CS229573B1 - Connection of RC amplitude stabilization circuit - Google Patents

Abstract

The connection is suitable for stabilizing the amplitude of RC generators intended for calibration purposes. The amplitude control loop has two branches. The slow branch ensures accuracy and long-term stability of the amplitude of the RC generator oscillations, the fast branch ensures rapid stabilization, limiting voltage overshoots during a step change in frequency while maintaining a low value of nonlinear distortion.

Description

BACKGROUND OF THE INVENTION The present invention relates to a circuit of an amplitude stabilization circuit of an RC generator with frequency limiting overshoot.

Connections of RC generators consist of electronic amplifiers and feedback systems that determine the frequency and stabilize the amplitude of the generated harmonic oscillations. The amplitude control circuit is solved in several different ways. Amplitude stabilization by non-linearity is poorly effective and causes large non-linear distortion. The use of such elements as thermistors and bulbs results in temperature dependence, weaker stabilizing effect and frequency dependence of properties.

Frequency control amplitude feedback circuits, consisting of an effective, medium or peak voltage rectifier, a DC reference, a deviation amplifier and an actuator, such as an analog multiplier or a controlled resistor realized by a dynamic diode resistance, a FET, a photo resistor, and the like are often used. In order to obtain accurate amplitude and small non-linear distortion of the generator, it is necessary to filter the waveform after rectification as best as possible, the loop being inertial. The requirement for high amplitude accuracy of the generated signal leads to the need for large amplification in the amplitude control branch, achieving a small non-linear distortion requires a large filter time constant.

These requirements can be met only partially, at the cost of a compromise. For stability reasons, the amplitude stabilization control loop needs to be solved as proportionally integrating, but the proportional branch increases the non-linear distortion by transferring the components of the spectrum generated in the rectifier to the generator control amplitude member. Especially disadvantageously, the properties of the amplitude control loop are manifested when the generator frequency is switched, where the amplitude may become fixed with amplitude overshooting or even damped oscillations. Amplitude overshoot is strongly undesirable especially when calibrating AC voltage metrology, where a sudden increase in amplitude can be dangerous for connected sensitive metrology equipment.

These prior disadvantages are overcome by the wiring of the amplitude stabilization circuit of the RC generator according to the invention.

It is an object of the invention that the non-inverting input of the sump is connected to a common point of the first and second resistors, the second resistor being connected to the first output of the DC reference by the second resistor, the second resistor being connected via the diode to the output terminal. with a common conductor.

The main advantage of this new circuit is high output voltage stability, better than 5. 10-5, at a low non-linear distortion value of better than 3.10 ^{4 4} , achieved at short settling times even at low frequencies, for example 10 Hz, due to the influence of a peak rectifier in place of the proportional amplitude control branch. Another advantage is the limitation of the amplitude of the output voltage amplitude during a step frequency change due to the fast acting amplitude control branch through the peak rectifier.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is illustrated in greater detail in the accompanying drawing, in which there is a block diagram of an RC amplitude stabilization circuit.

The output terminal 7 of the RC 1 generator is connected via a precision rectifier 2 and the integrator 3 to a summary 4, the output of which is connected to the amplitude control input 8 of the generator RC 1. The non-inverting input of the generator 4 is connected to a common point the second resistor terminal 11 is connected to a first output of the DC reference circuit 6, the second output of which is connected to an integrator 3. The second terminal of the first resistor 10 is connected via diode 9 to the output terminal 7 of the RC 1 generator. .

The amplitude control loop has two branches. The output voltage from the output terminal 7 is measured by a precision rectifier 2 and compared to the voltage from the other output of the DC reference 6 in the integrator 3. This provides a slow control branch ensuring accuracy and long-term stability of the RC 1 amplitude. a rectifier 5 with a diode 9, a capacitor 12 and a comparator circuit formed by the first and second resistors 10, 11. The rectified voltage is compared to the reference voltage by the first and second resistors 10 and 11 and the resulting signal is applied to the non-inverting terminal of the summator 4. The peak rectifier 5 reacts quickly to the voltage increase at the output terminal 7, while giving a control signal with less ripple than using a conventional proportional feedback branch.

The circuit according to the invention is particularly suitable for stabilizing the amplitude of RC generators intended for calibration purposes.

Claims (1)

SUBJECT Circuit of the generator amplitude stabilization circuit consisting of a precision rectifier, integrator, summer, peak rectifier and a DC reference circuit, characterized in that the non-inverting summer input (4) is connected to a common point of the first and second resistors (10, 11), the second resistor (11) is connected by its second terminal to the first output of the DC reference circuit (6), while the second terminal of the first resistor (10) is connected via diode (9) to the output terminal (7) and via capacitor (12) with common conductor (13).