JPH08162934A - H bridge circuit providing with boosting circuit - Google Patents

Abstract

PURPOSE: To provide an H bridge circuit provided with a boosting circuit capable of increasing a boosting amount and simplifying circuit constitution. CONSTITUTION: The boosting circuit 2 composed of only two stages of diode- capacitor serial circuits for which a transistor circuit and a dedicated oscillator are not incorporated is adopted so as to drive the high side switches H1 and H2 of this H bridge circuit 1 for so called PWM bidirectional drive constituted of an N type channel insulated gate transistor. For the boosting circuit 2, a terminal part on the capacitor side of the serial circuit on a lower side composed of a lower side diode D1 and a lower side capacitor C1 is connected to one of the output terminals of the H bridge circuit and the anode of the lower side diode D1 is connected to the higher side power supply terminal of the H bridge circuit. The terminal part on the capacitor side of the serial circuit on a higher side composed of a higher side diode D2 and a higher side capacitor C2 is connected to the other output terminal, of the H bridge circuit and the anode of the higher side diode D2 is connected to the cathode of the lower side diode D1. Since the boosting circuit 2 is driven by the output voltage of the PWM controlled H bridge circuit, the circuit constitution is simplified.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an H-bridge circuit having a booster circuit for driving an N-type channel insulated gate field effect transistor (hereinafter referred to as an NMOS transistor) used as a high side switch.

[0002]

2. Description of the Related Art A pair of inverters each having a high-side switch and a low-side switch, which are N-type channel insulated gate transistors, connected in series are provided, and a control voltage of a predetermined cycle is applied to each switch gate electrode. H that bidirectionally drives the load between the output terminals of the inverter
Bridge circuits are widely used.

The problem with this H-bridge circuit is that it is necessary to apply a gate voltage higher than the power supply voltage to drive the high-side switch composed of an NMOS transistor that operates as a source follower. For this reason, a booster circuit for boosting the power supply voltage is provided. It is necessary. Although various types of booster circuits have been put into practical use or proposed, all of them require a complicated circuit configuration such as an electronic circuit such as an inverter or an oscillation circuit and a capacitor, but the booster amount is small, and the booster amount is increased. There was a demand for simplification of the configuration.

The present invention has been made in view of the above problems, and an object thereof is to provide an H-bridge circuit having a booster circuit capable of increasing the boosting amount and simplifying the circuit configuration.

[0005]

The first structure of the present invention is as follows.
A bridge unit having a pair of inverters each configured by serially connecting a high-side switch and a low-side switch, which are N-type channel insulated gate transistors, and control of a predetermined cycle in which the gate electrodes of both the high-side switches have mutually opposite phases. A high-side switch control unit for applying a voltage and a low-side switch control unit for applying a control voltage of a predetermined cycle having opposite phases to the gate electrodes of the low-side switches, and between the output terminals of the both inverters. A drive circuit for bidirectionally driving a connected load in a PWM manner with a predetermined duty ratio, an anode connected to the drain electrode of the high-side switch, and a cathode connected to one output end of both inverters through a low-side capacitor. The lower diode and the anode are A high-side diode connected to the cathode of the high-side diode and having a cathode connected to the other output terminal of the two inverters through a high-side capacitor, the cathode of the high-side diode being the high side of the drive circuit. It is an H-bridge circuit having a booster circuit characterized in that it is connected to a high-potential power supply end of a switch control unit.

A second structure of the present invention is characterized in that, in the first structure, the load further comprises a coil. According to a third aspect of the present invention, a bridge portion having a pair of inverters respectively configured by serially connecting a high-side switch and a low-side switch, which are N-type channel insulated gate transistors, and gate electrodes of both the high-side switches are provided. A high-side switch control section for applying control voltages of opposite cycles having predetermined phases, and a low-side switch control section for applying control voltages of opposite cycles having opposite phases to the gate electrodes of the low-side switches. A drive circuit for bidirectionally driving a load connected between the output terminals of the two inverters at a predetermined duty ratio, an anode connected to the drain electrode of the high side switch, and a cathode connected to the low side through a low side capacitor. Connected to one output end of switch controller And a high-side diode whose anode is connected to the cathode of the low-side diode and whose cathode is connected to the other output end of the low-side switch control section through a high-side capacitor. Is connected to a high-potential power supply terminal of the high-side switch control section of the drive circuit, and is an H-bridge circuit having a booster circuit.

A fourth structure of the present invention is the above-mentioned first or second structure.
In the above configuration, the cathode of the high-side diode is connected to the anode of the output diode, and the cathode of the output diode is grounded through the output capacitor and connected to the high-level power supply terminal of the high-side switch controller. I am trying.

[0008]

In the first structure of the present invention, the two-stage diode is used for driving the high side switch of the so-called PWM bidirectional driving H bridge circuit composed of N-type channel insulated gate transistors. A booster circuit that consists of a capacitor series circuit and does not have a transistor circuit or a dedicated oscillator is used. That is, in this booster circuit, the capacitor-side end of the low-side series circuit including the low-side diode and the low-side capacitor is connected to one output end of the H-bridge circuit, and the anode of the low-side diode is the H-bridge circuit. Is connected to the high-side power supply end of. The end of the high-side series circuit composed of the high-side diode and the high-side capacitor on the capacitor side is connected to the other output end of the H-bridge circuit, and the anode of the high-side diode is connected to the cathode of the low-side diode. It With this configuration, with the above-described simple booster circuit configuration, a high boosted voltage can be supplied from the cathode of the high-side diode, and the power supply voltage of the high-side switch control unit that drives the high-side switch of the H-bridge circuit can be obtained. Can be used.

That is, in this configuration, both output terminals of the PWM bidirectionally driven H bridge circuit are periodically supplied with the power supply voltage (V
b)) and the ground potential to complementarily swing each other, and if the potentials at the one ends of the two capacitors are swung by the voltages at these output ends, the booster circuit does not need to include a transistor or an oscillator. Also focuses on the fact that boosting is possible. Therefore, according to this configuration, a high boosted voltage can be obtained with a simple circuit configuration.
Further, in this configuration, when the PWM control carrier frequency of the H-bridge circuit is low, the driving power of the high-side switch of the H-bridge circuit is reduced, but the operating frequency of the booster circuit can be reduced accordingly, and power saving can be achieved. it can. Further, when the H-bridge circuit is inactive, the booster circuit can also be automatically disabled, and power saving can be achieved.

A second structure of the present invention is characterized in that, in the first structure, the load is a coil. By doing so, it is possible to further boost the voltage by the electromagnetic energy accumulated in the coil. According to a third configuration of the present invention, in addition to the first configuration, one end of each of the capacitors is connected not to both output ends of the H bridge circuit but to both output ends of the low-side switch control section.
It is possible to obtain the same operational effects as those of the configuration.

A fourth structure of the present invention is the above-mentioned first or second structure.
In the above configuration, further, a third-stage diode-capacitor series circuit including an output diode and an output capacitor is provided between the output end of the high-side diode-capacitor series circuit and the high-side power supply end of the high-side switch control section. It is interposed and the end of the output capacitor is grounded. With this configuration, it is possible to achieve the effect that the power supply voltage of the high-side switch control unit does not change due to clocking of the low-side and high-side capacitors.

[0012]

【Example】

(Embodiment 1) An embodiment of an H-bridge circuit with a booster circuit according to the present invention will be described below with reference to FIG. This booster H-bridge circuit includes an H-bridge circuit (bridge unit) 1 including enhancement type NMOS transistors,
Booster circuit 2, drive circuit (high-side switch control unit) 3 that forms the gate voltage of high-side switches H1 and H2 of H-bridge circuit 1, and gate voltage of low-side switches L1 and L2 of H-bridge circuit 1. It consists of a drive circuit (low side switch control unit) 4 and
Both drive circuits 3 and 4 form a drive circuit according to the present invention.

As is well known, the H-bridge circuit 1 has an inverter having a high side switch H1 and a low side switch L1 connected in series, and an inverter having a high side switch H2 and a low side switch L2 connected in series. A coil L that is a reactance load is connected between the output terminals of both inverters. Boost circuit 2
Is a two-stage cascaded diode-capacitor series circuit, the low-side diode-capacitor series circuit is formed by connecting the low-side diode D1 and the low-side capacitor C1 in series, and the high-side diode-capacitor series circuit is
A high-side diode D2 and a high-side capacitor C2 are connected in series. The anode of the low-side diode D1 is applied with the battery voltage Vb together with the drain electrodes of the high-side switches H1 and H2 of the H-bridge circuit 1, and the end of the low-side capacitor C1 is connected to the output end of one inverter. . The anode of the high-side diode D2 is connected to the cathode of the low-side diode D1, and the end of the high-side capacitor C2 is connected to the output end of the other inverter. The cathode of the high-side diode D2 is connected to the high-potential power supply terminal of the drive circuit 3 that forms the high-side switch control unit, and supplies the drive circuit 3 with the power supply voltage.

The drive circuit 4 constitutes a low-side switch control section, and forms a gate voltage applied to the low-side switches L1 and L2 using the battery voltage as a power supply voltage. These drive circuits 3 and 4 are power amplification stages composed of NMOS transistor circuits, and power-amplify the PWM control signal waveform input from the PWM control signal generation circuit 5 and apply it to the gates of the respective transistors of the H-bridge circuit 1. . The configuration of such circuits 3 to 5 and the H bridge circuit 1 based on the PWM control signal output from these circuits
Since the PWM bidirectional operation itself is known, detailed description thereof will be omitted. However, assuming that the battery voltage is 8V, the circuit operation of FIG. 1 will be described below.

The inverter on the left side in FIG. 1 is 6, the inverter on the right side in FIG. 1 is 7, the potential at the output end of the inverter 6 is V1, the potential at the output end of the inverter 7 is V2, and the cathode potential of the low-side diode D1. V3, drive circuit 3
Is Vg, the potential drop of the diodes D1 and D2 is 0.7V, and the threshold voltage of the high-side switches H1 and H2 is Vt (for example, 1.5V).

First, H1 and L2 are off, H2 and L1 are on, V1 = 0V, V2 = Vb = 8V, V3 = Vb-0.
From the state of 7V = 7.3V, H1, L2 are on, H2,
It is assumed that L1 is off, V1 = Vb, and V2 = 0V. By swinging V1 from 0V to 8V,
Assuming that parasitic capacitance does not exist at the cathode of the low-side diode D1, V3 is 7.3 V if capacitance division is ignored.
Boosted to + 8V = 15.3V. Here, the current in the high-side diode D2 is very small, which causes V
Assuming that 3 does not almost decrease, V3 is 15.3.
Since it becomes V, Vg becomes 14.6V by subtracting 0.7V of D2 drop from V3.

Next, H1 and L2 are on, H2 and L1 are off, V1 = Vb, V2 = 0V, V3 = 15.3V, Vg.
= 14.6V, H1, L2 are off, H2, L
It is assumed that 1 is turned on, V1 = 0V, and V2 = Vb = 8V. By swinging V1 from 8V to 0V, the high side diode D2 is cut off, and
If the current consumption and the parasitic capacitance of the drive circuit 3 are neglected for convenience, Vg swings from 0V to 8V, and the potential change through the capacitor C2 affects Vg.
Is boosted from 14.6V to 22.6V.

In practice, since the drive circuit 3 consumes a large amount of current and has a large parasitic capacitance, its power supply voltage Vg is not boosted as described above, but it is easily understood that it is boosted to a necessary and sufficient value. When the battery voltage Vb is 8V, the high side switch H that operates as a source follower
Since the threshold voltages of 1 and H2 are 1.5V, 8V + 1.5V + 6V (gate voltage of the high side switch H1 with respect to the ground is required to sufficiently turn on the high side switches H1 and H2 (operate in the saturation region). Therefore, if the drive circuit 3 is composed of an E / E circuit of an NMOS transistor and voltage drop is taken into consideration, Vg should be secured at about 18.5 V. , This H bridge circuit 1
Turns out to work well. FIG. 2 shows the voltage waveform of each part of the circuit of FIG.

Next, the operation of the H bridge circuit 1 at the time of rising will be described. When the power is turned on, or when the PWM control signal is operated for a long time with a duty ratio of 0% or 100%, Vg is not boosted, and thus Vb-0.7V × 2 = 6.6V, Only the gate voltage of 5 V or less can be applied to the high side switch H1. However, the duty ratio is 0% from the circuit 5.
Or if a PWM control signal that is not 100% is output, C
1 and C2 perform charge transfer at a high speed, and Vg is quickly boosted to a required level, which is not a problem.

Other features of this embodiment will be described below. In this embodiment, a coil L, that is, a reactance load, is used as the load of the H bridge circuit 1. For this,
Boosting efficiency can be greatly improved. More specifically, first, H1 and L2 are off, H2 and L1 are on, and V
From the state of 1 = 0V, V2 = Vb = 8V, H1 and L2 are on, H2 and L1 are off, V1 = Vb, V2 = 0V, V
3 = Vb−0.7V = 7.3V.
V2 becomes 0V when L2 is turned on, but the electromagnetic energy accumulated in the coil L transiently boosts V1, and V1 becomes slightly higher than the battery voltage vb. Therefore, it is understood that V3 is swung in the positive direction more greatly than the above description. The same applies to the swing of the capacitor C2. This drop is particularly effective when the gate voltages of the high side switches H1 and H2 are low.

(Embodiment 2) In this embodiment, in FIG. 1, the end of the low-side capacitor C1 is not one output end of the H bridge circuit 1 but one output end of the drive circuit (low side switch control unit) 4. And the end of the high-side capacitor C2 is connected not to the other output end of the H-bridge circuit 1 but to the other output end of the drive circuit 4.

The output voltage Vg3 of the drive circuit 4 for outputting the gate voltage of the low-side switches L1 and L2 is in phase with the output voltage V2 of the H-bridge circuit 1, and the output voltage Vg
4 has the same phase as the output voltage V1 of the H bridge circuit 1, the same effect as that of the first embodiment can be obtained. (Embodiment 3) In this embodiment, an output (reverse current blocking) diode-capacitor series circuit 9 is added between the cathode of the high-side diode D2 and the power supply terminal of the drive circuit 3 in FIG. is there.

The output (reverse current blocking) diode-capacitor series circuit 9 comprises a series circuit of an output diode D3 and an output capacitor C3, and the anode of the output diode D3 is the cathode of the high-side diode D2. It is connected and the end of the output capacitor C3 is grounded. The cathode of the output diode D3 is connected to the high potential power supply terminal of the drive circuit 3.

In this way, the high-side capacitor C2
When the cathode potential V4 of the high-side diode D2 is boosted and swung by the potential swing of V4, V4 becomes Vg.
When the voltage drops to + 0.7V or less, the output diode D3 is cut off, Vg does not decrease, and the fluctuation of the power supply voltage of the drive circuit 3 can be effectively reduced, which is very practical. Easy to use.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an H-bridge circuit having a booster circuit according to a first embodiment of the present invention.

FIG. 2 is a timing chart showing a potential change in each part of the circuit of FIG.

FIG. 3 is a circuit diagram showing a main part of an H bridge circuit having a booster circuit according to a second embodiment.

FIG. 4 is a circuit diagram showing a main part of an H bridge circuit having a booster circuit according to a third embodiment.

[Explanation of symbols]

H1 and H2 are high side switches, L1 and L2 are low side switches, 1 is an H bridge circuit (bridge section), 2
Is a booster circuit, 3 is a drive circuit (high-side switch control unit), 4 is a drive circuit (low-side switch control unit), D1 is a low-side diode, D2 is a high-side diode, D3 is an output diode, and C1 is a low-side capacitor. , C2 is the high-side capacitor, and C3 is the output capacitor.

Claims (4)

[Claims] 1. A bridge section having a pair of inverters each composed of a high-side switch and a low-side switch, which are N-type channel insulated gate transistors, connected in series, and gate electrodes of the both high-side switches having opposite phases. And a low-side switch control section for applying a control voltage of a predetermined cycle having opposite phases to the gate electrodes of the low-side switches. A drive circuit for bi-directionally driving a load connected between output terminals of the PWM at a predetermined duty ratio; an anode connected to the drain electrode of the high side switch and a cathode connected to one of the two inverters through a low side capacitor. A low side diode connected to the output end, A high-side diode whose node is connected to the cathode of the low-side diode and whose cathode is connected to the other output terminal of the two inverters through a high-side capacitor, wherein the cathode of the high-side diode is of the drive circuit. An H-bridge circuit having a booster circuit, which is connected to a high-potential power supply terminal of the high-side switch controller. 2. The H-bridge circuit having a booster circuit according to claim 1, wherein the load comprises a coil. 3. A bridge section having a pair of inverters each composed of a high-side switch and a low-side switch, which are N-type channel insulated gate transistors, connected in series, and gate electrodes of both of the high-side switches having opposite phases. And a low-side switch control section for applying a control voltage of a predetermined cycle having opposite phases to the gate electrodes of the low-side switches. A drive circuit for bidirectionally driving a load connected between the output terminals of the low-side switch controller with an anode connected to the drain electrode of the high-side switch and a cathode through a low-side capacitor of the low-side switch controller. The low side datum connected to one output An anode, and a high-side diode whose anode is connected to the cathode of the low-side diode and whose cathode is connected to the other output end of the low-side switch control section through a high-side capacitor, wherein the cathode of the high-side diode is Is connected to the high-potential power supply terminal of the high-side switch control section of the drive circuit, the H-bridge circuit having a booster circuit. 4. The cathode of the high-side diode is connected to the anode of the output diode, and the cathode of the output diode is grounded through an output capacitor and connected to the high-side power supply terminal of the high-side switch control section. Alternatively, an H-bridge circuit including the booster circuit according to item 2.