JPS62281761A - Control circuit for semiconductor device - Google Patents

Abstract

PURPOSE:To dispense with resistors and eliminate overvoltage, by setting a semiconductor switch to be of a phase angle control system, and by increasing the current angle slowly to suppress rush current to a capairtor. CONSTITUTION:With AC voltage from terminals 1, 2, a condenser 20 is charged via a transformer 13, a diode bridge 14, and resistors 15, 20. when the charged voltage comes to the breakover voltage of a pulse element 19 or more, then the voltage flows to the gate of a thyristor 17 through the pulse element 19. Besides, the luminous diode 16 of a photocoupler 6 connected to the thyristor 17 in series is illuminated and is received by a photodetector 7, and a semiconductor switch 8 is put in a conductive state. As a result, the charged voltage flows to a smoothing condenser 12, and the then conduction angle of the switch 8 is set to be the same as that of the thyristor 17, and so the current flows in a narrow state and rush current is suppressed. when the potential of the condenser 12 is risen and comes to Zener voltage or more, then the thyristors 17, 8 are always set in an ON-state via a thyristor 25.

Description

[Detailed description of the invention] 3. Detailed description of the invention [Industrial application field] Semiconductor rectifier device 1 (especially switching regulator)
The present invention relates to a control circuit for a semiconductor device that suppresses inrush current that occurs when power is turned on.

[Conventional technology]

In conventional technology, as a measure to prevent inrush current to the capacitor at startup, a resistor is connected in parallel to the semiconductor switch, and at startup, a photoelectric current is applied to the capacitor through the resistor until the semiconductor switch opens. The semiconductor switch is closed during the time period when the potential of In connection with this circuit, the Shinkosha edition of ``How to Design Switching Regulators and How to Use Power Devices'' is known.

An example of a conventional circuit is shown in FIG. First, in Figure 2, in the conventional circuit, when a commercial frequency AC voltage is input to terminals 1 and 2, a photocurrent flows through the resistor 4 and diode bridge 5 to the smoothing capacitor 6. . When the potential of transistor 6 reaches a predetermined value, the drive circuit 12 of transistor 11 operates, transistor 11 starts switching at a predetermined frequency, and a voltage is generated in winding i8. The semiconductor switch (TRIAC) 3 is driven by the voltage generated in the winding 8, and becomes in a 2A conduction state.

In this circuit, the inrush current to the smoothing condenser 6 is limited by the resistor 4, but the current flows through the resistor 4 until the semiconductor switch 3 becomes conductive, resulting in a loss of V2/R. In addition, AC R and EErI applied to terminal 1.2
Since the turning-on phase is not constant, if the turning-on phase is turned on at 90 degrees in the worst case, a high dv/dt will be applied, causing malfunction.

[Problem that the invention seeks to solve]

The above conventional techniques have the following problems.

(1) The capacity of the resistor for preventing inrush current at startup is large and null. w = V2/R, = 1kw short Rfjl't'6 ruka 20 or so is required.

(2) Depending on the type of resistor inserted, power distribution, and wiring method,
Due to the inductance and contact chatter, i
A! This causes pressure and excessive d v/d t . (Destruction/erroneous firing) 3) In the case of a single-type switching regulator, the firing current of a semiconductor switch is often converted from current to DC at the switching frequency, resulting in a problem if the switching frequency is low. However, as the frequency increases, the pulse width of the ignition current becomes narrower and a larger current is required. For example, with a switching frequency of 200 KHz, the gate signal pulse width of the semiconductor switching element is r11 μs. The device's thermal time is about 1 .mu.s, which is on the verge of ignition and causes 9 hot spots with poor spread at turn-off.

The present invention was conceived to solve these problems.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention has the following features: (1) The ignition method of the semiconductor switch is a phase angle control method, the conduction angle is gradually increased from small to large, and the inrush current to the capacitor 7 is reduced. suppress. The method of gradually changing the conduction angle is controlled by using changes in the potential of the smoothing capacitor. By doing this, an inrush current prevention resistor becomes unnecessary. Also, overvoltage,
The cause of excessive dv/dt is eliminated.

(2) When the potential of the smoothing capacitor reached a zero level, a DC level current was applied to the gate signal of the semiconductor switch.

〔Example〕

An embodiment of the present invention is shown in FIG. 1 below.

Fig. 1rr In the operation of the embodiment of the present invention, when a commercial frequency or current voltage is input to the terminals 1 and 2, the capacitor 20 is It will be charged. When the charging voltage of the capacitor 20 exceeds the breakover voltage of the pulse element 19, the energy of the capacitor 20 is transferred to the pulse element 19.]
9 to the gate of thyristor 17. resistance 23
, the time constant determined by the capacitor 20 is determined by the thyristor 17.
fires. It is advantageous to set the phase angle to be large (on the contrary, the conduction angle is small), so that thyristor 1 is fired when the 0 firing phase is large, and the photocoupler is connected in series to thyristor 17. 6 light emitting diodes 16
A t-current flows through and emits light. The light-emitting energy is received by the light-receiving element 7, and the light-receiving element 7 becomes conductive. When the light receiving element 7 becomes conductive, the semiconductor switch 8 passes through the resistor 6.
becomes conductive, and a photocurrent flows to the capacitor 7 and the capacitor 12. The conduction angle of the semiconductor switch at this time is the thyristor 1.
7, the flow flows with a narrow conduction angle and is suppressed by a large inrush ilt flow. By increasing the potential due to the photocurrent flowing to the smoothing capacitor, or by using that potential to photoelectrically conduct the capacitor 20 through the resistor 22 and the diode 21, the phase angle becomes smaller and the conduction angle becomes larger. , the potential of the smoothing capacitor 12 rises roughly to 4T0, and the potential of the smoothing capacitor 12 increases to the Zener diode 2
When the zener voltage exceeds 60, the zener diode 2
Since current flows to the gate of the thyristor 25 through 6, the thyristor 25 is turned on, and the smoothing capacitor 1
2 flows to the thyristor 25, the resistor 24, the light emitting diode 6, and the thyristor 17;
A current higher than the holding current always flows through the
The light emitting diode has a shape without a light emitting block.

Therefore, the semiconductor switch 8 is also always in a continuous state. The present invention eliminates the need for a resistor for preventing inrush current, resulting in excessive d
The application of v/dt is also eliminated. Further, the gate signal of the semiconductor switch 8 becomes a DC level signal.

〔Effect of the invention〕

According to the present invention, resistance can be stopped and false #
It is possible to prevent J cropping.

[Brief explanation of drawings]

Figure 1 is a circuit diagram of an embodiment of the control circuit for the semiconductor device of the present invention, Figure 2 is a circuit diagram of a conventional device, and Figure 3 is another embodiment of the control circuit for the semiconductor device of the present invention. FIG. 2 is an explanatory diagram of a state in which a rush current prevention circuit is inserted into the DC j@ of the diode bridge for use in the present invention. 8... Semiconductor switch, 12... Flat i capacitor.

Claims (1)

[Claims] 1. A rectifier circuit with a capacitor smoothing circuit. In order to suppress the rush current flowing into the capacitor at startup, the conduction angle is gradually expanded by phase control of the semiconductor switch, and the conduction angle control power source is used to control the charging voltage of the smoothing capacitor. A control circuit for a semiconductor device, characterized in that when the potential of a smoothing capacitor is established at a certain value by utilizing the change in potential of the semiconductor switch, a direct current is caused to flow through the semiconductor switch.