JP3375457B2 - Switching power supply - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching power supply device for switching a DC voltage to convert the voltage and supplying the voltage to a load.

[0002]

2. Description of the Related Art A conventional switching power supply device will be described with reference to FIG. In FIG. 3, 1 is a DC power supply, 2 is a FET for switching a DC voltage, 3 is a control circuit for turning on / off the FET 2, 4 and 5 are coils and capacitors for smoothing the switched voltage, and 6 is for forming a return circuit. , The resistors 7 and 8 divide the load voltage, 9 and 11 are resistors, and 10 is a load.

The control circuit 3 outputs a pulse having a constant repetitive cycle. When the load voltage divided by the resistors 7 and 8 is lower than a set value, the output pulse width is increased, and when the load voltage is increased, the pulse is narrowed. FIG. 4 shows the pulse voltage output from the control circuit 3, and when the pulse voltage becomes 0 V, F
When the gate voltage of ET is lowered and the FET2 is turned on, when the pulse voltage becomes + V, it is turned off.

When the FET 2 is turned on and off, the energy stored in the coil 4 at the time of turning on is smoothed by the capacitor 5 via the diode 6 at the time of turning off and supplied to the load 10.

[0005]

As described above, in the conventional switching power supply device, the FET is turned on / off by the pulse voltage output from the control circuit. FE
There is a capacitance between the gate and source of T, and because of this capacitance, control is performed as shown by the dotted line even if the control signal shown by the solid line in FIG. 4 is applied, and loss occurs during this period. It becomes less efficient.

An object of the present invention is to provide a switching power supply device improved so as to have high efficiency.

[0007]

Means adopted by the present invention for solving the above-mentioned problems will be described. A switching element for switching a DC voltage, a control voltage generating means for generating a control voltage for turning on / off the switching element according to an output voltage, and a DC voltage for turning on / off the DC voltage based on a control voltage from the control voltage generating means. A driving means for turning on / off the direct current voltage of the voltage adding means, the direct current voltage is divided by a resistor, and the divided voltage is generated through the diode to generate the control voltage. It connects to the output of the means and the divided voltage is obtained as a drive signal via the buffer means.

In the second aspect of the invention, the divided voltage of the voltage input to the buffer means for outputting the drive signal is input via the constant voltage element.

In the third invention, the switching element is composed of a FET, the DC voltage of the voltage adding means is turned on and off by a transistor, and the buffer of the driving means is composed of a transistor.

In the fourth invention, a DC voltage is supplied to the gate of the FET of the switching element via a resistor, and a resistor is connected to the gate to supply a control voltage from the control voltage generating means.

[0011]

The switching element turns on / off the DC voltage by the control voltage generated by the control voltage generating means. The voltage adding means turns on / off the DC voltage based on the control voltage from the control voltage generating means and superimposes it on the control voltage.

The driving means for driving the voltage adding means is
The DC voltage is divided, the divided voltage is connected to the output of the control voltage generating means via the diode, and the divided voltage is driven to the voltage adding means via the buffer means. Further, the voltage input to the buffer means is input as a divided voltage via the constant voltage element.

Further, the switching element is constituted by an FET, the DC voltage of the voltage adding means is turned on / off by a transistor, and the buffer means is constituted by a transistor. In addition, a DC voltage is supplied to the gate of the FET of the switching element via a resistor,
Further, the control voltage from the control voltage generating means is supplied to the gate through the resistor.

As described above, since the on / off control of the DC voltage by the switching element is added to the control voltage from the control voltage generating means, the voltage obtained by turning on / off the DC voltage based on the control voltage is superimposed. The on / off characteristics of the switching element are improved, the loss is reduced, and the efficiency can be improved.

Further, the driving of the voltage adding means to be superimposed on the control voltage is divided into a DC voltage, the divided voltage is connected to the output of the control voltage generating means via a diode, and the divided voltage is buffered. The drive voltage can be easily obtained regardless of the DC voltage value.

Further, since the voltage input to the buffer is the divided voltage input via the constant voltage element,
It can be operated without being influenced by the fluctuation of the DC voltage. Further, since the switching element is constituted by the FET, the voltage adding means and the buffer are constituted by the transistor, a highly efficient switching power supply device can be constituted.

Further, since the DC voltage is connected to the gate of the FET through the resistor and the control voltage is supplied to the gate through the resistor, the ON / OFF operation of the FET can be efficiently performed.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram of an embodiment of the present invention. In FIG. 1, the power supply device 1, the FET 2, the control circuit 3, the coil 4, the capacitor 5, the diode 6, the resistors 7 to 9, and the load 1
0 is as described in FIG.

Further, 12 and 13 are transistors, 1
1 and 14 to 17 are resistors, 18 is a Zener diode,
19 is a diode. The operation in which the FET 2 is turned on / off by the control pulse output from the control circuit 3 and the converted voltage is supplied to the load 10 is as described in FIG. 3 of the conventional example.

As shown in FIG. 2A, when a pulse is sent from the control circuit 3, when the voltage is 0 V, a current flows through the diode 19 and the voltage divided by the resistors 16 and 17 is generated. Then, the transistor 13 is turned on and off as shown in FIG. The transistor 13 is shown in FIG.
When the transistor 12 is turned on and off as shown in FIG.
The on / off operation is performed as shown in (C), and a DC voltage is superimposed on the gate of the FET.

Therefore, as described with reference to FIG. 4, when the output from the control circuit 3 changes from 0V to + V, the transistor 12 is also turned on and the DC voltage is superimposed on the gate of the FET, and the input capacitance of the gate is discharged. Is performed via the transistor 12, a voltage with a fast rise is supplied, and the loss can be reduced.

In the embodiment, the switching element is F
Although ET is used, a transistor may be used. Further, although the divided voltage is supplied to the base of the transistor 13 via the Zener diode, a resistor may be used instead of the Zener diode, but the DC voltage changes by using the Zener diode. Can be surely performed.

[0023]

As described above, according to the present invention, the following effects can be obtained. Since the on / off control of the DC voltage by the switching element is added to the control voltage from the control voltage generating means and the voltage obtained by turning on / off the DC voltage based on the control voltage is superimposed, the on / off characteristics of the switching element are improved. The loss can be reduced and the efficiency can be improved.

Further, the driving of the voltage adding means to be superimposed on the control voltage is divided into a DC voltage, the divided voltage is connected to the output of the control voltage generating means through a diode, and the divided voltage is buffered. The drive voltage can be easily obtained regardless of the DC voltage value.

Further, since the voltage input to the buffer is input as the divided voltage via the constant voltage element,
It can be operated without being influenced by the fluctuation of the DC voltage. Further, since the switching element is constituted by the FET, the voltage adding means and the buffer are constituted by the transistor, a highly efficient switching power supply device can be constituted.

Further, since the DC voltage is connected to the gate of the FET through the resistor and the control voltage is supplied to the gate through the resistor, the ON / OFF operation of the FET can be efficiently performed.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is an operation explanatory diagram of the embodiment.

FIG. 3 is a configuration diagram of a conventional example.

FIG. 4 is an operation explanatory diagram of a conventional example.

[Explanation of symbols]

1 power supply 2 FET 3 control circuit 4 coils 5 capacitors 6,19 Diode 7-9, 11, 14-17 resistance 10 load 12, 13 transistors 18 Zener diode

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-153773 (JP, A) JP-A-4-150765 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H02M 3/155

Claims (4)

(57) [Claims] 1. A switching element for switching a DC voltage, a control voltage generating means for generating a control voltage for turning on / off the switching element according to an output voltage, and a DC voltage based on the control voltage from the control voltage generating means. and a voltage adding means for superimposing the control voltage by turning on and off the, driving for turning on and off a DC voltage of said voltage adding means
The operating means divides the DC voltage with a resistor and divides the divided voltage.
Connected to the output of the control voltage generator via a diode
And drive the divided voltage through the buffer means.
A switching power supply device characterized in that a signal is obtained . Wherein said voltage to be input to the buffer means for outputting a drive signal, the switching power supply unit of the divided voltage according to claim 1, characterized in that so as to input via the constant voltage element. Wherein the switching element FET, said voltage transistor on and off of the DC voltage of the adding means and the switching power supply device according to claim 1 or 2, characterized in that it has a transistor buffer of said drive means. 4. A DC voltage is supplied to the gate of the FET of the switching element via a resistor, and a resistor is connected to the gate to supply the control voltage from the control voltage generating means. The switching power supply device according to claim 3 .