Power converter

A synchronization detection PLL section generates an ON synchronized signal formed as a result of synchronization control based on a diode ON synthesized signal. The synchronization detection PLL section also generates an OFF synchronized signal formed as a result of synchronization control based on a diode OFF synthesized signal. A stator gate instruction generator PWM section generates a gate instruction signal for controlling the switching of a switching element on the basis of the ON synchronized signal and the OFF synchronized signal.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a power converter, and in particular, to a vehicle power converter for use in a vehicle rotary motor mounted on a vehicle such as a car.

2. Description of the Related Art

Full-wave rectification using a diode applied as a rectifying element is a generally known system used in a vehicle rotary motor. Meanwhile, a recent rectifying system uses a switching element as a rectifying element to enhance efficiency, and reduces loss generated by the rectifying element.

In a vehicle power converter already suggested, for example, in Patent Document 1, a switching element is used as a rectifying element. In this power converter, ON and OFF of the switching element are controlled on the basis of the rotational position of a rotor of a vehicle rotary motor determined by rotational position detecting means.

In a system suggested, for example, in Patent Document 2, a position signal indicative of the rotational position and the angle of a rotary motor is compared with ON and OFF signals of a diode of each phase in each of higher and lower arms. This determines a time when the diode of this phase is turned on in a next cycle. A switching element of the same phase is turned on at the determined time to predict a time when the diode is turned off. Then, the switching element of the same phase is turned off at a time before the predicted time when the diode is turned off.Patent Document 1: Japanese Patent Application Laid-Open No. 2002-218797Patent Document 2: Japanese Patent Application Laid-Open No. 2008-228450

However, the system for determining the rotational position of a rotor of a vehicle rotary motor by using rotational position detecting means to make phase control in the ON-OFF operation of a switching element cannot respond to the need to change a time when the switching element is turned on or off in real time in response to load variations.

In order to determine the rotational position of a rotor of a vehicle rotary motor, a rotational position sensor or an angle sensor typified by a resolver should be attached to the shaft of the rotary motor, or, an RD converter for converting the output of a sensor to data of a rotational position or an angle should be prepared.

External noise may be superimposed on a position signal depending on the degree of accuracy in attaching a rotational position sensor such as a resolver, as a result of enhanced efficiency in synchronous rectification in fast-speed rotation caused by the response characteristic delay of an RD converter, or depending on the response characteristic of an RD converter in a noise region. As a result, chattering may be caused when a switching element is turned on, or, a switching element may be turned on in a period during which the switching element should be off, leading to variations in load torque of a rotary motor.

Turning a switching element on in a period during which the switching element should be off may result in the following. A current flows in a direction opposite to its original direction at the time of generation of electricity, or a short circuit is generated depending on a time when the switching element is turned on, or a period during which the switching element is on. These will cause large variations or drop in output voltage of a power source.

The following way is regarded as a simple process if attention is focused only on one phase. In this system, a position signal indicative of the rotational position and the angle of a rotary motor is compared with ON and OFF signals of a diode of each phase in each of higher and lower arms. This determines a time when the diode of this phase is turned on in a next cycle. A switching element of the same phase is turned on at the determined time to predict a time when the diode is turned off. Then, the switching element of the same phase is turned off at a time before the predicted time when the diode is turned off. However, an actual situation of this way is that a check should be made to see whether ON and OFF of a diode are detected in correct order in six phases including three phases in each of higher and lower arms.

This check requires the following determinations for each cycle: a determination as to whether the ON and OFF cycles of diodes of the six phases are substantially the same; a determination as to whether turning-on of a diode is detected precisely in U, V, and W phases in this order, in such a way that a phase difference is about 120 degrees in terms of electrical angle; a determination as to whether detection of turning-on of diodes is shifted 180 degrees in terms of electrical angle between higher and lower arms of the same phase; and a determination as to whether a period of time during which a switching element is on is substantially the same in the six phases. This check places a heavy burden on the process.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, a power converter includes 2N (N is an integer no less than two) switching elements of N phases provided in each of higher and lower arms, 2N freewheeling diodes connected in parallel with corresponding ones of the 2N switching elements, a diode conducting state detector for determining times when the 2N freewheeling diodes are turned on and off, an ON PLL circuit for generating an ON synchronized signal formed as a result of synchronization control based on the times determined by the diode conducting state detector when the 2N freewheeling diodes are turned on, an OFF PLL circuit for generating an OFF synchronized signal formed as a result of synchronization control based on the times determined by the diode conducting state detector when the 2N freewheeling diodes are turned off, and a gate instruction generator PWM section for generating a gate instruction signal, which controls switching of the switching elements, on the basis of the ON synchronized signal and the OFF synchronized signal.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of a power converter according to the invention are described below in detail on the basis of the drawings. The embodiments are not intended to limit the scope of the invention.

First Embodiment

FIG. 1is a block diagram showing the schematic configuration of a power converter of a first embodiment of the invention.FIG. 2is a block diagram showing an example of the schematic configuration of a power converter unit shown inFIG. 1. In the description below, a U-phase higher arm is called a UH phase, a U-phase lower arm is called a UL phase, a V-phase higher arm is called a VH phase, a V-phase lower arm is called a VL phase, a W-phase higher arm is called a WH phase, and a W-phase lower arm is called a WL phase. The higher and lower arms of each of the three phases including the U, V, and W phases are distinguished from each other, so that six obtained by multiplying two by three is the total number of phases.

With reference toFIG. 1, the power converter includes a power converter unit11and a gate control unit120. The power converter unit11performs power conversion on the basis of a stator gate instruction signal S16generated by the gate control unit120. The gate control unit120generates the stator gate instruction signal S16on the basis of a voltage detection signal S11given from the power converter unit11.

As shown inFIG. 2, the power converter unit11includes a three-phase armature winding313placed on a stator, and a field winding314placed on a rotor that form a rotary motor.

The power converter unit11includes positive terminals P and FP, and negative terminals N and FN. The positive terminals P and FP are connected to the positive pole of a storage battery44, and the negative terminals N and FN are connected to the negative pole of the storage battery44. The storage battery44may be replaced by a capacitor. A DC load voltage may be applied as a positive voltage VP of the storage battery44. A ground voltage may be applied as a negative voltage VN of the storage battery44.

The stator has a U-phase higher-arm switching element (hereinafter called UH element)31, a U-phase lower-arm switching element (hereinafter called UL element)33, a V-phase higher-arm switching element (hereinafter called VH element)35, a V-phase lower-arm switching element (hereinafter called VL element)37, a W-phase higher-arm switching element (hereinafter called WH element)39, and a W-phase lower-arm switching element (hereinafter called WL element)311.

IGBTs, bipolar transistors, or field-effect transistors may be used as the UH element31, the UL element33, the VH element35, the VL element37, the WH element39, and the WL element311.

A U-phase higher-arm freewheeling diode (hereinafter called UH diode)32is connected in parallel with the UH element31. A U-phase lower-arm freewheeling diode (hereinafter called UL diode)34is connected in parallel with the UL element33. A V-phase higher-arm freewheeling diode (hereinafter called VH diode)36is connected in parallel with the VH element35. A V-phase lower-arm freewheeling diode (hereinafter called VL diode)38is connected in parallel with the UL element37. A W-phase higher-arm freewheeling diode (hereinafter called WH diode)310is connected in parallel with the WH element39. A W-phase lower-arm freewheeling diode (hereinafter called WL diode)312is connected in parallel with the WL element311.

The UH element31, the UL element33, the VH element35, the VL element37, the WH element39, and the WL element311form a three-phase bridge circuit. A connection point between the UH element31and the UL element33is connected to the U-phase terminal of the armature winding313. A connection point between the VH element35and the VL element37is connected to the V-phase terminal of the armature winding313. A connection point between the WH element39and the WL element311is connected to the W-phase terminal of the armature winding313. By doing so, the evenly spaced UH element31, UL element33, VH element35, VL element37, WH element39, and WL element311are connected in a circle to the motor.

A connection point among the UH element31, the VH element35, and the WH element39is connected through a stator gate driver315to the positive terminal P. A connection point among the UL element33, the VL element37, and the WL element311is connected through the stator gate driver315to the negative terminal N.

The stator has the stator gate driver315and a three-phase phase voltage detector318. The stator gate driver315drives the gates of the UH element31, the UL element33, the VH element35, the VL element37, the WH element39, and the WL element311on the basis of the stator gate instruction signal S16, thereby switching the UH element31, the UL element33, the VH element35, the VL element37, the WH element39, and the WL element311on and off.

The three-phase phase voltage detector318detects a positive terminal voltage Vp to be applied to the connection point among the UH element31, the VH element35, and the WH element39, and a negative terminal voltage Vn to be applied to the connection point among the UL element33, the VL element37, and the WL element311. The three-phase phase voltage detector318also detects a U-phase induction voltage Vu generated at the connection point between the UH element31and the UL element33, a V-phase induction voltage Vv generated at the connection point between the VH element35and the VL element37, and a W-phase induction voltage Vw generated at the connection point between the WH element39and the WL element311. Then, the three-phase phase voltage detector318can output the resultant voltages as the voltage detection signal S11.

The rotor has a field switching element324responsible for PWM (pulse width modulation) control of a field current. A freewheeling diode326is connected in parallel with the field switching element324. An IGBT, a bipolar transistor, or a field-effect transistor may be used as the field switching element324.

A diode325is connected between electric wires as a pair connected to opposite ends of the field switching element324. The field switching element324is placed in one of the electric wires, and a resistor30is placed in the other of the electric wires.

The rotor has a rotor gate driver317, a rotor gate instruction generator319, and a rotor current detector320. The rotor current detector320can output a detected value irotof a rotor current on the basis of a voltage across the resistor30. The rotor gate instruction generator319can generate a rotor gate instruction signal S21on the basis of the detected value irotof a rotor current. The rotor gate driver317can drive the gate of the field switching element324on the basis of the rotor gate instruction signal S21, thereby turning the field switching element324on and off.

FIG. 2shows the three-phase field winding power generator motor including the three-phase armature winding313placed on the stator, and the field winding314placed on the rotor. However, a different number of phases and a different field system are applicable. As an example, a permanent magnet system is applicable. Furthermore, the power generator motor is not necessarily part of an integrated structure in which the motor is integrated with the power converter unit11. The power generator motor may be formed as a separate unit. More specifically, the three-phase armature winding313and the field winding314placed on the rotor in the power converter unit11may be physically separated from the other constituent elements.

As shown inFIG. 1, the gate control unit120includes a diode conducting state detector12, a synchronization detection PLL section13, a cycle checker14, a stator gate instruction generator PWM section15, a diode ON signal synthesizer (hereinafter called Don signal synthesizer)12g, and a diode OFF signal synthesizer (hereinafter called Doff signal synthesizer)12g′.

The diode conducting state detector12can determine times when each of the six diodes shown inFIG. 2including the UH diode32, the UL diode34, the VH diode36, the VH diode38, the WH diode310, and the WL diode312is turned on and off.

The diode conducting state detector12may include a U-phase higher-arm diode ON signal detector (hereinafter called UH-phase Don signal detector)12a, a U-phase lower-arm diode ON signal detector (hereinafter called UL-phase Don signal detector)12b, a V-phase higher-arm diode ON signal detector (hereinafter called VH-phase Don signal detector)12c, a V-phase lower-arm diode ON signal detector (hereinafter called VL-phase Don signal detector)12d, a W-phase higher-arm diode ON signal detector (hereinafter called WH-phase Don signal detector)12e, and a W-phase lower-arm diode ON signal detector (hereinafter called WL-phase Don signal detector)12f. The diode conducting state detector12may also include a U-phase higher-arm diode OFF signal detector (hereinafter called UH-phase Doff signal detector)12a′, a U-phase lower-arm diode OFF signal detector (hereinafter called UL-phase Doff signal detector)12b′, a V-phase higher-arm diode OFF signal detector (hereinafter called VH-phase Doff signal detector)12c′, a V-phase lower-arm diode OFF signal detector (hereinafter called VL-phase Doff signal detector)12d′, a W-phase higher-arm diode OFF signal detector (hereinafter called WH-phase Doff signal detector)12e′, and a W-phase lower-arm diode OFF signal detector (hereinafter called WL-phase Doff signal detector)12f′.

The UH-phase Don signal detector12acan output a U-phase higher-arm diode ON detection signal (hereinafter called UH-phase Don detection signal) S12uhon the basis of a time when the UH diode32is turned on.

The UL-phase Don signal detector12bcan output a U-phase lower-arm diode ON detection signal (hereinafter called UL-phase Don detection signal) S12ulon the basis of a time when the UL diode34is turned on.

The VH-phase Don signal detector12ccan output a V-phase higher-arm diode ON detection signal (hereinafter called VH-phase Don detection signal) S12vhon the basis of a time when the VH diode36is turned on.

The VL-phase Don signal detector12dcan output a V-phase lower-arm diode ON detection signal (hereinafter called VL-phase Don detection signal) S12vlon the basis of a time when the VL diode38is turned on.

The WH-phase Don signal detector12ecan output a W-phase higher-arm diode ON detection signal (hereinafter called WH-phase Don detection signal) S12whon the basis of a time when the WH diode310is turned on.

The WL-phase Don signal detector12fcan output a W-phase lower-arm diode ON detection signal (hereinafter called WL-phase Don detection signal) S12wlon the basis of a time when the WL diode312is turned on.

The UH-phase Doff signal detector12a′ can output a U-phase higher-arm diode OFF detection signal (hereinafter called UH-phase Doff detection signal) S12uh′ on the basis of a time when the UH diode32is turned off.

The UL-phase Doff signal detector12b′ can output a U-phase lower-arm diode OFF detection signal (hereinafter called UL-phase Doff detection signal) S12ul′ on the basis of a time when the UL diode34is turned off.

The VH-phase Doff signal detector12c′ can output a V-phase higher-arm diode OFF detection signal (hereinafter called VH-phase Doff detection signal) S12vh′ on the basis of a time when the VH diode36is turned off.

The VL-phase Doff signal detector12d′ can output a V-phase lower-arm diode OFF detection signal (hereinafter called VL-phase Doff detection signal) S12vl′ on the basis of a time when the VL diode38is turned off.

The WH-phase Doff signal detector12e′ can output a W-phase higher-arm diode OFF detection signal (hereinafter called WH-phase Doff detection signal) S12wh′ on the basis of a time when the WH diode310is turned off.

The WL-phase Doff signal detector12f′ can output a W-phase lower-arm diode OFF detection signal (hereinafter called WL-phase Doff detection signal) S12wl′ on the basis of a time when the WL diode312is turned off.

As an example, synchronous counters may be used as the UH-phase Don signal detector12a, the UL-phase Don signal detector12b, the VH-phase Don signal detector12c, the VL-phase Don signal detector12d, the WH-phase Don signal detector12e, the WL-phase Don signal detector12f, the UH-phase Doff signal detector12a′, the UL-phase Doff signal detector12b′, the VH-phase Doff signal detector12c′, the VL-phase Doff signal detector12d′, the WH-phase Doff signal detector12e′, and the WL-phase Doff signal detector12f′.

Synchronous counters continue to detect ON or OFF of diodes in a predetermined period of time, so that a check can be made to see whether diodes are on or off. As a result, false detection caused by mixing of noises can be reduced.

The Don signal synthesizer12gsynthesizes the UH-phase Don detection signal S12uh, the UL-phase Don detection signal S12ul, the VH-phase Don detection signal S12vh, the VL-phase Don detection signal S12vl, the WH-phase Don detection signal S12wh, and the WL-phase Don detection signal S12wlin the same temporal sequence. As a result, a diode ON synthesized signal S12can be generated.

The Doff signal synthesizer12g′ synthesizes the UH-phase Doff detection signal S12uh′, the UL-phase Doff detection signal S12ul′, the VH-phase Doff detection signal S12vh′, the VL-phase Doff detection signal S12vl′, the WH-phase Doff detection signal S12wh′, and the WL-phase Doff detection signal S12wl′ in the same temporal sequence, thereby generating a diode OFF synthesized signal S12′.

As an example, six-input OR circuits may be used as the Don signal synthesizer12gand the Doff signal synthesizer12g′. Or, the Don signal synthesizer12gmay be formed by providing commonality of the outputs of the UH-phase Don signal detector12a, the UL-phase Don signal detector12b, the VH-phase Don signal detector12c, the VL-phase Don signal detector12d, the WH-phase Don signal detector12e, and the WL-phase Don signal detector12fvia a buffer. Further, the Doff signal synthesizer12g′ may formed by providing commonality of the outputs of the UH-phase Doff signal detector12a′, the UL-phase Doff signal detector12b′, the VH-phase Doff signal detector12c′, the VL-phase Doff signal detector12d′, the WH-phase Doff signal detector12e′, and the WL-phase Doff signal detector12f′ via a buffer.

The synchronization detection PLL section13can generate an ON synchronized signal S13formed as a result of synchronization control based on the diode ON synthesized signal S12. The synchronization detection PLL section13can also generate an OFF synchronized signal S13′ formed as a result of synchronization control based on the diode OFF synthesized signal S12′.

The ON synchronized signal S13and the OFF synchronized signal S13′ can be generated separately. More specifically, the synchronization detection PLL section13may include an ON PLL circuit121and an OFF PLL circuit122. The ON PLL circuit121can generate the ON synchronized signal S13formed as a result of synchronization control based on the diode ON synthesized signal S12. The OFF PLL circuit122can generate the OFF synchronized signal S13′ formed as a result of synchronization control based on the diode OFF synthesized signal S12′.

FIG. 3is a block diagram showing an example of a phase-locked loop circuit used in the power converter shown inFIG. 1. A phase-locked loop circuit51shown inFIG. 3includes a 1/n divider52, a phase comparator53, a PI controller54, and a voltage control oscillator55. The PI controller54may be replaced by a low-pass filter.

An oscillation signal ω•generated by the voltage control oscillator55is divided by n (n is a positive integer) by the 1/n divider52, and is then applied to the phase comparator53. The oscillation signal ω•may have a sinusoidal wave W1or a square wave W2. The oscillation signal ω•is compared in phase with a periodic signal Sy applied from outside in the phase comparator53, and a result of comparison is given through the PI controller54to the voltage control oscillator55. As a result, the frequency of the oscillation signal ω•is controlled such that the oscillation signal ω•coincides in phase with the periodic signal Sy. Next, the oscillation signal ω•is integrated by an integrator56, thereby generating a triangular wave signal θ•. Assuming that the frequency of the oscillation signal ω•is f, the oscillation signal ω•is converted to an angular velocity by following the formula ω•=2πf. A resultant angular velocity is integrated by the integrator56, thereby obtaining an estimated output of angular position.

If the phase-locked loop circuit51and the integrator56are used as the ON PLL circuit121shown inFIG. 1, the triangular wave signal θ•can be given as the ON synchronized signal S13by using the diode ON synthesized signal S12as the periodic signal Sy.

If the phase-locked loop circuit51and the integrator56are used as the OFF PLL circuit122shown inFIG. 1, the triangular wave signal θ•can be given as the OFF synchronized signal S13′ by using the diode OFF synthesized signal S12′ as the periodic signal Sy.

With reference toFIG. 1, the cycle checker14compares the UH-phase Don detection signal S12uh, the UL-phase Don detection signal S12ul, the VH-phase Don detection signal S12vh, the VL-phase Don detection signal S12vl, the WH-phase Don detection signal S12wh, and the WL-phase Don detection signal S12wlwith the ON synchronized signal S13. The cycle checker14also compares the UH-phase Doff detection signal S12uh′, the UL-phase Doff detection signal S12ul′, the VH-phase Doff detection signal S12vh′, the VL-phase Doff detection signal S12vl′, the WH-phase Doff detection signal S12wh′, and the WL-phase Doff detection signal S12wl′ with the OFF synchronized signal S13′. As a result, the cycle checker14is allowed to see whether the U-phase induction voltage Vu, the V-phase induction voltage Vv, and the W-phase induction voltage Vw have correct cycles in all the phases, and are detected in correct order in all the phases.

Based on the ON synchronized signal S13and the OFF synchronized signal S13′, the stator gate instruction generator PWM section15can generate the stator gate instruction signal S16for controlling the switching of the UH element31, the UL element33, the VH element35, the VL element37, the WH element39, and the WL element311.

The stator gate instruction generator PWM section15may include a U-phase higher-arm ON triangular wave generator15a, a U-phase higher-arm OFF triangular wave generator15a′, a U-phase higher-arm gate instruction signal generator15a″, a U-phase lower-arm ON triangular wave generator15b, a U-phase lower-arm OFF triangular wave generator15b′, and a U-phase lower-arm gate instruction signal generator15b″. The stator gate instruction generator PWM section15may also include a V-phase higher-arm ON triangular wave generator15c, a V-phase higher-arm OFF triangular wave generator15c′, a V-phase higher-arm gate instruction signal generator15c″, a V-phase lower-arm ON triangular wave generator15d, a V-phase lower-arm OFF triangular wave generator15d′, and a V-phase lower-arm gate instruction signal generator15d″. The stator gate instruction generator PWM section15may also include a W-phase higher-arm ON triangular wave generator15e, a W-phase higher-arm OFF triangular wave generator15e′, a W-phase higher-arm gate instruction signal generator15e″, a W-phase lower-arm ON triangular wave generator15f, a W-phase lower-arm OFF triangular wave generator15f′, and a W-phase lower-arm gate instruction signal generator15f″.

The U-phase higher-arm ON triangular wave generator15acan generate a U-phase higher-arm ON triangular wave (hereinafter called UH-phase ON triangular wave) S15uhon the basis of the ON synchronized signal S13applied in an interval between a time when the UH diode32is turned on last time and a time when the UH diode32is turned on this time that are indicated by the UH-phase Don detection signal S12uh.

The U-phase higher-arm OFF triangular wave generator15a′ can generate a U-phase higher-arm OFF triangular wave (hereinafter called UH-phase OFF triangular wave) S15uh′ on the basis of the OFF synchronized signal S13′ applied in an interval between a time when the UH diode32is turned off last time and a time when the UH diode32is turned off this time that are indicated by the UH-phase Doff detection signal S12uh′.

The U-phase higher-arm gate instruction signal generator15a″ can generate a gate instruction signal S16uhof the UH element31on the basis of a result of comparison between the UH-phase ON triangular wave S15uhand the UH-phase OFF triangular wave S15uh′.

The U-phase lower-arm ON triangular wave generator15bcan generate a U-phase lower-arm ON triangular wave (hereinafter called UL-phase ON triangular wave) S15ulon the basis of the ON synchronized signal S13applied in an interval between a time when the UH diode34is turned on last time and a time when the UL diode34is turned on this time that are indicated by the UL-phase Don detection signal S12ul.

The U-phase lower-arm OFF triangular wave generator15b′ can generate a U-phase lower-arm OFF triangular wave (hereinafter called UL-phase OFF triangular wave) S15ul′ on the basis of the OFF synchronized signal S13′ applied in an interval between a time when the UL diode34is turned off last time and a time when the UL diode34is turned off this time that are indicated by the UL-phase Doff detection signal S12ul′.

The U-phase lower-arm gate instruction signal generator15b″ can generate a gate instruction signal S16ulof the UL element33on the basis of a result of comparison between the UL-phase ON triangular wave S15uland the UL-phase OFF triangular wave S15ul′.

The V-phase higher-arm ON triangular wave generator15ccan generate a V-phase higher-arm ON triangular wave (hereinafter called VH-phase ON triangular wave) S15vhon the basis of the ON synchronized signal S13applied in an interval between a time when the VH diode36is turned on last time and a time when the VH diode36is turned on this time that are indicated by the VH-phase Don detection signal S12vh.

The V-phase higher-arm OFF triangular wave generator15c′ can generate a V-phase higher-arm OFF triangular wave (hereinafter called VH-phase OFF triangular wave) S15vh′ on the basis of the OFF synchronized signal S13′ applied in an interval between a time when the VH diode36is turned off last time and a time when the VH diode36is turned off this time that are indicated by the VH-phase Doff detection signal S12vh′.

The V-phase higher-arm gate instruction signal generator15c″ can generate a gate instruction signal S16vhof the VH element36on the basis of a result of comparison between the VH-phase ON triangular wave S15vhand the VH-phase OFF triangular wave S15vh′.

The V-phase lower-arm ON triangular wave generator15dcan generate a V-phase lower-arm ON triangular wave (hereinafter called VL-phase ON triangular wave) S15vlon the basis of the ON synchronized signal S13applied in an interval between a time when the VL diode38is turned on last time and a time when the VL diode38is turned on this time that are indicated by the VL-phase Don detection signal S12vl.

The V-phase lower-arm OFF triangular wave generator15d′ can generate a V-phase lower-arm OFF triangular wave (hereinafter called VL-phase OFF triangular wave) S15vl′ on the basis of the OFF synchronized signal S13′ applied in an interval between a time when the VL diode38is turned off last time and a time when the VL diode38is turned off this time that are indicated by the VL-phase Doff detection signal S12vl′.

The V-phase lower-arm gate instruction signal generator15d″ can generate a gate instruction signal S16vlof the VL element37on the basis of a result of comparison between the VL-phase ON triangular wave S15vland the VL-phase OFF triangular wave S15vl′.

The W-phase higher-arm ON triangular wave generator15ecan generate a W-phase higher-arm ON triangular wave (hereinafter called WH-phase ON triangular wave) S15whon the basis of the ON synchronized signal S13applied in an interval between a time when the WH diode310is turned on last time and a time when the WH diode310is turned on this time that are indicated by the WH-phase Don detection signal S12wh.

The W-phase higher-arm OFF triangular wave generator15e′ can generate a W-phase higher-arm OFF triangular wave (hereinafter called WH-phase OFF triangular wave) S15wh′ on the basis of the OFF synchronized signal S13′ applied in an interval between a time when the WH diode310is turned off last time and a time when the WH diode310is turned off this time that are indicated by the WH-phase Doff detection signal S12wh′.

The W-phase higher-arm gate instruction signal generator15e″ can generate a gate instruction signal S16whof the WH element39on the basis of a result of comparison between the WH-phase ON triangular wave S15whand the WH-phase OFF triangular wave S15wh′.

The W-phase lower-arm ON triangular wave generator15fcan generate a W-phase lower-arm ON triangular wave (hereinafter called WL-phase ON triangular wave) S15wlon the basis of the ON synchronized signal S13applied in an interval between a time when the WL diode312is turned on last time and a time when the WL diode312is turned on this time that are indicated by the WL-phase Don detection signal S12wl.

The W-phase lower-arm OFF triangular wave generator15f′ can generate a W-phase lower-arm OFF triangular wave (hereinafter called WL-phase OFF triangular wave) S15wl′ on the basis of the OFF synchronized signal S13′ applied in an interval between a time when the WL diode312is turned off last time and a time when the WL diode312is turned off this time that are indicated by the WL-phase Doff detection signal S12wl′.

The W-phase lower-arm gate instruction signal generator15f″ can generate a gate instruction signal S16wlof the WL element311on the basis of a result of comparison between the WL-phase ON triangular wave S15wland the WL-phase OFF triangular wave S15wl′.

FIG. 4is a timing chart showing a signal waveform of each part of the power converter shown inFIG. 1. The example ofFIG. 4shows the waveforms of the UH-phase Don detection signal S12uh, the UL-phase Don detection signal S12ul, the UH-phase Doff detection signal S12uh′, and the UL-phase Doff detection signal S12ul′. The example ofFIG. 4does not show the waveforms of the VH-phase Don detection signal S12vh, the VL-phase Don detection signal S12vl, the WH-phase Don detection signal S12wh, the WL-phase Don detection signal S12wl, the VH-phase Doff detection signal S12vh′, the VL-phase Doff detection signal S12vl′, the WH-phase Doff detection signal S12wh′, and the WL-phase Doff detection signal S12wl′.

The example ofFIG. 4shows the waveforms of the UH-phase ON triangular wave S15uh, the UH-phase OFF triangular wave S15uh′, the VH-phase ON triangular wave S15vh, the VH-phase OFF triangular wave S15vh′, the WH-phase ON triangular wave S15wh, and the WH-phase OFF triangular wave S15wh′. The example ofFIG. 4does not show the waveforms of the UL-phase ON triangular wave S15ul, the UL-phase OFF triangular wave S15ul′, the VL-phase ON triangular wave S15vl, the VL-phase OFF triangular wave S15vl′, the WL-phase ON triangular wave S15wl, and the WL-phase OFF triangular wave S15wl′.

InFIG. 4, the stator gate driver315drives the gates of the UH element31, the UL element33, the VH element35, the VL element37, the WH element39, and the WL element311shown inFIG. 2, thereby converting a direct current defined by the positive terminal voltage Vp and the negative terminal voltage Vn to a three-phase alternating current. This three-phase alternating current is applied to the U-phase terminal, the V-phase terminal, and the W-phase terminal of the armature winding313.

The rotor gate driver317drives the gate of the field switching element324shown inFIG. 2, thereby converting a direct current defined by a positive terminal voltage VFp and a negative terminal voltage VFn to an alternating current. This alternating current is applied across the field winding314. A rotor current flowing in the field winding314is converted to a voltage at the resistor30, and the voltage across the resistor30is given to the rotor current detector320. Then, the detected value irotof the rotor current is given to the rotor gate instruction generator319.

The rotor gate instruction generator319generates the rotor gate instruction signal S21on the basis of the detected value irotof the rotor current. The generated rotor gate instruction signal S21is given to the rotor gate driver317, thereby driving the gate of the field switching element324.

The three-phase phase voltage detector318detects the positive terminal voltage Vp, the negative terminal voltage Vn, the U-phase induction voltage Vu, the V-phase induction voltage Vv, and the W-phase induction voltage Vw, and applies a result of detection as the voltage detection signal S11to the diode conducting state detector12shown inFIG. 1.

The diode conducting state detector12determines that a diode is ON in the following situation. A forward current flows into each of the UH diode32, the UL diode34, the VH diode36, the VH diode38, the WH diode310, and the WL diode312, so a forward voltage Vf is applied across the corresponding diode.

The diode conducting state detector12determines that a diode is OFF in the following situation. A forward current does not flow into each of the UH diode32, the UL diode34, the VH diode36, the VL diode38, the WH diode310, and the WL diode312, so that the forward voltage Vf is not generated as a result of an open circuit formed between the opposite ends of the diode.

When a current flows in the UH diode32, the U-phase induction voltage Vu decreases in amplitude in a negative direction by the forward voltage Vf from the negative terminal voltage Vn. When a current flows in the UL diode34, the U-phase induction voltage Vu increases in amplitude in a positive direction by the forward voltage Vf from the positive terminal voltage Vp. With attention focused on the U-phase induction voltage Vu, if the switching devices (UH and UL elements)31and33are turned on as a result of synchronous rectification, the U-phase induction voltage Vu drops by the forward voltage Vf in a period during which the UH and UL elements31and33are on. In this case, the amplitude of the U-phase induction voltage Vu is determined by the positive terminal voltage Vp and the negative terminal voltage Vn. If the UH and UL elements31and33are turned off, the amplitude of the U-phase induction voltage Vu is again determined by the positive terminal voltage Vp, Vp+Vf, and voltage Vn−Vf.

By way of example, the diode conducting state detector12can determine times when the UH diode32, the VH diode36, and the WH diode310are turned on on the basis of the following formulas (1) to (3) respectively:
ON state ofUHdiode 32:VP≦Vu≦VP+Vf(1)
ON state ofVHdiode 34:VP≦Vv≦VP+Vf(2)
ON state ofWHdiode 310:VP≦Vw≦VP+Vf(3)

The diode conducting state detector12can determine times when the UH diode32, the VH diode36, and the WH diode310are turned off on the basis of the following formulas (4) to (6) respectively:
OFF state ofUHdiode 32:Vu<Vp(4)
OFF state ofVHdiode 34:Vv<Vp(5)
OFF state ofWHdiode 310:Vw<Vp(6)

The diode conducting state detector12can determine times when the UL diode34, the VL diode38, and the WL diode312are turned on on the basis of the following formulas (7) to (9) respectively:
ON state ofULdiode 34: −Vf≦Vu≦0  (7)
ON state ofVLdiode 38: −Vf≦Vv≦0  (8)
ON state ofWLdiode 312: −Vf≦Vw≦0  (9)

The diode conducting state detector12can determine times when the UL diode34, the VL diode38, and the WL diode312are turned off on the basis of the following formulas (10) to (12) respectively:
OFF state ofULdiode 34: 0<Vu(10)
OFF state ofVLdiode 38: 0<Vv(11)
OFF state ofWLdiode 312: 0<Vw(12)

If the U-phase induction voltage Vu, the V-phase induction voltage Vv, and the W-phase induction voltage Vw are shifted in phase by 120 degrees, the UH diode32starts to conduct at a time when the U-phase induction voltage Vu satisfies the formula (1) defined with respect to the positive terminal voltage Vp. Then, the U-phase Don signal detector12adetermines that the UH diode32is on, and outputs the UH-phase Don detection signal S12uhto the Don signal synthesizer12g.

The UH diode32stops conducting at a time when the U-phase induction voltage Vu satisfies the formula (4) defined with respect to the positive terminal voltage Vp. Then, the U-phase Doff signal detector12a′ determines that the UH diode32is off, and outputs the UH-phase Doff detection signal S12uh′ to the Doff signal synthesizer12g′.

Likewise, checks to see whether the UL diode34, the VH diode36, the VL diode38, the WH diode310, and the WL diode312are on or off are made by comparing the U-phase induction voltage Vu, the V-phase induction voltage Vv and the W-phase induction voltage Vw with the positive terminal voltage Vp and the negative terminal voltage Vn.

The diode conducting state detector12outputs the UH-phase Don detection signal S12uh, the UL-phase Don detection signal S12ul, the VH-phase Don detection signal S12vh, the VL-phase Don detection signal S12vl, the WH-phase Don detection signal S12wh, and the WL-phase Don detection signal S12wlto the Don signal synthesizer12g, to the cycle checker14, and to the stator gate instruction generator PWM section15.

Next, the Don signal synthesizer12gobtains a logical sum of the UH-phase Don detection signal S12uh, the UL-phase Don detection signal S12ul, the VH-phase Don detection signal S12vh, the VL-phase Don detection signal S12vl, the WH-phase Don detection signal S12wh, and the WL-phase Don detection signal S12wl, thereby generating the diode ON synthesized signal S12. The generated diode ON synthesized signal S12is given to the ON PLL circuit121.

The diode conducting state detector12outputs the UH-phase Doff detection signal S12uh′, the UL-phase Doff detection signal S12ul′, the VH-phase Doff detection signal S12vh′, the VL-phase Doff detection signal S12vl′, the WH-phase Doff detection signal S12wh′, and the WL-phase Doff detection signal S12wl′ to the Doff signal synthesizer12g′, to the cycle checker14, and to the stator gate instruction generator PWM section15.

Next, the Doff signal synthesizer12g′ obtains a logical sum of the UH-phase Doff detection signal S12uh′, the UL-phase Doff detection signal S12ul′, the VH-phase Doff detection signal S12vh′, the VL-phase Doff detection signal S12vl′, the WH-phase Doff detection signal S12wh′, and the WL-phase Doff detection signal S12wl′, thereby generating the diode OFF synthesized signal S12′. The generated diode OFF synthesized signal S12′ is given to the OFF PLL circuit122.

The ON PLL circuit121generates the ON synchronized signal S13formed as a result of synchronization control based on the diode ON synthesized signal S12. The OFF PLL circuit122generates the OFF synchronized signal S13′ formed as a result of synchronization control based on the diode OFF synthesized signal S12′.

The ON PLL circuit121is locked and the ON synchronized signal S13is generated only when diodes of the six phases including the UH, UL, VH, VL, WH, and WL phases are sequentially turned on at substantially regular intervals. Accordingly, the synchronization control based on the diode ON synthesized signal S12makes it possible to determine that no short circuit or no open circuit is generated between the six phases including the UH, UL, VH, VL, WH, and WL phases. The synchronization control based on the diode ON synthesized signal S12also makes it possible to determine that the V and W phases are shifted +120 degrees and −120 degrees respectively from the U phase, or makes it possible to determine that the UL phase is shifted 180 degrees from the UH phase.

Likewise, the OFF PLL circuit122is locked and the OFF synchronized signal S13′ is generated only when diodes of the six phases including the UH, UL, VH, VL, WH, and WL phases are sequentially turned off at substantially regular intervals. Accordingly, the synchronization control based on the diode OFF synthesized signal S12′ makes it possible to determine that no short circuit or no open circuit is generated between the six phases including the UH, UL, VH, VL, WH, and WL phases. The synchronization control based on the diode OFF synthesized signal S12′ also makes it possible to determine that the V and W phases are shifted +120 degrees and −120 degrees respectively from the U phase, or makes it possible to determine that the UL phase is shifted 180 degrees from the UH phase.

Diodes are turned on and off at times that are controlled separately from each other. Accordingly, even when intervals between times when diodes are turned on and times when the diodes are turned off are extended or shortened depending on the amount of electricity generated, the ON PLL circuit121and the OFF PLL circuit122can stably be locked. As a result, the ON synchronized signal S13and the OFF synchronized signal S13′ can be formed with stability.

FIG. 5is a timing chart showing a way performed by the cycle checker14shown inFIG. 1to check to see whether the cycle of each phase is correct, and to check to see whether detection is performed in correct order in all the phases. In the example shown inFIG. 5, the cycle checker14provides a fixed synchronization determining interval SK extending backward and forward of the time axis of the ON synchronized signal S13. The synchronization determining interval SK is provided for each of the UH, UL, VH, VL, WH, and WL phases.

The synchronization determining intervals SK of all the phases including the UH, UL, VH, VL, WH, and WL phases are connected together. Next, a check is made to see whether the UH-phase Don detection signal S12uh, the UL-phase Don detection signal S12ul, the VH-phase Don detection signal S12vh, the VL-phase Don detection signal S12vl, the WH-phase Don detection signal S12wh, and the WL-phase Don detection signal S12wlfall within their respective synchronization determining intervals SK. As a result, it is determined whether a cycle of determining times when diodes are turned on is complied with. If it is determined that the cycle of determining times when diodes are turned on is complied with, the cycle checker14outputs a synchronization determining signal S14to the stator gate instruction generator PWM section15.

The cycle checker14can also check to see whether a cycle of determining times when diodes are turned off is complied with by following the same process as that for determining times when diodes are turned on. In order to determine a current phase, the cycle checker14can hold Curr_phase [i] (i=0, 1, 2, 3, 4, 5) and Last_phase [i] (i=0, 1, 2, 3, 4, 5).

FIG. 6is a block diagram showing the schematic configurations of phase detection resistors provided to determine a current phase. With reference toFIG. 6, each time a cycle Y1of the ON synchronized signal S13is completed, an argument i in each of Curr_phase [i] and Last_phase [i] is incremented by one to become i+1. The argument i will be 0 after 5, so that Curr_phase [i] and Last_phase [i] each form an endless loop.

In the case of three phases, the prepared phase data may contain seven types of data including “null” indicating failure of phase detection, “UH” indicating that the UH phase is detected, “UL” indicating that the UL phase is detected, “VH” indicating that the VH phase is detected, “VL” indicating that the VL phase is detected, “WH” indicating that the WH phase is detected, and “WL” indicating that the WL phase is detected.

FIG. 7shows a way of detecting current phases and last phases of the power converter shown inFIG. 1, and a way of updating phases according to circumstances. While the UH phase will be explained as an example inFIG. 7, the ways shown therein are applied to the other phases including the UL, VH, VL, WL, and WL phases.

With reference toFIG. 7, a time when a diode is turned on is determined for each cycle Y1of the ON synchronized signal S13. Information indicating that Curr_phase [i] is “UH” is written into Curr_phase [i] at a time when the diode of the UH phase is determined to be on. Each time the cycle Y1of the ON synchronized signal S13is completed, the information in Curr_phase [i] is basically transferred to Last_phase [i]. If the same phase is detected as a last phase and a current phase, the data of Last_phase [i] is updated. If different phases are detected as a last phase and a current phase, “null” is written into Last_phase [i]. Thus, it is determined that the same phase is continuously detected.

As a practical matter, specific rules for determining the condition of next Last_phase [i] can be defined by using the conditions of Last_phase [i] and Curr_phase [i]. More specifically, Last_phase [i] can be determined under conditions to determine Last_phase [i] in the ten patterns shown inFIG. 7. Next, under condition that Last_phase [i] does not show a change in phase detection over a predetermined number of cycles, the cycle checker14can output the synchronization determining signal S14indicating successful synchronization and phase detection.

In addition to the synchronization determining signal S14, the cycle checker14can also output the value of Last_phase [n] in a current cycle of the ON synchronized signal S13as estimated phase information S14′ to the stator gate instruction generator PWM section15. Likewise, the cycle checker14can output the value of Last_phase [n] in a current cycle of the OFF synchronized signal S13′ as estimated phase information S14′ to the stator gate instruction generator PWM section15.

In the exemplary simplified configuration shown inFIG. 1, with attention focused only on the UH phase, the U-phase higher-arm ON triangular wave generator15ais activated at zero degrees of the ON synchronized signal S13in a period of a last cycle in which the UH phase is detected. Then, based on a count value obtained after such an interval of time that the count value is reset at zero degrees of the ON synchronized signal S13in a period of a current cycle in which the UH phase is detected, the higher-arm ON triangular wave generator15agenerates the UH-phase ON triangular wave S15uh.

In the exemplary simplified configuration, the U-phase higher-arm OFF triangular wave generator15a′ is activated at zero degrees of the OFF synchronized signal S13′ in a period of a last cycle in which the UH phase is detected. Then, based on a count value obtained after such an interval of time that the count value is reset at zero degrees of the OFF synchronized signal S13′ in a period of a current cycle in which the UH phase is detected, the higher-arm OFF triangular wave generator15a′ generates the UH-phase OFF triangular wave S15uh′.

Following the same process as that for generating the UH-phase ON triangular wave S15uhand UH-phase OFF triangular wave S15uh′, the stator gate instruction generator PWM section15generates ON triangular waves and OFF triangular waves for the other phases including the UL, VH, VL, WL, and WL phases.

It is assumed that the UH-phase ON triangular wave S15uhand the UH-phase OFF triangular wave S15uh′ have descending slopes as shown inFIG. 4. In this case, the U-phase higher-arm gate instruction signal generator15a″ can generate the gate instruction signal S16uhsuch that the UH element31is turned on in a period during which the UH-phase ON triangular wave S15uhis higher in level than the UH-phase OFF triangular wave S15uh′.

If the UH element31is turned on in the period during which the UH-phase ON triangular wave S15uhis higher in level than the UH-phase OFF triangular wave S15uh′, a margin may be allowed for in a period during which the UH element31is on in order to avoid a problem such as reverse current flow in the UH element31.

As an example, with attention focused only on the UH-phase ON triangular wave S15uh, a level LV4to be compared with the UH-phase ON triangular wave S15uhmay be provided. The level LV4indicates a time in terms of electrical angle when the UH element31should be turned on after a point of zero degrees in each cycle of the ON synchronized signal S13.

With attention focused only on the UH-phase OFF triangular wave S15uh′, a level LV1to be compared with the UH-phase OFF triangular wave S15uh′ may be provided. The level LV1indicates a time in terms of electrical angle when the UH element31should be turned off before a point of 360 degrees in each cycle of the OFF synchronized signal S13′.

A level LV3indicating the angle of a period during which the UH element31subjected to current synchronous rectification is on may also be provided. The level LV3can determine the maximum possible degrees of an electrical angle the UH element31can be turned on in synchronous rectification, in a period in which the UH element31can be turned on after a fall time t1of the UH-phase Don detection signal S12uh. As a result, the UH element31is turned on after the UH diode32is turned on in synchronous rectification.

A period after the UH-phase ON triangular wave S15uhreaches the level LV4, which is before the UH-phase OFF triangular wave S15uh′ reaches the level LV1after the UH diode32is turned on, and which is also before the UH-phase ON triangular wave S15uhreaches the level LV3, may be defined as a period during which the UH element31is on.

With reference toFIG. 1, the U-phase higher-arm gate instruction signal generator15a″ compares the level of the UH-phase ON triangular wave S15uhwith the level LV3, thereby defining a period during which the UH element31is on.

Following the same process as that for generating the gate instruction signal S16uh, the stator gate instruction generator PWM section15generates the gate instruction signals S16ul, S16vh, S16vl, S16wh, and S16wlfor the other phases including the UL, VH, VL, WL, and WL phases, respectively.

Thus, a detection member for detecting the rotational position and the angle of a rotary motor, and a converting member for sensing an output signal of the detection member and converting the signal to data, are not required to realize synchronous rectification. Furthermore, load torque of the rotary motor is stabilized independently of the degree of accuracy in attaching these members.

The ON PLL circuit121is synchronously controlled on the basis of the diode ON synthesized signal S12. This allows collective checks to see whether diodes of the six phases including the UH, UL, VH, VL, WH, and WL phases are turned on at correct intervals, and to see whether all the phases are detected in correct order. Furthermore, the OFF PLL circuit122is synchronously controlled on the basis of the diode OFF synthesized signal S12′. This allows collective checks to see whether diodes of the six phases including the UH, UL, VH, VL, WH, and WL phases are turned off at correct intervals, and to see whether all the phases are detected in correct order.

Accordingly, determinations including the following can be made on the basis of the operating conditions of the ON PLL circuit121and the OFF PLL circuit122: a determination as to whether the ON and OFF cycles of diodes of the six phases including the UH, UL, VH, VL, WH, and WL phases are substantially the same; a determination as to whether turning-on of diodes is detected precisely in the U, V, and W phases in this order, in such a way that a phase difference is about 120 degrees in terms of electrical angle; a determination as to whether detection of turning-on of diodes is shifted 180 degrees in terms of electrical angle between higher and lower arms of the same phase; and a determination as to whether a period of time during which a switching element is on is substantially the same in the six phases. This eliminates the need to store the cycles of all the phases and the positions of detection of all the phases, and to make detailed comparisons of the degrees of the detected cycles and detected positions of detection between the phases. As a result, a burden to be placed on the process is reduced, and a storage area is also reduced.

The ON PLL circuit121and the OFF PLL circuit122may be designed in advance in consideration of their capabilities to respond to rotations including low-speed rotation at which synchronous rectification of a vehicle rotary motor is started, and highest speed rotation. This allows fine controls of variations in the gains of the ON PLL circuit121and the OFF PLL circuit122during actual operation. As a result, a data processing system can be constructed without using a high-speed microcomputer that is required to respond to simultaneous variations in load or the number of revolutions.

Second Embodiment

With reference toFIG. 5, the U-phase higher-arm ON triangular wave generator15ashown inFIG. 1may generate the UH-phase ON triangular wave S15uhin a way as follows. First, the U-phase higher-arm ON triangular wave generator15ais activated at zero degrees of the ON synchronized signal S13in a period of a last cycle in which the UH phase is detected. Next, without being reset in a detection of phases other than a self phase, the U-phase higher-arm ON triangular wave generator15areverses components of the ON synchronized signal S13in a current cycle corresponding to the six phases including the UH, WL, VH, UL, WH, and VL phases, and then sequentially adds the components. The U-phase higher-arm ON triangular wave generator15ais thereafter reset at zero degrees of the ON synchronized signal S13in a period of a current cycle in which the UH phase is detected.

The U-phase higher-arm OFF triangular wave generator15a′ shown inFIG. 1may generate the UH-phase OFF triangular wave S15uh′ in a way as follows. First, the U-phase higher-arm OFF triangular wave generator15a′ is activated at zero degrees of the OFF synchronized signal S13′ in a period of a last cycle in which the UH phase is detected. Next, without being reset in a detection of phases other than a self phase, the U-phase higher-arm OFF triangular wave generator15a′ reverses components of the OFF synchronized signal S13″ in a current cycle corresponding to the six phases including the UH, WL, VH, UL, WH, and VL phases, and then sequentially adds the components. The U-phase higher-arm OFF triangular wave generator15a′ is thereafter reset at zero degrees of the OFF synchronized signal S13′ in a period of a current cycle in which the UH phase is detected.

Following the same process as that for generating the UH-phase ON triangular wave S15uhand UH-phase OFF triangular wave S15uh′, the stator gate instruction generator PWM section15can generate ON triangular waves and OFF triangular waves for the other phases including the UL, VH, VL, WL, and WL phases.

The ON triangular waves generated in the way of the second embodiment can be synchronized with the ON PLL circuit121at times when diodes of all the phases are turned on. Accordingly, compared to the ON triangular waves generated in the way of the first embodiment, the ON triangular waves generated in the way of the second embodiment more easily respond to the change in angular velocity of a rotary motor. Further, the OFF triangular waves generated in the way of the second embodiment can be synchronized with the OFF PLL circuit122at times when diodes of all the phases are turned off. Accordingly, compared to the OFF triangular waves generated in the way of the first embodiment, the OFF triangular waves generated in the way of the second embodiment more easily respond to the change in angular velocity of the rotary motor.

With attention focused only on the U-phase, for example, it is assumed, for example, that a time when the UH element31is turned off is estimated by comparing the level LV1with a margin TMA expressed in electrical angle and defined to safely maintain the ON state of the UH element31immediately before the UH diode32is turned on. In this case, a time when the UH element31is turned off can be estimated more precisely, as the UH-phase OFF triangular wave15uh′ generated in the way of the second embodiment has greater responsiveness to speed than that generated in the way of the first embodiment.

As described above, with attention focused only on the ON side, the ON triangular waves are generated on the basis of a result of addition of the components of the ON synchronized signal S13corresponding to the six phases including the UH, WL, VH, UL, WH, and VL phases. Thus, change in speed of the rotary motor is detected in a synchronization process of the ON PLL circuit121, and the detected change can be incorporated directly into the UH-phase ON triangular wave S15uh.

The ON PLL circuit121is in synchronization with times when diodes of all the phases including a self phase and phases except the self phase are turned on. Accordingly, the UH-phase ON triangular wave S15uhmore precisely responds to change in speed of rotation of the rotary motor in real time. Furthermore, the ON synchronized signal S13after one cycle always equals the ON synchronized signal S13at a terminal point. Accordingly, a terminal point of the UH-phase ON triangular wave S15uhcan be formed by incorporating a self phase and all the phases except the self phase (if turning off of a diode is detected early, five phases including a phase immediately before the self phase).

Thus, when compared to a way of estimating a time when a diode is turned off on the basis of the UH-phase Doff detection signal S12uh′, estimation of a time when the UH element31is turned off by comparing the level LV1with the margin TMA enhances accuracy in estimating a time when the UH element31is turned off.

Third Embodiment

FIG. 8is a block diagram showing the schematic configuration of a power converter of a third embodiment of the invention. In the power converter ofFIG. 8, the gate control unit120of the power converter shown inFIG. 1is replaced by a gate control unit120′.

The gate control unit120′ includes a stator gate instruction generator PWM section15′ instead of the stator gate instruction generator PWM section15shown inFIG. 1. The gate control unit120′ further includes a stator gate ON state detector16and a stator gate instruction monitor17.

The stator gate ON state detector16determines times when each of the UH element31, the UL element33, the VH element35, the VL element37, the WH element39, and the WL element311is turned on and off on the basis of the voltage detection signal S11, and can output a switching element ON detection signal S17.

The stator gate instruction monitor17compares a time when each of the UH element31, the UL element33, the VH element35, the VL element37, the WH element39, and the WL element311is turned on with the stator gate instruction signal S16to monitor a synchronous rectification operation. Then, the stator gate instruction monitor17can output a diode ON detection period signal S18.

The stator gate instruction generator PWM section15′ can generate the stator gate instruction signal S16on the basis of the ON synchronized signal S13, the OFF synchronized signal13′, and a result of monitoring by the stator gate instruction monitor17.

The stator gate instruction monitor17checks to see whether each of the UH element31, the UL element33, the VH element35, the VL element37, the WH element39, and the WL element311was turned off in compliance with estimation by the gate instruction generator PWM section15′. The stator gate instruction monitor17also checks to see whether each of the UH diode32, the UL diode34, the VH diode36, the VH diode38, the WH diode310, and the WL diode312was turned off in compliance with estimation by the gate instruction generator PWM section15′.

Next, with attention focused only on the UH phase, the stator gate instruction monitor17makes a check in an interval between a time when the UH element31is turned off and a time when the UH diode32is turned off to see whether a period during which the UH diode32is on is detected after the UH diode32is turned off. If such a period is detected, the stator gate instruction monitor17can notify a length of time when the UH diode32is on to the stator gate instruction generation PWM section15′.

The stator gate instruction generation PWM section15′ determines how much time is left for the UH element31to be on or off in synchronous rectification. Based on the determined time, the stator gate instruction generation PWM section15′ can control a period during which the UH element31is on to be shorter or longer than a last cycle.

Thus, efficiency in a synchronous rectification operation is raised to its highest possible level in consideration of real-time operating condition of a rotary motor.

FIG. 9is a timing chart showing a signal waveform of each part of the power converter shown inFIG. 8. With reference toFIG. 9, with attention focused only on the U-phase induction voltage Vu, a threshold TH1to detect voltage change of the UH diode32by the forward voltage Vf with respect to the positive terminal voltage Vp is defined for the U-phase induction voltage Vu. The threshold TH1may be about half the voltage Vf.

At this time, ON state of the UH element31is detected and the threshold TH1is defined not on the basis of a ground potential but on the basis of a difference from the positive terminal voltage Vp. Further, a differential comparison amplifier is used for detection, thereby enhancing a detection accuracy.

Likewise, a threshold TH2to detect voltage change of the UL diode33by the forward voltage Vf with respect to the negative terminal voltage Vn is defined for the U-phase induction voltage Vu. The threshold TH2may be about half the voltage Vf.

At this time, ON state of the UL element32is detected and the threshold TH2is defined not on the basis of a ground potential but on the basis of a difference from the negative terminal voltage Vn. Further, a differential comparison amplifier is used for detection, thereby enhancing a detection accuracy.

The stator gate ON state detector16outputs a UH element ON detection signal S17uhas a result showing that gate ON state of the UH element31is detected to the stator gate instruction monitor17.

Likewise, the stator gate ON state detector16outputs a UL element ON detection signal S17ulas a result showing that gate ON state of the UL element33is detected, a VH element ON detection signal S17vhas a result showing that gate ON state of the VH element35is detected, and a VL element ON detection signal S17vlas a result showing that gate ON state of the VL element37is detected. The stator gate ON state detector16also outputs a WH element ON detection signal S17whas a result showing that gate ON state of the WH element39is detected, and a WL element ON detection signal S17wlas a result showing that gate ON state of the WL element311is detected.

Assuming that a rise time t11of the gate instruction signal S16uhgiven from the stator gate instruction generator PWM section15′ is a starting point, the stator gate instruction monitor17detects a low period by using a fall time t12of the UH element ON detection signal S17uhin an event after the time t11. Then, the stator gate instruction monitor17generates a UH diode ON detection period signal S18uhindicating a period after the UH element31is turned off, and outputs the UH diode ON detection period signal S18to the stator gate instruction generator PWM section15′.

Likewise, the stator gate instruction monitor17outputs a UL diode ON detection period signal S18ulindicating a period after the UL element33is turned off, a VH diode ON detection period signal S18vhindicating a period after the VH element35is turned off, and a VL diode ON detection period signal S18vlindicating a period after the VL element37is turned off. The stator gate instruction monitor17also outputs a WH diode ON detection period signal S18whindicating a period after the WH element39is turned off, and a WL diode ON detection period signal S18wlindicating a period after the WL element311is turned off.

The stator gate instruction generator PWM section15′ can measure a time T1of a detection period of the UH diode ON detection period signal S18by using a first counter for making counts at fixed time intervals H1such as 1 usec.

The stator gate instruction generator PWM section15′ compares a current level of the UH-phase OFF triangular wave15uh′ with the level LV1. Then, by using a second counter for making counts at the fixed time intervals H1, the stator gate instruction generator PWM section15′ can measure a time T2of a period during which the level LV1is higher than the level of the UH-phase OFF triangular wave15uh′, and record the measured time T2.

The stator gate instruction generator PWM section15′ compares the times T1and T2to see whether the UH element31was turned off too early or too late. If the UH element31was turned off too early, the stator gate instruction generator PWM section15′ may raise the level LV2. If the UH element31is turned off too late, the stator gate instruction generator PWM section15′ can lower the level LV2.

Thus, the stator gate instruction generator PWM section15′ can generate the stator gate instruction signal S16while the UH element31is always turned off correctly in compliance with variations in rotation of the rotary motor.

Fourth Embodiment

With reference toFIG. 8, the cycle checker14compares the diode ON synthesized signal S12with the ON synchronized signal S13. The cycle checker14also compares the diode OFF synthesized signal S12′ with the OFF synchronized signal S13′.

By way of example, the cycle checker14provides a fixed synchronization determining interval SK extending backward and forward of the time axis of the ON synchronized signal S13. The synchronization determining interval SK is provided for each of the UH, UL, VH, VL, WH, and WL phases.

The synchronization determining intervals SK of all the phases including the UH, UL, VH, VL, WH, and WL phases are connected together. Next, a check is made to see whether the UH-phase Don detection signal S12uh, the UL-phase Don detection signal S12ul, the VH-phase Don detection signal S12vh, the VL-phase Don detection signal S12vl, the WH-phase Don detection signal S12wh, and the WL-phase Don detection signal S12wlfall within their respective synchronization determining intervals SK. As a result, it is determined whether a cycle of determining times when diodes are turned on is complied with. It is also determined whether an order of determining times is complied with. If it is determined that the cycle of determining times when diodes are turned on is complied with, and that the order of determining times is complied with, the cycle checker14outputs the synchronization determining signal S14to the stator gate instruction generator PWM section15′.

In the case of rotation in a forward rotation, for example, phases are detected in the following order: UH, WL, VH, UL, WH, VL, and UH phases. Accordingly, by making a check to see whether times when diodes are turned off in this order, compliance with the order of determining times when diodes are turned on is checked. If the order of phase detection does not change, or there is no loss in the order over a predetermined number of cycles (such as one or eight cycles), the cycle checker14determines that synchronization determination ends in success, and outputs the synchronization determining signal S14.

By following the same process as that for the process relating to determination of times when diodes are turned on, the cycle checker14can check to see whether a cycle of determining times when diodes are turned off is complied with, and whether an order of determining times is complied with.

Thus, the cycle checker14can check to see whether times when diodes of all the phases are turned on and off are determined at fixed intervals. The cycle checker14can also check to see whether times when diodes are turned on and off are determined in a given order of phases. This allows a more reliable check to see that a phase difference is at a fixed level (120 degrees) between the U, V, and W phases, and that a phase difference between the higher side and the lower side is at a fixed level (180 degrees).

Fifth Embodiment

With reference toFIG. 4, with attention focused only on the UH phase, a margin PMA is set at the level LV4. The margin PMA extends from a point of zero degrees in each cycle of the ON synchronized signal S13to a time when the UH element31is turned on in terms of electrical angle of a rotary motor.

The stator gate instruction generator PWM section15′ compares the level of the UH-phase ON triangular wave S15uhwith the level LV4. Then, the stator gate instruction generator PWM section15′ can turn the UH element31on at the fall time t1of the UH-phase Don detection signal S12uh, or a time t2when the level of the UH-phase ON triangular wave S15uhreaches the level LV4that is later than the other.

The margin TMA is set at the level LV1. The margin TMA extends from a point of 360 degrees in each cycle of the OFF synchronized signal S13′ to a time when the UH element31is turned off in terms of electrical angle of the rotary motor. A period during which the UH element is on is set at the level LV3.

The stator gate instruction generator PWM section15′ compares the level of the UH-phase OFF triangular wave S15uh′ with the level LV1, and compares the level of the UH-phase ON triangular wave S15uhwith the level LV3. Then, the stator gate instruction generator PWM section15′ can turn the UH element31off at a time t3when the level of the UH-phase OFF triangular wave S15uh′ reaches the level LV1, or at a time t4when the UH-phase ON triangular wave S15uhreaches the level LV3that is earlier than the other.

Sixth Embodiment

With reference toFIG. 9, with attention focused only on the UH phase, it is assumed that the level LV3is set such that a period during which the UH element31is on is longer than a period during which the UH diode32is on. In this case, the stator gate instruction generator PWM section15′ shown inFIG. 8measures a time UH_bkm_time of a UH diode ON detection period signal S18uhto see whether the UH element31is turned off at a too early time or at a too late time with respect to the time t3when the level of the UH-phase OFF triangular wave S15uh′ reaches the level LV1.

Then, the stator gate instruction generator PWM section15′ compares the level LV2with the UH-phase ON triangular wave S15uhwhile raising or lowering the level LV2within a predetermined degree. This allows a period during which the UH element31is on to be maximized with respect to a period during which the UH diode32is on.

Seventh Embodiment

With reference toFIG. 9, with attention focused only on the UH phase, the stator gate instruction generator PWM section15′ shown inFIG. 8measures lengths of time of one ON cycle and one OFF cycle of the UH diode32by using a counter. Next, the stator gate instruction generator PWM section15′ compares measured lengths of time at each measurement to see the number of counts a unit electrical angle corresponds to in terms of time. Then, the stator gate instruction generator PWM section15′ converts times when the UH element31is turned on and off to electrical angles, and outputs a level signal.

The stator gate instruction generator PWM section15′ thereafter compares the level signal with the UH-phase ON triangular wave S15uhand the UH-phase OFF triangular wave S15uh′ while taking the levels LV1and LV4defined on the basis of angle into consideration. Thus, while restrictions on setting a period during which the UH element31is on based on electrical angle and those based on time are simultaneously taken into consideration, the stator gate instruction generator PWM section15′ can define a period during which the UH element31is on under stricter restrictions.

As an example, when a level signal is generated by converting a count value of time to an electrical angle, “phase_last_off_level” is obtained from the following formula:
360/(phase_last_period)×phase_bkm_time

In this formula, “phase_last_period” represents a time count value from a time when a diode is turned on immediately before to a time when the diode is turned on this time, and “phase_bkm_time” represents a time count value from a time of switching off immediately before to a time when a diode is turned off.

If “phase_last_off_level” is the same as or greater than “off_level_target angle,” “phase_off_level_setting” may be decreased. If “phase_last_off_level” is smaller than “off_level_target angle,” “phase_off_level_setting” may be increased. Here, “off_level_target angle” may be common to all the phases.

As an example, With reference toFIG. 9, with attention focused on the UH phase, a time “UH_bkm_time” of the UH diode ON detection period signal S18uhis measured to obtain “UH_last_off_level.” Then, based on a result of comparison between “UH_last_off_level” and “off_level_target angle,” “UH_level_setting” is increased or decreased, thereby defining a UH-phase OFF level LV5(time t13). This process may be performed within a calculation time HE. Then, based on a newly defined “UH_level_setting,” a time when the UH element31shown inFIG. 2is turned off is controlled.

As described above, a period during which the UH element31is on can be defined in combination with restrictions based on electrical angle and those based on time, and the UH element31can be controlled to be turned on and off at a time of a greater electrical angle. This allows a higher degree of safety in synchronous rectification in situations including low-speed rotation in which a time of a unit electrical angle is long and high-speed rotation in which a time of a unit electrical angle is quite short.

Eighth Embodiment

FIG. 10is a block diagram showing the schematic configuration of a vehicle system of an eighth embodiment to which the power converter of the invention is applied. With reference toFIG. 10, a power generator motor43functioning as a vehicle rotary motor generates electricity after driven by an internal combustion engine41through a torque transmitter42such as a belt, thereby generating AC energy.

AC energy generated by the power generator motor43is converted to DC energy while the internal combustion engine41is in operation. The converted DC energy is stored in the storage battery44. The power converter shown inFIG. 1, or the power converter shown inFIG. 8may be used as the power generator motor43ofFIG. 8.

The power converter described in the foregoing embodiments performs power conversion for three phases including the U, V, and W phases. However, the invention is not limited to the power converter for performing power conversion for three phases including the U, V, and W phases. As long as phases are evenly spaced in terms of electrical angle, the invention may also be applied to a power converter for performing power conversion for N (N is an integer no less than two) phases.

The invention realizes synchronous rectification without requiring attachment of a sensor for determining a rotational position to the shaft of a rotary motor. The invention also reduces a burden to be placed on a check to see whether the cycle of an induction voltage of each phase is correct, and whether phases are detected in correct order.