KR960000823Y1 - Transistor speed-up circuit - Google Patents

Abstract

No content.

Description

Transistor speed-up circuit

1 is a conventional switching transistor driving circuit diagram

2 is a transistor speed-up circuit diagram according to the present invention

3 is a diagram showing transistor turn-on and off curves according to the present invention.

* Explanation of symbols for main parts of the drawings

D1: Rectifier Q1 ~ Q3: Transistor

R1 ~ R4: Resistance T1: Transformer

C1 ~ C4: Capacitor D2 ~ D4: Diode

L1: coil a1 ~ a4: coil of transformer

The present invention relates to a transistor speed-up circuit, and more particularly to a transistor speed-up circuit that speeds up the switching speed of a transistor in a circuit using a bipolar transistor for an electronic fluorescent ballast and a switching mode power supply (SMPS). .

In other words, the present invention improves the switching speed of switching transistors in electronic fluorescent lamp ballasts and SMPSs using bipolar transistors, and reduces the loss of switching transistors, thus improving the reliability and efficiency of products. It is about.

In the conventional bipolar transistor using circuit, as shown in FIG. 1, the output of the diode D1 rectifying the AC voltage to the DC voltage is connected to the resonant coil L1 through a smoothing electrolytic capacitor C1 connected in parallel and is resonant. The other side of the coil L1 is commonly connected to one end of the start resistor R1 and the middle end of the primary coil a1 of the crank T1, and the other end of the start resistor R1 is the bipolar transistor Q1. Is commonly connected to the base of the transistor and current limiting resistor R2, and is commonly connected to the base of the transistor Q2 and the current limiting resistor R3 through the coil a2 of the transformer T1. The other end of R3 is connected and commonly connected to one end of the capacitor C4 and the cathode of the diode D4, and the anode end of the diode D4 is connected through the coil a3 of the transformer T1. The other end of C4) and each emitter end of transistors Q1 and Q2 are commonly connected. Diodes D2 and D3 are connected to the collector-emitter stages of the transistors Q1 and Q2, respectively, and each collector stage of the transistors Q1 and Q2 is connected to both ends of the primary coil a1 of the transformer T1. A series configuration of capacitors C2 and C3 is connected in parallel to the transformer T1 primary coil a1.

The operation state of the configuration circuit will be described below.

When the AC voltage is applied, the waveform full-wave rectified by the rectifying diode D1 becomes a DC voltage by the electrolytic capacitor C1 ( (Input AC voltage)).

When the generated DC voltage is applied to the base of the bipolar transistor Q1 through the resonant coil L1 and the resistor R1, and the transistor Q1 is in an operating state, the voltage is induced in the transformer T1, that is, Designed frequency ( A voltage having a value of) is induced, and a voltage having an appropriate magnitude is induced from the induced voltage to the coils a2 to a4 of the transformer T1 according to the turn ratio of the transformer T1. That is, the voltage induced in the coil a3 of the transformer T1 becomes the DC voltage through the diode D4 and the capacitor C4, and passes through the current limiting resistors R2 and R3 to the bases of the transistors Q1 and Q2, respectively. The voltage is always supplied, and the base voltage is supplied to be operated at a 'high'-'low' voltage by alternating the voltage supplied to the bases of the transistors Q1 and Q2 with the voltage induced in the coil a2 of the transformer T1.

Thus, the transistors Q1 and Q2 operate alternately. When the transistors Q1 and Q2 do not operate, the internal energy of the transistors Q1 and Q2 is quickly returned to their original state through the freewheeling diodes D2 and D3, respectively, and the coil L1 and the capacitors C2 and C3 are returned to their original state. Is a component designed for the transistors Q1 and Q2 to operate at the resonance point (the point at which the current is zero).

However, in the related art, there is no circuit for increasing the speed of the transistors Q1 and Q2 as described above. However, when the transistors Q1 and Q2 are 'off', the internal energy is quickly restored to the original state. Since only D3) is connected, the switching speed is not increased when the transistors Q1 and Q2 are turned on, and thus there is a disadvantage in that the loss is large (in the case of a transistor having a slow switching time, the loss is large).

Accordingly, an object of the present invention is to provide a speed-up circuit that can reduce losses during turn-on of a switching transistor, which will be described below in detail with reference to the accompanying drawings.

First, as shown in FIG. 2, the output of the diode D1 rectifying the AC voltage to the DC voltage is connected to the resonant coil L1 through a parallel electrolytic capacitor C1 connected in parallel, and the resonant coil L1. Is connected to one end of the start resistor R1 and the middle end of the primary coil a1 of the transformer T1, and the other end of the start resistor R1 is the base and current of the bipolar transistor Q1. It is commonly connected to the limiting resistor R2 and simultaneously connected to the base of the transistor Q2 and the current limiting resistor R3 through the coil a2 of the transformer T1 and to the other of the current limiting resistors R2 and R3. One end is connected to the emitter of the transistor Q3 and the collector of the transistor Q3 is connected to the resistor R4 connected to the base end of the transistor Q3 to connect the one end of the capacitor C4 and the diode D4. Common to the cathode stage and the anode end of diode D4 is the coil of transformer T1. The common terminal is connected to the other end of the capacitor C4 and the emitter terminals of the transistors Q1 and Q2 through (a3), and the base of the transistor Q3 passes through the diodes D2 and D3, respectively. It is connected to the collector of Q2), and is connected to both ends of the transformer (T1) primary side coil a1, and the series configuration of the capacitors C2 and C3 is connected in parallel to the transformer (T1) primary side coil a1. .

The operation state of the configuration circuit will be described below.

The basic operation state of the present invention is the same as that of the prior art configuration, except that the voltage induced in the coil a3 of the transformer T1 becomes the DC voltage through the diode D4 capacitor C4, and the DC voltage is driven by the transistor. Amplified while passing through the resistor R4 and the transistor Q3, the amplified current is supplied to the bases of the switching transistors Q1 and Q2. The diodes D2 and D3 are connected to the collectors of the switching transistors Q1 and Q2 at the base of the transistor Q3, so that the diodes D4 and C4 are turned on and off during the switching transistors Q1 and Q2. After passing through the diodes D2 and D3, the voltage except for the down voltage (0.6V) is always applied to the collectors of the switching transistors Q1 and Q2 so that the switching time is turned on and off. This leads to faster transistor losses.

In this case, the transistor turn-on and turn-off curves (that is, the collector-emitter waveforms of the transistors Q1 and Q2) are the same as in the third degree.

As in the waveform of FIG. 3, the turn-on time at the time of transistor turn-on is reduced from a 'to a "with diode addition, and from b' to b" when off. In this case, diodes D2 and D3 must use a diode having a high reverse voltage, a fast recovery type, and a transistor for amplifier Q3 must be used.

Therefore, the present invention has the effect of reducing the switching time during turn-on and turn-off by applying a constant DC voltage to the collector of the switching transistor through the diode.

Claims (1)

In the switching transistor driving circuit which drives the switching transistors Q1 and Q2 using the (correction) transformer T1, Induced in the coil (a3) of the transformer (T1) is applied to the base through the resistor (R4) to the DC voltage by the diode (D4) and the capacitor (C4) to amplify and applied to the base of the switching transistor (Q1, Q2) The transistor Q3 and the base terminal of the transistor Q3 and the collector terminals of the switching transistors Q1 and Q2 are respectively connected to reduce switching losses of the switching transistors Q1 and Q2. Transistor speed-up circuit comprising a diode (D2, D3).