JPS63314165A - Load driving device - Google Patents

Abstract

PURPOSE:To reduce switching loss, by performing a control signal generation circuit to charge the current into capacitors with MOSFET periodically tuned OFF and by applying the voltage developed across this capacitor to each power source end of gate controlling circuits on the positive electrode. CONSTITUTION:A load drive circuit is equipped with transistor bridges composed of N-channel type MOSFET Q1-Q4, gate controlling circuits G1-G4 to control each FET Q1-Q4 and a control signal generation circuit CG. To the output terminal of this circuit a motor M1 is connected to supply drive current in normal and reverse directions. On this occasion, the control signal generation circuit CG is formed so that the capacitors C1-C2 are periodically charged through counterflow blocking diodes D1 and D2 with the FET Q1 & Q3 and Q2 & Q4 periodically turned OFF, while the voltage developed across these capacitors C1 and C2 is applied as a control power supply to the power source terminal of the gate controlling circuits G1 and G3. The control power supply can thereby be ensured at all times.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a load driving device that drives a load such as a motor using a DC power supply via a transistor bridge.

[Background technology] Conventionally, direct current? As a load drive device of this type in which a load such as a motor is driven by an It source via a transistor bridge, there is a load drive device as shown in FIG.

That is, P-channel type MOSFETQ,',Q,
'Oori N-channel type (7) MOS FET Q
2, Q4, and each MOSFET Q+', Q3', Q2. Gate control circuit G,~04 that controls Q, and each gate control @Qn
18G, ~G, and a control signal generation circuit CG that generates a control signal ffi input to the transistor bridge, a DC power supply Vin is connected to the input end of the transistor bridge, and a motor M1 is connected to the output end of each MOSFETQ, ',Q
,',Q, ,Q, were appropriately controlled to turn on and off the control signal generating circuit CG, so that a forward current or a reverse current could be arbitrarily passed through the motor M1. However, in such a conventional example, since P-channel type MOSFETs Q1'' and Q3' are used as switching elements on the positive side of the trunk stabilization, the configuration of the gate control circuit G1.G and its power supply system is Although it has the advantage of simplifying the process, the switching speed of the P-channel MOSFETQ,',Q,' is slow and the on-resistance between the source and drain is large. , Qz', Q2.
Q.

When performing PWM control by turning on and off at a high switching frequency, there is a problem in that switching loss increases and efficiency deteriorates.

Therefore, in order to solve such problems, as shown in FIG.
There was one in which a transistor bridge was constructed using chisel.

By the way, in place of the P-channel type MOSFETQ, °tQi1 of the conventional example shown in FIG. 7, an N-channel type MOSFETQ1. Q.

In the case of using gate control circuit G + = G
There was a problem that the power supply system of No. 3 became complicated and the loss increased. That is, the ground line of the control power supply that supplies power to the gate control circuits G, , G, which control the MOS FET Q + , Q 3 on the positive side of the DC power supply V in is set at the output end of the trunk stabilization. There is a need to. Therefore, in the conventional example, the capacitors C1 and C are constantly charged from the DC power supply Vin via the reverse current blocking diode D + -D2 and the resistor R8.
By applying the voltage across the capacitors C+ and C2 as a control power source to the gate control circuits G, , G, a control power source is obtained with the output end of the transistor bridge as a ground line.

However, in such a conventional example, in order to always ensure a charging path for the capacitors C, C2, the resistor R1 is
, R2, the circuit configuration becomes complicated, and the charging current of zlC+tC2 is connected to which resistor R+ and R2.
Since the gate current of Q, Q3 flows, the resistance R8゜R2
There was a problem in that the power loss caused by this increased and a large amount of heat was generated, and the shape also became larger.

In other words, in this type of load drive device, when the load becomes heavy, the positive side MOSFET Q or Q3 is always turned on to allow the maximum current to flow, so the resistance R
If l-R2 is not provided, the capacitor C+-C2 may not be charged for a long period of time, resulting in the inconvenience that control power for the six gate circuits Glt cannot be obtained normally. Therefore, in the conventional example, a resistor R1 or R2 for capacitor charging was added in order to secure a charging path and always obtain control power even in the above case.
In addition to complicating the circuit configuration, there is a problem that current continues to flow through the resistors R11R2, resulting in wasted power consumption.Furthermore, it is necessary to use large capacity resistors R2 and R2, so the device There was a problem in that as the size increased, the cost also increased.

[Object of the Invention] The present invention has been made in view of the above points, and its purpose is to provide a load driving device that has a simple circuit configuration, has low power loss and heat generation, and can be easily miniaturized. Our goal is to provide the following.

[Disclosure of the Invention 1 (Structure) The present invention includes a transistor bridge composed of N-channel MOSFETs, a gate control circuit that controls each MO6FET, and a control signal that is input to each gate control circuit. A DC power supply is connected to the input end of the transistor bridge, and a load such as a motor is connected to the output end of the transistor bridge. In a load drive device formed with a control signal generation circuit so that a directional current or a reverse current can flow arbitrarily, a series circuit of a reverse current blocking diode and a capacitor is connected in parallel to each MOSFET on the positive side of a DC power supply. However, the positive side MOSFET of the MOSFET series circuit connected in parallel to the DC power supply is periodically turned off, and the negative side MOSFET is also periodically turned off, and the capacitor is periodically turned off via the reverse current blocking diode. f to be charged
By applying the voltage across the capacitor as a control power source to the power supply terminal of the gate control circuit that controls the positive side MOSFET as well as the ilJ control signal generation circuit, the circuit configuration is simple, and power loss and heat generation are reduced. The object of the present invention is to provide a load driving device that has less noise and can be easily miniaturized.

(Embodiment) FIG. 1 shows an embodiment of the present invention, which includes a transistor britsuno composed of N-channel MOSFETs QI to Q4, and gate control circuits 61 to G4 that control each MOSFETQ, to Q4. , each gate control circuit 01-G,
Control signal generation circuit CG that generates control signals input to
By connecting the DC power supply Vin to the input terminal of the transistor Blitzno, and connecting the motor M to the output terminal, and appropriately controlling the on and off of each MOSFET Q, ~Q, the load M1 can be properly connected. In a load driving device similar to the conventional example shown in FIG. 8, in which a control signal generating circuit CG is formed so that a directional current or a reverse current can flow arbitrarily, each MOSFET Q1-Q3 on the positive side of the DC power supply Vin
A series circuit of reverse current blocking diodes D, D2 and capacitors C+ and C2 are connected in parallel to the DC power supply Vi.
MOSFET Q on the positive side of the MOSFET series circuit connected in parallel to n.

Q is periodically turned off and M08F on the negative electrode side
ETQ2. Q is periodically turned off and capacitor C,,
The control signal generating circuit CG is formed so that the capacitors C and C are periodically charged via the reverse blocking diodes DI and D2, and the voltage across the capacitors C and C2 is connected to the positive side MOSFET Q. +, Q3 is applied as a control power source to the power terminals of the gate control circuits G, , G, which control the gate control circuits G, , G,.

The operation of the embodiment will be specifically explained below.

Now, the basic operation is the same as the conventional example, and it fits!
The Ill signal generation circuit CG generates a PWM control signal that turns on and off the MOSFETQ, ~Q4, and is output from each gate control circuit G, ~G4 to MO8FET.
Gate voltage Vg applied to the gate of Q I-Q 4
1 to Vg< has a waveform as shown in FIG.

Here, when the gate voltages vg, , vg4 are "H", MOS FET Q5. When Q4 is turned on, a positive current as shown by arrow A flows through motor M, and gate voltage Vg2. MOSFET when Vg is “H”
QztQx turns on and a reverse current as shown by arrow B flows.

On the other hand, charging of the capacitor C1 for supplying control power to the power supply terminal of the gate control circuit G+-04 is performed using the MOSFET.
ETQl is performed via the diode D during the T3 period when MOSFETQz is on at t7L, and the capacitor C2 is charged when MOSFETQ3 is turned off and the MOSFETQz is turned off.
In Figure 6, ICps I
e2 indicates the charging current of capacitors C, , C2, and I g3. I gz is the gate control circuit G + -G
3 shows the discharge current from capacitors CI and C2 flowing through the capacitors CI and C2. In the example, the positive electrode side MOSFETQ,
, Q3 is periodically turned off and the negative side MOSF
ETQ, -Q4 is periodically turned off and capacitor C1-
The control signal generating circuit CG is formed so that C2 is periodically charged via the reverse current blocking diodes D, , D, so that the control power source for the gate control circuits G, , G is always secured. Therefore, as in the conventional example shown in Fig. 8, the resistor R+,
Since R2 is not required, the circuit configuration becomes simple, power loss and heat generation can be reduced, and miniaturization can be easily achieved. In addition, in the embodiment, even when the load becomes heavy, the control state by PWM control remains at 1.
00% control or 0% control (on duty is 100
% or 0%), and MOS F
E T Q + " Q4 is not kept on or off for a long period of time to ensure a regular charging period for the capacitors C, , C2 and to secure the control power for the gate control circuits G, , G. It has become.

Hereinafter, the operation of rotating the DC motor M1 at a constant speed by PWM control will be specifically explained. Now, as shown in Fig. 3, in each MOSFETQ, ~Q4 of the transistor bridge, there is a parasitic diode I) o+~D04 between the source and drain, and the output from the gate control circuit G1~G4 is Gate signal vg,,vg,,
vg2. When vg is a signal as shown in FIGS. 4(a) and 4(b), the current IL flowing through the motor M is as shown in FIG. 4(c). That is, M
OS FET Q 1-Q4 are on, M OS
When FETQ2-Qs is off, current ■L flows through the motor M along the path shown by the solid line, and then MOS FETQl-Q4
7, the back electromotive current of the motor M (the dead current shown in the shaded area in the figure) flows along the path shown by the dotted line. While this back electromotive current flows through the parasitic diode, the MOS
Since the source and drain of FETQs are reverse biased, MOSFETQ3 does not turn on even though the gate signal VD is high.Next, the back electromotive current attenuates to 0. Then, a forward bias is applied between the source and drain of MOSFETQ3, so the MOS
FETQ turns on and MOS FETQ2-
Current flows through Q3, and the direction of current IL flowing through motor M is reversed.

Figure 5 shows the process of passing an average current L through the motor M.First, as shown in Figure 5(a), the MOS
F E T Q 1t Q 4 on duty 10
Start with the on-duty increased appropriately so that it does not reach 0%, and gradually decrease the on-duty until the current ■L flowing through motor M1 reaches IL+, then reduce the on-duty to 50%.
If the current is stabilized, a substantially constant average current ILI will thereafter flow through the motor M1. In addition, in the same way, motor M
Current flowing through 1. It goes without saying that even in the opposite case, the average current can be controlled by PWM control.

FIG. 6 shows another embodiment, showing a load drive device that drives a three-phase motor M as a load, and shows a three-phase trunk stub consisting of N-channel MOSFETs Q, ~Q6. gate control circuits G1 to G that control each MO6FETQ, ~Q6, a control signal generation circuit CG, and reverse current blocking diodes D, -D connected in parallel to both ends of MOSFET Q + -Q y -Q s. It is composed of capacitors C, -C, and charged via . Note that since the operation is the same as that of the previous embodiment, the explanation will be omitted.

Further, although the above embodiment shows an example in which motors M1 to M3 are connected as loads, it is also possible to connect a transformer as a load to configure a switching power supply.

[Effect 1 of the Invention As described above, the present invention provides an N-channel MOSFET.
A trunk bridge configured with and each MOSFE
The transistor bridge is equipped with a gate control circuit that controls the T, and a control signal generation circuit that generates control signals to be input to each gate control circuit.A DC power supply is connected to the input end of the transistor bridge, and a Connect the load, each M
In a load driving device formed with a control signal generation circuit so that a forward current or a reverse current can be arbitrarily applied to the load in order to properly control ON/OFF of the OSFET, the positive terminal of the DC power source is A series circuit of a reverse current blocking diode and a capacitor is connected in parallel to each MOSFET, and the positive side MOSFET of the MOSFET series circuit connected in parallel to the DC power supply is periodically turned off, and the negative side MOSFET is periodically turned off. A control signal generation circuit is formed so that the capacitor is periodically charged via a reverse current blocking diode, and the voltage across the capacitor is connected to the power supply terminal of a gate control circuit that controls the positive side MOSFET. This is applied as a control power source, and since the transistor circuit is configured using an N-channel MOSFET, switching loss can be reduced compared to the conventional example shown in FIG.
Figure 8 Unlike the conventional example, resistors R+ and R2 are not required, making circuit borrowing easier and reducing power loss by 1.
This has the effect of reducing heat generation and making it easier to downsize.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of one embodiment of the present invention, Figs. 2 to 5 are explanatory diagrams of the same operation as above, Fig. 6 is a circuit diagram of another embodiment, and Fig. 7 is a circuit diagram of an embodiment of the present invention.
The figure is a circuit diagram of a conventional example, and FIG. 8 is a circuit diagram of another conventional example. Q, -Q6 are MOSFETs, G, ~G6 are gate control circuits, CG is a control signal generation circuit, Vin is a DC power supply, M,
, M3 is a motor, D1-D3 are diodes, C1-C1
is a capacitor. Agent Patent Attorney Ishi 1) Ai 7 Figure 2 Figure 5 Figure 6 Figure 7 Procedural Amendment (Voluntary) January 16, 1985

Claims (1)

[Claims] (1) A transistor bridge configured with N-channel MOSFETs, a gate control circuit that controls each MOSFET, and a control signal generation circuit that generates a control signal input to each gate control circuit. By connecting a DC power source to the input end of the bridge and connecting a load such as a motor to the output end, and controlling each MOSFET on and off appropriately, a forward current is generated in the load.
Alternatively, in a load drive device formed with a control signal generation circuit so that a reverse current can flow arbitrarily, a series circuit of a reverse current blocking diode and a capacitor is connected in parallel to each MOSFET on the positive side of a DC power supply, and a DC The positive side MOSFET of the MOSFET series circuit connected in parallel to the power supply is periodically turned off, and the negative side MOSFET is turned off periodically.
A gate control circuit forms a control signal generation circuit so that the OSFET is periodically turned off and the capacitor is periodically charged via the reverse current blocking diode, and controls the voltage across the capacitor to the positive side MOSFET. A load driving device characterized in that a control power source is applied to the power source end of the load drive device.