SU830630A1 - Digital device for control of pulse-width ac voltage regulator - Google Patents

Description

The invention relates to electrical engineering, in particular to regulating the voltage and power of electrical installations (resistance furnaces, induction installations) using counter-parallel connected thyristors.

A device for controlling a pulse-width regulator with a switching frequency of a higher frequency of the supply voltage [1].

The disadvantage of this device is the discrete nature of the regulation of the output voltage, so it is advisable to use a digital control device.

The closest in technical essence to the invention is a digital control device containing a clock pulse generator, which is a binary counter that counts the pulses received at its input from the output of the voltage zero sensor through a pulse shaper, voltage converter is a code that converts the control signal into a pulse sequence in additional code, a binary counter, the input of which receives pulses from the output of the voltage converter - the code and from the output of the second form I pulse output amplifier whose input is fed through a switch pulses you 'stroke binary counter and clock generator [2].

The disadvantage of this device is that when the voltage of the reference is equal to zero, the load U is not disconnected from the mains.

This leads to instability of regulation and inaccuracy in maintaining the adjustable parameter.

The purpose of the invention is to increase 5 accuracy at low levels of output voltage.

This goal is achieved by the fact that a well-known digital control device for a pulse-width regulator! 0 containing an output device, a clock pulse generator, a binary counter, a voltage zero sensor, two pulse shapers, a voltage converter 5 'code (PIK), a logic circuit is introduced consisting of two keys and a three-input circuit! coincidences. The first inputs of the keys are connected to the output of the clock generator, the second 0 inputs are connected to the output of the zero voltage sensor through a pulse shaper and to the output of the voltage-code converter. The outputs of the keys are connected to the inputs of the matching circuit, the third input of which is connected to the pulse generator, and the output is connected to the counting input of the binary counter.

In FIG. 1 shows a functional diagram of the proposed device with a digital system of pulse-width control; . FIG. 2 - timing diagrams.

The device contains a zero voltage sensor 1, pulse shapers 2 and 3, a 4 clock pulse generator, a PNK consisting of a key 5, a generator. 6 sawtooth voltage of a comparator 7, a matching circuit 8, a pulse generator 9, a trunk logic circuit consisting of 10 keys and 11 and three-input matching circuit 12, binary counter 13, key 14, output 15, source 16 of the reference voltage. Generator 4 clock pulses is a binary counter that recounts pulses of negative intersection (the moment the network voltage changes from the positive half-wave to negative) of the supply voltage, which are supplied from the voltage Gnu sensor through the shaper 2. The pulse from the generator 4 clock pulses goes to the keys 5.10, 11 and 14, as well as to the binary counter 13. The key 5 is opened and the sawtooth voltage generator 6 is operating. The keys 10 and 11 control the matching circuit 12, allowing the pulses of the pulse generator 9 to pass to the counting input of the binary counter 13. The key 14 controls the operation of the output amplifier 15.

Suppose that the control system must provide load connection for a time equal to three periods of the mains supply, and the entire regulation period contains 32 periods of mains voltage. The regulation period is set by the generator of 4 clock pulses. From the PNA to the binary counter 13 through the matching circuit 12, the number of pulses corresponding to the periods of the mains voltage, which must be passed to the load, is received. The conversion of the reference voltage and _e to the number of pulses at the output is carried out in direct code. A lower reference voltage Uj corresponds to a lower number of pulses at the output of the converter. These pulses arrive at the binary counter 13 during the time t ^ —t ₂ (see Fig. 2). The positive intersection pulses that come from the voltage zero sensor 1 through the shaper 3 (in this case 32-3 = 29), the binary counter 13 is brought to another full. After filling the binary counter 13, the pulse from its output opens the key 14 (moment t ₅ ), which allows the output device 15 to connect the load to the mains voltage. Upon the arrival of 32 pulses of the mains supply, the clock generator 4 generates a prohibition pulse (moment C), closing the key 14 and inhibiting the operation of the output device 15. The binary counter 13 is set to zero. The load is disconnected from the mains. The entire cycle of the controller starts over. The beginning of the operation of the output device 15 exactly corresponds to the moment when the voltage of the supply network passes through zero (the time of the transition from the negative half-wave to the positive), since the beginning of work is strictly connected with the arrival of the pulse of the binary counter 13 synchronized with the supply network. The end of the output device corresponds to the arrival of the last pulse of negative intersection, by which the generator 4 clock pulses generates a inhibit signal. When the reference voltage and _{3 is} close to zero (in Fig. 2, the level is indicated by a dashed line), the load voltage is zero. Indeed, at time t), the ramp voltage of the sawtooth voltage generator 6 is compared with the reference voltage Uj. From the output of the comparator 7, the signal is supplied to the coincidence circuit 8. At the moment of coincidence of the pulses of the pulse generator 9 and the comparator 7, a signal is generated at the output of the matching circuit 9 and supplied to the input of the key 10, which opens, and three signals (0; 1; 1) are received at the input of the matching circuit 12. Since the coincidence circuit is performed on a three-input AND-NOT element, the signal at the output of the coincidence circuit will not change, i.e. the pulses of the pulse generator 9 do not pass to the counting input of the binary counter 13, which reads only pulses of positive intersection, and the voltage at the load is zero.

Using a new node (logic circuit) improves the parameters of the controller, namely, it increases the accuracy of maintaining the adjustable parameter, increases the range of regulation, which expands the scope of the controller.

Claims (2)

zero voltage through the pulse shaper and to the output of the voltage converter is a code. The outputs of the keys are connected to the inputs of the coincidence circuit, the third input of which is connected to the pulse generator, and the output is connected to the counting input of the binary counter. FIG. 1 shows a functional diagram of the proposed device with a digital pulse-width control system; .on FIG. 2 time charts. The device contains a voltage sensor 1, a pulse voltage generator 2 and 3, a 4 clock pulse generator, a PNK consisting of a key 5, a generator. B of a sawtooth voltage of a comparator 7, a coincidence circuit 8, a pulse generator 9, a logic circuit SL, consisting of keys 10 and 11 and a three-input matching circuit 12,. binary counter 13, key 14, output 15, voltage supply source 16 The 4-clock pulse generator is a binary counter that recalculates the negative intersection pulses (the moment of the mains voltage transition from the positive half-wave to the negative) of the supply voltage that comes from sensor 1 zero voltage via globalizer 2. The pulse from the generator of clock pulses goes to the keys 5, 10, 11 and 14, as well as to the binary counter 13. Key 5 opens and runs the generator b of the sawtooth on the yarn. The keys 10 and 11 control the coincidence circuit 12, permitting the passage of pulses from the generator 9 pulses to the counting input of the binary counter 13. The key 14 controls the operation of the output amplifier 15. Suppose that the control system must connect the load to a time equal to three periods of the mains and the entire adjustment period contains 32 periods of mains voltage. The adjustment period is set by the 4 clock pulse generator. From the NCP, the number of impulses corresponding to the periods of the network voltage, which must be passed to the load, is fed into the binary counter 13 through the coincidence circuit 12. The conversion of the setting voltage from to the number of pulses at the output is carried out in the forward code. A lower voltage of the reference voltage corresponds to a smaller number of pulses at the output of the converter. These pulses enter the binary counter 13 over time (see FIG. 2). The positive-crossing pulses that come from the voltage zero sensor 1 through form factor 3 (in this case), the binary counter 13 is brought to full D9. After filling the binary counter 13, the 1-pulse from its output opens the key 14 (t-j) /, which enables the operation of the output device 15, which connects the load to the mains voltage. Upon the arrival of 32 pulses of the mains supply, the 4-clock pulse generates a inhibit pulse (time t), closing the key 14 and prohibiting the operation of the output device 15. The binary counter 13 is set to the zero state. The load is disconnected from the mains. The whole cycle of operation of the regulator starts over. The start of operation of the output device 15 corresponds exactly to the moment of transition of the mains voltage through zero (the moment of transition from the negative half-wave to the positive one), since the start of work is rigidly connected with the arrival of the pulse of the binary counter 13 synchronized with the mains. End of operation of the output device corresponds to the arrival of the last negative crossing pulse, with which the 4 clock pulse generator generates a inhibit signal. With a setting voltage of close to zero (in Fig. 2, the level is shown in dotted lines), the voltage across the load is zero. Indeed, at time t, the linearly rising voltage of the sawtooth generator 6 is compared with the driving voltage Uj. From the output of the comparator 7, the signal is fed to a coincidence circuit 8. At the time the pulses of the generator 9 of the pulses and the comparator 7 coincide, a signal is generated at the output of the circuit 9, which is applied to the input of the key 10, which opens, and three signals (0; 1; 1) are fed to the input of the coincidence circuit 12. Since the coincident NIN scheme is performed on the NAND three-input element, the signal at the output of the coincidence circuit does not change, i.e. the pulses of the pulse generator 9 do not pass to the counting input of the binary counter 13, which reads only the positive intersection pulses, and the voltage on the load is zero. The use of a new node (logic circuit) improves the parameters of the controller, namely, it increases the accuracy of maintenance of the adjustable parameter, increases the range of regulation, which expands the scope of application of the controller. DETAILED DESCRIPTION OF THE INVENTION Digital control device for a pulse width regulator of an alternating voltage containing a voltage zero sensor, two pulse shapers, the output of one of which is connected to the generator input clock pulse, and the output of the other to the input of a binary counter, high-frequency pulse generator voltage converter - the code, the output of which is connected to the input of the binary counter, output amplifier, to the input of which is connected via a switch the output of the clock pulse generator and the output of the binary counter, TL and. Of course, in order to increase accuracy at low levels of the output voltage, a logic circuit consisting of two keys, n, is connected between the output of the voltage converter. The code and the input of the binary counter. The left inputs of which are connected to the clock generator, and the second inputs to the output of the voltage converter are the code and to the output of the pulse driver, a three-input matching circuit, to the two inputs of which are connected the outputs of the logic circuit keys, and to the third input connected to the output of one high-frequency generator pulses. Information sources, taken into account during the examination 1. USSR author's certificate  471578, class, G 05 f 1/66, 1975. 2. M.I. Kolker. and others. Electric pulse width impedance control using thyristors. M., Energie, 1977, p. 85 - 89. but