SU760409A1 - Pulse generator - Google Patents

Description

The invention relates to a pulse technique ..

Pulse generators are known, consisting of a controlled trigger and a control voltage divider, 5 of which uses a thermo-dependent element of indirect heating £] as the timing element.

The disadvantage of such generators is the low stability of the oscillation period.

Most closely related to the invention is a pulse generator containing a controlled bistable element with a load, and a control voltage divider with 15 thermo-dependent; time assigning elements. tom £ 2].

To increase the stability of the oscillation period in such a generator, it is necessary to choose the temperature of thermodependent elements significantly higher than the temperature of the medium and apply a trigger with little temperature dependent parameters. > 25

The purpose of the invention is to increase the amount of.

bilnosti period oscillations. With this

purpose introduced housing and heater

thermally connected housings

generator elements, and

2

The case heater is included in the load circuit of the same generator.

In addition, an additional thermo-dependent element was used as a case heater.

The functional diagram of the pulse generator is shown in FIG. one; in fig. 2 shows the design of the housing heater in the form of a thermo-dependent element.

The pulse generator consists of a controlled bistable element, for example, trigger 1, and a control voltage divider, which includes a resistor 2 and a time-dependent thermodependent element 3, the junction point of which is connected to the trigger input 1. Thermo-dependent element heater 3 and housing heater 4 are turned on . . ·

The pulse generator works as follows.

In the half-period of oscillations, when the left half of the trigger 1 is open, the thermo-dependent element 3, having a negative temperature coefficient, is heated from the preheater, resulting in a voltage at the trigger input (or current at up760409

trip'er current) decreases in absolute value. At a certain value of this voltage, corresponding to the threshold, the trigger goes into a state in which its left half is closed. The cooling of the thermo-dependent element 3 begins and the absolute value of the voltage at the trigger input increases to a value equal to the stalling voltage, after which the trigger returns to its original state. Then the process is repeated.

When the generator is in operation, during the intervals when the left half of the trigger is open, the heater heats the 4th case and the elements enclosed in It, which are insulated from the external environment.

The thermal time constant of the housing with the generator elements is substantially longer than the thermo-dependent element 3 and longer than the duration of the generated pulses, therefore the temperature variations of the housing and the elements in it during the operation of the generator are small.

When the medium temperature changes, for example, it increases, the duration of the half-period of oscillations corresponding to the heating of the thermo-dependent element decreases, and the duration of the half-period corresponding to its cooling increases. In this case, the duty cycle of current pulses entering the case heater increases, which leads to a decrease in the average temperature of the case and the impulse generator elements contained in it.

With a decrease in the temperature of the medium, the duration of the i-period, corresponding to the heating of the thermo-dependent element, increases and the heating of the casing and elements of the pulse generator increases, i.e. the temperature of the elements of the generator is automatically changed when the temperature of the medium changes in such a way that the effect of this change on the oscillation period is significantly reduced. .

When the temperature of the medium changes by the value of ДТ _{0, the} temperature of the case gets an increment of ДТ ₆ ', which is η times. less

ten

15

20

25

thirty

35

40

45

ato

I „." * 1

η

50

where ΔΤ _Κ is the temperature rise

enclosures above ambient temperature 55;

P and respectively power

heating and thermal resistance of a thermo-dependent time-dependent element;

K - coefficient proportional to 60

¹ of its value

depends on the mode of the generator and is defined 2 <k, <3.

within inequality

Due to the nonlinear dependence of the oscillation period on the DT _{P, the} instability of the oscillation period decreases several times more than η. Elements of the generator, the parameters of which are small. Depending on the temperature of the RT, such as resistors, can be located outside the case.

In addition, a thermo-dependent element can be used as a body heater (Fig. 2). In this case, the pulse generator contains a controlled bistable element 5 and a control circuit in the form of a voltage divider that includes c. the resistor 6 itself and the time-dependent thermo-dependent element 7. The output of the control circuit is connected to the input of the controlled bistable element 5. The load circuit of the element 5 includes a heater 8 of the time-generating element 7 and a thermo-dependent element 9, which is a body heater with which the pulse generator elements have thermal coupling. A pulse generator operates similarly to that considered, but with increasing temperature, the environment decreases the heating of the housing both by increasing the duty cycle of the pulses and by increasing the resistance of the preheater 9, which has a positive temperature coefficient of resistance. In the expression above for ΔΤθ, this feature is taken into account by increasing the coefficient k ,, which leads to a decrease in ΔΤ ₀

The inclusion in the load circuit of an additional thermo-dependent element located in the common case with other elements of the generator significantly increases the stability of the oscillation period without increasing the operating temperatures of the constituent elements, expanding the functionality of the device.

Claims (2)

Claim 1. A pulse generator containing a controlled bistable element with a load and a control voltage divider with a thermo-dependent timing element, characterized in that, in order to increase the stability of the oscillation period, the housing and the heater of the housing having a thermal connection with the generator elements are introduced, load circuit of this same generator. 2. The generator in π. 1, that is due to the fact that an additional thermo-dependent element was used as a body heater. Priority points: 01.02.72 on π. one, 10/30/74 under item 2. 65 760409