Modulation mode switching synchronous rectification soft switching step-down type constant voltage power supply

Abstract

The invention provides a modulation mode switching synchronous rectification soft switching buck type constant voltage power supply which comprises an input filter circuit, a power inductor L1, an output filter circuit, a main switch tube Q1, a synchronous rectification tube Q2 and a control circuit. The left end of the power inductor L1 is connected to the source electrode of the main switch tube Q1 and the drain electrode of the synchronous rectifier tube Q2, the right end of the power inductor L1 is connected to the positive electrode of the output capacitor, the drain electrode of the main switch tube Q1 is connected to the positive electrode of the input capacitor, and the source electrode of the synchronous rectifier tube Q2 is connected to a reference ground through a power inductor current sampling resistor RS1; and the control circuit respectively controls the on-off states of the main switch tube Q1 and the synchronous rectifier tube Q2 so as to realize zero-voltage conduction of the synchronous rectifier tube Q2. Through the characteristics of different modulation modes, light-load and heavy-load modulation mode switching and synchronous rectifier tube soft switching are realized, and the loss of the switching power supply under different conditions is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of switching power supplies, in particular to a modulation mode switching synchronous rectification soft switching step-down constant voltage power supply. Background Art

[0002] With the rapid development of electronic information technology, miniaturized and integrated electronic devices emerge in an endless stream. Electronic devices in the fields of Internet of Things, industrial electronics, automotive electronics, etc. are full of opportunities and challenges, which makes the research of power management technology receive widespread attention in the field of integrated circuits. At the same time, due to the diversification of electronic product functions and miniaturization of volume, the performance and application requirements of power supplies have been raised to a more stringent level.

[0003] The switching power supply controls the periodic on and off of the power switch tube in the system, thereby controlling the energy transmission and conversion process to adjust the output voltage value, and has significant application advantages such as small size, low power consumption, high efficiency, and wide adjustment range. In non-isolated topology applications below 100W, compared with various common switching power supply topologies, the BUCK converter uses fewer components, has a simpler structure, lower cost, and better transient response. In addition, increasing the switching frequency can reduce the size of the peripheral devices of the switching power supply, especially the size of the filter capacitor and the filter inductor, which can reduce the size and cost of the peripheral system. Moreover, the increase in the switching frequency can improve the dynamic response characteristics of the system. Therefore, in response to the demand for miniaturization and lightweight of the switching power supply, it is necessary to further increase the operating frequency of the switching power supply.

[0004] The working characteristics of the switching power supply are different under different working conditions. When the system works in DCM state, the conversion efficiency is high, but as the system load increases, the inductor current ripple is 50% of the system, which can easily lead to inductor saturation and abnormal system operation; when the system works in CCM state, the conversion efficiency is lower than DCM, and the inductor current ripple can be controlled to less than 10% of the current flowing through.

[0005] For switching power supplies under high-frequency operation, snubber circuit loss, switching loss and transformer loss are the three main sources of loss. Among them, the switching loss of the buck switching power supply switch tube is proportional to the operating frequency, which seriously affects the efficiency of the buck switching power supply. Therefore, it is particularly important to reduce the switching loss of the buck converter switch tube. Summary of the invention

[0006] In view of the above technical problems, the present invention provides a modulation mode switching synchronous rectification soft switch step-down constant voltage power supply. Based on the BUCK topology, by replacing the rectifier diode with a MOS tube, during the dead time, since the direction of the inductor current cannot change suddenly in a short time, the power inductor and the synchronous rectifier parasitic capacitance and the output capacitor form a loop with the system load. While the current supplies power to the output capacitor and the load, it discharges the parasitic junction capacitance of the synchronous rectifier. When the charge of its parasitic junction capacitance is zero, the voltage across the synchronous rectifier is zero. At this time, the synchronous rectifier is turned on again, and the zero voltage start ZVS of the synchronous rectifier can be realized, thereby realizing the soft switch of the rectifier and reducing the system switching loss. At the same time, a modulation mode switching algorithm is provided. Since the PWM modulation mode is less efficient under light load conditions, and in the DCM working mode, the loop gain, response speed, and system stability of the compensator originally designed using the CCM mode may be negatively affected. The PFM modulation mode is more efficient than the PWM modulation mode under light load conditions, but its efficiency is significantly lower than the PWM modulation mode under heavy load conditions. Therefore, when the system load is light, the system switches to PFM modulation mode, and when the system load is heavy, it switches to PWM modulation mode. This modulation mode switching working mode can enable the converter to maintain extremely high efficiency and small ripple within a wide current output range.

[0007] To achieve the above object, the present invention provides the following technical solution: a modulation mode switching synchronous rectification soft switch step-down constant voltage power supply, comprising a power inductor L1, a main switch tube Q1, a synchronous rectifier tube Q2, an input capacitor C IN , output capacitor C OUT , output filter inductor L f , output filter capacitor C f , power inductor current sampling resistor R S1 , output current sampling resistor R S2 ; The left end of the power inductor L1 is connected to the source of the main switch tube Q1 and the drain of the synchronous rectifier tube Q2, and the right end is connected to the output capacitor C OUT The positive electrode is connected to the left end of the output filter inductor, and the drain of the main switch tube Q1 is connected to the input capacitor C IN The positive electrode is connected to the positive electrode of the input DC power supply, and the source side of the synchronous rectifier Q2 passes through the power inductor current sampling resistor R S1 Connect the input reference ground, the input capacitor C IN The negative pole, the negative pole of the input DC power supply, is connected to the reference ground; The filter inductor L f The left end is connected to the output capacitor C OUT The positive pole, the right end is connected to the output filter capacitor C f The positive terminal, the output capacitor C OUT Negative pole, output filter capacitor C fThe negative pole is connected to the reference ground; The control circuit is used to provide a main switch tube control signal and a synchronous rectifier tube control signal to respectively control the switch states of the main switch tube Q1 and the synchronous rectifier tube Q2 to achieve zero voltage conduction of the synchronous rectifier tube Q2.

[0008] Furthermore, a modulation mode switching synchronous rectification soft switch step-down constant voltage power supply, the control circuit includes: A sampling unit, used to sample the inductor current signal of the modulation mode switching synchronous rectification soft switching buck constant voltage power supply, and output voltage and current signals; A feedback unit, which adjusts according to the signal obtained by the sampling unit to obtain a compensation signal; The driving unit generates a main switch tube control signal and a synchronous rectifier tube control signal according to the compensation signal obtained by the feedback unit.

[0009] Furthermore, a modulation mode switching synchronous rectification soft switch step-down constant voltage power supply, the sampling unit includes: A current sampling unit, used for sampling the inductor current signal and output current of the modulation mode switching synchronous rectification soft switching buck constant voltage power supply; The voltage sampling unit is used to sample the output voltage of the modulation mode switching synchronous rectification soft switching buck constant voltage power supply.

[0010] Furthermore, a synchronous rectification soft switching step-down constant voltage power supply, the feedback unit comprises: An isolated feedback device, used for feeding back the output of the current and voltage sampling units to the main controller, wherein the input end thereof is respectively connected to the output end of the current sampling unit and the output end of the voltage sampling unit, and the output end thereof is connected to the input end of the ADC; The compensation signal generating unit is used to adjust the signal fed back by the isolated feedback device and then output it to the isolated driving unit to obtain PWM and PFM signals for adjusting the switch tube.

[0011] Furthermore, in a modulation mode switching synchronous rectification soft switch step-down constant voltage power supply, the compensation signal generating unit includes: Soft start unit, error amplifier, PWM compensator, limiter, PFM compensator, modulation mode switcher, output overvoltage protection unit, inductor overcurrent protection unit; Among them, the voltage feedback signal is respectively input to the PWM compensator and the PFM compensator through the error amplifier. After the signal passes through the limiter, it is selected by the modulation mode switcher to be input to the DSP square wave signal driving unit, and finally the square wave control signal is output; when the system is powered on, the voltage feedback signal is very small, which causes the compensator output signal to be too large, resulting in an output voltage overshoot. The soft start unit is used to simulate the system voltage feedback signal at power-on, so that it rises in a certain linear trend within a certain period of time; the modulation mode switcher is used to detect the current system load condition, and switches to the PFM compensator output when the load is light, and switches to the PWM compensator output when the load is heavy; the output overvoltage protection unit and the inductor overcurrent protection unit are respectively used to detect whether the output voltage is overvoltage and whether the inductor current exceeds the design margin. When the above signals exceed a certain threshold, the above protection units output signals to the square wave generator to limit the output voltage or the inductor current.

[0012] Furthermore, in a modulation mode switching synchronous rectification soft switch step-down constant voltage power supply, the isolation driving unit includes: DSP square wave signal driving unit generates low voltage main switch tube signal and synchronous rectifier tube signal; The isolation drive signal generating unit is used for electrically isolating the DSP system from the main topology structure, and converting the low-voltage control signal generated by the DSP system into the main switch tube control signal and the synchronous rectifier tube control signal to control the switching state of the main switch tube Q1 and the synchronous rectifier tube Q2, and converting it into a square wave signal sufficient to drive the switching state of the switch tube.

[0013] Furthermore, in a modulation mode switching synchronous rectification soft switch step-down constant voltage power supply, the drive signal generating unit includes: Square wave signal generating unit, dead zone signal generating unit; The square wave signal generating unit includes a sawtooth wave signal generator, a comparator, and a compensation signal input. The positive input port of the sawtooth wave signal generator is connected to the negative input port of the comparator, the compensation signal input port is connected to the positive input port of the comparator, and the output port of the square wave signal generating unit outputs a square wave switch signal to the dead zone signal generating unit; The dead zone signal generating unit includes a monostable trigger, a first analog signal delay unit, a second analog signal delay unit, a first dual-channel input AND gate, and a second dual-channel input AND gate. The output end of the square wave signal generating unit is connected to the rising edge trigger end of the monostable trigger, the falling edge trigger end of the monostable trigger is connected to the reference ground, the in-phase output end of the monostable trigger is connected to the input port of the first analog signal delay unit and the first input channel of the first AND gate, the second input channel of the first AND gate is connected to the output port of the first analog signal delay unit, at this time, the output signal of the first AND gate is the main switch tube control signal with dead zone control; similarly, the inverting output end of the monostable trigger is connected to the input port of the second analog signal delay unit and the first input channel of the second AND gate, the second input channel of the second AND gate is connected to the output port of the second analog signal delay unit, at this time, the output signal of the second AND gate is the synchronous rectifier tube control signal with dead zone control. Furthermore, in a modulation mode switching synchronous rectification soft switching step-down constant voltage power supply, the gate drive voltage of the main switch tube and the synchronous rectifier tube in the drive signal generating unit is 12V when they are turned on, and the gate drive voltage of the main switch tube and the synchronous rectifier tube when they are turned off is 0V.

[0014] The beneficial effects of the present invention are: 1. The present invention replaces the main switch tube in the step-down constant voltage power supply with a GaN HEMT, replaces the synchronous rectifier tube with a SiC HEMT, and utilizes the characteristics of low on-resistance and low charging capacitance of the GaN HEMT and the reverse fast recovery characteristics of the SiC HEMT body diode to achieve miniaturization and high efficiency of the step-down constant voltage power supply.

[0015] 2. The modulation mode switching synchronous rectification soft switch step-down constant voltage power supply of the embodiment of the present invention realizes zero voltage turn-on of the synchronous rectifier tube by controlling the dead time, reduces the conduction loss of the step rectifier tube, and realizes high efficiency of the power supply.

[0016] 3. The modulation mode switching of the synchronous rectification soft-switch step-down constant voltage power supply of the embodiment of the present invention is controlled by dual modulation modes to achieve high efficiency and low ripple characteristics under various load conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The overall structural diagram of a modulation mode switching synchronous rectification soft switch step-down constant voltage power supply of the present invention is shown.

[0018] Figure 2 The present invention is a schematic diagram of a feedback unit of a modulation mode switching synchronous rectification soft switch step-down constant voltage power supply.

[0019] Figure 3The present invention is a schematic diagram of a driving signal generating unit of a modulation mode switching synchronous rectification soft switching step-down constant voltage power supply.

[0020] Figure 4 The present invention discloses a timing diagram of a single-cycle driving signal under PFM modulation under light load of a modulation mode switching synchronous rectification soft-switch buck constant voltage power supply and a corresponding synchronous rectifier tube zero voltage conduction waveform diagram.

[0021] Figure 5 The present invention discloses a timing diagram of a single-cycle drive signal using PWM modulation under heavy load conditions for a modulation mode switching synchronous rectification soft-switch step-down constant voltage power supply and a corresponding synchronous rectifier tube zero-voltage conduction waveform diagram.

[0022] Figure 6 The present invention is a simulation waveform diagram of the output current and output voltage of a strong regulation mode switching synchronous rectification soft switch step-down constant voltage power supply under light load.

[0023] Figure 7 The present invention provides a simulated waveform diagram of the output current and output voltage of a strong regulation mode switching synchronous rectification soft switch step-down constant voltage power supply when it is overloaded.

[0024] Figure 8 The present invention is a simulated waveform diagram of the output current and output voltage of a strong regulation mode switching synchronous rectification soft switch buck constant voltage power supply when load switching. DETAILED DESCRIPTION

[0025] In order to facilitate the understanding of the present invention, the present invention will be described in more detail below with reference to the relevant drawings. The drawings provide embodiments of the present invention, but the present invention can be implemented in different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0026] like Figure 1 As shown, the modulation mode switching synchronous rectification soft switch step-down constant voltage power supply in the embodiment of the present invention includes: a DC power supply, a power inductor L1, a main switch tube Q1, a synchronous rectifier tube Q2, an input capacitor C IN , output capacitor C OUT , output filter inductor L f , output filter capacitor C f , power inductor current sampling resistor R S1 , output current sampling resistor R S2 , load resistance R OUT and control circuits.

[0027] The DC power supply VDC is used to power the entire circuit, and its positive electrode is connected to the input capacitor C IN, the drain of the main switch tube Q1 is connected, and the main switch tube Q 1源极 It is connected to the left end of the power inductor L1 and the drain of the synchronous rectifier Q2. The source of the synchronous rectifier Q2 is connected to the power inductor current sampling resistor R S1 Connected to measure the power inductor current sampling resistor R S1 The voltage across both ends can be used to obtain the waveform of the power inductor current when it decreases.

[0028] The right end of the power inductor L1 is connected to the output capacitor C OUT Positive pole and output filter inductor L f Left end, output filter inductor L f The right end is connected to the output filter capacitor C f With load resistance R OUT Positive electrode, load resistance R OUT The negative terminal is connected to the output current sampling resistor R S2 Then connect it to the reference ground and measure the output current sampling resistor R S2 The voltage across the two ends can be used to obtain the system output current waveform.

[0029] The control circuit is used to provide a main switch tube control signal and a synchronous rectifier tube control signal to control the switch states of the main switch tube Q1 and the synchronous rectifier tube Q2 respectively. The control circuit includes: a sampling unit, a feedback unit, and a driving unit. The sampling unit is used to sample the output voltage, the output current, and the power inductor current. The sampled current and voltage signals are output to the feedback unit, and are adjusted according to the signal obtained by the sampling unit to obtain a compensation signal. Finally, the main switch tube control signal and the synchronous rectifier tube control signal are generated according to the compensation signal obtained by the feedback unit.

[0030] The schematic diagram of the feedback unit of the modulation mode switching synchronous rectification soft switch buck constant voltage power supply is as follows: Figure 2 As shown, after the current and voltage signals are collected by the sampling unit, they are output to the isolated feedback device in the feedback unit for electrical isolation. For the PWM modulation end, the reference voltage is connected to the positive input end of the adder, the feedback voltage is connected to the negative input end of the adder, the output end of the adder is connected to the input end of the PWM compensator, and the compensation signal is output by the limiter; for the PFM modulation end, the reference voltage is connected to the positive input end of the comparator, the feedback voltage is connected to the negative input end of the adder, and the output end of the comparator is connected to the input end of the PFM compensator.

[0031] The schematic diagram of the driving signal generating unit of the modulation mode switching synchronous rectification soft switch buck constant voltage power supply is as follows: Figure 3 As shown, it is used to convert the compensation signal obtained by the feedback unit into a main switch tube control signal and a synchronous rectifier tube control signal.

[0032] The single-cycle driving timing signal of the modulation mode switching synchronous rectification soft switch buck constant voltage power supply and the corresponding main switch tube zero voltage turn-on waveform are shown in the figure. Figure 4 As shown, the main switch control signal is used to control the main switch Q1. When Q1 is turned on, the DC power supply VDC charges the power inductor and output capacitor, and the load resistor R OUT Power supply, synchronous rectifier Q2 is in the off state, power inductor current sampling resistor R S1 No current flows. The modulation mode switching synchronous rectification soft switch step-down constant voltage power supply improves the problem of synchronous rectifier tube switch conduction loss.

[0033] The above implementation modes are merely exemplary descriptions of the present invention and do not limit its protection scope. Those skilled in the art may also make partial changes thereto and may change the selection of the regulator according to actual conditions to generate a better compensation signal. Any form of equivalent replacement that conforms to the spirit of the invention falls within the protection scope of the present invention.

Claims

1. A modulation mode switching synchronous rectification soft switch step-down constant voltage power supply, characterized in that: include: It includes an input filter circuit, a power inductor L1, an output filter circuit, a main switch tube Q1, a synchronous rectifier tube Q2 and a control circuit; The input filter circuit consists of a DC power supply, an input capacitor C IN The positive electrode of the DC power supply is connected to the positive electrode of the input capacitor, and the negative electrode of the DC power supply and the negative electrode of the input capacitor are connected to the reference ground; The left end of the power inductor L1 is connected to the source of the main switch tube Q1 and the drain of the synchronous rectifier tube Q2, the right end of the power inductor L1 is connected to the positive electrode of the output capacitor, the drain of the main switch tube Q1 is connected to the positive electrode of the input capacitor, and the source of the synchronous rectifier tube Q2 is connected to the positive electrode of the power inductor current sampling resistor R S1 Access reference ground; The output filter circuit consists of an output capacitor C OUT , output filter inductor L f , output filter capacitor C f Composition, output filter inductor L f The left side is connected to the output capacitor C OUT Positive pole, output filter inductor L f The right side is connected to the output filter capacitor C f Positive electrode, output capacitor C OUT With the output filter capacitor C f The negative electrode is connected to the reference ground. The control circuit is used to provide a main switch tube control signal and a synchronous rectifier tube control signal to control the switch states of the main switch tube Q1 and the synchronous rectifier tube Q2 respectively, so as to realize zero voltage conduction of the synchronous rectifier tube Q2, wherein the control circuit includes: A sampling unit, used for sampling the output voltage and current signals of the modulation mode switching synchronous rectification soft switching buck constant voltage power supply; A feedback unit, which adjusts according to the signal obtained by the sampling unit to obtain a compensation signal; The driving unit generates a main switch tube control signal and a synchronous rectifier tube control signal according to the compensation signal obtained by the feedback unit.

2. According to claim 1, the modulation mode switching synchronous rectification soft switch step-down constant voltage power supply is characterized in that: The main switch tube Q1 must be a gallium nitride (GaN) high electron mobility transistor (HEMT) and the synchronous rectifier tube Q2 must be a silicon carbide (SiC) high electron mobility transistor (HEMT) to achieve high efficiency and miniaturization of the modulation mode switching synchronous rectification soft switching step-down constant voltage power supply.

3. The modulation mode switching synchronous rectification soft switch step-down constant voltage power supply according to claim 1, characterized in that: The sampling unit of the control circuit comprises: A current sampling unit, used for sampling the input and output currents of the modulation mode switching synchronous rectification soft switching buck constant voltage power supply; The voltage sampling unit is used to sample the input and output voltages of the modulation mode switching synchronous rectification soft switching buck constant voltage power supply.

4. The modulation mode switching synchronous rectification soft switch step-down constant voltage power supply according to claim 1, characterized in that: The feedback unit of the control circuit comprises: An isolated feedback device, used for feeding back the output of the current and voltage sampling units to the main controller, wherein the input end thereof is respectively connected to the output end of the current sampling unit and the output end of the voltage sampling unit, and the output end thereof is connected to the positive input end of the first adder; The compensation signal generating unit is used to adjust the signal fed back by the isolated feedback device and then output it to the driving unit to obtain a control signal for adjusting the switch tube.

5. The modulation mode switching synchronous rectification soft switch step-down constant voltage power supply according to claim 1, characterized in that: The driving unit of the control circuit comprises: A driving signal generating unit, used to generate the main switch tube control signal and the synchronous rectifier tube control signal to control the switching state of the main switch tube Q1 and the synchronous rectifier tube Q2; The PWM driving unit converts the main switch tube control signal and the synchronous rectifier tube control signal generated by the driving signal generating unit into a square wave signal that can control the switching state of the switch tube, and is characterized in that the gate driving voltage when the main switch tube and the synchronous rectifier tube are turned on is 12V, and the gate driving voltage when the main switch tube and the synchronous rectifier tube are turned off is 0V.

6. The modulation mode switching synchronous rectification soft switch step-down constant voltage power supply according to claim 4, characterized in that: The compensation signal generating unit includes: a soft start unit, an error amplifier, a PWM compensator, a limiter, a PFM compensator, a modulation mode switcher, an output overvoltage protection unit, and an inductor overcurrent protection unit; Among them, the voltage feedback signal is respectively input to the PWM compensator and the PFM compensator through the error amplifier. After the signal passes through the limiter, it is selected by the modulation mode switcher to be input to the DSP square wave signal driving unit, and finally the square wave control signal is output; when the system is powered on, the voltage feedback signal is very small, which causes the compensator output signal to be too large, resulting in an output voltage overshoot. The soft start unit is used to simulate the system voltage feedback signal at power-on, so that it rises in a certain linear trend within a certain period of time; the modulation mode switcher is used to detect the current system load condition, and switches to the PFM compensator output when the load is light, and switches to the PWM compensator output when the load is heavy; the output overvoltage protection unit and the inductor overcurrent protection unit are respectively used to detect whether the output voltage is overvoltage and whether the inductor current exceeds the design margin. When the above signals exceed a certain threshold, the above protection units output signals to the square wave generator to limit the output voltage or the inductor current.

7. The modulation mode switching synchronous rectification soft switch step-down constant voltage power supply according to claim 5, characterized in that: The driving signal generating unit includes: a square wave signal generating unit and a dead zone signal generating unit; The square wave signal generating unit includes a sawtooth wave signal generator, a comparator, and a compensation signal input. The positive input port of the sawtooth wave signal generator is connected to the negative input port of the comparator, the compensation signal input port is connected to the positive input port of the comparator, and the output port of the square wave signal generating unit outputs a square wave switch signal to the dead zone signal generating unit; The dead zone signal generating unit includes a monostable trigger, a first analog signal delay unit, a second analog signal delay unit, a first dual-channel input AND gate, and a second dual-channel input AND gate. The output end of the square wave signal generating unit is connected to the rising edge trigger end of the monostable trigger, the falling edge trigger end of the monostable trigger is connected to the reference ground, the in-phase output end of the monostable trigger is connected to the input port of the first analog signal delay unit and the first input channel of the first AND gate, the second input channel of the first AND gate is connected to the output port of the first analog signal delay unit, at this time, the output signal of the first AND gate is the main switch tube control signal with dead zone control; similarly, the inverting output end of the monostable trigger is connected to the input port of the second analog signal delay unit and the first input channel of the second AND gate, the second input channel of the second AND gate is connected to the output port of the second analog signal delay unit, at this time, the output signal of the second AND gate is the synchronous rectifier tube control signal with dead zone control.

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