Modulation and bipolar high-voltage square wave generation circuit

Abstract

The invention discloses a modulatable and bipolar high-voltage square wave generating circuit, which comprises a power supply unit, a low-voltage square wave generating unit, a high-voltage amplifying unit, an adjusting unit and an MCU (Microprogrammed Control Unit), the power supply unit comprises a low-voltage unit and a high-voltage unit, the low-voltage square wave generating unit comprises a grid driving chip U6, an MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor) Q1 and an MOSFET Q2, the high-voltage amplifying unit comprises an operational amplifier U1, and the high-voltage amplifying unit comprises a high-voltage amplifying unit, an adjusting unit and an MCU (Microprogrammed Control Unit). The power supply of the operational amplifier U1 is connected with the high-voltage unit, the input signal of the high-voltage amplifying unit is connected with the low-voltage square wave generating unit, the adjusting unit comprises a digital potentiometer U10, the adjusting unit is connected with the MCU unit, and the MCU unit is connected with the power supply unit, and is connected with and controls the input level of the gate driving chip U6. The amplitude and the frequency of a low-voltage square wave signal are adjusted through the gate driving chip U6 and the digital potentiometer U10, and then the amplitude and the frequency of a bipolar high-voltage square wave circuit are adjusted through the operational amplifier U1 in the high-voltage amplification unit, so that multi-voltage adjustment in the microfluidic liquid drop driving process is facilitated.

Description

Technical Field

[0001] The invention belongs to the technical field of microfluidics and relates to a modulatable bipolar high-voltage square wave generating circuit. Background Art

[0002] Digital microfluidics is a micro-droplet processing technology based on the principle of electrowetting. When a high voltage is applied to the electrode, the wettability of the solid-liquid interface at the corresponding position of the electrode and the contact angle between the electrode and the droplet change, generating a lateral driving force, causing the droplet to deform and displace on the electrode substrate. Multiple electrodes are arranged in a certain pattern to form a microfluidic chip. The high voltage signal of the microfluidic chip where the droplet is located at different times is controlled by the electrode control circuit, so that the droplet can be moved arbitrarily on the entire two-dimensional microfluidic chip.

[0003] At present, in the microfluidics field, for droplet-driven high-voltage circuits, only one of the amplitude or frequency can be adjusted during the drive control process, which is rather troublesome and has problems such as unstable drive control and AC high voltage distortion. Summary of the invention

[0004] In view of the above problems, the present invention proposes a modulated, bipolar high-voltage square wave generating circuit, which well solves the problems in the prior art.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A modulatable, bipolar high-voltage square wave generating circuit, comprising:

[0007] A power supply unit, the power supply unit includes a low voltage unit and a high voltage unit, the high voltage unit includes a high voltage power conversion chip U4, and the low voltage unit includes a low voltage power conversion chip U9;

[0008] A low-voltage square wave generating unit, the low-voltage square wave generating unit comprising a gate driving chip U6 and a MOSFET tube Q1 and a MOSFET tube Q2 connected to a DRV_HI pin and a DRV_LO pin of the gate driving chip U6;

[0009] A high-voltage amplifying unit, the high-voltage amplifying unit comprising an operational amplifier U1, the operational amplifier U1 power supply is connected to the high-voltage unit, and the high-voltage amplifying unit input signal is connected to the low-voltage square wave generating unit;

[0010] An MCU unit, the MCU unit is connected to the power supply unit, and the MCU unit is connected to and controls the input level of the gate drive chip U6;

[0011] The regulating unit includes a digital potentiometer U10, and the regulating unit is connected to the MCU unit and the power supply unit.

[0012] Optionally, the digital potentiometer U10 is connected to the low-voltage power conversion chip U9, the low-voltage power conversion chip U9 is connected to an inductor L2, a bootstrap capacitor C21, and a resistor R21, the digital potentiometer U10 is connected to a resistor R22, and the SDA pin and SCL pin of the digital potentiometer U10 are connected to the MCU unit.

[0013] Optionally, the power conversion chip U9 is connected to the MOSFET tube Q1, and the signal output end of the low-voltage square wave generating unit is connected to the signal input end of the operational amplifier U1.

[0014] Optionally, the low voltage unit includes a filter capacitor C22, a filter capacitor C23, a filter capacitor C25, and a filter capacitor C26.

[0015] Optionally, the low voltage unit includes a signal pull-down resistor R20, a pull-up resistor R23, and a pull-up resistor R24.

[0016] Optionally, the high voltage unit includes a high voltage power conversion chip U4 and a current detection chip U5, and the power conversion chip U4 is connected to a current limiting resistor R11, a current limiting resistor R13, a current limiting resistor R14, a current limiting resistor R15, an input filter capacitor C12, a filter capacitor C13, a filter capacitor C15 and an output filter capacitor C14.

[0017] Optionally, the high-voltage amplification unit includes a filter capacitor C1, a filter capacitor C8, a filter capacitor C9, a filter capacitor C10, a filter capacitor C11, an anti-reverse diode D4, and an anti-reverse diode D5.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] Through the switching characteristics of the MOSFET tube and the DC blocking and AC passing characteristics of the capacitor, a frequency and amplitude modulated bipolar high-voltage square wave generating circuit is realized when the MCU controls the gate drive chip and the digital potentiometer. The amplitude and frequency of the bipolar square wave up to ±450V can be modulated at the same time, with a wide amplitude variation range and a wide frequency variation range. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a schematic diagram of the overall structure of an embodiment of the present invention;

[0021] Figure 2 is a circuit diagram of a low voltage square wave generating unit according to an embodiment of the present invention;

[0022] Figure 3 is a circuit diagram of a high voltage amplification unit according to an embodiment of the present invention;

[0023] Figure 4 is a circuit diagram of a low voltage unit and a regulating unit according to an embodiment of the present invention;

[0024] Figure 5 is a circuit diagram of a high voltage unit according to an embodiment of the present invention;

[0025] Figure 6 It is a circuit diagram of a high voltage amplifying unit, a regulating unit and a low voltage unit according to another embodiment of the present invention. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] See also Figure 1 , a modulatable, bipolar high-voltage square wave generating circuit disclosed in an embodiment of the present invention, includes a power supply unit, a low-voltage square wave generating unit, a high-voltage amplifying unit, an adjusting unit and an MCU unit, the power supply unit includes a low-voltage unit and a high-voltage unit, the low-voltage square wave generating unit includes a gate driving chip U6 and a MOSFET tube Q1 and a MOSFET tube Q2 connected to the DRV_HI pin and the DRV_LO pin of the gate driving chip U6, the high-voltage amplifying unit includes an operational amplifier U1, the power supply of the operational amplifier U1 is connected to the high-voltage unit, the input signal of the high-voltage amplifying unit is connected to the low-voltage square wave generating unit, the adjusting unit includes a digital potentiometer U10, the adjusting unit is connected to the MCU unit, the MCU unit is connected to the power supply unit, and the gate driving chip U6 input level is connected and controlled.

[0028] Specifically, the gate drive chip U6 is connected through the MCU unit to control the on and off of the MOSFET tube Q1 and the MOSFET tube Q2, thereby generating a low-voltage square wave signal. The low-voltage square wave signal enters the high-voltage amplification unit and is amplified by the operational amplifier U1.

[0029] In this way, before the low-voltage square wave signal of the low-voltage square wave generating unit enters the high-voltage amplifying unit, the amplitude and frequency of the low-voltage square wave signal can be adjusted through the digital potentiometer U10 and the gate drive chip U6, and then the amplitude and frequency of the bipolar high-voltage square wave circuit can be adjusted through the operational amplifier U1 in the high-voltage amplifying unit, which facilitates the adjustment of multiple voltages in the process of microfluidic driving droplets.

[0030] For some possible approaches, see Figure 2, the gate driver chip U6 can be selected as NCP5304DR2G or IR2103STRPBF, the MOSFET tube Q1 and MOSFET tube Q2 can be selected as IRLRO24NTRPBF or NCE6050KA, the input signals IN_L and IN_H are connected to the MCU unit, and also include bootstrap diode D8, bootstrap capacitor C16, filter capacitors C17, C18, C20, isolation capacitor C19, current limiting resistors R16, R17, R18, pull-down resistor R19, filter inductor L1. When the MCU unit periodically controls IN_L and IN_H, U6 pins 5 and 7 will periodically generate high and low levels, but the levels of U6 pins 5 and 7 are always in opposite states. According to the input and output logic of U6, when IN_L is high and IN_H is low, U6 pin 5 is high level, U6 pin 7 is low level, MOSFET tube Q2 is turned on, Q1 is turned off, and SIG_Q is 0V; when IN_L is low and IN_H is high, U6 pin 5 is low level, U6 pin 7 is high level, Q1 is turned on, MOSFET tube Q2 is turned off, and SIG_Q is V_HV. When IN_L and IN_H change high and low levels periodically at a frequency f, SIG_Q changes periodically between 0V and V_HV, thereby generating a unipolar low-voltage square wave signal SIG_Q with a frequency of f and an amplitude of V_HV. When the switching frequency of IN_L and IN_H is changed, the frequency of the low-voltage square wave signal SIG_Q will change accordingly. In this embodiment, when the switching frequency of IN_L and IN_H changes between 1KHz and 10KHz, the frequency of the low-voltage square wave signal SIG_Q also changes between 1KHz and 10KHz. Capacitor C19 has the function of isolating DC and passing AC. When the SIG_Q signal passes through C19, the DC component V_HV / 2 is isolated, thereby generating a bipolar low-voltage square wave signal SIG_SQURE with a frequency of f and an amplitude of ±V_HV / 2.

[0031] See also Figure 3 The operational amplifier U1 can be PA95 or PA94. In this embodiment, PA95 is used. The high voltage unit is a high voltage power supply input to the +VS and -VS terminals of U1. In this embodiment, the high voltage unit is a ±450V high voltage power supply. The amplification factor of U1 is AVF

[0032]

[0033] When the input frequency is f and the amplitude is ±V_HV / 2, the bipolar low-voltage square wave signal SIG_SQURE is output, and the amplitude is amplified by AVF times compared to SIG_SQURE, and the frequency remains unchanged. In this embodiment, R4, R5, R6, R7, and R8 are all 100KΩ, and R9 is 5KΩ. It can be calculated that the AVF of U1 is 100, and the HV_AC amplitude is ±37V~±400V. The high-voltage amplifier unit is also provided with filter capacitors C1, C8, C9, C10, and C11, anti-reverse diodes D4 and D5, TVS diodes D6 and D7, forward end matching resistors R10, and current limiting resistors R1.

[0034] As a specific implementation of a modulatable, bipolar high-voltage square wave generating circuit provided by the application, please refer to Figure 4 The digital potentiometer U10 is connected to the low-voltage power conversion chip U9, the low-voltage power conversion chip U9 is connected to the inductor L2, the bootstrap capacitor C21, and the resistor R21, the digital potentiometer U10 is connected to the resistor R22, and the SDA pin and the SCL pin of the digital potentiometer U10 are connected to the MCU unit.

[0035] In general, the output voltage amplitude of the low-voltage unit is changed by adjusting the digital potentiometer U10.

[0036] In some feasible ways, the low voltage power conversion chip U9 can be selected as TPS54302DDCR or TP6841S6, and the digital potentiometer U10 can be selected as CAT5171TBI-50GT3 or AD5245BRJZ50-RL7. When the MCU controls U10 through the SDA pin and the SCL pin, the resistance R_U10 between pin 1 and pin 7 of U10 can be changed between 0Ω and 50KΩ. When 12V power is input to U9 and V_HV_EN is high, U9 charges the bootstrap capacitor C21 and the inductor L2. After charging is completed, the device starts to work. The output voltage of U9 is V_HV:

[0037]

[0038] The voltage of U9 pin 4 is fixed at 0.596V, R21 and R22 are fixed values, when R_U10 is adjusted, the ratio of R21 and R_U10+R22 changes, according to Ohm's law, the size of V_HV changes. When R_U10 is 0Ω, V_HV is 8.0V, when R_U10 is 50KΩ, V_HV is 0.74V, it can be concluded that the adjustment range of the output voltage V_HV is 0.74V~8.0V. The low voltage unit also includes filter capacitors C22, C23, C24, C25, C26, pull-up resistors R23, R24 and pull-down resistor R20 to ensure the state of the signal when it is not controlled.

[0039] As another specific implementation of a modulatable, bipolar high-voltage square wave generating circuit provided by the application, please refer to Figure 5 The high-voltage unit includes a high-voltage power conversion chip U4 and a current detection chip U5. The power conversion chip U4 is connected to a current limiting resistor R11, a current limiting resistor R13, a current limiting resistor R14, a current limiting resistor R15, an input filter capacitor C12, a filter capacitor C13, a filter capacitor C15 and an output filter capacitor C14.

[0040] In combination with specific usage scenarios, the current of U4 is monitored by setting a high-voltage power conversion chip U4 and a current detection chip U5.

[0041] In some feasible ways, the high-voltage power conversion chip U4 can be selected as HRA24450 or HRB24350D. When a 24V power supply is input, U4 will generate a bipolar high voltage of ±450V. U5 can be selected as INA181A2IDBVR, which monitors the current size of the 24V input and transmits it to the MCU through ADC_HVCD. U5 uses the resistor R12 connected to the high-voltage power conversion chip U4 as a sampling resistor, and also includes current limiting resistors R11, R13, R14, and R15, ground isolation resistor RN1, power supply filter capacitors C12, C13, and C15, and output filter capacitor C14 of signal ADC_HVCD.

[0042] In another specific embodiment, see Figure 6 The power conversion chip U9 is connected to the MOSFET tube Q1, and the signal output end of the low-voltage square wave generating unit is connected to the signal input end of the operational amplifier U1.

[0043] It should be understood that by keeping V_HV fixed and changing the amplification factor AVF of U1, the circuit is controlled to adjust the amplitude of the signal.

[0044] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A modulatable, bipolar high voltage square wave generating circuit, characterized in that: include: A power supply unit, the power supply unit includes a low voltage unit and a high voltage unit, the high voltage unit includes a high voltage power conversion chip U4, and the low voltage unit includes a low voltage power conversion chip U9; A low-voltage square wave generating unit, the low-voltage square wave generating unit comprising a gate driving chip U6 and a MOSFET tube Q1 and a MOSFET tube Q2 connected to a DRV_HI pin and a DRV_LO pin of the gate driving chip U6; A high-voltage amplifying unit, the high-voltage amplifying unit comprising an operational amplifier U1, the operational amplifier U1 power supply is connected to the high-voltage unit, and the high-voltage amplifying unit input signal is connected to the low-voltage square wave generating unit; An MCU unit, the MCU unit is connected to the power supply unit, and the MCU unit is connected to and controls the input level of the gate drive chip U6; The regulating unit includes a digital potentiometer U10, and the regulating unit is connected to the MCU unit and the power supply unit.

2. The modulatable, bipolar high-voltage square wave generating circuit according to claim 1, characterized in that: The digital potentiometer U10 is connected to the low-voltage power conversion chip U9, the low-voltage power conversion chip U9 is connected to an inductor L2, a bootstrap capacitor C21, and a resistor R21, the digital potentiometer U10 is connected to a resistor R22, and the SDA pin and the SCL pin of the digital potentiometer U10 are connected to the MCU unit.

3. The modulatable, bipolar high-voltage square wave generating circuit according to claim 1, characterized in that: The power conversion chip U9 is connected to the MOSFET tube Q1, and the signal output end of the low-voltage square wave generating unit is connected to the signal input end of the operational amplifier U1.

4. A modulatable, bipolar high voltage square wave generating circuit according to any one of claims 2 or 3, characterized in that: The low voltage unit includes a filter capacitor C22, a filter capacitor C23, a filter capacitor C25, and a filter capacitor C26.

5. A modulatable, bipolar high voltage square wave generating circuit according to any one of claims 2 or 3, characterized in that: The low voltage unit includes a signal pull-down resistor R20, a pull-up resistor R23, and a pull-up resistor R24.

6. The modulatable, bipolar high-voltage square wave generating circuit according to claim 1, characterized in that: The high voltage unit includes a high voltage power conversion chip U4 and a current detection chip U5. The power conversion chip U4 is connected to current limiting resistors R11, R13, R14, R15, input filter capacitors C12, C13, C15 and output filter capacitors C14.

7. The modulatable, bipolar high-voltage square wave generating circuit according to claim 1, characterized in that: The high voltage amplifying unit includes filter capacitors C1, C8, C9, C10, C11, anti-reverse diodes D4 and D5.

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