JPH02219461A - Booster type dc-dc converter provided with auxiliary coil - Google Patents

Abstract

PURPOSE:To produce voltage two times as high as the input voltage across a capacitor by connecting another boosting inductor, a diode, and a capacitor to the joint of a boosting inductor connected with a power source and a switch. CONSTITUTION:An boosting inductor L comprising a main coil N1 and an auxiliary coil N2 and a capacitor C are connected in series with a power source E, and a switching circuit Q is connected to the joint of the coils N1, N2. When the switch Q is turned ON, a diode D is biased reversely and energy is stored through the coil N1 in the coil N2 through transformer effect. When the switch Q is turned OFF, the coils N1, N2 function as a single inductor L and a voltage higher by such amount as corresponding to the coil N2 is produced then the voltage is rectified through the diode D in order to charge the capacitor C. Various output voltages can be produced by varying the operational duty of the switch Q and the winding ratio. By such arrangement, voltage two or more times higher than the input voltage can be produced stably.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a DC power conversion circuit, and particularly to a step-up DC-DC converter whose output power is higher than its input power.

[Prior Art] FIG. 3 is a circuit diagram showing the basic circuit configuration of a conventional step-up DC-DC converter.

In FIG. 3, an input power source E, an inductor LO, a switch Q, a rectifier diode D, a smoothing capacitor C, and a load resistor R are provided, and the output voltage thereof is ◯o.

In the conventional circuit described above, when the switch Q is on, power is supplied from the input power source E to the inductor LO, and the supplied power is stored in the inductor LO as excitation energy. After that, when the switch Q is turned off, the inductor LO is released, so a release voltage is generated in the inductor LO such that the junction between the switch Q and the inductor LO becomes positive, the rectifier diode D becomes conductive, and the smoothing capacitor A voltage that is the sum of the voltage of the input power source E and the open voltage of the inductor Lo is generated across C.

In this way, by periodically repeating on and off of the switch Q, the output voltage Vo, which is the voltage across the smoothing capacitor C, is supplied to the load resistor R.

FIG. 4 is a graph showing the output voltage characteristics of the conventional circuit.

In this FIG. 4, the on period T. n is the period during which the switch Q is on, and the switching period T is the period during which the switch Q repeats on and off. therefore,
The time during which the switch Q is off is the difference between T and T(Ill).The operating duty l1uty is the ratio of the on period "ran" to the switching period T (= T
On/T), and the maximum operating duty DIa
X is the value of the operating duty DutV that can generate a predetermined output voltage VO when the minimum load resistance among the plurality of load resistances R to be used is used.

In addition, in Fig. 4, the voltage of the input power supply E is 3■, and the load resistance R
4 shows the relationship between the operating duty Dutv and the output voltage vo in the cases where Ω is 40Ω and 100Ω, respectively.

[Problem 8 to be solved by the invention] In FIG. 4, in the range where the operating duty is around 0.5, the value of the output voltage VO is determined only by the operating duty, and the value of the output voltage vo is It is at most twice the input power source E. In addition, in a range where the operating duty is greater than 0.5, the output voltage Vo
increases rapidly as the operating duty l1uty increases, but it is affected by the load resistance H, and even with the same operating duty Dly, the smaller the load resistance R, the lower the output voltage VO
decreases.

Here, if the maximum output of the step-up DC-DC converter is 10V-2.5W (that is, the load resistance R is 40Ω or more), the maximum operating duty oaax is required to be 0.77 as shown in FIG. do. That is, in the conventional circuit, in order to obtain an output voltage o that is several times higher than the input power source E, it is necessary to set the maximum operating duty D□8 large.

However, since the switch Q requires sufficient switching time to turn on and off, if the operating duty ouLy becomes excessive, the switching time required for the switch Q to turn off is insufficient, and the switch Q cannot be turned off. It becomes possible.

In addition, the step-up DC-DC converter has a peak in the characteristics of the output voltage vo with respect to the operating duty, and when the operating duty DuLv increases beyond this peak, the output voltage V increases when the operating duty increases. There is a negative gain region where the gain decreases rapidly. If the converter is operated in this negative gain region, it will be impossible to reset the magnetic flux of the inductor Lo, so there is a risk that an excessive circuit current will flow and the components constituting the converter will burn out.

In addition, if the load resistance R changes, the operating duty 0LILV at which the negative gain region begins will change, and in addition to the load resistance R, parasitic elements such as the internal resistance of the switch Q and the forward drop voltage of the rectifier diode D will also cause Since the operational duty at which the negative gain region begins changes, it is difficult to intentionally set the operational duty at which the negative gain region begins.

In order to avoid the above problems, the maximum operating duty o
It is industrially safe to set aax to around 0.5, and most control circuits for conventional step-up DC-I)C converters limit the maximum operating duty naax to around 0.5.

Therefore, by limiting the maximum operating duty DlaX to around 0.5, the conventional step-up DC
-DC converter output voltage■. There is a problem in that a voltage up to approximately twice the input voltage E can only be obtained.

In the present invention, when the maximum operating duty is around 0.5,
It is an object of the present invention to provide a step-up DC-DC converter that can obtain a high output voltage that is twice or more that of the input power source.

[Means for Solving the Problems] The present invention provides a winding coil for the boost inductor between the boost inductor and the rectifier diode, connects the winding start of the winding coil to the winding end of the boost inductor, and connects the winding coil to the winding end of the boost inductor. A rectifier diode is connected at the end of the winding.

[Function] The present invention provides a step-up inductor winding coil between the step-up inductor and the rectifier diode, connects the winding start of the step-up inductor to the end of the step-up inductor, and connects the winding end of the step-up inductor to the rectifier. Since the diode is connected, when the maximum operating duty is around 0.5, the input power supply
It is possible to obtain a high output voltage that is more than twice as high.

[Example] FIG. 1 is a circuit diagram showing one embodiment of the present invention.

In this FIG. 1, an input power source E, a main coil Nl of an inductor L, and a switch Q are connected in series, and a winding coil N2 is connected between a connection point between the main coil N1 and the switch Q and a smoothing capacitor C. and a rectifier diode D are connected, a smoothing capacitor C smoothes the output voltage of the rectifier diode D, and output power is extracted from the smoothing capacitor C.

Note that the inductor L has a winding coil N1 connected to the main coil N1.
The main coil N1 corresponds to the step-up inductor Lo of the conventional circuit shown in FIG.

That is, in the above embodiment, the step-up inductor winding coil is provided between the step-up inductor and the rectifier diode, the winding start of the winding coil is connected to the winding end of the step-up inductor, and the rectifying coil is connected to the winding end of the step-up inductor. This is a diode connected.

Next, the operation of the above embodiment will be explained.

FIG. 2 shows the operating duty in the above embodiment.
FIG. 3 is a diagram showing the relationship between output voltage vo and output voltage vo.゛On period TOn, switching period T, operating duty Duty, and maximum operating duty 0 in FIG. is the same as that explained in the conventional example in Figure 4, and the operating conditions are that the input voltage E is 3■, and the load resistance R is 40Ω.
, 100Ω is also the same as in the case of the above-mentioned conventional example. In FIG. 2, the turn ratio between the winding coil N2 and the main coil N1 is 6.

First, the on period T of the switch Q. 0, the input power source E is connected to the main coil Nl of the inductor L, and due to the transformer effect, a voltage is generated in the winding coil N2 such that the beginning of the winding of the winding coil N2 is higher than the winding end of the winding coil N2. Since the beginning of the winding is at almost the same potential as the ground, the rectifier diode D is reverse biased and the diode D is turned off. As a result, the winding coil N2 becomes in a released state and is separated from the one-circuit operation. During the on-period Ton, power is supplied from the input power source E to the inductor via the main coil Nl, and is stored in the inductor L as excitation energy.

Next, when the switch Q is turned off, the main coil Nl is connected in series with the winding coil N2, so the main coil N1
The winding of one inductor L consisting of the winding coil N2 and the winding coil N2 is equivalent to an open throat. Therefore, the inductor L of the above embodiment is different from the step-up inductor L of the conventional circuit.
The number of turns of the winding coil N2 is larger than that of the coil N2, and a higher release voltage is generated across the inductor due to the larger number of turns, causing the rectifier diode D to conduct.

That is, when accumulating excitation energy in the inductor L, the main coil N1 is used, and when discharging the accumulated excitation energy, the main coil N1 and the winding coil N2 are used.

In the above embodiment, the fact that the output voltage ``o'' rapidly increases as the operating duty []uty increases is the same as in the conventional circuit. However, the above embodiment can obtain a high output voltage (2o) with a lower operating duty Dutv than the conventional circuit. Particularly, in the above embodiment, even though the operating duty is 0.5 or less, the output voltage is ■. is more than twice the input power E.

Therefore, in the above embodiment, compared to the conventional method in which several step-up converters with an operating duty of about 0.5 are connected in series to realize a high voltage, the number of converters connected in series can be reduced even with the same operating duty DLItV. The number of parts is reduced and efficiency is extremely high.

Furthermore, by adjusting the turns ratio between the main coil N1 and the winding coil N2, the starting point of the negative gain region with respect to the operating duty can be adjusted to an arbitrary operating duty.
It can be set to the value of y.

For example, when the turns ratio is increased, the starting point of the negative gain region moves to a lower operating duty. As described above, since the above embodiment is a circuit that sets the operating duty to an arbitrary value, the conventional control circuit for a boost converter can be used as is, and in particular, a new control method and control circuit components can be used. Not required, especially if the input power supply is 2
Since it is easy to obtain an output voltage of more than 10 cm at a low voltage of 3 V to 3 V, it is possible to construct a step-up power supply circuit using a battery as an input power source, for example, as a power source for analog electronic circuits that require a wide dynamic range. It is easy to carry and suitable for portable use.

Note that the limit value of the operating duty can be determined by setting the operating duty corresponding to the peak of the characteristic (shown in the second diagram) of the resistor with the lowest resistance value among the load resistors H used as the maximum operating duty oaax. Bye.

In other words, the circuit shown in Figure 1 shows the main parts of the converter, but in reality, it detects fluctuations in the output voltage V, applies the fluctuations to the control pole of the switch Q, and adjusts the output voltage. A negative feedback circuit is provided to keep the voltage vo constant. In this case, when the output voltage ■o decreases, the operating duty is increased to increase the output voltage vo, but if the operating duty D
When uty exceeds the maximum operating duty oaax, the output voltage Vo conversely decreases. In order to prevent this, when attempting to increase the output voltage (2)o, the operating duty Duty is made not to exceed the maximum duty n5ax.

[Effects of the Invention] According to the present invention, it is possible to obtain a high output voltage twice or more of the input power supply when the maximum operating duty is around 0.5.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing one embodiment of the present invention. FIG. 2 shows the operating duty in the above embodiment.
FIG. FIG. 3 is a circuit diagram showing an example of a conventional step-up DC-DC converter. FIG. 4 shows the operating duty in the above conventional example.
FIG. 3 is a diagram showing the relationship between the output voltage Vo and the output voltage Vo. Fig. 2 E... Input power supply, L... Inductor, LO... Boost inductor, Nl... Main coil (boost inductor), N2...
Winding coil, Q...switch, D...rectifier diode, R...load resistance. 0.2 0.4 0.6 0.8 Operation duty

Claims (1)

[Claims] An input power source, a step-up inductor, and a switch are connected in series, a rectifier diode is connected between a connection point between the step-up inductor and the switch, and a smoothing capacitor, and an output is generated from the smoothing capacitor. Step-up type DC-D that extracts electric power
In the C converter, between the boost inductor and the rectifier diode,
A booster with a winding coil, characterized in that a winding coil of the boosting inductor is provided, the winding start of the winding coil is connected to the winding end of the boosting inductor, and the rectifier diode is connected to the winding end of the winding coil. Type DC
-DC converter.