JPS5995618A - Phase controller - Google Patents

Abstract

PURPOSE:To obtain a phase controller which eliminates the need to provide a voltage level detecting circuit individually by composing the phase controller of a reference pulse detecting circuit, input voltage detecting circuit, control angle arithmetic device, and trigger pulse generating circuit. CONSTITUTION:The reference pulse detecting circuit 11 discriminates the level of an input voltage by a reference level whose pulse width depends upon the input voltage and generates a reference pulse. This reference pulse is sent to a differentiating circuit 12 to detect its rise and fall. A pulse-width measuring timer 13 measures the width theta of the reference pulse and a signal indicating the pulse width theta is sent to the input voltage detecting circuit 14, where the input voltage V is calculated. The control angle arithmetic device 15 calculates a control angle alpha according to the input voltage V so that a given control value E is satisfied. The trigger pulse generating circuit 18 outputs a trigger pulse with constant width when a time-up signal corresponding to a control angle beta is supplied from the device 15. Thus, the need to provided the voltage level detecting circuit individually is eliminated.

Description

BACKGROUND OF THE INVENTION The present invention relates to a phase control device, and more particularly to a conduction phase angle control device for switching elements such as Zyristors and triacs.

FIG. 1 shows a conventional phase control device. A full-wave rectified signal (in phase with the current waveform supplied to the load) is input to a zero-crossing detection circuit (1), which detects its zero-crossing point. That is, at the time when the aftereffect rectification input becomes zero, a reference pulse (zero cross signal) is input from the leverage detection circuit (moon) to the trigger pulse generator (21).

A control input representing a desired load current or phase angle etc. is input to the trigger pulse generator (2). This trigger pulse generator (2) generates a trigger pulse for making the switching element conductive at a phase angle represented by the control input with respect to the zero-crossing signal. Since the zero cross detection circuit (1) detects the reference zero cross point, it is preferable to detect that point extremely accurately, and for this purpose, the threshold level for detecting zero cross should be set as close to zero potential as possible. The conventional method was to set the level.

By the way, when the input voltage (power supply voltage) fluctuates, even if the conduction phase angle of the switching element is controlled to be constant, the integrated value of the current flowing through the switching element (the total amount of current flowing when the switching element is in a conductive state) When the current changes, the amount of current applied to the load changes. Therefore, a voltage level detection circuit (3) is provided in order to correct changes in the amount of energization due to fluctuations in input voltage. This detection circuit (3) detects the full-wave rectified input voltage (the input voltage itself or is proportional to it), for example, its peak value, and its detection signal is input to the trigger pulse generator (2).

The pulse generator (2) includes a correction circuit for input voltage fluctuations, and generates a tri-force pulse by correcting the phase angle determined by the control input according to the voltage level detection signal number.

In this way, in the conventional phase control device, the zero-crossing detection circuit that detects the reference zero-crossing point is fl
A voltage level detection circuit was required on the way.

Summary of the Invention An object of the present invention is to provide a phase control device that does not require a separate voltage level detection circuit.

This invention focuses on providing a circuit for detecting a reference point with a function of detecting an input voltage level, and this reference pulse detection circuit detects an input voltage at a predetermined level such that pulse +lJ depends on the input voltage There is also a method that discriminates and generates a reference pulse. The phase control device according to the present invention further includes a device that generates a trigger pulse with a phase according to a control input (control value) using the reference pulse as a reference. means for determining the input voltage, a given control value, and the determined pulse 1] and means for determining the control angle based on the input voltage, and when a time corresponding to the control angle determined with reference to the reference pulse has elapsed; It consists of means for generating a trigger pulse.

The reference point and input voltage are determined based on the reference pulse output from the reference pulse detection circuit.

Therefore, there is no need to provide an input voltage level detection circuit in addition to the zero-cross detection circuit as in the prior art. Then,
The control angle is calculated based on the obtained reference point, input voltage, and given control value, so that the amount of current flowing through the switching element is always constant regardless of fluctuations in the input voltage.
A pulse can be generated that triggers the switching element.

Description of examples FIG. 2 shows an example of a phase control device.

AC input type E (supplied to a load controlled by a switching element, or similar)
The input is input to a reference pulse detection circuit (11;). This detection circuit +111 generates a reference pulse by level-discriminating the input voltage at a reference level such that the pulse IJ depends on the input voltage. It is shown in FIG.

In FIG. 3, the reference pulse detection circuit (11) is composed of a full wave rectifier circuit (21+) and a level discrimination circuit (2).The aftereffect rectifier circuit c111 is a diode-bridge circuit as is well known. The level discrimination circuit (Inc.) consists of a Zener diode that determines the reference level Vr, and a comparator circuit that discriminates the output voltage of the aftereffect rectifier circuit 01) based on this reference level Vr. A positive pulse (reference pulse) is generated from the comparator 04) when the aftereffect rectified voltage becomes lower than the reference level Vr.

The full wave rectified voltage and reference pulse are shown in FIG. When the full-wave rectified voltage falls and becomes below the reference level Vr, the reference pulse rises, and when the full-wave rectified voltage rises and becomes above the reference level Vr after passing through the voltage zero point, the reference pulse is activated. fall As can be clearly seen from this figure, the reference pulse pulse []1θ changes depending on the input voltage, and the lower the voltage, the larger the pulse width θ. That is, as the voltage decreases (shown by the dashed line) the reference pulse rises earlier and falls later. This means that the reference level Vr is
This is because the pulse width of the reference pulse is set to a level that depends on the input voltage.

This can be explained quantitatively as follows.

When the full-wave rectified voltage is V and its effective value is V, V is expressed by the following equation.

Therefore, the following equation is obtained.

The effective value V is derived from equation (1) as follows.

r Further, θ is given by the following equation.

It will be understood that the input voltage (effective value V) can be determined by measuring rlJθ of the reference pulse.

In FIG. 2, the reference pulse output from the reference pulse detection circuit (11) is sent to the differential circuit (17Jl), and its rise and fall are detected (see FIG. 4).The pulse width measurement timer t13 is It measures the width θ of the reference pulse, and is started by the rising detection signal of the reference pulse and stopped by the falling detection signal. represents the width θ of the reference pulse. A signal representing the pulse width θ is sent to the input voltage detection circuit 141, where the (
2) Input voltage V is calculated based on the formula. The rising detection signal of the differential circuit (121) is also applied to the control angle timer 0η, which is an amount representing the integrated value of the current to be passed through the sending element (control value E
). This control value E may be set in advance as a target value, or may be determined based on the deviation between the detected value and the target value detected by detecting the output amount of the control equipment, such as the amount of heat or displacement.

The control angle calculating device Q51 calculates the control angle α according to the input voltage V so as to satisfy the given control value E. In FIG. 5, the phase angle at which the switching element is in the conducting state is referred to as the conducting phase angle θ. The integrated value of the current flowing through the switching element is the integral value ゛s (area indicated by diagonal lines) of this conduction phase angle θ, which is given by the following formula = 5・V・(1−cosθt)・...(4
) Since the given control value E can be considered to be approximately proportional to this area S, if E=-8 (Ic is a proportionality constant), the following equation is obtained from equation (4).

From Equation (5), the conduction phase angle θt corresponding to the given control value E can be determined according to the input voltage V.

In order to trigger the switching element, it is necessary to determine the phase angle difference, ie, the control angle α, from the voltage zero point to the point of triggering. This control angle α is given by the following equation using the conduction phase angle θt.

α engineering, -〇L -・-+61 control angle timer (
1η is the control angle β given to timer 071 since the timing starts from the rise of the reference pulse rather than from the voltage zero point.
The following formula is adopted.

θ β=α+) θ = π−θ also 10− (7) The control angle calculation device (15) is connected to the input voltage detection circuit (141
Then, the conduction phase angle θ is calculated by equation (5) using the voltage V and control value E input from the control value determination circuit, and the pulse [■ jilIII measurement [1jθ] input from the constant timer αJ is calculated. The control angle β is calculated using equation (7) and this β is given to the timer (171).

The control angle timer 071 is activated by the rising edge of the reference pulse as described above, and outputs a time-up signal when its clocked (counted) value reaches a value corresponding to the control angle β given by the arithmetic unit (15). . Trigger pulse generation circuit (I81 is a one-shot circuit, for example,
Outputs a trigger pulse of a certain width when a time-up signal is input. This trigger pulse is input to the gate of the switching element, and the switching element becomes conductive until the next voltage zero point due to the trigger pulse.

The functions of the input voltage detection circuit 04) and the control angle calculation device (15) shown in FIG. 2, as well as the overall operational control of phase control, can also be realized by a microprocessor. In this case, a timer (for example, in a predetermined area of memory) provided in the microprocessor such as the timer 1131 (t17) may be used instead. FIG. 6 shows the phase control procedure by the microprocessor.

In Figure 6, when the rising edge of the reference pulse is detected (
For example, an interrupt) (step 01)), a pulse width measurement timer and a control angle timer are started (step @ (3)
31). Next, when the falling edge of the reference pulse is detected (step 041), the operation of the pulse width measurement timer is stopped (step (351)), and the measured pulse width θ is read (step (3[il)). Input voltage V is calculated by equation (2) using this pulse width θ (step +371).Control value E is read (step (sub));

Using the calculated input type EV and the read pulse width θ, the control angle β is calculated according to equations (5) and (7) (step (39+). This control angle β is input to the control angle timer. is set (step (40)) and waits for the timer to time up. When the control angle timer times out (step +411), a trigger pulse is output (step (4)), and after a certain period of time rij has elapsed, this pulse is Output is stopped (step f431 +44)
).

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a conventional example, Fig. 2 is a block diagram showing an embodiment of the present invention, Fig. 3 is a circuit diagram showing an example of a reference pulse detection circuit, and Figs. 4 and 5 show the operation. FIG. 6 is a waveform diagram for explanation and a flowchart showing the processing procedure when the present invention is implemented using a microprocessor. fill..., reference pulse detection circuit, (131--pulse IJ measurement timer, (141--input voltage detection circuit,
1151, Control angle calculation device, (1η... Control angle timer, +181-Φ, Trigger pulse generation circuit.

Claims (1)

[Claims] A reference pulse detection circuit that generates a reference pulse by level-discriminating the input voltage at a required reference level such that the pulse [11] depends on the input voltage; means for determining the control angle based on the given control value and the determined pulse width and input voltage; and a trigger when the time corresponding to the determined control angle has elapsed with reference to the reference pulse A phase control device comprising means for generating pulses.