Design of Model HSDC 14596 Series High Precision & Hi-Rel Hybrid Integrated resolver to digital converter

Abstract: This paper describes the development background and general technical scheme of Model HSDC 14596 Series resolver to digital converter developed by ECRIM. The key circuits design and chip domestic production solution for front-end signal processor, 64-sector function generator, bipolar VCO and phase self-adaptive circuit are mainly analyzed. It comprehensively describes reliability design technology to meet “Technical Requirements of Electronic Components Used in Space Specialized Project”, and also with process research results such as chip soldering, inner atmosphere control and Au-Al bonding.

Keywords: 16 bit resolution, sector function generator, bipolar VCO, phase self-adaptation

1.Resolver to digital converters Overview

The HSDC14596 series of high-precision, hi-rel resolver to digital converters are a class of high-precision, hi-rel, small-volume, low-power hybrid integrated electronics. The function of the device in the platform inertial navigation system is to convert the angle analog signal output by the synchronous machine or the resolver into a 16-bit parallel binary digital fish output, so that the computer can measure the physical parameters such as angle and displacement, and realizes the system, and reach the target. The block diagram of the device application system is shown in Figure

1:

Figure 1 Resolver to digital converter application block diagram

Resolver to digital converter is the key component of analog-to-digital conversion in the platform inertial servo system. Its technical indicators directly affect the system performance, especially the product with 16-bit resolution, 1.3-point conversion accuracy, and RIPCLK zero-signal output, BT Fault detection signal output, and a maximum 60° phase adaptive function. The domestic military units have always relied on imported DDC products, and the cycle and price are restricted.

This project has passed the HSDC14596 series of high-precision and hi-rel hybrid integrated shaft angle converter technology, and has broken through and mastered the key technologies such as function generator, voltage-controlled oscillator and phase self-adaptation. At the same time, the circuit adopts independent core chip design to realize the goal of localization of products. In addition, with the application of ECRIM chips soldering, internal atmosphere control, gold-aluminum bonding and other technological research results in the manufacturing process of this product, the quality grade of this kind of product has reached K1 level, which can meet the "aerospace special engineering electronic components." skills requirement".

2. Resolver to digital converters Overall plan

This project adopts the design principle of the performance tracking type shaft angle converter circuit as the overall design of the electric raft design, and has the ability to realize high speed and high precision digital automatic tracking ability for the input simulation fish. In theory, the converter has good static and dynamic track performance, good anti-jamming and environmental adaptability. The circuit block diagram is shown in Figure 2:

Figure 2 Block diagram of the HSD14596 series converter

3. Resolver to digital converters Key technologies

3.1 Resolver to digital converters Front-end signal processing circuit design

This part is composed of an electronic SCOTT converter or an isolation amplifier, which functions to isolate the input analog angle and convert it into two precision orthogonal signals Vs and Vc, and simultaneously convert the excitation signal into a phase-phase processing control signal. The front-end signal processing circuit must have a large common-mode rejection ratio to accommodate the input of AC signals such as 11.8V, 26V, and 115V. At the same time, to ensure the high precision of the converter, the coverage of the Vs and Vc signals must be strictly matched. The error caused by the mismatch must be less than 0.33. The design principles and methods are described as follows:

Synchronous machine signal: V（S3-S1）= Vsinθsinωt

V（S1-S2）= Vsin(θ-120°)sinωt

V（S2-S3）= Vsin(θ-240°)sinωt

(V=KVm; Vm is the synchronous machine reference voltage input, K is the synchronous machine reference input and signal output voltage ratio)

The circuit design is as follows:

When: V（S2-S3）= Vsin(θ-240°)sinωt

= V(sinθcos240°- cosθsin240°) sinωt

= V(-sinθcos60°+ cosθsin60°) sinωt

= V( cosθ- sinθ) sinωt

So: V（S2-S3）+ V（S3-S1）

= V（ cosθ- sinθ+ sinθ）sinωt

= V cosθsinωt

The design circuit is as follows:

Figure 3 Electronic SCOTT schematic

R1=R2=R3； R4=R5=R6； R7=（1+）R8； R9=R10

Available: VS= Vsinθsinωt

VC= Vcosθsinωt

For the resolver signal: V（S3-S1）= Vsinθsinωt

V（S2-S4）= Vcosθsinωt

The circuit is designed as a differential amplifier structure.

In order to ensure the conversion accuracy of the circuit, the resistor R1~R9 adopts ECRIM’s thin film resistor network process design, and the proportional accuracy of the resistor pair is required to be ≤0.01%. The actual use certificate fully meets the requirements of the indicator.

3.2 Resolver to digital converters 64-sector function generator circuit design

The sector function generator circuit is the key to ensure high-precision conversion of products. This project has designed a 64-sector function generator, and the linear approximation method is directly used in the sector. The method has high theoretical precision and the theoretical error is 5 seconds.

The key to this design is to form a 64-part boundary function. The design principles and methods are described below.

The basic expression of the sector function is:

(1) VK=VOsin（θ－K×11.25°）sin（ωt+α）

The following simplified expression is sin（θ－K×11.25°），其中K∈{0，31}

According to the trigonometric function relationship:

(2) sinA+sinB=2sin(A+B)/2 • cos(A-B)/2

Then the function generation method is as follows:

The sector function input signal is:

VS=Vosinθsin（ωt+α） (3)

VC=Vocosθsin（ωt+α） (4)

(Simplified expression is sinθ、cosθ)

sinθ is generated by the inverter,:

－sinθ，that is sin（θ－180°）= sin（θ－11.25°×16）

－cosθ，that is sin（θ－90°）= sin（θ－11.25°×8）

The adder is used to form a sector function, and the sector circuit is shown in FIG 4.

Figure 4 sector circuit

If A= sinθ, B= sin（θ－180°）, the input circuit makes R2 / R1=1/ cos 45°－1，R3=R4

Then the sin（θ－11.25°×4）can be obtained at the C terminal.

If A= sin（θ－45°），B= sin（θ－90°）, the input circuit makes R2 / R1=1/ cos 22.5°－1，R3=R4

Then the sin（θ－11.25°×6）can be obtained at the C terminal.

By analogy, a block diagram of the 32-layer function boundary-partitioning sector function circuit is formed by mutual cascading inside the sector function circuit.

Figure 5 block diagram of the block function

This part of the circuit consists of a precision resistor network, an analog switch array and several operational amplifiers.

The sector control logic circuit is performed with a corresponding angular code (binary number) of five digits as the analog switch array strobe logic required by the sector function circuit. The sector control logic circuit is composed of two four-choice analog switches, five two-select analog switches and one logic code control unit, and is designed as an analog switch array dedicated chip, as shown in FIG 6

Figure 6 analog switch array

3.3 Resolver to digital converters error formation circuit design

After the boundary function voltage is generated, it is multiplied by the original code and the complement of the digital angle in the sector, and then summed to form an error voltage Δ. The circuit can be designed as a dedicated chip for the R-2R 10 bit original complement multiplies DAC. Another circuit conversion can be realized with a general-purpose DAC.

Known previously: △V =［A2 sin（θ-A1-φ0）+ A2补sin（θ-A1）］

Let sin（θ-A1-φ0）=X；sin（θ-A1）=Y

Then △V = A2X+ A2补Y

= A2X+（1-A2）Y

=（X-Y）A2 +Y

Therefore, the design circuit can be obtained as shown in Figure 7:

Figure 7 error voltage forming circuit

The resistors used in the entire sector function generator and error-forming circuit are designed using a thin film resistor network process to ensure product conversion accuracy.

3.4 Resolver to digital converters Bipolar Voltage Controlled Oscillator Circuit Design

To meet the technical requirements of ±10V angular velocity VEL voltage output at ±2.5 rpm, a bipolar voltage controlled oscillator must be designed to meet the specifications.

The design of the voltage controlled oscillator is based on the principle of the charge flat street method, that is, the charge is equal to the discharge charge in the discharge time T1 in one oscillation cycle time. The discharge charge is generated by the internal constant current source Ii, and the discharge time T1 is generated by the monostable timing circuit, and the charging current is generated by the ratio of the input voltage V to the input resistance Ri. Let’s look at Figure 8:

Figure 8 integrator schematic

Because:

So the integrator oscillation frequency F=

It can be seen that when T1 and I1 are constant values, F is proportional to Vi.

The bipolar voltage controlled oscillator circuit is composed of a threshold voltage window comparator, a double one-stable circuit and a hysteresis comparator circuit. The voltage comparator generates a falling edge triggering one-shot circuit to generate a BUSY pulse and a LATCH pulse god; the one-shot circuit can receive an external auxiliary inhibit signal INHIBIT, prohibiting the generation of the LATCH pulse; the hysteresis comparator generates a logic level DIR, and the control 16 The count direction of the bit reversible counter. This circuit is designed as a dedicated chip for voltage controlled oscillators.

In order to ensure high linearity of the V/F conversion, the resistance and capacitance of the integrator require a small temperature drift.

3.5 Resolver to digital converters Broadband Phase Adaptive Circuit Design

The phase adaptive circuit is a key circuit to ensure the dynamic tracking accuracy of the product when there is a phase shift condition between the signal and the reference. Referring to foreign data, the design scheme of the circuit is: the reference signal generates a switching signal with the same phase, and the input signal itself generates a control pulse, controls the phase shift of the switching signal, and finally generates a phase-detecting signal that is in phase with the input signal.

Since the sine or cosine signals generated by the front-end SCOTT transformation have a small amplitude and cannot meet the input threshold voltage required for the comparator output reversal, the summing circuit of the sine and cosine signals should be designed to ensure the output amplitude. value.

Known previously: VS= Vsinθsinωt

VC= Vcosθsinωt

Available: VS+VC =V(sinθ+ cosθ)sinωt

= Vsin(θ + 45°) sinωt

Therefore, a larger signal amplitude at sinωt≠0 is obtained.

To design this circuit, the signals of the sine and cosine signals in the first quadrant must be summed by the high two bits of the output digital code based on the polarity of the sine and cosine signals.

In order to improve the working bandwidth of the phase adaptive circuit, it is necessary to design a reference signal 90° phase shifting circuit with a frequency range of 50~2600Hz. The output is sent to the input end of the D flip-flop, and the zero-pulse control is generated by the signal itself to generate the correct Phase switching signal. Here is Figure 9:

Figure 9 Broadband phase adaptive circuit block diagram

3.6 Resolver to digital converters fault self-diagnosis circuit design

This circuit is used to detect internal and external line faults in the converter product and to output a BIT signal (active low). If the externally-assisted synchronous machine signal line or the excitation signal line is broken, or a component in the internal circuit fails, the converter cannot track the change of the input analog angle normally.

The circuit is designed to take the amplified AC error, and after full-wave rectification and filtering, it is sent to the input end of the Schmitt inverter 54LS14, and the output is the required fault self-diagnosis prompt.

Therefore, a larger signal amplitude at sint0 is obtained.

The design of the circuit is:

When the converter is normally tracked within the accuracy range, its 1LSB AC error is:

△V=

When the effective value of Vs is 2V; the error gain is K=136; the mode is RA=10.2; when n=16

ΔV =136×2×10.2× =260mV

After full-wave rectification and filtering, the DC error of 1SB is: =234 mV

When the converter's abnormal tracking error reaches 60 LSBs, the DC error is 1.4V, that reaching the positive threshold voltage of the Schmitt inverter 54LS14, and causing its output level to be inverted. When the DC error is less than 0.9V, at the threshold voltage, the output returns to a high level, so that BIT is high when the power is normally tracked, and BIT is low when the tracking is not normal.

3.7 Resolver to digital converters Process Reliability Technology Research

According to the Technical Requirements for Electronic Components of Aerospace Special Projects, in order to achieve the K1 quality grade, the product technology of this project has achieved the following research results:

3.7.1 Resolver to digital converters Chip Welding Process Research

According to the requirements of the prohibition of the use of conductive adhesive bonding chips in the aerospace special project, the project carried out research on the corresponding chip soldering process, including vacuum welding process, eutectic soldering process and other technical research, instead of using the conductive adhesive bonding chip process.

3.7.2 Research on resolver to digital converters internal atmosphere control technology of products

According to the requirements of the aerospace special engineering electronic components standard, the internal atmosphere control of the hybrid integrated circuit product is stricter than the H-level requirement. Not only the water vapor content requirement is further improved, but also the content of oxygen, hydrogen, carbon dioxide, carbon-based organic residues and other gases is specified. The project carried out related research on the formation mechanism and process control of harmful atmospheres, and effectively solved the problem of internal atmosphere control.

3.7.3 Study on resolver to digital converters gold-aluminum bonding process

According to the standard requirements of aerospace special engineering electronic components, the project carried out research on gold-aluminum bonding technology, passed the assessment requirements of 300 °C, 24h and long life. After the bottom test, the current bonding condition satisfies this requirement.

4 Conclusion

The HSDC14596 series of high-precision and hi-rel hybrid resolver to digital converters developed by this project are designed and manufactured by independent chip technology. The products have reached the technical indexes of similar products of DDC Company of the United States and achieved localization, and PIN-T0-PIN is compatible; It has the functions of INHIBIT output static, ENABLE output enable, RIFCLK zero signal output, BIT fault detection signal output, and the function of adaptive phase shift angle between signal and reference of maximum 60°; the product quality reaches the general specification of hybrid integrated circuits with GB2438-2002 assessment requirements, and meet the "aerospace special engineering electronic components technical requirements."

References:

(1) Data Converter Reference Manual I[M]. Data Devices Corporation, 1999

(2) Synchro/Resolver Conversion Handbook [M]. Data Devices Corporation 2009,

(3) Variable Resolution Resolver-to-Digtial Converter AD2S83 data manual[M]. Analog Devices, Inc, 2000

(4) Boyes G S, ed Synchro and resolver conversion [Z] Norwood, MA: Anolog Devices, 1980.

(5) Principle of automatic control, Yu Chengbo, Zhang Lian, et al., Beijing: Tsinghua University Press, 2006

(6) Operational Amplifier Application Technical Manual, 2009wtmg, etc., Zhang Lefeng, Zhang Ding, etc. Beijing: People's Posts and Telecommunications Press, 2009.1

(7) "Signal and System Theory, Methods and Applications" Xu Shoushi