Gallium Nitride Charger Based on 494PWM Chip

Abstract

This application relates to the field of switching power supply technology and discloses a gallium nitride (GaN) charger based on a 494 PWM chip. The charger includes a power board, a rectifier circuit module, a half-bridge GaN driver module, a transformer, a 494 chip control module, a totem-pole driver module, an isolation driver transformer, a full-wave rectifier module, a filter circuit module, and a conversion circuit module. The core of this application is that the 494 chip control module generates a PWM signal, which is then amplified by the totem-pole driver module and electrically isolated and coupled by the isolation driver transformer before driving two GaN transistors in the half-bridge topology to switch alternately at high frequency. This application fully utilizes the high-speed switching characteristics of GaN devices, enabling the charger to operate at higher frequencies. This increases the power level to the kilowatt level while reducing switching losses and the size of magnetic components, achieving high power density and high overall conversion efficiency.

Description

Technical Field

[0001] This application relates to the field of switching power supply technology, specifically a gallium nitride charger based on a 494PWM chip. Background Technology

[0002] Most existing chargers employ hard-switching topologies. In hard-switching mode, switching devices (such as silicon-based MOSFETs) experience significant voltage-current stress during turn-on and turn-off, resulting in substantial switching losses. This directly hinders the increase of switching frequency, leading to longer turn-on and turn-off times and slower switching speeds. The lower switching frequency limits the reduction in size of magnetic components such as transformers and inductors, resulting in bulky chargers; while the slower switching speed and longer switching time lead to persistently high switching losses and overall low charger efficiency. As fast charging technology advances towards higher power, these problems become particularly prominent in applications requiring high power density and high efficiency. Summary of the Invention

[0003] The purpose of this application is to provide a gallium nitride charger based on a 494PWM chip to solve the technical problems mentioned in the background art.

[0004] To achieve the above objectives, this application discloses the following technical solution: a gallium nitride charger based on a 494PWM chip, comprising:

[0005] Power board;

[0006] The rectifier circuit module has its input terminal connected to the AC input terminal of the power board, and is used to rectify the AC input into DC power.

[0007] The input terminal of the gallium nitride driver module with half-bridge topology is connected to the DC output terminal of the rectifier circuit module;

[0008] Transformer T1, the primary end of which is connected to the output end of the gallium nitride drive module;

[0009] The 494 chip control module is used to generate PWM control signals and sample and adjust the output voltage and output current of the charger.

[0010] The totem pole driving module has its input terminal connected to the PWM signal output terminal of the 494 chip control module;

[0011] The isolation drive transformer T2 has its primary end connected to the output end of the totem pole drive module and its secondary end connected to the control end of the gallium nitride drive module, and is used to isolate and drive the PWM control signal.

[0012] The full-wave rectifier module has its input terminal connected to the secondary terminal of the transformer T1, and is used to perform full-wave rectification on the transformed AC power.

[0013] The filter circuit module has its input terminal connected to the output terminal of the full-wave rectifier module, and its output terminal is controlled by a relay FJH, which is used to filter and control the output of the rectified voltage.

[0014] The conversion circuit module is connected to the output terminal of the filter circuit module and is used to control the indicator light and fan based on the output current sampling.

[0015] Optionally, the rectifier circuit module includes fuse F1, fuse F2, thermistor RTH3, thermistor RTH4, thermistor RTH5, ​​common mode inductor L1, X capacitor C1, X capacitor C2, Y capacitor C5, Y capacitor C6, Y capacitor C13 and Y capacitor C19.

[0016] The AC input passes sequentially through fuses F1 and F2 connected in parallel, and the thermistors RTH3, RTH4, and RTH5 connected in parallel, before being connected to the input terminal of the common-mode inductor L1. X capacitor C1 and resistor R0 are connected in parallel between pins 2 and 4 of the common-mode inductor L1, and X capacitor C2 is connected in parallel between pins 1 and 3 of the common-mode inductor L1. Y capacitors C5 and C6 are connected between the input live wire and ground, and Y capacitors C13 and C19 are connected between the input neutral wire and ground.

[0017] Optionally, the rectifier circuit module further includes a common-mode inductor L0, a rectifier bridge BG1, an electrolytic capacitor C8, an electrolytic capacitor C8_2, and a DC blocking capacitor C9.

[0018] The output terminal of the common mode inductor L1 is connected to the input terminal of the common mode inductor L0; the AC input terminal of the rectifier bridge BG1 is connected to the output terminal of the common mode inductor L0; the DC output positive terminal of the rectifier bridge BG1 is filtered by the electrolytic capacitor C8 and electrolytic capacitor C8_2, and then passes through the DC blocking capacitor C9, and serves as the DC output positive terminal of the rectifier circuit module.

[0019] Optionally, the 494 chip control module includes a 494 chip U1;

[0020] Pin 9 of the 494 chip U1 is connected to the base of transistors Q3 and Q7 in the totem pole driver module via resistor R13, for outputting the first PWM signal;

[0021] Pin 10 of the 494 chip U1 is connected to the base of transistors Q4 and Q8 in the totem pole driver module via resistor R14, for outputting a second PWM signal;

[0022] Pin 1 of the 494 chip U1 is connected to the output voltage sampling circuit for adjusting the output voltage;

[0023] Pin 15 of the 494 chip U1 is connected to the output current sampling circuit for adjusting the output current.

[0024] Optionally, the totem pole driving module includes transistor Q3, transistor Q4, transistor Q7, transistor Q8, diode D5, diode D1, diode D2, diode D8, diode D7, and diode D6;

[0025] The emitters of transistors Q3 and Q7 are connected together to form the first drive output terminal, which is connected to pin 3 of the primary side of the isolation drive transformer T2.

[0026] The emitters of transistors Q4 and Q8 are connected together to form the second drive output terminal, which is connected to pin 4 of the primary side of the isolation drive transformer T2.

[0027] The positive terminal of diode D5 is connected to a +12V power supply, and the negative terminal is connected to the collector of transistor Q3; diode D1 is connected between the base and collector of transistor Q3; diode D2 is connected between the emitter and collector of transistor Q7.

[0028] The diode D8 is connected between the base and collector of the transistor Q4; the diode D7 is connected between the emitter and collector of the transistor Q8; the anode of the diode D6 is connected to the collector of the transistor Q8, and the cathode is grounded.

[0029] Optionally, the gallium nitride drive module includes gallium nitride transistors Q1 and Q2, resistors R15, R16, R24, and R28, ferrite beads FB1 and FB2, bipolar diodes ZD1 and ZD2, and capacitors C30 and C35.

[0030] The drain of the gallium nitride transistor Q1 is connected to the positive DC output of the rectifier circuit module. Its gate is connected to pin 1 of the secondary side of the isolation drive transformer T2 via resistor R15 and ferrite bead FB1. Its source is connected to the drain of the gallium nitride transistor Q2 and pin 2 of the primary side of the transformer T1. Resistor R24 ​​is connected between the gate and source of the gallium nitride transistor Q1. Capacitor C30 is connected in parallel between the drain and source of the gallium nitride transistor Q1. Bipolar diode ZD1 is connected between the gate drive circuit and the source of the gallium nitride transistor Q1.

[0031] The gate of the gallium nitride transistor Q2 is connected to pin 5 of the secondary side of the isolation drive transformer T2 via the resistor R16 and the ferrite bead FB2, and its source is grounded; the resistor R28 is connected between the gate and the source of the gallium nitride transistor Q2; the capacitor C35 is connected in parallel between the drain and the source of the gallium nitride transistor Q2; and the bipolar diode ZD2 is connected between the gate drive circuit and the source of the gallium nitride transistor Q2.

[0032] Optionally, the full-wave rectifier module includes silicon carbide diode D15 and silicon carbide diode D16;

[0033] The positive terminal of the silicon carbide diode D15 is connected to pin 3 of the secondary winding of the transformer T1, and the positive terminal of the silicon carbide diode D16 is connected to pin 5 of the secondary winding of the transformer T1. The negative terminals of the silicon carbide diodes D15 and D16 are connected together, serving as the positive output terminal of the full-wave rectifier module.

[0034] Optionally, the filter circuit module includes an inductor L2, an electrolytic capacitor C17, an electrolytic capacitor C21, a capacitor C18, a resistor R44, and the relay FJH;

[0035] The input terminal of the inductor L2 is connected to the positive output terminal of the full-wave rectifier module; the electrolytic capacitor C17, the electrolytic capacitor C21, the capacitor C18 and the resistor R44 are connected in parallel between the output terminal of the inductor L2 and ground; the contacts of the relay FJH are connected in series between the output terminal of the inductor L2 and the final positive output terminal of the charger.

[0036] Optionally, the conversion circuit module includes operational amplifier U2A, operational amplifier U2B, indicator LED2, and fan M1;

[0037] The sampling input terminals of the operational amplifiers U2A and U2B are connected to the output current sampling circuit. The output terminals of the operational amplifiers U2A and U2B control the indicator LED2 to display different colors and control the fan M1 to turn on and off according to the signal level collected by the output current sampling circuit.

[0038] Optionally, the 494 chip control module drives the gallium nitride transistors Q1 and Q2 in the half-bridge topology to conduct alternately at high frequency through the totem pole driving module and the isolation driving transformer T2.

[0039] Beneficial Effects: The gallium nitride (GaN) charger based on the 494PWM chip in this application, by employing a half-bridge GaN topology controlled by the 494 chip and driven by a totem pole and isolation transformer, fully leverages the inherent advantages of GaN transistors—supporting extremely high switching frequencies and extremely short switching times—and reduces switching losses. This allows the circuit to operate safely and efficiently at higher frequencies, thereby reducing the size and weight of magnetic components such as transformers and achieving high power density. Ultimately, the charger in this application achieves higher overall conversion efficiency while increasing power levels, resolving the contradiction between efficiency, size, and power in traditional solutions. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1 A circuit schematic diagram of a gallium nitride charger based on a 494PWM chip provided for an embodiment of this application;

[0042] Figure 1-1 for Figure 1 A partial schematic diagram of the first part;

[0043] Figure 1-2 for Figure 1 Partial schematic diagram of the second section;

[0044] Figure 2 The circuit schematic diagram of the rectifier circuit module provided in the embodiments of this application;

[0045] Figure 3 The circuit schematic diagram of the 494 chip control module provided in the embodiments of this application;

[0046] Figure 4The circuit schematic diagram of the totem pole driving module provided in the embodiments of this application;

[0047] Figure 5 A circuit schematic diagram of a gallium nitride driver module provided in an embodiment of this application;

[0048] Figure 6 A circuit schematic diagram of a full-wave rectifier module provided in an embodiment of this application;

[0049] Figure 7 The circuit schematic diagram of the filter circuit module provided in the embodiments of this application;

[0050] Figure 8 The circuit schematic diagram is provided for the conversion circuit module in the embodiment of this application. Detailed Implementation

[0051] To facilitate understanding of the technical solutions provided in the embodiments of this application, the background technology involved in the embodiments of this application will be described below.

[0052] Existing high-power hard-switching chargers are generally limited by the performance of silicon-based power devices, and their switching frequencies are typically restricted to low levels (e.g., below 100kHz). This lower switching frequency directly results in larger and heavier energy storage and filtering components such as transformers and inductors, restricting the charger's power density and miniaturization. More importantly, during hard switching, the switching transistors generate significant switching losses when they turn on when the voltage is not zero (turn-on loss) or turn off when the current is not zero (turn-off loss). These losses increase linearly with increasing switching frequency, creating a dilemma for traditional solutions in balancing high efficiency and high power density: increasing the frequency reduces component size, but switches losses rise sharply, leading to a decrease in overall efficiency; using a low frequency to maintain efficiency results in a bulky design.

[0053] Therefore, those skilled in the art have long faced a clear technical dilemma: how to construct a charger topology that can operate safely and reliably at frequencies far exceeding those of traditional hard-switching circuits, thereby achieving a balance between high efficiency and small size while increasing power levels. The essence of this dilemma lies in the fact that simply replacing the switching devices (such as gallium nitride transistors) with faster ones is insufficient; a matching drive and control architecture that can fully leverage their high-speed potential must be designed. Traditional direct drive or simple optocoupler-isolated drive methods based on silicon devices often suffer from insufficient drive capability, poor signal integrity, high common-mode noise interference, and inaccurate switching timing when used to drive gallium nitride devices. These methods cannot ensure stable and efficient operation of gallium nitride devices at frequencies of hundreds of kHz or even MHz, thus preventing the performance advantages of gallium nitride from being translated into actual advantages for the overall product.

[0054] This embodiment provides a systematic solution based on this principle.

[0055] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application. Secondly, in this document, the term "comprising" is intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements, but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0056] This embodiment provides a gallium nitride charger based on a 494PWM chip, combined with... Figure 1 , Figure 1-1 and Figure 1-2 As shown (it should be noted that, to avoid issues related to display size and resolution, ...), Figure 1 There are unclear aspects in the accompanying drawings used in this embodiment. Figure 1-1 What is shown is Figure 1 The lower half of the part, Figure 1-2 What is shown is Figure 1 The upper part of the part, and Figure 1-1 and Figure 1-2 There are overlapping parts, and these overlapping parts (including but not limited to) Figure 1-1 and Figure 1-2 The "T2" section (etc.) aims to clarify Figure 1-1 and Figure 1-2 How to form after splicing Figure 1 The complete view shown includes:

[0057] Power board;

[0058] The rectifier circuit module has its input terminal connected to the AC input terminal of the power board, and is used to rectify the AC input into DC power.

[0059] The input terminal of the gallium nitride driver module in the half-bridge topology is connected to the DC output terminal of the rectifier circuit module;

[0060] Transformer T1, the primary end of which is connected to the output end of the gallium nitride drive module;

[0061] The 494 chip control module is used to generate PWM control signals and sample and adjust the output voltage and output current of the charger.

[0062] The totem pole driver module has its input terminal connected to the PWM signal output terminal of the 494 chip control module;

[0063] The isolation drive transformer T2 has its primary end connected to the output end of the totem pole drive module and its secondary end connected to the control end of the gallium nitride drive module, which is used to isolate and drive the PWM control signal.

[0064] The full-wave rectifier module has its input terminal connected to the secondary terminal of transformer T1 and is used to perform full-wave rectification on the transformed AC power.

[0065] The filter circuit module has its input terminal connected to the output terminal of the full-wave rectifier module, and its output terminal is controlled by the relay FJH. It is used to filter the rectified voltage and control the output.

[0066] The conversion circuit module, connected to the output of the filter circuit module, is used to control the indicator lights and fan based on the output current sampling.

[0067] In this charger, the power board provides auxiliary power (e.g., +12V) for the entire system. Alternating current (e.g., 220V) is converted to high-voltage direct current (DC) by a rectifier module. This DC power supplies a half-bridge topology composed of gallium nitride transistors Q1 and Q2. The 494 chip control module acts as the system's "brain," generating two complementary PWM square wave signals based on feedback sampling information. These two signals are first amplified by a totem-pole driver module to enhance driving capability, then electrically isolated and coupled by an isolation driver transformer T2, ultimately driving the two gallium nitride transistors on the half-bridge to alternately turn on and off at high speed and precision. Thus, the high-voltage DC is "chopped" into a high-frequency AC square wave, which is then stepped down by transformer T1. The stepped-down AC is converted to low-voltage DC by a full-wave rectifier module, then smoothed by a filter module, and finally output controlled by a relay FJH. The conversion circuit module monitors the output status in real time, controlling indication and heat dissipation.

[0068] Based on the above, this embodiment organically combines the mature 494 control chip, the classic and powerful totem-pole push-pull driver, reliable magnetic isolation, and cutting-edge gallium nitride power devices. The totem-pole circuit solves the problem of current drive capability for high-speed PWM signals, while the isolation transformer simultaneously solves the problems of electrical isolation between high and low voltage sides and the generation of two complementary drive signals, jointly providing a precise, powerful, and safe drive environment for gallium nitride devices to leverage their high-speed switching advantages. This enables the entire power conversion link to operate stably at frequencies far higher than traditional hard-switching circuits (e.g., 200kHz to 500kHz or higher), resulting in the dual benefits of miniaturized magnetic components and reduced switching losses, achieving a balance between high efficiency and high power density.

[0069] To ensure the charger's safe and reliable connection to the power grid and to suppress electromagnetic interference, AC input processing is necessary. Therefore, as an optional implementation method in this embodiment, such as... Figure 2 As shown, the rectifier circuit module includes fuse F1, fuse F2, thermistor RTH3, thermistor RTH4, thermistor RTH5, ​​common mode inductor L1, X capacitor C1, X capacitor C2, Y capacitor C5, Y capacitor C6, Y capacitor C13 and Y capacitor C19.

[0070] The AC input passes through fuses F1 and F2 in parallel, and thermistors RTH3, RTH4, and RTH5 in parallel before being connected to the input terminal of common-mode inductor L1. X capacitor C1 and resistor R0 are connected in parallel between pins 2 and 4 of common-mode inductor L1, and X capacitor C2 is connected in parallel between pins 1 and 3 of common-mode inductor L1. Y capacitors C5 and C6 are connected between the input live wire and ground, and Y capacitors C13 and C19 are connected between the input neutral wire and ground.

[0071] In practice, fuses F1 and F2 are glass or ceramic tube fuses, with rated current set according to the overall power (e.g., 10A), used for overcurrent protection. Parallel connection improves reliability. Thermistors RTH3, RTH4, and RTH5 are negative temperature coefficient (NTC) thermistors; their cold-state resistance (e.g., 5 ohms) effectively suppresses surge current during power-on, and their resistance becomes very small after normal operation due to heat, reducing losses. They are used in parallel to share current and power consumption. Common-mode inductor L1 consists of two identical coils wound on a single magnetic core, used to filter common-mode electromagnetic interference. X capacitors C1 and C2 are connected across the AC lines to filter differential-mode interference, with resistor R0 connected in parallel across C1 as a bleed resistor. Y capacitors C5, C6, C13, and C19 are connected across the live wire-to-ground and neutral wire-to-ground respectively, used to filter common-mode interference; their capacitance values ​​must comply with safety specifications. In practical applications, the specific models and parameters of these protection and filtering components can be adjusted according to EMC standard requirements, and this application embodiment does not limit this.

[0072] Based on the above, the rectifier circuit module constitutes the first stage of EMI filtering and input protection for the charger. The fuse and NTC thermistor provide necessary electrical safety protection and soft-start functionality. The π-type filter, composed of a common-mode inductor and X / Y capacitors, effectively suppresses interference from the power grid and conducted electromagnetic interference generated during charger operation and fed back to the power grid, ensuring the product meets electromagnetic compatibility requirements and creating a clean power supply environment for the stable operation of subsequent circuits.

[0073] The filtered AC power needs to be converted into stable high-voltage DC power for use by subsequent high-frequency switching circuits. Therefore, based on the aforementioned rectifier circuit module, as a further optional implementation of this embodiment, the rectifier circuit module also includes a common-mode inductor L0, a rectifier bridge BG1, an electrolytic capacitor C8, an electrolytic capacitor C8_2, and a DC blocking capacitor C9.

[0074] The output terminal of common mode inductor L1 is connected to the input terminal of common mode inductor L0; the AC input terminal of rectifier bridge BG1 is connected to the output terminal of common mode inductor L0; the DC output positive terminal of rectifier bridge BG1 is filtered by electrolytic capacitor C8 and electrolytic capacitor C8_2, and then passes through DC blocking capacitor C9 before serving as the DC output positive terminal of the rectifier circuit module.

[0075] In specific implementation, the common-mode inductor L0 is the second-stage common-mode inductor, which, together with L1, forms a more efficient EMI filtering network. The rectifier bridge BG1 can be an integrated rectifier bridge stack, internally composed of four silicon rectifier diodes forming a full-bridge rectifier circuit to convert AC to pulsating DC. Electrolytic capacitors C8 and C8_2 are high-voltage electrolytic capacitors (e.g., 450V rated voltage), connected in parallel between the positive and negative terminals of the rectifier bridge's DC output, used to store energy and smooth the pulsating DC after rectification, forming a relatively stable high-voltage DC bus (e.g., approximately 300V). The DC blocking capacitor C9 is a film capacitor or CBB capacitor, connected in series in the positive path of the DC bus, its function being to prevent the DC component from causing core saturation of the subsequent half-bridge transformer T1. In practical applications, the current specifications of the rectifier bridge, the capacitance and voltage rating of the electrolytic capacitors, and the capacitance value of the DC blocking capacitor can be selected according to the input voltage and output power; this embodiment does not limit these selections.

[0076] Based on the above, this rectifier circuit module also completes the power conversion from AC to DC. The rectifier bridge and electrolytic capacitors constitute a typical rectifier and filter circuit, establishing a high-voltage DC bus. The DC blocking capacitor C9 is one of the key components of the half-bridge topology. It ensures that the voltage applied to the primary winding of the transformer is a pure AC square wave, avoiding transformer magnetic saturation and overheating problems caused by DC bias, and ensuring the stable and efficient operation of the power conversion core.

[0077] To achieve precise control and regulation of the power conversion process, a stable control core is required. Therefore, as an optional implementation method in this embodiment, such as... Figure 3 As shown, the 494 chip control module includes a 494 chip U1;

[0078] Pin 9 of the 494 chip U1 is connected to the base of transistors Q3 and Q7 in the totem pole driver module through resistor R13 to output the first PWM signal;

[0079] Pin 10 of the 494 chip U1 is connected to the base of transistors Q4 and Q8 in the totem pole driver module through resistor R14 to output the second PWM signal;

[0080] Pin 1 of the 494 chip U1 is connected to the output voltage sampling circuit for adjusting the output voltage;

[0081] Pin 15 of the 494 chip U1 is connected to the output current sampling circuit for adjusting the output current.

[0082] In practical implementation, the 494 chip (such as TL494, KA7500, etc.) is a classic voltage-mode PWM control chip. Its peripheral circuitry includes a Vcc pin (connected to +12V) to power the chip, a Vref pin to provide a reference voltage, and an RT / CT network to set the oscillation frequency. Two error amplifiers inside the chip are used for voltage loop and current loop control, respectively. Pin 1 (the non-inverting input of error amplifier 1) is connected to the final output voltage (OUT) of the charger via a resistor divider network to sample the output voltage. Pin 15 (the non-inverting input of error amplifier 2) is connected to the output current sampling circuit. In this embodiment, the output current sampling circuit mainly includes a current sampling resistor (SENSOR1 in the figure) connected in series in the DC output circuit of the charger, used to convert the output current into a voltage signal. This voltage signal is sent via corresponding lines to pin 15 of the 494 chip U1 and the sampling inputs of operational amplifiers U2A and U2B in the subsequent conversion circuit module for processing. Pin 1 (the non-inverting input of error amplifier 1) is connected to the final output voltage (OUT) of the charger via a resistor divider network to sample the output voltage. The internal comparator adjusts the duty cycle of the two complementary (with dead time) PWM pulses output from pins 9 and 10 based on the comparison results of these two feedback signals with a reference. Resistors R13 and R14 are current-limiting resistors. In practical applications, parameters such as the voltage divider ratio of the feedback network, the resistance value of the current sampling resistor, and the oscillation frequency can be designed according to the specific output voltage and current specifications; this embodiment does not impose such limitations.

[0083] Based on the above, the 494 chip acquires the voltage and current signals at the output terminal and adjusts the PWM pulse width in real time to achieve constant voltage (CV) and constant current (CC) charging control, ensuring safety during the charging process and protecting the battery. Its two complementary PWM signals provide the initial control commands for driving the two switching transistors of the half-bridge.

[0084] The PWM signal output from the control chip has weak driving capability and cannot directly drive gallium nitride transistors, and requires preparation for isolated transmission. Therefore, based on the aforementioned 494 chip control module, as a further optional implementation method in this embodiment, such as... Figure 4 As shown, the totem pole driver module includes transistors Q3, Q4, Q7, and Q8, diodes D5, D1, D2, D8, D7, and D6.

[0085] The emitters of transistors Q3 and Q7 are connected together to form the first drive output terminal, which is connected to pin 3 of the primary side of the isolation drive transformer T2.

[0086] The emitters of transistors Q4 and Q8 are connected together to form the second drive output terminal, which is connected to pin 4 of the primary side of the isolation drive transformer T2.

[0087] The positive terminal of diode D5 is connected to the +12V power supply, and the negative terminal is connected to the collector of transistor Q3; diode D1 is connected between the base and collector of transistor Q3; diode D2 is connected between the emitter and collector of transistor Q7.

[0088] Diode D8 is connected between the base and collector of transistor Q4; diode D7 is connected between the emitter and collector of transistor Q8; the anode of diode D6 is connected to the collector of transistor Q8, and the cathode is grounded.

[0089] In the specific implementation, transistors Q3 and Q7 form a totem-pole push-pull circuit to drive one end (pin 3) of the primary winding of T2. Similarly, Q4 and Q8 form another totem-pole circuit to drive the other end (pin 4) of the primary winding of T2. Q3 and Q4 are NPN transistors (such as S8050), and Q7 and Q8 are PNP transistors (such as S8550). When pin 9 of the 494 chip outputs a high level, Q3 conducts, Q7 is cut off, and current flows from +12V through Q3 into pin 3 of T2. When pin 9 outputs a low level, Q3 is cut off, Q7 conducts, and current flows from pin 3 of T2 through Q7 to ground. This generates an alternating current in the pin 3-4 winding of T2, converting the voltage signal into a current signal that can be coupled through a transformer. Diode D5 provides power to the collector of Q3. D1 and D8 are accelerating diodes that help Q3 and Q4 turn off quickly. D2 and D7 are used to protect Q7 and Q8 from reverse peak voltage breakdown. D6 provides a return path to ground for the collector of Q8. In practical applications, the specific model of the transistor can be selected according to the drive current requirements; this embodiment does not limit this.

[0090] Based on the above, the totem-pole driver module functions as a power amplifier, converting the weak voltage-type PWM signal from the 494 chip into a current-driven signal capable of providing significant pull-up and sink currents. This push-pull output structure offers advantages such as low output impedance and fast switching speed, providing a sufficiently large excitation current to the primary winding of the isolation driver transformer. This ensures a steep signal edge, laying a solid foundation for subsequent high-frequency switching and solving the key problems of insufficient driving capability and slow signal edges when directly driving gallium nitride devices.

[0091] To achieve high-frequency, high-efficiency power conversion, as an optional implementation method in this embodiment, such as... Figure 5 As shown, the gallium nitride drive module includes gallium nitride transistors Q1 and Q2, resistors R15, R16, R24, and R28, ferrite beads FB1 and FB2, bipolar diodes ZD1 and ZD2, and capacitors C30 and C35.

[0092] The drain of gallium nitride transistor Q1 is connected to the positive DC output of the rectifier circuit module. Its gate is connected to pin 1 of the secondary side of the isolation drive transformer T2 through resistor R15 and ferrite bead FB1. Its source is connected to the drain of gallium nitride transistor Q2 and pin 2 of the primary side of transformer T1. Resistor R24 ​​is connected between the gate and source of gallium nitride transistor Q1. Capacitor C30 is connected in parallel between the drain and source of gallium nitride transistor Q1. Bipolar diode ZD1 is connected between the gate drive circuit and the source of gallium nitride transistor Q1.

[0093] The gate of the gallium nitride transistor Q2 is connected to pin 5 of the secondary side of the isolation drive transformer T2 via resistor R16 and ferrite bead FB2, and its source is grounded; resistor R28 is connected between the gate and source of gallium nitride transistor Q2; capacitor C35 is connected in parallel between the drain and source of gallium nitride transistor Q2; bipolar diode ZD2 is connected between the gate drive circuit and the source of gallium nitride transistor Q2.

[0094] In the specific implementation, Q1 and Q2 are enhancement-mode gallium nitride high electron mobility transistors (GaN HEMTs), such as the device with model number GS-065-011-1-L. The transistor's drain (D), gate (G), and source (S) are connected in a half-bridge configuration: Q1 is the upper transistor, and Q2 is the lower transistor. The secondary winding of the isolation drive transformer T2 has two independent windings, generating isolation signals to drive Q1 and Q2 respectively. The drain (D) of gallium nitride transistor Q1 is connected to the positive DC output of the rectifier circuit module. Its gate (G) is connected to pin 1 of the secondary winding of the isolation drive transformer T2 via resistor R15 and ferrite bead FB1. Its source (S) is connected to the drain (D) of gallium nitride transistor Q2 and pin 2 of the primary winding of transformer T1. Resistors R15 and R16 are gate drive resistors used to adjust the drive speed and suppress gate oscillation. Ferrite beads FB1 and FB2 are connected in series in the gate circuit to further absorb high-frequency noise. Resistors R24 and R28 are gate-source pull-down resistors, ensuring reliable turn-off of the GaN transistor when there is no drive signal. Capacitors C30 and C35 are the drain-source junction capacitance or external absorption capacitors, which help reduce voltage stress during switching. Bipolar diodes (also known as bidirectional TVS) ZD1 and ZD2 are connected in parallel between the gate and source to clamp the gate voltage and prevent gate overvoltage breakdown caused by interference or leakage inductance. They are key components for protecting the fragile gate of the GaN device. The gate (G pin) of the gallium nitride transistor Q2 is connected to pin 5 of the secondary side of the isolation drive transformer T2 through resistor R16 and ferrite bead FB2, while its source (S pin) is grounded. In practical applications, the model of the GaN transistor, the drive resistor, and the value of the ferrite bead can be adjusted according to the switching frequency and EMI requirements. This embodiment does not limit these aspects. The half-bridge topology shown in this embodiment, combined with the high current handling capability of gallium nitride transistors and the efficient rectification of silicon carbide diodes, enables the charger to stably output up to 1200W of power, realizing the potential of gallium nitride devices in high-power applications.

[0095] Based on the above, driven by a signal, Q1 and Q2 are alternately turned on at extremely high speeds (nanoseconds). When Q1 is on and Q2 is off, the DC bus voltage forms a loop to ground through Q1, the primary winding 2-1 (or 2-3) of transformer T1, and Q1. When Q2 is on and Q1 is off, the current in the primary winding of the transformer freewheels to ground through Q2. Thus, a high-frequency AC square wave is generated in the primary winding of transformer T1. The extremely low on-resistance and switching losses of gallium nitride devices result in minimal energy loss during this high-frequency switching process, allowing a higher proportion of input power to be transferred to the secondary winding, directly improving overall efficiency and making it possible to use a smaller transformer.

[0096] The high-frequency alternating current on the transformer secondary needs to be efficiently converted to direct current. Therefore, as an optional implementation method in this embodiment, such as... Figure 6As shown, the full-wave rectifier module includes silicon carbide diode D15 and silicon carbide diode D16;

[0097] The positive terminal of silicon carbide diode D15 is connected to pin 3 of the secondary winding of transformer T1, and the positive terminal of silicon carbide diode D16 is connected to pin 5 of the secondary winding of transformer T1. The negative terminals of silicon carbide diodes D15 and D16 are connected together as the positive output terminal of the full-wave rectifier module.

[0098] In practical implementation, the secondary winding of transformer T1 typically has a center tap (pin 4 grounded). Silicon carbide (SiC) SBDs D15 and D16 are Schottky barrier diodes, such as the C3D series. D15 is connected between one end (pin 3) of the secondary winding and the positive output terminal, and D16 is connected between the other end (pin 5) of the secondary winding and the positive output terminal. Thus, during the positive and negative half-cycles of the transformer secondary voltage, current flows to the output terminal through D15 and D16 respectively, achieving full-wave rectification. Silicon carbide diodes possess near-zero reverse recovery charge, low forward voltage drop, and extremely high operating frequency. In practical applications, other types of ultrafast recovery diodes can also be used, but silicon carbide diodes offer superior performance at high temperatures and high frequencies; this application does not limit this.

[0099] Based on the above, the full-wave rectifier module utilizes the high-speed, low-voltage-drop characteristics of silicon carbide diodes to rectify high-frequency AC power. Its near-zero reverse recovery time avoids the significant losses and noise generated during the reverse recovery period of traditional silicon fast recovery diodes, making it suitable for operation in high-frequency circuits. This further reduces losses and heat generation in the rectification stage and improves overall efficiency.

[0100] The rectified pulsating DC power needs to be smoothed and filtered, and the output controlled when necessary. Therefore, as an optional implementation method in this embodiment, such as... Figure 7 As shown, the filter circuit module includes inductor L2, electrolytic capacitor C17, electrolytic capacitor C21, capacitor C18, resistor R44, and relay FJH;

[0101] The input terminal of inductor L2 is connected to the positive output terminal of the full-wave rectifier module; electrolytic capacitors C17, C21, and C18, and resistor R44 are connected in parallel between the output terminal of inductor L2 and ground; the contacts of relay FJH are connected in series between the output terminal of inductor L2 and the final positive output terminal of the charger.

[0102] In the specific implementation, inductor L2 is the output filter inductor, forming an LC filter with the capacitor. Electrolytic capacitors C17 and C21 are low-voltage, high-capacity electrolytic capacitors (e.g., 63V) used to filter out low-frequency ripple and provide transient current to the load. Capacitor C18 is a film capacitor or ceramic capacitor with good high-frequency characteristics used to filter out high-frequency switching noise. Resistor R44 is a bleed resistor or voltage equalizing resistor. Relay FJH is an electromagnetic relay whose coil is controlled by a control circuit (not fully shown in the figure), and its normally open contact is connected in series in the filtered DC output path. When the charger is working normally, the relay is energized, and the output is turned on; when a fault is detected or standby is activated, the relay is de-energized, physically cutting off the output, ensuring high safety. In practical applications, the inductance value, capacitor capacity, and relay specifications can be designed according to the output voltage, current, and ripple requirements; this application embodiment does not limit these aspects.

[0103] Based on the above, the filter circuit module provides a stable and clean DC output. The LC filter effectively smooths the voltage ripple after high-frequency rectification, ensuring the quality of the output DC. The introduction of relays provides hard-switching output on / off control, which is safer and more reliable than relying solely on semiconductor switches, suitable for high-power applications, and enhances the product's safety and controllability.

[0104] To improve user experience and product reliability, it is necessary to intuitively display the status and manage temperature rise. As an optional implementation method in this embodiment, such as... Figure 8 As shown, the conversion circuit module includes operational amplifier U2A, operational amplifier U2B, indicator LED2, and fan M1;

[0105] The sampling input terminals of operational amplifiers U2A and U2B are connected to the output current sampling circuit. The output terminals of operational amplifiers U2A and U2B control the indicator LED2 to display different colors according to the signal level collected by the output current sampling circuit, and control the fan M1 to turn on and off.

[0106] In a specific implementation, operational amplifiers U2A and U2B can be dual op-amps integrated into a single chip, such as the LM358. Their non-inverting or inverting inputs are connected to the voltage signal across the output current sampling resistor (SENSOR1). Different current thresholds can be set by configuring the external resistors. The outputs of the op-amps are connected to the driving circuit of indicator LED2 (e.g., a dual-color LED) and the driving transistor (e.g., Q5) of fan M1 (a DC fan). For example, when the output current is less than a certain threshold (small current charging or standby), the control indicator LED2 displays green, and the fan M1 remains off. When the output current is greater than the threshold, the control indicator LED2 turns red (or orange), and the fan M1 starts rotating to enhance heat dissipation. The specific control logic can be implemented using op-amps U2A and U2B and their peripheral circuits (e.g., including transistor Q5). This application does not limit the specific circuit form for implementing this logic.

[0107] Based on the above, the conversion circuit module implements visual feedback of the output status and active thermal management. Indicator lights allow users to clearly understand the charger's operating mode (standby, low current, high power). The fan is automatically controlled according to the power (current) level, achieving a balance between quiet operation and heat dissipation: quiet operation at low power and efficient heat dissipation at high power, which not only improves the user experience but also ensures the lifespan of components and the reliability of the entire device through intelligent temperature control.

[0108] In summary, the core working mechanism of the gallium nitride charger based on the 494PWM chip in this application embodiment is as follows: the 494 chip control module drives the gallium nitride transistors Q1 and Q2 in the half-bridge topology to conduct alternately at high frequency through the totem pole drive module and the isolation drive transformer T2.

[0109] Specifically, the 494 chip generates two precise, complementary PWM signals. The totem-pole driver module amplifies these signals into drive signals with strong pull-in and pull-out current capabilities. The isolation drive transformer T2 not only achieves safe isolation between the high and low voltage sides but also converts the primary single-ended signal into two floating drive signals on the secondary side, which are used to drive the upper and lower transistors of the half-bridge, respectively. Finally, these two signals control Q1 and Q2 to switch alternately at extremely high speeds (e.g., hundreds of kHz), inverting high-voltage DC into high-frequency AC, which is then stepped down, rectified, and filtered before being output.

[0110] This complete signal and power chain works in tandem to construct a complete pathway from precise control to powerful drive to efficient execution, enabling the full and safe release of the high-frequency potential of gallium nitride devices. The result is that the charger can operate stably at higher switching frequencies, thereby reducing the size of transformers and inductors (increasing power density) while simultaneously reducing switching losses due to the extremely shortened switching process (improving efficiency), successfully achieving a balance between high power, high efficiency, and high power density.

[0111] In the embodiments provided in this application, it should be understood that the embodiments described herein can be implemented in hardware, software, firmware, middleware, code, or any suitable combination thereof. For hardware implementation, the processor may be implemented in one or more of the following: application-specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field-programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, other electronic units designed to implement the functions described herein, or combinations thereof. For software implementation, some or all of the processes of the embodiments may be performed by a computer program instructing the associated hardware. During implementation, the program may be stored in a computer-readable storage medium or transmitted as one or more instructions or code on a computer-readable storage medium. Computer-readable storage media include computer storage media and communication media, wherein communication media include any medium that facilitates the transmission of a computer program from one place to another. Storage media may be any available medium accessible to a computer. Computer-readable storage media may include, but are not limited to, RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage media or other magnetic storage devices, or any other medium capable of carrying or storing desired program code having the form of instructions or data structures and accessible to a computer.

[0112] Finally, it should be noted that the above description is only a preferred embodiment of this application and is not intended to limit this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A gallium nitride charger based on a 494PWM chip, characterized in that, include: Power board; The rectifier circuit module has its input terminal connected to the AC input terminal of the power board, and is used to rectify the AC input into DC power. The input terminal of the gallium nitride driver module with half-bridge topology is connected to the DC output terminal of the rectifier circuit module; Transformer T1, the primary end of which is connected to the output end of the gallium nitride drive module; The 494 chip control module is used to generate PWM control signals and sample and adjust the output voltage and output current of the charger. The totem pole driving module has its input terminal connected to the PWM signal output terminal of the 494 chip control module; The isolation drive transformer T2 has its primary end connected to the output end of the totem pole drive module and its secondary end connected to the control end of the gallium nitride drive module, and is used to isolate and drive the PWM control signal. The full-wave rectifier module has its input terminal connected to the secondary terminal of the transformer T1, and is used to perform full-wave rectification on the transformed AC power. The filter circuit module has its input terminal connected to the output terminal of the full-wave rectifier module, and its output terminal is controlled by a relay FJH, which is used to filter and control the output of the rectified voltage. A conversion circuit module, connected to the output terminal of the filter circuit module, is used to control the indicator light and fan based on the output current sampling. The 494 chip control module drives the gallium nitride transistors Q1 and Q2 in the half-bridge topology to conduct at high frequency through the totem pole drive module and the isolation drive transformer T2; The gallium nitride driving module includes gallium nitride transistors Q1 and Q2, resistors R15, R16, R24, and R28, ferrite beads FB1 and FB2, bipolar diodes ZD1 and ZD2, and capacitors C30 and C35. The drain of the gallium nitride transistor Q1 is connected to the positive DC output of the rectifier circuit module. Its gate is connected to pin 1 of the secondary side of the isolation drive transformer T2 via resistor R15 and ferrite bead FB1. Its source is connected to the drain of the gallium nitride transistor Q2 and pin 2 of the primary side of the transformer T1. Resistor R24 ​​is connected between the gate and source of the gallium nitride transistor Q1. Capacitor C30 is connected in parallel between the drain and source of the gallium nitride transistor Q1. Bipolar diode ZD1 is connected between the gate drive circuit and the source of the gallium nitride transistor Q1. The gate of the gallium nitride transistor Q2 is connected to pin 5 of the secondary side of the isolation drive transformer T2 via the resistor R16 and the ferrite bead FB2, and its source is grounded; the resistor R28 is connected between the gate and the source of the gallium nitride transistor Q2; the capacitor C35 is connected in parallel between the drain and the source of the gallium nitride transistor Q2; and the bipolar diode ZD2 is connected between the gate drive circuit and the source of the gallium nitride transistor Q2.

2. The gallium nitride charger based on a 494PWM chip according to claim 1, characterized in that, The rectifier circuit module includes fuse F1, fuse F2, thermistor RTH3, thermistor RTH4, thermistor RTH5, ​​common mode inductor L1, X capacitor C1, X capacitor C2, Y capacitor C5, Y capacitor C6, Y capacitor C13 and Y capacitor C19. The AC input passes sequentially through fuses F1 and F2 connected in parallel, and the thermistors RTH3, RTH4, and RTH5 connected in parallel, before being connected to the input terminal of the common-mode inductor L1. X capacitor C1 and resistor R0 are connected in parallel between pins 2 and 4 of the common-mode inductor L1, and X capacitor C2 is connected in parallel between pins 1 and 3 of the common-mode inductor L1. Y capacitors C5 and C6 are connected between the input live wire and ground, and Y capacitors C13 and C19 are connected between the input neutral wire and ground.

3. The gallium nitride charger based on a 494PWM chip according to claim 2, characterized in that, The rectifier circuit module also includes a common-mode inductor L0, a rectifier bridge BG1, an electrolytic capacitor C8, an electrolytic capacitor C8_2, and a DC blocking capacitor C9. The output terminal of the common mode inductor L1 is connected to the input terminal of the common mode inductor L0; the AC input terminal of the rectifier bridge BG1 is connected to the output terminal of the common mode inductor L0; the DC output positive terminal of the rectifier bridge BG1 is filtered by the electrolytic capacitor C8 and electrolytic capacitor C8_2, and then passes through the DC blocking capacitor C9, and serves as the DC output positive terminal of the rectifier circuit module.

4. The gallium nitride charger based on a 494PWM chip according to claim 1, characterized in that, The 494 chip control module includes a 494 chip U1; Pin 9 of the 494 chip U1 is connected to the base of transistors Q3 and Q7 in the totem pole driver module via resistor R13, for outputting the first PWM signal; Pin 10 of the 494 chip U1 is connected to the base of transistors Q4 and Q8 in the totem pole driver module via resistor R14, for outputting a second PWM signal; Pin 1 of the 494 chip U1 is connected to the output voltage sampling circuit for adjusting the output voltage; Pin 15 of the 494 chip U1 is connected to the output current sampling circuit for adjusting the output current.

5. The gallium nitride charger based on a 494PWM chip according to claim 4, characterized in that, The totem pole driving module includes transistor Q3, transistor Q4, transistor Q7, transistor Q8, diode D5, diode D1, diode D2, diode D8, diode D7, and diode D6; The emitters of transistors Q3 and Q7 are connected together to form the first drive output terminal, which is connected to pin 3 of the primary side of the isolation drive transformer T2. The emitters of transistors Q4 and Q8 are connected together to form the second drive output terminal, which is connected to pin 4 of the primary side of the isolation drive transformer T2. The positive terminal of diode D5 is connected to a +12V power supply, and the negative terminal is connected to the collector of transistor Q3; diode D1 is connected between the base and collector of transistor Q3; diode D2 is connected between the emitter and collector of transistor Q7. The diode D8 is connected between the base and collector of the transistor Q4; the diode D7 is connected between the emitter and collector of the transistor Q8; the anode of the diode D6 is connected to the collector of the transistor Q8, and the cathode is grounded.

6. The gallium nitride charger based on a 494PWM chip according to claim 1, characterized in that, The full-wave rectifier module includes silicon carbide diode D15 and silicon carbide diode D16; The positive terminal of the silicon carbide diode D15 is connected to pin 3 of the secondary winding of the transformer T1, and the positive terminal of the silicon carbide diode D16 is connected to pin 5 of the secondary winding of the transformer T1. The negative terminals of the silicon carbide diodes D15 and D16 are connected together, serving as the positive output terminal of the full-wave rectifier module.

7. The gallium nitride charger based on a 494PWM chip according to claim 1, characterized in that, The filter circuit module includes an inductor L2, an electrolytic capacitor C17, an electrolytic capacitor C21, a capacitor C18, a resistor R44, and the relay FJH; The input terminal of the inductor L2 is connected to the positive output terminal of the full-wave rectifier module; the electrolytic capacitor C17, the electrolytic capacitor C21, the capacitor C18 and the resistor R44 are connected in parallel between the output terminal of the inductor L2 and ground; the contacts of the relay FJH are connected in series between the output terminal of the inductor L2 and the final positive output terminal of the charger.

8. The gallium nitride charger based on a 494PWM chip according to claim 1, characterized in that, The conversion circuit module includes operational amplifier U2A, operational amplifier U2B, indicator LED2, and fan M1; The sampling input terminals of the operational amplifiers U2A and U2B are connected to the output current sampling circuit. The output terminals of the operational amplifiers U2A and U2B control the indicator LED2 to display different colors and control the fan M1 to turn on and off according to the signal level collected by the output current sampling circuit.

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