Electrical power converter

Abstract

Electrical power converter, featuring: a choke coil (15, 25, 35, 45, 55); a main switch (11, 22, 31, 32, 41, 51) which connects a power supply to the choke coil (15, 25, 35, 45, 55) by being switched on, and supplies current from the power supply to the choke coil (15, 25, 35, 45, 55) in order to store energy in the choke coil (15, 25, 35, 45, 55); a synchronous rectifying switch (12, 21, 32, 31, 42, 52) which connects the inductor (15, 25, 35, 45, 55) to a load by being switched on for a period during which the main switch (11, 22, 31, 32, 41, 51) is switched off, and releases the energy stored in the inductor (15, 25, 35, 45, 55) to supply current from the inductor (15, 25, 35, 45, 55) to the load; and a control circuit (17, 27, 37, 47, 57) which is connected to the main switch (11, 22, 31, 32, 41, 51) and the synchronous rectifier switch (12, 21, 32, 31, 42, 52), and controls the main switch (11, 22, 31, 32, 41, 51) and the synchronous rectifier switch (12, 21, 32, 31, 42, 52); wherein The control circuit (17, 27, 37, 47, 57) detects a switching transition time indicating a transition state of a cross-connection voltage of the main switch (11, 22, 31, 32, 41, 51) and controls the main switch (11, 22, 31, 32, 41, 51) and the synchronous rectifier switch (12, 21, 32, 31, 42, 52) based on the detected switching transition time, wherein The control circuit (17, 27, 37, 47, 57) controls the main switch (11, 22, 31, 32, 41, 51) and the synchronous rectifier switch based on a target output voltage value, an output voltage, and a deviation of a target switching transition time value from the actual switching transition time, and The control circuit (17, 27, 37, 47, 57) corrects the ON time ratio, which is obtained based on an input voltage and an output voltage, by means of an ON time ratio correction value, which is obtained based on the deviation of the target switching transition time value from the actual switching transition time, and controls the main switch (11, 22, 31, 32, 41, 51) and the synchronous rectifier switch based on the corrected ON time ratio.

Description

BACKGROUND OF THE INVENTION Technical field of the invention

[0001] The present invention relates to an electrical power converter comprising a reactor, a main switch and a synchronous rectification switch. DESCRIPTION OF RELATED TECHNOLOGY

[0002] As a generally known electric power converter having a reactor and switches, a boost converter control system is disclosed, for example, in Japanese Patent Application Laid-Open No. JP 2013-70586 A.

[0003] This boost converter control system includes a choke coil, switches, diodes, and a control circuit. The control circuit controls the switches based on servo commands.

[0004] When the control circuit controls the switches, the switches are turned off based on a voltage slope of the cross-connection voltage of the switches.

[0005] When the boost converter control system is controlled in a currently critical mode, it is necessary to turn off the switches when a discharge of energy stored in the reactor is completed.

[0006] Therefore, conventionally, a reactor current is detected, and based on the detected current, the completion of the discharge of the energy stored in the reactor is judged.

[0007] However, the completion of the discharge of the energy stored in the choke coil can also be detected based on the change in the voltage slope of the cross-connection voltage of the switches.

[0008] Accordingly, the boost converter control system can be controlled in the currently critical mode without detecting the inductor current.

[0009] In the boost converter control system mentioned above, the diodes can be replaced by synchronous rectifying switches to reduce losses in the diodes.

[0010] When the diodes are replaced by synchronous rectification switches, the voltage change of the cross-connection voltage of the switches does not occur even when the discharge of the energy stored in the choke coil is completed because the synchronous rectification switches are turned on.

[0011] Therefore, the completion of the discharge of the energy stored in the choke coil cannot be detected.

[0012] Therefore, the boost converter control system cannot be controlled in the current critical mode without detecting the inductor current.

[0013] US 2004 / 0 062 061 A1 discloses the following: A bidirectional flyback circuit includes a switch on the primary side that regulates the recirculated energy to achieve near-zero voltage switching, and a switch on the secondary side that regulates the output voltage. No feedback circuit is required between an output side and an input side of the bidirectional flyback circuit to regulate the output voltage.

[0014] US 2002 / 0190698 A1 discloses the following: A buck converter, boost converter, or flyback converter is generally represented as a two-port converter having a primary side with a primary switching device and a secondary side with a secondary switching device. The primary switching device is controlled to adjust the duty cycle to the voltage on the primary side of the converter. The relationship between the duty cycle of the primary switching device and the primary voltage is a generally hyperbolic function. SUMMARY OF THE INVENTION

[0015] The present invention has been made in view of the above-mentioned problem and has an object to provide an electric power converter which can be controlled in a current critical mode without detecting a reactor current.

[0016] This object is achieved by the electrical power converter having the features of claim 1. Further advantageous embodiments and further developments are the subject of the subsequent claims.

[0017] In an electric power converter according to a first aspect, the electric power converter includes a reactor, a main switch that connects a power supply to the reactor by being turned on and supplies a current from the power supply to the reactor to store energy in the reactor, a synchronous rectification switch that connects the reactor to a load by being turned on during a period in which the main switch is turned off and releases the energy stored in the reactor to supply the current from the reactor to the load, and a control circuit that is connected to the main switch and the synchronous rectification switch and controls the main switch and the synchronous rectification switch.

[0018] The control circuit detects a switching transition time indicating a transient state of a cross-connection voltage of the main switch, and controls the main switch and the synchronous rectification switch based on the detected switching transition time.

[0019] Since there is a predetermined relationship between the switching transition time and the inductor current, the inductor current can be estimated using the switching transition time.

[0020] According to this structure, the main switch and the synchronous rectification switch are controlled based on the switching transition time.

[0021] Therefore, the inductor current can be appropriately controlled without detecting the inductor current.

[0022] Consequently, the electric power converter can be controlled in the current critical mode without detecting the reactor current. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings show: Fig. 1 shows the circuit diagram of the electrical power converter in a first embodiment; Fig. 2 is a circuit diagram of a switching transition time detection circuit used in Fig. 1 is shown; Fig. 3 a block diagram of a controller used in Fig. 1 is shown; Fig. 4 is a waveform diagram for explaining an operation of the electric power converter used in Fig. 1 is shown; Fig. 5 is another waveform diagram for explaining the operation of the electrical power converter shown in Fig. 1 is shown; Fig. 6 is a graph showing a relationship between a reactor current and a switching transition time; Fig. 7 is a waveform diagram for explaining an operation of the switching transition time detecting circuit; Fig. 8 is a circuit diagram of the electric power converter in a second embodiment; Fig. 9 is a circuit diagram of the switching transition time detection circuit shown in Fig. 8 is shown; Fig. 10 a block diagram of the controller used in Fig. 8 is shown; Fig. 11 is a circuit diagram of the electric power converter in the third embodiment; Fig. 12 is a circuit diagram of the switching transition time detection circuit shown in Fig. 11 is shown; Fig. 13 is a circuit diagram of the electric power converter in a fourth embodiment; Fig. 14 a block diagram of the controller used in Fig. 13 is shown; Fig. 15 is a circuit diagram of the electric power converter in a fifth embodiment; Fig. 16 is a circuit diagram of the electric power converter in a comparative example; Fig. 17 a block diagram of the controller used in Fig. 16 is shown, Fig. 18 is a circuit diagram of the electric power converter in another comparative example; and Fig. 19 a block diagram of the controller used in Fig. 18 is shown. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Embodiments of the present invention will be described below with reference to the drawings. (First embodiment)

[0025] First, with reference to Fig. 1 to Fig. 3 a structure of an electric power converter of a first embodiment is explained.

[0026] An electrical power converter 1, which is Fig. 1 is a device that converts a direct current supplied from a high-voltage battery B10 (power supply) mounted in a vehicle into a low-voltage direct current and supplies it to a low-voltage battery B11 (load) mounted in the vehicle to charge the low-voltage battery B11. It is a so-called step-down type boost / buck converter.

[0027] The high-voltage battery B10 is a battery with a nominal voltage of, for example, 48V. The low-voltage battery B11 is a battery with a nominal voltage of, for example, 12V.

[0028] The electrical power converter 1 comprises a smoothing capacitor 10, an FET 11 (main switch), an FET 12 (synchronous rectification switch), circuits or suppression circuits 13 and 14, a choke coil 15, a smoothing capacitor 16 and a control circuit 17.

[0029] The smoothing capacitor 10 is an element that smoothes an input voltage Vin of the electric power converter 1. The smoothing capacitor 10 also smoothes a voltage of the high-voltage battery B10.

[0030] One end of the smoothing capacitor 10 is connected to a positive terminal of the high-voltage battery B10, whereas another end of the smoothing capacitor 10 is connected to a negative terminal of the high-voltage battery B10, respectively.

[0031] FET 11 is an element that connects the high-voltage battery B10 to the choke coil 15 by being turned on, supplies power from the high-voltage battery B10 to the choke coil 15, and stores energy in the choke coil 15. FET 11 has a diode between a source and a drain in a parallel connection.

[0032] FET 12 is an element that connects choke coil 15 to low-voltage battery B11 by turning on during the period in which FET 11 is off, releasing the energy stored in choke coil 15, and supplying a current from choke coil 15 to low-voltage battery B11. FET 12 has a diode between a source and a drain in a parallel connection.

[0033] FETs 11 and 12 are connected in series. Specifically, the source of FET 11 is connected to the drain of FET 12. The drain of FET 11 is connected to one end of smoothing capacitor 10, and the source of FET 12 is connected to the other end of smoothing capacitor 10 and the negative terminal of low-voltage battery B11.

[0034] A series connection point of FETs 11 and 12 is connected to choke coil 15. The gates of FETs 11 and 12 are each connected to control circuit 15.

[0035] Suppressor circuits 13 and 14 are circuits that suppress surge voltages that are unnecessarily applied to FETs 11 and 12. Suppressor circuits 13 and 14 include suppressor capacitors 130 and 140, respectively.

[0036] One ends of the suppression capacitors 130 and 140 are connected to the drains of the FETs 11 and 12, and the other ends of the suppression capacitors 130 and 140 are connected to the sources of the FETs 11 and 12, respectively.

[0037] The choke coil 15 is an element that stores or releases energy. One end of the choke coil 15 is connected to the series connection point of the FETs 11 and 12, and the other end of the choke coil 15 is connected to a positive terminal of the low-voltage battery B11.

[0038] The smoothing capacitor 16 is an element that smoothes an output voltage Vout of the electrical power converter 1.

[0039] One end of the smoothing capacitor 16 is connected to the other end of the choke coil 15, whereas another end of the smoothing capacitor 16 is connected to the source of the FET 12.

[0040] The control circuit 17 is a circuit that controls the FETs 11 and 12.

[0041] The control circuit 17 controls the FETs 11 and 12 based on a target output voltage value Vout* of the electric power converter 1 input from the outside, detected input and output voltages Vin and Vout of the electric power converter 1, and a switching transition time.

[0042] Here, the switching transition time indicates a transition state of the voltage between the source and the drain of the FET 11 (cross-connection voltage).

[0043] The switching transition time is specifically a time required for the voltage between the source and drain of the FET 11 to reach a threshold voltage Vth after the FET 12 is commanded to turn off.

[0044] For example, the threshold voltage Vth is set to 10% of the input voltage Vin of the electrical power converter 1.

[0045] The control circuit 17 includes a switching transition time detection circuit 170, a controller 171, and drive circuits 172 and 173.

[0046] The switching transition time detection circuit 170 is a circuit that first commands a drive signal (mentioned later) output from the controller 171 to the FET 12 to turn off the FET 12, and thereafter outputs a pulse signal whose level is maintained until the voltage between the source and drain of the FET 11 reaches the threshold voltage Vth.

[0047] As in Fig. 2, the switching transition time detection circuit 170 includes resistors 170a to 170d, a comparator 170e, and an XOR circuit 170f.

[0048] Resistors 170a and 170b are connected in series. One end of resistor 170a is connected to the drain of FET 11, and the other end of resistor 170b is connected to the source of FET 12.

[0049] Resistors 170c and 170d are connected in series. One end of resistor 170c is connected to the series connection point of FETs 11 and 12, and the other end of resistor 170d is connected to the source of FET 12.

[0050] A non-inverting input terminal of the comparator 170e is connected to a series connection point of the resistors 170a and 170b, and an inverting input terminal of the comparator 170e is connected to a series connection point of the resistors 170c and 170d, respectively.

[0051] Here, a resistance value of each of the resistors 170a to 170d is designed so that an output of the comparator 170e is maintained at its level until the voltage between the source and the drain of the FET 11 reaches the threshold voltage Vth.

[0052] One input end of the XOR circuit 170f is connected to an output end of the comparator 170e, and another input end of the XOR circuit 170f is connected to the controller 171, respectively. One output end of the XOR circuit 170f is connected to the controller 171.

[0053] The controller 171 is a circuit that generates and outputs the drive signals for the FETs 11 and 12 based on the target output voltage value Vout*, the input and output voltages Vin and Vout, and the switching transition time.

[0054] The controller 171 is configured by a microcomputer and a program.

[0055] As in Fig. 3, the controller 171 includes an ON-time ratio calculation section 171a, a switching transition time measuring section 171b, a deviation calculation section 171c, a switching transition time control section 171d, correction calculation sections 171e and 171f, a deviation calculation section 171g, a voltage control section 171h, ON-time calculation sections 171i and 171j, and a drive signal generation section 171k.

[0056] The ON-time ratio calculation section 171a is a block that generates and outputs an ON-time ratio of the FETs 11 and 12 based on the input voltage Vin of the electric power converter 1, the target output voltage value Vout*, and the output voltage Vout.

[0057] Here, the ON-time ratio is the ratio of the ON time when the FETs are turned on and off. It is a so-called duty cycle.

[0058] The switching transition time measuring section 171b is a block that acquires and outputs the switching transition time by measuring a pulse width of the pulse signal that the switching transition time detecting circuit 170 outputs.

[0059] The deviation calculating section 171c is a block that calculates and outputs a deviation between a predetermined target switching transition time value and the switching transition time output from the switching transition time measuring section 171b.

[0060] Here, the target switching transition time value is designed based on a resonance duration of a resonant circuit formed by an inductance of the choke coil 15, capacitances of the noise suppression capacitors 130 and 140, and a parasitic capacitance of a circuit.

[0061] The target switching transition time value is designed, for example, to be 1 / 4 of the resonance period, or it is designed to be approximately 80% of 1 / 4 of the resonance period, taking into account a delay time of the switching transition time detection circuit 170 or a deviation of the delay time of the drive circuits 172 and 173.

[0062] The switching transition time control section 171d is a block that outputs a value as an ON-time ratio correction value for correcting the ON-time ratio by performing a proportional integral calculation of a deviation of the target switching transition time value output by the deviation calculation section 171c from the actual switching transition time.

[0063] The correction calculation section 171e is a block that outputs a value as the corrected ON-time ratio of the FET 11 by adding the ON-time ratio correction value output by the switching transition timing control section 171d to the ON-time ratio of the FET 11 output by the ON-time ratio calculation section 171a.

[0064] The correction calculation section 171f is a block that outputs a value as the corrected ON-time ratio of the FET 12 by subtracting the ON-time ratio correction value output by the switching transition timing control section 171d from the ON-time ratio of the FET 12 output from the ON-time ratio calculation section 171a.

[0065] The deviation calculation section 171g is a block that calculates and outputs a deviation of the target output voltage value Vout* of the electric power converter 1 input from the actual output voltage Vout from the outside.

[0066] The voltage control section 171h is a block that outputs a value as a conversion factor by performing a proportional integral calculation of the deviation of the target output voltage value Vout* output by the deviation calculation section 171b from the actual output voltage Vout.

[0067] The ON-time calculation section 171i is a block that outputs a value as the ON time for the FET 11 by multiplying the conversion factor output by the voltage control section 171h by the correct ON-time ratio for the FET 11 output by the correction calculation section 171e.

[0068] The ON-time calculation section 171j is a block that outputs a value as the ON time for the FET 12 by multiplying the conversion factor output by the voltage control section 171h by the corrected ON-time ratio for the FET 12 output from the correction calculation section 171e.

[0069] The drive signal generating section 171k is a block that generates and outputs the drive signal for driving the FETs 11 and 12 based on the ON times for the FETs 11 and 12 output by the ON time calculating sections 171i and 171j.

[0070] The control circuits 172 and 173, which are Fig. 1 are circuits that turn on and off the FETs 11 and 12, respectively, based on the drive signal output by the drive signal generating section 171k of the controller 171.

[0071] Input ends of the drive circuits 172 and 173 are connected to the drive signal generating section 171k, as shown in Fig. 3, and output ends of the control circuits 172 and 173 are connected to the gates of the FETs 11 and 12, respectively, as shown in Fig. 1 is shown.

[0072] The following is based on Fig. 1 to Fig. 7, an operation of the electric power converter of the first embodiment is explained.

[0073] First, with reference to Fig. 1 and Fig. 4 to Fig. 6 an overview of the operation of the electrical power converter, and a relationship between inductor current and the switching transition time is explained.

[0074] In Fig. 1, the high voltage battery B10 is connected to the choke coil 15 through the FET 12 when the FET 11 turns on while the FET 12 is off.

[0075] Accordingly, current is supplied from the high-voltage battery B10 to the choke coil 15, and energy is stored in the choke coil 15.

[0076] At this time, the reactor current IL, which defines a flow direction from the input side to the output side as a positive direction, flows into the reactor 15 and increases as shown in Fig. 4 is shown.

[0077] Then the choke coil 15 is connected to the low voltage battery B11 through the FET 12 as shown in Fig. 1 is shown when FET 11 turns off and FET 12 turns on during this period.

[0078] As a result, the energy stored in the choke coil 15 is released, and a current from the choke coil 15 is supplied to the low-voltage battery B11. At this time, the choke coil current IL decreases, as shown in Fig. 4 is shown.

[0079] Subsequently, the same operation is repeated, and electric power from the high-voltage battery B10 is supplied to the low-voltage battery B11, thereby charging the low-voltage battery B11.

[0080] If the electrical power converter 1, which is in Fig. 1 is controlled in a currently critical mode, it is necessary to turn off the FET 12 when the release of the energy stored in the choke coil 15 is completed.

[0081] In order to reduce a turn-on loss of the FET 11 and to operate the FET 11 with a zero voltage switching at this time, the FET 12 is turned off when the choke coil current IL becomes slightly negative (less than zero), as shown in Fig. 4 is shown.

[0082] When the FET 12 is turned off, the capacitance of the suppression capacitors 130 and 140 and the parasitic capacitance of the circuit are charged by the inductor current IL, which is slightly negative, and as in Fig. 5, a voltage Vp of the series connection point of the FETs 11 and 12 to which the choke coil 15 is connected rises and reaches the input voltage Vin within a short period of time.

[0083] When the choke coil current IL in the negative direction is larger than an optimal value, the rate of the capacitance of the noise suppression capacitors 130 and 140, and the rate of the parasitic capacitance of the circuit charged by the choke coil current IL becomes fast, and a rise in the voltage Vp becomes rapid.

[0084] On the other hand, if the reactor current IL in the negative direction is smaller than the optimum value, the rise of the voltage Vp becomes slow.

[0085] As in Fig. 1, the voltage between the source and drain of the FET 11 is a voltage such as subtracting the voltage Vp from the input voltage Vin.

[0086] Therefore, as in Fig. 5, a drop in the voltage between the source and drain of the FET 11 occurs rapidly when the choke current IL in the negative direction is larger than the optimum value.

[0087] As a result, the time required for the voltage between the source and drain of the FET 11 to reach the threshold voltage Vth after the FET 12 is turned off, ie, the switching transition time, becomes short.

[0088] On the other hand, if the inductor current IL in the negative direction is smaller than the optimum value, the voltage drop between the source and drain of FET 11 becomes slow. Consequently, the switching transition time becomes long.

[0089] That is, there is a relationship between the inductor current IL and the switching transition time in that the switching transition time becomes shorter when the inductor current IL becomes large in the negative direction, as shown in Fig. 6. Therefore, the inductor current IL can be estimated using the switching transition time.

[0090] The following is based on Fig. 2 and Fig. 7 an operation of the switching transition time detection circuit is explained.

[0091] The resistance value of each of the resistors 170a to 170d used in Fig. 2, is designed such that the output of the comparator 170e is maintained at its level until the voltage between the source and drain of the FET 11 reaches the threshold voltage Vth.

[0092] As in Fig. 7, the comparator 170e therefore outputs a high level signal until the voltage between the source and drain of the FET 11 reaches the threshold voltage Vth.

[0093] Thereafter, the XOR circuit 170f outputs a high level signal when the drive signal level for the FET 12 is low, so that the FET 12 is commanded to turn off, and the output of the comparator 170e is high.

[0094] Accordingly, the switching transition time detection circuit 170 can output the pulse signal so as to maintain its level until the voltage between the source and drain of the FET 11 reaches the threshold voltage Vth after it commands the drive signal for the FET 12 to turn off the FET 12.

[0095] The following describes the operation of the controller and the control circuit with reference to Fig. 1 and Fig. 3 described.

[0096] The ON-time ratio calculation section 170a, which is Fig. 3, calculates and outputs the ON-time ratio of the FETs 11 and 12 based on the input voltage Vin, the target output voltage value Vout*, and the output voltage Vout.

[0097] The switching transition time measuring section 171b obtains the switching transition time by measuring the pulse width of the pulse signal output from the switching transition time detecting circuit 170.

[0098] The deviation calculating section 171c calculates the deviation between the predetermined target switching transition time value and the switching transition time output from the switching transition time measuring section 171b.

[0099] The switching transition time control section 171d outputs the value as the ON-time ratio correction value by performing the proportional integral calculation of the deviation of the target switching transition time value from the actual switching transition time.

[0100] The correction calculation section 171e outputs the value as the corrected ON-time ratio for the FET 11 by adding the ON-time ratio correction value to the ON-time ratio for the FET 11.

[0101] The correction calculation section 171f outputs the value as the corrected ON-time ratio for the FET 12 by subtracting the ON-time ratio correction value from the ON-time ratio for the FET 12.

[0102] This corrects the ON-time ratio so that the ON-time transition time can assume a target ON-time transition time value.

[0103] The deviation calculation section 171g calculates the deviation of the target output voltage value Vout* from the actual output voltage Vout.

[0104] The voltage control section 171h outputs the value as the conversion factor by performing the proportional integral calculation of the deviation of the target output voltage value Vout* from the actual output voltage Vout.

[0105] The ON-time calculating section 171i outputs the value as the ON-time for the FET 11 by multiplying the conversion factor by the corrected ON-time ratio for the FET 11.

[0106] The ON-time calculating section 171j outputs the value as the ON-time for the FET 12 by multiplying the conversion factor by the corrected ON-time ratio for the FET 12.

[0107] The drive signal generating section 171k generates and outputs the drive signal for driving the FETs 11 and 12 based on the ON time for the FETs 11 and 12.

[0108] The control circuits 172 and 173, which are Fig. 1, the FETs 11 and 12 turn on and off based on the drive signal, respectively.

[0109] Accordingly, the switching transition time is controlled to the target switching transition time value.

[0110] This means that the choke coil current IL is controlled to the optimal value.

[0111] Therefore, the electric power converter 1, which supplies electric power from the high-voltage battery B10 to the low-voltage battery B11, can be controlled in the current critical mode without detecting a reactor current.

[0112] Effects of the electric power converter of the first embodiment will be explained below.

[0113] As in Fig. As shown in Fig. 6, the reactor current IL can be estimated using the switching transition time because there is a predetermined relationship between the switching transition time and the reactor current IL.

[0114] According to the first embodiment, the control circuit 17 detects the switching transition time and controls the FETs 11 and 12 based on the switching transition time.

[0115] Therefore, the reactor current IL can be appropriately controlled without detecting a reactor current.

[0116] Therefore, the electric power converter 1, which is a step-up / step-down converter, can be controlled in the current critical mode without detecting a reactor current.

[0117] In addition, considering that characteristics of each element configuring the electric power converter have deviations, the reactor current has conventionally been controlled to be larger in the negative direction in particular.

[0118] However, since the characteristic variations of each element are reflected in the switching transition time in the present embodiment, it is primarily unnecessary to control the reactor current IL larger in the negative direction. Therefore, switching loss and conduction loss can be suppressed.

[0119] According to the first embodiment, the control circuit 17 controls the FETs 11 and 12 based on the input voltage Vin, the output voltage Vout, and the deviation of the target switching transition time value from the actual switching transition time.

[0120] Therefore, the switching transition time can be controlled to the target switching transition time value.

[0121] This means that the reactor current IL can be controlled to the optimal value. Therefore, the electrical power converter 1 can be reliably controlled in the current critical mode.

[0122] According to the first embodiment, the control circuit 17 corrects the ON-time ratio obtained based on the input voltage Vin and the output voltage Vout by the corrected ON-time ratio obtained based on the deviation of the target switching transition time value from the actual switching transition time, and controls the FETs 11 and 12 based on the corrected ON-time ratio.

[0123] Therefore, the switching transition time can be reliably controlled to the target switching transition time value.

[0124] According to the first embodiment, the control circuit 17 controls the FETs 11 and 12 based on the deviation of the target output voltage value Vout from the actual output voltage Vout.

[0125] Therefore, the output voltage Vout can be controlled to the target output voltage value Vout*.

[0126] According to the first embodiment, the control circuit 17 changes the ON-time ratio corrected based on the deviation of the target output voltage value Vout* from the actual output voltage Vout to the ON time, and controls the FETs 11 and 12 based on the ON time.

[0127] Therefore, the output voltage Vout can be reliably controlled to the target output voltage value Vout*. (Second embodiment)

[0128] The electric power converter of the second embodiment is explained below.

[0129] Although the electric power converter of the first embodiment supplies electric power from the high-voltage battery to the low-voltage battery, the electric power converter of the second embodiment supplies electric power from the low-voltage battery to the high-voltage battery.

[0130] First, with reference to Fig. 8 to Fig. 10 a structure of the electric power converter of the second embodiment is explained.

[0131] An electrical power converter 2, which is Fig. 8 is a device that converts a direct current supplied from a low-voltage battery B21 (power supply) mounted in a vehicle into a low-voltage direct current and supplies it to a high-voltage battery B20 (load) mounted in the vehicle to charge the high-voltage battery B20. It is a so-called boost-type buck-boost converter.

[0132] Here, the high-voltage battery B20 and the low-voltage battery B21 are the same as the high-voltage battery B10 and the low-voltage battery B11 of the first embodiment.

[0133] The electrical power converter 1 has a smoothing capacitor 26, a choke coil 25, an FET 21 (synchronous rectification switch), an FET 22 (main switch), interference suppression capacitors 23 and 24, a smoothing capacitor 20 and a control circuit 27.

[0134] Although there are differences in the function of each component, the structures of the smoothing capacitor 26, the choke coil 25, the FETs 21 and 22, the noise suppression circuits 23 and 24, and the smoothing capacitor 20 are the same as the structures of the smoothing capacitor 16, the choke coil 15, the FETs 11 and 12, the noise suppression circuits 13 and 14, and the smoothing capacitor 10 of the first embodiment.

[0135] The smoothing capacitor 26 is an element that smoothes an input voltage Vin of the electric power converter 2. The smoothing capacitor 26 also smoothes a voltage of the low-voltage battery B21.

[0136] One end of the smoothing capacitor 26 is connected to a positive terminal of the low-voltage battery B21, whereas another end of the smoothing capacitor 26 is connected to a negative terminal of the low-voltage battery B21, respectively.

[0137] The choke coil 25 is an element that stores or releases energy. One end of the choke coil 25 is connected to one end of the smoothing capacitor 26, and the other end of the choke coil 25 is connected to the FETs 21 and 22, respectively.

[0138] The FET 21 is an element that connects the choke coil 25 to the high-voltage battery B20 by being turned on during the period in which the FET 22 is turned off, releasing the energy stored in the choke coil 25, and supplying current from the choke coil 25 to the high-voltage battery B20.

[0139] The FET 21 has a diode between a source and a drain in the manner of a parallel connection.

[0140] The FET 22 is an element that connects the low-voltage battery B21 to the choke coil 25 by being turned on, supplies current from the low-voltage battery B21 to the choke coil 25, and stores energy in the choke coil 25.

[0141] The FET 22 has a diode between a source and a drain in the manner of a parallel connection.

[0142] FETs 21 and 22 are connected in series. Specifically, the source of FET 21 is connected to the drain of FET 22. A series connection point of FETs 21 and 22 is connected to choke coil 25.

[0143] The source of FET 22 is connected to one end of smoothing capacitor 26 and the negative terminal of high-voltage battery B20, and the drain of FET 21 is connected to the positive terminal of high-voltage battery B20, respectively. The gates of FETs 21 and 22 are each connected to control circuit 27.

[0144] Suppressor circuits 23 and 24 are circuits that suppress surge voltages that are unnecessarily applied to FETs 21 and 22. Suppressor circuits 23 and 24 include suppressor capacitors 230 and 240, respectively.

[0145] One ends of the suppression capacitors 230 and 240 are connected to the drains of the FETs 21 and 22, and the other ends of the suppression capacitors 230 and 240 are connected to the sources of the FETs 21 and 22, respectively.

[0146] The smoothing capacitor 26 is an element that smoothes an output voltage Vout of the electrical power converter 2.

[0147] One end of the smoothing capacitor 26 is connected to the drain of the FET 21, whereas another end of the smoothing capacitor 26 is connected to the source of the FET 22, respectively.

[0148] The control circuit 27 is a circuit that controls the FETs 21 and 22. The control circuit 27 controls the FETs 21 and 22 based on a target output voltage value Vout* of the electric power converter 2 input from the outside, detected input and output voltages Vin and Vout of the electric power converter 2, and a switching transition time.

[0149] Here, the switching transition time is a time required for the voltage between the source and drain of the FET 22 (cross-connection voltage) to reach a threshold voltage Vth after the FET 21 is commanded to turn off.

[0150] The threshold voltage Vth is designed similarly to that in the first embodiment.

[0151] The control circuit 27 includes a switching transition time detection circuit 270, a controller 271, and drive circuits 272 and 273.

[0152] The switching transition time detection circuit 270 is a circuit that first commands a drive signal (mentioned later) output from the controller 271 to the FET 21 to turn off the FET 21, and thereafter outputs a pulse signal whose level is maintained until the voltage between the source and drain of the FET 22 reaches the threshold voltage Vth.

[0153] As in Fig. 9, the switching transition time detection circuit 270 includes a reference power supply 270g, resistors 270c and 270d, a comparator 270e, and an XOR circuit 270f.

[0154] The reference power supply 270g is a power supply that outputs a voltage corresponding to the threshold voltage Vth.

[0155] A positive terminal of the reference power supply 270g is connected to the comparator 270e, and a negative terminal of the reference power supply 270g is connected to the source of the FET 22, respectively.

[0156] Resistors 270c and 270d are connected in series. One end of resistor 270c is connected to the series connection point of FETs 21 and 22, and one end of resistor 270d is connected to the source of FET 22, respectively.

[0157] A non-inverting input terminal of the comparator 270e is connected to the positive terminal of the reference power supply 270g, and an inverting input terminal of the comparator 270e is connected to the series connection point of the resistors 270c and 270d, respectively.

[0158] Here, the resistance value of each of the resistors 270c and 270d is designed taking into account the voltage of the reference power supply 270g so that an output of the comparator 270e maintains its level until the voltage between the source and drain of the FET 22 reaches the threshold voltage Vth.

[0159] One input end of the XOR circuit 270f is connected to an output end of the comparator 270e, and another input end of the XOR circuit 270f is connected to the controller 271, respectively. One output end of the XOR circuit 270f is connected to the controller 271.

[0160] The controller 271, which is in Fig. 8 is a circuit that generates and outputs the drive signals for the FETs 21 and 22 based on the target output voltage value Vout*, the input and output voltages Vin and Vout, and the switching transition time.

[0161] The controller 271 is formed by a microcomputer and a program.

[0162] As in Fig. As shown in Fig. 10, the controller 271 includes an ON-time ratio calculation section 271a, a switching transition time measuring section 271b, a deviation calculation section 271c, a switching transition time control section 271d, correction calculation sections 271e and 271f, a deviation calculation section 271g, a voltage control section 271h, ON-time calculation sections 271i and 271j, and a drive signal generation section 271k.

[0163] Unlike the correction calculation section 271e of the first embodiment, the correction calculation section 271e is a block that outputs a value as the corrected ON-time ratio for the FET 21 by subtracting the ON-time ratio correction value from the ON-time ratio of the FET 21.

[0164] In contrast to the correction calculation section 171f of the first embodiment, the correction calculation section 271f is a block that outputs a value as the corrected ON-time ratio for the FET 22 by adding the ON-time ratio correction value to the ON-time ratio for the FET 22.

[0165] The controller 271 has an identical structure to the controller 171 of the first embodiment, except for the correction calculation sections 271e and 271f.

[0166] The following is a summary of the Fig. 8 to Fig. 10 explains an operation of the electric power converter of the second embodiment.

[0167] First, with reference to Fig. 9 an operation of the switching transition time detection circuit is explained.

[0168] The reference power intake 270g, which in Fig. 9 outputs the voltage corresponding to the threshold voltage.

[0169] The resistance value of each of the resistors 270c and 270d is designed taking into account the voltage of the reference power 270g so that an output of the comparator 270e maintains its level until the voltage between the source and drain of the FET 22 reaches the threshold voltage Vth.

[0170] Therefore, the comparator 270e outputs a high level signal until the voltage between the source and drain of the FET 22 reaches the threshold voltage Vth.

[0171] Thereafter, the XOR circuit 270f outputs a high level signal when the drive signal level for the FET 21 is low, so that the turn-off of the FET 21 is commanded, and the output of the comparator 270e is high.

[0172] Accordingly, the switching transition time detection circuit 270 can output the pulse signal whose level is maintained until the voltage between the source and drain of the FET 22 reaches the threshold voltage Vth after the drive signal for the FET 21 commands the FET 21 to turn off.

[0173] The following describes the operation of the controller and the control circuit with reference to Fig. 8 and Fig. 10 explained.

[0174] In contrast to the correction calculation section 171e of the first embodiment, the correction calculation section 271e shown in Fig. 10, the value is calculated as the corrected ON-time ratio for the FET 21 by subtracting the ON-time ratio correction value from the ON-time ratio for the FET 21.

[0175] Unlike the correction calculation section 171f of the first embodiment, the correction calculation section 271f outputs the value as the corrected ON-time ratio for the FET 22 by adding the ON-time ratio correction value to the ON-time ratio for the FET 22.

[0176] The controller 271 performs the same operation as the controller 171 of the first embodiment, except for the operations of the correction calculation sections 271e and 271f.

[0177] The control circuits 272 and 273, which are Fig. 8, the FETs 21 and 22 turn on and off based on the drive signal, respectively.

[0178] Accordingly, the switching transition time is controlled to the target switching transition time value.

[0179] That is, the reactor current IL, which defines a flow direction from the input side to the output side as a positive direction, is controlled to the optimal value.

[0180] Therefore, the electric power converter 2, which supplies electric power from the low-voltage battery B21 to the high-voltage battery B20, can be controlled to the currently critical mode without detecting a reactor current.

[0181] Next, effects of the electric power converter of the second embodiment are explained.

[0182] According to the second embodiment, the same effects as in the first embodiment are obtained.

[0183] In addition, although the switching transition time detection circuit 270 is composed using the reference power supply 270g as an example in the second embodiment, the composition thereof is not limited thereto.

[0184] The resistance value of the resistors can be adjusted by the same composition as in the switching transition time detection circuit 170 of the first embodiment. (Third embodiment)

[0185] An electric power converter of the third embodiment will be explained below.

[0186] The electric power converter of the third embodiment is a combination of the electric power converter in the first embodiment and the electric power converter in the second embodiment, and enables electric power to be supplied bidirectionally between a high-voltage battery and a low-voltage battery.

[0187] First, with reference to Fig. 11 and Fig. 12 explains a composition of the electric power converter of the third embodiment.

[0188] An electrical power converter 3, which is Fig. 11 is a device that converts a direct current supplied from a high-voltage battery B30 (power supply) mounted in a vehicle into a low-voltage current and supplies it to a low-voltage battery B31 (load) mounted in the vehicle to charge the low-voltage battery B31.

[0189] In addition, it is, in turn, a device that converts a direct current supplied from a low-voltage battery B31 (power supply) mounted in a vehicle into a high-voltage direct current and supplies it to a high-voltage battery B30 (load) mounted in the vehicle to charge the high-voltage battery B30.

[0190] This means it's a device that can supply electrical power bidirectionally between the high-voltage battery B30 and the low-voltage battery B31. It's a so-called boost / buck type of boost / buck converter.

[0191] The electrical power converter 3 has a smoothing capacitor 30, an FET 31 (main switch), an FET 32 (synchronous rectification switch), noise suppression circuits 33 and 34, a choke coil 35, a smoothing capacitor 316 and a control circuit 37.

[0192] The composition of the smoothing capacitor 30, the FETs 31 and 32, the noise suppression circuits 33 and 34, the choke coil 35, and the smoothing capacitor 36 is the same as that of the smoothing capacitor 10, the FETs 11 and 12, the noise suppression circuits 13 and 14, the choke coil 15, and the smoothing capacitor 16 of the first embodiment and that of the smoothing capacitor 20, the FETs 21 and 22, the noise suppression circuits 23 and 24, the choke coil 25, and the smoothing capacitor 26 of the second embodiment.

[0193] The control circuit 37 is a circuit that controls the FETs 31 and 32. The control circuit 37 performs the same operation as the control circuit 17 of the first embodiment when electric power is supplied from the high-voltage battery B30 to the low-voltage battery B31, and it performs the same operation as the control circuit 27 of the second embodiment when electric power is supplied from the low-voltage battery B31 to the high-voltage battery B30.

[0194] The control circuit 37 includes a switching transition time detection circuit 370, a controller 371, and drive circuits 372 and 373.

[0195] The switching transition time detection circuit 370 is a circuit having a function of the switching transition time detection circuit 170 of the first embodiment and a function of the switching transition time detection circuit 270 of the second embodiment.

[0196] As in Fig. As shown in Figure 12, the switching transition time detection circuit 370 includes resistors 370h to 370l, comparators 370m and 370n, and XOR circuits 370l and 370p.

[0197] Resistors 370h to 370j are connected in series. One end of resistor 370h is connected to the drain of FET 31, and the other end of resistor 370j is connected to the source of FET 32, respectively.

[0198] Resistors 370k and 370l are connected in series. One end of resistor 370k is connected to the series connection point of FETs 31 and 32, and the other end of resistor 370l is connected to the source of FET 32, respectively.

[0199] A non-inverting input terminal of the comparator 370m is connected to a series connection point of the resistors 370h and 370i, and an inverting input terminal of the comparator 370m is connected to a series connection point of the resistors 370 and 370l, respectively.

[0200] A non-inverting input terminal of comparator 370n is connected to a series connection point of resistors 370k and 370l, and an inverting input terminal of comparator 370n is connected to a series connection point of resistors 370i and 370j, respectively.

[0201] Here, a resistance value of each of the resistors 370h to 370l is designed such that an output of the comparator 370m maintains its high level until the voltage between the source and drain of the FET 31 reaches the threshold voltage Vth, and it is designed such that an output of the comparator 370n maintains its level until the voltage between the source and drain of the FET 32 reaches the threshold voltage Vth.

[0202] One input end of the XOR circuit 370o is connected to an output end of the comparator 370m, and another input end of the XOR circuit 370o is connected to a drive signal generating section (not shown) of the controller 371, respectively, which outputs a drive signal for the FET 32.

[0203] An output end of the XOR circuit 370o is connected to a switching transition time measuring section (not shown) of the controller 371, which measures a switching transition time of the FET 31.

[0204] One input end of the XOR circuit 370p is connected to an output end of the comparator 370m, and another input end of the XOR circuit 370p is connected to a drive signal generating section (not shown) of the controller 371, respectively, which outputs a drive signal for the FET 31.

[0205] An output end of the XOR circuit 370p is connected to a switching transition time measuring section (not shown) of the controller 371, which measures a switching transition time of the FET 32.

[0206] The controller 371, which is in Fig. 11 is a circuit having a function of the controller 171 of the first embodiment and a function of the controller 271 of the second embodiment.

[0207] The controller 371 includes components of the controller 171 of the first embodiment and components of the controller 271 of the second embodiment.

[0208] The drive circuits 372 and 373 have the same functions and structures as the drive circuits 172 and 173 of the first embodiment and the drive circuits 272 and 273 of the second embodiment.

[0209] The following is based on Fig. 11 and Fig. 12 explains an operation of the electric power converter of the third embodiment.

[0210] The following is based on Fig. 12 an operation of the switching transition time detection circuit is explained.

[0211] The resistance value of each of the resistors 370h to 370l used in Fig. 12, is designed so that an output of the comparator 370m maintains its level until the voltage between the source and drain of the FET 31 reaches the threshold voltage Vth, and is designed so that an output of the comparator 370n maintains its level until the voltage between the source and drain of the FET 32 reaches the threshold voltage Vth.

[0212] Therefore, the comparator 370m outputs a high level signal until the voltage between the source and drain of the FET 31 reaches the threshold voltage Vth.

[0213] Then, the XOR circuit 370o outputs a high level signal when the drive signal level for the FET 32 is low, so that the turn-off of the FET 32 is commanded, and the output of the comparator 370m is high.

[0214] Accordingly, the switching transition time detection circuit 370 can output the pulse signal whose level is maintained until the voltage between the source and drain of the FET 31 reaches the threshold voltage Vth after the drive signal commands the FET 32 to turn off the FET 32.

[0215] On the other hand, the comparator 370n outputs a high level signal until the voltage between the source and drain of the FET 32 reaches the threshold voltage Vth.

[0216] Then, the XOR circuit 370p outputs a high level signal when the drive signal level for the FET 31 is low, so that the FET 31 is commanded to turn off, and the output of the comparator 370n is high.

[0217] Accordingly, the switching transition time detection circuit 370 can output the pulse signal whose level is maintained until the voltage between the source and drain of the FET 32 reaches the threshold voltage Vth after the drive signal commands the FET 31 to turn off the FET 31.

[0218] The following describes the operation of the controller and the control circuits with reference to Fig. 11 explained.

[0219] The controller 371, which is in Fig. 11 performs the same operation as the controller 171 of the first embodiment when power is supplied from the high-voltage battery B30 to the low-voltage battery B31.

[0220] On the other hand, the controller 371 performs the same operation as the controller 271 of the second embodiment when electric power is supplied from the low-voltage battery B31 to the high-voltage battery B30.

[0221] The drive circuits 372 and 373 turn on and off the FETs 31 and 32, respectively, based on the drive signals.

[0222] As a result, the switching transition time is controlled to the target switching transition time value. This means that the inductor current IL is controlled to the optimal value.

[0223] Therefore, the electric power converter 3, which supplies electric power bidirectionally between the high-voltage battery B30 and the low-voltage battery B31, can be controlled in the currently critical mode without detecting a reactor current.

[0224] Effects of the electric power converter of the third embodiment will be explained below.

[0225] According to the third embodiment, the same effects as in the first embodiment are obtained.

[0226] In addition, although the switching transition time detection circuit 370 is not composed using the reference power supply as an example in the third embodiment, its configuration is not limited thereto.

[0227] The switching transition time detection circuit 170 of the first embodiment and the switching transition time detection circuit 270 of the second embodiment may be combined. (Fourth embodiment)

[0228] The electric power converter of the fourth embodiment is explained below.

[0229] With respect to the electric power converter of the first embodiment, the electric power converter of the fourth embodiment detects an output current and controls the FET based on the detected output current.

[0230] First, with reference to Fig. 13 and Fig. 14 a structure of the electric power converter of the fourth embodiment is explained.

[0231] An electrical power converter 4, which is Fig. 13 is a device that converts a direct current supplied from a high-voltage battery B40 (power supply) mounted in a vehicle into a low-voltage direct current and supplies it to a low-voltage battery B41 (load) mounted in the vehicle to charge the low-voltage battery B41. It is a so-called buck-type boost / buck converter.

[0232] The electrical power converter 4 has a smoothing capacitor 40, an FET 41 (main switch), an FET 42 (synchronous rectification switch), noise suppression circuits 43 and 44, a choke coil 45, a smoothing capacitor 46 and a control circuit 47.

[0233] The electrical power converter 4 further comprises a current sensor 48.

[0234] The structures and functions of the smoothing capacitor 40, the FETs 43 and 44, the noise suppression circuits 43 and 44, the choke coil 45, and the smoothing capacitor 46 are the same as the functions and structures of the smoothing capacitor 10, the FETs 11 and 12, the noise suppression circuits 13 and 14, the choke coil 15, and the smoothing capacitor 16 of the first embodiment.

[0235] The current sensor 48 is an element that detects an output current Iout of the electric power converter 4. The current sensor 48 is arranged on a wiring connecting one end of the reactor 45 and a positive terminal of the low-voltage battery B41, and is connected to the control circuit 47.

[0236] The control circuit 47 is a circuit that controls the FETs 41 and 42. The control circuit 47 controls the FETs 41 and 42 based on a target output voltage value Vout* and a target output current value Iout* of the electric power converter 40 input from the outside, detects input and output voltages Vin and Vout and an output current value Iout of the electric power converter 40, and a switching transition time.

[0237] Here, the switching transition time is a time required for the voltage between the source and drain of the FET 41 (cross-connection voltage) to reach a threshold voltage Vth after the FET 42 is commanded to be turned off, and is designed similarly to the first embodiment.

[0238] The control circuit 47 includes a switching transition time detection circuit 470, a controller 471, and drive circuits 472 and 473.

[0239] The switching transition time detection circuit 470 has the same function and structure as the switching transition time detection circuit 170 of the first embodiment.

[0240] Controller 471 is a circuit that generates and outputs the drive signals for FETs 41 and 42 based on a target output voltage value Vout*, the target output current value Iout*, the input and output voltages Vin and Vout, the output current value Iout, and the switching transition time. Controller 471 is implemented by a microcomputer and a program.

[0241] As in Fig. As shown in Fig. 14, the controller 471 includes an ON-time ratio calculation section 471a, a switching transition time measuring section 471b, a deviation calculation section 471c, a switching transition time control section 471d, correction calculation sections 471e and 471f, a deviation calculation section 471g, a voltage control section 471h, ON-time calculation sections 471i and 471j, and a drive signal generation section 471k.

[0242] Further, the controller 471 includes a selection section 471l, a deviation calculation section 471m, and a current control section 471n.

[0243] The ON-time ratio calculation section 471a, the switching transition time measuring section 471b, the deviation calculation section 471c, the switching transition time control section 471d, the correction calculation sections 471e and 471f, and the deviation calculation section 471g have the same functions and structures as the ON-time ratio calculation section 171a, the switching transition measuring section 171b, the deviation calculation section 171c, the switching transition time control section 171d, the correction calculation sections 171e and 171f, and the deviation calculation section 171g of the first embodiment.

[0244] The voltage control section 471h is a block that outputs a value as a target output current value by performing a proportional integral calculation of the deviation of the target output voltage value Vout* output by the deviation calculation section 471g from the actual output voltage Vout.

[0245] The selecting section 471l is a block that selects and outputs a smaller than a new target output current value among the target output current value output by the voltage control section 471h and the target output current value Iout* input from the outside.

[0246] The deviation calculation section 471m is a block that calculates and outputs the deviation of the target output current value that the selection section 471l outputs from the actual output current value Iout of the electric power converter 4 that the current sensor 48 detects.

[0247] The current control section 471n is a block that outputs a value as a conversion factor by performing a proportional integral calculation of a deviation of the new target output current value, which the deviation calculation section 471m outputs, from the actual output current Iout.

[0248] The ON-time calculation section 471i is a block that outputs a value as the ON time for the FET 41 by multiplying the conversion factor output by the voltage control section 471h by the corrected ON-time ratio for the FET 41 that the correction calculation section 471 outputs.

[0249] The ON-time calculation section 471j is a block that outputs a value as the ON time for the FET 42 by multiplying the conversion factor output from the voltage control section 471h by the corrected ON-time ratio for the FET 42 that the correction calculation section 471i outputs.

[0250] The drive signal generating section 471k is a block that generates and outputs the drive signal for driving the FETs 41 and 42 based on the ON times of the FETs 41 and 42 output by the ON time calculating sections 471i and 471j.

[0251] The control circuits 472 and 473, which are Fig. 13 have the same functions and structures as the drive circuits 172 and 173 of the first embodiment.

[0252] The following is based on Fig. 13 and Fig. 14 explains an operation of the electric power converter of the fourth embodiment.

[0253] Since the operation of the switching transition time detection circuit 470, which is Fig. 13 is the same as the operation of the switching transition time detection circuit 170 of the first embodiment, an explanation will be omitted.

[0254] The operating modes of the controller and the control circuit are explained.

[0255] The voltage control section 471h, which is Fig. 14, outputs the value as the target output current value by performing the proportional integral calculation of the deviation of the target output voltage value Vout* from the actual output voltage Vout.

[0256] The selecting section 471l selects and outputs the smaller of the target output current value output by the voltage control section 471h and the target output current value Iout* input from the outside as the new target output current value.

[0257] The deviation calculation section 471m calculates and outputs the deviation of the new target output current value from the actual output current Iout.

[0258] The current control section 471n outputs the value as the conversion factor by performing the proportional integral calculation of the deviation of the new target output current value from the actual output current Iout.

[0259] That is, unlike the controller 171 of the first embodiment, the conversion factor is calculated taking into account the target output current value and the output current.

[0260] The ON-time calculating section 471i outputs the value as the ON-time for the FET 41 by multiplying the conversion factor output by the current control section 471n by the corrected ON-time ratio for the FET 41.

[0261] The ON-time calculating section 471j outputs the value as the ON-time for the FET 42 by multiplying the conversion factor output by the current control section 471n by the corrected ON-time ratio for the FET 42.

[0262] The drive signal generating section 471k generates and outputs the drive signal for driving the FETs 41 and 42 based on the ON time for the FETs 41 and 42.

[0263] The control circuits 472 and 473, which are Fig. 13, the FETs 41 and 42 turn on and off based on the drive signal, respectively.

[0264] As a result, the switching transition time is controlled to the target switching transition time value. This means that the inductor current IL is controlled to the optimal value.

[0265] Therefore, the electric power converter 4, which supplies electric power from the high-voltage battery B40 to the low-voltage battery B41, can be controlled in the currently critical mode without detecting a reactor current.

[0266] Effects of the electric power converter of the fourth embodiment will be explained below.

[0267] According to the fourth embodiment, like the first embodiment, the electric power converter 4, which is a boost / buck converter, can be controlled in the current critical mode without detecting a reactor current. Furthermore, switching loss can be suppressed.

[0268] According to the fourth embodiment, the control circuit 47 controls the FETs 41 and 42 based on the deviation of the target output voltage value Vout* from the actual output voltage Vout, the target output current value Iout*, and the output current value Iout.

[0269] Therefore, the output voltage Vout can be controlled to the target output voltage value Vout*, and the output current value Iout can be controlled to the target output current value Iout*.

[0270] According to the fourth embodiment, the control circuit 47 selects a smaller one as a new target output current value among the target output current value obtained based on the deviation of the target output voltage value Vout* from the actual output voltage Vout and the target output current value Iout* input from the outside, and controls the FETs 41 and 42 based on the deviation of the new target output current value from the actual output current Iout.

[0271] Therefore, the output voltage Vout can be reliably controlled to the target output voltage value Vout*, and the output current value Iout can be reliably controlled to the target output current value Iout*. (Fifth embodiment)

[0272] The electric power converter of the fifth embodiment is explained below.

[0273] The electric power converter of the fifth embodiment is configured as a flyback converter with respect to the electric power converter of the first embodiment, which is a boost / buck converter.

[0274] First, with reference to Fig. 15 a structure of the electric power converter of the fifth embodiment is explained.

[0275] An electrical power converter 5, which is Fig. 15 is a device that converts a direct current supplied from a high-voltage battery B50 (power supply) mounted in a vehicle into a low-voltage direct current and supplies it to a low-voltage battery B51 (load) mounted in the vehicle to charge the low-voltage battery B51. It is a so-called step-down type flyback converter.

[0276] Here, the high-voltage battery B50 and the low-voltage battery B51 are the same as the high-voltage battery B10 and the low-voltage battery B11 in the first embodiment.

[0277] The electrical power converter 5 has a smoothing capacitor 50, an FET 51 (main switch), an FET 52 (synchronous rectification switch), noise suppression circuits 53 and 54, a transformer (choke coil) 55, a smoothing capacitor 56 and a control circuit 57.

[0278] The smoothing capacitor 50 has the same function and structure as the smoothing capacitor 10 of the first embodiment.

[0279] FET 51 is an element that connects the high-voltage battery B50 to the transformer 55 by turning on, supplying a current from the high-voltage battery B50 to the transformer 55, and storing energy in the choke coil 55. FET 51 has a diode between a source and a drain in a parallel connection.

[0280] The drain of the FET 51 is connected to the transformer 55, and the source of the FET 51 is connected to one end of the smoothing capacitor 50, respectively.

[0281] The FET 52 is an element that connects the transformer 55 to the low-voltage battery B51 by being turned on during a period in which the FET 51 is off, releasing the energy stored in the transformer 55, and supplying current from the transformer 55 to the low-voltage battery B51.

[0282] FET 52 has a diode connected between a source and a drain in a parallel circuit configuration. The source of FET 52 is connected to transformer 55, and the drain of FET 51 is connected to a positive terminal of low-voltage battery B51, respectively.

[0283] The noise suppression circuits 53 and 54 have noise suppression capacitors 530 and 540, respectively, and have the same functions and structures as the noise suppression circuits 13 and 14 of the first embodiment.

[0284] The transformer 55 is an element that stores or releases energy, and, in a state where it is insulated, converts and outputs an alternating current supplied to an alternating current having a predetermined voltage according to a turns ratio.

[0285] The transformer 55 has a primary winding 550 and a secondary winding 551. One end of the primary winding 550 is connected to one end of the smoothing capacitor 50, and another end of the primary winding 550 is connected to the drain of the FET 51, respectively.

[0286] One end of the secondary winding 551 is connected to the source of the FET 52, and another end of the secondary winding 551 is connected to a negative terminal of the low-voltage battery B51, respectively.

[0287] The smoothing capacitor 56 has the same function as the smoothing capacitor 16 of the first embodiment. One end of the smoothing capacitor 56 is connected to the drain of the FET 52, and the other end of the smoothing capacitor 56 is connected to the other end of the secondary winding 551, respectively.

[0288] The control circuit 57 has the same function as the control circuit 17 of the first embodiment, and a circuit that controls the FETs 51 and 52.

[0289] The control circuit 57 includes a switching transition time detection circuit 570, a controller 571, drive circuits 572 and 573, and an isolation circuit 574.

[0290] The switching transition time detection circuit 570 is a circuit that first commands a drive signal output from the controller 571 to the FET 52 to turn off the FET 52, and thereafter outputs a pulse signal whose level is maintained until the voltage between the source and drain of the FET 51 reaches the threshold voltage Vth.

[0291] The switching transition time detection circuit 570 is connected to the controller 571 to obtain the drive signal for the FET 52.

[0292] In addition, the switching transition time detection circuit 570 is connected to the source and drain of the FET 51, respectively, to detect the voltage between the source and drain of the FET 51.

[0293] Further, the switching transition time detection circuit 570 is connected to the controller 571 to output a pulse signal of a detected result to the controller 571.

[0294] The controller 571 and the drive circuits 572 and 573 have the same functions and structures as the controller 171 of the first embodiment and the drive circuits 172 and 173.

[0295] The isolation circuit 574 is a circuit that outputs the output voltage Vout of the electric power converter 5 to the controller 571 in an isolated state.

[0296] One input end of the isolation circuit 574 is connected to one end of the smoothing capacitor 56, and another end of the isolation circuit 574 is connected to the controller 571, respectively.

[0297] The following is based on Fig. 15 an operation of the electric power converter of the fifth embodiment is explained.

[0298] The switching transition time detection circuit 570, which is Fig. 15 outputs the pulse signal whose level is maintained until the voltage between the source and drain of the FET 51 reaches the threshold voltage Vth after the FET 52 is commanded the drive signal to turn off the FET 52.

[0299] The controller 571, like the controller 171 of the first embodiment, obtains the switching transition time from the pulse signal output by the switching transition time detection circuit 570, and generates and outputs the drive signals for the FETs 51 and 52 based on the target output voltage value Vout*, the input and output voltages Vin and Vout, and the switching transition time.

[0300] The drive circuits 572 and 573 turn on and off the FETs 51 and 52, respectively, based on the drive signal.

[0301] Accordingly, as in the electric power converter 1 of the first embodiment, the switching transition time is controlled to the target switching transition time value. That is, the reactor current IL is controlled to the optimal value.

[0302] Therefore, the electric power converter 1, which supplies electric power from the high-voltage battery B10 to the low-voltage battery B11, can be controlled in the current critical mode without detecting a reactor current.

[0303] Effects of the electric power converter of the fifth embodiment will be explained below.

[0304] According to the fifth embodiment, even in an electric power converter 5 which is a flyback converter, the same effects as in the first embodiment can be obtained.

[0305] In addition, although the FETs 51 and 52 are controlled based on the target output voltage value Vout*, the input and output voltages Vin and Vout, and the switching transition time as an example in the fifth embodiment, they are not limited to such a structure.

[0306] The FETs 51 and 52 can be controlled as in the electric power converter 4 of the fourth embodiment, further taking into account the desired output current value Iout* and the output current Iout.

[0307] The same effects as those of the fourth embodiment can also be obtained in the electric power converter 5 which is a flyback converter. (Comparative example)

[0308] The electrical power converter of the comparative example is explained below.

[0309] The electric power converter of the comparative example changes a structure of a controller with respect to the electric power converter of the first embodiment.

[0310] First, with reference to Fig. 16 and Fig. 17 a structure of the electrical power converter of a comparative example is explained.

[0311] As in Fig. As shown in FIG. 16, an electric power converter 6 is a device that converts a direct current supplied from a high-voltage battery B60 (power source) mounted in a vehicle into a low-voltage direct current, and supplies it to a low-voltage battery B61 (load) mounted in a vehicle to charge the low-voltage battery B61. It is a so-called step-down type boost / step-down converter.

[0312] Here, the high-voltage battery B60 and the low-voltage battery B61 are the same as the high-voltage battery B10 and the low-voltage battery B11 of the first embodiment.

[0313] The electrical power converter 6 has a smoothing capacitor 60, an FET 61 (main switch), an FET 62 (synchronous rectification switch), noise suppression circuits 63 and 64, a choke coil 65, a smoothing capacitor 66 and a control circuit 67.

[0314] The structures and functions of the smoothing capacitor 60, the FETs 63 and 64, the noise suppression circuits 63 and 64, the choke coil 65, and the smoothing capacitor 66 are the same as the functions and structures of the smoothing capacitor 10, the FETs 11 and 12, the noise suppression circuits 13 and 14, the choke coil 15, and the smoothing capacitor 16 of the first embodiment.

[0315] The control circuit 67 is a circuit that controls the FETs 61 and 62. The control circuit 67 controls the FETs 61 and 62 based on a target output voltage value Vout* of the electric power converter 6 input from the outside, a detected output voltage Vout of the electric power converter, and a switching transition time.

[0316] Unlike the control circuit 17 of the first embodiment, an input voltage of the electric power converter 6 is not fed back when the FETs 61 and 62 are controlled.

[0317] Here, the switching transition time is a time required for the voltage between the source and drain of the FET 61 to reach a threshold voltage Vth after the FET 62 is commanded to be turned off, and is designed similarly to that of the first embodiment.

[0318] The control circuit 67 includes a switching transition time detection circuit 670, a controller 671, and drive circuits 672 and 673.

[0319] The switching transition time detection circuit 670 has the same function and structure as the switching transition time detection circuit 170 of the first embodiment.

[0320] Controller 671 is a circuit that generates and outputs the drive signals of FETs 61 and 62 based on the target output voltage value Vout*, the output voltage Vout, and the switching transition time. Controller 671 is composed of a microcomputer and a program.

[0321] As in Fig. As shown in Fig. 17, the controller 671 includes a deviation calculation section 671o, a voltage control section 671p, a switching transition time measuring section 671q, a deviation calculation section 671r, a switching transition time control section 671s, an ON-time calculation section 671t, and a drive signal generation section 671u.

[0322] The deviation calculation section 671o is a block that calculates and outputs a deviation of the target output voltage value Vout* of the electric power converter 6, which is input from the outside, from the actual output voltage Vout.

[0323] The voltage control section 671p is a block that outputs a value as an ON-time ratio for the FETs 61 and 62 by performing a proportional integral calculation of the deviation of the target output voltage value Vout* output by the deviation calculation section 671o from the actual output voltage Vout.

[0324] The switching transition time measuring section 671q and the deviation calculating section 671r each have the same functions and structures as the switching transition time measuring section 171b and the deviation calculating section 171c of the first embodiment.

[0325] The switching transition time control section 671s is a block that outputs a value as a switching duration by performing a proportional integral calculation of the deviation of the target switching transition time value output by the deviation calculation section 671r from the actual switching transition time.

[0326] Here, the switching duration is a time between consecutive commands to turn on the FET 61.

[0327] In addition, the switching times are also a time between consecutive commands to turn on the FET 62.

[0328] The ON-time calculation section 671t is a block that calculates and outputs the ON time of the FETs 61 and 62 based on the ON time ratio output by the voltage control section 671p and the switching period output by the switching transition time control section 671s.

[0329] The drive signal generating section 671u is a block that generates and outputs the drive signal for driving the FETs 61 and 62 based on the ON times of the FETs 61 and 62 output from the ON time calculating section 671t.

[0330] The control circuits 672 and 673, which are Fig. 16 have the same functions and structures as the drive circuits 172 and 173 of the first embodiment.

[0331] The following is based on Fig. 16 and Fig. 17 an operation of the electrical power converter of the comparative example is explained.

[0332] Since the operation of the switching transition time detection circuit 670 shown in Fig. 16 is the same as the operation of the switching transition time detection circuit 170 of the first embodiment, an explanation will be omitted.

[0333] The operating modes of the controllers and the control circuits are explained.

[0334] The deviation calculation section 671o, which is Fig. 17, calculates the deviation of the target output voltage value Vout* from the actual output voltage Vout and outputs it.

[0335] The voltage control section 671p outputs a value as the ON-time ratio of the FETs 61 and 62 by performing a proportional integral calculation of the deviation of the target output voltage value Vout* from the actual output voltage Vout.

[0336] The switching transition time measuring section 671q obtains the switching transition time by measuring a pulse width of a pulse signal output by the switching transition time detecting circuit 670.

[0337] The deviation calculating section 671r calculates the deviation of the predetermined target switching transition time value from the actual switching transition time.

[0338] The switching transition time control section 671s outputs a value as a switching duration by performing a proportional integral calculation of the deviation of the target switching transition time value from the actual switching transition time.

[0339] The switching transition time control section 671s shortens the switching time when the reactor current IL in the negative direction is larger than the optimal value.

[0340] On the other hand, the switching transition time control section 671s extends the switching time when the reactor current IL in the negative direction is smaller than the optimal value.

[0341] The ON-time calculation section 671t calculates and outputs the ON time of the FETs 61 and 62 based on the ON time ratio and the switching duration.

[0342] The drive signal generating section 671u generates and outputs the drive signal for driving the FETs 61 and 62 based on the ON time for the FETs 61 and 62.

[0343] The control circuits 672 and 673, which are Fig. 16, the FETs 61 and 62 turn on and off based on the drive signal, respectively.

[0344] When the switching time becomes short, a period in which the reactor current II is negative becomes short, and the reactor current IL in the negative direction becomes small.

[0345] On the other hand, when the switching time becomes long, the period in which the reactor current IL is negative is long, and the reactor current IL in the negative direction becomes large.

[0346] As a result, the switching transition time is controlled to the target switching transition time value. This means that the inductor current IL is controlled to the optimal value.

[0347] Therefore, the electric power converter 6, which supplies electric power from the high-voltage battery B60 to the low-voltage battery B61, can be controlled in the current critical mode without detecting a reactor current.

[0348] The effects of the electrical power converter of the comparative example are explained below.

[0349] According to the comparative example, as in the first embodiment, the electric power converter 6, which is a boost / buck converter, can be controlled in the current critical mode without detecting a reactor current. Furthermore, switching loss can be suppressed.

[0350] According to the comparative example, the control circuit 67 obtains the ON-time ratio based on the deviation of the target output voltage value Vout* from the actual output voltage Vout, while obtaining the switching duration based on the deviation of the target switching transition time value from the actual switching transition time, and controls the FETs 61 and 62 based on the obtained ON-time ratio and the switching duration.

[0351] Therefore, the switching transition time can be controlled to the target switching transition time value, while the output voltage Vout can be controlled to the target output voltage value Vout*.

[0352] According to the comparative example, the control circuit 67 acquires the ON time based on the ON time ratio and the switching duration, and controls the FETs 61 and 62 based on the acquired ON time.

[0353] Therefore, the ON time can be reliably obtained, and the FETs 61 and 62 can be reliably controlled based on the ON time. (Another comparative example)

[0354] Below is the electrical power converter of the further comparative example.

[0355] With respect to the electric power converter of the comparative example, the electric power converter of the further comparative example detects an output current and controls the FET based on the detected output current.

[0356] First, with reference to Fig. 18 and Fig. 19 a structure of the electrical power converter of the further comparative example is explained.

[0357] An electrical power converter 7, which is Fig. 18 is a device that converts a direct current supplied from a high-voltage battery B70 (power supply) mounted in a vehicle into a low-voltage direct current, and supplies it to a low-voltage battery B71 (load) mounted in the vehicle to charge the low-voltage battery B71. It is a so-called buck-type boost / buck converter.

[0358] The electrical power converter 7 has a smoothing capacitor 70, an FET 71 (main switch), an FET 72 (synchronous rectification switch), noise suppression circuits 73 and 74, a choke coil 75, a smoothing capacitor 76 and a control circuit 77.

[0359] The electrical power converter 7 further comprises a current sensor 78.

[0360] The structures and functions of the smoothing capacitor 70, the FETs 71 and 72, the noise suppression circuits 73 and 74, the choke coil 75, and the smoothing capacitor 76 are the same as the functions and structures of the smoothing capacitor 60, the FETs 61 and 62, the noise suppression circuits 63 and 64, the choke coil 65, and the smoothing capacitor 66 of the comparative example.

[0361] The current sensor 78 is an element that detects an output current Iout of the electric power converter 7. The current sensor 78 is arranged in a wiring that connects one end of the reactor 75 and a positive terminal of the low-voltage battery B71, and is connected to the control circuit 77.

[0362] The control circuit 77 is a circuit that controls the FETs 71 and 72. The control circuit 77 controls the FETs 71 and 72 based on a target output voltage value Vout* and a target output current value Iout* of the electric power converter 7 input from the outside, detected input and output voltages Vin and Vout, and an output current value Iout of the electric power converter 7, and a switching transition time.

[0363] Here, the switching transition time is a time required for the voltage between the source and drain of the FET 71 (cross-connection voltage) to reach a threshold voltage Vth after the FET 72 is commanded to turn off, and is designed similarly to that of the first embodiment.

[0364] The control circuit 77 includes a switching transition time detection circuit 770, a controller 771, and drive circuits 772 and 773.

[0365] The switching transition time detection circuit 770 has the same function and structure as the switching transition time detection circuit 670 of the comparative example.

[0366] Controller 771 is a circuit that generates and outputs the drive signals of FETs 71 and 72 based on the target output voltage value Vout*, the target output current value Iout*, the input and output voltages Vin and Vout, the output current value Iout, and the switching transition time. Controller 771 is implemented by a microcomputer and a program.

[0367] As in Fig. 19, the controller 771 includes a deviation calculation section 771o, a voltage control section 771p, a switching transition time measuring section 771q, a deviation calculation section 771r, a switching transition time control section 771s, an ON-time calculation section 771t, and a drive signal generation section 771u.

[0368] Further, the controller 771 includes a selection section 771v, a deviation calculation section 771w, and a current control section 771x.

[0369] The deviation calculation section 771o has the same function and structure as the deviation calculation section 671o of the comparative example.

[0370] The voltage control section 771p is a block that outputs a value as a target output current value by performing a proportional integral calculation of the deviation of the target output voltage value Vout* calculated by the deviation calculation section 771o from the actual output voltage Vout.

[0371] The selecting section 771v is a block that selects a smaller one than a new target output current value among the target output current value output by the voltage control section 771p and the target output current value Iout* input from the outside and outputs it.

[0372] The deviation calculation section 771w is a block that calculates the deviation of the new target output current value output by the selection section 771v from the actual output current Iout of the electric power converter 7 detected by the current sensor 78.

[0373] The current control section 771x is a block that outputs a value as an ON-time ratio for the FETs 71 and 72 by performing a proportional integral calculation of a deviation of the new target output current value that the deviation calculation section 771w outputs from the actual output current Iout.

[0374] The switching transition time measuring section 771q, the deviation calculating section 771r, and the switching transition time control section 771s have the same functions and structures as the switching transition time measuring section 671q, the deviation calculating section 671r, and the switching transition time control section 671s of the comparative example.

[0375] The ON-time calculation section 771t is a block that calculates and outputs the ON time for the FETs 71 and 72 based on the ON-time ratio output by the voltage control section 771x and the switching period output by the switching transition time control section 771s.

[0376] The drive signal generating section 771u is a block that generates and outputs the drive signal for driving the FETs 71 and 72 based on the ON times for the FETs 71 and 72 output from the ON time calculating section 771t.

[0377] The control circuits 772 and 773, which are Fig. 18 have the same functions and structures as the drive circuits 672 and 673 of the comparative example.

[0378] The following are provided with reference to Fig. 18 and Fig. 19 Operating modes of the electrical power converter are explained in the further comparative example.

[0379] Since the operation of the switching transition time detection circuit 770, which is Fig. 18 is the same as the operation of the switching transition time detection circuit 670 of the comparative example, an explanation will be omitted.

[0380] The operation of the controller and the control circuit are explained.

[0381] The voltage control section 771p, which is Fig. 19, outputs the value as the target output current value by performing a proportional integral calculation of the deviation of the target output voltage value Vout* from the actual output voltage Vout.

[0382] The selecting section 771v selects the smaller one as the new target output current value among the target output current value output by the voltage control section 771p and the target output current value Iout* input from the outside and outputs it.

[0383] The deviation calculation section 771w calculates and outputs the deviation of the new target output current value from the actual output current Iout.

[0384] The current control section 771x outputs the value as the new ON-time ratio for the FETs 71 and 72 by performing the proportional integral calculation of the deviation of the new target output current value from the actual output current Iout.

[0385] That is, unlike the controller 671 of the comparative example, the ON time ratio for the FETs 71 and 72 is calculated taking into account the target output current value and the output current.

[0386] The ON-time calculation section 771t calculates and outputs the ON time for the FETs 71 and 72 based on the ON time ratio and the switching duration.

[0387] The drive signal generating section 771u generates and outputs the drive signal for driving the FETs 71 and 72 based on the ON time for the FETs 71 and 72.

[0388] The control circuits 772 and 773, which are Fig. 18, the FETs 71 and 72 turn on and off based on the drive signal, respectively.

[0389] As a result, the switching transition time is controlled to the target switching transition time value. This means that the inductor current IL is controlled to the optimal value.

[0390] Therefore, the electric power converter 7, which supplies electric power from the high-voltage battery B70 to the low-voltage battery B71, can be controlled in the current critical mode without detecting a reactor current.

[0391] Below, effects of the electrical power converter of the further comparative example are explained.

[0392] According to the further comparative example, as in the comparative example, the electric power converter 7, which is a boost / buck converter, can be controlled in the current critical mode without detecting a reactor current. Furthermore, switching loss can be suppressed.

[0393] According to the further comparative example, the control circuit 77 controls the FETs 71 and 72 based on the deviation of the target output current value Vout* from the actual output voltage Vout, the target output current value Iout* and the output current value Iout.

[0394] Therefore, the output voltage Vout can be controlled to the target output voltage value Vout*, and the output current value Iout can be controlled to the target output current value Iout*.

[0395] According to the further comparative example, the control circuit 77 selects a smaller one as a new target output current value among the target output current value obtained based on the deviation of the target output voltage value Vout* and the output voltage Vout and the actual target output current value Iout* input from the outside, and controls the FETs 71 and 72 based on the deviation of a new target output current value from the actual output current Iout.

[0396] Therefore, the output voltage Vout can be reliably controlled to the target output voltage value Vout*, and the output current value Iout can be reliably controlled to the target output current value Iout*.

Claims

[1] Electrical power converter, comprising: a choke coil (15, 25, 35, 45, 55); a main switch (11, 22, 31, 32, 41, 51) that connects a power supply to the choke coil (15, 25, 35, 45, 55) by being turned on, and supplies current from the power supply to the choke coil (15, 25, 35, 45, 55) to store energy in the choke coil (15, 25, 35, 45, 55); a synchronous rectification switch (12, 21, 32, 31, 42, 52) connecting the choke coil (15, 25, 35, 45, 55) to a load by being switched on during a period in which the main switch (11, 22, 31, 32, 41, 51) is switched off, and releasing the energy stored in the choke coil (15, 25, 35, 45, 55) to supply the current from the choke coil (15, 25, 35, 45, 55) to the load; and a control circuit (17, 27, 37, 47, 57) connected to the main switch (11, 22, 31, 32, 41, 51) and the synchronous rectification switch (12, 21, 32, 31, 42, 52) and controlling the main switch (11, 22, 31, 32, 41, 51) and the synchronous rectification switch (12, 21, 32, 31, 42, 52); wherein the control circuit (17, 27, 37, 47, 57) detects a switching transition time indicating a transition state of a cross-connection voltage of the main switch (11, 22, 31, 32, 41, 51), and controls the main switch (11, 22, 31, 32, 41, 51) and the synchronous rectification switch (12, 21, 32, 31, 42, 52) based on the detected switching transition time, wherein the control circuit (17, 27, 37, 47, 57) controls the main switch (11, 22, 31, 32, 41, 51) and the synchronous rectification switch based on a target output voltage value, an output voltage and a deviation of a target switching transition time value from the actual switching transition time, and the control circuit (17, 27, 37, 47, 57) corrects the ON-time ratio obtained based on an input voltage and an output voltage by an ON-time ratio correction value obtained based on the deviation of the target switching transition time value from the actual switching transition time, and controls the main switch (11, 22, 31, 32, 41, 51) and the synchronous rectification switch based on the corrected ON-time ratio. [2] An electric power converter according to claim 1, wherein the control circuit (17, 27, 37, 47, 57) controls the main switch (11, 22, 31, 32, 41, 51) and the synchronous rectification switch (12, 21, 32, 31, 42, 52) based on a deviation of the target output voltage value from the actual output voltage. [3] An electric power converter according to claim 2, wherein the control circuit (17, 27, 37, 47, 57) converts an ON-time ratio corrected based on the deviation of the target output voltage value from the actual output voltage into the ON-time, and controls the main switch (11, 22, 31, 32, 41, 51) and the synchronous rectification switch (12, 21, 32, 31, 42, 52) based on the converted ON-time. [4] An electric power converter according to any one of claims 1 to 3, wherein the control circuit (47) controls the main switch (41) and the synchronous rectification switch (42) based on a deviation of the target output voltage value from the actual output voltage, a target output current value input from the outside, and an output current. [5] An electric power converter according to claim 4, wherein the control circuit (47) selects a smaller one than a new target output current value among the output current value obtained based on the deviation of the target output voltage value from the actual output voltage and the target output current value input from the outside, and controls the main switch (41) and the synchronous rectification switch (42) based on the deviation of the new target output current value from the actual output current. [6] An electric power converter according to any one of claims 1 to 5, wherein the switching transition time is a time required for the cross-connection voltage of the main switch (11, 22, 31, 32, 41, 51) to reach a threshold voltage after the synchronous rectification switch (12, 21, 32, 31, 42, 52) is commanded to turn off. [7] Electrical power converter according to one of claims 1 to 6, wherein the main switch (11, 22, 31, 32, 41) and the synchronous rectification switch (12, 21, 32, 31, 42) are connected in series; one end of the main switch (11, 22, 31, 32, 41) is connected to the power supply; one end of the synchronous rectification switch (12, 21, 32, 31, 42) is connected to the load; and a series connection point of the main switch (11, 22, 31, 32, 41) and the synchronous rectification switch (12, 21, 32, 31, 42) is connected to the choke coil (15, 25, 35, 45). [8] Electrical power converter according to one of claims 1 to 6, wherein the choke coil (55) is a transformer having a primary winding and a secondary winding; one end of the main switch (51) is connected to the power supply and another end of the main switch (51) is connected to the primary winding; and one end of the synchronous rectification switch (52) is connected to the secondary winding and another end of the synchronous rectification switch (52) is connected to the load.

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