A high-voltage isolation bridge leg driving circuit based on a single magnetic core

Abstract

The application relates to a single-magnetic-core-based high-voltage isolation bridge arm driving circuit, which comprises a PWM signal conditioning circuit, a first path buffer and reverse circuit, a second path buffer and reverse circuit, a transistor driving circuit, a transformer and a secondary side clamping circuit; the PWM signal conditioning circuit has at least one input pin and two output pins, which are used for inputting 50% duty ratio PWM driving signals and dead time signals. The application has the beneficial effects that the single-magnetic-core-based high-voltage isolation bridge arm driving circuit can realize the dead-time-complemented PWM driving of two half-bridge switching tubes or four full-bridge switching tubes, reduces the number of driving transformers used, and simplifies the design of the bridge driving circuit. By adopting one driving transformer, the dead-time-complemented isolation driving of all power switches of the bridge conversion topology is realized, the design of the isolation driving circuit is simplified, and the application is suitable for frequency modulation and duty ratio control.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, specifically to a high-voltage isolated bridge arm drive circuit based on a single magnetic core. Background Technology

[0002] High-voltage power supplies achieve high-voltage power conversion and are commonly used in applications such as high-voltage DC power supply, specialized industrial and medical applications, and high-energy pulse pollution control. High-voltage power supplies generally employ a full-bridge inverter topology composed of power switching transistors and a transformer-isolated conversion topology, particularly a resonant DC-DC converter topology. The power switch drive circuit must withstand the same operating potential difference as the power supply input / output terminals. When the potential difference is too high, a transformer-isolated drive method is more suitable.

[0003] Existing drive transformer solutions are often single-transistor driven, which cannot simultaneously generate complementary PWM drive signals with dead time for the upper and lower transistors of the bridge arm. If there are four power switches in a full bridge, four drive transformers are required, which increases the manufacturing cost of the drive circuit and the PCB mounting space. Summary of the Invention

[0004] This invention addresses the technical problems existing in the prior art by providing a high-voltage isolated bridge arm drive circuit based on a single magnetic core to solve the problem of the cumbersome driving method of the aforementioned bridge drive circuit.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: a high-voltage isolated bridge arm drive circuit based on a single magnetic core, including a PWM signal conditioning circuit, a first buffer and inverting circuit, a second buffer and inverting circuit, a transistor drive circuit, a transformer, and a secondary clamping circuit;

[0006] The PWM signal conditioning circuit has at least one input pin and two output pins for inputting a 50% duty cycle PWM drive signal and a dead time signal; one output pin of the PWM signal conditioning circuit is connected to the input pin of the first buffer and inverting circuit, and the other output pin is connected to the input pin of the second buffer and inverting circuit through a delay unit, for converting one PWM signal into two complementary PWM signals with dead time to drive the transistor drive circuit.

[0007] Based on the above technical solution, the present invention can be further improved as follows.

[0008] Furthermore, the transistor driving circuit includes an upper transistor and a lower transistor located in the first bridge arm, and an upper transistor and a lower transistor located in the second bridge arm.

[0009] Furthermore, both the first and second buffer and inverting circuits are composed of buffers and inverters.

[0010] Furthermore, the input pins of the co-channel buffer and inverter are connected to the output pins of the co-channel PWM signal conditioning circuit; the outputs of the two buffers are respectively connected to the control terminals of the upper and lower transistors of one bridge arm; the outputs of the two inverters are respectively connected to the control terminals of the upper and lower transistors of the other bridge arm.

[0011] Furthermore, the PWM drive signal is phase-shifted by a delayer to generate a dead time, and the phase-shifting angle corresponds to the size of the dead time.

[0012] Furthermore, the secondary clamping circuit consists of a diode, a bleeder resistor, a Zener diode, and a drive resistor.

[0013] The beneficial effects of this invention are as follows: The high-voltage isolated bridge arm drive circuit based on a single magnetic core involved in this invention can realize complementary PWM drive with dead time for two switching transistors in a half-bridge or four switching transistors in a full-bridge, reducing the number of drive transformers used and simplifying the design of the bridge drive circuit. By using a single drive transformer, complementary isolated drive with dead time is achieved for all power switches in the bridge converter topology, simplifying the design of the isolation drive circuit and making it suitable for frequency modulation and proportional modulation control. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the existing half-bridge topology driving circuit of the present invention;

[0015] Figure 2 This is a schematic diagram of the existing full-bridge topology drive circuit of the present invention;

[0016] Figure 3 This is a circuit diagram of the half-bridge transformer isolation drive circuit of the present invention;

[0017] Figure 4 This is a circuit diagram of the full-bridge transformer isolation drive circuit of the present invention;

[0018] Figure 5 This is a diagram showing the main waveforms of the bridge transformer isolation drive circuit of the present invention during operation;

[0019] Figure 6 Simulation of the output drive waveform of the bridge transformer isolation drive circuit of the present invention. Detailed Implementation

[0020] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0021] It should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integrally formed structures. Those skilled in the art can understand the specific meaning of these terms in this patent based on the specific circumstances.

[0022] High-voltage power supplies typically employ a full-bridge inverter topology composed of power switching transistors and a transformer-isolated converter topology, particularly resonant DC-DC topologies. These topologies often use frequency modulation control, with the bridge switching transistors driven by a 50% duty cycle PWM wave. The drive signals for the upper and lower transistors on the same bridge arm are complementary, but a certain dead time is required to prevent shoot-through short circuits. This type of power switch drive circuit must withstand the same operating potential difference as the power input / output terminals. When the potential difference is as high as 10KV or higher, transformer-isolated drive is more suitable. However, existing drive transformer schemes are often single-transistor drive methods, unable to simultaneously generate complementary PWM drive signals with dead time for the upper and lower transistors on the bridge arm. This invention provides a high-voltage isolated bridge arm drive circuit based on a single magnetic core to solve the above problems.

[0023] The high-voltage isolated bridge arm drive circuit based on a single magnetic core proposed in this invention can realize complementary PWM drive with dead time for two switching transistors in a half-bridge or four switching transistors in a full-bridge, reducing the number of drive transformers used and simplifying the design of the bridge drive circuit.

[0024] Existing bridge drive circuits with dead time consist of a primary-side PWM signal conditioning circuit, a primary-side drive circuit, a high-isolation drive transformer, and a secondary-side clamping circuit. For example... Figure 1 The diagram shows a half-bridge power topology; as shown... Figure 2 The diagram shows a full-bridge power topology.

[0025] The working principle of the drive circuit for the half-bridge power topology is explained below:

[0026] like Figure 3 As shown, this invention proposes a high-voltage isolated bridge arm drive circuit based on a single magnetic core, including a PWM signal conditioning circuit, a first buffer and inverting circuit, a second buffer and inverting circuit, a transistor drive circuit, a transformer, and a secondary clamping circuit.

[0027] The PWM signal conditioning circuit has at least one input pin and two output pins for inputting a 50% duty cycle PWM drive signal and a dead time signal; one output pin of the PWM signal conditioning circuit is connected to the input pin of the first buffer and inverting circuit, and the other output pin is connected to the input pin of the second buffer and inverting circuit through a delay unit, for converting one PWM signal into two complementary PWM signals with dead time to drive the transistor drive circuit.

[0028] The PWM signal is conditioned by a PWM signal conditioning circuit to produce a 50% duty cycle PWM drive signal and a dead time signal. The transistor drive circuit includes an upper transistor and a lower transistor located in the first bridge arm, and an upper transistor and a lower transistor located in the second bridge arm. The four transistors are named Q1, Q2, Q3, and Q4 respectively.

[0029] Both the first and second buffer and inverting circuits consist of buffers and inverters. The input pins of the buffers and inverters in the same path are connected to the output pins of the PWM signal conditioning circuit in the same path. The outputs of the two buffers are connected to the control electrodes of the upper and lower transistors of one of the bridge arms, respectively; that is, the buffer of the first buffer and inverting circuit is connected to the control electrode of transistor Q1 in the first bridge arm, and the buffer of the second buffer and inverting circuit is connected to the control electrode of transistor Q4 in the first bridge arm. The outputs of the two inverters are connected to the control electrodes of the upper and lower transistors of the other bridge arm, respectively; that is, the inverter of the first buffer and inverting circuit is connected to the control electrode of transistor Q2 in the second bridge arm, and the inverter of the second buffer and inverting circuit is connected to the control electrode of transistor Q3 in the second bridge arm.

[0030] Specifically, the original PWM signal conditioning circuit conditions the 50% duty cycle PWM drive signal and the dead time signal. After processing, it outputs four PWM signals to drive four transistors. The PWM drive signals are phase-shifted by a delay unit to generate the dead time, with the phase shift angle corresponding to the dead time. The first path directly outputs PWM1 after passing through a buffer, driving transistor Q1; the second path outputs PWM2 after passing through an inverter, driving transistor Q2; the third path outputs PWM3 after passing through a delay unit and an inverter, driving transistor Q3; and the fourth path outputs PWM4 after passing through a delay unit and a buffer, driving transistor Q4. The waveforms of the four PWM paths are as follows: Figure 5 As shown, the transistor drive circuit generates the VT1 voltage waveform under the modulation of four PWM signals, which includes positive and negative drive levels as well as the zero level corresponding to the dead time.

[0031] For details, please refer to the following: Figure 3The secondary-side clamping circuit consists of diode D1, bleed resistor R2, Zener diodes (D2 and D3), and drive resistor R1. The drive voltage VT1 is isolated by the drive transformer and then output to the secondary-side clamping circuit. Here, Cgs1 represents the equivalent capacitive load driving the power switch SW1. Diode D1 acts as a unidirectional conductor, allowing only forward voltage to reach the output. R2 provides a discharge path for the Cgs charge in the drive turn-off device. Zener diodes D2 and D3 clamp the voltage to the required drive level for the switch SW1. The drive resistor R1 limits the current and sets the rise time of the Vgs voltage, ensuring the power switch turns on and off at an appropriate speed.

[0032] As can be seen from the above description, the positive winding of the same name is output to the secondary clamping circuit, generating the driving voltage Vgs1 of the upper transistor SW1 of the bridge arm, and the negative winding of the same name is output to another clamping circuit on the secondary side, generating the driving voltage Vgs2 of the lower transistor SW2 of the bridge arm.

[0033] like Figure 5 As shown. When the primary side of the drive transformer is positively excited, due to the unidirectional conduction of diode D1, the positive voltage of VT1 outputs a drive signal through the isolation transformer. When the primary side of the drive transformer is negatively excited, due to the unidirectional conduction of diode D4, the negative voltage of VT1 outputs a drive signal through the isolation transformer. When the primary side of the drive transformer is zero-level excited, there is no drive signal output on the secondary side. The simulation yields the drive signal Vgs1 of the upper transistor SW1 and the drive signal Vgs2 of the lower transistor SW2 in the same bridge arm.

[0034] like Figure 6 As shown, the two PWM drive signals are complementary and have a set dead time between them, which meets the switching requirements of the bridge topology.

[0035] Finally, it should be noted that the high-voltage isolated bridge arm drive circuit based on a single magnetic core proposed in this invention can be applied not only to half-bridge power topology drive circuits but also to full-bridge drive circuits. The principles are the same; the difference lies in that the half-bridge power topology drive circuit drives both the upper and lower transistors of a single half-bridge arm simultaneously, while the full-bridge drive circuit drives both the upper and lower transistors of both bridge arms simultaneously. Figure 4 The diagram shown is a schematic of a full-bridge transformer isolation drive circuit, which will not be described in detail here.

[0036] The high-voltage isolated bridge arm drive circuit based on a single magnetic core proposed in this invention eliminates the need for a separate power supply to the secondary side, solving the problem of additional auxiliary power supply and avoiding the tens of kV withstand voltage isolation issue between the auxiliary power supply and the main circuit. By employing a single drive transformer, it achieves complementary isolation drive with dead time for all power switches in the bridge converter topology, simplifying the design of the isolation drive circuit and making it suitable for frequency modulation and proportional modulation control.

[0037] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-voltage isolated bridge arm drive circuit based on a single magnetic core, characterized in that, It includes a PWM signal conditioning circuit, a first-channel buffer and inverting circuit, a second-channel buffer and inverting circuit, a transistor driving circuit, a transformer, and a secondary-side clamping circuit; The PWM signal conditioning circuit has at least one input pin and two output pins for inputting a 50% duty cycle PWM drive signal and a dead time signal; one output pin of the PWM signal conditioning circuit is connected to the input pin of the first buffer and inverting circuit, and the other output pin is connected to the input pin of the second buffer and inverting circuit through a delay unit, for converting one PWM signal into two complementary PWM signals with dead time to drive the transistor drive circuit. The PWM signal is conditioned by the PWM signal conditioning circuit to form a 50% duty cycle PWM drive signal and a dead time signal. The transistor drive circuit includes an upper transistor and a lower transistor located in the first bridge arm, and an upper transistor and a lower transistor located in the second bridge arm. The four transistors are named Q1, Q2, Q3, and Q4 respectively. Both the first and second buffer and inverting circuits consist of buffers and inverters; the input pins of the buffers and inverters are connected to the output pins of the PWM signal conditioning circuits; the outputs of the first buffer circuit and the inverting circuit are connected to the control electrodes of the upper transistor Q1 and lower transistor Q2 of the first bridge arm, respectively; the outputs of the second inverting circuit and the buffer circuit are connected to the control electrodes of the upper transistor Q3 and lower transistor Q4 of the second bridge arm, respectively.

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