JP2009194976A - Step-up switching power supply circuit of ringing choke type - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ringing choke switching power supply circuit that boosts the voltage generated by one solar battery cell as input voltage. <P>SOLUTION: When the charging voltage of a capacitor Cb exceeds an on-threshold voltage with a transistor Tr off, the transistor Tr is turned on and input voltage Vin is applied to primary winding Np on the primary side. As a result, voltage is produced in secondary winding Nb on the primary side and the transistor Tr is kept on by the combined voltage of this voltage and the charging voltage. As the transistor is continuously kept on, the charging voltage of the capacitor Cb drops and the transistor Tr is eventually turned off. At this time, induced voltage is produced in secondary winding Ns. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a ringing choke step-up switching power supply circuit that converts a DC low voltage to a DC high voltage, and is suitable for application to, for example, one solar battery cell as a power generator for generating the DC low voltage. The present invention relates to a ringing choke step-up switching power supply circuit.

  Conventionally, a boosting switching power supply circuit of a ringing choke method that uses a self-excited oscillation operation with a transformer and a transistor without using an external clock has been used.

  FIG. 7 is a circuit diagram of a general boosting switching power supply circuit 2 of a ringing choke method. In this step-up switching power supply circuit 2, a power generator 4 that generates an input voltage Vin is connected between input terminals 6 and 8, and a load 10 is connected between output terminals 12 and 14 that generate an output voltage Vo. .

  In the step-up switching power supply circuit 2, the transistor Tr is turned on when a current Ig flows through the resistor Rg to the base of the transistor Tr at the start. When the transistor Tr is turned on, the input voltage Vin is applied between the primary windings Np on the primary side.

  At this time, a constant current Ib (Ib = (Vnb−VBE) / Rb by an induced voltage Vin × Nb / Np = Vnb generated in the second winding Nb of the same polarity on the primary side via the transformer T, where VBE is a transistor Tr-base-emitter voltage) is supplied to the base of the transistor Tr. At this time, since the secondary winding Ns has a reverse polarity and the diode D is reverse biased, the secondary current Is does not flow.

  When the transistor Tr is ON, the primary current (collector current) Ic increases linearly, but the transistor Tr is turned OFF when the base current Ib becomes insufficient.

  When the transistor Tr is turned off, a back electromotive force generated in the first winding Np is induced in the secondary winding Ns with a voltage corresponding to the winding ratio (Ns / Np), and the diode D is turned on to turn on the secondary. The capacitor C2 is charged by the current Is, and the load 10 is supplied with the load current Io and the voltage Vo.

  When the induced voltage to the secondary winding Ns decreases and the diode D is turned off, power is supplied from the capacitor C2 to the load, and the counter electromotive force generated in the secondary winding Ns is converted to the winding ratio (Nb / Ns ) Is induced in the second winding Nb of the primary winding at a voltage corresponding to (), and the transistor Tr is turned on. Thereafter, the transistor Tr repeats ON and OFF operations.

  FIG. 8 shows a primary current Ic (current flowing through the primary first winding Np) and a secondary current Is (secondary winding) of the general ringing choke boost switching power supply circuit 2 shown in FIG. Each waveform of (current flowing through Ns) is shown.

  The switching cycle Tsw is composed of a transistor ON period Tr_on and a transistor OFF period Tr_off. During the transistor ON period Tr_on, the primary current Ic flows in the first winding Np of the transformer T, and energy is supplied to the first winding Np that is a reactor. Accumulated. The transistor ON period Tr_on is equal to the primary current conduction period TIc_on.

  On the other hand, the secondary current Is flows out from the secondary winding Ns of the transformer T during the transistor OFF period Tr_off, and the energy is completely discharged. The transistor OFF period Tr_off and the energization period of the secondary current Is (secondary current energization period) TIs_on are equal.

  By the way, when considering the use of, for example, one solar cell that generates a DC low voltage as the power generation device 4 of the step-up switching power supply circuit 2 of the ringing choke method, the OCV (open circuit voltage) of one solar cell is considered. : Open Circuit Voltage) is about 0.6 [V], and the ON threshold voltage of the transistor Tr is slightly lower than that.

  Therefore, when one solar cell is connected as the power generation device 4 of the step-up switching power supply circuit 2 of the ringing choke type shown in FIG. 7, the current Ig flows to the transistor Tr through the resistor Rg, and the transistor Tr is turned on. However, since the solar cell supplies the current Ig, the voltage drop due to the internal resistance of the solar cell causes the base voltage of the transistor Tr to fall below the ON threshold voltage of the transistor Tr. The disadvantage of not being able to do so occurs.

  In order to solve this problem, it is conceivable to employ SOI (Silicon On Insulator) technology that lowers the ON threshold voltage of a transistor (Patent Document 1).

Japanese Patent Laying-Open No. 2005-102440 ([0031], [0032])

  However, the SOI technology has a problem that the manufacturing process is complicated and the cost is high.

  The present invention has been made in consideration of such problems. Even in a power generation device that generates a low voltage such as one solar cell using an inexpensive transistor, switching is stably continued. It is an object of the present invention to provide a ringing choke type boosting switching power supply circuit that makes it possible.

  The ringing choke boosting switching power supply circuit according to the present invention includes a first winding and a second winding on the primary side to which the voltage generated by the power generator is applied as an input voltage. A transformer provided with an output winding to which a load is connected, a collector connected to the other end of the first winding to which a hot side of the input voltage is connected to one end, and an emitter connected to the input voltage A transistor connected to the cold side, a resistor connected between the hot side of the input voltage and the base of the transistor, the other end of the second winding having one end connected to the emitter, and the base And a capacitor connected between the two.

  In the present invention, a capacitor is connected between the hot side of the primary side second winding connected to the base of the transistor and the base, and the capacitor is connected between the hot side of the input voltage and the capacitor. It adopts the characteristic configuration of charging by. With this configuration, the capacitor is charged every switching cycle, and the transistor can be turned on by the charging voltage. Therefore, if the charging voltage is slightly higher than the ON threshold voltage of the transistor, the transistor is continued. It can be turned on.

  According to this invention, when the open circuit voltage of the power generator is a voltage that does not fall below the ON threshold voltage of the transistor, the transistor can be continuously turned on (continuously).

  The transistor is turned on when the voltage across the capacitor charged through the resistor exceeds the ON threshold voltage. When the transistor is turned on, the input voltage is applied between the primary side first windings. When the input voltage is applied between the secondary first windings, a voltage is induced in the primary secondary winding, and the induced second winding voltage is added to the voltage across the capacitor, The ringing choke including the transformer is configured such that the transformer is manufactured so that the voltage between the second windings becomes a voltage lower than the ON threshold voltage when the transistor further operates in the ON direction. The power loss of the step-up type switching power supply circuit can be suppressed.

  This invention can be applied suitably when the said electric power generation apparatus is one photovoltaic cell.

  According to the present invention, even in a power generation device that generates a low voltage, such as a single solar cell, a switching operation that can increase an output voltage higher than an input voltage using an inexpensive transistor can be stably performed. Can continue.

  Embodiments of the present invention will be described below with reference to the drawings. In the drawings to be referred to below, the same reference numerals are given to the components corresponding to those shown in FIGS.

  FIG. 1 is a circuit diagram of a ringing choke boosting switching power supply circuit 20 according to an embodiment of the present invention.

  In this step-up switching power supply circuit 20, a power generator 4 that generates an input voltage Vin is connected between primary input terminals 6 and 8, and a load 10 is a secondary output terminal that generates an output voltage Vo. 12 and 14 are connected.

  Although one solar cell is used as the power generation device 4 in this embodiment, the power generation device 4 is not limited to one solar cell.

  In order to convert the input voltage Vin, which is the primary voltage generated by the power generation device 4, into the output voltage Vo, which is the secondary voltage, the ringing choke boosting switching power supply circuit 20 according to this embodiment basically includes Includes a transistor Tr that is turned ON / OFF and one transformer T.

  In this embodiment, a bipolar NPN transistor is used as the transistor Tr. However, the transistor Tr is not limited to the bipolar transistor.

  A first winding Np and a second winding Nb are wound on the primary side of the core 22 of the transformer T, and an output winding Ns is wound on the secondary side of the transformer T.

  A rectifier circuit including a diode D and a smoothing capacitor C2 is connected to the output winding Ns. The output voltage Vo is obtained as a voltage across the smoothing capacitor C2.

  One end of the first winding Np on the primary side is connected to the hot side (current source side in this embodiment) of the power generating device 4 via the terminal 6, and the other end of the first winding Np is connected to the transistor Tr. Connected to the collector.

  A resistor Rg is connected between the base of the transistor Tr and the hot side of the power generator 4.

  The emitter of the transistor Tr is grounded and connected to the cold side (current sink side in this embodiment) of the power generation device 4 via the terminal 8.

  One end of the second winding Nb on the primary side is grounded. A series circuit of a resistor Rb and a capacitor Cb is connected between the other end of the second winding Nb on the primary side and a connection point between the base of the transistor Tr and the resistor Rg.

  The resistor Rb is a damping resistor (braking resistor), and has such a value that an excessive reverse voltage is not applied between the base and emitter of the transistor Tr due to a spike voltage generated on the hot side of the second winding Nb when the transistor Tr is turned on and off. (Small resistance value) is set. Since the resistance Rb has a small resistance value, in the following description, the voltage generated at both ends of the resistance Rb is described as 0 [V] in consideration of easy understanding. Further, since the resistor Rb is inserted for the purpose of reducing the spike voltage, a bead core or the like for reducing the frequency of the spike voltage (an element having a high resistance component at the spike voltage frequency and a zero resistance component in the direct current) It is also possible to substitute (in combination with a resistor).

FIG. 2 shows a change characteristic of the open-circuit voltage Vocv [V] with respect to the temperature of the power generation device 4 which is one solar battery cell according to this embodiment, and an ON threshold voltage Vth [V] between the base and emitter with respect to the temperature of the transistor Tr. The change characteristics are shown. The characteristics of the open circuit voltage Vocv of the power generation device 4 are the characteristics of the open circuit voltage Vocv2 when the solar radiation amount is 500 [W / m ² ] and the characteristics of the open circuit voltage Vocv1 when the solar radiation amount is 1000 [W / m ² ]. Is shown. It can be seen that at the same temperature, the open circuit voltage Vocv is higher when the amount of solar radiation is larger (Vovv1> Vovv2).

  In order to turn on the transistor Tr by the power generator 4 composed of one solar battery cell, the open circuit voltage Vocv needs to be a voltage that does not fall below the ON threshold voltage Vth of the transistor Tr (Vth). ≦ Vocv).

  For example, at a temperature of 40 [° C.], it can be read that the ON threshold voltage Vth of the transistor Tr is about 0.5 [V] and the open circuit voltage Vocv1 is about 0.55 [V]. Hereinafter, unless otherwise specified, the ON threshold voltage Vth of the transistor Tr is Vth = 0.5 [V], and the open-circuit voltage Vocv of the power generator 4 is Vocv = 0. It is assumed that the voltage is 55 [V].

  The ringing choke boosting switching power supply circuit 20 according to this embodiment is basically configured as described above, and the operation thereof will be described next.

  As shown in FIG. 3, when the transistor Tr is OFF and the diode D is OFF, the current Ig flows out from the power generation device 4, and the capacitor Cb passes through the path of the resistor Rg, the capacitor Cb, the resistor Rb, and the second winding Nb. The battery is gradually charged. During continuous oscillation (during self-excited oscillation), load current Io is supplied from capacitor C2 to load 10 when diode D is OFF.

  On the primary side, the current Ig flows from the power generation device 4 to the capacitor Cb, whereby the input voltage (generated voltage of the power generation device 4) Vin temporarily decreases due to a voltage drop due to the internal resistance of the power generation device 4. However, since the charging voltage Vcb increases as the capacitor Cb is gradually charged, the input voltage Vin approaches the open circuit voltage Vocv = 0.55 [V].

  Further, as the capacitor Cb is charged, the base voltage of the transistor Tr approaches the open circuit voltage Vocv = 0.55 [V], and the base voltage of the transistor Tr reaches the ON threshold voltage Vth = 0.5 [V]. Then, the transistor Tr is turned from OFF to ON.

  As shown in FIG. 4, when the transistor Tr is turned on, the input voltage Vin is applied between the primary windings Np, and energy is supplied to the first winding Np (which can be considered as a reactor). Accumulated.

  At this time, the voltage Vnb (Vnb = Vin × Nb / Np) is generated in the second winding Nb on the primary side via the transformer T, so that the voltage at the base of the transistor Tr rapidly increases.

  As a result, the base voltage of the transistor Tr becomes a combined voltage (Vcb + Vnb) of the charging voltage Vcb and the voltage Vnb, and the transistor Tr is further turned on.

  When the transistor Tr continues to be turned on, the charge of the capacitor Cb is consumed to turn on the transistor Tr, and the charge voltage Vcb is lowered.

  When the charging voltage Vcb decreases and the combined voltage (Vcb + Vnb) falls below the ON threshold voltage Vth of the transistor Tr, the transistor Tr is turned off.

  As shown in FIG. 5, when the transistor Tr is turned off, a back electromotive force Vin ′ is generated in the primary first winding Np, and the secondary winding Ns corresponds to the winding ratio (Ns / Np). A voltage Vns due to the electromotive force is induced.

  At this time, as shown in FIG. 5, the diode D is turned ON, the secondary current Is flows out from the secondary winding Ns, charges the capacitor C2, and supplies the load 10 with the load current Io at the voltage Vo. .

  When energy is released from the secondary winding Ns (which can be considered as a reactor), the operation returns to the first operation described with reference to FIG. 3, and the capacitor Cb starts to be charged again. Repeats (continues) self-oscillation operation.

  FIG. 6 shows a primary current Ic (current flowing in the primary side first winding Np) and a secondary current Is (in the secondary winding Ns) of the ringing choke type boosting switching power supply circuit 20 according to this embodiment. Each waveform of flowing current) is shown.

  The switching cycle Tsw includes a transistor ON period Tr_on between time points t0 and t1, and a transistor OFF period Tr_off between time points t1 and t3. The primary current Ic flows in the first winding Np of the transformer T during the transistor ON period Tr_on. Energy is stored in the first winding Np that is a reactor. The transistor ON period Tr_on is equal to the primary current conduction period TIc_on.

  On the other hand, the secondary current Is flows from the secondary winding Ns of the transformer T during the secondary current energization period TIs_on between the time points t1 and t2, which is the initial period of the transistor OFF period Tr_off, and energy is completely discharged.

  During the capacitor charging period Tch between time points t2 and t3, the capacitor Cb is charged with current Ig.

  Thus, in this embodiment, the transistor OFF period Tr_off and the secondary current energization period TIs_on are not equal as compared with the conventional technique shown in FIG.

  As described above, the ringing choke type boosting switching power supply circuit 20 according to this embodiment can be said to be a ringing choke type switching power supply circuit that boosts the voltage generated by one solar battery cell as the input voltage Vin.

  The ringing choke boosting switching power supply circuit 20 basically includes a first winding Np and a second winding Nb on the primary side to which power is supplied from the power generator 4 that generates the input voltage Vin. A transformer T provided with a winding Ns connected to the load 10 via a rectifier circuit on the secondary side, and a first winding in which the hot side (voltage generation side) of the input voltage Vin is connected to one end side. The transistor Tr is connected to the other end of the line Np, the emitter is connected to the cold side (ground side) of the input voltage Vin, and the resistor Rg is connected between the hot side of the input voltage Vin and the base of the transistor Tr. And a capacitor Cb connected between the other end of the second winding Nb connected to the grounded emitter of the transistor Tr and the base of the transistor Tr.

  Thus, the capacitor Cb is connected between the base side second winding Nb connected to the base of the transistor Tr and the base, and the capacitor Cb is connected to the hot side of the input voltage Vin and the capacitor Cb. A characteristic configuration in which charging is performed by a resistor Rg connected therebetween is employed. With this configuration, the capacitor Cb is charged in the capacitor charging period Tch every switching cycle Tsw shown in FIG. 6, and the transistor can be turned on by the charging voltage Vcb (see FIG. 3). If the voltage Vcb is slightly higher than the ON threshold voltage Vth of the transistor Tr, the transistor Tr can be continuously turned on.

  In other words, when the open voltage Vocv of the power generation device 4 is a voltage that does not fall below the ON threshold voltage Vth of the transistor Tr, the transistor Tr can be continuously turned on.

  That is, the ringing choke step-up switching power supply circuit 20 can be self-excited.

  The transistor Tr is turned on when the voltage Vcb across the capacitor Cb charged through the resistor Rg exceeds the ON threshold voltage Vth. However, when the transistor Tr is turned on, the input voltage Vin is applied between the primary side first windings Np. When the input voltage Vin is applied between the secondary side first winding Np, a voltage Vnb is generated in the primary side second winding Nb, and the generated voltage Vnb between the second windings becomes a voltage Vcb across the capacitor Cb. Ringing choke method including the transformer T by manufacturing the transformer T so that the second inter-winding voltage Vnb when the transistor Tr further operates in the ON direction by addition (Vnb + Vcb) is smaller than the ON threshold voltage Vth. The power loss of the step-up switching power supply circuit 20 can be suppressed.

  If the power generation device 4 is one solar battery cell, the present invention can be suitably applied. In practice, the solar cell was used with the step-up switching power supply circuit 20 of the ringing choke type in FIG. 1, and the operation could be confirmed in the range of −40 to +80 [° C.].

  As described above, according to the present invention, even with the power generation device 4 that generates a low voltage, such as one solar battery cell, switching can be stably continued using an inexpensive transistor Tr.

  In the above-described embodiment, an NPN bipolar transistor is used as the transistor Tr. However, based on the description in this specification, the transistor Tr can be changed to a PNP bipolar transistor, or the power generator 4 can be changed. Various configurations such as switching to a fuel cell instead of a solar cell, or using a MOSFET or IGBT instead of a bipolar transistor when these power generation devices 4 are connected in series are used. obtain.

1 is a circuit diagram of a ringing choke boosting switching power supply circuit according to an embodiment of the present invention. FIG. It is a characteristic view which shows the change characteristic of the open circuit voltage with respect to the temperature of the electric power generator which is one photovoltaic cell which concerns on this embodiment, and the change characteristic of ON threshold voltage with respect to the temperature of a transistor. It is explanatory drawing at the time of the charge which is a time of a transistor OFF. It is explanatory drawing of the state by which the transistor was turned ON and the input voltage was applied to the primary side 1st coil | winding. It is explanatory drawing which shows the state which the transistor turned off and the induced electromotive force generate | occur | produced in the secondary side coil | winding. It is each waveform diagram of the primary current and the secondary current of the step-up switching power supply circuit of the ringing choke system according to this embodiment. FIG. 2 is a circuit diagram of a general ringing choke boosting switching power supply circuit. FIG. 8 is a waveform diagram of a primary current and a secondary current of the general ringing choke type boosting switching power supply circuit shown in FIG. 7.

Explanation of symbols

2, 20 ... Ringing choke type step-up switching power supply circuit 4 ... Power generator 10 ... Load Cb ... Capacitor Nb ... Primary side second winding Np ... Primary side first winding Ns ... Secondary side winding ( (Secondary winding, output winding)
T ... Transformer Tr ... Transistors Rb, Rg ... Resistance Vin ... Input voltage Vo ... Output voltage

Claims (4)

A primary winding and a secondary winding are provided on the primary side to which the voltage generated by the power generator is applied as an input voltage, and an output winding to which a load is connected is provided on the secondary side. With a transformer,
A transistor having a collector connected to the other end of the first winding, the hot side of the input voltage connected to one end, and an emitter connected to the cold side of the input voltage;
A resistor connected between the hot side of the input voltage and the base of the transistor;
A capacitor connected between the other end of the second winding whose one end is connected to the emitter and the base;
A step-up switching power supply circuit using a ringing choke system. The step-up switching power supply circuit according to claim 1.
A ringing choke step-up switching power supply circuit characterized in that the open circuit voltage of the power generator is a voltage that does not fall below the ON threshold voltage of the transistor. The step-up switching power supply circuit according to claim 1 or 2,
The transistor is turned on when the voltage across the capacitor charged through the resistor exceeds the ON threshold voltage, but when turned on, the input voltage is applied between the primary side first winding, and the primary side When the input voltage is applied between the first windings, a voltage is induced in the primary side second winding, and the induced second winding voltage is added to the voltage across the capacitor, so that the transistor The ringing choke step-up switching power supply circuit is characterized in that the transformer is manufactured such that the voltage between the second windings is lower than the ON threshold voltage when operating in the ON direction. The step-up switching power supply circuit according to any one of claims 1 to 3,
The power generation device is one solar battery cell. A ringing choke type boosting switching power supply circuit.

Images