Soft-switching ultrasonic drive circuit and method of implementing the same

Abstract

The application discloses a soft-switching ultrasonic wave driving circuit and an implementation method thereof, and mainly solves the problem of low working efficiency of an existing ultrasonic wave transmitting circuit. The circuit is composed of a pulse driving circuit, an LLC soft-switching resonant circuit and an isolation transformer circuit. The driving circuit mainly generates oscillation through the LLC resonant circuit. In small-power to large-power ultrasonic wave signal transmission, the MOS tube is in conduction, and the voltage between the source S and the drain D of the MOS tube is 0 due to the conduction of the body diode (D3 and D4), so that zero-voltage conduction (i.e. soft-switching effect) is realized, and there is no power loss during conduction, and the working efficiency of the circuit can be obviously improved. Therefore, the application is suitable for wide promotion and application.

Description

Technical Field

[0001] This invention belongs to the field of ultrasonic sensor technology, specifically, it relates to a soft-switching ultrasonic driving circuit and its implementation method. Background Technology

[0002] In existing ultrasonic transmitter sensor drive circuits, the traditional method of converting DC signals into AC pulses using transistors such as MOSFETs, BJTs, or IGBTs via simple on / off switching is employed to drive the ultrasonic transmitter sensor. This method has very low efficiency and high transistor conduction losses. It cannot meet the requirements of instruments or industrial applications that demand energy conservation, environmental friendliness, or high efficiency.

[0003] Therefore, high-efficiency ultrasonic sensor drive circuits are particularly important. Utilizing a half-bridge LLC topology to achieve soft-switching can significantly improve circuit efficiency in the transmission of ultrasonic signals from low to high power. Summary of the Invention

[0004] The purpose of this invention is to provide a soft-switching ultrasonic driving circuit and its implementation method, mainly to solve the problem of low working efficiency of existing ultrasonic transmitting circuits.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A soft-switching ultrasonic drive circuit comprises a pulse drive circuit, an LLC soft-switching resonant circuit, and an isolation transformer circuit.

[0007] The pulse drive circuit includes a transformer T2 with one primary input and two secondary outputs, a resistor R3 with one end connected to the same-name terminal of one secondary output, a resistor R6 with one end connected to the opposite-name terminal of the same secondary output and the other end connected to the other end of resistor R3, an NMOS transistor Q1 with its gate connected to the common terminal of resistors R3 and R6, a resistor R5 with one end connected to the same-name terminal of the other secondary output, and a resistor R5 with one end connected to the opposite-name terminal of the same secondary output. The other end is connected to resistor R4, and NMOS transistor Q2 is connected to the common terminal of resistors R4 and R5; the source of NMOS transistor Q1 is connected to the drain of NMOS transistor Q2 and connected to the opposite terminal of the secondary output terminal connected to resistor R6; the drain of NMOS transistor Q1 is connected to voltage VCC, and the source of NMOS transistor Q2 is connected to the same terminal of the secondary output terminal connected to resistor R5 and then grounded; the input terminal of the LLC soft-switching resonant circuit is connected to the source of NMOS transistor Q1;

[0008] The LLC soft-switching resonant circuit includes an inductor L1, a capacitor C1, and a capacitor C2 connected at one end to the source of an NMOS transistor Q1; a diode D1 connected in parallel across capacitor C1 with its cathode connected to voltage VCC; a resistor R1 connected in parallel across diode D1; a diode D2 connected in parallel across capacitor C2 with its anode grounded; a resistor R2 connected in parallel across diode D2; and an inductor L2 connected at one end to the other end of inductor L1 and at the other end to the cathode of diode D2. The other end of capacitor C1 is connected to voltage VCC, the other end of capacitor C2 is grounded, and an isolation transformer circuit is connected in parallel across inductor L2.

[0009] The isolation transformer circuit includes a transformer T1 with its two primary input terminals connected to the two ends of inductor L2, a resistor R7 with one end connected to the same-name terminal of the secondary output terminal of transformer T1, a Zener diode D6 with its anode connected to the other end of resistor R7 and its cathode connected to the opposite-name terminal of the secondary output terminal of transformer T1, and a Zener diode D5 with its anode connected to the cathode of Zener diode D6 and its cathode connected to the anode of Zener diode D6; wherein, the two ends of Zener diode D5 serve as the output terminals of the ultrasonic drive circuit.

[0010] Based on the above-described driving circuit, the present invention also provides a method for implementing a soft-switching ultrasonic driving circuit, comprising the following steps:

[0011] S1, Calculate and determine the transmission frequency Fp of the ultrasonic transmitter driven by the ultrasonic drive circuit;

[0012] S2 makes the capacitance values ​​of capacitors C1 and C2 equal, the resonant frequency of inductor L1 with capacitor C1 or C2 is Fr, and the resonant frequency of inductor L1+L2 with capacitor C1 or C2 is Fm.

[0013] S3, ensures that the magnitude of the input PWM frequency Fp satisfies Fr>Fp>Fm;

[0014] When NMOS transistors Q1 and Q2 are turned on, due to the resonance effect of the LLC soft-switching resonant circuit during normal operation, the voltage between the source (S) and drain (D) of NMOS transistors Q1 and Q2 is 0. According to the power P = UI, the ultrasonic transmitter is finally driven with high efficiency.

[0015] Furthermore, in this invention, the body diodes of NMOS transistors Q1 and Q2 are turned on when the MOS transistors are turned on.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] This invention generates oscillation through an LLC resonant circuit. In the transmission of ultrasonic signals from low power to high power, when the MOSFET is turned on, the voltage between its source (S) and drain (D) is 0 due to the conduction of its body diodes (D3 and D4), thus achieving zero-voltage conduction (i.e., soft switching). There is no power loss when conducting, which can significantly improve the circuit's operating efficiency. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the circuit structure of the present invention. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments. The embodiments of the present invention include, but are not limited to, the following embodiments.

[0020] like Figure 1 As shown, the present invention discloses a soft-switching ultrasonic driving circuit, which consists of a pulse driving circuit, an LLC soft-switching resonant circuit and an isolation transformer circuit, and is used in applications that drive ultrasonic transmitting sensors.

[0021] The pulse drive circuit includes a transformer T2 with a primary input and two secondary outputs; a resistor R3 connected at one end to the same-name terminal of one secondary output; a resistor R6 connected at one end to the opposite-name terminal of the same secondary output and at the other end of resistor R3; an NMOS transistor Q1 with its gate connected to the common terminal of resistors R3 and R6; a resistor R5 connected at one end to the same-name terminal of the other secondary output; a resistor R4 with one end connected to the opposite-name terminal of the same secondary output and at the other end of resistor R5; and a resistor R4 with its gate connected to the common terminal of resistors R4 and R5. The NMOS transistor Q2 is connected to the common terminal; the source of NMOS transistor Q1 is connected to the drain of NMOS transistor Q2 and connected to the opposite terminal of the secondary output terminal connected by resistor R6; the drain of NMOS transistor Q1 is connected to voltage VCC, and the source of NMOS transistor Q2 is connected to the same terminal of the secondary output terminal connected by resistor R5 and then grounded; the input terminal of the LLC soft-switching resonant circuit is connected to the source of NMOS transistor Q1; two PWM signals are input from the two ports of the primary input terminal of transformer T2, and the input PWM signals Fp are complementary PWM with a duty cycle of 50%.

[0022] The LLC soft-switching resonant circuit includes an inductor L1, a capacitor C1, and a capacitor C2 connected at one end to the source of an NMOS transistor Q1; a diode D1 connected in parallel across capacitor C1 with its cathode connected to voltage VCC; a resistor R1 connected in parallel across diode D1; a diode D2 connected in parallel across capacitor C2 with its anode grounded; a resistor R2 connected in parallel across diode D2; and an inductor L2 connected at one end to the other end of inductor L1 and at the other end to the cathode of diode D2. The other end of capacitor C1 is connected to voltage VCC, the other end of capacitor C2 is grounded, and an isolation transformer circuit is connected in parallel across inductor L2.

[0023] The isolation transformer circuit includes a transformer T1 with its two primary input terminals connected to the two ends of inductor L2, a resistor R7 with one end connected to the same-name terminal of the secondary output terminal of transformer T1, a Zener diode D6 with its anode connected to the other end of resistor R7 and its cathode connected to the opposite-name terminal of the secondary output terminal of transformer T1, and a Zener diode D5 with its anode connected to the cathode of Zener diode D6 and its cathode connected to the anode of Zener diode D6; wherein, the two ends of Zener diode D5 serve as the output terminals of the ultrasonic drive circuit.

[0024] Based on the above-described driving circuit, the present invention also provides a method for implementing a soft-switching ultrasonic driving circuit, comprising the following steps:

[0025] S1, Calculate and determine the transmission frequency Fp of the ultrasonic transmitter driven by the ultrasonic drive circuit;

[0026] S2 makes the capacitance values ​​of capacitors C1 and C2 equal, the resonant frequency of inductor L1 with capacitor C1 or C2 is Fr, and the resonant frequency of inductor L1+L2 with capacitor C1 or C2 is Fm.

[0027] S3, ensures that the magnitude of the input PWM frequency Fp satisfies Fr>Fp>Fm;

[0028] When NMOS transistors Q1 and Q2 are turned on (S4), due to the resonance effect of the LLC soft-switching resonant circuit during normal operation, the voltage between the source (S) and drain (D) of NMOS transistors Q1 and Q2 is 0. According to the power formula P = UI, high-efficiency driving of the ultrasonic transmitter is ultimately achieved. The body diodes of NMOS transistors Q1 and Q2 are conducting when the transistors are turned on. Since the voltage between their source (S) and drain (D) is 0, zero-voltage conduction (i.e., soft-switching) is achieved. There is no power loss during conduction, thus improving circuit efficiency.

[0029] The above embodiments are merely one of the preferred embodiments of the present invention and should not be used to limit the scope of protection of the present invention. Any modifications or refinements made to the main design concept and spirit of the present invention that are not of substantial significance, but solve the same technical problem as the present invention, should be included within the scope of protection of the present invention.

Claims

1. A soft-switching ultrasonic drive circuit, characterized in that, It consists of a pulse drive circuit, an LLC soft-switching resonant circuit, and an isolation transformer circuit; The pulse drive circuit includes a transformer T2 with one primary input and two secondary outputs, a resistor R3 with one end connected to the same-name terminal of one secondary output, a resistor R6 with one end connected to the opposite-name terminal of the same secondary output and the other end connected to the other end of resistor R3, an NMOS transistor Q1 with its gate connected to the common terminal of resistors R3 and R6, a resistor R5 with one end connected to the same-name terminal of the other secondary output, and a resistor R5 with one end connected to the opposite-name terminal of the same secondary output. The other end is connected to resistor R4, and NMOS transistor Q2 is connected to the common terminal of resistors R4 and R5; the source of NMOS transistor Q1 is connected to the drain of NMOS transistor Q2 and connected to the opposite terminal of the secondary output terminal connected to resistor R6; the drain of NMOS transistor Q1 is connected to voltage VCC, and the source of NMOS transistor Q2 is connected to the same terminal of the secondary output terminal connected to resistor R5 and then grounded; the input terminal of the LLC soft-switching resonant circuit is connected to the source of NMOS transistor Q1; The LLC soft-switching resonant circuit includes an inductor L1, a capacitor C1, and a capacitor C2 connected at one end to the source of an NMOS transistor Q1; a diode D1 connected in parallel across capacitor C1 with its cathode connected to voltage VCC; a resistor R1 connected in parallel across diode D1; a diode D2 connected in parallel across capacitor C2 with its anode grounded; a resistor R2 connected in parallel across diode D2; and an inductor L2 connected at one end to the other end of inductor L1 and at the other end to the cathode of diode D2. The other end of capacitor C1 is connected to voltage VCC, the other end of capacitor C2 is grounded, and an isolation transformer circuit is connected in parallel across inductor L2. The isolation transformer circuit includes a transformer T1 with its two primary input terminals connected to the two ends of inductor L2, a resistor R7 with one end connected to the same-name terminal of the secondary output terminal of transformer T1, a Zener diode D6 with its anode connected to the other end of resistor R7 and its cathode connected to the opposite-name terminal of the secondary output terminal of transformer T1, and a Zener diode D5 with its anode connected to the cathode of Zener diode D6 and its cathode connected to the anode of Zener diode D6; wherein, the two ends of Zener diode D5 serve as the output terminals of the ultrasonic drive circuit.

2. A method for implementing a soft-switching ultrasonic drive circuit, characterized in that, The soft-switching ultrasonic drive circuit as described in claim 1 includes the following steps: S1, Calculate and determine the transmission frequency Fp of the ultrasonic transmitter driven by the ultrasonic drive circuit; S2 makes the capacitance values ​​of capacitors C1 and C2 equal, the resonant frequency of inductor L1 with capacitor C1 or C2 is Fr, and the resonant frequency of inductor L1+L2 with capacitor C1 or C2 is Fm. S3, make the magnitude of the input PWM frequency Fp satisfy Fr>Fp>Fm; When NMOS transistors Q1 and Q2 are turned on, due to the resonance effect of the LLC soft-switching resonant circuit during normal operation, the voltage between the source (S) and drain (D) of NMOS transistors Q1 and Q2 is 0. According to the power P=UI, the ultrasonic transmitter is finally driven with high efficiency.

3. The method for implementing a soft-switching ultrasonic drive circuit according to claim 2, characterized in that, The body diodes of NMOS transistors Q1 and Q2 are conducting when the MOS transistors are turned on.

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