CN1177803A

CN1177803A - Coil-load driving circuit

Info

Publication number: CN1177803A
Application number: CN 97116491
Authority: CN
Inventors: 古贺彻
Original assignee: Rohm Co Ltd
Current assignee: Rohm Co Ltd
Priority date: 1996-09-24
Filing date: 1997-09-24
Publication date: 1998-04-01

Abstract

An inductive load drive circuit includes a transistor for pulling-in an excitation current having a predetermined polarity and generated by an inductive load. The transistor is turned-on by a first idling loop when a drive voltage of the inductive load has a negative polarity, and the transistor is turned-on by a second idling loop when the drive voltage has a positive polarity. Though both of the first idling loop and the second idling operate on the basis of the drive voltage, in pulling the excitation current into the circuit, the drive voltage reaches a lower limit of a dynamic range at a time that the first idling loop is suitably operated while the drive voltage reaches an upper limit of the dynamic range at a time that the second idling loop is suitably operated.

Description

Coil-load driving circuit

The present invention relates to the coil-load driving circuit that CD, CD-ROM and MD disk systems such as (minidisks) is used, relate in particular to the energising control technology that (signal) picks up the coil load of motor, disk turning motor, spindle drive motor, load motor etc.

Be used for the drive controlling that light (signal) picks up the coil load of servomotor etc. in this kind disk system, shown in Fig. 3 (mode chart), use current converter circuit.For example, when (signal) when picking up servocontrol, the electric current that flows through loading coil L is converted to forward and reverse electric current I A or IB along with the input voltage (Vi) based on the control signal of focus direction or signal record orbital direction.In order to eliminate the back electromotive force that coil produces, increase unnecessary torque, suppress motor rotation etc., need the direction of conversion electrical current.Amplifier 60 among Fig. 3, provide reference voltage V R to in-phase end, and, be formed in the negative-feedback amplifier that is connected feedback resistance Rf between end of oppisite phase and the output terminal, provide input voltage Vi by input resistance Ri to end of oppisite phase, coil L corresponding with it supplied with forward and reverse electric current I A or IB.Figure 4 shows that the final output-stage circuit of the formation amplifier 60 that in the past used.In this final output stage,, be provided with the output stage transistor Tr1 and the Tr2 of NPN type for coil L being provided output Vout.Connect power supply potential V by collector _CCThe contact 61 that is connected with the collector of the transistor Tr 2 of grounded emitter of the emitter of transistor Tr 1, corresponding to described output Vout.And this final level according to described input voltage Vi, provides control input VC to its base stage by transistor Tr 3.

The collector of this transistor Tr 3 connects the base stage of transistor Tr 1, makes transistor Tr 1 conducting by transistor Tr 3, and electric current I A flows into coil L.For making sense of current consistent, electric current I A and opposite direction electric current I B are provided with by the open loop idler circuit of tie point 61 through transistor Tr 1, Tr5, Tr4 and diode D1, D2 with the direction of coil L ABSORPTION CURRENT.This open loop idler circuit is for the low dead voltage of lower limit set in the dynamic range of amplifier 60, provides excess current to the base stage of transistor Tr 2.Tie point 61 connects constant current source C2 by two diode D1, D2, in addition, if the forward voltage of diode D1, D2 is identical with described VF, is the base stage of the potential point connection NPN transistor Tr4 on the 2VF through diode D1, D2 by output potential Vout then.And, being provided with PNP transistor Tr 5, this transistorized emitter connects the emitter of transistor Tr 4, and collector connects the base stage of transistor Tr 2, and the base stage of Tr5 connects constant current source C1, and connects the collector of described transistor Tr 3.

Dead voltage lower limit with regard to the dynamic range of the final output stage amplifier 60 of Fig. 4 is verified.At first, make the base stage of transistor Tr 1 and the voltage between the emitter identical with VF, when the base potential of transistor Tr 1 is the voltage level of Vout when above, transistor Tr 1 conducting, electric current I A flows into coil L.As base potential and Vout during with voltage level, transistor Tr 1 is ended, ABSORPTION CURRENT IB inflow transistor Tr2.At this moment for ABSORPTION CURRENT IB steady flow, make of the base potential conducting of the transistor Tr 5 of described idle loop at the Vout voltage level, thereby, provide excess current to the base stage of transistor Tr 2, make transistor Tr 2 be state of saturation.Therefore, by the electric current I B of transistor Tr 2,, between its collector-emitter, flow as saturation current.Yet, be provided with described idle loop exactly,, the detection voltage of tie point 61 risen by diode D1 and D2 in order not influence the dynamic range of amplifier 60, then, partly offset by the 2VF that reduces by two diodes between transistor Tr 4 and Tr5.For this reason, with the lower limit in the dead voltage territory of the dynamic range of amplifier 60, set and remain on the smaller value of the saturation voltage VSAT between the collector-emitter of transistor Tr 2.

Yet, as shown in Figure 5, generally, during the drive coil load, according to the characteristic of its coil, the phase place of output current I produces for example 90 ° hysteresis with respect to output voltage V out, have as using the represented opposed polarity of oblique line among the figure, that is to say that output Vout is subjected to the influence of coil L characteristic, when output voltage and output current produce so phase deviation, in the interval of the opposed polarity of described oblique line, produce the essential ABSORPTION CURRENT IB that flows.But with the amplifier 60 of existing Fig. 4, even output Vout be greatly the time, ABSORPTION CURRENT IB also is possible, and the current potential of the tie point 61 in described idle loop is boundary level (V _CC-when 2VF-VSAT) above, owing to have the upper limit of being failure to actuate, because such phase deviation, current conversion is not smooth, produces and is referred to as negative feedback function oscillatory occurences improper action, similar output voltage itself.

In view of above-mentioned already present problem, the invention provides a kind of stable coil-load driving circuit that carries out the negative feedback action.

For addressing the above problem, the coil-load driving circuit of claim 1 invention has first output stage transistor with the load of unidirectional drive current supply coil, with second output stage transistor of the drive current of other direction being supplied with described coil load, has the mutual base stage of described first and second output stage transistor of common connection, connect each output terminal, and this tie point as the lead-out terminal that is connected with described coil load, simultaneously, with the output of described lead-out terminal feedback-type output amplifier as the feedback input, corresponding with the control input of described feedback-type output amplifier, change the current potential of the common tie point of described base stage, make the described first or second output stage transistor conducting, it is characterized in that, has first shunt circuit, this circuit since the output voltage of described lead-out terminal be closure state below the fixed boundary level, described second output stage transistor of this closure state conducting, with between the common tie point of described base stage and described lead-out terminal along separate routes; And have the 2nd shunt circuit, this circuit is because the output voltage of described lead-out terminal is closure state than the high boundary level of described boundary level the time, described first shunt circuit open state the time, phase deviation along with the output voltage and the output current of described lead-out terminal, change along with described control input, described second output stage transistor of conducting, with between the common tie point of described base stage and described lead-out terminal along separate routes; By described first shunt circuit, described second output stage transistor is become this saturation voltage of state of saturation, be set at the lower limit in the dead voltage territory of described output amplifier.

According to the present invention, when described unidirectional drive electric current being offered described coil load state by described first output stage transistor, because described first shunt circuit, along separate routes may be more than the voltage even described output voltage exceeds, phase deviation along with output voltage and output current, by described second shunt circuit, change the conducting state of described second output stage transistor, the drive current of described other direction can be flowed into described coil load, therefore, by this phase deviation, can not produce bad feedback, and, still keep lower limit to the saturation voltage dead voltage territory of described second output stage transistor.

Below accompanying drawing is done simple declaration.

Fig. 1 is the circuit diagram of expression embodiments of the invention Linear Driving circuit integrated circuit.

Fig. 2 is the simple forming circuit figure of the output stage amplifier in the Linear Driving circuit integrated circuit of presentation graphs 1.

Fig. 3 is the circuit diagram of the feedback-type output amplifier of expression coil driver.

Fig. 4 is the existing feedback-type output amplifier circuit figure of expression.

Fig. 5 is the voltage of amplifier output and the oscillogram of electric current.

Symbol description

1-output stage transistor, 2-output stage transistor, 3-transistor, 4-transistor, 5-transistor, 16-diode, 17-diode, 18-diode.

Below, with reference to accompanying drawing, embodiments of the invention are described.

Fig. 1 illustrates the Linear Driving circuit that the coil load that is used for disk system drives usefulness, and Fig. 2 illustrates the simple forming circuit figure of the output stage amplifier in this driving circuit.

Also have, in the present embodiment, transistorized base stage is VF with the forward voltage of emission voltage across poles and diode.

In Fig. 1, Linear Driving circuit 40 has the

input end

23 and 24 that is connected with servo integrated circuit that does not illustrate among the figure; The

output terminal

41 and 42 that is connected with coil 36 as load.Input end 23 connects the end of oppisite phase of input amplifier 25, connects the in-phase end of polarity comparer 28 simultaneously.Input amplifier 25 is inverting amplifiers, has the feedback resistance 31 that connects and connect inverting input resistance 30 between output terminal and inverting input, provides reference voltage V REF to its in-phase end.The output of input amplifier 25 connects the in-phase end of output amplifier 26, offers the in-phase end of output amplifier 27 simultaneously by phase inverter 29.

Output amplifier 26 is negative-feedback amplifiers, has feedback resistance 33 that connects between output terminal and inverting input and the resistance 32 that connects inverting input, provides reference voltage V REF to its end of oppisite phase.Then, the output of output amplifier 26 connects lead-out terminal 41.Also have, output amplifier 27 also is a negative-feedback amplifier, has feedback resistance 35 that connects between output terminal and inverting input and the resistance 34 that connects inverting input, provides reference voltage V REF to its end of oppisite phase, and its output connects lead-out terminal 42.Here, the output voltage of lead-out terminal 41,42 is respectively V0 ^-, V0 ⁺

Polarity comparer 28 according to by described servo integrated circuit to the input of input end 23 and comparative result from input to the reference voltage of input end 24 that set, will in the following

output amplifier

26 or 27 of conversion and control, first and second the conversion output of idle loop offers output amplifier 26 or 27.That is, for example when the input of input end 23 is low level, the output voltage V 0 of the output amplifier 26 of the in-phase amplifier of the input amplifier 25 by inverting amplifier ^-Output voltage V 0 than the output amplifier 27 that passes through phase inverter 29 ⁺Greatly, at this moment, the output current of output amplifier 26 flows into coil 36, becomes a kind of pattern, exports from the mode initialization of polarity comparer 28 and offers

output amplifier

26,27 respectively.Otherwise, when the input of input end 23 is high level, set and above-mentioned opposite pattern.And also the in-phase end to polarity comparer 28 provides reference voltage V REF, and is same with described three amplifiers (25-27), sets input by the described reference voltage that input end 24 provides, and sets the set-point of each reference voltage V REF.

Below, the concrete formation of

output amplifier

26 or 27 is described with reference to Fig. 2.

In order to provide drive current by lead-out terminal 41 or 42 coils 36 to servo load, output stage NPN transistor 1 and 2 (each base stage with emission voltage across poles be VF) is set, lead-out terminal 41 (42) is set at the tie point A of the collector of the emitter of transistor 1 and transistor 2.The collector of transistor 1 connects supply voltage V _CC, and its base stage is connected with the collector of transistor 6 by tie point B.The current potential of tie point B, by a pair of difference channel of forming by transistor 10,11, according to the control of input end 23 input and to the feedback input of the energising of coil 36, oxide-semiconductor control transistors 1 or any 1 conducting state wherein of 2 changeably.Be provided with the 1st idle loop of being formed by the constant current source 12 by transistor 1, diode 16,17 and transistor 4 and transistor 5 (the 1st shunt circuit) at output terminal 41 (42).Collector has connected supply voltage V _CCThe base stage of transistor 4 be connected the intermediate point of constant current source 12 and two diodes that are connected in series 16,17 (each forward voltage is identical with described VF), and collector and emitter connect supply voltage V respectively _CC, transistor 5 emitter.Also have, second idle loop (second shunt circuit) is made up of the transistor 2,3 by transistor 1 and diode 18 and constant current source 13.The collector and the base stage that are connected PNP transistor 3 between the base stage of NPN transistor 2 and the collector respectively, its annexation are that mutual inverted Darlington connects.The base stage of transistor 2 connects the collector of transistor 5, and the base stage of transistor 5 connects collector and the tie point C of constant current source 14 on same lead with described transistor 6.Tie point C connects the base stage and the constant current source 13 of transistor 3 by diode 18.

Have again, in each circuit that is provided with constant

current source

12,13 and 14, be provided with

switch

19,20,21 respectively,, carry out blocked operation, be switched on or switched off each circuit according to the output of polarity comparer 28.

The input stage of above-mentioned Linear Driving circuit 40 has been purchased differential amplifier, is made up of

transistor

10 and 11, and the common emitter of two transistor has connected constant current source 37.And, connect the collector of

transistor

10 and 8 respectively, and the collector of transistor 11 and 9, these transistors constitute general symmetric circuit, and the collector of output transistor 9 connects the base stage of transistor 7, and its emitter connects the base stage of described transistor 6.By the

feedback resistance

33 or 35 between lead-out terminal 41 (42), import the input terminal 38 that offers in the base stage setting of transistor 10 with feeding back.

Corresponding output amplifier

26 or 27 reverse input end impressed

voltage VIN.By resistance

32 or 34 reference voltage V REF is offered another input terminal 39,

corresponding output amplifier

26 or 27 in-phase input end impressed voltage VIN.

In the Linear Driving circuit 40 of above-mentioned formation, the conversion of described first and second idle loop is the output according to polarity comparer 28, and the output of controlling

output amplifier

26 and 27 becomes mutual reversed polarity.And

output amplifier

26 and 27 output are connected by coil 36, set when a side is the pattern of electric current inflow coil 36, and the opposing party is the electric current input pattern.

Below, by the

output amplifier

26 and 27 of the final output stage of electric current, the feedback action of Linear Driving circuit 40 is described.

For example, in the output amplifier 26 of final output stage, when its output voltage V 0 ^-Output voltage V 0 than another output amplifier 27 ⁺Hour (V0 ^-＜V0 ⁺), form described first idle loop, make inflow current I1 or ABSORPTION CURRENT I2 flowing through coil 36.That is to say that the output signal by polarity comparer 28 makes

switch

19 and 21 closures (ON), and, the 1st idle loop that makes switch 20 disconnect (OFF) formed.At this moment, import according to the control that described servo integrated circuit comes, and a pair of difference channel by forming by

transistor

10,11, set and compare V0 ^-The base potential of the transistor 5 of high-voltage level (tie point B), turn-on transistor 1 makes inflow current I1 flow to coil 36.On the one hand, according to described control input, conducting and V0 be with the base potential (tie point B) of the transistor 5 of voltage level, by shunt, provides electric current to the base stage of transistor 2, makes transistor 2 as conducting state, makes ABSORPTION CURRENT I2 steady flow.By this first idle loop, the saturation voltage VSAT of transistor 2 is set the dead voltage territory lower limit of

output amplifier

26,27 dynamic ranges.

So, when output voltage V 0 ^-Than another output voltage V 0 ⁺(V0 when big ^-＞V0 ⁺) also with described (V0 ^-＜V0 ⁺) time same, form described first idle loop, inflow current I1 or ABSORPTION CURRENT I2 are flowed.At this moment, under electric current injection state, as shown in Figure 5, when the phase place of the output voltage of lead-out terminal 41 (42) and output current produces skew, remove described first idle loop, form described second idle loop.That is to say that the output by polarity comparer 28 disconnects switch 19 and 21, and makes switch 20 closures, forms the 2nd idle loop.Therefore, the current potential at tie point B (or C) is V0 ^-Below the voltage level, transistor 1 ends, and because the constant current source 13 of second idle loop, by transistor 3 along separate routes, turn-on transistor 2 can produce ABSORPTION CURRENT I2.Therefore, transistor 2 and 3 connects by described inverted Darlington, and its output voltage is that the shunt of first idle loop may boundary voltage (V _CC-2VF-VSAT) more than, for example, even high to supply voltage V _CCNear, also can produce ABSORPTION CURRENT, can fully guarantee the stability of negative feedback action.Also have, second idle loop be set be since in first idle loop rising part of diode 16 and 17 2VF cancel out each other, be not subjected to the influence of second idle loop, make the lower limit of the dead voltage of dynamic range still keep the low value of VSAT.

Claims

1. coil-load driving circuit, has first output stage transistor with the load of unidirectional drive current supply coil, with second output stage transistor of the drive current of other direction being supplied with described coil load, has the mutual base stage of described first and second output stage transistor of common connection, connect each output terminal, and this tie point as the lead-out terminal that is connected with described coil load, simultaneously, with the output of described lead-out terminal feedback-type output amplifier as the feedback input, corresponding with the control input of described feedback-type output amplifier, change the current potential of the common tie point of described base stage, make the described first or second output stage transistor conducting, it is characterized in that:

Have first shunt circuit, this circuit since the output voltage of described lead-out terminal be closure state below the fixed boundary level, described second output stage transistor of this closure state conducting, with between the common tie point of described base stage and described lead-out terminal along separate routes;

Has second shunt circuit, this circuit is because the output voltage of described lead-out terminal is closure state than the high boundary level of described boundary level the time, described first shunt circuit open state the time, phase deviation along with the output voltage and the output current of described lead-out terminal, change along with described control input, described second output stage transistor of conducting, with between the common tie point of described base stage and described lead-out terminal along separate routes;

By described first shunt circuit, described second output stage transistor is become this saturation voltage of state of saturation, be set at the lower limit in the dead voltage territory of described output amplifier.