JPH062475Y2 - Switching power supply - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a switching power supply. Conventionally, this type of switching power supply device has been shown in the circuit diagram of FIG. 1, for example. That is, Q ₁ is a driving transistor, Q ₂ is a reverse bias transistor, Q ₃ is a main switching transistor, Q ₁ adds an input signal to the base B ₁ , and turns on Q ₁ by the driving power supply VB. , and turned on the _{Q 3} in the main switching transistor _{Q 3} flows the base current iB _1. Further, by providing a reverse bias power supply -VB, it adds an input signal to the base B ₂ of the reverse bias transistor _{Q 2,} by turning on the _{Q 2,} the _{Q 3} by supplying a reverse base current iB ₂ to _{Q 3} The switching speed to the off state was increased. First
In the switching power supply unit of figure as this is supplied via the rectifier such power from main input power + Vcc by a transformer T by turning on and off the Q ₃ to load L. Therefore, in the conventional device, both the drive power source + VB and the reverse bias power source -VB are prepared, which is troublesome in terms of circuit configuration and has the drawback of increasing the number of parts.
The present invention solves the above-mentioned drawbacks of the conventional device, and provides a switching power supply device having a simple circuit configuration and high speed.

Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 2 is a circuit diagram showing an embodiment of the present invention, and the same symbols as in FIG. 1 show the same parts. Base _{B 1} of the driving transistor _{Q 1}
Adding an input signal Q ₁ is turned on to when the base current iB
₁ flows, the main switching transistor Q ₃ also turns on, and the collector current Ic flows as shown in the operation waveform diagram of FIG. Then Q ₁ is turned off, the collector current Ic of Q ₃ when Q ₂ is turned on by an input signal to the base B ₂ of the reverse bias transistor Q ₂ is continues to flow due to the accumulation effect, the emitter of this period Q _3, to base The voltage is short-circuited and has a small value. In the figure, the rectifier diode D ₁ to the emitter of Q ₃ is connected to the rectifying direction of flow emitter current of Q _3, the relationship of the collector-emitter voltage VCE ₂ of the forward voltage VF, Q ₂ of D ₁ is VF> VCE ₂ during the accumulation time. Therefore, the base-emitter of Q ₃ is reversely biased, and the reverse base current iB ₂ flows through Q ₂ . Then, when the accumulation effect of Q ₃ disappears, the reverse bias state is released, iB ₂ decreases, and Ic also stops flowing.

In the present invention, as shown in FIG. 1, a reverse bias power source -V
It is not necessary to provide B, Q ₁ and Q ₂ are connected in series, a driving power source + VB is added to this, the midpoint of Q ₁ and Q ₂ is connected to the base of Q ₃ , and rectifier diode D ₁ are connected in the direction of flow a emitter current of Q ₃ to the emitter side of the Q ₃ a. Therefore, only by adding the rectifying diode D ₁ , the number of power sources can be reduced, the circuit configuration is simplified, and the number of parts can be reduced. In the present invention, replacement of transistors with PNPs, addition of components usually provided as a switching power supply device, and equivalent changes in circuit configuration are included in the scope of the present invention. As described above, the present invention provides a high-speed switching power supply device having a simple circuit configuration and a small number of parts, and has a great practical effect.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a conventional switching power supply device, FIG. 2 is a circuit diagram of an embodiment of the device of the present invention, and FIG. 3 is an operation waveform diagram of the device of the present invention. Q ₁ is a driving transistor, Q ₂ for reverse bias transistor, Q ₃ is the main switching transistor, T is a transformer, D ₁ is the rectifier diode, L is the load, VB is a power source for driving, -VB power for reverse bias,
+ Vcc is a main input _{supply, B 1,} B ₂ is _Q 1, _{Q 2} each of the base, iB ₁ base current iB ₂ of _{Q 3} are the reverse base current of _{Q 3,} Ic is the collector current of _{Q 3.}

Claims (1)

[Scope of utility model registration request] 1. A drive transistor Q ₁ and a reverse bias transistor Q ₂ connected in series to a drive power source are connected,
The midpoint between Q ₁ and Q ₂ and the base of the main switching transistor Q ₃ are connected, and the load and the transistor Q ₃ are connected.
And a rectifying diode is connected between the emitter of Q _{3 and} the emitter of Q ₂ in a direction to flow a current to the load.