Piezoelectric ceramic actuators are a new type of micro-displacement device developed in recent years, characterized by small size, large thrust, high precision and displacement resolution, and fast frequency response. They operate without noise or heat, making them ideal micro-displacement devices, and have been widely used in aerospace, precision measurement, robotics, and precision machining. The performance of the driving power supply has a significant impact on piezoelectric ceramic actuators. While China has made some progress in the development of static piezoelectric ceramic driving power supplies in recent years, most of these power supplies are composed of discrete components, resulting in complex structures and a tendency to self-oscillate, which affects the stability of the power supply. In contrast, driving power supplies using high-voltage operational amplifiers can achieve mV-level resolution and have lower output ripple, improving both circuit integration and reliability, thus making them suitable for driving piezoelectric ceramic actuators. Piezoelectric ceramic actuator drive power supply 1 Requirements for drive power supply of piezoelectric ceramic actuator The drive power supply of piezoelectric ceramic actuator should have the following characteristics: (1) The response speed of the displacement output of piezoelectric ceramic actuator to the applied drive control voltage mainly depends on the magnitude of the drive current of the drive power supply. Therefore, the drive power supply should have a large drive current, generally not less than 150mA; (2) The output control voltage of the drive power supply should be continuously adjustable. For the domestic piezoelectric ceramic actuator PTBS200 series, the output voltage of the drive power supply should be DC 0～200V, continuously adjustable; (3) In order to meet the requirements of high frequency response, the drive power supply should have a circuit for rapid discharge of capacitive load; (4) Since piezoelectric ceramic actuator is mainly used in the field of micro and nano technology, the drive power supply should have good stability, and its output ripple voltage should be controlled within a very small range; (5) In order to realize automatic displacement control, the drive power supply is best controlled by computer. The external circuit of piezoelectric ceramic actuator is a capacitive load, and there are hysteresis and creep phenomena. The drive power supply can generally be divided into charge control type and voltage control type. Charge-controlled drive power supplies, based on the principle of capacitor charging (each piezoelectric ceramic plate is equivalent to a parallel-plate capacitor for the applied voltage), can improve the hysteresis and creep of piezoelectric ceramics. Voltage-controlled drive power supplies mainly come in two forms: one is a switching drive power supply based on the DC/DC converter principle, which is small in size and highly efficient, but has a large output ripple and a narrow frequency response range; the other is a DC amplification power supply, which has a wide frequency response range and, judging from development trends, has broad application prospects. 2. Drive Power Supply Design Based on the requirements of the piezoelectric ceramic actuator for its drive power supply, the power supply in this design adopts a DC amplification circuit. The circuit principle block diagram is shown in Figure 1. The entire power supply circuit mainly consists of a computer and data acquisition card, an operational amplifier circuit, and a high-voltage circuit. The high-voltage circuit provides a 220V DC voltage. The computer controls the data acquisition card via LabVIEW 8.5 to generate a certain output waveform, obtaining a continuously adjustable control voltage of 0-5V. The amplifier circuit realizes linear voltage amplification and power amplification, outputting a continuously adjustable DC voltage of 0-200V, and determines the resolution and stability of the power supply output voltage, making it the key to the entire power supply. [align=center] Figure 1 Power Supply Principle Block Diagram[/align] ① High-Voltage Circuit [align=center] Figure 2 High-Voltage Circuit Principle Diagram[/align] Since the stability of the DC voltage directly affects the stability of the drive power supply, a high-voltage circuit with a 220V output voltage (see Figure 2) is used. The main part is a full-bridge rectifier power supply circuit that converts the AC 220V mains voltage into a +220V DC voltage. ② Waveform Generation Circuit A good input waveform is one of the keys to the power supply, relating to the expansion and contraction of the piezoelectric ceramic. The frequency and amplitude of the input waveform signal are variable, and the signal waveform is good with little distortion. This not only eliminates the hysteresis and creep characteristics of the piezoelectric ceramic itself, but also allows for wider applications. Due to the high voltage accuracy requirements, the NI 6221 multi-function data acquisition card with 16-bit analog input/output is used to convert digital signals into analog signals. The output voltage is 0-5V, with a voltage resolution of 5/216, approximately 0.076mV. LabVIEW 8.5 programming allows for arbitrary waveforms and gradually changing DC outputs, offering high flexibility and meeting various needs. ③ High-voltage amplifier circuit [align=center] Figure 3 High-voltage amplifier circuit schematic[/align] A series negative feedback amplifier circuit is formed by connecting the high-voltage operational amplifier PA96 and the high-precision operational amplifier OP07 manufactured by APEX Corporation, as shown in Figure 3. The PA96 is a high-voltage, wide-bandwidth MOSFET operational amplifier with an output current of 1.5A and an output voltage close to 300V. Its safe operating area (SOA) has no secondary breakdown limitation; by selecting a suitable current-limiting resistor, a safe operating curve under any load can be observed. The maximum offset voltage of the PA96 is 5mV, which is insufficient for piezoelectric ceramic drive power supplies requiring a resolution below 10mV. In the linear amplification section of this power supply, a composite amplifier consisting of PA96 and OP07 connected in series is used, so that the input offset voltage is controlled by the preamplifier OP07. Since the input voltage of the composite amplifier is 0-5V and the output voltage requirement is 0-200V, the required gain of the composite amplifier is 40. However, excessive gain will affect the stability of the op-amp; therefore, the closed-loop gain of PA96 is selected as 31, and the combined gain provided by PA96 and OP07 in series is 40. Based on the gain allocation requirements, we have: R1=3kΩ, R2=117Ω, R3=180Ω, R4=6kΩ. Due to the negative feedback circuit, the output resistance is very small (mΩ level), thus possessing strong load-carrying capacity. R5 in Figure 3 is the current-limiting resistor, whose value can be obtained from the formula IL=0.68V/R5=125mA, and here it is 5.4Ω. 3. Phase Compensation and Output Protection Self-oscillation is a major factor affecting power supply stability. When the open-loop gain of an integrated operational amplifier (op-amp) is constant, excessive phase shift can cause oscillations in the circuit. Therefore, phase compensation is necessary. This is typically achieved by connecting external compensation components at the input and output terminals. Phase compensation not only improves the stability of the op-amp but also extends its bandwidth. In this circuit, the closed-loop gain of the PA96 stage is 31, resulting in a calculated gain of 30. Based on the PA96 datasheet, the phase compensation capacitor value CC = 10pF, resulting in a closed-loop bandwidth of approximately 1MHz. The feedback capacitors C1 and C6 in Figure 3 enhance the stability of the amplifier circuit at high frequencies. Diodes D1 and D2 at the OP07 input provide differential-mode and common-mode protection against transient overvoltages, while output diodes D3 and D4 protect against transient overvoltages, preventing damage to the OP07 output. Diodes D5, D6, D7, and D8 at the PA96 amplifier input clamp the voltages at the positive and negative input terminals within a specified range, protecting the op-amp. Experimental Results and Conclusions of the Driver Power Supply The output characteristics of the regulated power supply were tested using a high-precision FLUKE 8580A voltmeter in the 0-200V range. The measured data and input voltage were compared (see Table 1). Linear regression analysis showed that the linear correlation coefficient r≈1 for the regulated power supply output, indicating good output linearity. Under continuous operation with load, the output voltage drift of the driver power supply was less than 10mV, and the output ripple voltage was less than 10mV. This ripple voltage has a minimal impact on the displacement accuracy of the piezoelectric ceramic in the micro-positioning system. [img=543,32]http://www.21ic.com/news/upload/2008_11/081125132849954.jpg[/img]