The Programmable Mixed Signal Company

Transcription

1 The Programmable Mixed Signal Company 1

2 Table of Contents 1. Introduction 2. Digitally Controlled Potentiometer 3. Advantages of XDCP Calibration of Power Supply 4. Front End 5. Power Mesh 6. Secondary Control 7. Primary Control 8. Performance Data 9. XDCP Converter Frequency Control 10. XDCP Output Voltage Control 11. XDCP Output Overcurrent Control 12. A Simple XDCP Programmer 13. Other XDCP Power Supply Applications 2

3 INTRODUCTION This seminar introduces the power supply designer to a powerful control device. The XICOR integrated circuit, the Digitally Controlled Potentiometer (XDCP ), offers new options in power supply design. Mechanical potentiometers are typically avoided by the power supply designer because of: 1. Significant reliability problems, 2. Undesirable wiper movements due to normal handling during shipping, 3. The requirement for manual adjustment during calibration and test. The Xicor XDCP overcomes these problems and offers additional options. The Xicor XDCP can be used for: 1. Electronic set and forget calibration, manually or under automatic test equipment control, 2. High reliability associated with IC silicon technology, 3. Immunity from wiper movement due to mechanical stresses, 4. Power supply customer interface to potentiometer via electronic means. 3 To demonstrate potential Xicor XDCP applications, a switching power supply incorporating three XDCPs was designed, built, and tested. The power supply is an AC input and 12V@10A DC output. Xicor XDCPs are used to calibrate the output voltage, converter frequency, and overcurrent trip set points.

4 Digitally-Controlled Potentiometer block diagram, 3 wire interface 4

5 Advantages of XDCP Calibration of Power Supply: 5 1.Output Voltage Improves initial output voltage accuracy by 30:1 2.Converter Frequency Reduces worst case steady state stresses on magnetic components Stabilizes low frequency EMI performance (allows for smaller EMI filter inductor) 3.Overcurrent Threshold Improves initial accuracy from a typical + 30% to + 3% Substantially reduces worst case overload stress on magnetic components and power silicon devices 4.Plus the additional advantages of: Eliminates mechanical potentiometers Automates calibration during test Allows computer control of power supply parameters

6 Front End 6 All capacitor values in microfarads All resistor values in ohms All inductor values in microhenries

7 Power Mesh 7

8 Secondary Control 8

9 Primary Control 9

10 Performance Data 10 Parameter Conditions Test Data Load Regulation: 0.5A to 10A (0.5A is minimum load), 120Vac 25mV (?Vo) Line Regulation: 100Vac-132Vac, 60Hz, 10A load 2mV (?Vo) Input Power: 10A load, 120Vac, 60Hz input 139W Efficiency: 10A load, 120Vac, 60Hz input 86% Output Voltage: 10A load, 120Vac, 60Hz input Vdc XDCP Programmable Output Voltage Range: Vdc to Vdc Converter Frequency: 109.6kHz XDCP Programmable Converter Frequency Range: to122.9khz 101.7kHz Onset of Overcurrent Protection: 120Vac, 60Hz input 10.67A XDCP Programmable Overcurrent Protection Onset: 8.09A to 13.85A Output Ripple & Noise: 10A load, 120Vac, 60Hz input, 20mHz Bandwidth <100mV P-P

11 XDCP Converter Frequency Control 11

12 XDCP Output Voltage Control Output Voltage nominal when XICOR XDCP at mid point tap Output Voltage maximum when XICOR XDCP at lowest tap Output Voltage minimum when XICOR XDCP at highest tap 12

13 XDCP Output Overcurrent Control 13

14 Other XDCP Power Supply Applications Automatic calibration in production, programmable via bed-of-nails interface (same time as parametric testing) User interface to control output voltage/current (e.g. margin testing) Long life reliable alternative for adjustment of potentiometers in laboratory power supplies Trim out feedback optocoupler gain tolerance (often >2:1) to optimize closed loop performanceany application requiring electronic control of a potentiometer setting or adjustment. This is simply not practical with a mechanical potentiometer 14