JPH01186192A - Drive for brushless motor - Google Patents

Abstract

PURPOSE:To eliminate the need for a filter circuit, and to prevent the influences of noises, etc., included in a driving-coil conduction waveform by controlling the frequency and phase of a conduction changeover signal in response to the phase difference between the phase back electromotive voltage generated in a motor driving coil and that of the conduction changeover signal. CONSTITUTION:An output from a voltage control oscillator 40 is transmitted to driving coils 1-3 through a frequency dividing circuit 41, a conduction changeover circuit 44 and drive transistors 10-15. When phase angle shift is generated between driving-coil back electromotive voltage and a driving-coil conduction waveform, the phase error is detected by a phase error detector 20 and amplified by an error amplifier 30, and the oscillation frequency and phase of the voltage control oscillator 40 are controlled so that the phase error is brought to zero.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a brushless motor drive device without a position detector for detecting the position of a movable element of a motor.

BACKGROUND OF THE INVENTION In recent years, brushless motors have been increasingly used for various drive motors in order to have longer lifespans, higher reliability, and thinner shapes.

Brushless motors generally require a position detector to detect the position of the movable element, and in order to achieve further cost reduction and miniaturization, so-called commutation sensorless brushless motors that do not have a position detector are required. It has become. A conventional example of such a drive device for a brushless motor is disclosed in Japanese Patent Application Laid-open No. 52-80415, for example.

An example of the above-mentioned conventional brushless motor drive device will be described below with reference to the drawings.

FIG. 8 is a circuit diagram of a conventional brushless motor drive device. In FIG. 8, one end of the drive coils 1 to 3 is common, and the other end of the drive coil 1 is connected to the anode of the diode 4, the cathode of the diode 5, and the drive transistor 10.
The other end of the drive coil 2 is connected to the anode of the diode 6, the cathode of the diode 7, and the collectors of the drive transistors 11 and 14, and the other end of the drive coil 3 is connected to the anode of the diode 8. It is connected to the cathode of diode 9 and the collectors of drive transistors 12 and 15. the cathode of the diode 4.6.8 and the drive transistor 10;
, 11.12 are connected to the positive feed line, and the anode of the diode 5.7.9 and the emitter of the drive transistor 13.14.15 are grounded.

The other ends of the drive coils 1 to 3 are each connected to a filter circuit 1.
6, and the output of the filter circuit 16 is input to the energization switching circuit 17. The output of the energization switching circuit 17 is input to the bases of the drive transistors 10 to 15, respectively.

The operation of the conventional brushless motor drive device configured as described above will be described below.

FIG. 9 is an explanatory diagram of the operation in FIG. 8, and Uo.

Vo and Wo are energization waveforms of the drive coils 1, 2.3. The energization waveforms Uo, Vo, and Wo have their harmonic components removed by the filter circuit 16 and have a phase of 90°.
Delay, Fl, F2. Each is converted to Fl. In addition,
The filter circuit 16 is a first-order filter, and is composed of, for example, an RC passive filter, a negative-order mirror integration circuit, etc., and its cutoff wave number is set to be sufficiently lower than the frequency of the drive coil energization waveform. The outputs Fi, Fa, Fs of the filter circuit 16 are controlled by the energization switching circuit 17,
Logically processed into UH, UL, VH, VL, Wo, Wt,
The driving transistors 10 to 15 are operated in a switching manner. At this time, the switching operation is performed so that motor drive torque is always generated in one direction, and the motor is driven.

Problems to be Solved by the Invention However, in the above configuration, a filter circuit having low cutoff wavenumber characteristics is required for each phase of the drive coil, and therefore a large number of large capacitance capacitors are required.

Furthermore, when the inductance of the drive coil is large, the current flowing through the drive coil is delayed in time after the drive transistor is turned on, and the permanent magnetic field is further demagnetized by the magnetic field generated by the drive coil itself. There is a so-called armature reaction.

In such a case, it is known that if the drive coil is energized at the timing shown in FIG. 9, the efficiency will decrease. As an improvement measure, a method was proposed in JP-A-52-8 in which the phases of the Fl, Ft, and Fl signals are slightly advanced and the drive transistor is operated to compensate for the delay in energization due to armature reaction.
Although this is described in Japanese Patent No. 0145, additional parts such as capacitors are required to realize this. Also,
The drive coil energization waveforms Uo, Vo, and Wo include spike noise that occurs when the drive transistor is turned off, current fluctuations due to power supply voltage fluctuations, load fluctuations, etc.
*It is often difficult to accurately obtain an energization switching signal from the VOg WO energization waveform using a filter circuit. As a countermeasure to this problem, a method as shown in Japanese Patent Publication No. 59-36519 has been proposed.

However, the method of obtaining the energization switching signal from the drive coil energization waveform using a filter circuit basically has the following problems. In other words, the voltage drop caused by the energizing current and internal impedance of the drive coil when the drive coil is energized, and the spike noise that occurs immediately after the current-carrying body is stopped are superimposed on the fundamental wave (back electromotive force) of the drive coil energization waveform. constantly fluctuates with fluctuations in power supply voltage and load. Therefore, when filtering the drive coil energization waveform to obtain the energization switching signal, errors occur due to the above components that are constantly fluctuating and superimposed on the fundamental wave (back electromotive force) of the energization waveform, resulting in accurate drive coil energization. becomes difficult.

To solve these problems, various methods have been proposed to accurately obtain the energization switching signal, but basically the phase difference between the back electromotive force generated in the drive coil and the energization switching signal is kept constant. Therefore, the adjustment is performed around the filter circuit, and the adjustment is extremely troublesome. In addition, a large number of capacitors are required in addition to those used to configure the filter circuit.
Therefore, when using IC, the number of external parts and the number of bottles increase, resulting in an expensive product. In addition, a method for obtaining the energization switching signal digitally using a microcomputer, etc. without using a filter circuit was published in Japanese Patent Application Laid-Open No. 61-29319.
Although it is described in Publication No. 1, it is still expensive.

As mentioned above, the conventional brushless motor drive device is
From the drive coil energization waveform, a filter circuit obtains an energization switching signal that has a certain phase relationship with the position of the mover, and this is used to sequentially energize the drive coils, so the drive coil energization waveform It is difficult to obtain a true energization switching signal due to spike noise included in the energization, a voltage drop in the drive coil due to the energizing current, fluctuations in these superimposed components due to fluctuations in the power supply voltage and load, and influences such as armature reaction. Further, a large number of large capacitance capacitors are required when constructing a filter circuit, and especially when integrated into an IC, the number of external parts and the number of bins increases, which is disadvantageous in terms of cost.

Therefore, as shown in Japanese Patent Publication No. 61-3193, the waveform of the back electromotive force generated in the drive coil is shaped, and P
A method has been proposed in which a proper phase pulse is generated using an LL circuit, and the drive coils are sequentially energized to drive the motor. That is, with the configuration shown in Figure 1O, the back electromotive voltages A, B, and C generated in the drive coils are pulse-shaped and arithmetic processed to obtain a pulse signal G, Comparing the phases of the frequency generator output I and the pulse signal G, and feeding the comparison output to the voltage controlled oscillator to synchronize the phases of the signals I and G;
A method is shown in which the frequency of the signal I is divided to generate an energization signal for a drive coil to drive a motor. FIG. 11 shows the signals of each part of this system. However, in this type of system, the back electromotive force generated in the drive coil includes the voltage drop caused by the current flowing when the drive coil is energized and the internal impedance of the drive coil, as well as the voltage drop that occurs immediately after the current-carrying body stops. Since spike noise and the like are superimposed, it is extremely difficult to obtain a pulse signal by waveform shaping and arithmetic processing of the back electromotive force generated in the drive coil. actual,
In the configuration shown in FIG. 10, it is not possible to obtain the pulse signal G as shown in FIG. 11, and the influence of spike noise that occurs immediately after energization of the drive coil always occurs. Therefore, a phase comparison with the frequency divider output ■ becomes impossible, and phase synchronization of both signals I and G becomes impossible. Therefore, the Tokuko Sho 61
In the method disclosed in Japanese Patent No. 3193, the back electromotive force of the drive coil is simply pulse-shaped and processed, so the above-mentioned problems occur and it is impossible to implement the system.

As described above, conventional brushless motor drive devices have had various problems.

In view of the above-mentioned problems, the present invention eliminates the large number of large-capacity capacitors that were required in the conventional filter circuit configuration by obtaining a drive coil energization switching signal without using a filter circuit, and at the same time changes the drive coil energization waveform. The present invention provides a novel brushless motor drive device that can sequentially energize and drive drive coils without being affected by included spike noise, power supply voltage fluctuations, load fluctuations, or armature reactions.

Means for Solving the Problems In order to solve the above problems, a brushless motor drive device of the present invention includes a multi-phase motor drive coil, a plurality of drive transistors provided in the drive coil, a voltage controlled oscillator, an energization switching circuit that forms an energization switching signal for the drive coil based on a frequency signal corresponding to an oscillation frequency of the voltage controlled oscillator; and a energization switching circuit that has a constant phase relationship with the energization switching signal during a period when the drive coil is not energized. a comparator that generates a phase error detection pulse and compares a back electromotive voltage generated in the drive coil and a neutral point voltage of the drive coil during the phase error detection pulse generation period;
a phase error detector that equivalently detects the phase difference between the back electromotive voltage and the energization switching signal at the output of the comparator; and an error amplifier that amplifies the output of the phase error detector; The output is input to the voltage controlled oscillator.

Operation The present invention uses the above-described configuration to detect the phase difference between the back electromotive force generated in the motor drive coil and the energization switching signal of the same coil, and to control the frequency and phase of the energization switching signal according to the detected phase difference. Since a feedback loop or phase control loop (PLL loop) is configured so that the energization switching signal maintains a constant phase relationship with respect to the position of the movable element, the filter circuit that was previously required is no longer required. All of the various problems that occurred due to this will be resolved.

In addition, since the phase difference between the back electromotive force generated in the motor drive coil and the energization switching signal of the same coil is detected during the energized period, accurate phase difference detection is possible and stable operation of the phase control loop is ensured. It becomes possible.

Embodiment Hereinafter, a brushless motor drive device according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram of a brushless motor drive device according to an embodiment of the present invention. In FIG. 1, parts having the same functions as those of the conventional brushless motor drive device shown in FIG. 8 are given the same symbols, and their explanations will be omitted. In FIG. 1, the bases of drive transistors 10 to 15 are respectively connected to the outputs of power amplifiers 43, and the inputs of power amplifiers 43 are connected to the outputs of logic circuits . Here, the logic circuit 42 and the power amplifier 43 constitute an energization switching circuit 44. The input of the logic circuit 42 is connected to the output Dl of the frequency dividing circuit 41.
The input of 1 is connected to the output of voltage controlled oscillator 40. Further, a minimum frequency setting circuit 50 is connected to the voltage controlled oscillator 40. Output DI of the frequency dividing circuit 41
gD2+D3 and the output Ut+U2 of the logic circuit 42
+ VIJV, , W, , W are input to the phase difference detection pulse generation circuit 28, and one end Uo of the drive coils 1, 2.3
+Vo, Wo l;! H7y [fn ro 21, 2
2, 231. : Has been input. The buffer circuit 2
1.22.23 each output UB, VB, WB is comparator 27
This common connection point NB is input to the comparator 27. The output PD of the comparator 27 is controlled by the output of the phase difference detection pulse generation circuit 28. Here, each of the components 21 to 28 constitutes a phase error detector 20, and the output PD is the output of the phase error detector 2o. The output PD of the phase error detector 20 is connected to the resistor 3
2 to the inverting input terminal of the operational amplifier 31;
A series circuit of a resistor 33 and a capacitor 34 and a capacitor 3 are connected between the inverting input terminal and the output terminal of the operational amplifier 31.
5 has been inserted. A constant bias voltage is applied to the non-inverting input terminal of the operational amplifier 31 through resistors 36 and 37. Here, each of the components 31 to 37 constitutes an error amplifier 3o, and the output EA of the error amplifier 30 is
O is connected to the input of the voltage controlled oscillator 40.

The operation of the brushless motor drive device configured as described above will be described below.

FIG. 2 is a detailed explanatory diagram of the present invention, showing the phase relationship between the drive coil back electromotive force and the drive coil energization waveform. FIG. 2(a) shows a case where the phase relationship between the back electromotive force (broken line part) and the energization waveform (solid line part) is in an optimal state,
Figures (b) and (c) show the case where the phase angle ψ deviates from the optimum state. Here, in FIG. 1, the output of the voltage controlled oscillator 40 is transmitted to the frequency dividing circuit 419
．． Drive coils 1 to 1 through drive transistors 10 to 15
3 has been transmitted. Therefore, a certain phase relationship exists between the output of the voltage controlled oscillator 40 and the energization waveforms of the drive coils 1 to 3. That is, by controlling the oscillation frequency and phase of the voltage controlled oscillator 40, it is possible to control the phase difference between the drive coil back electromotive voltage and the drive coil energization waveform. Therefore, as shown in Fig. 2 (b) and (c), if a phase angle ψ deviation occurs between the drive coil back electromotive force and the drive coil energization waveform, the phase error ψ is detected by phase error detection. By providing a phase control loop that detects and amplifies the voltage controlled oscillator 40 using the oscillator 20 and the error amplifier 30 and controls the oscillation frequency and phase of the voltage controlled oscillator 40 so that ψ becomes zero, the optimum energization state as shown in FIG. 2(a) is achieved. It becomes possible to secure the following. Therefore, it is possible to always generate motor drive torque stably and efficiently, and the motor is driven.

Here, a specific example of the configuration of the phase error detector 20 will be described in detail.

First, a concrete configuration of the phase difference detection pulse generation circuit 28 in the phase error detector 20 may be as shown in FIG. 3, for example.

In FIG. 3, parts having the same functions as those in FIG. 1 are given the same symbols. Output Ul +U2 of the logic circuit 42. v
1. v2. W1. W2 and the output Di of the frequency dividing circuit 41
, D2. D3 is applied as an input signal to this phase difference detection pulse generation circuit. FIG. 4 is an explanatory diagram of the operation of the phase difference detection pulse generation circuit shown in FIG. 3, and each waveform in FIG. 4 corresponds to the signal at each symbol point in FIG. 3. There is. Output terminal S of the phase difference detection pulse generation circuit. Signal waveforms with the same symbols in FIG. 4 are output from +S1 +St+Sa+S4+Ss+Ss.

Next, as a concrete configuration of the phase error detector 20 including the phase difference detection pulse generation circuit 28, for example, the one shown in FIG. 5 can be considered.

In FIG. 5, parts having the same functions as those in FIG. 1 are given the same symbols. In other words, one end U of the drive coils 1, 2゜3
o, Vo, and Wo are buffer circuits 21 and 22, respectively.
．． 23 and the buffer circuit 21.22.23
(7) Output UBI Va, Ws each have a resistance of 24.2
5.26, and the common connection point NB is connected to the inverting input terminals of the comparison circuits 100, 120.degree. 140 and the non-inverting input terminals of the comparison circuits 110, 130.degree. 150. The output UB of the buffer circuit 21 is connected to the non-inverting input terminal of the comparison circuit 100 and the inverting input terminal of the comparison circuit 110, and the output UB of the buffer circuit 22
B is connected to the non-inverting input terminal of the comparator circuit 120 and the inverting input terminal of the comparator circuit 1300, and the output WB of the buffer circuit 23 is connected to the non-inverting input terminal of the comparator circuit 140 and the inverting input terminal of the comparator circuit 150. It is connected. The comparison circuit 100, 110, 120, 130, 14
0.150 each output transistor 101, 111, 12
1°131.141.151, and the transistors 101, 111°121.
The collectors of transistors 131, 141, and 151 are commonly connected to the collector of transistor 161, and form a phase error detector output PD. The base of the transistor 161 is connected to the base and collector of a transistor 162, the collector of a transistor 164, and the collector of a transistor 169 that operates as a constant current source. The emitter of the transistor 162 is a resistor 163
A stabilized power supply voltage Vreg is applied through the transistors 161 and 164, and the stabilized power supply voltage Vreg is applied to the emitters of the transistors 161 and 164. the transistor 164
The base of is connected to the emitter of the transistor 167 via a resistor 166, and the collector of a transistor 167 whose emitter is grounded is connected via a resistor 165. The base of the transistor 167 is connected to the output So of the phase difference detection pulse generation circuit 28 via a diode 168.

Another output S1 of the phase difference detection pulse generation circuit 28. S
2, S3, S4. Ss and Ss each have a resistance of 17
1,173,175,177.179° Transistor 170.172,17 whose emitter is grounded through 181
4,176.178, 180, and the transistors 170°172.174, 176.17
8. Each collector of 180 is connected to the transistor 1, respectively.
It is connected to each base of 01°111, 121, 131, 141, and 151. Each input terminal of the phase difference detection pulse generation circuit 28 is connected to each output Ur of the energization switching circuit 44,
U2, Vl, Va, Wt, W2 and the outputs DI, D-, and D3 of the CF frequency dividing circuit 41 are connected.

The operation of the phase error comparator configured as above will be described below.

FIG. 6 is an explanatory diagram of the operation, and shows how the phase error between the back electromotive voltage and the energization waveform is detected with respect to the drive coil 1. In FIG. 6, the drive coil 1 receives signals Ul, U2 . (that is, UH, UL) are energized as energization command signals. Therefore, a period in which neither Ul nor U2 is output is a period in which the current-carrying body is stopped, and during this period, the drive coil energization waveform Uo coincides with the back electromotive voltage U. From Figure 6, during the period when the current-carrying body is stopped, U2 becomes H after Ul becomes Low.
The period until it becomes high corresponds to 1 clock or 4 clocks of DI. Similarly, there is a current-carrying-off period during the period from when U2 becomes Low until when Ul becomes High, but to simplify the explanation, only the former period will be considered.

During the current-carrying period, the neutral point voltage of each drive coil is No.
Comparing the drive coil energization waveform Uo with the drive coil energization waveform Uo, when the phase difference ψ between Uo and the drive coil back electromotive force U is zero, No and Uo are at the center during the energization period, that is, after Ul becomes Low and then 2 of D3. Match after clock. Also, if Uo lags behind U by the phase difference ψ, then No and Uo will be different from each other when Ul is Low.
Then, two clocks after D3, they match, and Uo becomes U.

When the phase difference ψ is advanced from , NO and Uo coincide after Ul becomes Low, and two clocks later. Therefore, two clocks after Ul goes low, Uo and N. By comparing Uo and Ue
You can know the phase relationship of Therefore, as a method for detecting the phase difference ψ, phase error detection pulse signals S2 and So having an appropriate width are generated based on two clocks of D3 after Ul becomes Low, and No. By comparing Uo with Uo, a comparator output PD having a duty corresponding to the phase difference ψ can be obtained. In FIG. 6, S2 and S.

occurs two clocks after D3 after Ul goes low, and occurs for a period of -clocks.

The figure shows a case where Ue lags behind Ue by a phase angle ψ.

As described above, for the energization waveform Uo of the drive coil 1, Ul is L
The operating principle was explained in 2, where the phase difference ψ is detected using the current-carrying body off period from when Uo becomes OW until U2 becomes High. The period from when Ul becomes Low to when Ul becomes High, and the energization waveforms V of the other drive coils 2 and 3.

, Wo can be similarly detected, and in this embodiment, by combining all of them, the phase error detector output P
I got a D.

Further, the buffer circuits 21, 22, and 23 are inverting amplifiers with a gain of 1/2, and each comparison circuit is 100°, 110, 120°
, 130, 140, and 150 as the respective outputs UB, VB, and WB of the buffer circuits 21, 22, and 23.
is designed to satisfy.

FIG. 7 shows the operating waveforms of each part when the configuration shown in FIG. 5 is used as the phase error detector 20 in FIG. This shows how the oscillation frequency f of the voltage controlled oscillator is controlled so that Note that the lowest frequency setting circuit 50 in FIG. 1 sets the oscillation frequency of the voltage controlled oscillator 40 to the lowest frequency when starting the motor, and
This is to reliably start the motor by generating a rotating magnetic field at a speed that the rotor (rotor) can sufficiently follow.

As described above, according to this embodiment, the motor drive coil is always energized based on the output of the voltage controlled oscillator, and the phase difference between the energization waveform and the back electromotive force of the drive coil is detected by the phase error detector. By providing a so-called phase control loop (PLL loop) that controls the oscillation frequency and phase of the voltage-controlled oscillator so that the phase error becomes zero using the amplified signal, the motor can be driven efficiently without the influence of armature reaction. Furthermore, the conventional filter circuit is not required, and the number of large-capacity capacitors can be significantly reduced. In addition, the phase error detector generates a phase error detection pulse during the period when the drive coil is not energized, and compares the back electromotive force generated in the drive coil with the neutral point voltage during the detection pulse generation period to equivalently calculate the reverse voltage. Since the phase error output of the electromotive voltage and the energization switching signal is obtained, by setting the detection pulse generation timing to avoid the spike noise generation period that occurs immediately after the drive coil energization stops, it is possible to avoid the influence of the spike noise. can be eliminated. Furthermore, since the phase error is detected during the period when the current-carrying body is not in use, it is not affected by the voltage drop or its fluctuation caused by the current-carrying current and the impedance of the drive coil that occur during the current-carrying period. Furthermore, the width of the phase error detection pulse generated during the current-carrying period is constant with respect to the electrical angle or mechanical angle of the motor, and the comparison output between the back electromotive force and the neutral point voltage during the phase error detection pulse generation period is Since it depends only on the duty of , the phase error detection gain does not change due to the influence of the motor rotation speed, and the phase control loop can always operate stably.

Effects of the Invention As described above, the present invention includes a multi-phase motor drive coil,
a plurality of drive transistors connected to the drive coil; a voltage-controlled oscillator; an energization switching circuit that forms an energization switching signal for the drive coil based on a frequency signal corresponding to an oscillation frequency of the voltage-controlled oscillator; During the period when the coil is not energized, a phase error detection pulse having a constant phase relationship with the energization switching signal is generated, and a back electromotive force generated in the drive coil and the inside of the drive coil are generated during the phase error detection pulse generation period. a phase error detector having a comparator for comparing sex point voltages, and equivalently detecting a phase difference between the back electromotive voltage and the energization switching signal using the comparison output;
By biasing the error amplifier that amplifies the output of the phase error detector and inputting the output of the error amplifier to the voltage controlled oscillator, there is no need for a conventionally required filter circuit. It can significantly reduce the number of capacitors, and also eliminates spike noise included in the drive coil energization waveform, voltage drop due to the energization current and drive coil impedance, fluctuations due to power supply voltage and load fluctuations, and reduced efficiency due to armature reaction. An extremely superior brushless motor drive device without any problems can be realized.

Although the embodiments of the present invention have been described using a three-phase full-wave drive system, other drive systems such as a two-phase full-wave drive system, a two-phase half-wave drive system, a three-phase half-wave drive system, etc. It is also possible to realize a brushless motor drive device using the same method as the present invention.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram of a brushless motor drive device according to an embodiment of the present invention, FIG. 2 is an explanatory diagram of the operating principle of FIG. 1, and FIG. 3 is a specific circuit configuration diagram of a phase difference detection pulse generation circuit. 4 is an explanatory diagram of the operation of FIG. 3, FIG. 5 is a specific circuit configuration diagram of the phase error detector, FIG. 6 is an explanatory diagram of the operation of FIG. 5, and FIG. 7 is an operation diagram of the embodiment of the present invention. A waveform diagram, FIG. 8 is a circuit configuration diagram of a conventional brushless motor drive device, FIG. 9 is an operation explanatory diagram of FIG. 8, and FIG. 10 is a circuit configuration diagram of another conventional brushless motor drive device. FIG. 11 is an explanatory diagram of the operation of FIG. 10. 1-3... Drive coil, 10-15...
- Drive transistor, 20... phase error detector, 30... error amplifier, 40... voltage controlled oscillator, 44... energization switching agent Name: Patent attorney Toshio Nakao and 1 other person Figure 6
q Figure 7＼ Figure ≧ 0 mouth group Figure 9 W

Claims (1)

[Claims] A multi-phase motor drive coil, a plurality of drive transistors connected to the drive coil, a voltage controlled oscillator, and a energization switching signal for the drive coil based on a frequency signal corresponding to the oscillation frequency of the voltage controlled oscillator. an energization switching circuit that generates a phase error detection pulse having a constant phase relationship with the energization switching signal during a period when the drive coil is not energized; a phase difference error detector that includes a comparator that compares the electromotive force and the neutral point voltage of the drive coil, and that equivalently detects the phase difference between the back electromotive force and the energization switching signal using the output of the comparator; and an error amplifier for amplifying the output of the phase difference error detector, and the output of the error amplifier is input to the voltage controlled oscillator.