JPH0697837B2 - DC-DC converter - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC-DC converter, and more particularly to a DC-DC converter capable of increasing its boosting efficiency when obtaining a high voltage output from a low voltage input. .

[Conventional technology]

Conventionally, in this type of DC-DC converter, as shown in FIG. 2, by interrupting the current flowing through the load L, surge energy generated at both ends of the load L at the moment when the current of the load L is interrupted is eliminated. It is used to obtain a constant high voltage output from a low voltage input. And this load L
The period of intermittently flowing the current is determined by the time when the current flowing through the load L reaches a constant value and the oscillation frequency of the internal oscillation circuit.

[Problems to be Solved by the Invention]

However, in this conventional method, the oscillation frequency is always constant regardless of the magnitude of the surge energy generated at both ends of the load L. Therefore, when the surge energy is large, before all the energy is discharged to the output side. In addition, since the current again flows through the load L, there is a problem that the efficiency of the energy obtained as the output is poor.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a DC-DC converter that can reduce surge energy loss and perform boosting with high efficiency.

[Means for Solving the Problems]

In order to achieve the above object, in the present invention, in the DC-DC converter, the input voltage of the DC power supply is boosted by utilizing the surge energy generated by the interruption of the coil to obtain an output voltage higher than the input voltage, The potential of the coil is detected, and the first switching means that is turned on while surge energy is generated at both ends of the coil is compared with the potential of the first switching means and the reference potential. A comparing means that is in an on state when the first switching means is in an on state; and a comparing means that is connected in series with the coil and that is in an off state when the comparing means is in an on state to stop energization of the coil. 2 switching means, and when the generation of surge energy at both ends of the coil is completed, the first switching means is turned off. Then, the comparison means is turned off and the second switching means is turned on to start energizing the coil.

[Action]

In the DC-DC converter configured as described above,
While surge energy is generated at both ends of the coil,
The first switching means is turned on, the comparison means is turned on, the second switching means is turned off, and the power supply to the coil is stopped. After that, when the generation of surge energy at both ends of the coil ends,
The first switching means is turned off, the comparison means is turned off, the second switching means is turned on, and power supply to the coil is started.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. First
The figure is an electric circuit diagram showing this embodiment. In FIG. 1, reference numeral 1 is a power supply bypass diode, 2 is a power supply diode, and when boosting is not required, that is, when the input voltage is higher than the output voltage, the current is bypassed through the diode 1 and the coil 27, 28 is not powered. 3 is a capacitor for smoothing the input power supply voltage. Reference numeral 4 is a power supply protection resistor for the comparator, 5 is a power supply smoothing capacitor for the comparator, and power is supplied to the comparators 10 and 13 by the resistor 4 and the capacitor 5. The resistors 6, 8 and 9 and the Zener diode 7 constitute a constant voltage circuit. The constant voltage of the Zener diode 7 is divided by the resistors 8 and 9, and the voltage is divided into non-inverting input terminals 10a of the comparators 10 and 13. Connected to 13a respectively. The comparator 10 cuts the current flowing through the coils 27 and 28 by a constant amount. The comparator 13 controls the voltage generated at the output end to a constant voltage. The resistors 11 and 12 give the comparator 13 hysteresis. Resistors 14, 15, 17 and transistor 16 and diode 18
Constitutes a switching circuit as a first switching means, and the transistor 16 is turned on while the surge energy is generated at the point 28a. The diode 18 is for preventing reverse bias of the transistor 16.
The output voltage divided by resistors 19 and 30 is
It is connected to the inverting input terminal 13b of and serves as a reference voltage for controlling the output voltage value. Resistors 21, 22, 25 and transistor 23 and resistor 26
The transistor 24 constitutes a switching circuit as a second switching means, and by turning on / off this circuit, the currents of the coils 27 and 28 are intermittently connected and generated, and surge energy is generated at a point 28a. Resistor 26 is for current detection, resistor 20
It is connected to the inverting input terminal 10b of the comparator 10 via. 27 and 28 are surge energy generating coils. The diode 29 is for preventing the reverse flow of the boosted voltage, and the capacitor 32 is for accumulating and smoothing the output voltage. The Zener diode 31 is for preventing excessive boosting output, and forcibly stops the boosting operation when excessive boosting is performed due to a circuit failure or the like and an overvoltage is output. The resistor 33 is an output load resistor.

Next, the operation of the present embodiment having the above structure will be described.

When power is supplied to the input terminal side and it is higher than a certain voltage that does not require boosting, that is, when the input voltage is higher than the output voltage, the forward voltage drop of the diode 1 from the input voltage is applied to the output terminal side. The voltage minus is output. On the other hand, when the input voltage is low and does not reach the output voltage to be obtained, the following boosting operation is performed. First, the comparator 10,1
3 is an open collector output, both of which are off when voltage is input. Therefore, the transistors 23 and 24 are turned on, current flows through the coils 27 and 28, a voltage drop occurs in the resistor 26, and the voltage value divided by the resistor 20 is applied to the inverting input terminal 10b of the comparator 10. The voltage drop of the resistor 26 rises transiently, and when it exceeds the voltage value of the non-inverting input terminal 10a of the comparator 10 set to a constant value in advance, the comparator 10 turns on, the output terminal of the comparator becomes Lo level, and the transistor 23 and 24 turn off.
When the transistor 24 is turned off, positive surge energy is generated at the point 28a due to the nature of the coils 27 and 28,
Through the diode 29, consumed by the load or the capacitor 32
Accumulated in. Especially when surge energy is generated, the transistor 16 turns on, and the inverting input terminal 10b of the comparator 10
To the Hi level and the potential becomes higher than the non-inverting input terminal 10a, forcibly turn on the comparator 10 during this period,
Transistor 24 is off. When all the surge energy is released, the transistor 16 turns off and the comparator 10 turns off accordingly. As a result, the transistors 23 and 24 are turned on again, and current flows through the coils 27 and 28. After that, this series of operations is repeated to boost the voltage.

Incidentally, the Zener diode 31 is for the purpose of preventing an excessively high output voltage for the sake of safety, which prevents an abnormally high voltage from being generated even if the circuit fails, and the output voltage becomes equal to or higher than the Zener voltage due to the circuit failure. At this time, the oscillation is stopped by making the inverting input of the comparator 10 higher than the non-inverting input.

As described above, according to the present embodiment, the energization of the coil is forcibly stopped by the first and second switching means while the surge energy is being generated, so that all the surge energy is output. There is no problem that an electric current flows through the coil before the end of the discharge and the energy loss occurs. In addition, the comparator 13 has a resistor 1
When the divided voltage by 9,30 exceeds the voltage specified by resistors 8 and 9, the voltage is controlled by shutting off the circuit and stopping the energy release, so there is no abnormal high voltage. .

In the above embodiment, a transistor is used as the first switching means for turning on the output of the comparator 10 during the generation of surge energy. However, the present invention is not limited to this, and a comparator circuit for determining the presence or absence of surge energy may be used. It may be. Further, in FIG. 1, the transistor may be replaced with a FET, and the comparator 10,
Alternatively, 13 may be composed of a transistor and a FET.

〔The invention's effect〕

As described above, according to the present invention, there is an excellent effect that the loss of surge energy can be reduced and highly efficient boosting can be performed.

[Brief description of drawings]

FIG. 1 is an electric circuit diagram showing an embodiment of the present invention, and FIG. 2 is a diagram showing a conventional DC-DC converter. 10,13 …… Comparator, 14,15,17 …… Resistance, 16 …… Transistor, 18 …… Diode, 19,20 …… Resistance, 23,24 ……
Transistor, 27, 28 ... Coil.

Claims (1)

[Claims] 1. A DC-DC converter for boosting an input voltage of a DC power supply by utilizing surge energy generated by the intermittent coil to obtain an output voltage higher than the input voltage, by detecting the potential of the coil. , The first switching means is turned on while surge energy is generated at both ends of the coil, and the potential of the first switching means is compared with the reference potential to compare the first switching means with each other. A comparison unit that is in an ON state when in an ON state; and a second switching unit that is connected in series with the coil and that is in an OFF state when the comparison unit is in an ON state and stops energization to the coil; When the generation of surge energy at both ends of the coil is completed, the first switching means is turned off and the comparison means is turned off. , The second switching means is turned on, DC-DC converter, characterized in that to start the energization of the coil.