Engine control and methods for controlling an engine

Abstract

Motor control (100), comprising: an H-bridge circuit (20, 20X, 20Y) comprising switching elements (2, 4, 6, 8), freewheeling diodes and half-bridges connected to motor coils provided in the motor (120); a current detector (116) that detects a current flowing in the motor coil (124); a zero-crossing detector that detects a zero crossing of a back EMF of each of the motor coils; and a controller that operates the H-bridge circuit (20, 20X, 20Y) such that it is operated in one of different operating modes, the operating modes include a charging mode, a high-dissipation mode, a low-dissipation mode and a power-off mode and wherein the operating mode is set on the basis of the motor current detected by the current detector (116) by activating the switching elements (2, 4, 6, 8) of the H-bridge circuit (20, 20X, 20Y), where the H-bridge circuit (20, 20X, 20Y) increases the motor current flowing in the respective motor coils in the charging mode, in the high-dissipation mode the H-bridge circuit (20, 20X, 20Y) operates with high energy dissipation and a freewheeling pulse is induced in each of the motor coils, in the low-dissipation mode the H-bridge circuit (20, 20X, 20Y) operates with a low energy dissipation, which is lower than in the high-dissipation mode, wherein the H-bridge circuit (20, 20X, 20Y) is operated in such a way that the zero-crossing detector is enabled to detect the zero crossing of the back EMF of each of the motor coils after the freewheeling pulse of each of the motor coils has decreased, the control system is further operated in such a way that it carries out a process which includes: Controlling the H-bridge circuit (20, 20X, 20Y) to switch to charging mode; Controlling the H-bridge circuit (20, 20X, 20Y) to switch to high-dissipation mode when the zero-crossing detector detects that the back EMF of the motor coil (124) connected to a phase of the H-bridge circuit (20, 20X, 20Y) is about to cross zero; Controlling the H-bridge circuit (20, 20X, 20Y) to switch to low-dissipation mode after a predetermined time has elapsed; and Control of the H-bridge circuit (20, 20X, 20Y) to switch to the de-energized mode when the motor current detector detects that the motor current flowing in the motor coil (124) connected to the H-bridge circuit (20, 20X, 20Y) is flowing in a direction opposite to that of the charging mode.

Description

Background of the invention 1. Field of the invention

[0001] The present invention relates to a motor control system and a method for controlling a stepper motor. 2. Description of the state of the art

[0002] A method for controlling an inductive load is disclosed in JP H10-80 194 A which combines a regenerative electric current and a flowing electric current such that a switching current flowing in an inductive load is suitable.

[0003] Paragraph

[0023] of JP H10-80 194 A describes that “an H-bridge circuit is configured to allow a current to flow in opposite directions in an inductive load, i.e.in a forward and a reverse direction, with four semiconductor switching elements and freewheeling diodes, each connected antiparallel to the semiconductor switching elements, such that when a current supply operation is carried out to supply a current from a current source to the inductive load, two of the semiconductor switching elements assume a conduction state to cause current to flow in a desired direction into the inductive load, and thereby the current flowing into the inductive load is increased by such a current supply operation, which has the result that when the current is greater than or equal to a predetermined reference current value, the energy accumulated in the inductive load is released to control the current flowing in the inductive load.

[0004] Paragraph

[0024] describes that “control can then be carried out by two types of processes: One is carried out in such a way that one of the semiconductor switching elements assumes the conducting state, so that the semiconductor switching element which is in the conducting state forms a closed current path with a freewheeling diode, wherein the energy stored in the inductive load causes a current flow in the closed current path, and the other is carried out in such a way that all four semiconductor switching elements are interrupted, so that current flows through the two freewheeling diodes due to the energy stored in the inductive load and thereby charge current.”

[0005] The first process, which causes current to flow in the closed current path, is called communication control.

[0006] Furthermore, paragraph

[0026] of JP H10-80194A describes that “a predetermined frequency of a control cycle is set and a current supply operation is started by initiating the control cycle, such that when a current flowing in the inductive load is greater than or equal to a predetermined value during a current supply operation, the current supply operation is terminated and the energy accumulated in the inductive load is released, and assuming that a predetermined period after the initiation of the control cycle is defined as a current regeneration period, and a period from the end of the current regeneration period to the end of the control cycle is defined as a current period, a current regeneration process is carried out within the current regeneration period after the current supply operation is terminated, and the communication control is carried out within the current period.”

[0007] A motor is driven by rotating a multitude of drive coils in opposite directions (bipolar), thus energizing a different phase than before. If switching elements located on opposite sides of the coils—namely, on a motor supply voltage side (upper bridge branch) and a ground side (lower bridge branch)—are simultaneously switched off while the motor is rotating, a high voltage of a freewheeling pulse (kickback) is induced by the energy accumulated in the coils.

[0008] The coil current is maximized at the time of the phase change. When the freewheeling pulse is induced, the coil current discharges to ground due to a parasitic transistor effect caused by the complementary MOS (CMOS) manufacturing process of an application-specific integrated circuit (ASIC), resulting in power dissipation. This heat generation by the ASIC limits its operation at high temperatures.

[0009] During the period in which the freewheeling pulse is induced, the switching elements on the upper side of the bridge are temporarily switched on, instead of all switching elements being switched off. This causes the current discharged to ground to flow through the switching elements on the upper side of the bridge and thus back to a power supply source of the motor. In this way, it is possible to reduce power loss.

[0010] However, since the period during which the freewheel pulse is induced varies depending on the motor's control voltage, drive load, and rotational speed, it is difficult to precisely control the flow time in relation to motor operation. Therefore, a situation can arise where the timing for communication control is not optimal, resulting in undesirable power loss.

[0011] For example, if the communication control time is shorter than the period during which the freewheeling pulse is induced, current flowing in the switching elements will flow back through a freewheeling diode connected in parallel, causing power loss. Conversely, if the communication control time is shorter than the period during which the freewheeling pulse is induced, an inductive load will be short-circuited to act as a brake against the motor's rotation, making it even more difficult to control the motor's speed and impossible to measure back EMF to detect step loss after the motor speed has been set.

[0012] Furthermore, it is possible to reduce the heat generation effect by attaching a heat sink to an ASIC and increasing the size of the substrate and the amount of copper. However, this method is problematic because it increases the size of the substrate or package, as well as the manufacturing costs.

[0013] An externally mounted diode is added to each motor output, allowing the coil current to flow back to the motor power source without being affected by the parasitic transistor effect, thus reducing power loss. However, this method is also problematic because it increases the substrate size and manufacturing costs due to the larger mounting point and surface area.

[0014] US Patent 7,545,369 B1 discloses methods and devices for improving the efficiency of cold cathode fluorescent lamp (CCFL) controls by using a full-bridge resonant implementation. The secondary winding of a transformer drives the CCFL, while the primary winding of the transformer is driven by a full bridge via a capacitor. The bridge connects the capacitor and the primary winding alternately and repeatedly between the power supply terminals, through one of the power supply terminals, between the power supply terminals with alternating polarity, and again through one of the power supply terminals. Instead of switching from one power supply terminal to another when the primary current is near zero, a delay is intentionally introduced before the switchover.

[0015] Further state of the art is known from US 2006 / 0 152 947 A1 and JP 2004 - 274 880 A. Summary of the invention

[0016] One of the objects of the present invention is to provide a motor control and a method for controlling a stepper motor which are designed to reduce power loss by returning a current discharged to a ground terminal to a current source.

[0017] The invention is defined in the claims.

[0018] According to an illustrative embodiment of the present invention, a motor control system is provided comprising: an H-bridge circuit with switching elements, freewheeling diodes, and half-bridges connected to motor coils arranged in the motor; a current detector that detects a motor current flowing in the motor coil; a zero-crossing detector that detects a zero crossing of the back EMF of each of the motor coils; and a control unit that operates the H-bridge circuit in one of the following modes: a charging mode, a high-dissipation mode, a low-dissipation mode, and a currentless mode, by activating the switching elements of the H-bridge based on the motor current detected by the current detector. In the charging mode, the H-bridge circuit increases the motor current flowing in the respective motor coils.In high-dissipation mode, the H-bridge circuit operates with high energy dissipation, inducing a freewheeling pulse in each of the motor coils. In low-dissipation mode, the H-bridge circuit operates with low energy dissipation, lower than in high-dissipation mode. The H-bridge circuit is operated in such a way that the zero-crossing detector can detect the zero crossing of the back EMF of each of the motor coils after the freewheeling pulse of each motor coil has decayed.The controller is further operated to carry out a process comprising: controlling the H-bridge circuit to switch to charging mode; controlling the H-bridge circuit to switch to high-dissipation mode when the zero-crossing detector detects that the back EMF of the motor coil connected to a phase of the H-bridge circuit just upstream of the H-bridge circuit passes through zero; controlling the H-bridge circuit to switch to low-dissipation mode after a predetermined time has elapsed; and controlling the H-bridge circuit to switch to no-current mode when the voltage detector detects that the motor current flowing in the motor coil connected to the H-bridge circuit is flowing in a direction opposite to that in charging mode.

[0019] According to a further illustrative embodiment of the present invention, a method for controlling a motor with a motor controller is provided, comprising: an H-bridge circuit having switching elements, freewheeling diodes and half-bridges, wherein the half-bridges are connected to motor coils provided in the motor; a current detector that detects a motor current flowing in the motor coil; a zero-crossing detector that detects a zero crossing of a back EMF of each of the motor coils; and a controller that is operated to control the H-bridge circuit to be operated in one of operating modes comprising a charging mode, a high-dissipation mode, a low-dissipation mode and a no-current mode, by activating the switching elements of the H-bridge circuit based on the motor current detected by the current detector.In charging mode, the H-bridge circuit increases the motor current flowing in the respective motor coils. In high-dissipation mode, the H-bridge circuit operates with high energy dissipation, inducing a freewheeling pulse in each motor coil. In low-dissipation mode, the H-bridge circuit operates with low energy dissipation, which is lower than in high-dissipation mode. The H-bridge circuit is operated such that the zero-crossing detector can detect the zero crossing of the back EMF of each motor coil after the freewheeling pulse of each motor coil has decreased.The method comprises: controlling the H-bridge circuit to switch to charging mode; controlling the H-bridge circuit to switch to high-dissipation mode when the zero-crossing detector detects that the back EMF of the motor coils connected to a phase of the H-bridge circuit just upstream of the H-bridge circuit is experiencing a zero crossing; controlling the H-bridge circuit to switch to low-dissipation mode after a predetermined time has elapsed; and controlling the H-bridge circuit to switch to no-current mode when the motor current detector detects that the motor current flowing in the motor coil connected to the H-bridge circuit is flowing in a direction opposite to that in charging mode. Short description of the drawings

[0020] The accompanying drawings show: Fig. 1. A complete block diagram illustrating an engine control system according to one embodiment and a comparative example; Fig. 2. A detailed block diagram illustrating an engine control system according to the embodiment and the comparative example; the Fig. 3A to 3D explanatory views illustrating the operating modes of an H-bridge circuit according to the embodiment; Fig. 4 a waveform representation illustrating current sequences of an X-phase and a Y-phase of the H-bridge circuit; Fig. 5 a waveform representation illustrating a voltage and current of each part of the X-phase of the H-bridge circuit; Fig. 6 a flowchart illustrating the processing of a first quadrant of the X-phase of the device for controlling the motor control according to the first embodiment; Fig. 7 a flowchart illustrating the processing of a second quadrant of the X-phase of the device for controlling the motor's actuation according to the embodiment; the Fig. 8A to 8C explanatory views illustrating the operating modes of an H-bridge circuit according to a comparative example; Fig. 9 a waveform representation illustrating current sequences of an X-phase and a Y-phase of the H-bridge circuit according to the comparison example; Fig. 10 a flowchart illustrating the processing of a first quadrant of the X-phase of a motor control according to the comparative example; and Fig. 11 a flowchart illustrating the processing of a second quadrant of the X-phase of the device for controlling the motor control according to the comparative example. Detailed description

[0021] The following is a detailed description of embodiments of the present invention with reference to the accompanying drawings.

[0022] Fig. Figure 1 shows an entire block diagram of an engine control system according to an embodiment of the present invention.

[0023] In Fig. Figure 1 is a motor 120, a bipolar two-phase stepper motor, comprising a rotor 126 with a permanent magnet mounted for free rotation, and stators mounted at four positions around the circumference of the rotor 126. These stators include stators 122XP and 122XN, each with an X-phase, and stators 122YP and 122YN, each with a Y-phase. Coils are wound around the corresponding stators. The coils wound around stators 122YP and 122YN are connected in series, so the two coils together are referred to as "coil 124Y". Similarly, the coils wound around stators 122XP and 122XN are also connected in series, so the two coils together are referred to as "coil 124X".

[0024] A host device 130 outputs a speed command signal to instruct the motor 120 to run at a specific speed. A motor controller 100 controls the drive of the motor 120 in response to the speed command signal. H-bridge circuits 20X and 20Y are integrated into the motor controller 100 to apply a voltage VMX of the X-phase and a voltage VMY of the Y-phase to the coils 124X and 124Y, respectively.

[0025] One end of coil 124X of the X-phase is a connection point Mouto, while the other end is a connection point Mout1. The voltage VMX of the X-phase is the difference between the voltage at connection Mout1 and the voltage at connection Mout1. In a coil current IMX of the X-phase, a direction from connection point Mouto to connection point Mout1 is set as a positive direction.

[0026] Furthermore, one end of coil 124Y of the Y-phase is a connection point Mout2, while the other end is a connection point Mout3. The voltage VMY of the Y-phase is the difference between the voltage at connection point Mout3 and the voltage at connection point Mout2. In a coil current IMY of the Y-phase, the direction from connection point Mout2 to connection point Mout3 is set as a positive direction.

[0027] The motor control unit 100 is described in detail using the following: Fig. 2 described.

[0028] Fig. Figure 2 is a detailed block diagram illustrating the motor control according to the embodiment.

[0029] Fig. Figure 1 shows two systems of coils 124X and 124Y and two systems of H-bridge circuits 20X and 20Y, while Fig. Figure 2 shows a system of coil 124 and a system of H-bridge circuit 20.

[0030] A central processing unit (CPU) 101, built into the motor controller 100, controls each part via a bus 106, based on a control program stored in a read-only memory (ROM) 103. Random access memory (RAM) 102 serves as the working memory of the CPU 101. A clock 104 measures the time elapsed since a reset time, controlled by the CPU 101. An I / O port 105 transmits signals between the host device 130, located at the top position in Fig. 1 is arranged, and other external devices on or off. A bridge controller 107 controls each part of the bridge control circuit 110 based on an instruction from the CPU 101.

[0031] The bridge control circuit 110 is configured as an integral integrated circuit. A PWM signal generator 113, provided in the bridge control circuit, is controlled by the bridge controller 107, generates a PWM signal, and then supplies this signal to the H-bridge circuit 20. The H-bridge circuit 20 contains switching elements 2, 4, 6, and 8, which consist of FETs (field-effect transistors). The PWM signal is an on / off signal that is applied to the switching elements 2, 4, 6, and 8 as a gate voltage. In the diagram, the lower terminal of each of the switching elements 2, 4, 6, and 8 becomes a source terminal, while their upper terminal becomes a drain terminal.

[0032] Switching elements 2 and 4 are connected in series, and a DC power source 140 and a ground 142 are connected to the series circuit, applying a predetermined supply voltage MVdd. Similarly, switching elements 6 and 8 are also connected in series, applying the supply voltage MVdd to the series circuit. Diodes 12, 14, 16, and 18 are reverse current diodes and are connected in parallel with switching elements 2, 4, 6, and 8. Switching elements 15 and 17 are for current sensing and, together with switching elements 4 and 8 respectively, form part of a current mirror circuit. In this way, a current proportional to the current flowing in switching elements 4 and 8 flows in either switching element 15 or 17.

[0033] A voltage VMouto from a connection point Mouto between switching elements 2 and 4 is applied to one end of the coil 124X of motor 120. Furthermore, a voltage VMout1 from a connection point Mout1 between switching elements 6 and 8 is applied to the other end of the coil 124. In this way, a motor voltage VM (= voltage VMouto - VMout1), which is equal to the difference between the voltage VMouto and the voltage VMout1, is applied to the coil 124. The motor voltage VM is actually the voltage VMX of the X-phase and the voltage VMY the voltage of the Y-phase, which are in Fig. Figure 1 shows the following. Furthermore, a voltage VMout2 is applied to the coil 124Y of the Y-phase and a voltage VMout3 is applied to the other end of the coil 124Y of the Y-phase.

[0034] A current detector 116 measures the current flowing in the switching element 15, 17 in one direction and thus outputs a current reading Icoil of the current flowing in the coil 124. A digital-to-analog converter 115 receives a digital value of a current reference value Iref from the bridge controller 107 and converts it into an analog value. A comparator 114 compares the current reading Icoil of the analog value with the current reference value Iref and then outputs a "1" signal if the current reading is greater than or equal to the current reference value, and outputs a "0" signal in other cases.

[0035] The voltages VMouto and VMout1 are also supplied to a back EMF detector 118. The back EMF detector 118 is a zero-crossing detector. When the motor voltage VM is the back EMF, namely during a period when no voltage is applied from the H-bridge circuit 20, the voltage polarity reverses (zero crossing), and a flag ZC is output.

[0036] The Fig. Figures 8A to 8C are explanatory views that illustrate an operating mode of the H-bridge circuit 20 according to the comparison example.

[0037] Fig. 8A is a view showing the operation of the H-bridge circuit 20 in a charging mode.

[0038] When motor current is applied to coil 124, two diagonally opposite switching elements are turned on. In the example shown, switching elements 4 and 6 are on, while switching elements 2 and 8 are off. In this state, the motor current flows through switching element 6, coil 124, and switching element 4 in a direction indicated by a thick line. The period during which the H-bridge circuit 20 operates in charging mode is referred to as a "current-energizing period".

[0039] Even when the gate voltage of one of the switching elements is switched off, a related switching element remains temporarily in the on state due to its parasitic capacitance. Therefore, when diagonally opposite switching elements 4 and 6 are switched from the on state to the off state, and simultaneously the other diagonally opposite switching elements 2 and 8 are switched from the off state to the on state, the series-connected switching elements 2 and 4 are temporarily on, causing a current breakdown. This creates a short circuit between the DC power source 140 and ground 142, potentially destroying switching elements 2 and 4. The same applies to switching elements 6 and 8. To avoid this problem, the H-bridge circuit 20 is switched from "charging mode" to a "high-dissipation mode" of Fig. 8B offset.

[0040] This means that if switching elements 4 and 6 are off, while switching elements 2 and 8 are off, the operation will be in charging mode. Fig. 8A into high-dissipation mode of Fig. 8B transitions. A period in which the H-bridge circuit 20 is operated in high-dissipation mode is referred to as the "high-dissipation period".

[0041] Fig. Figure 8B is a view showing the operation of the H-bridge circuit 20 in high-dissipation mode.

[0042] In high-dissipation mode, the H-bridge circuit 20 switches off all switching elements 2, 4, 6, and 8. At this time, current flows through diode 18, coil 124, and diode 12 in a direction indicated by a thick line due to energy stored in coil 124. That is, the energy accumulated in coil 124 causes current to flow in a closed circuit formed by the high-side diode 12, which is oriented in the direction of the motor current (indicated by a thick line), and the low-side diode 18, which is oriented in the opposite direction to the motor current (indicated by a thick line). This high-dissipation mode results in power dissipation in response to a forward voltage drop Vf across diodes 12 and 18.When the H-bridge circuit 20 is formed by a CMOS process, the current leaks to ground 142 due to the parasitic transistor effect in high-dissipation mode, generating heat and consequently increasing energy dissipation.

[0043] If the coil 124 receives enough energy from the high-dissipation mode of Fig. When 8B is released, no current flows.

[0044] Fig. 8C is a view illustrating the operation of the H-bridge circuit 20 in a currentless mode.

[0045] In the de-energized mode, the H-bridge circuit 20 switches off all switching elements 2, 4, 6, and 8. At this time, the energy accumulated in coil 124 is released. In this de-energized mode, the back EMF appears in coil 124. The bridge control circuit 110 switches to the next quadrant, in which the zero crossing of the back EMF of motor 120 during the de-energized period is detected. Furthermore, the H-bridge circuit 20 switches back to the charging mode. Fig. 8A um.

[0046] Fig. Figure 9 is a waveform representation illustrating current sequences of the X-phase and the Y-phase of the H-bridge circuit 20.

[0047] The waveform display of Fig. Figure 9 shows the voltage Mouto of the X-phase as a thick line and the setting of switching element 6 as a thick dashed line. This shows the voltage VMout1 of the X-phase using the thick line and the setting of switching element 2 using the thick dashed line. This thick dashed line has a high value (H level) when each switching element is on and a low value (L level) when each switching element is off. Furthermore, the coil current IMX and the operating mode of the X-phase are also shown in Figure 9. Fig. 9 shown.

[0048] Furthermore, the waveform display of Fig. Figure 9 shows the voltage VMout2 of the Y-phase in a solid line and the setting of the upper bridge-side switching element of a branch at connection point Mout2 in a dashed line. Figure 9 shows the voltage VMout3 of the Y-phase in a solid line and the setting of the upper bridge-side switching element of a branch at connection point Mout3 in a dashed line. Furthermore, the coil current IMY and the operating mode of the Y-phase are also shown. Fig. 9 shown.

[0049] The motor controller 100 of the comparison example drives the motor 120 in phase excitation in response to the motor control voltage and the load. The motor 120 rotates by creating an electrical angle with four phases (quadrants). When the X-phase is the current-energizing period (see Fig. 8A) in any quadrant, the Y-phase takes over the free period (see Fig. 8C) after the high-dissipation period (see Fig. 8B).

[0050] When the motor control voltage is high or the load is low, the motor speed 120 increases, and the maximum current of the coil 124 decreases. When the motor drive load is low, the freewheeling pulse duration is shortened. Back EMF is generated during the current-free period of each phase. This back EMF is high when the motor speed is high and becomes 0 [V] at standstill, so it can be used to detect step loss.

[0051] In Fig. Quadrant 9 represents the first quadrant, a period from time t111 to time t121. During this first quadrant, the H-bridge circuit 20X of the X-phase operates in charging mode. At this time, the upper-bridge switching element 6 of a branch at connection point Mouto of the H-bridge circuit 20X and connection point Mout1 conduct current to the DC power source 140 to apply the supply voltage MVdd, and connection point Mout1 conducts current to ground 142, thus becoming 0 [V]. The coil current IMX of the X-phase flows in one direction from connection point Mouto to connection point Mout1, and the absolute value of the current gradually increases.

[0052] In the first quadrant, all switching elements of the H-bridge circuit 20Y of the Y-phase are switched off, and the H-bridge circuit is operated in high-dissipation mode from time t111 until time t112, and is operated in no-current mode after time t112. Fig. 9 is the high dissipation mode, simply referred to as "K".

[0053] Immediately after time t111, the voltage VMout2 at connection point Mout2 of the Y-phase becomes greater than or equal to (+MVdd + Vf) [V] due to the flyback pulse and is clamped by the diode. Furthermore, the voltage VMout3 at connection point Mout3 becomes less than or equal to (-Vf) [V] and is clamped by the diode. The voltage values ​​of VMout2 and VMout3 at connection point Mout3 are maintained for a predetermined period. At time t121, the voltage VMout2 is suddenly reduced to 0 [V]. Later than VMout2, the voltage VMout3 is slightly increased and then gently reduced back to 0 [V] at time t121.The coil current IMY of the Y-phase flows in one direction from the connection point Mout3 to the connection point Mout2 immediately after time t111, but the absolute value of the current is gradually reduced to 0 [mA] shortly before time t112 and is then held at 0 [mA] until time t121 is reached.

[0054] The second quadrant is a period from time t121 to time t131. In this second quadrant, all switching elements 2, 4, 6 and 8 of the H-bridge circuit 20X of the X-phase are in the off state and the H-bridge circuit is operated in high-dissipation mode from time t121 to time t122 ​​and is operated in de-energized mode after time t122.

[0055] Immediately after time t121, the voltage VMout1 at connection point Mout1 of the X-phase becomes greater than or equal to (+MVdd + Vf) [V] due to the feedback pulse and is clamped by diode 12. Furthermore, the voltage VMouto at connection point Mouto becomes less than or equal to (-Vf) [V] and is clamped by diode 18. The voltage values ​​of VMout1 at connection point Mout1 and VMouto at connection point Mouto are maintained for a predetermined period. At time t122, the voltage VMout1 is suddenly reduced to 0 [V]. Later than the voltage VMout1, the voltage VMouto is slightly increased and then gently reduced back to 0 [V] at time t131.The coil current IMX of the X-phase flows immediately after time t121 in one direction from the connection point Mouto to the connection point Mout1, but the absolute value of the current is gradually reduced to 0 [mA] shortly before time t122 ​​and is then held at 0 [mA] until time t131 is reached.

[0056] In the second quadrant, the H-bridge circuit 20Y of the Y-phase is operated in charging mode. At this time, the upper bridge-side switching element of one branch at connection point Mout2 of the H-bridge circuit 20Y and its lower bridge-side switching element of one branch at connection point Mout3 are switched on. In this way, connection point Mout2 conducts current to the DC power source 140 to apply the supply voltage MVdd, and connection point Mout3 conducts current to ground 142 and thus becomes 0 [V]. The coil current IMY of the Y-phase flows in one direction from connection point Mout2 to connection point Mout3, and the absolute value of the current gradually increases.

[0057] The third quadrant is the period from time t131 to time t141. In this third quadrant, the H-bridge circuit 20X of the X-phase is operating in charging mode. At this time, the upper bridge-side switching element 2 of the branch at connection point Mout1 of the H-bridge circuit 20X and its lower bridge-side switching element 8 of the branch at connection point Mouto are switched on. In this way, connection point Mout1 conducts current to the DC power source 140 to apply the supply voltage MVdd, and connection point Mouto conducts current to ground 142, so that the applied voltage becomes 0 [V]. The coil current IMX of the X-phase flows in one direction from connection point Mout1 to connection point Mouto, and simultaneously, an absolute value of the current is gradually increased.

[0058] In this third quadrant, all switching elements of the H-bridge circuit 20Y of the Y-phase are switched off, and the H-bridge circuit is operated in high-dissipation mode from time t131 to time t132 and in currentless mode after time t132.

[0059] Immediately after time t131, the voltage VMout3 at connection point Mout3 of the Y-phase becomes greater than or equal to (+MVdd + Vf) [V] due to the feedback pulse and is clamped by the diode. Simultaneously, the voltage VMout2 at connection point Mout2 becomes less than or equal to (-Vf) [V] and is clamped by the diode. The voltage values ​​of VMout3 and VMout2 at connection point Mout2 are maintained for a predetermined period. At time t132, the voltage VMout3 is abruptly reduced to 0 [V]. Later than VMout3, the voltage VMout2 is slightly increased and then gently reduced back to 0 [V] at time t141.The coil current IMY of the Y-phase flows immediately after time t131 in one direction from connection point Mout2 to connection point Mout3, but the absolute value of the current is gradually reduced to 0 [mA] shortly before time t132 and is then held at 0 [mA] until time t141 is reached.

[0060] The fourth quadrant is a period from time t141 to time t151. In this fourth quadrant, all switching elements 2, 4, 6 and 8 of the H-bridge circuit 20X of the X-phase are switched off and the H-bridge circuit is operated in high-dissipation mode from time t141 to time t142 and in de-energized mode after reaching time t142.

[0061] Immediately after time t141, the voltage VMouto at the Mouto junction of the X-phase becomes greater than or equal to (+MVdd + Vf) [V] due to the feedback pulse and is clamped by diode 16. Furthermore, the voltage VMout1 at the Mout1 junction becomes less than or equal to (-Vf) [V] and is clamped by diode 14. The voltage values ​​of VMouto at the Mouto junction and VMout1 at the Mout1 junction are maintained for a predetermined period. At time t142, the voltage VMouto is suddenly reduced to 0 [V]. Later than the voltage VMouto, the voltage VMout1 is slightly increased and then gently reduced back to 0 [V] at time t151.The coil current IMX of the X-phase flows immediately after time t141 in one direction from connection point Mout1 to connection point Mouto, but the absolute value of the current is gradually reduced to 0 [mA] shortly before time t142 and is then held at 0 [mA] until time t151 is reached.

[0062] In the fourth quadrant, the H-bridge circuit 20Y of the Y-phase is operated in charging mode. At this time, the upper bridge-side switching element of one branch at junction Mout3 of the H-bridge circuit 20Y and the lower bridge-side switching element of one branch at junction Mout2 are switched on. In this way, junction Mout3 conducts current to the DC power source 140 to apply the supply voltage MVdd, and junction Mout2 conducts current to ground 142 to become 0 V. The coil current IMY of the Y-phase flows in one direction from junction Mout3 to junction Mout2, and the absolute value of the current is gradually increased.

[0063] As the motor 120 rotates, the waveforms repeat from the first quadrant to the fourth quadrant.

[0064] A power loss P on The current supply period can be calculated from the following equation (1). Pon=Irms2×(RdsH+RdsL) where: P on a power loss during the current supply period; I rms an effective value of a coil current; R dsH a resistance exists between the drain and source of the upper bridge-side switching element when the upper bridge-side switching element is turned on; and R dsL a resistance exists between the drain and source of the lower bridge-side switching element when the lower bridge-side switching element is turned on.

[0065] A power loss P off1 The high-dissipation period can be calculated from the following equation (2) if no current returns to the DC source 140 and all the current leaks to ground 142 due to the parasitic transistor effect. Poff1=((lpeak2×Vf)+(lpeak2×(MVdd+Vf)))×Dfly where: P off1a power loss during the high dissipation period; I peak the maximum coil current is; V f a voltage drop in the forward direction of the diode; and D fly a ratio of the high-dissipation period for each quadrant.

[0066] No power loss occurs during the period when the current is off, as current rarely flows in coil 124. The power loss P at an electrical angle of the two-phase stepper motor can be calculated from the following equation (3). P=(Pon+Poff1)×4 where: P is the power loss for each electrical angle of the stepper motor.

[0067] As expressed in equations (1) to (3), the supply voltage MVdd, the coil current and the ratio of the high-dissipation period have a strong effect on the power dissipation P. Therefore, a large power dissipation occurs under the parasitic transistor effect.

[0068] Fig. Figure 10 is a flowchart illustrating the processing of the first quadrant of the X-phase of a device for controlling a motor drive, as described in the comparative example. Furthermore, octagons shown in the flowchart illustrate the state of the H-bridge circuits 20X and 20Y.

[0069] The X-phase starts the first quadrant from the current-energizing period. A bridge control circuit 110 switches on the upper bridge-side switching element 6 of the branch at connection point Mouto and the lower bridge-side switching element 4 of the branch at connection point Mout1 in the H-bridge circuit 20X of the X-phase (step S30). In this way, the H-bridge circuit 20X of the X-phase applies a current in the first quadrant. At this time, a difference between the voltage VMouto and the voltage VMout1 becomes the supply voltage MVdd (step S31). Current flows from connection point Mouto to connection point Mout1, so that the motor 120 is rotated and the absolute value of the coil current IMX gradually increases (step S32).

[0070] If the back EMF of the Y-phase voltage VMY experiences a zero crossing (Yes in step S32), the upper bridge-side switching element 6 of the branch at the connection point Mouto of the X-phase and its lower bridge-side switching element 4 of the branch at the connection point Mout1 are switched off (step S34), switching the X-phase into the high-dissipation period. This makes the voltage VMouto equal to the voltage VMout1 (step S35), thus completing the first quadrant.

[0071] In the first quadrant, the H-bridge circuit 20Y of the Y-phase assumes a voltage waveform in which the reverse voltage and the back EMF cancel each other out. In an initial stage of the first quadrant, the back EMF is generated by the rotation of the motor. However, because all switching elements are simultaneously switched off in a final stage of a preceding fourth quadrant, the reverse voltage is induced by the coil 124Y in a direction opposite to the previous current, and then a switch to the high-dissipation period occurs. Due to this reverse voltage, the voltage VMout2 becomes greater than or equal to the sum of the supply voltage MVdd and a forward voltage drop Vf across the diode and is clamped by the diode. Furthermore, the voltage VMout3 becomes less than or equal to the forward voltage drop Vf across the diode and is clamped by the diode.The voltage values ​​of voltage VMout2 or voltage VMout3 are maintained for a predetermined period of time.

[0072] In this way, a current path is formed through which current flows from ground 142 through coil 124Y back to the DC power source 140, so that the absolute value of the coil current IMY decreases at high speed until it reaches 0 [mA] and the reverse voltage is lifted. The H-bridge circuit 20Y of the Y-phase is switched to the no-current position by lifting the reverse voltage. Therefore, the back EMF between junction point Mout2 and junction point Mout3 appears due to the rotation of the motor. When the back EMF of the voltage VMY of the Y-phase crosses zero, step S32 is executed and the first quadrant is completed.

[0073] Fig. Figure 11 is a flowchart illustrating the processing of a second quadrant of the X-phase of the device for controlling the motor control according to the comparative example.

[0074] In the second quadrant, the H-bridge circuit 20X of the X-phase assumes a voltage waveform in which the reverse voltage and the back EMF cancel each other out. In the initial stage of the second quadrant, the back EMF is generated by the rotation of the motor. However, because all switching elements are simultaneously switched off in the final stage of the preceding fourth quadrant, the reverse voltage is induced by the coil 124Y in a direction opposite to that of the preceding current, and then a switch to the high-dissipation period takes place.

[0075] In the initial stage of the second quadrant, the H-bridge circuit 20X of the X-phase has the voltage VMouto and the voltage VMout1, which are equal to each other (step S40). Subsequently, the energy accumulated in the coil 124X is released and the coil current IMX decreases (step S41), so that the return voltage is induced between the junction point Mout1 and the junction point Mouto (step S41).

[0076] The reverse voltage of the X-phase causes the voltage VMouto to become greater than or equal to the sum of the supply voltage MVdd and the forward voltage drop Vf of diode 12, and this voltage is clamped by diode 16. Furthermore, the voltage VMout1 becomes less than or equal to the forward voltage drop Vf of diode 18 and is clamped by diode 14. The voltage values ​​of VMouto and VMout1 are maintained for a predetermined period. In this way, a current path is formed, causing current to flow from ground 142 through diode 18, inductor 124X, and diode 12 back to the DC power source 140, thus reducing the absolute value of the inductor current IMX at high speed to 0 mA (step S43) and transitioning to the currentless period.

[0077] During the power-off period, the back EMF between connection point Mout1 and connection point Mouto appears due to the rotation of the motor (step S44). The back EMF VMX of the X-phase passes through a zero crossing (step S44 > Yes), thus completing the second quadrant.

[0078] In the second quadrant, the H-bridge circuit 20Y of the Y-phase performs a process that corresponds to the operating mode of the X-phase of Fig. 10 corresponds to this. That is, the H-bridge circuit 20Y of the Y-phase switches on the upper bridge-side switching element of the branch at connection point Mout2 and the lower bridge-side switching element of the branch at connection point Mout3 (corresponds to step S30 of Fig. 10) and applies current. A difference between the voltage VMout2 and the voltage VMout3 is converted to the voltage MVdd (corresponds to step S31 of Fig. 10) At this time, current flows from connection point Mout2 to connection point Mout3, causing the motor to rotate 120° and the absolute value of the coil current IMY to gradually increase (corresponds to step S32 of Fig. 10).

[0079] If the back EMF VMX of the X-phase passes through a zero crossing (corresponds to step S33 of Fig. 10 > Yes), the upper bridge-side switching element of the branch at connection point Mout2 of the Y-phase and the lower bridge-side switching element of the branch at connection point Mout3 are switched off (corresponds to step S34 of Fig. 10) and the Y-phase is switched to the high-dissipation period. This makes the voltage VMout2 equal to the voltage VMout3 (corresponds to step S35 of Fig. 10), so that the second quadrant is completed.

[0080] The Fig. 3A and Fig. 3D are explanatory views that illustrate an operating mode of the H-bridge circuit 20 according to the embodiment.

[0081] Fig. Figure 3A illustrates the operation of the H-bridge circuit 20 in charging mode, which is the same as that of the H-bridge circuit 20 from Fig. 8A. The H-bridge circuit 20 is switched to the high-dissipation period after the charging mode in the same way as the comparison example. Fig. 3B switched.

[0082] Fig. Figure 3B illustrates the operation of the H-bridge circuit 20 during the high-dissipation period, which is the same as the high-dissipation mode of the H-bridge circuit 20 from Fig. 8B. The H-bridge circuit 20 of the comparative example maintains the high-dissipation mode during the generation of the feedback voltage. However, the H-bridge circuit 20 of the first embodiment is configured such that after a predetermined time, the switching element 2 is switched from an off state to an on state, and consequently the H-bridge circuit enters a low-dissipation mode. Fig. 3C is switched.

[0083] Fig. Figure 3C illustrates the operation of the H-bridge circuit 20 in low-dissipation mode.

[0084] The energy accumulated in coil 124 causes current to flow through switching element 8, coil 124, and switching element 2 in a direction indicated by the thick line. This means that the upper bridge-side switching element 2, arranged in a motor current flow direction indicated by the thick line, assumes a conducting state, and the energy accumulated in coil 124 causes a current flow in a closed circuit formed by the conducting upper bridge-side switching element 2 and the lower bridge-side switching element 8. The lower bridge-side switching element 8 is located on a side of the bridge circuit opposite to the motor current flow direction shown by the thick line. In the low-dissipation mode of Fig. In 3C, the power loss is solely due to the on-resistance of switching elements 8 and 2 and is lower than during the high-dissipation mode. Even if the H-bridge circuit 20 of the embodiment is manufactured using a CMOS fabrication process, there is no instance where current leaks to ground 142 due to the parasitic transistor effect and thereby generates heat, thus preventing further energy dissipation. The period during which the H-bridge circuit 20 operates in the low-dissipation mode is referred to as the "reverse period".

[0085] If the coil 124 has enough energy from the state of Fig. When 3C is released, the direction of the current is reversed, thereby switching to the state of Fig. Performed in 3D.

[0086] Fig. 3D is a view that illustrates the operation of the H-bridge circuit 20 in low-dissipation mode.

[0087] Here, the current flows through switching element 2, coil 124, and switching element 8 in the direction indicated by the thick line. When a mirror current for the aforementioned current flows in switching element 17, and a minimum current threshold transition, preset by the D / A converter 115, is detected by the comparator 114, a switch to the state of Fig. 3E. Furthermore, the comparator 114 is used to measure the positive current of the coil 124 for the purposes of controlling and detecting the current.

[0088] Fig. 3E is a view illustrating the operation of the H-bridge circuit 20 in the de-energized mode, which is the same as that of the H-bridge circuit 20 from Fig. 8C. The bridge control circuit 110 is switched to the next quadrant by detecting the zero crossing of the back EMF of the motor 120 during the de-energized period. Furthermore, the H-bridge circuit 20 is switched back to charging mode. Fig. 3A switched.

[0089] Fig. Figure 4 shows a waveform representation illustrating current sequences of an X-phase and a Y-phase of the H-bridge circuit 20.

[0090] In a similar way to Fig. 9 shows the waveform representation of Fig. Figure 4 shows the voltage VMouto of the X-phase as a solid line and the setting of switching element 6 as a dashed line. The voltage VMout1 of the X-phase is shown as a thick line and the setting of switching element 2 as a thick dashed line. This thick dashed line is at a high level when each switching element is on and at a low level when each switching element is off. Furthermore, the coil current IMX and the operating mode of the X-phase are also shown. Fig. 9 shown.

[0091] The waveform display of Fig. Figure 4 shows the voltage Mout2 of the Y-phase as a thick line and the setting of the upper bridge-side switching element of a branch at connection point Mout2 as a thick dashed line. The voltage VMout3 of the Y-phase is shown as a thick line, and the setting of the upper bridge-side switching element on a branch at connection point Mout3 is shown as a thick dashed line. Furthermore, the coil current IMY and the operating mode of the Y-phase are also shown in Figure 4. Fig. 4 shown.

[0092] The motor controller 100 of the embodiment drives the motor 120 in a phase excitation in response to the motor driver voltage and load, as in the comparative example. The motor 120 rotates by generating an electrical angle with four phases (quadrants). When the X-phase of the current-energizing period (see Fig. 3A) in any quadrant, the Y phase passes through the high-dissipation period (see Fig. 3B), which then becomes the return period (see Fig. 3C and Fig. 3D) and then assumes the power outage period (see Fig. 3E).

[0093] When the motor control voltage is high or the load is low, the speed of motor 120 increases, and the maximum current through coil 124 decreases. When the motor drive load is low, the reverse pulse time is shortened. The back EMF is generated during the no-current period of each phase. The back EMF is high when the motor speed is high and becomes 0 [V] at standstill, so it can be used to detect step loss.

[0094] In Fig. Quadrant 4 represents the first quadrant, a period from time t11 to time t21. During this first quadrant, the H-bridge circuit 20X of the X-phase operates in charging mode. At this time, the upper bridge-side switching element 6 of the branch at connection point Mouto of the H-bridge circuit 20X and its lower bridge-side switching element 4 of the branch at connection point Mout1 are switched to the on state. In this way, connection point Mouto conducts current to the DC power source 140 to apply the supply voltage MVdd, and connection point Mout1 conducts current to ground 142 to become 0 [V]. The coil current IMX of the X-phase flows in one direction from connection point Mouto to connection point Mout1, with an absolute value of the current gradually increasing.

[0095] In the initial stage of the first quadrant, all switching elements of the H-bridge circuit 20Y of the Y-phase are switched off, and the H-bridge circuit is operated in high-dissipation mode for a short period (predetermined period) after time t11. During this time, the voltage VMout2 of the Y-phase becomes greater than or equal to (+MVdd + Vf) [V] due to the freewheeling pulse and is clamped by the diode. Furthermore, the voltage VMout3 becomes less than or equal to (-Vf) [V] and is clamped by the diode. The voltage values ​​of VMout2 and VMout3 are maintained for a predetermined period. The coil current IMY of the Y-phase flows in one direction from junction Mout3 to junction Mout2. The description of the high-dissipation mode is further detailed below. Fig. 4 omitted.

[0096] After a predetermined period has elapsed from time t11, the upper bridge-side switching element of the branch at connection point Mout2 of the H-bridge circuit 20Y and the lower bridge-side switching element of the branch at connection point Mout3 are switched to the on state, and operation in low-dissipation mode is carried out until time t13. Furthermore, the low-dissipation mode is in Fig. 4 simply labelled "T".

[0097] At this time, the voltage VMout2 of the Y-phase becomes (+MVdd) [V] and the voltage VMout3 becomes 0 [V]. The coil current IMY of the Y-phase flows in one direction from junction Mout3 to junction Mout2, and its absolute value gradually decreases, so that the zero crossing and the reversal process occur at time t12. At time t13, the coil current IMY crosses the minimum current threshold.

[0098] In low-dissipation mode, the bridge control circuit 110 sets the minimum current threshold in advance using the D / A converter 115 and periodically detects, using the comparator 114, that the coil current IMY exceeds the minimum current threshold. When the coil current IMY exceeds the minimum current threshold, the bridge control circuit 110 switches off the upper bridge-side switching element of the branch at connection point Mout2 and the lower bridge-side switching element of the branch at connection point Mout3. This occurs at time t13. This control method ensures that power loss is optimally avoided depending on the operating conditions, such as the supply voltage MVdd or the load supplied to the motor 120.

[0099] If the switching off of the switching element is delayed when the rewind period ends, voltages on opposite sides of the coil are balanced by the supply voltage MVdd supplied to the motor 120, allowing the voltage waveform to be dispersed. The coil current IMY is significantly reduced compared to a peak of the freewheeling pulse, but the supply voltage MVdd supplied to the motor 120 is applied in a direction opposite to the motor's direction of rotation to act as a brake against the motor's rotation. This can be achieved by adjusting the minimum current threshold of the D / A converter 115 that can be detected by the comparator 114 and by shortening the sampling cycle of the comparator 114.

[0100] At time t13, all switching elements 2, 4, 6, and 8 are in the off state, and operation then proceeds in de-energized mode. At this time, the voltage VMout2 is suddenly reduced to 0 [V], and the voltage VMout3 is suddenly increased and then, at time t21, reduced again to 0 [V] via a ramp. The coil current IMY becomes 0 [mA].

[0101] The second quadrant is the period from time t21 to time t31. In the initial stage of this second quadrant, all switching elements 2, 4, 6, and 8 in the H-bridge circuit 20X of the X-phase are switched off, and the H-bridge circuit operates in high-dissipation mode for a short period (predetermined period) after time t21. At this time, the voltage VMout1 of the X-phase is increased by the freewheeling pulse to greater than or equal to (+MVdd + 2Vf) [V] and is clamped by diode 12. Furthermore, the voltage VMouto becomes less than or equal to (-Vf) [V] and is clamped by diode 18. The voltage values ​​of MVout1 and MVouto are maintained for a predetermined period. The coil current IMX of the X-phase flows in one direction from the connection point Mouto to the connection point Mout1, but the absolute value of the current is gradually reduced, so that at time t22 the zero crossing and the reversal process take place.At time t23, the absolute value of the coil current IMX exceeds the minimum current threshold.

[0102] In low-dissipation mode, the bridge control circuit 110 pre-sets the minimum current threshold using the D / A converter 115 and periodically detects, using the comparator 114, that the coil current IMX exceeds the minimum current threshold. When the coil current IMX exceeds the minimum current threshold, the bridge control circuit 110 switches off the upper bridge-side switching element 2 of the branch at junction point Mout1 and the lower bridge-side switching element 8 of the branch at junction point Mouto. This occurs at time t23.

[0103] At time t23, all switching elements 2, 4, 6, and 8 are in the off state, and operation then proceeds in de-energized mode. At this time, the voltage VMout1 is suddenly reduced to 0 [V], and the voltage VMouto is suddenly increased and then, at time t31, reduced again to 0 [V] via a ramp. The coil current IMX becomes 0 [mA].

[0104] In the second quadrant, the H-bridge circuit 20Y of the Y-phase is operated in charging mode. At this time, the upper bridge-side switching element of the branch at connection point Mout2 of the H-bridge circuit 20Y and its lower bridge-side switching element at connection point Mout3 are switched to the on state. In this way, connection point Mout2 conducts current to the DC power source 140 to apply the supply voltage MVdd, and connection point Mout3 conducts current to ground 142 and becomes 0 [V]. The coil current IMY of the Y-phase flows in one direction from connection point Mout2 to connection point Mout3, and the absolute value of the current gradually increases.

[0105] The third quadrant is the period from time t31 to time t41. In this third quadrant, the H-bridge circuit 20X of the X-phase is operating in charging mode. At this time, the upper bridge-side switching element 2 of the branch at connection point Mout1 of the H-bridge circuit 20X and its lower bridge-side switching element 8 of the branch at connection point Mouto are switched on. In this way, connection point Mout1 conducts current to the DC power source 140 to apply the supply voltage MVdd, and connection point Mouto conducts current to ground 142, so that the applied voltage becomes 0 [V]. The coil current IMX of the X-phase flows in one direction from connection point Mout1 to connection point Mouto, and an absolute value of the current is gradually increased.

[0106] In the initial stage of the third quadrant, all switching elements of the H-bridge circuit 20Y of the Y-phase are switched off, and the H-bridge circuit is operated in high-dissipation mode for a short period (predetermined time) after time t31. At this time, the voltage MVout3 of the Y-phase is increased by the freewheeling pulse to or greater than (+ MVdd + Vf) [V] and is clamped by the diode. Furthermore, the voltage VMout2 becomes less than or equal to (- Vf) [V] and is clamped by the diode. The voltage values ​​of VMout3 and VMout2 are maintained for a predetermined period. The coil current IMY of the Y-phase flows in one direction from junction point Mout2 to junction point Mout3.

[0107] After a predetermined period of time has elapsed from time t31, the upper bridge side switching element of the branch at connection point Mout3 of the H-bridge circuit 20Y and the lower bridge side switching element of the branch at connection point Mout2 are switched to the on state and operation in low dissipation mode is carried out until time t33.

[0108] At this time, the voltage VMout3 of the Y-phase becomes (+MVdd) [V] and the voltage VMout2 becomes (0) [V]. The coil current IMY of the Y-phase flows in one direction from junction point Mout2 to junction point Mout3, and its absolute value gradually decreases, so that the zero crossing and the reversal process occur at time t32. At time t33, the coil current IMY exceeds the minimum current threshold.

[0109] In low-dissipation mode, the bridge control circuit 110 pre-sets the minimum current threshold using the D / A converter 115 and periodically detects, using the comparator 114, that the coil current IMY crosses the minimum current threshold. When the coil current IMY crosses the minimum current threshold, the bridge control circuit 110 switches off the upper bridge-side switching element of the branch at connection point Mout3 and the lower bridge-side switching element of the branch at connection point Mout2. This occurs at time t33.

[0110] At time t33, all switching elements are in the off state, and operation then proceeds in de-energized mode. At this time, the voltage VMout3 is suddenly reduced to 0 [V], and the voltage VMout2 is suddenly increased and then, at time t41, reduced again to 0 [V] via a ramp. The coil current IMY becomes 0 [mA].

[0111] The fourth quadrant is the period from time t41 to time t51. In the initial stage of this fourth quadrant, all switching elements 2, 4, 6, and 8 of the H-bridge circuit 20X of the X-phase are switched off, and the H-bridge circuit is operated in high-dissipation mode for a short period (predetermined period) after time t41. At this time, the voltage VMouto of the X-phase is increased by the freewheeling pulse to or greater than (+MVdd + 2Vf) [V] and is clamped by diode 16. Furthermore, the voltage VMout1 becomes less than or equal to (-Vf) [V] and is clamped by diode 14. The voltage values ​​of MVouto and MVout1 are maintained for a predetermined period.The coil current IMX of the X-phase flows in one direction from connection point Mout1 to connection point Mouto, and the absolute value of the current gradually decreases, so that at time t42 the zero crossing and the reversal process occur. At time t43, the absolute value of the coil current IMX exceeds the minimum current threshold.

[0112] In low-dissipation mode, the bridge control circuit 110 pre-sets the minimum current threshold using the D / A converter 115 and periodically detects, using the comparator 114, that the coil current IMX exceeds the minimum current threshold. When the coil current IMX exceeds the minimum current threshold, the bridge control circuit 110 switches off the upper bridge-side switching element 6 of the branch at junction point Mouto and the lower bridge-side switching element 4 of the branch at junction point Mout1. This occurs at time t43.

[0113] At time t43, all switching elements are in the off state, and operation then proceeds in de-energized mode. At this time, the voltage VMouto is suddenly reduced to 0 [V], and the voltage VMout1 is suddenly increased and then, at time t51, reduced again to 0 [V] via a ramp. The coil current IMX becomes 0 [mA].

[0114] In the fourth quadrant, the H-bridge circuit 20Y of the Y-phase is operated in charging mode. At this time, the upper bridge-side switching element of the branch at junction Mout3 of the H-bridge circuit 20Y and its lower bridge-side switching element of the branch at junction Mout2 are switched on. In this way, junction Mout3 conducts current to the DC power source 140 to apply the supply voltage MVdd, and junction Mout2 conducts current to ground 142 to become 0 V. The coil current IMY of the Y-phase flows in one direction from junction Mout3 to junction Mout2, and the absolute value of the current is gradually increased.

[0115] Motor 120 rotates while waveforms are repeated from the first quadrant to the fourth quadrant.

[0116] In this embodiment, for example, when the X-phase is in the energized period, the Y-phase is switched to the high-dissipation period, the discharge period, and the de-energized period. The power loss is reduced by switching to the discharge period.

[0117] It is assumed that in the high-dissipation mode of the embodiment, current does not return to the DC power source 140, but that all current leaks to ground 142 due to the parasitic transistor effect. In this case, the power dissipation P off2 represented by the following equation (4). Poff2=((lpeak2×Vf)+(lpeak2×(MVdd+Vf)))×Ddead where: P off2 a power loss during the high dissipation period; I peak the maximum coil current is; V f a voltage drop in the forward direction of the diode; and D deada time ratio of the high-dissipation period for each quadrant.

[0118] Since it passes through the switching element, the power loss P off3 the return period is represented by the following equation (5). Poff3=(lpeak2×RdsL+lpeak2×RdsH)×Dfly where: P off3 a loss of power during the return period; I peak the maximum coil current is; V f a voltage drop in the forward direction of the diode; R dsL A resistance exists between the drain and source of the lower bridge-side switching element when the lower bridge-side switching element is switched on. dsH a resistance exists between the drain and source of the upper bridge-side switching element when the upper bridge-side switching element is turned on; and D fly a ratio of the high-dissipation period for each quadrant.

[0119] The power loss P of an electrical angle of the two-phase stepper motor is represented by the following equation (6). P=(Pon+Poff2+Poff3)×4 where: P is the power loss for each electrical angle of the stepper motor.

[0120] As expressed in equation (5), since it passes through the switching element during the “reverse period”, the power dissipation is not affected by the supply voltage MVdd and the parasitic transistor effect. Therefore, it is possible to reduce the power dissipation.

[0121] Fig. Figure 5 is a waveform representation illustrating a voltage and current of each part of the X-phase of the H-bridge circuit 20.

[0122] The waveform display of Fig. Figure 5 shows the X-phase voltage VMX and the coil current IMX and the X-phase voltage VMouto and VMout1 in the waveform of an oscilloscope.

[0123] In the first quadrant, the upper bridge side switching element 6 of the branch at the connection point Mouto of the H-bridge circuit 20X and its lower bridge side switching element 4 of the branch at the connection point Mout1 are set to the on state.

[0124] The voltage VMX of the X-phase becomes (- MVdd) [V] and the X-phase coil current IMX flows in the direction from the junction point Mouto to the junction point Mout1 and the absolute value of the current is gradually increased.

[0125] Since the connection point Mouto conducts current to the DC power source 140, the voltage VMouto becomes (+MVdd) [V]. Since the connection point Mout1 conducts current to ground 142, the voltage VMout1 becomes 0 [V].

[0126] In the second quadrant, all switching elements 2, 4, 6 and 8 of the H-bridge circuit 20X are in the off state.

[0127] The X-phase voltage VMX is immediately after time t21 increased by the freewheeling pulse to or greater than (+MVdd + 2Vf) [V], clamped by diodes 12 and 18, and then switched to low-dissipation mode to increase to or greater than (+MVdd + Vf) [V], while simultaneously clamped by the diode so that this voltage value is maintained for a predetermined period. Shortly before time t23, the voltage VMX is abruptly reduced to pass through zero, and after decreasing to a predetermined voltage, it is gradually increased to pass through zero again at time t31. The coil current IMX of the X-phase flows immediately after time t21 in a (positive) direction from the connection point Mouto to the connection point Mout1, but the absolute value of the current is gradually reduced, so that the current (- IMX) becomes greater than the minimum current threshold at time t23 and returns to 0 [mA].The current is then held at 0 [mA] until time t31 is reached.

[0128] The voltage VMouto at the Mouto connection point is immediately reduced by the freewheeling pulse (-Vf) [V] after time t21, clamped by diode 18, and then switched to low-dissipation mode, reaching 0 [V] by time t23. This voltage is gradually increased to a predetermined value and then reduced by the back EMF of motor 120 after time t23, so that the voltage returns to 0 [V] at time t31.

[0129] The voltage VMout1 at connection point Mout1 is immediately after time t21 increased by the freewheeling pulse to or equal to (+MVdd + Vf) [V], clamped by diode 12, and then switched to low-dissipation mode to become (+MVdd [V]). This voltage is maintained for a predetermined period. At time t23, the voltage VMout1 is abruptly reduced to 0 [V] and then held at 0 [V] until time t31.

[0130] In the third quadrant, the upper bridge side switching element 2 of the branch at connection point Mout1 of the H-bridge circuit 20X and its lower bridge side switching element 8 of the branch at connection point Mouto are set to the on state.

[0131] The voltage VMX of the X-phase is (+ MVdd) [V], so that the X-phase coil current IMX flows in the direction from junction point Mout1 to junction point Mouto and the absolute value of the current is gradually increased.

[0132] Since the connection point Mouto conducts current to ground 142, the voltage VMouto then becomes 0 [V]. Since the connection point Mout1 conducts current to the DC source 140, the voltage VMout1 (+ MVdd) [V].

[0133] In the fourth quadrant, all switching elements 2, 4, 6, and 8 of the H-bridge circuit 20X are switched off. Immediately after time t41, the voltage VMX of the X-phase is reduced by the freewheeling pulse to less than or equal to (-MVdd - 2Vf) [V], clamped by diodes 14 and 16, and then switched to low-dissipation mode to become less than or equal to (-MVdd) [V]. This voltage value is maintained for a predetermined period. Shortly before time t43, the voltage VMX is suddenly increased to pass through zero and, after being increased to a predetermined voltage, is gradually decreased to pass through zero again at time t51.The coil current IMX of the X-phase flows in a (negative) direction from connection point Mout1 to connection point Mouto immediately after time t41, but the absolute value of the current k is gradually reduced so that at time t43 the current becomes greater than the minimum current threshold and then returns to 0 [mA]. ​​After this, the current is held at 0 [mA] until time t51 is reached.

[0134] The voltage VMouto at junction Mouto is immediately reduced to or equal to (+MVdd + Vf) [V] by the freewheeling pulse after time t41. It is clamped by diode 16 and then switched to low-dissipation mode, becoming (+MVdd) [V]. This voltage value is maintained for a predetermined period. At time t43, the voltage VMouto is abruptly reduced to 0 [V] and is held at 0 [V] until time t51.

[0135] The voltage VMout1 of terminal Mout1 is immediately reduced by the reverse pulse (-Vf) [V] after time t41, clamped by diode 14, and then switched to low-dissipation mode, reaching 0 [V] by time t43. This voltage is gradually increased to a predetermined value and then, after time t43, reduced by the back EMF of motor 120, so that the voltage returns to 0 [V] at time t51.

[0136] Fig. Figure 6 is a flowchart illustrating the processing of the first quadrant of the X-phase of the device for controlling the motor drive according to the embodiment. It is identical to the flowchart of the comparative example in Fig. 10, but differs in its Y-phase operating mode.

[0137] The X-phase starts the first quadrant of the current-energizing period. The bridge control circuit 110 switches on the upper bridge-side switching element 6 of the branch at connection point Mouto and the lower bridge-side switching element 4 of the branch at connection point Mout1 in the H-bridge circuit 20X of the X-phase (step S10). In this way, the H-bridge circuit 20X of the X-phase applies current in the first quadrant. At this time, a difference between the voltage VMouto and the voltage VMout1 is established relative to the supply voltage MVdd (step S11). Current flows from connection point Mouto to connection point Mout1, causing the motor 120 to rotate and the absolute value of the coil current IMX to gradually increase (step S12).

[0138] When the back EMF VMY of the Y-phase passes through a zero crossing ("Yes" in step S13), the upper bridge-side switching element 6 of the branch at connection point Mouto of the X-phase and its lower bridge-side switching element 4 of the branch at connection point Mout1 are switched off (step S14), switching the X-phase into the high-dissipation period. This makes the voltage VMouto equal to the voltage VMout1 (step S15), thus completing the first quadrant.

[0139] In the first quadrant, the H-bridge circuit 20Y of the Y-phase assumes a voltage waveform in which the reverse voltage and the back EMF cancel each other out. Initially, in the first quadrant, the back EMF is generated by the rotation of the motor. However, because all switching elements are simultaneously switched off in the final stage of the preceding fourth quadrant, the reverse voltage is induced by the coil 124Y in a direction opposite to that of the preceding current, and then a switch to the high-dissipation period occurs. This reverse voltage causes the voltage VMout2 to become greater than or equal to the sum of the supply voltage MVdd and the forward voltage drop Vf across the diode, and it is clamped by the diode. Furthermore, the voltage VMout3 becomes less than or equal to the forward voltage drop Vf across the diode and is also clamped by the diode.The voltage values ​​of VMout2 and MVout3 are maintained for a predetermined period. In this way, a current path is formed to cause current to flow from ground 142 through coil 124Y to the DC power source 140.

[0140] After a predetermined period, the H-bridge circuit 20Y switches the upper bridge-side switching element, which is oriented in the direction of the coil current IMY, and the lower bridge-side switching element, which is oriented in the opposite direction on one side, to conduct, thus switching it into low-dissipation mode. The current path is formed to cause current to flow from ground 142 through the coil 124Y back to the DC power source 140, so that the absolute value of the coil current IMY decreases until it reaches 0 mA, and the return voltage is eliminated. The Y-phase of the H-bridge circuit 20Y then switches to the no-current period when the direction of the coil current IMY is reversed and (- IMY) exceeds the minimum current threshold. Therefore, the back EMF between connection point Mout2 and connection point Mout3 appears due to the rotation of the motor.When the counter-EMF VMY of the Y phase experiences a zero crossing, the aforementioned step S14 is performed and the first quadrant is completed.

[0141] Fig. Figure 7 is a flowchart illustrating the processing of the second quadrant of the X-phase of the device for controlling the drive of the motor according to the embodiment.

[0142] In the second quadrant, the H-bridge circuit 20X of the X-phase assumes a voltage waveform in which the reverse voltage and the back EMF cancel each other out. In an initial stage of the second quadrant, the back EMF is generated by the rotation of the motor. However, because all switching elements 2, 4, 6, and 8 are simultaneously switched off in a final stage of the preceding first quadrant, the reverse voltage is induced in a direction opposite to that of the preceding current, and a switch to the high-dissipation period then occurs.

[0143] In the initial stage of the second quadrant, the H-bridge circuit 20X of the X-phase has the voltage VMouto and the voltage VMout1, which are equal to each other (step S20). Subsequently, energy accumulated in the coil 124X is released and the coil current IMY decreases (step S21), and then the return voltage is induced between the junction point Mout1 and the junction point Mouto (step S22).

[0144] When a predetermined time has elapsed, the X-phase reverse voltage causes the voltage VMouto to be greater than or equal to the sum of the supply voltage MVdd and the forward voltage drop Vf of the diode, and is clamped by diode 16. It also causes the voltage VMout1 to be less than or equal to the forward voltage drop Vf of diode 18, and is clamped by diode 18. The voltage values ​​of MVouto and VMout1 are maintained for a predetermined period. In this way, the current path is formed to cause current to flow from ground 142 through diode 18, inductor 124X, and diode 12 back to the DC power source 140.

[0145] The bridge control circuit 110 switches on the upper bridge-side switching element 2 of the branch at junction point Mout1 and the lower bridge-side switching element 8 of the branch at junction point Mouto (step S23) and switches into the reverse cycle. During the reverse cycle, the current path is formed to cause current to flow from ground 142 through switching element 8, coil 124X, and switching element 2 back to the DC power source 140, and the coil current IMX is reduced at high speed until it reaches 0 mA. This is referred to as the low-dissipation mode, which has a lower dissipation than the high-dissipation mode.

[0146] During the reverse cycle, the bridge control circuit 110 performs a zero crossing of the coil current IMX (step S24) and then determines whether the current (-IMX) is greater than or equal to the minimum current threshold (step S25). If the current (-IMX) is greater than or equal to the minimum current threshold ("Yes" in step S25), the bridge control circuit 110 switches off the upper bridge-side switching element 2 of the branch at connection point Mout1 and the lower bridge-side switching element 8 of the branch at connection point Mouto (step S26) and switches to the de-energized cycle. If the bridge control circuit 110 detects in step S25 that the coil current IMX flowing in coil 124 is flowing in the opposite direction to the charging mode, the switch to the de-energized cycle is performed.

[0147] During the power-off period, the back EMF appears between connection point Mouto and connection point Mout1 (step S27). The bridge control circuit 110 attempts to detect the zero crossing of the back EMF generated in the voltage VMX using the back EMF detector 118 (step S28). If the back EMF experiences a zero crossing ("Yes" in step S28), the second quadrant is closed.

[0148] The bridge control circuit 110 switches on the upper bridge-side switching element 2 of the branch at connection point Mout1 and the lower bridge-side switching element 8 of the branch at connection point Mouto (step S23), thus operating in low-dissipation mode, which has a lower dissipation than the high-dissipation mode. Therefore, it is possible to reduce power loss. Furthermore, when the current (-IMX) becomes greater than or equal to the minimum current threshold, the bridge control circuit 110 switches off the upper bridge-side switching element 2 of the branch at connection point Mout1 and the lower bridge-side switching element 8 of the branch at connection point Mouto, thus ending the low-dissipation mode. Therefore, nothing interferes with the measurement of the back EMF and the detection of step loss after the freewheeling pulse has ended, so the motor 120 is not decelerated.

[0149] In the second quadrant, the H-bridge circuit 20Y of the Y-phase performs a process of the X-phase operating mode of Fig. 6 off. This means that the H-bridge circuit 20Y of the Y-phase switches on the upper bridge-side switching element of the branch at connection point Mout2 and the lower bridge-side switching element of the branch at connection point Mout3 (corresponds to step S10 of Fig. 6) and applies current. A difference between the voltage VMout2 and the voltage VMout3 is converted to the voltage MVdd (corresponds to step S11 of Fig. 6) At this time, the current flows from connection point Mout2 to connection point Mout3, so the motor rotates at 120° and the absolute value of the coil current IMY gradually increases (corresponds to step S12 of Fig. 6).

[0150] If the back EMF VMX of the X-phase experiences a zero crossing (corresponds to Yes in step S13 of Fig. 6), the upper bridge-side switching element of the branch at connection point Mout2 of the Y-phase and its lower bridge-side switching element of the branch at connection point Mout3 are switched off (corresponds to step S14 of Fig. 6), and the Y-phase is switched to the high-dissipation period. The voltage VMout2 of the Y-phase temporarily becomes equal to the voltage VMout3 (corresponds to step S15 of Fig. 6), so that the second quadrant is complete.

[0151] In this embodiment, since the comparator 114, the D / A converter 115, and the current detector 116, which are designed for micro-stepping control, are used to detect the end of the reverse rotation, this can be done without increasing costs. Even if the supply voltage MVdd, the load torque, or the rotational speed are changed, no power loss or braking occurs.

[0152] According to this embodiment, it is possible to detect the end time of the freewheeling pulse and to switch off the switching element during this time. Therefore, this does not affect the measurement of the back EMF or the detection of a step loss after the freewheeling pulse has ended. Furthermore, since the motor 120 is not braked, this does not affect the motor's performance at maximum speed.

[0153] The present invention is not limited to the embodiments mentioned above, but can be modified without departing from its spirit. For example, the following modifications a) to i) are possible. a) The present invention is not limited to a two-phase stepper motor, but can be used with a motor with any number of phases, for example, a three-phase stepper motor. Furthermore, a brushless motor whose motor coil has a star connection or a delta connection can also be used. b) The switching element is not limited to a MOSFET, but can be any type of semiconductor switching element. c) At least some of the relevant components of the engine control system can be implemented not only as hardware but also as software. d) At least part of the drive control device may be an integrated circuit (IC). e) The circuit block configuration of the in the Fig. 1 and Fig. The motor control unit shown in section 2 is a specific example and the invention is not limited to this. f) The one in the Fig. 6 and Fig. The control flow shown in step 7 is merely an example and is not limited to these steps; for example, other steps can be inserted between the steps. g) The transition from the high-dissipation mode to the low-dissipation mode is not limited to the elapsed time, but can be brought about by the zero crossing of the return voltage. h) The H-bridge circuit of the present invention cannot be limited by combining half-bridges with each other.

[0154] As described in the embodiments, according to the present invention a motor control and a method for controlling a motor are provided which have the capability to allow the current discharged to ground to be returned to the power source, thereby making it possible to reduce power loss.

Claims

[1] Engine control (100), comprising: an H-bridge circuit (20, 20X, 20Y) comprising switching elements (2, 4, 6, 8), freewheeling diodes and half bridges connected to motor coils provided in the motor (120); a current detector (116) that detects a current flowing in the motor coil (124); a zero-crossing detector that detects a zero-crossing of a back EMF of each of the motor coils; and a controller that operates the H-bridge circuit (20, 20X, 20Y) in one of various operating modes, wherein the operating modes include a charging mode, a high-dissipation mode, a low-dissipation mode and a power-off mode, and wherein the operating mode is set on the basis of the motor current detected by the current detector (116) by activating the switching elements (2, 4, 6, 8) of the H-bridge circuit (20, 20X, 20Y), wherein the H-bridge circuit (20, 20X, 20Y) increases a motor current flowing in the respective motor coils in the charging mode, wherein in the high-dissipation mode the H-bridge circuit (20, 20X, 20Y) operates with a high energy dissipation and a freewheeling pulse is induced in each of the motor coils, wherein in the low dissipation mode the H-bridge circuit (20, 20X, 20Y) operates with a low energy dissipation which is lower than in the high dissipation mode, wherein the H-bridge circuit (20, 20X, 20Y) is operated such that the zero-crossing detector is enabled to detect the zero crossing of the back EMF of each of the motor coils after the freewheeling pulse of each of the motor coils has decreased, wherein the controller is further operated to perform a process comprising: Controlling the H-bridge circuit (20, 20X, 20Y) to switch to charging mode; Controlling the H-bridge circuit (20, 20X, 20Y) to switch to the high-dissipation mode when the zero-crossing detector detects that the back EMF of the motor coil (124) connected to a phase of the H-bridge circuit (20, 20X, 20Y) is about to experience a zero crossing; controlling the H-bridge circuit (20, 20X, 20Y) to switch to the low dissipation mode after a predetermined time has elapsed; and Controlling the H-bridge circuit (20, 20X, 20Y) to switch to the currentless mode when the motor current detector detects that the motor current flowing in the motor coil (124) connected to the H-bridge circuit (20, 20X, 20Y) flows in a direction opposite to that of the charging mode. [2] Motor controller (100) according to claim 1, wherein in the low dissipation mode, the controller switches one of the upper-bridge-side switching elements (2, 6) and one of the lower-bridge-side switching elements into conduction, wherein the upper-bridge-side switching element (2, 6) is arranged on a side of the H-bridge circuit (20, 20X, 20Y) in the direction of which the motor current flows, and wherein the lower-bridge-side switching element (4, 8) is arranged on a side of the H-bridge circuit (20, 20X, 20Y) which is opposite to the direction of flow of the motor current, so that a current flow in a closed circuit is caused due to the energy accumulated in the motor coil (124), wherein the closed circuit is formed by the upper-bridge-side switching element (2, 6) and the lower-bridge-side switching element (4, 8), each of which is in a conducting state. [3] Motor controller (100) according to claim 1 or 2, wherein in the high dissipation mode, the controller sets all switching elements (2, 4, 6, 8) of the H-bridge circuit (20, 20X, 20Y) into a non-conductive state and causes current to flow in a closed circuit due to the energy accumulated in the motor coil (124), wherein the closed circuit is formed by a freewheeling diode of the upper bridge side and a freewheeling diode of the lower bridge side, wherein the freewheeling diode of the upper bridge side is arranged on a side of the H-bridge circuit in the direction of which the current flows and wherein the freewheeling diode of the lower bridge side is arranged on a side of the H-bridge circuit (20, 20X, 20Y) opposite to the direction of flow of the motor current. [4] The motor controller (100) according to any one of claims 1 to 3, wherein the switching elements (2, 4, 6, 8) and the freewheeling diodes included in the H-bridge circuit (20, 20X, 20Y) are CMOS elements. [5] Motor controller (100) according to one of claims 1 to 4, wherein the current detector (116) comprises a current mirror circuit and a comparator (114). [6] Method for controlling an engine (120) with an engine controller (100), comprising: an H-bridge circuit (20, 20X, 20Y) comprising switching elements (2, 4, 6, 8), freewheeling diodes and half bridges connected to motor coils provided in the motor (120); a current detector (116) that detects a current flowing in the motor coil (124); a zero-crossing detector that detects a zero-crossing of a back EMF of each of the motor coils; and a controller which operates the H-bridge circuit (20, 20X, 20Y) in such a way that it is operated in one of various operating modes, wherein the operating modes include a charging mode, a high-dissipation mode, a low-dissipation mode and a power-off mode, and wherein the operating mode is set on the basis of the motor current detected by the current detector (116) by activating the switching elements (2, 4, 6, 8) of the H-bridge circuit (20, 20X, 20Y), wherein the H-bridge circuit (20, 20X, 20Y) increases a motor current flowing in the respective motor coils in the charging mode, wherein in the high-dissipation mode the H-bridge circuit (20, 20X, 20Y) operates with a high energy dissipation and a freewheeling pulse is induced in each of the motor coils, wherein in the low dissipation mode the H-bridge circuit (20, 20X, 20Y) operates with a low energy dissipation which is lower than in the high dissipation mode, wherein the H-bridge circuit (20, 20X, 20Y) is operated to enable the zero-crossing detector to detect the zero crossing of the back EMF of each of the motor coils after the freewheeling pulse of each of the motor coils is reduced, the method comprising: Controlling the H-bridge circuit (20, 20X, 20Y) to switch to charging mode; Controlling the H-bridge circuit (20, 20X, 20Y) to switch to the high-dissipation mode when the zero-crossing detector detects that the back EMF of the motor coil (124) connected to a phase of the H-bridge circuit (20, 20X, 20Y) is about to experience a zero crossing; controlling the H-bridge circuit (20, 20X, 20Y) to switch to the low dissipation mode after a predetermined time has elapsed; and Controlling the H-bridge circuit (20, 20X, 20Y) to switch to the currentless mode when the motor current detector detects that the motor current flowing in the motor coil (124) connected to the H-bridge circuit (20, 20X, 20Y) flows in a direction opposite to that of the charging mode.

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