Control circuit for realizing feed-forward of input voltage by adopting secondary PWM (Pulse-Width Modulation) waveform

Abstract

The invention discloses a control circuit for realizing input voltage feedforward by adopting a secondary PWM waveform, and belongs to the field of DC-DC. The control circuit comprises a main power transformer Tx, a main power rectifying circuit, a PWM rectifying circuit and a sawtooth wave generating circuit, a main power transformer Tx is arranged in the main power rectifying circuit, the main power rectifying circuit is connected with the PWM rectifying circuit, and the PWM rectifying circuit is connected with the sawtooth wave generating circuit. According to the invention, a sawtooth signal proportional to the input voltage is generated, and feedforward control of the input voltage is realized. According to the DC-DC module power supply circuit, the main power transformer and the main power rectification circuit are shared, an input voltage sampling circuit and a signal isolation feedback circuit do not need to be additionally adopted, the space and the size in the module are saved, the dynamic response of the module power supply is improved, and the circuit has a certain application prospect in the field of high-power-density DC-DC module power supplies.

Description

Technical Field

[0001] The present invention relates to the field of DC-DC, and specifically to an input voltage feedforward control circuit implemented by using a secondary PWM waveform. Background Art

[0002] Isolated DC-DC module power supplies are widely used in fields such as rail transit, new energy vehicles, drones, and radar electronic equipment due to their characteristics of high efficiency and high power density. The control methods of isolated DC-DC module power supplies are generally divided into two types: primary side control and secondary side control. When using the primary side control method, the control chip is placed on the primary side, and an optocoupler device is required to feedback the output voltage signal in real time to participate in the closed-loop control. At the same time, the drive signal needs to be transmitted to the secondary side for synchronous rectification or active absorption. However, the characteristics of the optocoupler device are greatly affected by temperature and have a long delay time. The secondary side control method is to place the control chip on the secondary side, which can avoid using an optocoupler device, and perform closed-loop compensation control by sampling voltage and current signals on the secondary side in real time. The input voltage range of the isolated DC-DC module power supply is wide. When the input voltage changes rapidly, it is necessary to keep the output voltage stable. The DC-DC module using the primary side control method can flexibly sample the input voltage for feedforward compensation control to meet the dynamic response requirements of the module power supply; when using the secondary side control method, it is necessary to sample the input voltage on the primary side and feedback it to the secondary side to participate in the feedforward control, and generally voltage sensors and other devices are required.

[0003] Due to the small volume and limited size of the isolated DC-DC module power supply, when the isolated DC-DC module power supply uses the secondary side control method, it is necessary to sample the primary input voltage and isolate and transmit the sampled voltage signal to the secondary side. Since the size of the voltage sensor is large and the price is high, it generally cannot be used in the module power supply. Therefore, how to simply implement the feedforward control of the input voltage is a problem and challenge faced by the high power density isolated DC-DC module power supply. Summary of the Invention

[0004] For the above problems existing in the prior art, the purpose of the present invention is to provide an input voltage feedforward control circuit implemented by using a secondary PWM waveform to solve the problems proposed in the above background art.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] An input voltage feedforward control circuit implemented by using a secondary PWM waveform, including a main power transformer Tx, a main power rectification circuit, a PWM rectification circuit, and a sawtooth wave generating circuit;

[0007] The main power rectification circuit is internally provided with the main power transformer Tx, the main power rectification circuit is connected to the PWM rectification circuit, and the PWM rectification circuit is connected to the sawtooth wave generating circuit.

[0008] The main power rectification circuit includes MOS transistor Q1, MOS transistor Q2, MOS transistor Q3, MOS transistor Q4, MOS transistor Q5, MOS transistor Q6, MOS transistor Q7, MOS transistor Q8 and power supply Vin;

[0009] The PWM rectification circuit includes diode D1, resistor R2 and capacitor C1;

[0010] The sawtooth wave generating circuit includes resistor R4, diode D2, capacitor C2 and power supply V1.

[0011] As a further solution of the present invention: the positive pole of the power supply Vin in the main power rectification circuit is simultaneously connected to the drain of MOS transistor Q1 and the drain of MOS transistor Q3;

[0012] The negative pole of the power supply Vin in the main power rectification circuit is simultaneously connected to the source of MOS transistor Q2 and the source of MOS transistor Q4;

[0013] The source of MOS transistor Q1 is connected to the drain of MOS transistor Q2, and the source of MOS transistor Q3 is connected to the drain of MOS transistor Q4;

[0014] The source of MOS transistor Q3 in the main power rectification circuit is connected to one end of the input side of the main power transformer Tx; the source of MOS transistor Q1 is connected to the other end of the input side of the main power transformer Tx;

[0015] One end of the output side of the main power transformer Tx is connected to the source of MOS transistor Q5; the other end of the output side of the main power transformer Tx is connected to the source of MOS transistor Q7;

[0016] The drain of MOS transistor Q5 is connected to the drain of MOS transistor Q7; the source of MOS transistor Q5 is connected to the drain of MOS transistor Q6;

[0017] The source of MOS transistor Q6 is connected to the source of MOS transistor Q8; the source of MOS transistor Q7 is connected to the drain of MOS transistor Q8.

[0018] As a further solution of the present invention: the gates of MOS transistor Q1, MOS transistor Q2, MOS transistor Q3, MOS transistor Q4 are connected to an external drive signal.

[0019] As a further solution of the present invention: the gates of MOS transistor Q5, MOS transistor Q6, MOS transistor Q7, MOS transistor Q8 are connected to an external drive signal.

[0020] As a further solution of the present invention: the positive pole of diode D1 in the PWM rectification circuit is connected to the drain of MOS transistor Q5 in the main power rectification circuit;

[0021] The negative electrode of diode D1 is movably connected to one end of resistor R2, and the other end of resistor R2 is grounded.

[0022] As a further solution of the present invention: A capacitor C1 is connected in parallel at both ends of resistor R2 in the PWM rectifier circuit.

[0023] As a further solution of the present invention: The negative electrode of diode D2 in the sawtooth wave generating circuit is connected to one end of resistor R3, and the other end of resistor R3 is connected to the negative electrode of diode D1 in the PWM rectifier circuit;

[0024] The positive electrode of diode D2 is connected to the positive electrode of power supply V1, and the negative electrode of power supply V1 is grounded;

[0025] The negative electrode of diode D2 is connected to one end of resistor R4, and the other end of resistor R4 is connected to one end of capacitor C2; The other end of capacitor C2 is grounded.

[0026] As a further solution of the present invention: The main power rectifier circuit is connected to the filter circuit, and the filter circuit includes inductor Lo, capacitor C0 and resistor R1.

[0027] As a further solution of the present invention: One end of inductor Lo in the filter circuit is connected to the drain of MOS transistor Q7; The other end of inductor Lo is connected to one end of resistor R1, and the other end of resistor R1 is connected to the source of MOS transistor Q8.

[0028] As a further solution of the present invention: A capacitor C0 is connected in parallel at both ends of resistor R1 in the filter circuit.

[0029] Compared with the prior art, the beneficial effects of the present invention are:

[0030] The present invention combines the main power transformer, the main power rectifier circuit, the PWM rectifier circuit and the sawtooth wave generating circuit in a superposition manner to generate a sawtooth signal proportional to the input voltage, and realizes the feedforward control of the input voltage. The present invention shares the main power voltage transformer and the main power rectifier circuit, and does not need to additionally adopt a sampling circuit for the input voltage and a signal isolation feedback circuit, saving the space and size inside the module, improving the dynamic response of the module power supply, and this circuit has a certain application prospect in the field of high power density DC-DC module power supplies. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a circuit schematic diagram of a circuit for realizing input voltage feedforward control by using a secondary side PWM waveform disclosed in the embodiment.

[0032] Figure 2A full-bridge circuit input voltage V in an input voltage feedforward control circuit implemented using a secondary PWM waveform is disclosed for an embodiment in and the primary voltage V of the transformer AB and the output PWM voltage V PWM waveform schematic diagram.

[0033] Figure 3 A waveform diagram of the output PWM voltage, rectified waveform Vrec, RAMP voltage, and duty cycle in an input voltage feedforward control circuit implemented using a secondary PWM waveform is disclosed for an embodiment. Specific implementation manner

[0034] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention; obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0035] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "installed", "provided with", "connected", and "connected" should be understood in a broad sense; for example, it may be a fixed connection, a detachable connection, or an integral connection, it may be a mechanical connection, it may be an electrical connection, it may be directly connected, or indirectly connected through an intermediate medium, and it may be the internal communication of two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0036] Please refer to Figures 1-3 , an input voltage feedforward control circuit implemented using a secondary PWM waveform, including a main power transformer Tx, a main power rectification circuit, a PWM rectification circuit, and a sawtooth wave generation circuit;

[0037] The main power rectification circuit is internally provided with the main power transformer Tx, the main power rectification circuit is connected to the PWM rectification circuit, and the PWM rectification circuit is connected to the sawtooth wave generation circuit.

[0038] The main power rectification circuit includes MOS transistors Q1, Q2, Q3, Q4, Q5, Q6, Q7, Q8, and a power supply Vin;

[0039] The PWM rectification circuit includes a diode D1, a resistor R2, and a capacitor C1;

[0040] The sawtooth wave generation circuit includes a resistor R4, a diode D2, a capacitor C2, and a power supply V1;

[0041] Through the superposition and combination of the main power transformer, the main power rectification circuit, the PWM rectification circuit and the sawtooth wave generating circuit, a sawtooth signal proportional to the input voltage is generated to achieve the feedforward control of the input voltage. Using the method of the present invention, the main power voltage transformer and the main power rectification circuit are shared, and there is no need to additionally adopt a sampling circuit for the input voltage and a signal isolation feedback circuit, saving the space and size inside the module. This circuit has a certain application prospect in the field of high power density DC-DC module power supplies.

[0042] The positive pole of the power supply Vin in the main power rectification circuit is simultaneously connected to the drain of the MOS transistor Q1 and the drain of the MOS transistor Q3;

[0043] The negative pole of the power supply Vin in the main power rectification circuit is simultaneously connected to the source of the MOS transistor Q2 and the source of the MOS transistor Q4;

[0044] The source of the MOS transistor Q1 is connected to the drain of the MOS transistor Q2, and the source of the MOS transistor Q3 is connected to the drain of the MOS transistor Q4;

[0045] The source of the MOS transistor Q1 is the output node B; the source of the MOS transistor Q3 is the output node A;

[0046] The gates of the MOS transistor Q1, the MOS transistor Q2, the MOS transistor Q3, the MOS transistor Q4 are connected to an external drive signal;

[0047] The source of the MOS transistor Q3 in the main power rectification circuit is connected to one end of the input side of the main power transformer Tx; the source of the MOS transistor Q1 is connected to the other end of the input side of the main power transformer Tx;

[0048] One end of the output side of the main power transformer Tx is connected to the source of the MOS transistor Q5; the other end of the output side of the main power transformer Tx is connected to the source of the MOS transistor Q7;

[0049] The drain of the MOS transistor Q5 is connected to the drain of the MOS transistor Q7; the source of the MOS transistor Q5 is connected to the drain of the MOS transistor Q6;

[0050] The source of the MOS transistor Q6 is connected to the source of the MOS transistor Q8; the source of the MOS transistor Q7 is connected to the drain of the MOS transistor Q8;

[0051] The gates of the MOS transistor Q5, the MOS transistor Q6, the MOS transistor Q7, the MOS transistor Q8 are connected to an external drive signal;

[0052] The positive pole of the diode D1 in the PWM rectification circuit is connected to the drain of the MOS transistor Q5 in the main power rectification circuit; the voltage of the positive pole of the diode D1 is the output PWM voltage V PWM; The negative voltage of diode D1 is the voltage waveform Vrec after PWM rectification and filtering;

[0053] One end of the negative electrode of diode D1 is movably connected to one end of resistor R2, and the other end of resistor R2 is grounded;

[0054] A capacitor C1 is connected in parallel across both ends of resistor R2;

[0055] One end of the negative electrode of diode D2 in the sawtooth wave generating circuit is connected to one end of resistor R3, and the other end of resistor R3 is connected to the negative electrode of diode D1 in the PWM rectifier circuit;

[0056] The positive electrode of diode D2 is connected to the positive electrode of power supply V1, and the negative electrode of power supply V1 is grounded; the voltage at the positive electrode of diode D2 is the DC voltage Vrdc;

[0057] One end of the negative electrode of diode D2 is connected to one end of resistor R4, and the other end of resistor R4 is connected to one end of capacitor C2; the other end of capacitor C2 is grounded;

[0058] The main power rectifier circuit is connected to the filter circuit. The filter circuit includes inductor Lo, capacitor C0 and resistor R1. One end of inductor Lo is connected to the drain of MOS transistor Q7; the other end of inductor Lo is connected to one end of resistor R1, and the other end of resistor R1 is connected to the source of MOS transistor Q8;

[0059] A capacitor C0 is connected in parallel across both ends of resistor R1;

[0060] Taking the isolated DC-DC module power supply with an input voltage of 200 - 400Vdc and an output voltage of 28Vdc as an example.

[0061] Figure 1 It is a schematic diagram of a common hard-switching full-bridge circuit in an isolated DC-DC module power supply, including the input voltage Vin; the primary-side power switch devices Q1 - Q4 form a full-bridge circuit; the main power transformer Tx includes two windings: the primary winding P1 and the secondary winding S1, where the transformer turns ratio is n:1; the secondary-side synchronous rectifier circuit includes: switching transistors Q5 - Q8. The output filter circuit includes the output inductor Lo and the output capacitor C0, which form a low-pass filter to filter out the high-frequency ripples of the PWM waveform to obtain the output voltage.

[0062] Figure 3 It is a specific circuit proposed by the present invention for implementing input voltage feedforward control using the secondary-side PWM waveform. The main circuit principle is to perform uncontrolled rectification on the PWM waveform. The voltage value obtained after rectification is Vin / n. After voltage division processing of this voltage, it is superimposed on the DC voltage that generates the sawtooth wave. The sawtooth wave as a whole serves as the RAMP signal to generate the duty cycle to control the switching transistors Q1 - Q4.

[0063] Figure 2 For the input voltage Vin of the full-bridge circuit, the primary-side voltage VAB of the transformer, and the output PWM voltage V PWM Waveform schematic diagram (from top to bottom). It can be seen that the input voltage is 400V. Since the hard-switching waveform modulation method is adopted, the primary-side voltage of the transformer is a high-frequency pulse waveform. The peak value of the pulse waveform is the input voltage value Vin. The period of the pulse waveform is the same as the switching period of the switching tubes Q1-Q4. Its pulse width is the conduction time of the switching tubes Q1-Q4. The high-frequency pulse voltage is stepped down by high-frequency isolation of the transformer to obtain the secondary-side voltage waveform, which is the same as the primary-side waveform of the transformer. However, the peak value of the secondary-side voltage waveform is Vin / n. The secondary-side waveform of the transformer is rectified by the main power synchronous rectification to obtain the PWM waveform, and the peak value of the PWM waveform is also Vin / n, and the period is half of the switching period of the switching tubes. It can be seen that the amplitude of the PWM voltage waveform itself contains the information of the input voltage value. When the input voltage changes, the amplitude of the PWM voltage also changes in the same proportion, achieving the function of isolating and sampling the input voltage.

[0064] Figure 3 This is the working waveform of the method for realizing the input voltage feedforward control by using the secondary-side PWM waveform in the present invention. From top to bottom, they are the main power PWM waveform, the voltage waveform Vrec after PWM rectification and filtering, the RAMP voltage waveform, and the duty cycle signal waveform. It can be seen that after being rectified by the diode, the PWM waveform is approximately changed into a DC voltage, and its DC voltage value is Vin / n. This voltage is processed by voltage division and jointly generates the sawtooth waveform Vramp with the DC voltage Vrdc, where the voltage value of Vrdc remains unchanged all the time. When the input voltage Vin changes from 400V to 300V, the peak value of the PWM waveform changes from 67V to 50V, and the equivalent value of the rectified Vrec voltage changes to 50V. The peak value of the generated RAMP voltage and the duty cycle signal also change correspondingly, thereby realizing the input voltage feedforward control and ensuring the dynamic response of the isolated module power supply when the input voltage changes.

[0065] In the field of isolated DC-DC module power supplies, the present invention provides a method and a circuit for realizing the input voltage feedforward control by using the secondary-side PWM waveform. By superimposing and combining the main power transformer, the main power rectification circuit, the PWM rectification circuit, and the sawtooth waveform generation circuit, a sawtooth signal proportional to the input voltage is generated to realize the input voltage feedforward control. Using the method of the present invention, the main power transformer and the main power rectification circuit are shared, and there is no need to additionally adopt the sampling circuit of the input voltage and the signal isolation feedback circuit, saving the space and size inside the module. This circuit has a certain application prospect in the field of high-power density DC-DC module power supplies.

[0066] The present invention relates to the technical field of modular power supplies, and provides a method and a circuit for implementing input voltage feedforward control by using a secondary-side PWM waveform. Through the combination of a main power transformer, a main power rectification circuit, a PWM rectification circuit, and a sawtooth circuit, a sawtooth signal proportional to the input voltage is generated to achieve the feedforward control of the input voltage. By using the method of the present invention, the separate sampling circuit for the input voltage and the signal isolation feedback circuit are omitted, saving the space of the modular power supply and improving the dynamic response of the modular power supply.

[0067] The present invention provides a method and a circuit for implementing input voltage feedforward control by using a secondary-side PWM waveform. Through the superposition combination of a main power transformer, a main power rectification circuit, a PWM rectification circuit, and a sawtooth wave generating circuit, a sawtooth signal proportional to the input voltage is generated to achieve the feedforward control of the input voltage. By using the method of the present invention, the sampling circuit for the input voltage and the signal isolation feedback circuit are omitted, the feedforward control of the input voltage is achieved, and the dynamic response of the modular power supply is improved.

[0068] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention, and any reference signs in the claims should not be regarded as limiting the claims involved.

[0069] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only includes an independent technical solution. This narrative manner of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A circuit for realizing input voltage feedforward control using secondary side PWM waveform, characterized in that: It includes a main power transformer Tx, a main power rectifier circuit, a PWM rectifier circuit and a sawtooth wave generator circuit; The main power rectifier circuit is provided with a main power transformer Tx inside, the main power rectifier circuit is connected to the PWM rectifier circuit, and the PWM rectifier circuit is connected to the sawtooth wave generator circuit; The main power rectifier circuit includes MOS tube Q1, MOS tube Q2, MOS tube Q3, MOS tube Q4, MOS tube Q5, MOS tube Q6, MOS tube Q7, MOS tube Q8 and a power supply Vin; The PWM rectifier circuit includes a diode D1, a resistor R2 and a capacitor C1; The sawtooth wave generating circuit includes a resistor R4, a diode D2, a capacitor C2 and a power source V1.

2. The circuit for realizing input voltage feedforward control by using secondary side PWM waveform according to claim 1, characterized in that: The positive electrode of the power source Vin in the main power rectifier circuit is connected to the drain of the MOS tube Q1 and the drain of the MOS tube Q3 at the same time; The negative electrode of the power supply Vin in the main power rectifier circuit is connected to the source of the MOS tube Q2 and the source of the MOS tube Q4 at the same time; The source of the MOS tube Q1 is connected to the drain of the MOS tube Q2, and the source of the MOS tube Q3 is connected to the drain of the MOS tube Q4; The source of the MOS tube Q3 in the main power rectifier circuit is connected to one end of the input side of the main power transformer Tx; the source of the MOS tube Q1 is connected to the other end of the input side of the main power transformer Tx; One end of the output side of the main power transformer Tx is connected to the source of the MOS tube Q5; the other end of the output side of the main power transformer Tx is connected to the source of the MOS tube Q7; The drain of the MOS tube Q5 is connected to the drain of the MOS tube Q7; the source of the MOS tube Q5 is connected to the drain of the MOS tube Q6; The source of the MOS transistor Q6 is connected to the source of the MOS transistor Q8; the source of the MOS transistor Q7 is connected to the drain of the MOS transistor Q8.

3. The circuit for realizing input voltage feedforward control by using secondary side PWM waveform according to claim 2, characterized in that: The gate of the MOS transistor Q1 , the gate of the MOS transistor Q2 , the gate of the MOS transistor Q3 , and the gate of the MOS transistor Q4 are connected to an external driving signal.

4. The circuit for realizing input voltage feedforward control by using secondary side PWM waveform according to claim 3, characterized in that: The gate of the MOS transistor Q5 , the gate of the MOS transistor Q6 , the gate of the MOS transistor Q7 , and the gate of the MOS transistor Q8 are connected to an external driving signal.

5. The circuit for realizing input voltage feedforward control by using secondary side PWM waveform according to claim 4, characterized in that: The positive electrode of the diode D1 in the PWM rectifier circuit is connected to the drain of the MOS tube Q5 in the main power rectifier circuit; The cathode of the diode D1 is connected to one end of the resistor R2, and the other end of the resistor R2 is grounded.

6. The circuit for realizing input voltage feedforward control by using secondary side PWM waveform according to claim 5, characterized in that: A capacitor C1 is connected in parallel to both ends of the resistor R2 in the PWM rectifier circuit.

7. The circuit for realizing input voltage feedforward control by using secondary side PWM waveform according to claim 6, characterized in that: The cathode of the diode D2 in the sawtooth wave generating circuit is connected to one end of the resistor R3, and the other end of the resistor R3 is connected to the cathode of the diode D1 in the PWM rectifier circuit; The anode of the diode D2 is connected to the anode of the power supply V1, and the cathode of the power supply V1 is grounded; The cathode of the diode D2 is connected to one end of the resistor R4, the other end of the resistor R4 is connected to one end of the capacitor C2; the other end of the capacitor C2 is grounded.

8. The circuit for realizing input voltage feedforward control by using secondary side PWM waveform according to claim 7, characterized in that: The main power rectification circuit is connected to a filter circuit, and the filter circuit includes an inductor Lo, a capacitor C0 and a resistor R1.

9. The circuit for implementing input voltage feedforward control using secondary side PWM waveform according to claim 8, characterized in that: One end of the inductor Lo in the filter circuit is connected to the drain of the MOS tube Q7; the other end of the inductor Lo is connected to one end of the resistor R1, and the other end of the resistor R1 is connected to the source of the MOS tube Q8.

10. The circuit for realizing input voltage feedforward control by using secondary side PWM waveform according to claim 9, characterized in that: The two ends of the resistor R1 in the filter circuit are connected in parallel with a capacitor C0.

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