JPS642540Y2 - - Google Patents

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to a step-up type switching regulator.

[Background technology of the invention and its problems]

Conventionally, switching regulators have been widely used as small-sized, low-loss DC power supplies.

Incidentally, among such switching regulators, a step-up type switching regulator is generally constructed as shown in FIG. That is,
A capacitor 2 is connected between both ends of a DC power source 1, and an inductance element 3 and a transistor 4 as a switching element are connected between both ends of the capacitor 2.
are connected in series. And transistor 4
A protective diode 5 is connected between the collector and emitter of
A diode 6 and a capacitor 7 having the illustrated polarity are connected in series between both ends of the diode 5, and both ends of the capacitor 7 are connected to output terminals 8a and 8b. In addition, in the figure, 9 indicates a Zener diode connected between both ends of the capacitor 7 to prevent the voltage between the terminals of the capacitor 7 from exceeding an allowable level, and 10 indicates the impedance of the DC power supply 1. .

In this way, by applying a rectangular wave pulse train signal P between the base and emitter of the transistor 4, the output voltage from both ends of the capacitor 7, that is, between the output terminals 8a and 8b, is several times to several times the output voltage of the DC power supply 1. I'm trying to get 10 times the DC voltage. That is, when the pulse train signal P rises, the transistor 4 turns on, and current flows through the path from the capacitor 2 to the inductance element 3 to the transistor 4 to the capacitor 2 and the path via the DC power supply 1. When the pulse train signal P falls in such a state, the transistor 4 is rapidly turned off, and the current flowing through the inductance element 3 is accordingly rapidly reduced. Now, assuming that the inductance value of the inductance element 3 is L and the current reduction rate is di/dt, an overvoltage with the illustrated polarity of v _L =Ldi/dt is generated across the inductance element 3. This voltage v _L is applied to the capacitor 7 via the diode 6. Therefore, the capacitor 7 will be charged to a voltage much higher than the output voltage of the DC power supply 1. Note that the capacitor 2 increases the level of current flowing through the inductance element 3 and effectively reduces di/
Served to increase dt.

However, the conventional switching regulator configured as described above lacks effective use of the energy generated in the inductance element 3, and as a result, the time required to charge the capacitor 7 is relatively long. There was a problem. That is, if we consider the phenomenon at the time when the transistor 4 is turned off, at this time a voltage v _L of the illustrated polarity is generated in the inductance element 3 as described above. this voltage
v _L is applied to the series circuit of capacitor 7 and capacitor 2. Now, let the capacitance of capacitor 7 be C ₇ ,
If the capacitance of capacitor 2 is C ₂ and C ₂ > C ₇ , then the voltage generated in inductance element 3 is
Most of v _L will be applied to both ends of capacitor 7. In this state, a voltage of opposite polarity is applied to the diode 5, so the diode 5 can be regarded as a capacitor having a junction capacitance _C5 . Therefore, inductance element 3
A part of the energy generated in is stored in the diode 5, and this stored energy is
When the voltage between the two is v, it becomes 1/2C ₅ v ² . The energy stored in the junction capacitance _C5 is then released through the path from the junction capacitance _C5 to the inductance element 3 to the capacitor 2 to the junction capacitance _C5 . in this case,
From the moment when the voltage between A and B is about to reverse, the circuit switches to a circuit in which the junction capacitance _C5 does not exist. Therefore, the energy previously stored in the junction capacitor C ₅ is used to charge the capacitor 2 . Here, since the capacitance C 2 of the capacitor ₂ and the junction capacitance C ₅ have a relationship of C ₂ ≫ _{C 5} , the junction capacitance C ₅
Even if all of the energy stored in capacitor 2 is transferred to capacitor 2, the terminal voltage of capacitor 2 hardly changes. Therefore, as shown in FIG. 2, the voltage between A and B is such that every time the transistor 4 turns off, only one high voltage pulse with a peak value v is generated superimposed on the output voltage E of the DC voltage 1. becomes. That is,
This means that the energy stored in the junction capacitance C ₅ does not contribute to charging the capacitor 7 at all. Therefore, there was a problem in that it took a long time to charge the capacitor 7.

[Purpose of invention]

The present invention was developed in view of these circumstances, and its purpose is to use the energy stored in the junction capacitance and stray capacitance of a protective diode connected to both ends of a semiconductor switching element for charging purposes. It is an object of the present invention to provide a step-up type switching regulator that can be used and shorten charging time.

[Summary of the idea]

The switching regulator according to the present invention is characterized in that a diode is connected in the forward direction between the inductance element and the switching element.

[Effect of idea]

With the above configuration, the effective value of the charging high voltage applied to the output capacitor can be increased for reasons described later. That is, the output capacitor can be charged by effectively utilizing the energy stored in the junction capacitance and stray capacitance of the protection diode. Therefore, the charging time can be shortened compared to the conventional one.

[Example of idea]

The details of this invention will be explained below with reference to illustrated embodiments.

FIG. 3 shows a step-up type switching regulator according to an embodiment of the present invention.
The same parts as in FIG. 1 are designated by the same reference numerals. Therefore, the explanation of the overlapping parts will be omitted.

In this embodiment, the inductance element 3
A diode 11 is connected in the forward direction between and the collector of the transistor 4, and the connection point between the diode 11 and the inductance element 3 is connected to the anode of the diode 6.

With such a configuration, when the pulse train signal P falls and the transistor 4 is turned off, a voltage of v _L =Ldi/dt is generated across the inductance element 3 with the illustrated polarity. This voltage v _L is applied to the series circuit of capacitor 7 and capacitor 2 through diode 6. Now, assuming that the capacitance C ₇ of capacitor 7 is much smaller than the capacitance C ₂ of capacitor 2,
Most of the voltage v _L is applied to the capacitor 7.
Now, let the voltage of the capacitor 7 at this time be v.
When a voltage of v is applied in this way, since the diode 11 is in the forward direction and the diode 5 is in the opposite direction with respect to this voltage, the junction capacitance C ₅ of the diode 5 is charged with the voltage of v. That is, the junction capacitance C ₅
can store 1/2C ₅ v ² of energy. Next, the energy stored in the junction capacitance C ₅ is released into a vibrating circuit consisting of the junction capacitance C ₅ , the junction capacitance C ₁₁ of the diode 11 , the inductance element 3 , the capacitor 2 , and the junction capacitance C ₅ . In this case, C ₅ ≒
Assuming C ₁₁ , the capacitor 2 is smaller than C ₅ and C ₁₁ .
capacity is much larger. Therefore, from a circuit perspective, it is equivalent to capacitor 2 being short-circuited. Therefore, the energy stored in the junction capacitance C ₅ is substantially released through the path from the junction capacitance C ₅ to the junction capacitance C ₁₁ to the inductance element 3 to the junction capacitance C ₅ , and the junction capacitances C ₅ and C ₁₁ are It is charged to the polarity shown every other time.
Therefore, as shown in FIG. 4, the voltage between C and B will undergo damped free oscillation for a while after the transistor 4 is turned off. As can be seen from this waveform, a plurality of forward half waves appear for the diode 6. Further, due to the presence of the diode 11, the off time of the transistor 4 is shortened, and as a result, the current change rate becomes large and the peak value of the first wave overvoltage becomes higher than that of the conventional one. Therefore,
Since these half waves contribute to the charging of the capacitor 7, the effective value of the voltage applied to the capacitor 7 can be increased compared to the conventional case, and the charging time can be shortened accordingly.

FIG. 5 shows another embodiment of the present invention,
The same parts as in FIG. 3 are indicated by the same reference numerals.

This embodiment differs from the previous embodiment in that the cathode of diode 11 is connected to the anode of diode 6.

With such a configuration, the voltage applied to the capacitor 7 due to the rectification action of the diode 11,
In other words, the voltage between D and B in the figure has the waveform shown in FIG. In this case, the peak value v' is lowered by the voltage shared by the diode 11 compared to the embodiment shown in FIG. However, the effective value of the voltage applied to the capacitor 7 is larger than in the conventional case. Therefore, the same effects as in the embodiment described above can be obtained.

Although stray capacitance was not mentioned in the description of each of the above-mentioned embodiments, since stray capacitance always exists in an actual circuit, the energy stored in this capacitance can also be effectively used in the present invention.

[Brief explanation of the drawing]

Figure 1 is a block diagram of a conventional step-up switching regulator, Figure 2 is a diagram showing the output waveform of the high voltage generator of the same regulator, and Figure 3 is a diagram of a switching regulator according to an embodiment of the present invention. FIG. 4 is a diagram showing the output waveform of the high voltage generator in the regulator, FIG. 5 is a diagram showing the configuration of a switching regulator according to another embodiment of the present invention, and FIG. It is a figure which shows the output waveform of the high voltage generation part in the same regulator. 1... DC power supply, 2, 7... Capacitor, 3...
...Inductance element, 4...Transistor,
5, 6, 11...diode.

Claims (1)

[Scope of utility model registration request] A step-up type switch in which an inductance element and a semiconductor switching element are connected in series between both ends of a capacitor that is charged by a DC power supply, and a protective diode is connected in opposite polarity between both ends of the semiconductor switching element. 1. A switching regulator, characterized in that a diode is inserted in a forward direction between the inductance element and the semiconductor switching element.