DE20304578U1 - Electronically commutated motor with at least one Hall generator - Google Patents

Description

March 20, 2003
DE-3072 iG

Electronically commutated motor with at least one Hall generator

The invention relates to an electronically commutated motor (ECM) with at least one analog Hall generator.

An analogue Hall generator, which is often also referred to as a Hall sensor, contains a magnetic field-sensitive semiconductor plate through which a Hall current is passed in one direction via two current connections, which can be between 2 and 20 mA, for example. This plate also has two signal outputs on the side from which the so-called Hall voltage uh can be taken, which can be between 10 and 150 mV, for example, depending on the size of the Hall current and the magnetic field.

Such a semiconductor plate represents a resistance with a negative temperature coefficient, i.e. at 25° C, for example in the case of type HW101A (Asahi), depending on the batch, it has a resistance of between 240 and 550 Ω, while at a temperature of 110° C, as is often the case in an ECM, this resistance drops to approximately 100 Ω.

If such a Hall generator is connected in the usual way in series with a resistor at a constant voltage, it can happen that at higher temperatures the Hall voltage only reaches values of 10 mV, which is in the range of the noise signals and makes correct control of the commutation difficult in an electronically commutated motor.

It is therefore an object of the invention to provide a new electronically commutated motor.

According to a first aspect of the invention, this object is achieved by the subject matter of claim 1. By limiting the voltage drop at the measuring resistor, or in other words: the current through this measuring resistor, to a predetermined value once a predetermined temperature of the at least one Hall generator is exceeded, it is achieved that above this predetermined temperature the current through the Hall generator is essentially constant, so that this current can be set so that the Hall voltage is sufficiently high even at high temperatures, but on the other hand no

unnecessarily high currents occur (power limitation of the components used). Below the specified temperature, such a regulation is not necessary because at that point the at least one Hall generator has a sufficiently large internal resistance that limits the current through the Hall generator to a safe value. At high temperatures, the efficiency of an ECM can be improved in this way because the current through the Hall generator(s) does not exceed the value required for a sufficient Hall voltage.

This also makes it possible to reliably control the relatively widely differing resistance values of the Hall generators, which for the type mentioned above can be between 240 and 550 Ω for different batches (lots). In addition, only a few additional components are required, which is particularly important where there is little space in an ECM and/or prices are very low. In addition, operational reliability is increased across the entire operating temperature range.

According to a second aspect of the invention, the stated object is achieved by the subject matter of claim 10. Such a motor requires only a few additional components, which is particularly important where there is little space in an ECM. In addition, the power consumption of the Hall generators is limited in the range between the predetermined temperature and the maximum temperature of the motor, which reduces the heat loss in the motor and makes it possible to make the power supply of the at least one Hall generator smaller, thereby reducing the manufacturing costs of such a motor.

According to a third aspect of the invention, this object is achieved by the subject matter of claim 17. The series connection of the Hall generators results in a corresponding reduction in energy requirements, since the same current is used to power all Hall generators. These are at different potentials, but the use of the feedback comparators makes it possible to generate binary Hall signals that are related to the same potential. On the one hand, the current limitation enables reliable signal generation even at the highest operating temperature. On the other hand, the energy consumption for generating the Hall signals remains very low, even at high temperatures.

Further details and advantageous developments of the invention emerge from the exemplary embodiments described below and shown in the drawing, which are in no way to be understood as a limitation of the invention, as well as from the dependent claims. It shows:

Fig. 1 shows a first preferred embodiment of a sensor arrangement according to the invention, here for a three-phase ECM,

Fig. 2 is a diagram to explain Fig. 1,

Fig. 3 shows a second embodiment of a sensor arrangement according to the invention, also for a three-phase ECM, and

Fig. 4 shows a third embodiment of a sensor arrangement according to the invention.

Fig. 1 shows a first embodiment of a sensor arrangement 20 according to the invention, such as can be used for controlling commutation in a three-phase brushless DC motor (ECM). This arrangement contains three Hall generators 22, 24, 26, which are taken from the same batch, i.e. have approximately the same resistance values, and each of which has two power connections 28, 30 (Hall generator 22), 32, 34 (Hall generator 24) or 36, 38 (Hall generator 26). The power connection 28 is connected to a positive connection 48, to which a regulated voltage of + 5 V is applied, for example. The connection 30 is connected to the connection 32 and the connection 34 to the connection 36. The terminal 38 is connected via a resistor 40 to the collector of an npn transistor 42, the emitter of which is connected to ground 46 via a current measuring resistor 44 (e.g. 120 Ω).

A resistor 50 (e.g. 10 k) leads from the positive terminal 48 to the collector of an npn transistor 52, which is connected to the base of the transistor 42 via a resistor 54 (e.g. 10 k). The emitter of the transistor 52 is connected to ground, and its base is connected to the emitter of the transistor 42 via a resistor 58 (e.g. 47 k).

The Hall generator 22 has two outputs 60, 62, between which a

Hall voltage uh occurs, which is fed to the two inputs 66 (+) and 68 (-) of a comparator 64, the output of which is designated 70. This output 70 is connected to the positive input 66 via a positive feedback resistor 72. The analog Hall voltage uh is converted by the comparator 64 into a binary signal with the values "1" or "0".

A comparator 74 is assigned to the Hall generator 24, and a comparator 76 is assigned to the Hall generator 26. The circuit is obviously the same as for the Hall generator 22 and is therefore not described again.

How Fig. 1 works

During operation, a current i flows from terminal 48 via the three Hall generators 22, 24, 26, the resistor 40, the conductive transistor 42 and the measuring resistor 44 to ground and leads to a corresponding voltage drop at the measuring resistor 44.

In the low temperature range, the Hall generators 22, 24, 26 have a sufficiently high internal resistance, which for example for the above-mentioned type HW101A at 25° C can be in the range 240 to 550 Ω, but for the same batch deviates only slightly from a predetermined value, which is e.g. 300 Ω. In contrast, at 110° C the average value of this resistance is only 100 Ω.

The resistor 40 can have, for example, 200 Ω, the measuring resistor 44 120 Ω, so that at 25° C and an average value of 300 Ω for the resistance of a Hall generator 22, 24, 26, a total resistance of 3 x 300 + 200 + 120 = 1,220 Ω is obtained. This results in a current i of 5 V/1.22 kΩ = 4.1 mA, and a sufficiently large Hall voltage of, for example, uh = 150 mV is obtained.

At 110° C, the resistance of a Hall generator drops to about 100 Ω, and the total resistance is therefore 3 x 100 + 200 + 120 = 620 Ω, corresponding to a current of 5 V/0.62 kΩ = 8 mA. This current requires a suitably dimensioned power supply and in itself should not be so high, thus reducing the efficiency of the motor.

Therefore, according to Fig. 2, starting at temperature Ton, the current i is limited to a lower value, e.g. to 5 mA, since with this current a sufficiently large Hall voltage uh is obtained even at 110° C.

*· 1

·

·

The limitation is achieved by means of the measuring resistor 44. If a sufficiently high measuring voltage um occurs at this starting at the temperature Ton, this causes the transistor 52 to become more conductive via the resistor 58 (e.g. 47 k). This causes a larger voltage drop at the resistor 50 (e.g. 10 k), which reduces the base potential of the transistor 42 via the resistor 54, so that this transistor becomes less conductive and keeps the current i essentially constant once this predetermined temperature Ton is reached, as shown schematically in Fig. 2.

The upper limit value iG (Fig. 2) of the current i is set so that even at the highest temperature, e.g. 110° C, a sufficiently high Hall voltage Uh is obtained, which enables reliable operation of the comparators 64, 74, 76.

Fig. 3 shows a variant. Parts that are the same or have the same effect as in Fig. 1 are designated by the same reference numerals as there and are usually not described again.

The power connection 38 of the Hall generator 26 is, as in Fig. 1, connected via a resistor 40 to the collector of the npn control transistor 42, the emitter of which is connected to ground 46 via the measuring resistor 44. This emitter is also directly connected to the negative input 79 of an operational amplifier 80, the output 82 of which is connected to the base of the transistor 42 via a resistor 83. The positive input 84 of the amplifier 80 is connected to ground 46 via a resistor and to the positive connection 48 via a resistor 88.

Example values in Fig. 3 (k = kQ)

Hall generators 22, 24, 26 ...HW101A Transistors 42 ...BC847B Resistance 40 ...200 Ω Resistance 44 ...120Ω Resistance 83 ...22k Resistance 86 ...1k Resistance 88 ...7.5k How Fig.3
· · · · ·
· · · • · · * · · · ··· · ·· · · ·

t · ♦ »

The positive input 84 receives a voltage setpoint, e.g. 0.6 V, via the voltage divider made up of resistors 88, 86. If the voltage drop across the measuring resistor 44 exceeds this setpoint of 0.6 V, the amplifier 80 generates a reduced base current for the transistor 42 so that it becomes less conductive until the voltage drops across the resistor 86 and the measuring resistor 44 are practically identical.

As a result, as shown in Fig. 2, once the temperature Ton is reached, the current i through the Hall generators 22, 24, 26 is limited to a predetermined value, e.g. to 5 mA. The mode of operation is therefore similar to that of Fig. 1, but the use of an operational amplifier 80 means that the control accuracy is significantly higher. However, it has been shown that excellent results can also be achieved with the circuit according to Fig. 1.

Fig. 4 shows a variant where the amplitude of the Hall signals Uh can be changed by means of a control signal ust which is fed to an input 90.

The arrangement according to Fig. 4 is constructed similarly to that according to Fig. 3, and therefore the same reference numerals are used for identical or equivalent parts.

The Hall generators 22 ... 26 are part of an actual value acquisition 89, which is used, for example, to acquire the actual speed of a motor 91. This can be done as shown and described in Fig. 1. For this purpose, the motor 91 has a permanent magnet rotor (not shown) which activates the Hall generators 22 ... 26 alternately with a north pole and a south pole via its magnetic field 93, so that their output signals um and uh2 change depending on the speed.

An operational amplifier is connected to the signal outputs 60, 62 of the Hall generator 22, which therefore supplies an analog output signal at its output 92, the magnitude of which is proportional to the Hall voltage um between the inputs of the operational amplifier 90. An operational amplifier 94 is also connected to the signal outputs of the Hall generator 26, the output 96 of which supplies an analog output signal that is proportional to the Hall voltage uh2 at its input. The operational amplifiers 90 ... 94 are part of a signal conditioning 95.

The current i through the Hall generators 22 ... 26 is determined by a controller. A setpoint value SW is fed to this controller via an input 104, e.g. a desired speed of 9,300 rpm. An actual value IW from the actual value acquisition 89 is fed to it via an input 106, e.g. an actual speed of 9,250 rpm.

From this, the controller 97 calculates an increased control value ust, which leads to a corresponding increase in the current I in the actuator, in that this control value ust is fed from an input 90 via a resistor 98 to the positive input of the operational amplifier 80. As in Fig. 3, this ensures that the current i is set so high that the voltage drop across the measuring resistor 44 essentially corresponds to the control value ust. This causes the signals at the outputs 92 ... 96 to rise, and the speed of the motor 91 is increased accordingly until the desired setpoint SW is reached. - The motor 91 therefore represents the so-called controlled system here.

The analog voltages at outputs 92 and 96 are a function

a) the magnetic flux density acting on the Hall generators 22 ... 26, and

b) the size of the control value ust·

The arrangement according to Fig. 4 can be used, for example, for a simple speed controller in which the level of the stator currents of an ECM 91 depends on the amplitude of the signals at the analog outputs 92, 96.

From the voltages um and uh2, as shown and described in Fig. 1, additional digital signals can be derived, which can be used to measure the rotor position, to calculate the speed, to measure the time for one rotor revolution, etc. and are fed to the controller 97 as actual value IW.

The number of Hall sensors 22 ... 26 depends on the respective application. For example, only one sensor is required for a single-phase motor, whereas at least two and usually three Hall sensors are required for a three-phase motor. Additional Hall sensors 100 and operational amplifiers 102 are shown schematically in Fig. 4.

Naturally, numerous variations and modifications are possible within the scope of the present invention.

Claims (20)

1. Electronically commutated motor, which has at least one analog Hall generator ( 22 , 24 , 26 ) with two power connections ( 28 , 30 ) and two signal outputs ( 60 , 62 ) for detecting its rotor position, wherein the power connections ( 28 , 30 ) of the analog Hall generator are connected in series with a semiconductor actuator ( 42 ) and a measuring resistor ( 44 ) to a direct voltage source ( 48 ), and a controller ( 50 , 52 , 54 , 58 ; 80 , 86 , 88 ) is provided, which, by influencing the semiconductor actuator ( 42 ), limits the voltage drop at the measuring resistor ( 44 ) to a predetermined value (uM) when a predetermined temperature (TON) is exceeded, which is dimensioned such that the Hall generator ( 22 , 24 , 26 ) enables reliable detection of the rotor position even at the maximum permissible temperature of the motor, whereby the specified temperature (TON) is greater than the minimum permissible temperature of the motor and less than its maximum permissible temperature. 2. Motor according to claim 1, in which a plurality of analog Hall generators ( 22 , 24 , 26 ) are provided, the current connections ( 28 , 30 , 32 , 34 , 36 , 38 ) of which are connected in series with one another, with the semiconductor actuator ( 42 ) and with the measuring resistor ( 44 ). 3. Motor according to claim 1 or 2, in which the voltage drop across the measuring resistor ( 44 ) is fed to a transistor ( 52 ) whose internal resistance decreases with increasing magnitude of this voltage drop and the voltage drop across this transistor ( 52 ) is in turn fed to the semiconductor switching element ( 42 ) in order to limit the voltage drop across the measuring resistor ( 44 ) to a predetermined value (uM) once the predetermined temperature (TON) is exceeded. 4. Motor according to one of the preceding claims, in which the Hall voltage (uH) occurring between the signal outputs ( 60 , 62 ) of a Hall generator ( 22 , 24 , 26 ) can be fed to a comparator ( 64 , 74 , 76 ) in order to convert this voltage into a binary signal. 5. The motor of claim 4, wherein the comparator ( 64 ) has positive feedback ( 72 ). 6. Motor according to one of the preceding claims, in which an operational amplifier ( 80 ) is provided for controlling the semiconductor actuator ( 42 ), to one output ( 84 ) of which a potential can be supplied which corresponds to a desired setpoint value and in which the potential at the other input ( 79 ) is a function of the voltage drop (uM) across the measuring resistor ( 44 ). 7. Motor according to claim 6, in which a potential dependent on the voltage drop (uM) across the measuring resistor ( 44 ) can be fed as an actual value to the other input ( 79 ) of the operational amplifier ( 80 ). 8. Motor according to one of the preceding claims, in which the series connection of the at least one Hall generator ( 22 , 24 , 26 ), the semiconductor actuator ( 42 ) and the measuring resistor ( 44 ) can be supplied with an operating voltage which is approximately n × (1.4...2.2 V), where n is the number of Hall generators ( 22 , 24 , 26 ) connected in series. 9. Motor according to one of the preceding claims, in which, when a plurality of Hall generators are connected in series, Hall generators belonging to the same batch are used. 10. Electronically commutated motor, which has at least one analog Hall generator ( 22 , 24 , 26 ) with two current connections ( 28 , 30 ) and two signal outputs ( 60 , 62 ) for detecting its rotor position, wherein the current connections ( 28 , 30 ) of the analog Hall generator are connected in series with a first transistor ( 42 ) serving as an actuator and a measuring resistor ( 44 ) to a direct voltage source ( 48 ), further comprising a second transistor ( 52 ), to the input of which a value dependent on the voltage drop (uM) at the measuring resistor ( 44 ) is supplied in such a way that the internal resistance of the second transistor ( 52 ) decreases with increasing magnitude of this voltage drop, wherein a signal dependent on the voltage drop at the second transistor ( 52 ) is in turn supplied to the first transistor ( 42 ) in order to (ToN), which lies within the operating temperature range of the engine, to limit the voltage drop (uM) across the measuring resistor ( 44 ) to a predetermined value and thereby reduce the power consumption of the at least one Hall generator ( 22 , 24 , 26 ) in the range of higher engine temperatures. 11. A motor according to claim 10, wherein the second transistor ( 52 ) is connected in series with a resistor ( 50 ) to a substantially constant voltage. 12. Motor according to claim 10 or 11, in which a plurality of analog Hall generators ( 22 , 24 , 26 ) are provided, the current connections ( 28 , 30 , 32 , 34 , 36 , 38 ) of which are connected in series with one another, with the first transistor ( 42 ) and with the measuring resistor ( 44 ). 13. Motor according to one of claims 10 to 12, in which the Hall voltage (uH) occurring between the signal outputs ( 60 , 62 ) of a Hall generator ( 22 , 24 , 26 ) can be fed to a comparator ( 64 , 74 , 76 ) in order to convert this voltage into a binary signal. 14. The motor of claim 13, wherein the comparator ( 64 ) has positive feedback ( 72 ). 15. Motor according to one of claims 10 to 14, in which the series connection of the at least one Hall generator ( 22 , 24 , 26 ), the first transistor ( 42 ) and the measuring resistor ( 44 ) can be supplied with an operating voltage which is approximately n × (1.4...2.2 V), where n is the number of Hall generators ( 22 , 24 , 26 ) connected in series. 16. Motor according to one of claims 10 to 15, in which, when a plurality of Hall generators are connected in series, those Hall generators ( 22 , 24 , 26 ) are used which belong to the same batch. 17. Electronically commutated motor, which has a plurality of analog Hall generators ( 22 , 24 , 26 ) for detecting its rotor position, the power connections ( 28 , 30 , 32 , 34 , 36 , 38 ) of which are connected in series with one another, with a semiconductor actuator ( 42 ) and with a measuring resistor ( 44 ), the series connection being designed for connection to a direct voltage source, which Hall generators ( 22 , 24 , 26 ) have signal outputs ( 60 , 62 ), to each of which a comparator ( 64 , 74 , 76 ) having a positive feedback ( 72 ) is connected in order to convert the Hall voltage (uH) occurring at the associated Hall generator ( 22 , 24 , 26 ) into a binary signal, wherein a controller ( 50 , 52 , 54 , 58 ; 80 , 86 , 88 ) is provided which, by influencing the semiconductor actuator ( 52 ), limits the voltage drop across the measuring resistor ( 44 ) to a predetermined value (UM) when a predetermined temperature (TON) of the Hall generators is exceeded, which is dimensioned such that the Hall generators ( 22 , 24 , 26 ) enable detection of the rotor position even at the permissible maximum temperature, wherein the predetermined temperature (TON) is greater than the permissible minimum temperature and less than the permissible maximum temperature. 18. Motor according to claim 17, in which the voltage drop across the measuring resistor ( 44 ) is fed to a transistor ( 52 ) whose internal resistance decreases with increasing magnitude of this voltage drop, and the voltage drop across this transistor ( 52 ) is in turn fed to the semiconductor actuator ( 42 ) in order to limit the voltage drop across the measuring resistor ( 44 ) to a predetermined value (UM) once the predetermined temperature (TON) is exceeded. 19. Motor according to claim 17 or 18, in which the series connection of the Hall generators ( 22 , 24 , 26 ), the semiconductor actuator ( 42 ) and the measuring resistor ( 44 ) can be supplied with a direct voltage which is approximately
n × (1.4...2.2 V), where n is the number of Hall generators ( 22 , 24 , 26 ) connected in series. 20. Motor according to one of claims 17 to 19, in which when a plurality of Hall generators are connected in series, Hall generators are used which belong to the same batch.