Design of the hottest CNC high voltage power suppl

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Design of NC high-voltage power supply

Abstract: This paper introduces a design scheme of NC high-voltage power supply, which organically combines single-chip microcomputer digital control technology with high-voltage power supply technology. The input of the high-voltage power supply system is mains power, and the output is 0 ~ 4KV continuously adjustable DC. The maximum output current is 10mA, and the maximum voltage fluctuation is 5%. It has the advantages of stable output, convenient adjustment, small volume and strong versatility

key words: high voltage power supply computer control single chip microcomputer

Chinese Library Classification Number: tm835 document identification code: a article number: (2006)

I. Introduction

in recent years, with the development of power supply technology, the technology of low-voltage power supply in multi-function and digitization has become mature, but more general high-voltage power supply is rare. In view of the requirements of high-voltage control power supply devices in engineering technology fields such as ER technology and voltage withstand test of devices, a numerical control high-voltage power supply device is designed and manufactured with single-chip microcomputer as the core and the row output transformer of TV as the high-frequency step-up transformer

II. System working principle

the block diagram of CNC high voltage power supply system is shown in Figure 1. The keyboard inputs the required voltage value to the single chip microcomputer, and the single chip microcomputer compares the value with the voltage feedback value to obtain the deviation. After calculating according to a certain control algorithm, it outputs a digital control quantity, and provides a control signal to the high-frequency control circuit through the d/a converter. The high-frequency control circuit then performs boost, rectification and filtering processing, and outputs the required high-voltage signal to the high-voltage component

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Figure 1 block diagram of CNC high voltage power supply system

III. design of single chip microcomputer control system

the design of CNC high voltage power supply is based on single chip microcomputer. The single chip microcomputer sets the voltage, controls the voltage in a closed loop, and displays the output voltage, output current and other parameters in real time. The system adopts AT89C51 single chip microcomputer with chip memory. The structure block diagram of single chip microcomputer control system is shown in Figure 2

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Figure 2 structure diagram of single chip microcomputer control system

1. Single chip microcomputer unit

the system uses AT89C51 single chip microcomputer as the control core, which is fully compatible with the instructions and functions of 8031 single chip microcomputer. At the same time, it also adds a built-in 4KB flash memory, with 128B internal RAM and 3 i/o ports. It has the advantages of low power consumption, small size, no need to expand the memory to meet the needs of the system, and can simplify the circuit

2. D/a converter

the single chip microcomputer outputs digital control signals after completing the voltage control processing, while the PWM (pulse width modulation) converter controlled by it needs analog signals. Therefore, d/a conversion must be carried out first. TLC5615, a widely used and low-cost 10 bit serial interface d/a converter, is selected for the system. TLC5615 is a digital to analog converter with serial interface launched by Texas Instruments in 1999. It has a 10 bit CMOS voltage output. The maximum output voltage is twice the reference voltage. The output voltage has the same polarity as the reference voltage, and is powered by a +5v single power supply. The three wire serial interface between TLC5615 and CPU conforms to the interface standard of industrial microprocessor, and the establishment time is 12.5 μ s. It has internal power on reset function, with low power consumption, and the maximum power consumption is only 1.75mw

3.a/d converter

a/d conversion circuit converts the voltage and current signals collected by the sampling circuit into digital signals and inputs them to the single chip microcomputer for processing. The system uses a low-power 8-channel serial 10 bit multi-channel a/d converter max192. Max192 has high conversion speed and is suitable for broadband systems. It is also powered by +5v power supply and can use external or internal clock for a/d conversion. Since the system samples and displays the output voltage and current in real time, there are two sampling input values

4. keyboard display circuit

the keyboard display circuit adopts the nixie tube driver and keyboard control chip CH451 with high cost performance and built-in high current drive. CH451 has built-in RC oscillation circuit, which can dynamically drive 8-bit nixie tubes. It has functions such as BCD decoding, flickering and shifting, and can scan 64 key keyboards at the same time. It can exchange information with single chip microcomputer through cascaded serial interface, and has monitoring functions such as power on reset and watchdog. CH451 can scan the display and identify keyboard keys instead of software methods, thus reducing the burden of CPU. The program design was simplified at the packaging day of DEMAG factory held in Ningbo on November 2

fourth, the design of high-voltage generation circuit

the low-voltage control signal output by the single-chip microcomputer generates the high-voltage output by the way of high-frequency switch boost through the switching power conversion circuit, and then obtains the required high-voltage DC output through rectification and filtering

1. high frequency booster

this system uses the row output transformer of the TV as the step-up transformer, and selects the pin as the input side and pin 4-hv as the output side. The boost ratio n is determined by the turns of the primary and secondary windings and the on time of the transistor,. N1 is the primary winding turns ratio n1=2300/21, which is the duty cycle of the switch tube

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2. Oscillation generation and driving circuit

high frequency oscillation circuit is a multivibrator circuit composed of a 555 timer plus resistance and capacitance, and the output is high-frequency rectangular pulse signal and high-frequency rectangular pulse signal

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