CN2039028U - Dynamic-characteristics tester for a thyristor - Google Patents

Abstract

Thyristor dynamic characteristics tester adopts synchronous pulse delay control circuit, power MOSFET is used as power switch element, realizes internal automatic switching power supply, and is equipped with manual switch, which can conveniently observe and test many dynamic characteristics of thyristor and diode, and has a high degree of integration , stable and reliable work, low power consumption, light weight, low price, it is an ideal experimental test equipment.

Description

The utility model is a thyristor dynamic characteristic tester for teaching experiments.

The thyristor is a high-power semiconductor device, which has developed rapidly in recent years and has been widely used in various fields of the national economy. Due to its continuous development and continuous expansion of applications, a new discipline - power electronics has been formed. According to the development of the national economy and the needs of colleges and universities to cultivate talents, the course of power electronic devices has been listed as an important course for many years. This course covers the internal mechanism, external characteristics (static and dynamic characteristics) and measurement methods of various high-power semiconductor devices such as thyristors. The dynamic characteristics of thyristors are important characteristics (such as turn-on characteristics, turn-off characteristics, etc.), especially for devices working in high-frequency applications. However, the currently opened experiments usually only measure the static characteristics, and the dynamic characteristics measurement has been difficult to set up. Today, some manufacturers in my country generally develop their own measuring equipment for dynamic characteristics. Each equipment can only measure one parameter, such as on-time measurement and off-time measurement. needs. Even such test equipment is not specially produced and difficult to purchase. Due to the long-term inability to set up dynamic characteristic test experiments, it will have a negative impact on the teaching effect.

The purpose of the utility model is to design a thyristor dynamic characteristic tester with good performance to meet the needs of experimental teaching. The tester has wide measurement range, low price and reasonable structure.

The technical solution of the utility model is to use an adjustable constant current source circuit to provide the required constant on-state current to the device under test Th, see Figure 2, so as to ensure the reliable conduction of the device under test. The switch S ₁ is closed, the constant current source output tube BJT works in the amplified state, the switch S ₂ is closed, the device under test is triggered to conduct, and the on-state current controlled by the BJT flows. When the device under test is turned on for a certain period of time, the switch _S3 is closed, and a reverse voltage is applied to the device under test, the on-state current will decrease and reverse at a certain rate of decline -di/dt, and the reverse current will flow. Until the reverse blocking state is restored. Thereafter, switch _S4 is turned on at an appropriate moment, and the device under test is given a forward voltage with a certain du/dt. The on-off of all switches is controlled by synchronous pulse delay to realize the function of automatic switching. Use the dual-trace oscilloscope to observe the current and voltage waveforms of the device under test to measure the required dynamic parameters.

Description of drawings:

Fig. 1: System block diagram of the utility model;

Figure 2: Switching of power supply;

Figure 3: Pulse forming circuit;

Figure 4: Constant current source control circuit;

Figure 5: Gating circuit and sync pulse delay circuit;

Figure 6: Delay control circuit;

Figure 7: Reverse voltage control and -di/dt circuit;

Figure 8: Re-add off-state voltage control and du/dt circuit.

Embodiment is described with reference to accompanying drawing:

As shown in Figure 3, the synchronous pulse forming circuit is composed of TC4572. The power frequency voltage is added to the input terminal of TC4572 after full-wave rectification, and the amplitude is less than 10V. After pulse shaping, delay adjustment, etc., a square wave pulse with good front and rear edges is obtained. After passing through the power amplifier, the required square wave pulse can be obtained. Change the resistance Rp ₁ to make the phase shift of the pulse in the range of 0.5ms～3ms, change the resistance Rp ₂ to make the pulse width adjustable between 0.3ms～5ms. The output pulse amplitude is 10V.

The synchronous pulse signal firstly controls the constant current source and the gate control circuit to work. When the synchronization pulse arrives, the output tube BJT works and is in an amplified state, so that the main circuit power is added to the device under test Th. The constant current source circuit uses a two-stage composite tube as the driving stage to improve control sensitivity. As shown in Figure 4, changing the resistors R _I1 and R _I2 can adjust the output current of the constant current source to obtain the required on-state current of the device under test. As shown in Figure 5, the synchronization pulse applied to the gating circuit is obtained after being delayed by the operational amplifier A ₀ , the resistor Rg ₀ , the capacitor Cg ₀ , the regulator tube DW ₀ and the transistor BG ₀ , and the pulse is simultaneously sent to the delay The input terminal of the circuit, the delay circuit is composed of op amp A ₁ , resistor Rg, capacitor Cg, voltage regulator tube DW ₁ and transistor BG ₁ , the op amp A ₁ works, the output signal drives BG ₁ to conduct, and will be added to the gate The delayed synchronous pulse of the control circuit is blocked, that is, a narrow pulse output is obtained. When Rg=12KΩ, Cg=3000PF, the pulse width is 36μs. In order to prevent the influence of the main circuit on the control circuit, a photocoupler LED is installed at the input end of the constant current source circuit and the gate control circuit. In order to meet a certain power requirement, the photocoupler is GD05.

As shown in Figure 6, the delay control circuit is composed of operational amplifiers A ₁ , A ₂ , A ₃ and A ₄ and corresponding resistors and capacitors. In order to increase the reliability of the delay and simplify the power supply, op amps A ₁ and A ₂ share a single power supply dual op amp amplifier LM358, which does not require external zero adjustment and is easy to use. The op amp A ₃ only uses half of LM358, and the op amp A ₄ can use F007. The synchronization pulse is delayed by Rd ₁ , Cd ₁ and Rd ₂ , Cd ₂ to reach the required delay. Resistor Rd ₁ selects a potentiometer with a resistance value of 4KΩ, when Cd ₁ = 0.02μF, Rd ₂ = 65KΩ, and Cd ₂ = 3600PF, change the delay of resistor Rd ₁ to 0.35ms. The delayed pulse _P1 is sent to the -di/dt circuit. The pulse delayed by op amp A ₂ , resistor Rd ₁ , and capacitor Cd ₁ is further delayed by op amp A ₄ , resistor Rd ₃ , and capacitor Cd _3. Rd ₃ is connected in series with a 150KΩ potentiometer and a 1KΩ resistor, and Cd ₃ = 3700PF, the delay can reach 0.3ms. Changing the resistance Rd ₃ delay is adjustable between 2μs ~ 0.3ms. The input pulse of the delay circuit is added to the inverting terminal of the operational amplifier _A4 to obtain the inverse delayed pulse _P3 . Pulse _P2 is sent to du/dt circuit.

As shown in Fig. 7 and Fig. 8, the work of -di/dt circuit and du/dt circuit is controlled by power MOSFET. The power MOSFET is an enhanced device, and the drain-source current is controlled by the gate bias voltage. After the pulse _F1 is amplified, it is added to the gate of the power MOSFET of the -di/dt circuit to turn it on, and the reverse voltage can be applied to the device under test, and the on-state current decreases according to a certain -di/dt. The pulse P ₂ is added to the gate of the power MOSFET of the du/dt circuit to make it change from conduction to cut-off, and a certain du/dt forward voltage is applied to the device under test.

Advantages and characteristics of the utility model:

1. The whole device has low power consumption (about 25W), small size (400×350×250mm ³ ), light weight (less than 15Kg), and is easy to carry.

2. As long as the capacity of the output tube of the constant current source is increased, and the power MOSFETs of the -di/dt circuit are connected in parallel, the device under test with a larger capacity can be measured.

3. Manual switches Si and Su are set between the -di/dt circuit and du/dt circuit and the main circuit, respectively, and various dynamic characteristics such as conduction and reverse recovery of the device under test can be tested respectively under different conditions.

4. When the Th and du/dt circuits of the device under test are not connected, short-circuit the anode and cathode terminals of the circuit to test the reverse recovery characteristics of the diode.

5. Equipped with SR-8 dual-trace oscilloscope, it can measure the Kp5 thyristor and Zp5 diode, and the work is stable.

Claims (5)

1. A thyristor dynamic characteristic tester is controlled by a synchronous pulse to a constant current source circuit, a gate control circuit, a -di/dt circuit and a du/dt circuit, and is characterized in that: (1) The synchronous pulse is composed of TC4572. The power frequency sine wave voltage is full-wave rectified and then added to the pulse forming circuit. After pulse shaping and amplification, a square wave pulse with an amplitude of 10V is obtained. The phase shift is adjustable from 0.5ms to 3ms. The width is adjustable from 0.3ms to 5ms, the synchronous pulse directly controls the work of the constant current source, changing the resistors R _I1 and R _I2 can adjust the constant current output current, adjustable between 0 and 10A, the synchronous pulse passes through the operational amplifier A ₀ and the resistor R _g0 , capacitor C _g0 , voltage _regulator tube DW _{0 ,} and transistor BG ₀ generate a 0.1ms delay and _then control the gate control circuit to _{work .} The composed delay circuit makes the gate control circuit generate a narrow pulse, triggers the device under test to be turned on, and the synchronous pulse is controlled by the delay control circuit to work -di/dt circuit and du/dt circuit. The delay control circuit is composed of operational amplifier A ₁ , A ₂ , A ₃ , and A ₄ , resistors R _d1 , R _d2 , R _d3 , and capacitors C _d1 , C _d2 , and C _d3 are composed of A ₁ , A ₂ , A ₃ and R _d1 , R _d2 , C _d1 , C _d2 delays to get the synchronous pulse P ₁ , the delay time is 0.35ms, after A ₃ , R _d3 , C _d3 delays to get the inversion pulse P ₂ , the delay time is adjustable from 2μs to 0.3ms, and the operational amplifiers A ₀ , A ₁ , A ₂ and A ₃ use single power supply and double op amp LM358, and op amp A ₄ uses F007; (2) The constant current source circuit, the gate control circuit and the synchronous pulse delay control circuit are isolated by the photocoupler GD05; (3) The on-off of -di/dt circuit and du/dt circuit is realized by power MOSFET. 2. The tester according to claim 1, characterized in that when the constant current source and the gating circuit work, the -di/dt circuit and the du/dt circuit do not work, and the diode terminal is short-circuited to observe the measured Turn-on and on-state characteristics of device Th. 3. The tester according to claim 1, characterized in that when the device under test Th is turned on, the -di/dt circuit is operated by a manual switch, and a reverse voltage is applied to Th to test the reverse recovery characteristic of Th . 4. The tester according to claim 1, characterized in that when the device under test Th has been applied with a reverse voltage, the du/dt circuit is operated by a manual switch, a forward voltage is applied to Th, and the Ru test Th is adjusted. break feature. 5. The tester according to claim 1, characterized in that the main circuit is connected to the anode and cathode terminals of the device under test, and the constant current source works to make the diode conduct, and then manually makes the -di/dt circuit work, Apply a reverse voltage to the diode to test the reverse recovery characteristics of the diode.

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