JP7386737B2 - Rectifier circuit and switching power supply using the same - Google Patents

Description

The invention disclosed herein relates to a rectifier circuit and a switching power supply using the same.

FIG. 15 is a diagram showing a conventional example of a switching power supply. In the switching power supply 100 of this conventional example, when the pulse voltage output from the half-bridge drive circuit 120 is applied to the primary winding L1 of the transformer 110 via the coil 150, the pulse voltage is applied to the secondary winding L2a of the transformer 110. An induced voltage of At this time, in the rectifier circuit 130, the current rectified by the diode D11 is accumulated in the capacitor C11.

On the other hand, when a pulse voltage having a phase opposite to that described above is output from the half-bridge drive circuit 120, an induced voltage having a phase opposite to that described above is generated in the secondary winding L2b. At this time, in the rectifier circuit 130, the current rectified by the diode D12 is accumulated in the capacitor C11.

By repeating the above series of operations, the rectifier circuit 130 can perform full-wave rectification (bidirectional rectification) of the induced pulse voltages generated in each of the secondary windings L2a and L2b.

In addition, as an example of the prior art related to the above, Patent Document 1 and Patent Document 2 can be cited.

JP 2019-9989 Publication Patent No. 5007966 specification

By the way, the conventional rectifier circuit 130 requires a transformer 110 (=center-tapped transformer) including secondary windings L2a and L2b with mutually different winding directions in order to realize the full-wave rectifying operation.

However, when one of the secondary windings L2a and L2b is performing a rectifying operation, the other does not contribute to the rectifying operation at all, so the winding utilization rate of the transformer 110 is low, and the transformer 110 There was a problem in that it led to an increase in size (which in turn led to an increase in heat generation due to a decrease in the degree of bonding).

In view of the above problems discovered by the inventors of the present application, the invention disclosed herein provides a rectifier circuit that can increase the winding utilization rate of a transformer and a switching power supply using the same. The purpose is to

For example, the rectifier circuit disclosed herein includes a first rectifier that rectifies the positive induced voltage generated in the secondary winding of a transformer, and a first rectifier that rectifies the negative induced voltage generated in the secondary winding. It is set as the structure (1st structure) which has the 2nd rectifier which rectifies|straightens, and the inductance part connected between the said 1st rectifier and the said 2nd rectifier.

In the rectifier circuit having the first configuration, the inductance section may preferably include an auxiliary winding coupled to the primary winding of the transformer (second configuration).

In the rectifier circuit having a second configuration, the degree of coupling between the primary winding and the auxiliary winding is smaller than the degree of coupling between the primary winding and the secondary winding (third configuration). It's good to do that.

In the rectifier circuit having the second or third configuration, it is preferable that the inductance section further includes a connection coil that limits the short-circuit current flowing through the auxiliary winding (fourth configuration).

In the rectifier circuit having the fourth configuration, the connection coil may be a balance coil whose center tap is connected to the output end of the output voltage (fifth configuration).

Furthermore, in the rectifier circuit having the first configuration, the inductance portion may include a connection coil that is not coupled to the primary winding of the transformer (sixth configuration).

In the rectifier circuit having any of the first to sixth configurations, the first rectifier section has a first end connected to the first end of the secondary winding, and a second end connected to the first end of the inductance section. a first rectifying element connected to the inductor, and a first capacitor having a first end connected to the first end of the inductance section and a second end connected to the second end of the secondary winding, The second rectifying section includes a second rectifying element whose first end is connected to the second end of the secondary winding and whose second end is connected to the second end of the inductance section; A configuration (seventh configuration) including a second capacitor connected to the second end of the inductance section and whose second end is connected to the first end of the secondary winding is preferable.

The rectifier circuit having a seventh configuration further includes a third capacitor connected in series between the secondary winding, the first rectifying section, and the second rectifying section (eighth configuration). good.

In the rectifier circuit having a fourth configuration, the first rectifier includes a first rectifier element whose first end is connected to the first end of the secondary winding, and a first rectifier element whose first end is connected to the first rectifier element. a first capacitor connected to a second end of the element and having a second end connected to a second end of the secondary winding, the second rectifier having a first end connected to the second end of the secondary winding; a second rectifying element connected to a second end of the second rectifying element, and a second rectifying element having a first end connected to a second end of the second rectifying element and a second end connected to a first end of the secondary winding. a capacitor, a first end of the connection coil is connected to a second end of the first rectifying element and a first end of the first capacitor, and a second end of the connection coil is connected to the auxiliary coil. The second end of the auxiliary winding is connected to the second end of the second rectifying element and the first end of the second capacitor (a ninth configuration).

In the rectifier circuit having a fifth configuration, the first rectifier includes a first rectifier element whose first end is connected to the first end of the secondary winding, and a first rectifier element whose first end is connected to the first rectifier element. a first capacitor connected to a second end of the element and having a second end connected to a second end of the secondary winding, the second rectifier having a first end connected to the second end of the secondary winding; a second rectifying element connected to a second end of the second rectifying element, and a second rectifying element having a first end connected to a second end of the second rectifying element and a second end connected to a first end of the secondary winding. a capacitor, a first end of the balance coil is connected to a second end of the first rectifying element and a first end of the first capacitor, and a second end of the balance coil is connected to the auxiliary capacitor. The second end of the auxiliary winding is connected to the second end of the second rectifying element and the first end of the second capacitor, and the second end of the auxiliary winding is connected to the second end of the second rectifying element and the first end of the second capacitor. The midpoint tap is connected to an output end of the output voltage together with a first end of an output smoothing capacitor, and a second end of the secondary winding is connected to a second end of the output smoothing capacitor. configuration (tenth configuration).

Further, for example, the rectifier circuit disclosed in this specification includes a pair of rectifier elements connected in series in opposite directions between both ends of a secondary winding of a transformer, and a rectifier circuit connected in parallel to the pair of rectifier elements. The present invention has a configuration (eleventh configuration) including a balance coil and a rectifier coil connected to a center tap of the balance coil.

The rectifier circuit having the eleventh configuration may further include a capacitor that DC-blocks the closed circuit formed by the secondary winding and the balance coil (twelfth configuration).

Further, for example, the switching power supply disclosed in this specification includes a transformer, a drive circuit for switching and driving the primary winding of the transformer, and any one of the first to twelfth structures described above, This configuration includes a rectifier circuit connected to the next winding (a thirteenth configuration).

According to the invention disclosed in this specification, it is possible to provide a rectifier circuit that can increase the winding utilization rate of a transformer and a switching power supply using the rectifier circuit.

A diagram showing a first embodiment of a switching power supply A diagram showing a second embodiment of the switching power supply A diagram showing a third embodiment of a switching power supply A diagram showing a fourth embodiment of the switching power supply A diagram showing a fifth embodiment of the switching power supply A diagram showing a sixth embodiment of the switching power supply A diagram showing a seventh embodiment of the switching power supply A diagram showing an eighth embodiment of a switching power supply A diagram showing a ninth embodiment of a switching power supply A diagram showing a tenth embodiment of a switching power supply A diagram showing an eleventh embodiment of a switching power supply A diagram showing a twelfth embodiment of a switching power supply A diagram showing a thirteenth embodiment of a switching power supply A diagram showing a fourteenth embodiment of a switching power supply Diagram showing a conventional example of a switching power supply

<First embodiment>
FIG. 1 is a diagram showing a first embodiment of a switching power supply. The switching power supply 1 of the first embodiment converts the input voltage Vin supplied from the DC power supply E1 into the output voltage Vout and supplies it to the load Z while electrically insulating the primary circuit system and the secondary circuit system. This is an isolated type DC/DC converter for supplying power, and includes a transformer 10, a half-bridge drive circuit 20, a rectifier circuit 30, a control circuit 40, a coil 50, and capacitors 61 and 62.

The transformer 10 includes a primary winding L1 provided in a primary circuit system, and a secondary winding L2 provided in a secondary circuit system and magnetically coupled to the primary winding L1.

The half-bridge drive circuit 20 includes an upper switch and a lower switch (both of which are connected in series between the positive end (=the application end of the input voltage Vin) and the negative end (=the ground of the primary circuit system) of the DC power supply E1. (not shown), and switches and drives the primary winding L1 of the transformer 10 in response to instructions from the control circuit 40.

The rectifying circuit 30 includes a first rectifying section 31, a second rectifying section 32, and an inductance section 33, and generates an output voltage Vout by full-wave rectifying the induced voltage generated in the secondary winding L2 of the transformer 10.

The first rectifier 31 includes a diode D1 and a capacitor C1, and rectifies the positive induced voltage generated in the secondary winding L2 of the transformer 10. The anode of the diode D1 is connected to the first end (=winding start end) of the secondary winding L2. The cathode of the diode D1 and the first end of the capacitor C1 are both connected to the output end of the output voltage Vout (=high potential end of the load Z) and the first end of the inductance section 33 (=the winding end of the auxiliary winding L3). has been done. The second end of the capacitor C1 is connected to the second end (=winding end) of the secondary winding L2 and the low potential end of the load Z.

The second rectifier 32 includes a diode D2 and a capacitor C2, and rectifies the negative induced voltage generated in the secondary winding L2 of the transformer 10. The anode of the diode D2 is connected to the second end (=winding end) of the secondary winding L2 and the low potential end of the load Z. The cathode of the diode D2 and the first end of the capacitor C2 are both connected to the second end of the inductance section 33 (=the winding start end of the auxiliary winding L3). The second end of the capacitor C2 is connected to the first end (=winding start end) of the secondary winding L2.

Note that the diodes D1 and D2 are each connected to a synchronous rectifier circuit (for example, a switching element such as a MOSFET) that is turned on/off in synchronization with the half-bridge drive circuit 20 by the control circuit 40, or a voltage across the respective terminals or It may be replaced with a switch element that is turned on/off by detecting the current flowing through the switch.

Inductance section 33 includes an auxiliary winding L3. The auxiliary winding L3 is connected between the first rectifier 31 (=the connection node between the diode D1 and the capacitor C1) and the second rectifier 32 (=the connection node between the diode D2 and the capacitor C2). It is magnetically coupled to the primary winding L1 of the transformer 10. Further, the auxiliary winding L3 is wound so that its own induced voltage is equal to the induced voltage of the secondary winding L2. However, the degree of coupling between the primary winding L1 and the auxiliary winding L3 is smaller than the degree of coupling between the primary winding L1 and the secondary winding L2.

The control circuit 40 has, for example, a function (=output feedback control function) of controlling the half-bridge drive circuit 20 so that the output voltage Vout matches a desired target value. By providing such a function, it becomes possible to stably supply a constant output voltage Vout to the load Z.

The coil 50 is connected between the output end of the half-bridge drive circuit 20 (=the connection node between the upper switch and the lower switch) and the first end of the primary winding L1, and functions as a resonant coil.

Capacitor 61 is connected in parallel to DC power supply E1, and functions as an input filter capacitor that removes noise components from input voltage Vin.

The capacitor 62 is connected between the second end of the primary winding L1 and the negative end of the DC power supply E1 (=ground of the primary circuit system), and functions as a resonant capacitor.

Although not clearly shown in this figure, the switching power supply 1 preferably has a startup circuit that precharges the capacitors C1 and C2 at startup.

Next, the operation of the switching power supply 1 will be explained. When the DC power source E1 is turned on, the input voltage Vin is applied to the capacitor 61 and the half-bridge drive circuit 20. When a pulse voltage is applied from the half-bridge drive circuit 20 to the primary winding L1 of the transformer 10 via the coil 50, a pulse-like induced voltage is also generated in the secondary winding L2.

For example, when a positive induced voltage is generated in the secondary winding L2, charge is accumulated in the capacitor C1 via the diode D1. On the other hand, when a negative induced voltage is generated in the secondary winding L2, charge is accumulated in the capacitor C1 via the diode D2.

By repeating the above series of operations, the rectifier circuit 30 can perform full-wave rectification (bidirectional rectification) of the pulse-like induced voltage generated in the secondary winding L2.

Further, the same (or almost the same) induced voltage as that of the secondary winding L2 is generated in the auxiliary winding L3. Therefore, capacitors C1 and C2 connected via auxiliary winding L3 are both charged to the same potential. That is, when a pulse-like induced voltage is generated at the first end of one of the capacitors C1 and C2, an induced voltage with the same waveform is also generated at the other first end. Therefore, basically no short circuit pulse current flows through the auxiliary winding L3.

In addition, the auxiliary winding L3 has a smaller degree of coupling with the primary winding L1 than the secondary winding L2, and has a smaller current (for example, RMS value 1/2 or less) than the secondary current flowing through the secondary winding L2. Therefore, it is sufficient to make the cross-sectional area smaller (thinner wire diameter) than the secondary winding L2. This prevents the transformer 10 from becoming unnecessarily large.

With the rectifier circuit 30 having the above configuration, both positive and negative induced voltages can be full-wave rectified without requiring a center-tapped transformer, regardless of the direction of the current flowing through the secondary winding L2. Unlike a center-tapped transformer that requires two secondary windings of the same thickness, for the transformer 10 connected to the rectifier circuit 30, it is sufficient to wind one secondary winding L2, so the transformer 10 This makes it possible to increase the winding utilization rate. Therefore, the cross-sectional area of the secondary winding L2 can be increased (the wire diameter is increased) without increasing the size of the transformer 10 (and thus decreasing the degree of coupling), so that the heat generated by the transformer 10 (=√ 2RI ² , where R is the resistance value of the secondary winding L2 and I is the current value of the secondary current).

Further, since the surge component can be released through the auxiliary winding L3, it is also possible to design the withstand voltage of each of the diodes D1 and D2 to the minimum necessary.

<Second embodiment>
FIG. 2 is a diagram showing a second embodiment of the switching power supply. The switching power supply 1 of the second embodiment is based on the first embodiment (FIG. 1), but the configuration of the inductance section 33 is modified.

More specifically, the inductance section 33 further includes a connection coil L4 that limits the short-circuit pulse current flowing through the auxiliary winding L3.

In addition, in this figure, the connection coil L4 is connected between the second rectifier 32 (=the connection node between the diode D2 and the capacitor C2) and the second end of the auxiliary winding L3, but the connection of the connection coil L4 is The position is not limited to this, and the connection coil L4 is connected between the first rectifier 31 (=connection node between the diode D1 and the capacitor C1) and the first end of the auxiliary winding L3. You may.

According to the present embodiment, even if the induced voltages generated in the secondary winding L2 and the auxiliary winding L3 are different, the short-circuit pulse current caused by the voltage difference is limited, and heat generation in the transformer 10 is suppressed. becomes possible.

<Third embodiment>
FIG. 3 is a diagram showing a third embodiment of the switching power supply. The switching power supply 1 of the third embodiment is based on the second embodiment (FIG. 2), but the configuration of the inductance section 33 is modified.

To be more specific, the inductance section 33 includes a balance coil L5 whose center tap is connected to the output end of the output voltage Vout, as the previously mentioned connection coil L4. Further, the connection node between the diode D1 and the capacitor C1 is separated from the output end of the output voltage Vout. Furthermore, a capacitor 63 is connected in parallel to the load Z.

According to this embodiment, it is possible to improve the stability of output feedback control.

<Fourth embodiment>
FIG. 4 is a diagram showing a fourth embodiment of the switching power supply. The switching power supply 1 of the fourth embodiment is based on the third embodiment (FIG. 3), but the configuration of the rectifier circuit 30 is modified.

To be more specific, the rectifier circuit 30 connects the first end (=winding start end) of the secondary winding L2, the first rectifier 31 and the second rectifier 32 (=the connection between the diode D1 and the capacitor C2). It further includes a capacitor 34 connected between the node and the node.

According to the present embodiment, even if the positive and negative induced voltages generated in the secondary winding L2 vary, the variations are canceled and the secondary currents flowing through each of the first rectifying section 31 and the second rectifying section 32 are reduced. It becomes possible to match.

Note that although this figure is based on the third embodiment (FIG. 3), it may also be based on the first embodiment (FIG. 1) or the second embodiment (FIG. 2).

<Fifth embodiment>
FIG. 5 is a diagram showing a fifth embodiment of the switching power supply. The switching power supply 1 of the fifth embodiment is based on the third embodiment (FIG. 3), but the configuration of the rectifier circuit 30 is modified.

To be more specific, the rectifier circuit 30 connects the second end (=end of the winding) of the secondary winding L2, the first rectifier 31 and the second rectifier 32 (=the connection between the diode D2 and the capacitor C1). It further includes a capacitor 35 connected between the node and the node.

According to the present embodiment, as in the fourth embodiment (FIG. 4) described earlier, even if both the positive and negative induced voltages generated in the secondary winding L2 vary, the variations are canceled and the first rectifier It becomes possible to match the secondary currents flowing through each of the rectifier 31 and the second rectifier 32.

Note that although this figure is based on the third embodiment (FIG. 3), it may also be based on the first embodiment (FIG. 1) or the second embodiment (FIG. 2).

<Sixth embodiment>
FIG. 6 is a diagram showing a sixth embodiment of the switching power supply. A switching power supply 1 according to the sixth embodiment is based on the third embodiment (FIG. 3), but an AC power supply E2 is connected instead of the DC power supply E1.

That is, the switching power supply 1 converts the input voltage Vin supplied from the AC power supply E2 into an output voltage Vout and supplies it to the load Z while electrically insulating the primary circuit system and the secondary circuit system. It is said to be a type of AC/DC converter.

In this way, in order to operate the switching power supply 1 with the AC power supply E2, the half-bridge drive circuit 20 may be made compatible with the input voltage Vin in both positive and negative directions.

Note that this figure is based on the third embodiment (FIG. 3), but also includes the first embodiment (FIG. 1), the second embodiment (FIG. 2), the fourth embodiment (FIG. 4), and the third embodiment (FIG. 3). Any of the five embodiments (FIG. 5) may be used as the basis.

<Seventh embodiment>
FIG. 7 is a diagram showing a seventh embodiment of the switching power supply. The switching power supply 1 of the seventh embodiment is based on the sixth embodiment (FIG. 6), but the primary circuit system is mainly changed.

To be more specific, the switching power supply 1 includes a capacitor 64, a bidirectional switch 70, and a driver 81 in place of the half-bridge drive circuit 20, coil 50, and capacitor 62 described earlier as components of the primary circuit system. and 82, and a current detection element 90. Further, a capacitor 65 is added to the secondary circuit system of the switching power supply 1.

Note that among the above components, the bidirectional switch 70 and the drivers 81 and 82 correspond to a drive circuit that switches and drives the primary winding L1 of the transformer 10.

Capacitor 64 is connected in parallel to bidirectional switch 70 and functions as a resonant capacitor.

Bidirectional switch 70 includes switch elements 71 and 72 that are reversely connected in series between AC power source E2 and primary winding L1.

For example, when the switch elements 71 and 72 are Si-based or SiC-based NMOSFETs [N-channel type metal oxide semiconductor field effect transistors], the respective sources S of the switch elements 71 and 72 are common, and the drain D of the switch element 71 is is connected to the AC power source E2, and the drain D of the switch element 72 is connected to the primary winding L1. Note that as the switch elements 71 and 72, GaN devices, IGBTs (insulated gate bipolar transistors), or the like may be used, respectively.

Further, the switch elements 71 and 72 are associated with internal diodes 73 and 74 and internal capacitances 75 and 76, respectively. In the case of this figure, the cathode of the internal diode 73 and the first end of the internal capacitance 75 are connected to the drain D of the switch element 71. Further, the anode of the internal diode 73 and the second end of the internal capacitance 75 are connected to the source S of the switch element 71. On the other hand, the cathode of the internal diode 74 and the first end of the internal capacitance 76 are connected to the drain D of the switch element 72. Further, the anode of the internal diode 74 and the second end of the internal capacitance 76 are connected to the source S of the switch element 72.

Drivers 81 and 82 generate drive signals (gate signals) for switch elements 71 and 72, respectively, in response to instructions from control circuit 40.

For example, the control circuit 40 has a function (=output feedback control function) of turning on/off the bidirectional switch 70 so that the DC output voltage Vout matches a desired target value. By providing such a function, it becomes possible to stably supply a constant output voltage Vout to the load Z. As for the output feedback control method, existing pulse width modulation method, criticality method, etc. may be applied.

Further, the control circuit 40 has a function of turning on/off the bidirectional switch 70 so that the power factor of the switching power supply 1 approaches 1 (=power factor improvement function). By providing such a function, a separate power factor correction circuit is not required, so it is possible to realize a one-converter type switching power supply 1.

The control circuit 40 also monitors a current sense signal (=signal corresponding to the primary current) obtained using the current detection element 90 (for example, a sense resistor) to prevent the primary current from exceeding a predetermined upper limit value. It has a function of turning on/off the bidirectional switch 70 (=constant current control function). By providing such a function, an excessive primary current does not flow through the primary circuit system, so that the safety of the switching power supply 1 can be improved.

In addition, current feedback control using the current detection element 90 allows harmonic current control in addition to power factor improvement and overcurrent protection.

Additionally, the control circuit 40 has a function (which monitors the voltage across the bidirectional switch 70 (and by extension, the voltage across the capacitor 64) and turns on the bidirectional switch 20 at the timing when the voltage value becomes 0V. = ZVS [zero-volt switching] function). By providing such a function, the switching loss of the bidirectional switch 70 can be reduced, so that the conversion efficiency of the switching power supply 1 can be increased.

Alternatively, the control circuit 40 may have a function of individually controlling zero voltage switching of the switch elements 71 and 72 (=individual ZVS function). By providing such a function, the switching loss of the bidirectional switch 70 can be further reduced, so it is possible to suppress the heat generation of the bidirectional switch 70 and further increase the conversion efficiency of the switching power supply 1. Become.

The basic operation of the switching power supply 1 having the above configuration will be explained. When the control circuit 40 turns on the bidirectional switch 70 (=both switch elements 71 and 72), a primary current flows through the primary winding L1 of the transformer 10, and energy is stored. Then, when a predetermined amount of energy is accumulated in the transformer 10, the bidirectional switch 70 is turned off.

For example, when the switch voltage Vsw appearing at the connection node between the primary winding L1 and the bidirectional switch 70 is a positive potential, the switch element 72 is turned off from the control circuit 40 via the driver 82. At this time, the energy stored in the transformer 10 is used to charge the internal capacitance 76 of the switch element 72, the internal capacitances (not shown) of the diodes D1 and D2, and the capacitors 64 and 65. Also, at this time, the energy output from the secondary winding L2 is rectified by the diode D1, stored in the capacitor C1, and further output to the capacitor 63 via the center tap of the balance coil L5.

On the other hand, when the switch voltage Vsw is a negative potential, the switch element 71 is turned off from the control circuit 40 via the driver 81. At this time, the energy stored in the transformer 10 is used to charge the internal capacitance 75 of the switch element 71, the internal capacitances (not shown) of the diodes D1 and D2, and the capacitors 64 and 65. Also, at this time, the energy output from the secondary winding L2 is rectified by the diode D2, stored in the capacitor C2, and further output to the capacitor 63 via the center tap of the balance coil L5.

Note that the capacitors C1 and C2 are connected via the inductance section 33 (=auxiliary winding L3 and balance coil L5), but as mentioned earlier, the secondary winding L2 and the auxiliary winding L3 are connected to each other. Since the induced voltages are designed to be equal to each other, no short-circuit current flows through the inductance section 33.

Thereafter, when the energy of the transformer 10 is completely discharged into the capacitor 63, the bidirectional switch 70 is turned on again at an appropriate timing, and the above series of operations is repeated.

In this way, the rectifier circuit 30 described above can also be applied to the switching power supply 1 that uses the bidirectional switch 70 to drive the primary winding L1.

<Eighth embodiment>
FIG. 8 is a diagram showing an eighth embodiment of the switching power supply. The switching power supply 1 of the eighth embodiment is based on the seventh embodiment (FIG. 7), but a changeover switch SW for changing the number of turns of the primary winding L1 is added.

The changeover switch SW has a common node connected to the application end of the input voltage Vin, a first selection node connected to the first end of the primary winding L1, and a second selection node connected to the inside of the primary winding L1. Connected to the dot tap. Therefore, the changeover switch SW can switch which of the first end and the center tap of the primary winding L1 the input voltage Vin is applied to.

For example, in an application where a relatively high input voltage Vin (for example, Vin=AC220V) is input, it is preferable to conduct the common node of the changeover switch SW and the first selection node. At this time, the turns ratio between the primary winding L1 and the secondary winding L2 is n1:n2 (where n1 is the number of turns from the first end to the second end of the primary winding L1, and n2 is the number of turns of the secondary winding L1). (number of turns from the first end to the second end of L2).

On the other hand, in applications where a relatively low input voltage Vin (for example, Vin=AC100V) is input, it is preferable to conduct the common node of the changeover switch SW and the second selection node. At this time, the turns ratio between the primary winding L1 and the secondary winding L2 is n1':n2 (where n1' is the number of turns from the midpoint tap to the second end of the primary winding L1, and n1> n1').

In this way, by switching the number of turns of the primary winding L1 according to the input voltage Vin, the on time (or switching frequency) of the bidirectional switch 70 is difficult to change even if the input voltage Vin changes.

Therefore, when dealing with various input voltages Vin (so-called multi-power supply support), it is possible to standardize the control circuit 40 (=controller IC) and downsize the transformer 10 and peripheral components, making it easy to use with universal specifications. It becomes possible to provide the switching power supply 1 at low cost.

Further, in the switching power supply 1 of this embodiment, the higher the input voltage Vin is, the more the number of turns of the primary winding L1 can be increased to increase the inductance L. Therefore, the higher the input voltage Vin is, the higher the Q value [quality factor] (=√(L/C)) of the resonant waveform appearing in the voltage across the bidirectional switch 70 becomes, making the ZVS operation easier.

Note that as the changeover switch SW, a manual switch may be used, or an electric switch such as a relay may be used. When adopting the former, it is desirable to use a transformer 10 that includes a changeover switch SW (=a transformer with a tap changer). On the other hand, when adopting the latter, it is desirable to have a configuration in which the input voltage Vin is detected and the changeover switch SW is automatically switched.

<Ninth embodiment>
FIG. 9 is a diagram showing a ninth embodiment of the switching power supply. The switching power supply 1 of the ninth embodiment is based on the first embodiment (FIG. 1), but the configuration of the inductance section 33 is modified.

More specifically, the inductance section 22 includes a connection coil L6 that is not magnetically coupled to the primary winding L1 of the transformer 10, instead of the auxiliary winding L3. The first end of the connection coil L6 is connected to the first rectifier 31 (=the connection node between the diode D1 and the capacitor C1). The second end of the connection coil L6 is connected to the second rectifier 32 (=the connection node between the diode D2 and the capacitor C2).

Capacitors C1 and C2 connected via connecting coil L6 are both charged to the same potential. Therefore, basically no short circuit pulse current flows through the connecting coil L6. In this way, magnetic coupling between the inductance section 33 and the primary winding L1 is not essential.

<Tenth embodiment>
FIG. 10 is a diagram showing a tenth embodiment of the switching power supply. The switching power supply 1 of the tenth embodiment converts the input voltage Vin supplied from the DC power supply E1 into the output voltage Vout and supplies it to the load Z while electrically insulating the primary circuit system and the secondary circuit system. This is an isolated DC/DC converter for supplying power, and includes a transformer 10, half-bridge drive circuits 21 and 22, a rectifier circuit 30, a control circuit 40, and capacitors 61, 66, and 67.

The transformer 10 includes a primary winding L1 provided in a primary circuit system, and a secondary winding L2 provided in a secondary circuit system and magnetically coupled to the primary winding L1. Note that the first end of the primary winding L1 is connected to the output end of the half-bridge drive circuit 21 via a capacitor 66. On the other hand, the second end of the primary winding L1 is connected to the output end of the half-bridge drive circuit 22.

The half-bridge drive circuits 21 and 22 each include an upper switch and a lower switch connected in series between the positive end (=the application end of the input voltage Vin) and the negative end (=the ground of the primary circuit system) of the DC power supply E1. It includes a switch (none of which is shown), and drives the primary winding L1 of the transformer 10 by switching in response to an instruction from the control circuit 40. Note that the half-bridge drive circuits 21 and 22 can also be understood as one full-bridge drive circuit.

The rectifier circuit 30 includes diodes 36 and 37, a balance coil 38, and a rectifier coil 39, and generates an output voltage Vout by full-wave rectification of the induced voltage generated in the secondary winding L2 of the transformer 10. .

The cathode of the diode 36 is connected to the first end (=winding start end) of the secondary winding L2. The cathode of the diode 37 is connected to the second end (=winding end) of the secondary winding L2. The anodes of the diodes 36 and 37 are both connected to the ground of the secondary circuit system (=low potential end of the load Z). The diodes 36 and 37 connected in this manner correspond to a pair of rectifying elements connected in series in opposite directions between both ends of the secondary winding L2.

The balance coil 38 is connected in parallel to the pair of rectifying elements. More specifically, the first end (=winding start end) of the balance coil 38 is connected to the cathode of the diode 36. The second end (=winding end) of the balance coil 38 is connected to the cathode of the diode 37.

A first end of the rectifier coil 39 is connected to a center tap of the balance coil 38. The second end of the rectifier coil 39 is connected to the output end of the output voltage Vout.

The control circuit 40 has, for example, a function (=output feedback control function) of controlling the half-bridge drive circuits 21 and 22 so that the output voltage Vout matches a desired target value. By providing such a function, it becomes possible to stably supply a constant output voltage Vout to the load Z. As for the output feedback control method, an existing pulse width modulation method, frequency modulation method, phase modulation method, etc. may be applied.

Capacitor 61 is connected in parallel to DC power supply E1, and functions as an input filter capacitor that removes noise components from input voltage Vin.

Capacitor 66 is connected between the output end of half-bridge drive circuit 21 and the first end of primary winding L1, and functions as a resonant capacitor. When the capacitance value of the capacitor 66 is large relative to the operating frequency of each of the half-bridge drive circuits 21 and 22, it may be simply called a capacitor.

The capacitor 67 is connected in parallel to the load Z and functions as an output capacitor that smoothes the output voltage Vout.

Although not explicitly shown in this figure, the switching power supply 1 preferably has a startup circuit that precharges the capacitor 67 at startup.

Next, the operation of the switching power supply 1 will be explained. When the DC power supply E1 is turned on, the input voltage Vin is applied to the capacitor 61 and the half-bridge drive circuits 21 and 22. When a pulse voltage is applied to the primary winding L1 of the transformer 10 using the half-bridge drive circuits 21 and 22, a pulse-like induced voltage is also generated in the secondary winding L2.

For example, when a positive induced voltage is generated in the secondary winding L2, charges are accumulated in the capacitor 67 via the diode 37, the balance coil 38, and the rectifier coil 39. On the other hand, when a negative induced voltage is generated in the secondary winding L2, charges are accumulated in the capacitor 67 via the diode 36, the balance coil 38, and the rectifier coil 39.

By repeating the above series of operations, the rectifier circuit 30 can perform full-wave rectification (bidirectional rectification) of the pulse-like induced voltage generated in the secondary winding L2.

In this figure, the primary circuit system has a full-bridge configuration, but the primary circuit system may have a half-bridge configuration (such as in the first embodiment). It is also optional to operate as a resonant power supply circuit by adding a transformer leakage inductance or a resonant coil.

<Eleventh embodiment>
FIG. 11 is a diagram showing an eleventh embodiment of the switching power supply. A switching power supply 1 according to the eleventh embodiment is based on the tenth embodiment (FIG. 10), but an AC power supply E2 is connected instead of the DC power supply E1.

That is, the switching power supply 1 converts the input voltage Vin supplied from the AC power supply E2 into an output voltage Vout and supplies it to the load Z while electrically insulating the primary circuit system and the secondary circuit system. It is said to be a type of AC/DC converter.

In this way, in order to operate the switching power supply 1 with the AC power supply E2, the half-bridge drive circuits 21 and 22 may be made to correspond to the positive and negative input voltages Vin, respectively.

Further, a current detection element 91 is provided between the half-bridge drive circuits 21 and 22 and the AC power supply E2. Therefore, the control circuit 40 can perform power factor improvement and overcurrent protection, as well as control of harmonic currents, by current feedback control using the current detection element 91.

<Twelfth embodiment>
FIG. 12 is a diagram showing a twelfth embodiment of the switching power supply. The switching power supply 1 of the twelfth embodiment is based on the tenth embodiment (FIG. 10), but a capacitor 68 is added. The capacitor 68 may be provided on a closed circuit formed by the secondary winding L2 and the balance coil 38 (for example, between the second end of the secondary winding L2 and the second end of the balance coil 38). With this configuration, the capacitor 38 can be used to block the closed circuit in terms of direct current, so it is possible to prevent direct current from flowing in the closed circuit.

<13th embodiment>
FIG. 13 is a diagram showing a thirteenth embodiment of the switching power supply. The switching power supply 1 of the thirteenth embodiment combines the primary circuit system of the eighth embodiment (FIG. 8) and the secondary circuit system of the second embodiment (FIG. 2), and the connection position of the connection coil L4 is has been changed.

To be more specific, the connection coil L4 is connected not between the second rectification section 32 (=the connection node between the diode D2 and the capacitor C2) and the second end of the auxiliary winding L3, but between the first rectification section 31 and the second end of the auxiliary winding L3. (=connection node between diode D1 and capacitor C1) and the first end of auxiliary winding L3.

According to the present embodiment, even if the induced voltages generated in the secondary winding L2 and the auxiliary winding L3 are different, the short-circuit pulse current caused by the voltage difference is limited, and heat generation in the transformer 10 is suppressed. becomes possible. This point is similar to the second embodiment (FIG. 2).

Note that when considering the basic circuit when AC is applied, both the changeover switch SW of the primary circuit system and the connection coil L4 of the secondary circuit system can be omitted. Considering this, the combination of the primary circuit system of the seventh embodiment (Fig. 7) and the secondary circuit system of the first embodiment (Fig. 2) is the simplest, and this combination is the basic circuit when applying AC. It can be understood as a circuit.

<Fourteenth embodiment>
FIG. 14 is a diagram showing a fourteenth embodiment of the switching power supply. The switching power supply 1 of the fourteenth embodiment is based on the eighth embodiment (FIG. 8), but the connection position of the balance coil L5 is changed.

To be more specific, the balance coil L5 is located not between the second rectifier 32 (=the connection node between the diode D2 and the capacitor C2) and the second end of the auxiliary winding L3, but between the first rectifier 31 and the second end of the auxiliary winding L3. (=connection node between diode D1 and capacitor C1) and the first end of auxiliary winding L3. The technical significance thereof will be explained below.

First, consider a case where the balance coil L5 is connected between the second rectifier 32 and the second end of the auxiliary winding L3 (corresponding to the eighth embodiment (FIG. 8)). In this case, the potential of the first end (=terminal connected to the second rectifier 32) of the balance coil L5 fluctuates greatly. This is because the connection node between the diode D2 and the capacitor C2 is not connected to the capacitor 63 (=output smoothing capacitor), so the potential fluctuates greatly. On the other hand, since the center tap of the balance coil L5 is connected to the capacitor 63, the potential fluctuation is relatively small. Therefore, the potential of the second end of the balance coil L5 (=the terminal connected to the second end of the auxiliary winding L3) fluctuates greatly, similar to the first end of the balance coil L5.

In this way, when the balance coil L5 is connected between the second rectifier 32 and the second end of the auxiliary winding L3, the potentials of the first and second ends of the balance coil L5 are large. Because of the fluctuation, a coil with large inductance must be used to prevent the balance coil L5 from becoming saturated.

Next, consider a case where the balance coil L5 is connected between the first rectifier 31 and the first end of the auxiliary winding L3 (corresponding to the thirteenth embodiment (FIG. 13)). In this case, the first end (=the terminal connected to the first rectifier 32) of the balance coil L5 has relatively small fluctuation in potential. This is because, from a high frequency perspective, the potential appearing at the connection node between the diode D1 and the capacitor C1 is equal to the potential appearing at the second end of the secondary winding L2 through the capacitor C1; This is because the end is connected to the capacitor 63 (=output smoothing capacitor), so the potential fluctuation is relatively small. Further, since the center tap of the balance coil L5 is also connected to the capacitor 63, fluctuations in potential are relatively small. Therefore, the second end of the balance coil L5 (=the terminal connected to the first end of the auxiliary winding L3) has a relatively small potential fluctuation, like the first end of the balance coil L5.

In this way, when the balance coil L5 is connected between the first rectifier 31 and the first end of the auxiliary winding L3, fluctuations in the potentials of the first and second ends of the balance coil L5 occur. Since is relatively small, there is no need to consider the saturation of the balance coil L5, and a coil with small inductance can be used.

<Other variations>
Note that the various technical features disclosed in this specification can be modified in addition to the above-described embodiments without departing from the gist of the technical creation. That is, the above embodiments should be considered to be illustrative in all respects and not restrictive, and the technical scope of the present invention is not limited to the above embodiments, and the claims Ranges and equivalents should be understood to include all changes falling within the range.

The rectifier circuit disclosed herein can be used, for example, as a secondary rectifier used in an isolated switching power supply.

1 switching power supply 10 transformer 20, 21, 22 half bridge drive circuit 30 rectifier circuit 31 first rectifier 32 second rectifier 33 inductance section 34, 35 capacitor 36, 37 diode 38 balance coil 39 rectifier coil 40 control circuit 50 coil 61 , 62, 63, 64, 65, 66, 67, 68 capacitor 70 bidirectional switch 71, 72 switch element 73, 74 internal diode 75, 76 internal capacitance 81, 82 driver 90, 91 current detection element C1, C2 capacitor D1, D2 Diode E1 DC power supply E2 AC power supply L1 Primary winding L2 Secondary winding L3 Auxiliary winding L4 Connection coil L5 Balance coil L6 Connection coil SW Changeover switch Z Load

Claims (10)

a first rectifier that rectifies the positive induced voltage generated in the secondary winding of the transformer;
a second rectifier that rectifies the negative induced voltage generated in the secondary winding;
an inductance section connected between the first rectification section and the second rectification section;
has
A rectifier circuit , wherein the inductance section includes an auxiliary winding coupled to a primary winding of the transformer . The rectifier circuit according to claim 1 , wherein the degree of coupling between the primary winding and the auxiliary winding is smaller than the degree of coupling between the primary winding and the secondary winding. The rectifier circuit according to claim 1 or 2, wherein the inductance section further includes a connection coil that limits a short circuit current flowing through the auxiliary winding. 4. The rectifier circuit according to claim 3, wherein the connection coil is a balance coil whose center tap is connected to the output end of the output voltage. The first rectifying section includes a first rectifying element having a first end connected to the first end of the secondary winding and a second end connected to the first end of the inductance section; a first capacitor connected to a first end of the inductance section and a second end connected to the second end of the secondary winding; a second rectifying element connected to a second end of the wire and having a second end connected to the second end of the inductance section; a first rectifying element connected to the second end of the inductance section; 5. The rectifier circuit according to claim 1, further comprising a second capacitor connected to the first end of the secondary winding. a first rectifier that rectifies the positive induced voltage generated in the secondary winding of the transformer;
a second rectifier that rectifies the negative induced voltage generated in the secondary winding;
an inductance section connected between the first rectification section and the second rectification section;
has
The first rectifying section includes a first rectifying element having a first end connected to the first end of the secondary winding and a second end connected to the first end of the inductance section; a first capacitor connected to a first end of the inductance section and a second end connected to the second end of the secondary winding; a second rectifying element connected to a second end of the wire and having a second end connected to the second end of the inductance section; a first rectifying element connected to the second end of the inductance section; a second capacitor connected to a first end of the secondary winding . The rectifier circuit according to claim 5 or 6, further comprising a third capacitor connected in series between the secondary winding, the first rectifier, and the second rectifier. The first rectifying section includes a first rectifying element having a first end connected to a first end of the secondary winding, and a second rectifying element having a first end connected to a second end of the first rectifying element. a first capacitor connected to a second end of the secondary winding;
The second rectifying section includes a second rectifying element having a first end connected to a second end of the secondary winding, and a second rectifying element having a first end connected to a second end of the second rectifying element. a second capacitor connected to the first end of the secondary winding;
A first end of the connection coil is connected to a second end of the first rectifying element and a first end of the first capacitor, and a second end of the connection coil is connected to a first end of the auxiliary winding. 4. The rectifier circuit according to claim 3 , wherein the second end of the auxiliary winding is connected to the second end of the second rectifying element and the first end of the second capacitor. The first rectifying section includes a first rectifying element having a first end connected to a first end of the secondary winding, and a second rectifying element having a first end connected to a second end of the first rectifying element. a first capacitor connected to a second end of the secondary winding;
The second rectifying section includes a second rectifying element having a first end connected to a second end of the secondary winding, and a second rectifying element having a first end connected to a second end of the second rectifying element. a second capacitor connected to the first end of the secondary winding;
A first end of the balance coil is connected to a second end of the first rectifying element and a first end of the first capacitor, and a second end of the balance coil is connected to the first end of the auxiliary winding. The second end of the auxiliary winding is connected to the second end of the second rectifying element and the first end of the second capacitor, and the center tap of the balance coil is connected to 5. The secondary winding is connected to the output end of the output voltage along with a first end of an output smoothing capacitor, and a second end of the secondary winding is connected to a second end of the output smoothing capacitor. rectifier circuit. transformer and
a drive circuit that switches and drives the primary winding of the transformer;
The rectifier circuit according to any one of claims 1 to 9 , which is connected to a secondary winding of the transformer;
A switching power supply.

Images