JPH0691745B2 - Voltage resonant converter - Google Patents

Description

TECHNICAL FIELD The present invention relates to a general-purpose DC-DC converter characterized by low noise, high efficiency, large power, and low cost, and more particularly to a voltage resonance converter.

(Prior Art and Problems to be Solved by the Invention) Various DC-DC converters have been conventionally proposed. As these DC-DC converters, there are those shown in FIGS. 5 to 7.

FIG. 5 shows an on-off type converter with a power supply voltage V ₁
Is turned on and off by the transistor Q ₀ , and the primary winding of the transformer T ₀
The current of n ₀₁ is interrupted, the voltage induced in the secondary winding n ₀₂ of the transformer T ₀ is rectified by the diode D, smoothed by the capacitor C and converted into the output voltage V ₀ . Transistor Q ₀ is a transformer
The base circuit is driven by the voltage induced in the tertiary winding n ₀₃ of T ₀ , and oscillates according to the constants of each part. Since this circuit cannot operate in the quasi-E class operation, the loss is large and there is a problem in high efficiency and miniaturization.

Further, shown in FIG. 6 is a voltage resonance type on-off converter, which also connects and disconnects the current of the primary winding n ₀₁ of the transformer T _{0 by} the transistor Q ₀ to output the DC power supply V ₁ to the output voltage V _0.
Convert to. In this circuit, the inductance of the primary winding n ₀₁ of the transformer T ₀ and the capacitor C ₀ resonate to regulate the oscillation frequency. In this converter, the turn-off characteristic of the transistor Q ₀ is poor and the loss is large. Therefore, there is a problem in improving efficiency.

Further, FIG. 7 shows a separately-excited voltage resonance type converter, in which the DC power supply V ₁ is turned on and off by turning on and off the transistor Q _0.
Convert to V ₀ . This converter has an output voltage control function. That is, the output voltage V ₀ is input to the error amplifier 1, is input to the amplifier 3 via the photocoupler H (insulating the secondary side of the transformer T from the primary side), and the current of the flywheel diode is changed. This is a separately-excited voltage resonance type converter which detects by a current transformer CT, drives a synchronous oscillator 4, inputs its output to an amplifier 3, and drives a transistor Q ₀ . This converter has a problem that the circuit configuration is complicated and the cost is high.

The present invention has been made in view of the above problems, and an object thereof is to provide a voltage resonance type converter characterized by low noise, high efficiency, large power, and low cost.

(Means for Solving the Problems) The present invention has been proposed to achieve the above object,
A voltage obtained by connecting an on / off switching element in series with the primary winding of the transformer, driving the switching element with the induced voltage of the tertiary winding of the transformer, and rectifying and smoothing the output of the secondary winding of the transformer. A resonance type converter is provided with a detection circuit for detecting a resonance current, and the voltage resonance type converter is characterized in that an output of the detection circuit turns off the switching element via a transistor.

(Examples) Examples of the present invention will be described below with reference to the drawings.
Needless to say, the embodiment is merely an example, and various modifications and improvements can be made without departing from the spirit of the present invention.

FIG. 1 is a circuit diagram showing a first embodiment of the present invention, in which V ₁ is a DC power source, C ₁ is a smoothing capacitor on the power source side, T ₁
Is a transformer for conversion in which primary winding n ₁₁ , secondary winding n ₁₂ , and tertiary winding n ₁₃ are wound, D is a rectifying diode, C is an output-side smoothing capacitor, and C ₂ is a resonance. Capacitor, D ₁ is a diode, D ₂ and D ₃ are detection diodes, Q ₁ is an on / off transistor, Q ₂ is a transistor for turning off transistor Q ₁ , and C ₃ is a base circuit capacitor for transistor Q _1. .

Next, the operation of this circuit will be described with reference to the waveform chart of FIG.

The present invention is an on / off type voltage resonant converter which is a quasi-E class converter. This circuit configuration detects the resonance current If of the resonance capacitor, detects the voltage V _D of the diode D ₁ with the diodes D ₂ and D ₃ for detection, turns on the transistor Q _2, and turns on and off the transistor that is a switching element.
By turning off the Q ₁ rapidly, while the voltage across V _CE of the transistor to Q ₁ for off does not rise, that suppress the loss of the transistor Q ₁ to interrupt the current I _C of the transistor to Q ₁ for OFF Is. V _BE is transistor Q
_{1 is} the base-emitter voltage.

Next, FIG. 3 is a circuit diagram showing a second embodiment of the present invention, in which the detection diode of the first embodiment shown in FIG.
The resistor R is used instead of D ₂ and D ₃ .

FIG. 4 is a circuit diagram showing a third embodiment of the present invention, in which the detection diode of the first embodiment shown in FIG.
The current transformer CT ₁ is used instead of D ₂ and D ₃ .

The circuits shown in FIGS. 3 and 4 are similar to the operation of FIG. 1 only with the detection circuit changed.

(Effects of the Invention) As described above, according to the present invention, the switching element for ON / OFF is connected in series with the primary winding of the transformer, and the switching element is driven by the induced voltage of the tertiary winding of the transformer, In a voltage resonance type converter obtained by rectifying and smoothing an output of a secondary winding of the transformer, a detection circuit for detecting a resonance current is provided, and the output of the detection circuit turns off the switching element via a transistor, It is possible to provide a low-voltage, high-efficiency, high-power, and low-cost voltage resonant converter.

[Brief description of drawings]

1, 3, and 4 show the first, second, and third aspects of the present invention, respectively.
2 and 3 are circuit diagrams showing the third embodiment, FIG. 2 is a waveform diagram for explaining the operation of FIG. 1, and FIGS. 5 to 7 are circuit diagrams showing various conventional converters. T ₁ …… Transformer, D, D ₁ …… Diode, D ₂ , D ₃ …… Detection diode, C, C ₁ , C ₂ , C ₃ …… Capacitor, Q ₁ …… On / off transistor, Q ₂ … ... transistor

Claims (1)

[Claims] 1. A switching element for ON / OFF is connected in series with a primary winding of a transformer, and the switching element is driven by an induced voltage of a tertiary winding of the transformer, and
A voltage resonance type converter in which an output of a secondary winding is rectified and smoothed, comprising a detection circuit for detecting a resonance current, and the output of the detection circuit turns off the switching element via a transistor. Type converter.