectifier half-bridge switch S4 in the resonant switched capacitor converter. gs4 Amplifier 4 (5) outputs the drive signal v of the low-side synchronous rectifier half-bridge switch S3 in the resonant switched capacitor converter. gs3 .

4. A modulation method for a synchronous rectification drive modulation circuit of a resonant switched capacitor converter according to claim 1, characterized in that, The method includes: For receiving the resonant inductor L in the resonant switched capacitor converter r The voltage across the terminals, i.e., v L+ Resonant inductor L r The positive terminal voltage and v L- Resonant inductor L r The negative terminal voltage, and the received v L+ and v L- After differential amplification, the output v Lr_m Inverting inductor voltage, and v Lr_m The method of sending the signal to the high-speed operational amplifier integrating circuit; For receiving the v Lr_m After performing inverse integration, i is obtained Lr_m The inductor current calculated from the output of the inverting integrator circuit, and the i Lr_m The method of sending to the high-speed comparator; Used for receiving i Lr_m respectively with V TH+ and V TH- After comparison, the corresponding drive signals v of the low-side synchronous rectifier half-bridge switches S3 and S4 are obtained. gs3 and v gs4 Among them, V TH- and V TH+ It is the turn-on threshold voltage of the low-side synchronous rectifier half-bridge switches S4 and S3 in the resonant switched capacitor converter.

5. A modulation method for a synchronous rectification drive modulation circuit of a resonant switched capacitor converter according to any one of claims 1 to 4, characterized in that, The method includes the following steps: Step 1: Resonant inductor L r Voltage v across the terminals L+ and v L- The voltage is divided by two resistor voltage divider networks and then fed into the first amplifier (2) of the instrumentation amplifier for differential calculation. The differential calculation eliminates the voltage difference. L+ and v L- The common-mode voltage; Step 2: The output voltage of the instrumentation amplifier is shown in equation (1): v L+ : Resonant inductance L r The positive terminal voltage; v L- : Resonant inductance L r The negative terminal voltage; v Lr : Resonant inductance L r The voltage across the two ends; K res Gain of the resistor divider network; K ina Voltage gain of the instrumentation amplifier; （1） Step 3: The resonant inductor Lr and the resonant capacitor Cr are connected in series and carry the same current i. Lr That is, the inductor current output by the inverting integrator circuit; The differential equations for the voltage and current of the resonant inductor Lr are as follows: Integrating both sides simultaneously, under the condition that the initial inductor current is 0, we can obtain the integral relationship between the inductor current and the inductor voltage (2). （2） In order to utilize the above integral relationship, the high-speed operational amplifier integrator circuit performs the integration operation function of equation (3), where v in (t) represents the input voltage of the integrating circuit, v out (t) represents the output voltage of the integrator circuit; （3） Specifically, the measured value v of the resonant inductor voltage output by the instrumentation amplifier is... Lr_m (t) is the input voltage v in equation (3). in (t), and correspondingly, the output value of the integral operation in equation (3) can be calculated using the inductor current i. Lr_m (t) represents the expression, which gives equation (4); （4） From equation (1) In equation (3) Substituting it into equation (4), we get equation (5); R2C1: Integral time constant; v Lr_m (t): Amplifier output voltage; K res :Gain of the resistor divider network; K ina Voltage gain of the instrumentation amplifier; K int Voltage gain of the integrating circuit; （5） Arrange equation (2) to obtain Substituting into equation (5) can be further transformed into equation (6), which illustrates the linear proportional relationship between the calculated inductor current and the actual inductor current. （6） Step 4: In the high-speed comparator, i Lr_m (t) and the set threshold voltage V TH- and V TH+ Compare; Step 5: If i Lr_m (t) is greater than V TH+ This indicates that the inductor current has changed from negative to positive, and S3 is turned on; if i Lr_m (t) is less than V TH- Then the inductor current has changed from positive to negative, and S4 is turned on.

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