A high voltage input LLC control circuit
By employing capacitor series voltage divider sampling in the high-voltage input LLC control circuit, the problems of high power loss and low sampling accuracy of the sampling unit are solved, achieving lower power consumption and higher sampling accuracy, and improving the system's adaptive dead-time control and light-load efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- MORNSUN GUANGZHOU SCI & TECH
- Filing Date
- 2025-08-07
- Publication Date
- 2026-07-28
AI Technical Summary
In existing high-voltage input LLC control circuits, the resistor-divided voltage method of the sampling unit results in high power loss, large space occupation, and low sampling accuracy, which affects the system's dead-time adaptive control.
A capacitor series voltage divider sampling method is adopted. By adding a sampling unit at the midpoint of the series connection between the upper and lower switching devices, the rising and falling edges of the upper and lower switching devices are detected by the voltage divider signal to control the on and off of the devices.
It reduces the power loss of the sampling unit, reduces the space occupied, improves the sampling accuracy, enhances the adaptive dead-zone control effect of the system, and improves the efficiency and reliability of the system under light load.
Smart Images
Figure CN224571087U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of electronic circuit technology, and in particular to a high-voltage input LLC control circuit. Background Technology
[0002] With the rapid development of power electronics technology, switching converters have been widely used. People are placing higher demands on switching converters: high power density, high reliability, and small size. LLC resonant converters, as a type of resonant converter, have many advantages such as low noise, low stress, and low switching losses. Since LLC converters have two switching devices, they are usually driven by a bootstrap mechanism. LLC control chips generally integrate drive circuits, which can be directly connected to the upper and lower switching devices. However, the withstand voltage of the upper and lower drive circuits in commercially available LLC control chips generally does not exceed 650V, which limits the applicable input voltage range of the LLC. The rectified input voltage of three-phase power systems and high-voltage input systems can reach over 800V. Therefore, LLC topology control chips used for high-voltage input cannot be directly connected to the upper and lower switching devices for driving.
[0003] Chinese patent application CN202211726553.6 proposes an adaptive dead-time control technology for a high-voltage input LLC control circuit based on a sampling unit that uses a resistor series voltage divider. By adding a sampling unit at the midpoint of the series connection of the upper and lower switching devices, and dividing the voltage at the midpoint of the series connection of the upper and lower switching devices, the voltage signal after this two-stage floating ground voltage divider is provided to the control unit as a sampling signal for detecting the rising and falling edges of the midpoint of the series connection of the upper and lower switching devices.
[0004] This sampling unit uses a series resistor voltage divider. Under high-voltage input, the resistor voltage divider continuously consumes energy, leading to reduced circuit efficiency. Furthermore, it requires multiple high-value resistors in series, resulting in a large space footprint for the sampling unit. The sampling unit is connected at the midpoint of the series connection between the upper and lower switching devices. The input to the sampling unit is a high-voltage, high-frequency switching square wave signal. Influenced by the parasitic parameters of other components in the circuit, the resistor voltage divider sampling method suffers from insufficient voltage equalization, affecting sampling accuracy and consequently impacting the adaptive dead-time control of the entire system. Utility Model Content
[0005] The present invention aims to overcome at least one of the defects in the prior art and provide a high-voltage input LLC control circuit that can reduce the power loss of the sampling unit, improve the efficiency of the circuit, reduce the space occupied by the sampling unit, improve the voltage equalization sampling effect, and avoid the system adaptive dead time control defect caused by uneven voltage division.
[0006] To solve the above-mentioned technical problems, the objective of this utility model is achieved through the following technical solution:
[0007] This utility model provides a high-voltage input LLC control circuit, which includes a control unit, an isolation unit, an upper switching device, a lower switching device, a sampling unit, and a resonant unit. The first output terminal of the control unit is connected to the first input terminal of the isolation unit. The second output terminal of the control unit and the output terminal of the sampling unit are both connected to the second input terminal of the isolation unit. The first output terminal of the isolation unit is connected to the control terminal of the upper switching device. The output terminal of the upper switching device is connected to the second output terminal of the isolation unit, the input terminal of the lower switching device, the first input terminal of the sampling unit, and the first input terminal of the resonant unit, respectively. The third output terminal of the control unit is connected to the control terminal of the lower switching device. The fourth output terminal of the control unit is connected to the output terminal of the lower switching device, the second input terminal of the sampling unit, and the second input terminal of the resonant unit, respectively.
[0008] The sampling unit includes capacitor C8 and capacitor C9. The first end of capacitor C8 serves as the first input terminal of the sampling unit. The second end of capacitor C8 is connected to the first end of capacitor C9 and serves as the output terminal of the sampling unit. The second end of capacitor C9 serves as the second input terminal of the sampling unit. The sampling unit is used to divide and reduce the voltage and output it to the control unit, so that the control unit controls the upper switching device to turn on when the rising edge disappears and controls the lower switching device to turn on when the falling edge disappears.
[0009] Optionally, the sampling unit further includes diodes D3 and D4. Diode D3 is connected in parallel across capacitor C8. The cathode of diode D3 is led out as the first input terminal of the sampling unit, and the anode of diode D3 is led out as the output terminal of the sampling unit. Diode D4 is connected in parallel across capacitor C9. The cathode of diode D4 is led out as the output terminal of the sampling unit, and the anode of diode D4 is connected to ground.
[0010] Optionally, the control unit is used to receive the sampling signal output by the sampling unit and output the drive signals of the upper switching device and the lower switching device;
[0011] The isolation unit is used to receive the drive signal from the control unit, and output it to the upper switching device after modulation and isolation.
[0012] Optionally, the isolation unit includes a power supply terminal VCC, diodes D5 and D6, capacitors C1 and C2, and an isolation chip U1. When the lower switching device is turned on, the power supply terminal VCC charges capacitor C1 through diode D6 and capacitor C1 in a first path, and simultaneously charges capacitor C2 through diode D5 and capacitor C2 in a second path. When the upper switching device is turned on, capacitors C1 and C2 supply power to the isolation chip U1.
[0013] Optionally, the isolation unit includes a power supply terminal VCC, diodes D5 and D6, capacitors C1 and C2, and an isolation chip U1. When the lower switching device is turned on, the power supply terminal VCC charges capacitor C1 through diode D6 and capacitor C1 via the input terminal HS of the sampling unit to ground. At the same time, the power supply terminal VCC charges capacitor C2 through diode D5 and capacitor C2 via the output terminal HB of the sampling unit to ground. When the upper switching device is turned on, capacitors C1 and C2 supply power to the isolation chip U1.
[0014] Optionally, the isolation unit includes a power supply terminal VCC, diodes D5 and D6, capacitors C1 and C2, and an isolation chip U1. The power supply terminal VCC is connected to the anodes of diodes D5 and D6, respectively. The cathode of diode D5 is connected to one end of capacitor C2 and the VCC1 terminal of the isolation chip, and the other end of capacitor C2 is connected to the output terminal HB of the sampling unit and the GND1 terminal of the isolation chip, respectively. The cathode of diode D6 is connected to one end of capacitor C1 and the VCC2 terminal of the isolation chip, and the other end of capacitor C1 is connected to the input terminal HS of the sampling unit and the GND2 terminal of the isolation chip, respectively.
[0015] Optionally, the high-voltage input LLC control circuit can withstand an input voltage of 800V or higher.
[0016] Compared with the prior art, the present invention has the following beneficial effects:
[0017] 1. This utility model avoids the problem of overheating and aging caused by long-term operation of resistors by adopting capacitor series voltage division sampling, thereby enabling the adaptive dead-time control technology of the high-voltage input LLC control circuit to achieve lower power consumption, reduce standby power consumption, and improve the working efficiency of the high-voltage LLC topology.
[0018] 2. This invention adds a sampling unit at the midpoint of the series connection between the upper and lower switching devices. The output of the sampling unit is connected to the second output of the control unit. This divides the voltage at the midpoint of the series connection between the upper and lower switching devices, and the resulting signal is sent to the control unit to detect the rising and falling edges of the midpoint of the series connection. When the rising edge disappears, the upper switching device is turned on. When the falling edge disappears, the lower switching device is turned on. This achieves adaptive dead time for the upper and lower switching devices, improving efficiency under light loads and system reliability. Attached Figure Description
[0019] Figure 1 This is a schematic block diagram of a high-voltage input LLC control circuit according to the present invention.
[0020] Figure 2 This is a circuit diagram of a high-voltage input LLC control circuit according to the present invention. Detailed Implementation
[0021] To make this utility model clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of the utility model.
[0022] Please see Figure 1 , Figure 1 The schematic diagram of a high-voltage input LLC control circuit and its working method provided in this embodiment of the present invention can solve the problems of insufficient withstand voltage of the upper and lower drive units of the LLC control chip and the inability to detect the rising and falling edges of the midpoint of the series connection of the upper and lower switching devices when high voltage is input.
[0023] refer to Figure 1 This utility model embodiment provides a high-voltage input LLC control circuit, including a control unit 01, an isolation unit 02, an upper switching device 03, a lower switching device 04, a sampling unit 05, and a resonant unit 06.
[0024] The first output terminal of control unit 01 is the drive signal output terminal for the upper switching device. This terminal is connected to the first input terminal of isolation unit 02. After the drive signal is modulated by isolation unit 02, a control signal is generated. The control signal is output from the first and second output terminals of isolation unit 02 to control the on and off of the upper switching device 03. The second output terminal of control unit 01 is the potential reference point of the first output terminal. This port is equipped with rising edge and falling edge detection functions. The second output terminal of control unit 01 is connected to the second input terminal of isolation unit 02, so that the potential of the first output terminal of control unit 01 is equal to that of the reference point of the first input terminal of isolation unit 02. After the second output terminal of control unit 01 is connected to the second input terminal of isolation unit 02, it is then connected to the output terminal of sampling unit 05, so that the second output terminal of control unit 01 can detect the rising edge and falling edge signals of the midpoint of the series connection of the upper and lower switching devices obtained by voltage division by sampling unit 05.
[0025] The third output terminal of control unit 01 is the drive signal output terminal for the lower switching device. This port can be directly connected to the lower switching device, or connected to the lower switching device through other drive circuits, for controlling the opening and closing of the lower switching device. The fourth output terminal of control unit 01 is the control unit potential reference point.
[0026] The second output terminal of isolation unit 02 serves as the potential reference point for the first output terminal of isolation unit 02, and this terminal is connected to the output terminal of the upper switching device 03. The control signal generated by isolation unit 02 is transmitted to the control terminal and output terminal of the upper switching device 03 through the first output terminal and the second output terminal to control the opening and closing of the upper switching device.
[0027] The output terminal of the upper switching device 03 is connected to the input terminal of the lower switching device 04. The control signal generated by the control unit 01 causes an AC square wave to be generated at the midpoint between the output terminal of the upper switching device 03 and the input terminal of the lower switching device 04. The AC square wave provides energy and flows into the resonant unit 06 through the first and second input terminals for power conversion.
[0028] The first input terminal of sampling unit 05 is connected to the midpoint between the output terminal of upper switching device 03 and the input terminal of lower switching device 04, and the second input terminal of sampling unit 05 is connected to the output terminal of lower switching device 04. Sampling unit 05 samples and divides the voltage at the rising and falling edges of the midpoint between the output terminals of upper switching device 03 and lower switching device 04, and then transmits the signal to the second output terminal of control unit 01 for detection through the output terminal of sampling unit 05.
[0029] This invention improves the voltage withstand capability of the control unit by adding an isolation unit between the control unit and the upper switching device. A sampling unit is added at the midpoint of the series connection between the upper and lower switching devices to divide the voltage at this midpoint. The divided signal is then sent to the control unit to detect the rising and falling edges of the midpoint of the series connection. When the rising edge disappears, it indicates that the parasitic capacitance of the upper switching device has completely discharged, and turning on the upper switching device at this time achieves zero-voltage turn-on. Similarly, when the falling edge disappears, turning on the lower switching device achieves zero-voltage turn-on. Therefore, sampling the rising and falling edges of the midpoint of the series connection between the upper and lower switching devices can determine their turn-on times, achieving adaptive dead time and improving light-load efficiency and system reliability. The problems of insufficient withstand voltage of the upper and lower drive units of the LLC control chip and inability to detect the rising and falling edges of the midpoint of the series connection of the upper and lower switching devices were also solved when the control chip was operating under high voltage input conditions exceeding the rated withstand voltage value.
[0030] Please see Figure 2 , Figure 2 The circuit diagram shows a high-voltage input LLC control circuit and its working method provided in this embodiment of the utility model.
[0031] In a specific embodiment, please refer to Figure 2 The control unit includes a control chip U2B. In this embodiment, the control chip U2B is a TEA2016, but is not limited to TEA2016. Pin 10 of this chip is the second output terminal of the control unit 01, pin 9 is the first output terminal of the control unit 01, pin 6 is the third output terminal of the control unit 01, and pin 4 is the fourth output terminal of the control unit.
[0032] In a specific embodiment, please refer to Figure 2The isolation unit 02 includes an isolation chip U1, a power supply terminal VCC, diodes D5 and D6, capacitors C1 and C2. The power supply terminal VCC is connected to the anodes of diodes D5 and D6. The cathode of diode D5 is connected to one end of capacitor C2 and the VCC1 terminal of the isolation chip. The other end of capacitor C2 is connected to the output terminal HB of the sampling unit and the GND1 terminal of the isolation chip. The cathode of diode D6 is connected to one end of capacitor C1 and the VCC2 terminal of the isolation chip. The other end of capacitor C1 is connected to the input terminal HS of the sampling unit and the GND2 terminal of the isolation chip. In this embodiment, the isolation chip U1 is an IC that implements isolation driving, preferably an Nsi6601, but not limited to Nsi6601. Pin 2 of this chip is the first input terminal of isolation unit 02, pin 4 is the second input terminal of isolation unit 02, pin 6 is the first output terminal of isolation unit 03, and pin 8 is the second output terminal of isolation unit 03.
[0033] In a specific embodiment, please refer to Figure 2 The sampling unit 05 includes diodes D3 and D4, capacitors C8 and C9. Capacitors C8 and C9 are connected in series to form a series branch, diode D3 and capacitor C8 are connected in parallel to form a parallel network, and diode D4 and capacitor C9 are connected in parallel to form a parallel network. The cathode of diode D3 is led out as the first input terminal HS of sampling unit 05. One end of capacitor C9 in the series branch is grounded to PGDN, serving as the second input terminal of sampling unit 05. The midpoint of the series connection between capacitors C8 and C9 is led out as the output terminal HB of sampling unit 05. In this embodiment, capacitor C8 can be the parasitic capacitance of diode D3; by pairing it with a pull-down capacitor C9 of appropriate value, the desired effect can also be achieved. In this embodiment, capacitor C9 can be the equivalent capacitance of pin 11 of control chip U2B to ground GND; by pairing it with a pull-up capacitor C8 of appropriate value, the desired effect can also be achieved. In this embodiment, diode D4 serves to prevent negative voltage from HB to ground GND, thus protecting pin 11 of control chip U2B; in practical applications, it may not be connected.
[0034] In a specific embodiment, please refer to Figure 2 The upper switching device 03 includes MOSFET Q1, and the lower switching device 04 includes MOSFET Q2.
[0035] In a specific embodiment, please refer to Figure 2The control signals generated by the control chip U2B for the upper and lower switching devices are complementary and symmetrical square wave signals. When pin 6 of the control chip U2B outputs a high-level drive signal, the drive signal is transmitted to the gate of MOSFET Q2 through resistor R6, turning on the drain and source of MOSFET Q2. At this time, the first input terminal HS of sampling unit 05 is shorted to ground GND through MOSFET Q2. The power supply terminal VCC forms a path to ground through diode D5, capacitor C2, and the output terminal HB of the sampling unit connected to diode D3, charging capacitor C2. Simultaneously, the power supply terminal VCC forms a path to ground through diode D6, capacitor C1, and the input terminal HS of the sampling unit, charging capacitor C1. Capacitors C1 and C2 are used to power the isolation driver IC U1 when the upper switching device is turned on.
[0036] In a specific embodiment, please refer to Figure 2 When the control chip U2B outputs a high-level drive signal from pin 9 to pin 11, the drive signal is sent to the isolation chip U1. The isolation chip U1 modulates and isolates the drive signal, then outputs it through pin 6, which, via resistor R1, transmits it to the gate of MOSFET Q1, turning on the drain and source of MOSFET Q1. After MOSFET Q1 is turned on, the HS network at the input of the sampling unit is shorted to VBUS through the MOSFET. The HB network at the output of the sampling unit is divided by capacitors C8 and C9, with the specific voltage division value being... The rising and falling changes of the input HS at the sampling unit are divided by capacitors C8 and C9. The resulting signal is the voltage signal after two-stage floating ground voltage division. This divided signal is transmitted to pin 11 of the control chip U2B. By detecting the divided signal, the rising and falling edges of the midpoint of the series connection between the upper and lower switching devices reflected in the HS network can be detected. Furthermore, when the input voltage is high, especially under conditions exceeding the rated withstand voltage of the control chip U2B, adjusting the values of capacitors C8 and C9 can ensure that the withstand voltage of pin 11 of the control chip U2B to ground remains within safe specifications.
[0037] The above are merely preferred embodiments of this utility model. It should be noted that the above preferred embodiments should not be considered as limitations on this utility model, and the scope of protection of this utility model should be determined by the scope defined in the claims. For those skilled in the art, several improvements and modifications can be made without departing from the spirit and scope of this utility model, and these improvements and modifications should also be considered within the scope of protection of this utility model.
[0038] Furthermore, all the terms "electrical connection" and "connection" mentioned in this patent application do not refer to direct connection of components, but rather to the ability to form a better connection structure by adding or removing connecting accessories according to the specific implementation. The use of "electrical connection" in this utility model is only to emphasize this meaning, but it does not exclude the use of "connection" and other terms that also have this meaning.
Claims
1. A high-voltage input LLC control circuit, characterized in that: The high-voltage input LLC control circuit includes a control unit, an isolation unit, an upper switching device, a lower switching device, a sampling unit, and a resonant unit. The first output terminal of the control unit is connected to the first input terminal of the isolation unit. The second output terminal of the control unit and the output terminal of the sampling unit are both connected to the second input terminal of the isolation unit. The first output terminal of the isolation unit is connected to the control terminal of the upper switching device. The output terminal of the upper switching device is connected to the second output terminal of the isolation unit, the input terminal of the lower switching device, the first input terminal of the sampling unit, and the first input terminal of the resonant unit, respectively. The third output terminal of the control unit is connected to the control terminal of the lower switching device. The fourth output terminal of the control unit is connected to the output terminal of the lower switching device, the second input terminal of the sampling unit, and the second input terminal of the resonant unit, respectively. The sampling unit includes capacitor C8 and capacitor C9. The first end of capacitor C8 serves as the first input terminal of the sampling unit. The second end of capacitor C8 is connected to the first end of capacitor C9 and serves as the output terminal of the sampling unit. The second end of capacitor C9 serves as the second input terminal of the sampling unit. The sampling unit is used to divide and reduce the voltage and output it to the control unit, so that the control unit controls the upper switching device to turn on when the rising edge disappears and controls the lower switching device to turn on when the falling edge disappears.
2. The high-voltage input LLC control circuit according to claim 1, characterized in that: The sampling unit further includes diodes D3 and D4. Diode D3 is connected in parallel across capacitor C8. The cathode of diode D3 is led out as the first input terminal of the sampling unit, and the anode of diode D3 is led out as the output terminal of the sampling unit. Diode D4 is connected in parallel across capacitor C9. The cathode of diode D4 is led out as the output terminal of the sampling unit, and the anode of diode D4 is connected to ground.
3. The high-voltage input LLC control circuit according to claim 1, characterized in that: The control unit is used to receive the sampling signal output by the sampling unit and output the drive signals of the upper switching device and the lower switching device; The isolation unit is used to receive the drive signal from the control unit, and output it to the upper switching device after modulation and isolation.
4. The high-voltage input LLC control circuit according to claim 1, characterized in that: The isolation unit includes a power supply terminal VCC, diode D5, diode D6, capacitor C1, capacitor C2, and isolation chip U1. When the lower switching device is turned on, the power supply terminal VCC forms a first path through diode D6 and capacitor C1 to charge capacitor C1, and at the same time, the power supply terminal VCC forms a second path through diode D5 and capacitor C2 to charge capacitor C2. When the upper switching device is turned on, capacitors C1 and C2 supply power to the isolation chip U1.
5. The high-voltage input LLC control circuit according to claim 1, characterized in that, The isolation unit includes a power supply terminal VCC, diode D5, diode D6, capacitor C1, capacitor C2, and isolation chip U1. When the lower switching device is turned on, the power supply terminal VCC charges capacitor C1 through diode D6 and capacitor C1 via the input terminal HS of the sampling unit to ground. At the same time, the power supply terminal VCC charges capacitor C2 through diode D5 and capacitor C2 via the output terminal HB of the sampling unit to ground. When the upper switching device is turned on, capacitors C1 and C2 supply power to the isolation chip U1.
6. The high-voltage input LLC control circuit according to claim 1, characterized in that, The isolation unit includes a power supply terminal VCC, diodes D5 and D6, capacitors C1 and C2, and an isolation chip U1. The power supply terminal VCC is connected to the anodes of diodes D5 and D6, respectively. The cathode of diode D5 is connected to one end of capacitor C2 and the VCC1 terminal of the isolation chip, and the other end of capacitor C2 is connected to the output terminal HB of the sampling unit and the GND1 terminal of the isolation chip, respectively. The cathode of diode D6 is connected to one end of capacitor C1 and the VCC2 terminal of the isolation chip, and the other end of capacitor C1 is connected to the input terminal HS of the sampling unit and the GND2 terminal of the isolation chip, respectively.
7. The high-voltage input LLC control circuit according to claim 1, characterized in that, The high-voltage input LLC control circuit can withstand input voltages of 800V or higher.