SCR Applications Circuits

在本文中，我们将学习许多有趣的SCR应用程序电路，并学习主要功能和SCR的属性also called a thyristor device.

什么是可控硅或晶闸管

SCR is the acronym of Silicon Controlled Rectifier, as the name suggests it's a kind of diode or a rectifying agent whose conduction or operation can be controlled through an external trigger.

这意味着该设备会响应外部小信号或电压而打开或关闭，这与晶体管完全相似，但与其技术特性大不相同。

SCR C106 pinouts

看着图，我们可以看到SCR有三个导线，可将垫子识别如下：

Keeping the printed side of the device facing us,

• 右端导线称为“大门”。
• 中心线是“阳极”，并且
• The left end lead is the "Cathode"

How to Connect an SCR

The gate is the trigger input of an SCR and requires a DC trigger with a voltage of around 2 volts, the DC should be ideally more than 10mA. This trigger is applied across the gate and the ground of the circuit, meaning the positive of the DC goes to the gate and the negative to the ground.

施加栅极触发器时，跨阳极的电压传导和阴极的传导被打开，反之亦然。

The extreme left lead or the cathode of an SCR should always be connected to the ground of the triggering circuit, meaning the ground of the triggering circuit should be made common by connecting to the SCR cathode or else the SCR will never respond to the applied triggers.

载荷始终连接到阳极和AC电源电压上，这可能是激活负载所需的。

SCR专门适合切换交流负载或脉冲DC负载。纯净或干净的直流负载将无法与SCR一起使用，因为直流将对SCR产生闩锁效果，即使在卸下栅极扳机后，也不会关闭。

SCR Application Circuits

In this part, we will look at some of the popular applications of SCR which are in the form of static switch, a phase-control network, SCR battery charger, temperature controller, and a single-source emergency-lighting
system.

系列静态开关

A half-wave series static switch can be witnessed in the following figure. When the switch is pressed to allow the supply in, current at the gate of the SCR becomes active during the positive cycle of the input signal, switching ON the SCR.

amo电阻器R1控制和限制unt of gate current.

In the switched ON condition the anode to cathode voltage VF of the SCR decreases to the level of the conduction value of RL. This causes the gate current to reduce drastically, and minimum loss at the gate circuitry.

During the negative input cycle, the SCR is switched OFF, because of the anode getting more negative than the cathode. Diode D1 safeguards the SCR from a reversal of the gate current.

The right side section of the above image shows the resulting waveform for the load current and the voltage. The waveform looks like a half-wave supply across the load.

Closing the switch allows the user to achieve a conduction level lower than 180 degrees at phase displacements happening during the positive period of the input AC signal.

For achieving conduction angles between 90° and 180°, the following circuit can be used. This design is similar to the above, except the resistor, which is in the form of the variable resistor here, and the manual switch is eliminated.

The network using R and R1 ensures a properly controlled gate current for the SCR during the positive half cycle of the input AC.

将可变电阻器R1滑动臂移至最大或最低点，栅极电流可能变得太弱，无法到达SCR的门，这将永远不会让SCR打开。

On the other hand when it is moved upwards, the gate current will slowly increase until the SCR turn ON magnitude is reached. Thus, using the variable resistor the user is able to set the level of the turn ON current for the SCR anywhere between 0° and 90°, as indicated at the right hand side of the above diagram.

对于R1值，如果相当低，则会导致SCR快速发射，从而导致从上面的第一个图（180°传导）获得的类似结果。

However, if the R1 value is bigger, a higher positive input voltage will be needed to fire the SCR. This situation wouldn't allow us to extend the control over 90° phase displacement, since the input is at its highest level at this point.

如果SCR无法在此级别或AC循环正斜率下输入电压的较低值发射，则对于输入循环的负斜率，响应将完全相同。

从技术上讲，SCR的这种类型的工作称为半波变量抗性相位控制。

This method can be effectively used in applications requiring RMS current control or load power control.

使用SCR的电池充电器

Another very popular application of the SCR is in the form of电池充电器控制器。

在下图中可以看到基于SCR的电池充电器的基本设计。阴影部分将是我们的主要讨论领域。

The working of the aboveSCR controlled battery chargercan be understood with the following explanation:

The input stepped down AC is full wave rectified through the diodes D1, D2 and supplied across the SCR anode/cathode terminals. The battery which is under charging can be seen in series with the cathode terminal.

When the battery is in the discharged condition, its voltage is low enough to keep the SCR2 is the switched OFF state. Due to the open state of SCR2, the SCR1 control circuit behaves exactly like our series static switch discussed in the previous paragraphs.

With the input rectified supply adequately rated, triggers ON the SCR1 with a gate current that's regulated by R1.

This instantly turns ON the SCR and the battery begins charging via the anode/cathode SCR conduction.

In the beginning, due to the low discharged level of the battery, the VR will have a lower potential as set by the R5 preset or potential divider.

At this point the VR level will be too low to turn ON the 11 V zener diode. In its non-conducting state the zener will be almost like an open circuit, causing the SCR2 to be completely switched OFF, due to virtually zero gate current.

Also, the presence of C1 ensures that the SCR2 is never accidentally turned ON due to voltage transients or spikes.

随着电池充电，其端子电压逐渐上升，最终在达到设置的全充电值时，VR就足以打开11 V Zener二极管，随后在SCR2上启动。

As soon as SCR2 fires, it effectively generates a short circuit, connecting R2 end terminal to ground, and enabling the potential divider created by R1, R2 network at the gate of the SCR1.

The activation of the R1/R2 potential divider at the gate of SCR1 causes an instant drop in the gate current current of SCR1, forcing it to shut off.

This results in the supply to the battery getting cut off, ensuring the battery is not allowed to over charge.

After this, if the battery voltage tends to drop below the preset value, the 11 V zener switches OFF, causing SCR1 to switch ON yet again to repeat the charging cycle.

AC Heater Control using SCR

The above diagram shows a classic加热器控制application using an SCR.

The circuit is designed to switch ON and OFF the 100 watt heater depending on the thermostat switching.

A mercury-in-glassthermostatis used here, which are supposed to be extremely sensitive to the changes in the temperature levels surrounding it.

To be precise it can sense even a change of a 0.1°C temperatures.

However, since thesetypes of thermostatsare normally rated to handle very small magnitudes of current in the range of 1 mA or so, and therefore it is not too popular in temperature control circuits.

在讨论的加热器控制应用中，SCR用作放大恒温器电流的电流放大器。

Actually, the SCR does not function like a traditional amplifier, rather as a当前传感器, which allows the varying thermostat characteristics to control the higher current level switching of the SCR.

我们可以看到，SCR的电源是通过加热器和完整的桥梁整流器应用的，这允许SCR的全波整流DC供应。

在此期间，当恒温器处于开放状态时，跨0.1UF电容器的电势通过每个校正的DC脉冲产生的脉冲电势充电到SCR栅极电势的触发水平。

The time constant for charging the capacitor is established by the product of the RC elements.

这使得在这些脉冲可控硅进行d DC half cycle triggers, allowing the current to pass through the heater, and allow the required heating process.

As the heater heats up and it temperature rises, at the predetermined point, causes the conductive thermostat to activate and create a short circuit across the 0.1uF capacitor. This in turn switches OFF the SCR and cuts off power to the heater, causing its temperature to drop gradually, until it drops to a level where the thermostat yet again is disabled and the SCR fires ON.

Emergency Lamp using SCR

The next SCR application talks about a single-sourceemergency lamp designin which a6 V battery保持在充电的充电条件下，以便每当发生电源故障时，连接的灯都可以无缝打开。

When power is available, a full wave rectified DC supply using D1, D2 reaches the connected 6 V lamp.

C1 is allowed to charge to a level that's slightly lower than the difference between the peak DC of the fully rectified supply and the voltage across R2, as determined by the supply input and charge level of the 6 V battery.

在任何情况下，SCR的阴极电势水平都高于其阳极高，并且阴极电压的门也为阴性。这确保SCR保持在非导电状态。

The charging rate of the attached battery is determined by R1, and enabled through the diode D1.

充电仅限A D1阳极的持续时间比其阴极更为正。

While the input power is present, the full wave rectified across the emergency lamp keeps it switched ON.

During power failure situation, the capacitor C1 begins discharging through D1, R1, and R3, until the point where the SCR1 cathode becomes less positive than its cathode.

Also, meanwhile the R2, R3, junction goes positive resulting in an increased gate to cathode voltage for the SCR, turning it ON.

The SCR now fires and allows the battery to get connected with the lamp, instantly illuminating it through battery power.

The lamp is allowed to stay in the illuminated state as if nothing had happened.

When power returns, the capacitors C1 is yet again recharged, causing the SCR to switch OFF, and cutting off the battery power to the lamp, so that the lamp now illuminates through the input DC supply.

从本网站收集的其他SCR应用程序

Simple Rain Alarm:

The above circuit of a rain alarm can be used for activating a AC load, like a lamp or an automatic folding cover or shade.

The sensor is made by placing to metallic pegs, or screws or similar metal over a plastic body. The wires from these metals are connected across the base of a triggering transistor stage.

传感器是电路唯一放置在室外的部分，以感知雨水降落。

当降雨开始时，水滴将传感器的金属桥接。

Small voltage start leaking across the sensor metals and reach the base of the transistor, the transistor immediately conducts and supplies the required gate current to the SCR.

The SCR also responds and switches ON the connected AC load for pulling an automatic cover or simply an alarm for correcting the situation as desired by the user.

SCR窃贼警报

我们在上一节中讨论了有关SCR的特殊属性，其中它响应直流负载而锁定。

The circuit described below exploits the above property of the SCR effectively for triggering an alarm in response to a possible theft.

Here, initially the SCR is held in a switched OFF position as long as its gate stays rigged or screwed with the ground potential which happens to be the body of the asset which is required to be protected.

如果通过拧开相关螺栓来窃取资产的尝试，则将其删除SCR的地面电势，并通过连接到其底座和正面的相关电阻器和正面的相关电阻来激活晶体管。

The SCR also instantly triggers because now it gets its gate voltage from the transistor emitter, and latches sounding the connected DC alarm.

The alarm remains switched ON until its switched OFF manually, hopefully by the actual owner.

Simple Fence Charger, Energizer Circuit

SCRs becomes ideally suited for makingfence charger circuits. Fence chargers primarily require a high voltage generator stage, where a high switching device like an SCR becomes highly imperative. SCRs thus become specifically suitable for such applications where they are used for generating the required high arcing voltages.

CDI Circuit for Automobiles:

As explained in the above application, SCRs are also widely used in automobiles, in their ignition systems.Capacitive discharge ignition circuitsor CDI systems employ SCRs for generating high voltage switching required for the ignition process or for starting a vehicle ignition.