CN203911762U - LLC resonance converting device - Google Patents

Abstract

The utility model discloses an LLC resonant conversion device, which comprises a bridge circuit, a resonant circuit, a transformer, a rectifier circuit and a filter circuit sequentially connected in series; and an input detection circuit, a drive circuit, a peak detection circuit, an output detection circuit and digital processing device. The input detection circuit is connected to the input end of the LLC resonant conversion device to detect the input voltage and send it to the digital processor; the driving circuit is connected to the digital processor to convert the PWM signal into a driving level to drive the bridge circuit; the peak detection circuit is connected to the resonance The circuit detects the peak value of the resonant current and sends it to the digital processor; the output detection circuit detects the output voltage and the output current, and sends it to the digital processor. The utility model realizes input undervoltage protection by adding an input detection circuit, and effectively improves the reliability of the LLC resonant conversion device during operation; the peak detection circuit can quickly respond to the peak value of the resonant current, and can directly realize the overcurrent protection of the resonant current. It adopts digital control, which has the advantages of simple operation and flexible control. The utility model is suitable for the application occasions with high power and wide output range.

Description

A kind of LLC resonant conversion device

technical field

The utility model belongs to the field of DC/DC converters, and more specifically relates to an LLC resonant conversion device.

Background technique

High efficiency, high power density, and high reliability have always been the development trend of switching converters. At present, resonant soft switching technology has been widely used in switching converters to improve converter efficiency and power density. The LLC resonant converter works above the resonant frequency, which can realize the zero-voltage conduction of the input bridge switch tube, and can also realize the zero-current shutdown of the output rectifier diode within a certain load range, so it has high efficiency, small size, electromagnetic Good compatibility and other advantages have attracted widespread attention in recent years.

Unlike general converters, LLC resonant converters use pulse frequency modulation (Pulse Frequency Modulation, PFM), a wide operating frequency range, and a duty cycle that is always maintained at 50%. The switching frequency is adjusted in a closed loop to maintain a stable output voltage. It has the advantages of wide output range, high adjustment accuracy, and fast dynamic response. It is suitable for applications with high power and wide output range.

However, the reliability of the LLC resonant converter, especially in the closed-loop operation process, needs to be further resolved. The dynamics of the resonant circuit of the LLC resonant converter is very fast, while the output dynamics are relatively slow. During the closed-loop control process, if the input voltage drops severely, the switching frequency of the closed-loop control will rise rapidly to the lowest frequency. At this time, the output dynamics are too late to respond, which will easily lead to Overcurrent occurs in the resonant circuit, which will damage the switch tube and other circuit components in severe cases; in addition, in the process of closed-loop adjustment, if the switching frequency is adjusted too fast, it is easy to cause overcurrent in the resonant circuit. The existing technical solution only judges the fault by detecting the output voltage and output current, the response is slow, and effective protection cannot be realized; the average value of the resonant current is used for sampling and protection, because the average value needs to be added to the filter link, and the filter delay is long, so it cannot Timely protection, and the relationship between the average value and peak value of the resonant current changes with the change of the operating point, it is not easy to determine the protection value.

Utility model content

In view of the above defects or improvement needs of the prior art, the utility model provides an LLC resonant conversion device, which effectively improves the reliability of the LLC resonant conversion device in the closed-loop operation process.

The invention provides an LLC resonant conversion device, which includes a bridge circuit, a resonant circuit, a transformer, a rectifier circuit and a filter circuit connected in series; it also includes an input detection circuit, a drive circuit, a peak detection circuit, an output detection circuit and digital processing device; the input end of the input detection circuit is connected to the input end of the bridge circuit, and the output end of the input detection circuit is connected to the first input end of the digital processor; the input end of the peak detection circuit It is connected with the connection end of the resonant circuit and the transformer, the output end of the peak detection circuit is connected with the second input end of the digital processor; the input end of the output detection circuit is connected with the output of the filter circuit The output terminal of the output detection circuit is connected with the third input terminal of the digital processor; the input terminal of the driving circuit is connected with the output terminal of the digital processor, and the output terminal of the driving circuit is connected with the output terminal of the digital processor. The control terminal of the bridge circuit is connected.

Wherein, the input detection circuit includes a first differential amplifier circuit, a first voltage follower and a first RC filter connected in series; and a first sampling unit, a filter capacitor C _ins and a filter capacitor C ₅ ; the filter capacitor C ₅ is connected between the non-inverting input terminal of A1 in the first differential amplifier circuit and the ground; the filter capacitor C _ins is connected between the output terminal of the first sampling unit and the ground, and the first sampling unit The input terminal of the first RC filter is used as the input terminal of the input detection circuit; the output terminal of the first RC filter is used as the output terminal of the input detection circuit.

Wherein, the first sampling unit includes a first voltage Hall device H1, a resistor R ₀ and a sampling resistor R _ins ; the voltage input terminal V+ of the first voltage Hall device H1 is connected to the LLC resonance conversion through a resistor R ₀ The positive pole of the device input, the negative pole of the voltage input terminal V- of the first voltage Hall device H1 is connected to the negative pole of the input of the resonant conversion device, and the output terminal of the first voltage Hall device H1 is used as the output terminal of the first sampling unit , the output end of the first voltage Hall device H1 is also grounded through the sampling resistor R _ins .

Wherein, the first differential amplifier circuit includes a resistor R ₁ , a resistor R ₂ , a resistor R ₃ , a resistor R ₄ and an operational amplifier A1; the non-inverting input terminal of the operational amplifier _A1 is connected to the The output terminal of the first sampling unit, the non-inverting input terminal of the operational amplifier A1 is also grounded through the resistor _R3 ; the inverting input terminal of the operational amplifier A1 is grounded through the resistor _R2 ; the operational amplifier A1 The output terminal of the operational amplifier A1 is used as the output terminal of the first differential amplifier circuit; the resistor _R4 is connected between the inverting input terminal and the output terminal of the operational amplifier A1.

Wherein, the first voltage follower includes a resistor _R5 , a resistor _R6 and an operational amplifier A2; the non-inverting input terminal of the operational amplifier A2 is connected to the output terminal of the first differential amplifier circuit through the resistor _R5 , the inverting input terminal of the operational amplifier A2 is connected to its output terminal through the resistor _R6 , and the output terminal of the operational amplifier A2 is used as the output terminal of the first voltage follower.

Wherein, the peak detection circuit includes a CT coil, a sampling resistor Rrs, a capacitor Crs, a half-wave rectification module and a peak detection module; the sampling resistor Rrs is connected to the output end of the CT coil in parallel, and the capacitor Crs is connected to the The sampling resistor Rrs is connected in parallel; the input terminal of the half-wave rectification module is connected to the connection terminal between the sampling resistor Rrs and the CT coil, and the input terminal of the peak detection module is connected to the output terminal of the half-wave rectification module , the output terminal of the peak detection module is used as the output terminal of the peak detection circuit.

Wherein, the half-wave rectification module includes a resistor R ₈ , a resistor R ₉ , a resistor R ₁₀ , a diode D ₉ , a diode D ₁₀ and an operational amplifier A ₃ ; one end of the resistor R ₈ is used as the input of the half-wave rectification module end, the other end of the resistor R ₈ is connected to the inverting input of the operational amplifier A3, and the non-inverting input of the operational amplifier A3 is grounded through the resistor R ₉ ; the anode of the diode D ₉ is connected to The inverting input terminal of the operational amplifier A3, the cathode of the diode D ₉ is connected to the output terminal of the operational amplifier A3; the anode of the diode D ₁₀ is connected to the output terminal of the operational amplifier A3, the diode The cathode of D ₁₀ serves as the output end of the half-wave rectification module; the resistor R ₁₀ is connected between the inverting input end of the operational amplifier A3 and the cathode of the diode D ₁₀ .

Wherein, the peak detection module includes a diode D ₁₁ , a capacitor C ₇ , a resistor R ₁₁ and an operational amplifier A4; the positive phase input of the operational amplifier A4 is used as the input of the peak detection module, and the diode D ₁₁ The anode is connected to the output terminal of the operational amplifier A4, and the cathode of the diode D ₁₁ is used as the output terminal of the peak detection module; the negative electrode of the diode D ₁₁ is also connected to the inverting input terminal of the operational amplifier A4; The capacitor C ₇ is connected between the cathode of the diode D ₁₁ and ground; the resistor R ₁₁ is connected in parallel with the capacitor C ₇ .

Wherein, the output detection circuit includes an output voltage detection circuit for collecting output voltage and an output current detection circuit for collecting output current.

Wherein, the resonant circuit includes an inductance L _r and a capacitor C _r connected in series in sequence; the non-serial connection terminal of the inductance L _r is used as the input terminal of the resonant circuit, and the non-serial connection terminal of the capacitor C _r is used as the output of the resonant circuit.

The main advantage of the utility model is:

(1) The utility model adopts a digital processor to control, with fast speed and flexible control;

(2) By increasing the input detection circuit to detect the input voltage, the input under-voltage protection and over-voltage protection are realized, and the resonant current overcurrent caused by the drop of the input voltage is avoided during the closed-loop operation, which improves the closed-loop operation of the LLC resonant conversion device time reliability;

(3) By adding a peak detection circuit, quickly detect the peak value of the resonant current, directly realize the limited protection of the peak value of the resonant current, avoid the overcurrent of the resonant current caused by too fast frequency adjustment during the closed-loop adjustment process, and improve the LLC resonance conversion The reliability of the device during closed-loop regulation.

Description of drawings

Fig. 1 is the structural representation of the LLC resonant conversion device provided by the utility model;

Fig. 2 is the circuit diagram of the LLC resonant conversion device provided by the utility model;

Fig. 3 is a schematic diagram of the driving level provided by the utility model;

Fig. 4 is the specific circuit diagram of the input detection circuit provided by the utility model;

Fig. 5 is the specific circuit diagram of the peak detection circuit provided by the utility model;

Fig. 6 (a) is the specific circuit diagram of the output voltage detection circuit provided by the utility model;

Fig. 6 (b) is the specific circuit diagram of the output current detection circuit that the utility model provides;

Fig. 7 is the specific circuit diagram of the driving circuit provided by the utility model;

Fig. 8 (a) is the main program flowchart of the DSP control system provided by the utility model;

Fig. 8 (b) is the interrupt program flowchart of the DSP control system provided by the utility model.

Detailed ways

In order to make the purpose, technical solution and advantages of the utility model clearer, the utility model will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the utility model, and are not intended to limit the utility model. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not constitute conflicts with each other.

The utility model provides an LLC resonant conversion device, which comprises a bridge circuit connected in series, a resonant circuit, a transformer, a rectifier circuit and a filter circuit; and an input detection circuit, an output detection circuit, a peak detection circuit, a drive circuit and a digital processor. The input end of the input detection circuit is connected to the input end of the LLC resonant conversion device, and the output end is connected to the digital processor for collecting the input voltage; the input end of the output detection circuit is connected to the output end of the LLC resonant conversion device, and the output end is connected to the A digital processor for collecting output voltage and output current; the input end of the peak detection circuit is connected to the resonant circuit, and the output end is connected to the digital processor for collecting the peak value of the resonant current; the input end of the driving circuit is connected to A digital processor whose output end is connected to the bridge circuit for driving the bridge circuit.

In the present invention, the bridge circuit may be a full-bridge circuit composed of switching devices, or a half-bridge circuit composed of switching devices. The resonant circuit is composed of resonant inductance L _r and resonant capacitor C _r connected in series, and its resonant frequency The transformer may be composed of at least two high-frequency transformers with center taps, the primary windings of the high-frequency transformers are connected in series, the center taps of the secondary windings are connected to the negative output terminal, and the other taps are connected to the rectifier circuit. The rectification circuit can adopt an uncontrolled rectification circuit composed of diodes. The filtering circuit can adopt C filtering or LC filtering. The input detection circuit consists of an amplifier circuit including a voltage Hall element. The peak detection circuit is composed of CT sensor, precision rectified current and single operational amplifier peak circuit. The drive circuit includes a high frequency isolation transformer and a bridge totem pole structure composed of MOSFETs.

The utility model adopts a digital processor for control, with fast speed and flexible control; by adding an input detection circuit to detect the input voltage, the input under-voltage protection and over-voltage protection can be realized, and the resonance caused by the drop of the input voltage can be avoided during closed-loop operation The current overcurrent improves the reliability of the LLC resonant conversion device during closed-loop operation; by adding a peak detection circuit, the peak value of the resonant current can be quickly detected, and the limited protection of the peak value of the resonant current can be directly realized, avoiding the frequency adjustment during the closed-loop adjustment process. The resonant current overcurrent caused by too fast improves the reliability of the LLC resonant conversion device in the closed-loop adjustment process.

As shown in Figure 1, the LLC resonant conversion device provided by the utility model includes a bridge circuit 10, a resonant circuit 11, a transformer 12, a rectifier circuit 13, a filter circuit 14, an input detection circuit 20, a drive circuit 21, Peak detection circuit 22, output detection circuit 23, digital processor 30, after the bridge circuit 10 is driven by the drive level, the input DC voltage is converted into a square wave voltage output with the same frequency as the drive level; the square wave voltage passes through the resonant circuit 11. A certain resonant impedance is formed to generate a resonant current; the resonant current flows into the primary side of the transformer 12, and flows out from the secondary side of the transformer 12 after transformation; the rectifier circuit 13 rectifies the secondary side current of the transformer 12, and outputs a half-wave current; filtering After the circuit 14 filters the output current of the rectification circuit 13, it outputs a direct current to supply power to the load. Wherein, in the input detection circuit 20, the input terminal is connected to the input terminal of the bridge circuit 10 as the input terminal of the LLC resonant conversion device, and the output terminal is connected to the first input terminal of the digital processor 30 for collecting the input voltage Vin; The input end of the circuit 21 is connected with the output end of the digital processor 30, and the output end is connected with the driving end of the bridge circuit 10, and generates a drive level according to the PWM control signal output by the digital processor 30; the input end of the peak detection circuit 22 is connected To the output end of the resonant circuit 11, the output end of the peak detection circuit 22 is connected to the second input end of the digital processor 30 for collecting the resonant current; the input end of the output detection circuit 23 is connected to the output end of the filter circuit 14, and the output The output terminal of the detection circuit 23 is connected to the third input terminal of the digital processor 30 for collecting the output voltage and output current; the digital processor 30 outputs according to the collected input voltage Vin and the resonant current, and according to the collected output voltage and output Current output PWM control signal. To control the operation of the LLC resonant conversion device, a TMS320F2808 chip is used as a digital processor in this embodiment.

The resonant circuit 11 is composed of a resonant inductor L _r and a resonant capacitor C _r connected in series, and its resonant frequency $f_r=\frac{1}{2\mathrm{\π}\sqrt{L_r{C}_r}}.$

As shown in FIG. 2 , it is a circuit diagram of an LLC resonant conversion device according to an embodiment of the present invention, including a bridge circuit 10 , a resonant circuit 11 , a transformer 12 , a rectifier circuit 13 and a filter circuit 14 connected in series. The bridge circuit 10 includes four switch tubes T1, T2, T3 and T4. The switch tubes T1 to T4 all include MOSFETs, freewheeling diodes and snubber capacitors, and the MOSFETs, freewheeling diodes and snubber capacitors are connected in parallel. The switching tube T1 and the switching tube T2 are in the same bridge arm, the switching tube T3 and the switching tube T4 are in the same bridge arm, and the two bridge arms are connected to the positive and negative bus bars of the input power supply, the input power supply voltage is 600V, the gap between the switching tube T1 and the switching tube T2 The point A between the switch tube T3 and the switch tube T4 is connected to the rear-end resonant circuit.

The resonant circuit 11 includes an inductor L _r and a capacitor C _r , the inductor L _r is connected in series with the capacitor C _r , the inductance L _r =37.07 uH, the capacitor C _r =23.63 nF, and the resonant frequency is 170 kHz.

The transformer 12 includes a first transformer and a second transformer. Both the first transformer and the second transformer have three windings, and both have a transformation ratio of 26:3:3. The primary winding of the first transformer is connected in series with the primary winding of the second transformer, the terminals s2, s3 of the secondary winding of the first transformer and the terminals s6, s7 of the secondary winding of the second transformer are jointly connected to the output negative pole, and the terminals s1, s4, s5 of the winding , s8 connected to the rear rectifier circuit.

The rectifier circuit 13 includes four diodes from the first to the fourth, the anode of the first diode _D5 is connected to the secondary terminal s1 of the first transformer, and the anode of the second diode _D6 is connected to the secondary terminal of the first transformer s4, the anode of the third diode _D7 is connected to the secondary terminal s5 of the second transformer, the anode of the fourth diode _D8 is connected to the secondary terminal s8 of the second transformer, and the negative poles of the first to fourth diodes are common Connect to output positive.

The filter circuit 14 includes a capacitor C, which is connected to the positive and negative poles of the output, and its capacitance C=11.48mF.

The drive levels of the switches T1-T4 are shown in Figure 3, the duty cycle of the drive level is D≈50%, the dead time td is fixed, and the cycle T is adjusted through closed-loop control.

Figure 4 shows an embodiment of the input detection circuit 20, including a first sampling unit 201, a first filter capacitor C _ins , a first differential amplifier circuit 202, a second filter capacitor C ₅ , a first voltage follower 203 and a first RC Filter 204; wherein the first sampling unit 201 includes a first voltage Hall device H1, a resistor R ₀ and a sampling resistor R _ins ; the first voltage Hall device H1 is connected to the positive and negative poles of the input of the LLC resonant conversion device through the resistor R ₀ , the output side of the first voltage Hall device H1 is connected to the sampling resistor R _{ins in} parallel to convert the current signal output by the voltage Hall H1 into a voltage signal V ₁ , and the filter capacitor C _ins is connected to the sampling resistor R _ins to smooth the first voltage Hall The output signal of the device H1; the resistors R ₁ , R ₂ , R ₃ , R ₄ and the operational amplifier A1 constitute the first differential amplifier circuit 202, which amplifies the voltage Hall output signal V ₁ proportionally to obtain a voltage V with a suitable range ₂ , the magnification ratio is Capacitor C ₅ is connected in parallel with resistor R ₃ for further filtering V ₂ ; resistors R ₅ , R ₆ and operational amplifier A2 form a first voltage follower 203, whose output voltage V ₃ follows voltage V ₂ and increases output impedance; Resistor R ₇ and capacitor C ₆ form an RC filter 204, which filters the voltage V ₃ to obtain a relatively clean and smooth voltage signal V _{in_s} , the voltage V _{in_s} is input to the digital processor 30, and is processed by the AD module inside the digital processor. AD conversion.

Figure 5 shows an embodiment of the peak detection circuit 22, including a CT coil, a sampling resistor Rrs, a capacitor Crs, a half-wave rectification module 221, and a peak detection module 222; wherein the output of the resonant circuit passes through the CT coil, and the CT coil turns ratio The number is 1:200, the ratio of CT coil secondary output current to resonant current is 1:200, the sampling resistor Rrs is connected to the CT coil output in parallel, and the AC current signal output by the CT is converted into an AC voltage signal V ₄ , and the capacitor Crs is connected in parallel Connected to the sampling resistor Rrs to filter the voltage _V4 ; resistors _R8 , _R9 , _R20 , diodes _D9 , _D10 and operational amplifier A3 form a half-wave rectification module 221, which performs half-wave rectification on the AC voltage signal _V4 , output only positive half-wave voltage signal V ₅ , diode D ₁₁ , capacitor C ₇ , resistor R ₁₁ and operational amplifier A4 form a peak detection module 222 to collect the peak value of the half-wave voltage signal V ₅ and output a peak DC voltage signal V _{rp_s} , the voltage V _{rp_s} is input to the digital processor 30 , and the AD conversion is performed by the AD module inside the digital processor 30 .

FIG. 6 shows an embodiment of the output detection circuit 23 , wherein (a) is the output voltage detection circuit 231 , and (b) is the output current detection circuit 232 . The output voltage detection circuit 231 includes a second sampling unit 2311, a filter capacitor C _os , a second differential amplifier circuit 2312, a capacitor C ₈ , a second voltage follower 2313 and a second RC filter 2314; wherein the second sampling unit 2311 includes The second voltage Hall H2, resistor R ₁₂ and sampling resistor R _os ; the voltage Hall H2 is connected to the positive and negative poles of the output of the LLC resonant conversion device through the resistor R ₁₂ , and the output side of the voltage Hall H2 is connected to the sampling resistor R _os to convert the voltage The current signal output by Hall H2 is converted into voltage signal V ₆ , and the filter capacitor C _os is connected to R _os to smooth the output signal of voltage Hall H2; resistors R ₁₃ , R ₁₄ , R ₁₅ , R ₁₆ and operational amplifier A5 constitute The second differential amplifier circuit 2312 amplifies the voltage Hall output signal V ₆ proportionally to obtain a voltage V ₇ in a suitable range, and the amplification ratio is Capacitor C ₈ is connected in parallel with R ₁₅ to further filter V ₆ ; resistors R ₁₇ , R ₁₈ and operational amplifier A6 form a second voltage follower 2313, whose output voltage V ₈ follows voltage V ₇ while increasing the output impedance; resistor R ₁₉ The second RC filter 2314 is formed with the capacitor _C9 , and the voltage _V8 is filtered to obtain a relatively clean and smooth voltage signal V _{o_s} , the voltage V _{o_s} is input to the digital processor 30, and AD is performed through the AD module inside the digital processor convert.

The output current detection circuit 232 includes a third sampling unit 2321, a sampling resistor R _os1 , a third differential amplifier circuit 2322, a capacitor C10, a third voltage follower 2323 and a third RC filter 2324; wherein the third sampling unit 2321 includes a third Current Hall H3 and sampling resistor R _os1 ; the third current Hall H3 is connected in series to the output, and its output side is connected in parallel with the sampling resistor R _os1 to convert the current signal output by the current Hall H3 into a voltage signal V ₉ , and the filter capacitor C _os1 is parallel connected to R _os1 to smooth the output signal of current Hall H3; resistors R ₂₀ , R ₂₁ , R ₂₂ , R ₂₃ and operational amplifier A7 form a third differential amplifier circuit 2322, which converts the current Hall output signal V ₉ into a voltage Amplify the ratio to get a voltage V ₁₀ with a suitable range, and the amplification ratio is Capacitor C ₁₀ is connected in parallel with R ₂₂ to further filter V ₉ ; resistors R ₂₄ , R ₂₅ and operational amplifier A8 form a third voltage follower 2323, whose output voltage V ₁₁ follows voltage V ₁₀ while increasing the output impedance; resistor R ₂₆ The third RC filter 2324 is formed with the capacitor C ₁₁ , and the voltage V ₁₁ is filtered to obtain a relatively clean and smooth voltage signal I _{o_s} , the voltage I _{o_s} is input to the digital processor 30, and AD is performed through the AD module inside the digital processor convert.

Figure 7 shows an embodiment of the driving circuit. DRIVE_H and DRIVE-L are two PWM signals sent by the digital processor respectively. The period and duty cycle of DRIVE_H and DRIVE_L are the same, and the phase difference is 180°. The primary side of the driving circuit adopts a totem pole driving structure composed of high-speed MOSFETs Q1-Q4 and capacitors _Cd1 - _Cd8 , which can realize fast switching and power amplification of the PWM signals DRIVE_H and DRIVE_L sent by the digital processor 30 . The secondary sides Q5-Q8 of the drive circuit respectively form a rapid discharge circuit for the drive levels G1-G4, and are turned off at the trailing edge of the accelerated drive level during the drive turn-off time.

Fig. 8 shows the flow chart of the DSP control system of the utility model embodiment, wherein, (a) is the flow chart of the main program, (b) is the flow chart of the interrupt program. When the LLC resonant conversion device is started, it first enters the main program, as shown in (a), after DSP initialization, variable initialization and zero drift correction, the main program enters an endless loop, and in the loop body, the DSP continuously performs logical judgments and communication inquiries. The main function of the logical judgment is to judge the operating state of the LLC resonant conversion device and control the transition between states; the main function of the communication query is to control the communication between the DSP and the upper computer. The closed-loop operation of the LLC resonant conversion device is realized by an interrupt program. As shown in (b), the DSP executes this interrupt program every 15us. After entering the interrupt, the DSP first reads the AD results of each sampling amount, and then performs fault judgment , Faults include input undervoltage fault, input overvoltage fault, resonant current overcurrent fault, output overvoltage fault, output overcurrent fault, and finally judge the operation mode, and perform voltage closed-loop control or current closed-loop control according to the judgment result.

The LLC resonant conversion device provided by the utility model is controlled by a digital processor, with fast speed and flexible control; by adding an input detection circuit to detect the input voltage, the input under-voltage protection and over-voltage protection are realized, and the closed-loop operation is avoided due to Resonant current overcurrent caused by input voltage drop; by adding a peak detection circuit to detect the peak value of the resonant current, the limit protection for the peak value of the resonant current can be directly realized, and the resonant current overcurrent caused by too fast frequency adjustment can be avoided during the closed-loop adjustment process. flow.

Those skilled in the art can easily understand that the above descriptions are only preferred embodiments of the present utility model, and are not intended to limit the present utility model. Any modifications, equivalent replacements and modifications made within the spirit and principles of the utility model Improvements and the like should all be included within the protection scope of the present utility model.

Claims (10)

1. a kind of LLC resonant conversion device is characterized in that, comprises bridge circuit (10), resonant circuit (11), transformer (12), rectifier circuit (13) and filter circuit (14) connected in series successively; Its characteristic In that, an input detection circuit (20), a drive circuit (21), a peak detection circuit (22), an output detection circuit (23) and a digital processor (30) are also included; The input end of the input detection circuit (20) is connected to the input end of the bridge circuit (10), the output end of the input detection circuit (20) is connected to the first input end of the digital processor (30) connect; The input end of the peak detection circuit (22) is connected to the connection end of the resonant circuit (11) and the transformer (12), and the output end of the peak detection circuit (22) is connected to the digital processor (30 ) is connected to the second input end; The input end of the output detection circuit (23) is connected to the output end of the filter circuit (14), and the output end of the output detection circuit (23) is connected to the third input end of the digital processor (30) ; The input terminal of the driving circuit (21) is connected with the output terminal of the digital processor (30), and the output terminal of the driving circuit (21) is connected with the control terminal of the bridge circuit (10). 2. The LLC resonant conversion device according to claim 1, characterized in that, the input detection circuit (20) comprises a first differential amplifier circuit (202), a first voltage follower (203) and a first RC filter (204); and the first sampling unit (201), filter capacitor C _ins and filter capacitor C ₅ ; The filter capacitor _C5 is connected between the non-inverting input terminal of A1 in the first differential amplifier circuit (202) and ground; The filter capacitor C _ins is connected between the output terminal of the first sampling unit (201) and ground, and the input terminal of the first sampling unit (201) is used as the input terminal of the input detection circuit (20); The output terminal of the first RC filter (204) serves as the output terminal of the input detection circuit (20). 3. LLC resonant conversion device as claimed in claim 2, is characterized in that, described first sampling unit (201) comprises first voltage Hall device H1, resistance R ₀ and sampling resistance R _ins ; The positive pole V+ of the voltage input terminal of the first voltage Hall device H1 is connected to the positive pole of the input of the LLC resonant conversion device through a resistor _R0 , and the negative pole V- of the voltage input terminal of the first voltage Hall device H1 is connected to the input of the resonant conversion device Negative pole, the output terminal of the first voltage Hall device H1 is used as the output terminal of the first sampling unit (201), and the output terminal of the first voltage Hall device H1 is also grounded through the sampling resistor R _ins . 4. The LLC resonant conversion device according to claim 2, wherein the first differential amplifier circuit (202) comprises a resistor R ₁ , a resistor R ₂ , a resistor R ₃ , a resistor R ₄ and an operational amplifier A1; The positive-phase input terminal of the operational amplifier A1 is connected to the output terminal of the first sampling unit (201) through the resistor _R1 , and the positive-phase input terminal of the operational amplifier A1 is also grounded through the resistor _R3 ; The inverting input terminal of the operational amplifier A1 is grounded through the resistor _R2 ; the output terminal of the operational amplifier A1 is used as the output terminal of the first differential amplifier circuit (202); the resistor _R4 is connected to the Between the inverting input and output of operational amplifier A1. 5. The LLC resonant conversion device according to claim 2, characterized in that, the first voltage follower (203) comprises a resistor R ₅ , a resistor R ₆ and an operational amplifier A2; The non-inverting input terminal of the operational amplifier A2 is connected to the output terminal of the first differential amplifier circuit (202) through the resistor _R5 , and the inverting input terminal of the operational amplifier A2 is connected to the output terminal of the first differential amplifier circuit (202) through the resistor _R6 . Its output terminal, the output terminal of the operational amplifier A2 is used as the output terminal of the first voltage follower (203). 6. The LLC resonant conversion device according to any one of claims 1-5, wherein the peak detection circuit (22) comprises a CT coil, a sampling resistor Rrs, a capacitor Crs, a half-wave rectification module (221) and Peak detection module (222); The sampling resistor Rrs is connected in parallel to the output terminal of the CT coil, the capacitor Crs is connected in parallel with the sampling resistor Rrs; the input terminal of the half-wave rectification module (221) is connected to the sampling resistor Rrs and the The connection end of the CT coil, the input end of the peak detection module (222) is connected to the output end of the half-wave rectification module (221), and the output end of the peak detection module (222) is used as the peak detection circuit (22) output. 7. The LLC resonant conversion device according to claim 6, characterized in that, the half-wave rectification module (221) comprises a resistor R ₈ , a resistor R ₉ , a resistor R ₁₀ , a diode D ₉ , a diode D ₁₀ and an operational amplifier A3; One end of the resistance R ₈ is used as the input end of the half-wave rectification module (221), and the other end of the resistance R ₈ is connected to the inverting input end of the operational amplifier A3, and the non-phase input end of the operational amplifier A3 The input terminal is grounded through the resistor _R9 ; The anode of the diode _D9 is connected to the inverting input of the operational amplifier A3, and the cathode of the diode _D9 is connected to the output of the operational amplifier A3; The anode of the diode D ₁₀ is connected to the output terminal of the operational amplifier A3, and the cathode of the diode D ₁₀ is used as the output terminal of the half-wave rectification module (221); The resistor _R10 is connected between the inverting input terminal of the operational amplifier A3 and the cathode of the diode _D10 . 8. The LLC resonant conversion device according to claim 6, wherein the peak detection module (222) comprises a diode D ₁₁ , a capacitor C ₇ , a resistor R ₁₁ and an operational amplifier A4; The positive-phase input terminal of the operational amplifier A4 is used as the input terminal of the peak detection module (222), the anode of the diode D ₁₁ is connected to the output terminal of the operational amplifier A4, and the cathode of the diode D ₁₁ is used as the input terminal of the peak detection module (222). The output terminal of the peak detection module (222); the cathode of the diode D ₁₁ is also connected with the inverting input terminal of the operational amplifier A4; The capacitor C ₇ is connected between the cathode of the diode D ₁₁ and ground; the resistor R ₁₁ is connected in parallel with the capacitor C ₇ . 9. The LLC resonant conversion device as claimed in claim 1, characterized in that, the output detection circuit (23) comprises an output voltage detection circuit (231) for collecting the output voltage and an output current detection circuit for collecting the output current circuit (232). 10. LLC resonant conversion device as claimed in claim 1, is characterized in that, described resonant circuit (11) comprises inductance L _r and electric capacity C _r connected in series successively; The non-series connection end of the inductor L _r is used as the input end of the resonant circuit (11), and the non-series connection end of the capacitor C _r is used as the output end of the resonant circuit (11).