SU761190A1 - Method and apparatus for stabilizing voltage on the electrodes of contact welding machine - Google Patents

Description

The invention relates to resistance welding and can be used as a source of welding pulses in installations for sealing the housings of semiconductor devices, as well as in microslide.

There is a method of stabilizing the voltage on the electrodes of a contact welding machine by comparing the output voltage value with the reference 'and then using the error signal to control the stabilization process [1].

The disadvantage of this method is the impossibility of the implementation of the stabilization of the voltage on the electrodes directly in each welding pulse.

A device that implements a known method comprising an inverter made on a push-pull amplifier with a transformer, a master frequency generator of welding pulses, a constant current source, a frequency divider, a regulator of duty ratio of the number of pulses and pauses, a constant reference voltage node, a reference node and connected to the output of the reference node is known. control unit {1].

However, in the known device, the large inertia of the stabilization system, due to the presence of a KS filter in reverse2

connection, it is not possible to stabilize the welding process directly in each welding pulse.

The aim of the invention is to improve the quality of stabilization 5.

This goal is achieved by comparing the output voltage with the reference voltage, its fronts that do not correspond to the nominal value of 10 pulses cut and fill the gaps between the pulses, as well as the times of the front and rear edges cut with a reference voltage whose amplitude is equal to the nominal value of the output voltage. A rectifier, a voltage mixer, a shaping unit with cutting the edges of pulses that do not correspond to the nominal voltage, and a pulse reference voltage switch-on node are inserted into the device that implements the proposed method, while the rectifier and the voltage mixer are connected in series between the inverter output and one of the inputs of the comparison node , and 25 serially connected nodes for forming and switching on the reference voltage are connected between the second input of the mixer and the output of the master oscillator.

The proposed method allows you to get 30 speed stabilization and regulation

under the influence of disturbing factors up to 0.5 ms.

FIG. 1 shows time diagrams explaining the proposed method; in fig. 2 is a functional diagram of the device that implements the method.

The stabilized output pulses (Fig. 1, a) are rectified (Fig. D, b), mixed with the pulses of the reference voltage (Fig. 1, c). When this occurs, the combination in time of the stabilized rectified pulses with the pulses of the reference voltage.

The cutting of the fronts of the pulses is carried out before the supply of the pulses of the reference voltage in order to combine them with the stabilized pulses. As a result of such a combination of pulses of the reference voltage and stabilized rectified pulses, a continuous control signal is generated, which allows further stabilization of the voltage of the output pulses by the usual compensation method.

A device that implements the proposed method consists of an inverter 1, containing a master oscillator 2, a push-pull amplifier 3, a welding transformer 4; frequency divider 5; the controller 6 of the duty cycle of the number of pulses and pauses; diodes 7 and 8; resistance 9; capacitor 10; a voltage stabilization unit 11 on electrodes consisting of a rectifier 12, a voltage mixer 13, a comparison unit 14, a regulating unit 15, a constant reference voltage node 16, a pulse reference voltage driver 17, a pulse reference voltage switching node 18.

The device works as follows.

During operation, a change in the voltage of the network or a change in the resistance of the load leads to a change in the voltage of the output pulses taken from the output winding of the welding transformer 4 and having different polarities (Fig. 1, a). Then these pulses are rectified by a rectifier and have a discrete level rather than a solid one (Fig. 1.6). The intervals between pulses are determined by the delay time to eliminate the through currents in inverter 1. From the output of the rectifier 12, unipolar pulses go to one of the inputs of a voltage mixer 13, to another input of which pulses are sent from the driver 17 of the pulsed reference voltage to the intervals between the output pulses of the inverter 1. This supply of a continuous, rather than a discrete, voltage level to the comparison unit 14 is achieved, which is then compared with a constant stabilized voltage level outputted by the 16th node common reference voltage.

The device requires the formation of

two reference voltages, one of which is constant and goes directly to the comparison node 14, and the other - the reference pulse voltage supplied to the intervals between the pulses generated by the inverter at one of the inputs of the voltage mixer 13, thereby maintaining the nominal supply voltage on the transistor collectors the inverter amplifier 1 at the time specified intervals. FIG. 1, e shows the process of mixing the voltages from the output of the rectifier 12 and the reference pulses from the block.

In the process of the formation of output pulses by the inverter 1, pulses with varying amplitude voltage are input from the output of the voltage mixer 13, depending on changes in the load resistance, as well as on the network voltage. This change in voltage can be observed both in single pulses and in a series of pulses. These pulses from the output of the voltage mixer 13 are fed to the comparison node 14, where they are compared with a constant level of the reference voltage generated by the node 16 of the constant reference voltage. The error voltage generated by the comparison unit 14, affects the control unit 15, resulting in the amplitude of the voltage of the output pulses to the nominal value during each welding pulse generated by the inverter 1.

Improving the stability of the formation of "packs" of high-frequency welding pulses is achieved by introducing between the output of the master oscillator 2 and one of the inputs of the push-pull amplifier 3 of the frequency divider 5 and the controller 6 of the duty ratio of the number of pulses and pauses.

The introduction of these elements and their connection in this way allows you to achieve a synchronous start of the regulator 6 of the duty cycle from the frequency of the master oscillator 2 and to obtain strictly fixed “bundles” of high-frequency pulses, which increases the stability of the welding mode.

The chain, consisting of diodes 7 and 8 and parallel-connected resistances 9 and capacitor 10, makes it possible to obtain smooth increases in the amplitude of high-frequency pulses and eliminate the spikes that occur when the inverter is switched. A smooth increase in the welding pulse improves the quality of the formation of the welded point, and the elimination of emissions protects the power transistors of the inverter 1 from voltage breakdown.

The advantage of the proposed method and device for its implementation is a significant reduction in inertia and the ability to stabilize the amplitude of the pulses at the output of the inverter directly in the process of forming these parameters.

five

pulses. The inertia of the device is determined only by minor phase shifts of the circuit elements and is 0.5 ms. The stability of the output voltage of the device is ± 1%, which implements the proposed method.

Claims (3)

Claim 1. The method of voltage stabilization on the electrodes of the contact welding machine by comparing the output voltage value with the reference and subsequent use of the error signal to control the stabilization process, characterized in that, in order to improve the quality of stabilization, before comparison with the reference output voltage is rectified, its fronts are inappropriate the nominal value of the pulse, cut and fill the gaps between the pulses, as well as the times of the front and rear edges cut out with the reference voltage iem whose amplitude is equal to the nominal value of the output voltage. 2. A device for implementing the method of π. 1, containing an inverter, made 6 on a push-pull amplifier with a transformer, a driving frequency generator for welding pulses, a DC source, a frequency divider, a duty cycle controller 5 number of pulses, and pauses, constant reference voltage node, reference node and a regulating unit connected to the output of the comparison node, characterized in that a rectifier, a mixer, a shaping unit with cutting out the edges of impulses that do not correspond to the nominal voltage, and a pulse switching node are entered into it reference voltage, with the rectifier and voltage mixer 5 are connected in series between the output of the inverter and one of the inputs of the comparison node, and the series-connected nodes for forming and switching on the reference voltage are connected between the second input 0 mixer and output master oscillator.