KR0145876B1 - Exchange system ring signal circuit - Google Patents

Abstract

[Technical field to which the invention described in the claims belong]

A ring signal generating circuit is provided in an exchange system.

[Technical Challenges to Invent]

The present invention provides a ring signal generation circuit that can reduce the size of an exchange system by miniaturizing a transformer and simplifying circuit configuration and control.

[Summary of the solution of the invention]

A circuit for generating a ring signal using detachment of a relay, the circuit comprising: a DC-DC conversion means using pulse width modulation and a predetermined control signal for controlling pulse width modulation switching in the DC-DC conversion means; Control signal generating means, phase switching means for converting a phase of a signal output from the DC-DC conversion means in a predetermined period in response to a pulse generated from the control signal generating means to output a sine wave, and generation of the ring signal And zero cross detection means for generating a zero cross detection signal in order to set the time point as a time point at which the sine wave output from the phase shifting means reaches a zero potential.

[Important Uses of the Invention]

In the implementation of the ring signal generation circuit, it is used to reduce the size of the exchange system in which the ring signal generation circuit is mounted by miniaturizing the transformer and simplifying the configuration and control of the circuit.

Description

Ring signal generation circuit of exchange system

1 is a block diagram of a pulse width modulation DC / AC conversion circuit according to the present invention

2 is a detailed circuit diagram of an embodiment of a control signal generator using a single power supply;

Figure 3a is a waveform diagram of the signals generated from the control signal generator when using a positive power supply

3b is a waveform diagram of signals generated from the control signal generator when using a single power supply;

4 is a detailed circuit diagram of a portion of the control and feedback related circuit in FIG.

5 is an operational waveform diagram according to the present invention

6 is an operating waveform diagram of the voltage V _CD applied between the node points CD and the comparison signal 21 in FIG.

7 is a configuration diagram of an embodiment of a dummy rod of the filter and the dummy rod part among the first diagrams.

8 is a configuration diagram of another embodiment of the dummy rod of the filter and the dummy rod part of the first diagram

FIG. 9 is a view illustrating a part of an operating waveform associated with a dummy rod of a filter and a dummy rod part of FIG. 1.

FIG. 10 is an overall operation waveform diagram relating to the dummy rod of the filter and the dummy rod part of the first diagram

FIG. 11A is a view showing an embodiment of an AC switch in FIG.

FIG. 11B is an equivalent circuit diagram when a low level control signal is input to the AC switch of FIG. 11A.

FIG. 11C is an equivalent circuit diagram when a high level control signal is input to the AC switch of FIG. 11A.

12 is an operating waveform diagram according to zero cross detection.

* Explanation of symbols for main parts of the drawings

100: DC-DC power supply device 20: control signal generator

4: Transformer 5: Sine Wave Generator

6: Full wave rectifier 7: Pulse generator

8: PWM conversion switch 9, 10, 18: photocoupler

11: filter and dummy rod 14: AC switch

16: Feedback part 17: SCR

3: Current sensor 34: Level shifter

D1, D3, D11: Diode R6: Variable resistance

Q11: N-MOS transistor OP1-OP4: Operational amplifier

D2: Zener Diode

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ring signal generation circuit in an exchange system, and in particular, converts a direct current (DC) input power source into a low frequency sinusoidal AC power source using pulse width modulation (PWM) and generates a ring signal. The present invention relates to a circuit that realizes miniaturization of an exchange system.

When implementing a key phone system, the distance between each board is usually about 25 millimeters, but it is falling to 16 millimeters and the gap is gradually narrowing. Reducing the gap is directly related to the size of the key phone, and the miniaturization of electronic products and the simplification of configuration are acting as important as the quality of the product for consumers. The ring signal generation circuit is no exception in reducing the distance between the multiple boards implementing the key phone system.

In general, there are three ways to generate ring signal. One method is DC-AC conversion on the primary side and amplitude amplification using linear transformer. An example of this can be found in “Linear Applications Handbook Volume II”, 1993, AN35-14 and Patent Application No. 94-23106, 'Sine-wave Ring Generation Circuit', filed earlier by the applicant.

The other method is to make the maximum voltage required by AC using DC-DC converter and turn on / off four switches by PWM control to make pulse wave with variable duty and LC filter it. This example is a patent application No. 91-8340, filed by the applicant of the present application, 'ring generator using a PWM inverter' and utility model registration application number previously filed by the Korea Electronics and Telecommunications Research Institute and the Korea Telecommunications Corporation 93-3747, Digital Pulse Width Modulated DC / AC Voltage Converters for Switcher Call Signals.

Another method is to make AC by making a (±) maximum voltage with a DC-DC converter and then linearly changing the transistor as in the second method. Looking at these three methods, the first method has the simplest configuration, but has the disadvantage of high loss in DC-AC conversion and large linear transformer in inverse proportion to AC frequency.

The second method has the advantage that the size is reduced by using a switching transformer without using a linear transformer. However, since the four switches are turned on and off while the voltage is raised to the maximum voltage, a separate control to reduce such switching loss is achieved. Is needed. Therefore, the circuit becomes complicated. In addition, since the low pass filter enters the output stage, the size can be increased.

The third method is to avoid using a linear transformer, but the loss caused by the transistor is increased because a sine wave must be generated using only the transistor while being amplified to a (±) maximum voltage. Therefore, the heat dissipation problem should be considered according to the capacity.

US Patent No. 5,159,539, HIGH FREQUENCY DC / AC POWER CONVERTING APPARATUS, and US 5,189,603 DC TO AC ELECTRIC POWER CONVERTING APPARATUS, are described above. A method using the second method is disclosed. In other words, by using four switches on both the primary and secondary sides of the transformer, the primary side serves as an inverter and the secondary side performs a role of a cyclo converter. According to this method, although the size of the transformer is reduced by the high speed switching operation, there is a problem in that the circuits for controlling the switches on the primary and secondary sides are complicated.

Accordingly, an object of the present invention is to provide a ring signal generation circuit which can reduce the size of the keyphone system through the miniaturization of the transformer, and the configuration and control of the circuit.

The present invention for achieving the above object is a circuit for generating a ring signal by using the detachment of the relay, the DC-DC conversion means using pulse width modulation, and the pulse width modulation switching in the DC-DC conversion means Control signal generating means for outputting a predetermined control signal for controlling, and in response to a pulse generated from the control signal generating means to switch the phase of the signal output from the DC-DC conversion means to a predetermined period to output a sine wave And a phase crossing means and a zero cross detection means for generating a zero cross detection signal in order to set the time point at which the ring signal is generated to the point at which the sine wave output from the phase change means reaches zero potential.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

First, in adding reference numerals to the components of each drawing, it should be noted that the same reference numerals have the same reference numerals as much as possible even if displayed on different drawings. In addition, in the following description, many specific details such as components of specific circuits are shown, which are provided to help a more general understanding of the present invention, and the present invention may be practiced without these specific details. It will be obvious to those skilled in the art. In the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

1 is a block diagram of a pulse width modulated DC / AC conversion circuit according to the present invention.

First, the method according to the input and output relationship of the PWM converter, there are a number of RCC, forward, flyback and half-bridge scheme, etc. The bag method is shown as an example.

In FIG. 1, the DC-DC power supply device 100 is a known power supply device. The DC-DC power supply device 100 includes a filter 1, a switch 2, a current sensor 3, a transformer 4, a PWM conversion switching unit 8, a filter and a dummy load unit 11, and a feedback unit 16.

A predetermined comparison signal 21 is applied to the ERROR AMP. Terminal of the PWM conversion switching unit 8 so that the output voltage varies according to the level of the comparison signal 21. In this case, the comparison signal 21 is a full-wave rectified sine wave output from the sine wave generator 5 of the control signal generator 20.

The photocoupler 10 and the AC switch 14 are phase switching circuits. In response to a predetermined control signal 24, the phase of the full wave rectified waveform output from the filter and the dummy rod part 11 is changed at a predetermined period so that the sine wave is output. In this case, the control signal 24 is a signal generated by the pulse generator 7 using the sine wave output from the sine wave generator 5 of the control signal generator 20 described above.

The portions composed of the SCR 17, the photocoupler 18, the signal conversion unit 19 or the feedback unit 16, and the signal conversion unit 19 are different paths for zero cross detection, respectively. Signal 25 generated through this path is transmitted to the key controller of the keyphone or exchange.

For reference, current sensor 3 is used to set a variable pulse width reference. In addition, although not shown, a voltage sensor for maintaining the output at a constant voltage may be connected to an output terminal of the filter and the dummy load unit 11, and this sensor is also used to hold a variable pulse width reference, and whether an overcurrent or a load is shorted. You can also connect a current sensor that detects and performs a blocking function.

On the other hand, the signals generated by the control signal generator 20 in FIG. 1 are half-sine waves and pulse waves, and there are various methods of generating the signals. Generally used can be divided into when using a positive power supply and when using a single power supply, and when using a positive power supply is composed of a sine wave generator, a full-wave rectifier and a pulse generator.

2 is a specific circuit diagram of an embodiment of the control signal generator 20 using a single power supply, and is composed of a sine wave generator 5, a full wave rectifier 6, a pulse generator 7 and a level shifter 34. As shown in FIG.

3A and 3B illustrate signals generated by the control signal generator 20 when using both power sources and short power sources, respectively. The 3b or 3f waveform is input to the control terminal of the PWM conversion switch 8 so that the output waveforms of the filter and dummy load 11 of FIG. 1 become amplified reflection waves, and 3c or 3g converts the amplified anti-sine waves into sine waves. The main acts as a control signal.

Referring again to FIG. 3, a sine wave generator 5 using a known win bridge oscillator circuit consists of an operational amplifier OP1, a variable resistor R6, a plurality of resistors R1 to R5, and capacitors C1 to C3. Since a single power source is used, a predetermined reference potential Vref is applied instead of the ground (GND) level used as the reference power source when using both power sources. Capacitor C2 is added for some degree of phase correction, and variable resistor R6 is one of means for adjusting the oscillation width of the win bridge. The sine wave output from the sine wave generator 5 having such a configuration shows a waveform as shown in 3d of FIG. 3 and is supplied to the full wave rectifier 6 and the pulse generator 7.

The full-wave rectifier 6 is composed of operational amplifier OP2, resistors R7, R8 and diode D1. A level shifter 34 is connected to an output terminal of the full-wave rectifier 6, and the level shifter 34 includes an operational amplifier OP3, a zener diode D2, and a diode D3.

Since the reference voltage Vref is applied to the operational amplifier OP2, the sine wave is raised by Vref at ground as shown in 3e of FIG. 3. This signal is applied to the (+) input terminal of the operational amplifier OP3 of the level shifter 34 to remove the Vref overlap as shown in 3f of FIG. 3 to obtain the anti-sine wave of the ground level.

The pulse generator 7 is implemented with a comparator COMP1. As a result of comparing the 3d waveform of FIG. 3 sent to the non-inverting terminal of the comparator COMP1 with the reference voltage Vref provided to the inverting terminal, a square wave equal to 3g of FIG. 3 is obtained.

FIG. 4 specifically illustrates a portion of circuitry related to control and feedback in FIG. When the phototransistor of photocoupler 9 becomes conductive, diode D11 is reverse biased and cut off because the secondary winding of transformer 4 induces a voltage of opposite polarity to the primary. Therefore, no current flows through the secondary winding, but only current flows through the primary winding, and energy is accumulated by the magnetizing inductance. Next, when the phototransistor is cut off, a voltage having a polarity opposite to that of the previous state is induced in the secondary winding to conduct the diode D11 so that the energy accumulated in the transformer 4 is released. At this time, the capacitor C12 smoothes the pulsed energy transmitted through the diode D11 to make a DC voltage. If Volt.sec equilibrium conditions are applied to the primary side of the transformer 4, the following equations (1) and (2) are given.

Table 1 below shows the input / output voltage relationship of each converter. However, Nr = N2 / N1.

In the above formula, since N1, N2, and Vi are fixed values and the duty D is a variable value, if the duty D is arbitrarily changed to 0 or 1, the output voltage V is varied from 0 to (N2 / N1) xVi. The waveform of the output voltage becomes a sinusoidal wave rectified by the comparison signal 21 supplied from the control signal generator 20 to the PWM conversion switching unit 8.

On the other hand, the comparison signal 21 generated by the control signal generator 20 is input to the (+) terminal of the operational amplifier OP4. At this time, a signal fed back through the photocoupler 9 from the output terminals C and D is input to the negative terminal of the operational amplifier OP4. The two signals are compared and provided to the feedback terminal of the PWM conversion switching unit 8. The PWM converting switch 8 operates with its own switching frequency of several tens of kHz to several hundred kHz. The signal for determining the output duty D of the PWM converting switch 8 becomes the output signal of the operational amplifier OP4. When the signal at the (−) input terminal of the operational amplifier OP4 is smaller than the comparison signal input to the (+) input terminal, the output voltage of the operational amplifier OP4 is increased, and when it is large, the output voltage is decreased.

Referring to FIG. 5, when the anti-sine wave is input as a comparison signal to the self-carrier frequency of the PWM conversion switching unit 8 as shown in 5a, the control signal of the switch 2 is generated by changing the duty as shown in 5b. do. As the comparison signal increases, the duty of the 5b waveform increases and then decreases again. This 5b signal causes a waveform such as 5c to appear at both ends of the switch 2, and the output voltage whose duty is controlled is induced in the transformer 4 as shown in Equation 2 above. The pulse waveform of 5d is obtained by smoothing the waveform with the capacitor C12, and the amplitude is amplified in proportion to the anti-sine wave generated by the control signal generator 20. The 5e waveform is an output waveform 24 of the pulse generator 7 and is a control signal for turning the photocoupler 10 on and off. In other words, through the photocoupler 10 with the square wave signal 24 output from the pulse generator 7 to make the anti-sine wave amplified as 5d into a square wave control signal as shown in 5e and a sine wave as shown in 5f. Drive AC switch 14.

On the other hand, if the anti-sine wave is V, and the current transformer ratio (CRT) of the photocoupler 9 is denoted by h, and the potential between the output terminals C-D is V,

It can be represented as. If you organize this for V _CD ,

It can be represented as.

7 to 10 are diagrams illustrating circuits related to the dummy rods of the filter and the dummy rod unit 11 and the operation waveforms of the first diagram. The dummy load in this embodiment is different from the role of the dummy load in the general DC-DC converter. Although the minimum load of a general DC-DC converter provides the minimum load of the converter, the operation of the PWM conversion switching unit 8 is stabilized. However, in this embodiment, the PWM conversion switching unit 8 operating at several tens of kHz is shown in FIG. Therefore, the high frequency amplified signal generated by the transformer 4 and the rectifier diode D11 serves to discharge the energy charged in the output filtering capacitor C12, which smoothes the signal as shown in 2d of FIG. When the resistor Req is connected as shown in FIG. 7 while the voltage V _C1 is charged to the capacitor C12, the voltage V _C1 of the capacitor C12 is discharged as shown by the b waveform shown in FIG. The voltage V _C1 of the capacitor C12 is expressed as in Equation 5 below.

Therefore, if the equivalent resistance is constant, the output waveform follows the waveform of d in the period t2 to t4 and the curve of b in the period t4 to t5, so that the desired waveform cannot be obtained. That is, in the t4 to t5 section, the control range of the PWM converter is out of range. In order to solve this problem, there is a method of reducing the equivalent resistance value to allow sufficient discharge to occur within the period of t2 to t5.However, in order to do this, the resistance value becomes small and the loss increases in inverse proportion (≒ V _DC ² / Req) It leads to a decrease in overall efficiency. Therefore, it is efficient to use a constant current sink circuit as shown in FIG.

According to FIG. 8, the resistor R33 connected between the base of the transistor Q12 and the emitter determines the magnitude of the sink current, which is I _sink = V _BE / R33. If more current flows, the base current of the transistor Q13 is increased. Sink to transistor Q12 to limit the collector current of transistor Q13. In this circuit, the role of the transistor Q11 is a voltage sensor to prevent unnecessary power loss by controlling the starting point of the constant current sink circuit consisting of the two transistors Q12, Q13 and two resistors R32, R33 to operate from the t3 point in FIG. The operation start voltage is approximately as shown in Equation 6 below.

FIG. 10 shows a waveform obtained by using only the resistance as shown in FIG. 7 as the dummy rod (upper) and the output waveform when using the constant current sink circuit of FIG. 8 (lower). will be. The upper waveform has no zero cross point. This is due to the failure of capacitor C12 to discharge properly. On the other hand, when a forced discharge of the capacitor is induced by using a constant current sink circuit, a zero cross point is detected. FIG. 9 illustrates the factors in which the waveform of FIG. 10 is generated in more detail. In the normal case, a → d may be the principle from t1 to t5, but a1 to t2 may be the same as a → b → d. , t2-t3 is b, and t3-t5 is a → d → b, so it is difficult to detect zero cross.

11A through 11C are circuits for converting an anti-sine wave into a sine wave using a single control signal as an embodiment of the AC switch 14 in FIG. The circuit shown in FIG. 11A is a circuit for inverting phase every cycle by inputting an amplified anti-sine wave. Transistors Q1 to Q4 serve as switches for phase inversion. If the square wave control signal 24 output from the pulse generator 7 is in the low state, the photocoupler 10 is in the off mode, so that the transistor Q1 is turned on by the base current through the base resistor R1, and the emitter-collector of the transistor Q1 is saturated. When the current flows through the transistor Q2 through the resistor R2, the transistor Q2 is turned on. At this time, the two transistors Q3 and Q4 are off because the base current does not flow. Therefore, a path of DC (+) → diode D1 → diode D2 → transistor Q1 → diode D4 → load → transistor Q2 → DC (−) is formed to output a positive waveform. 11B shows the operation circuit at this time.

Next, when the control signal 24 goes high and the photocoupler 10 is turned on, the control signal 24 operates as shown in FIG. 11C. In FIG. 11A, when the voltage drop for normal operation at the emitter-base of the two diodes D1, D2 and transistor Q1 is about 1.5 volts, if the output transistor of photocoupler 10 is completely saturated, 'Vce, s ≒ 0.2V' Since Vce, s + Vd3 ≒ 0.7V, the transistor Q1 is turned off and the transistor Q2 is automatically turned off. Since the switching operation is performed when the output voltage reaches zero volts as in 5d, 5e, and 5f of FIG. 5, switching losses do not occur in each transistor.

12 is an operation waveform diagram according to zero cross detection, where 12a is an output waveform of the photocoupler 9, 12b is a final output waveform, and 12c and 12d are signals 25 to be output from the signal converter 19 to the keyphone (or exchange system). Waveform. Referring to FIG. 4, the signal 23 generated at the emitter terminal of the output transistor of the photocoupler 9 is connected to the (+) input terminal of the comparator COMP2, and compared with the reference voltage Vref connected to the (-) input terminal. 25 has a waveform such as 12c. If the connection between the (+) input terminal and the (-) input terminal is changed, it may be generated as shown in 12d.

As described above, the signal 25 generated through each of the zero cross detection paths consisting of the SCR 17, the photocoupler 18, the signal converter 19 or the feedback converter 16, and the signal converter 19 in FIG. The time when the load is connected to the final output terminal when the output waveform reaches zero potential prevents surge current from flowing. The former path for detecting the final output voltage of the two paths is common, but the latter case is adopted in FIG. The connection of the relay by detecting the zero cross point, that is, the portion having a low potential, is because the relay may be broken when the relay is connected in the high voltage portion, and it is well known to adopt such a method for relay connection.

As described above, the present invention has an advantage of reducing the size of the keyphone system through the miniaturization of a transformer and the simplification of configuration and control of a circuit.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described. Of course, various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the scope of the following claims, but also by the equivalents of the claims.

Claims (14)

A circuit for generating a ring signal by attaching or detaching a relay, comprising: a DC-DC conversion means using pulse width modulation and a control for outputting a predetermined control signal for controlling pulse width modulation switching in the DC-DC conversion means; Signal generating means, phase switching means for switching the phase of the signal output from the DC-DC conversion means in a predetermined period in response to a pulse generated from the control signal generating means to output a sinusoidal wave, and a timing point of generating the ring signal And zero cross detection means for generating a zero cross detection signal to set a time when the sine wave output from the phase shift means reaches a zero potential. 2. The apparatus according to claim 1, wherein the control signal generating means comprises: sine wave generating means for generating a sine wave, full-wave rectifying means for outputting a semi-sine wave obtained by full-wave rectifying the sine wave to the DC-DC conversion means as a predetermined comparison signal; And pulse generating means for generating a predetermined pulse from the sine wave and outputting the predetermined pulse to the DC-DC conversion means. 3. The circuit according to claim 2, further comprising a level shifting means for amplifying the full-wave rectified signal by a predetermined reference voltage at a ground level and outputting it as a comparison signal. The method of claim 1, wherein the phase shifting means is configured to periodically phase a phase of a signal output from the DC-DC conversion means as a photocoupler applied from the pulse generating means and operating in response to a pulse, and the photo coupler is conductive. A circuit comprising an AC switch for switching to. A DC-AC converter circuit comprising: control signal generating means for generating a half-sine wave and a pulse wave, a transformer electrically insulating the input / output, a pulse width converter for adjusting a pulse width in response to the anti-sine wave, and the transformer Switch means connected to a primary side of the pulse width converter and an output terminal of the pulse width converter to induce a predetermined voltage from the primary side to the secondary side of the transformer, and smoothing means for charging and discharging and smoothing the voltage induced on the secondary side of the transformer, The dummy rod for inducing a forced discharge of the energy charged in the smoothing means and the voltage induced on the secondary side of the transformer are fed back and compared with the anti-sine wave output from the control signal generating means and the comparison result is compared with the pulse width converter. Feedback means for controlling the width of the pulse output from the pulse width converter An integrated DC-DC conversion means, an AC switch connected to the secondary side of the transformer to switch the phase of the signal induced at a predetermined cycle, switching control means for controlling a switching operation of the AC switch in response to the pulse wave; And load control means for sensing a signal output from the feedback means and controlling the load to be connected to the AC switch means only at the zero potential of the detection signal. 6. The circuit according to claim 5, further comprising rectifying means for rectifying the voltage induced on the secondary side of the transformer to provide the smoothing means. 7. The feedback device according to any one of claims 5 to 6, wherein the feedback means includes a photocoupler having a light emitting diode connected to a secondary side of the transformer and a light receiving transistor connected to the pulse width converter, and a feedback from the light receiving transistor. And comparing means for comparing the anti-sinusoidal signal with the anti-sine wave to increase the output voltage if the feedback signal is smaller than the anti-sine wave and to lower the output signal if the feedback signal is smaller than the anti-sine wave. 6. A circuit according to claim 5, wherein said switching control means is comprised of a photocoupler. 6. The circuit according to claim 5, wherein the load is a ring generating means of the exchange device. 10. The circuit according to claim 9, wherein the load control means is a main control device for controlling ring generation of the exchange device. 6. The circuit according to claim 5, wherein the dummy rod is composed of a constant current sink circuit. In a key phone system, a control signal generating means for generating a half-sine wave and a pulse wave from a ring signal generating means sine wave that detaches and relays a relay under predetermined control, and generates a ring signal, and a pulse width in response to the half-sine wave. A pulse width converter for adjusting, a power transistor for driving in response to the output of the pulse width converter, a photocoupler having a light emitting diode connected to a secondary side of the transformer, and a light receiving transistor connected to the pulse width converter, and a feedback from the light receiving transistor. A comparator for comparing the signal to the anti-sine wave to raise the output voltage if the feedback signal is smaller than the anti-sine wave and to decrease the output voltage if the feedback signal is larger, and means for rectifying and smoothing the voltage induced on the secondary side of the transformer. DC-DC conversion switching power supply means and the switching power supply in response to the pulse wave Phase switching means for outputting a sinusoidal wave by switching the phase of the phase to a predetermined period, and means for detecting a time point when the sinusoidal wave output from the phase shifting means reaches zero potential, and outputting a relay detachment signal to the ring signal generating means. Ring signal generating circuit characterized in that. 13. The apparatus of claim 12, wherein the phase shifting means comprises a photocoupler operating in response to the applied pulse wave, and an AC switch for periodically switching the phase of the switching power supply as the photocoupler is conducted. Circuit. 13. The circuit according to claim 12, further comprising a dummy rod made of a constant current sink circuit to induce a forced discharge of energy charged in the smoothing means.