JPS6041817A - Triac controller - Google Patents

Abstract

PURPOSE:To attain accurate zero cross trigger for a TRIAC independently of a frequency with simple circuit constitution by controlling the trigger timing of the TRIAC by means of a microcomputer. CONSTITUTION:The hardware is simplified and the accurate zero cross triggering for the TRIAC by using an interruption signal generating circuit 2 outputting an interruption signal at a point of time earlier than the zero cross point of a power supply voltage from an output (a) of a diode bridge circuit 1 full-wave- rectifying a voltage from an AC power supply by a time corresponding to the frequency, a microprocessor 3 counting the time corresponding to the frequency of the power supply voltage and generating the trigger signal when the interruption signal is inputted and a TRIAC trigger circuit 4 triggering an objective TRIAC5 in response to the trigger signal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for controlling the trigger of a triac.

[Prior art]

When using a TRIAC to continuously supply power to a load such as a heater (in order to prevent noise generation due to sudden changes in load current, the TRIAC is triggered when the power supply voltage is zero). A zero cross trigger is applied.

However, it is actually difficult to have an accurate zero-cross trigger, that is, to completely match the zero-cross point and the trigger timing, and the circuit configuration to achieve this must be complicated. When the frequency of the power supply changes (for example, from 50I (from z to 60Hz)), it is necessary to change the circuit constants accordingly.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned circumstances, and its object is to achieve accurate zero-cross triggering of a triac regardless of frequency with a simple circuit configuration.

[Structure of the invention]

Therefore, the present invention uses a microcomputer to control the triac trigger timing as follows. That is, the present invention detects a zero cross at a point earlier than the zero cross point of the power supply voltage by a time corresponding to the frequency of the power supply voltage, and inputs this as an interrupt signal to a microprocessor (CPU), thereby changing the frequency to the above frequency. A timer that counts the corresponding time is started, and when the count of the timer ends, an interrupt process is performed in which the bird outputs a signal of 11'', and a trigger signal from the microprocessor causes the triac to be activated via the triac ignition means. It is designed to be triggered.

〔Example〕

A specific example of this invention will be described below with reference to accompanying drawings.

I will explain about it.

FIG. 1 is a circuit diagram of a triac control device according to the present invention. This device consists of an interrupt signal generating circuit (2 ) and a microphone [co-processor (3) that receives the output from this circuit (2) and performs predetermined interrupt processing.
) and a triac ignition circuit (4) that triggers the target triac (5) in accordance with the output from the microprocessor t (31 units).

This specific example is used as a control device for a copying machine, and as shown in the figure, the power supply voltage whose phase is controlled by a triac (5) is input to AClooV and also to an interrupt signal generation circuit (2). The voltage is a full-wave rectified voltage of 24 V AC (Fig. 2) for driving the electromagnetic clutch, relay, etc. in the copying machine.

The interrupt signal generation circuit (2) consists of two resistors R, R2 that divide the output of the diode bridge circuit (1), and two resistors R3 and R4 that divide the DC constant voltage (5V).
The power supply voltage divided by these two sets of voltage dividing resistors is compared with the constant voltage, and when the former becomes lower than the latter, a voltage that changes from high level to low level (Fig. 2 ■) is output. A comparator (6) is provided. The way the low voltage is output from this comparator (6) is not clear from Figure 2 ■ and ■ (2. Zero cross point L1 + j of power supply voltage
It has an equal time width before and after 4+j3+..., and the time width is determined by the frequency of the power supply voltage.

That is, the time width T when the power supply frequency is 50 Hz.

is large, and the time width T2 in the case of 60H7 is small.

Therefore, the low voltage output of this comparator (6) is
The microprocessor (
3) is input.

When the above-mentioned interrupt signal is input, the microprocessor (3) starts a timer that counts the time corresponding to the frequency of the power supply voltage, and when the count ends, the bird performs an interrupt process in which a signal is generated.

That is, the frequency of the power supply voltage is set in advance in the microprocessor (3), and the above-mentioned interrupt processing is performed by inputting the above-mentioned interrupt signal. Therefore,
In the illustrated example, a manual operation switch (7) is connected to one end of the microprocessor (3), and a constant voltage (+5V) is applied between the two through a resistor.

Therefore, turning on and off the manual operation switch (7)
ヲ7i; Frequency of source voltage 50Hz, 60Hz (m
If you let people deal with it, MicroProcera! ) (3
) C. The frequency of the voltage for 7 (i) can be identified by the voltage applied by the switch (7) (+5 V when the switch (7) is OFF, ov when it is ON), and the corresponding timer operation can be performed. .

Thus, when the microprocessor (3) receives an interrupt signal (■ in Figure 2) from the interrupt signal generation circuit (2), it starts the above-mentioned interrupt processing, and after a predetermined time has elapsed, the microprocessor (3) generates a pulse signal (
Figure 2 ■) is generated.

- It is important that the timing at which this bird generates a pulse coincides with the zero-crossing point of the power supply voltage, as is clear from the figure. 1- i.e. microprocessor (3
) is the time from the generation of the interrupt signal to the zero-crossing point of the power supply voltage, which is equal to half the time width of the low voltage output from the interrupt signal generation circuit (2). Therefore, the timer operation 11.1 can be appropriately set by the value of the voltage dividing resistor that determines the input terminal to the comparator (6) in the interrupt signal generating circuit (2).

For example, in the illustrated example, the power supply frequency is 50Hz.
In the case of , timer operation time 'll''+ = 1506
'I'2 = 1.26 for sec +60Hz
By setting p see , no matter what the power supply frequency is,
(Stop 2V) can be obtained.

The triac ignition circuit (4) converts the negative tri-pulse signal from the microprocessor (3) into an inverter (8).
), and its inverted output is applied to the base of the transistor (10) via the resistor (9), and this transistor (
10) is turned on, a trigger voltage Vt (Fig. 8) is applied to the negative side of the pulse transformer (11), and the secondary voltage ignites the triac (5).
It is composed of Therefore, when a trigger pulse is output from the microprocessor (3) at the zero-crossing point of the power supply voltage, the voltage V2 across the triac (5) changes as shown in FIG.

〔Effect of the invention〕

2, the device of the present invention causes the microprocessor to perform predetermined interrupt processing at a point before the zero-crossing point of the power supply voltage, and generates a trigger doubler at the point when the zero-crossing point coincides with the zero-crossing point. Since the hardware is simple, it is possible to realize inexpensive and accurate zero-cross firing of the triac.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing a specific example of the device of the present invention, Fig. 2 is a voltage waveform diagram at each point in the circuit of Fig. 1, and Fig. 8 shows the triac trigger heavy use and both voltages. FIG. Explanation of symbols (1)... Rectifier circuit (2)... Interrupt signal generation circuit (3)... Microprocessor (
4)...Triac ignition circuit (5)...
...Triac (6) ...Comparator (7
)...Manual operation switch (8)...
Inverter (10)...Transistor (11)
...Pulse transformer patent applicant Fuji Xerox Co., Ltd.

Claims (1)

[Claims] An interrupt signal generating means for generating an interrupt signal at a time corresponding to the frequency earlier than the zero crossing point of the power supply voltage, and a timer for counting the time corresponding to the frequency when the interrupt signal is input. A triac comprising: a microprocessor that performs interrupt processing for starting and outputting a signal when the timer finishes counting; and triac ignition means for triggering the triac in response to a trigger signal from the microprocessor. Control device.