JPS5929404Y2 - Zero potential control circuit - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a zero potential control circuit capable of noiseless power control.

Phase control or on/off control has conventionally been used as a power control method using Cyrisk.

Phase control is a method of controlling load power by triggering a sirisk at an arbitrary phase of AC voltage, but because the current flowing to the load rises suddenly, noise radio waves are generated, which can interfere with broadcast frequencies. I'm going to call you.

Therefore, a noise removal filter is required.

Further, on/off control is a method of controlling the on/off of a thyristor using a signal such as temperature, but the on signal is controlled by temperature etc. and is unrelated to the AC power supply voltage.

Therefore, the trigger phase of Cyrisk is rarely near the zero potential of the AC power supply voltage, and most of them are outside the zero potential, and like phase control, noise is generated every time an on signal is input.

On the other hand, zero-potential control enables power control without generating such noise, and eliminates the risk at the point when the current flowing through the load is zero, that is, when the voltage value of the AC power supply voltage passes through zero. By turning it on or off, interference with broadcast frequencies is minimized, and at the same time, a noise removal filter is not required.

The circuit used in this control method can be constructed at a much lower cost than the circuit used in the conventional power control method, and is also smaller, so it is used in many fields such as temperature control.

By the way, cutting off the current flowing through the Cyrisk while the AC voltage passes through the zero voltage point is not a problem since the Cylisk will turn off if the current flowing through the Cyrisk becomes less than the holding current of the Cyrisk.

However, in order to turn on the Cyrisk at the zero voltage point, a zero potential control circuit is required to supply a gate trigger signal to the Cyrisk at the zero voltage point.

FIG. 1 is a diagram showing a conventional example of such a zero potential control circuit.

In the figure, numeral 3 denotes a two-way conduction type three-terminal SIRISK (hereinafter simply referred to as SIRISK), which is connected to the AC power supply 1 in series with the load 2.

The AC power supply 1 is an ordinary commercial power supply 6. Note that 4 is the gate power supply of Cyrisk, and 5 is the first anode electrode.

6 is a DC power supply for supplying a gate trigger signal, which is connected to the gate electrode 4 of the thyristor 3 via a gate control switch 7 that is switched depending on temperature or the like and a gate current limiting resistor 8 connected in series with the gate control switch 7; It is connected.

The resistors 9 and 10 and the transistors 11 and 12 constitute a zero potential detection circuit, and the emitter of the transistor 11 and the base of the transistor 12 are connected in common, and are connected to the first anode electrode 5 of the thyristor 3 and one end of the AC power supply. ing.

Furthermore, the base of transistor 11 and transistor 1
The two emitters are commonly connected and connected to the other end and one end of the AC power source via bias resistors 9 and 10.

The collector of the transistor 11 and the collector of the transistor 12 are commonly connected to the gate electrode 4 of the thyristor 3.
is connected to the gate current, forming a shunt for the gate current.

In such a configuration, when an alternating current voltage is applied from the alternating current power supply 1, when the other end of the alternating current power supply has a positive voltage with respect to one end of the alternating current power supply connected to the first anode electrode 5 of the thyristor 3, the transistor 11 Iasu resistance 9 on the base of
A base current flows through the transistor 11, and the transistor 11 is turned on.

- In the case of a negative voltage, a closed circuit is formed between the base of the transistor 12, the emitter, the bias resistor 9, and the AC power supply 1, and current flows through the base of the transistor 12, so that the transistor 12 is turned on.

Therefore, both transistors 11 and 12 are turned off at the same time when the voltage of the traffic power supply 1 is close to zero voltage, and moreover, in a low voltage region where the base current necessary to maintain the transistors 11 and 12 in the on state cannot be supplied. Only.

Since the transistors 11 and 12 constitute a shunt for the gate current of the thyristor 3, the gate electrode of the thyristor 3 is connected to the DC power supply only in the phase near the zero potential of the AC voltage, when both the transistors 11 and 12 are in the OFF state. A gate trigger signal is applied from 6, and the thyristor 3 is triggered.

Triggering at other phases is prohibited.

That is, due to the operation of the zero potential detection circuit, the gate current continuously supplied from the DC power supply 6 in synchronization with the opening and closing of the gate control switch 7 is applied to the gate of the thyristor 3 only when the potential is very close to zero. Since the current flows to the electrode 4, zero potential control is reliably performed.

According to the conventional zero potential control circuit, although zero potential control is performed as described above, the following disadvantages cannot be avoided.

That is, transistors 11 and 12 are connected to thyristor 3.
When trying to completely turn on these transistors, the gate current is shunted to the transistor 11 in the positive voltage range of the AC power supply voltage.
The bias current divided by the DC current amplification factor is required,
Further, in the negative voltage range, it is necessary to flow a bias current equal to the emitter current of the transistor 12, that is, the gate current of the thyristor 3 through the resistor 9.

Figure 2a shows the AC voltage waveform.
In the positive voltage range, the bias current is small, so the voltage drop due to the resistor 9 is small, and the transistor 11 switches when the value of the AC voltage is approximately the pace-emitter voltage VBE of the transistor 11. However, in the negative voltage range, the gate current flows through the resistor 9, so the voltage drop vT is large and the transistor 1
2 switches at this voltage drop vT.

Therefore, when the gate trigger current of the thyristor 3 is large, the voltage drop vT becomes larger and larger, and when the gate control switch 7 is turned on in the negative voltage range, when the AC voltage is -vT, that is, far from the zero phase point, This causes the inconvenience that the thyristor 3 is triggered and generates noise.

On the other hand, if the resistance value of the resistor 9 is made small in order to reduce the voltage drop vT caused by the resistor 9, the power consumption in the resistor 9 increases, causing problems in mounting due to heat generation and the like.

The present invention was made with the intention of eliminating the disadvantages that exist in the conventional zero potential control circuit, and provides an improved zero potential control circuit that is not affected by gate current etc. .

FIG. 3 is a diagram showing a zero-voltage phase detection circuit according to an embodiment of the present invention. As shown in the figure, a gate current shunting transistor 12 of opposite polarity to the transistor 11 is connected to the conventional circuit shown in FIG. 1. In addition, the collector of the transistor 11 and the emitter of the transistor 13 are connected in common, and the collector of the transistor 12 is connected to the base of the transistor 13.

In the zero potential control circuit of the present invention shown in FIG. Current i.e. transistor 12
Only the base current of the transistor 13 and the base current of the transistor 13 flow, and the gate current is shunted by the transistor 13.

Therefore, the voltage drop across the bias resistor 9 is very small, and its value is f'ff degrees of the pace emitter voltage (VBB) of the transistor 13, and the trigger phase point is at zero phase, as shown in FIG. 2C. It will be extremely close.

As a result, the generation of broadcast frequency interference noise becomes extremely small.
There is no need to use a noise reduction filter at all.

FIG. 4 shows another embodiment, in which a transistor 14 and a gate current limiting resistor 15 are connected in series between the gate circuit 7 and the gate electrode 4 of the thyristor 3.
By connecting the emitter of the transistor 13 which shunts the gate current to the base of the transistor 14, the transistor 14 operates as an emitter follower.

According to such a configuration, shunt transistors 11 and 13
Due to the presence of the transistor 14, the current flowing into the circuit is one part of the DC current amplification factor of the transistor 14 compared to that of the circuit shown in FIG. Reduced.

Therefore, even in the case of a large gate current, zero potential control can be performed reliably.

As is clear from the above embodiments, according to the present invention, by simply adding one transistor to a conventional circuit, zero potential control can be reliably performed without being affected by the magnitude of the gate current. Effects can be achieved in terms of implementation, such as eliminating noise prevention filters and downsizing circuit installation.

Note that the above explanation was about injecting a gate current, but if the gate current is negative, the polarity of the DC power supply and the polarity of the transistor can be reversed at the same time.
Also, Cyrisk is a unidirectional conduction type, so there is no problem with it.

[Brief explanation of drawings]

Figure 1 is a conventional zero potential control circuit diagram, and Figure 2 is a waveform diagram of each part to explain the operation of the zero potential control circuit, where a shows the AC power supply voltage waveform, and b and c show the on/off waveforms of the shunt transistor. . 3 and 4 are diagrams showing specific circuit examples of the zero potential control circuit according to the present invention. 1...AC power supply, 2...Load, 3...
・・・Bidirectional conduction type 3 terminal Cyrisk, 4・・・・・・
・Date electrode, 5...First anode electrode, 6.
...DC power supply, 7...Gate circuit, 8,
15...Current limiting resistance, 9,10...
Bias resistor, 11, 12.13... shunt transistor, 14... emitter follower transistor.

Claims (1)

[Scope of utility model registration request] A DC power supply serving as a gate trigger signal source is connected to the gate of the SIRISK connected in series with the load between both terminals of the AC power supply via a gate control switch and a gate current limiting resistor, and further includes a collector. is connected to one end of the gate current limiting resistor connected to the gate electrode of the thyristor, the emitter is connected to the connection point between the anode electrode of the thyristor and one end of the AC power supply, and the base is connected between the AC power supply terminals. a first transistor connected to a series connection point of at least two series-connected resistors; an emitter and a base connected to the base and emitter of the first transistor; a second transistor having one polarity, a base and a collector connected to the collector and base of the second transistor, an emitter connected to the collector of the first transistor, and a second transistor having a polarity opposite to that of the first transistor; A zero potential control circuit comprising a zero potential detection circuit configured with a third transistor.