JP2002272095A - Switching signal generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an efficient switching signal generator that has a large phase margin, and can stably control with high-frequency switching in a switching power supply using a ΔΣ modulator. SOLUTION: The ΔΣ modulator comprises an adder, an integrator, and a quantizer, a gate driver circuit is provided in the input of a power switch element, the output of the quantizer is inputted to the gate driver circuit, and the output of the gate driver circuit is fed back to the adder of the ΔΣmodulator, thus increasing the phase margin in high-frequency switching, and hence providing an efficient switching signal generator of the ΔΣ modulator type switching power supply where DC transmission linear characteristics are improved to DC input and stable control can be made.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching power supply using a .DELTA..SIGMA. Modulator, and more particularly to a switching signal generator in which a switching signal of a power switch element is fed back from a gate driver circuit output to the modulator.

[0002]

2. Description of the Related Art A conventional PWM (pulse modulation) type switching signal generator modulates an input signal by changing a pulse width. That is, as shown in the block diagram of the PWM switching signal generator in FIG. 2, a gate signal can be generated from the input signal 1 by the PWM oscillator 18, and the signal can be amplified by the gate driver circuit 6 to drive the power switch element 7. However, in the PWM method, the distortion generated in the gate driver circuit 6 could not be corrected.

FIG. 6 shows a block diagram in which a conventional PWM type switching signal generator is applied to a step-down chopper. The voltage applied to the load is compared with the reference voltage 17 and input to the PWM oscillator 18.
However, since there is no direct feedback path from the gate driver circuit 6, it is impossible to directly correct the distortion generated in the gate driver circuit 6.

Further, as shown in FIG. 3, instead of a PWM oscillator, an input signal is integrated by an integrator 3 and is quantized to generate a 1-bit output signal. Although a switching signal generator for driving the power switch element 7 can be provided by outputting the drive signal, the distortion generated in the gate driver circuit 6 can be corrected because the feedback is performed before the gate driver input. Did not.

FIG. 7 shows a block diagram in which a conventional ΔΣ switching signal generator is applied to a step-down chopper. In this method, the voltage applied to the load and the reference voltage 17 are compared and input to the ΔΣ modulator 5, and the power switch element 7 is controlled by the output of the Δ５ modulator 5, but has a direct feedback path from the gate driver circuit 6. Therefore, it is impossible to directly correct the distortion generated in the gate driver circuit 6.

As a result, the distortion of the gate driver circuit 6 for directly driving the power switch element 7 cannot be removed, and the linearity of the ΔΣ modulator is deteriorated.

The distortion generated in the gate driver circuit in both the PWM system and the conventional ΔΣ system causes an error in the output signal of the PWM oscillator in the PWM system, and in the output signal of the ΔΣ modulator and the output signal of the gate driver in the conventional ΔΣ system. However, when used as switching power supply control, there is a disadvantage that the phase margin is small and the control becomes unstable, especially when operated at high frequency.

Further, a phase correction circuit is added to prevent oscillation. However, in addition to an increase in the number of parts and an increase in cost, in order to design an optimal circuit, it is necessary to use an actual circuit. In many cases, experiments and confirmations have been made, making stable circuit design difficult and increasing development time.

Further, there has been a method of improving the linearity by inputting an analog signal and feeding back an output signal of a power switch element as in a switching amplifier using ΔΣ modulation as disclosed in Japanese Patent Application Laid-Open No. 2000-307359.

FIG. 5 shows a conventional ΔΣ modulation system for feeding back an output signal of a power switch element.
FIG. 1 is a block diagram of the conventional method. However, when the conventional method is used as switching power supply control, there are the following problems.

When the output current of the switching power supply is small, there is a discontinuous region where the current flowing through the inductance in the power supply circuit is discontinuous. When the current flowing through the inductance becomes 0 in this discontinuous region, oscillation occurs due to the capacitance component and the inductance component in the power supply circuit.

In the method in which the output signal of the power switch element is fed back to the ΔΣ modulator as shown in FIG. 5, the noise due to this oscillation is also fed back, and the number of switching of the ΔΣ modulation output is significantly increased, resulting in an increase in switching loss. However, there is a problem that the power supply efficiency is reduced.

That is, in the conventional switching signal generation method, the linearity of the DC transmission characteristic is poor because the distortion generated in the gate driver is difficult to remove, and the phase margin is small because the linearity is not good, so that the oscillation phenomenon easily occurs. .

Further, in the method using Δ を 持 つ modulation having a feedback path from a stage subsequent to the power switch element in order to improve the linearity, there is a problem that power supply efficiency is reduced due to noise at the time of discontinuous current.

[0015]

SUMMARY OF THE INVENTION In a switching power supply using a ΔΣ modulator, there is provided a switching signal generator having high efficiency, a large phase margin, and capable of performing stable control by high frequency switching.

[0016]

According to the present invention, an analog input signal or a multi-bit digital signal is input to a ΔΣ modulator, and the modulated signal is amplified by a gate driver circuit. In the switching power supply for switching the power switch element by the signal, the output of the gate driver is fed back to the ΔΣ modulator.

The ΔΣ modulator includes at least one adder, an integrator, and a quantizer, and at least one of the outputs of the gate driver circuit connected to the quantizer output.
One adder input has a feedback path, and has an integrator connected to the output of the adder, with at least one of the integrator outputs connected to the quantizer.

An adder serving as an input of the ΔΣ modulator and an integrator connected to the output of the adder include an analog adder and an analog integrator when a continuous time signal such as an analog signal is input to the modulator. When a discrete time signal such as a multi-bit digital signal is input to the modulator, a digital adder and a digital integrator can be used.

The quantizer is a quantizer that performs sampling on a discrete time signal. The quantizer receives an output signal of the quantizer and is connected to an input of a gate driver circuit for supplying a current and a voltage sufficient to drive a power switch element. Have been.

The feedback path includes an attenuator that adapts the large amplitude pulse signal of the gate driver circuit to the ΔΣ modulator input signal level. However, even if the output level of the gate driver circuit and the input of the ΔΣ modulator match from the beginning and no attenuator is required, it is needless to say that an attenuator with an attenuation rate of 0 is considered to be included.

Since there is a feedback path from the gate driver output connected to the quantizer output to the modulator input, distortion generated in the gate driver is reduced, and the conventional PW
Distortion generated in the gate driver can be directly fed back as compared with the Δ M modulator which is fed back immediately after the M system and the conventional quantizer.

Further, since the output from the gate driver circuit connected to the output of the quantizer is directly fed back to the input of the modulator, the linearity of the input / output characteristics is good, the phase margin is increased, and oscillation hardly occurs.

By directly feeding back from the gate driver output, distortion generated in the gate driver circuit can be fed back directly, and the switching loss is reduced when the switching power supply is adapted to have less noise compared to the case where the feedback is performed at the subsequent stage of the power switch element. Can be reduced.

It is clear that the output is amplified to DC power by converting the analog input signal into DC voltage, and it can clearly function as a DC switching power supply. However, a rectifying / smoothing circuit is inserted after the power switch element, and ΔΣ It is also possible to configure as a modulation type chopper power supply.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a switching signal generator according to the present invention will be described with reference to the accompanying drawings. In the description of the drawings, the same members are given the same reference numerals,
Duplicate description will be omitted.

FIG. 1 shows an embodiment of the present invention, and FIG. 1 is a block diagram thereof. In this circuit diagram, an input signal 1 is input to an adder 2, an output of the adder 2 is input to a quantizer 4 through an integrator 3, and an output of the quantizer 4 is output to a gate driver circuit 6, The output of the gate driver circuit 6 is supplied to a power switch element 7. The output of the gate driver circuit 6 has a path that passes through the attenuator 19 and is fed back to the adder 2.

Compared with the conventional method in which the output of the quantizer 4 is fed back to the adder 4, the output of the gate driver circuit 6 for directly amplifying the voltage and current sufficient to drive the power switch element 7 as in the present invention is used The feedback reduces distortion and improves the linearity of the DC transmission characteristics. FIG.
Indicates this DC transmission characteristic.

FIG. 8 shows an embodiment in which the present invention is applied to a ΔΣ modulation type step-down chopper. The voltage output to the load is compared with the reference voltage 17 to amplify the difference voltage, and the difference voltage is calculated as ΔΣ
The signal modulated by the modulator 5 is output to the gate driver circuit 6, and the power switch element 7 is driven by the gate drive signal and fed back to the ΔΣ modulator 5.

The power supply input is an analog signal. For example, when a DC voltage is input, the output of the power switch element 7 can obtain a power-amplified DC voltage. That is, it can be driven as a switching power supply according to the output voltage. Since the modulated signal is binarized, the configuration is easy as an integrated circuit, and a small switching power supply can be provided.

As described above, the gate driver circuit 6 having a sufficient current and voltage capacity to drive the power switch element 7
Is fed back to the ΔΣ modulator 5 to greatly affect the input signal and reduce the distortion generated in the gate driver circuit 6. As shown in FIG.
Even when switching is performed by the high frequency of the power switch element 7, the phase margin is large and the control can be stabilized.

Although FIG. 8 particularly describes a step-down chopper, it is apparent that the same method can be applied to a step-up chopper and a polarity inversion chopper.

A switching signal generator according to a second aspect has at least one integrator 3 connected to the output of the adder 2 and has a quantizer 4 connected to at least one output of the integrator 3. Implement ΔΣ modulation.

Further, the former is provided with two or more integrators 3 connected in series to the output of the adder 2 or two or more integrators 3 connected in parallel to the output of the adder 2 so that the former is used for sampling. It is possible to increase the accuracy, and the latter can be provided with outputs in parallel, so that high accuracy,
It is possible to provide a multi-output switching power supply.

According to a third aspect of the present invention, there is provided a switching signal generator having a feedback path from the output of the gate driver circuit connected to the output of the quantizer to the input of the adder. Is necessary to correct the distortion generated in the gate driver circuit 6.

According to a fourth aspect of the present invention, there is provided a switching signal generator comprising a gate driver circuit for supplying a voltage and a current sufficient to drive the power switch element. With the output of 4, the output sufficient to drive the power switch element 7 cannot be obtained, and the signal to be fed back is necessary to sufficiently exhibit the effect.

According to a fifth aspect of the present invention, there is provided a switching signal generator comprising an attenuator in a feedback path from an output of the gate driver circuit to an input of the adder. Of the large-amplitude pulse signal to the input signal level of the ΔΣ modulator 5 and the signal to be fed back is required to be sufficiently effective.

[0037]

In the switching power supply using the ΔΣ modulator 5, the output of the gate driver circuit 6 is connected to the Δ５ modulator 5.
, The distortion in the gate driver circuit 6 can be reduced, the power switch element 7 can be driven, the phase margin is increased, and the control is stabilized. In particular, oscillation becomes difficult at a high switching frequency, and stable control can be provided. That is, it is possible to provide a switching power supply that does not easily oscillate even at a high switching frequency and supplies an output voltage corresponding to an input voltage.

Further, since the output of the power switch element is hardly affected by noise, especially when the power output is low, a switching loss is small and a high efficiency switching power supply can be supplied.

[0039]

[Brief description of the drawings]

FIG. 1 is a block diagram of an example showing an embodiment of the present invention.

FIG. 2 is a block diagram using a conventional PWM modulator.

FIG. 3 is a block diagram of a conventional ΔΣ modulator.

FIG. 4 is a DC transmission characteristic diagram comparing the feedback of the output of the gate driver circuit of the present invention with the output feedback of the conventional quantizer.

FIG. 5 is a block diagram using a conventional ΔΣ modulator.

FIG. 6 is a block diagram in which a conventional PWM modulator is applied to a step-down chopper power supply.

FIG. 7 is a block diagram in which a conventional ΔΣ modulator is applied to a step-down chopper power supply.

FIG. 8 is an embodiment of a ΔΣ modulation type step-down chopper of the present invention.

FIG. 9 is a Bode diagram showing gain (GAIN) and phase (PHASE).

[Explanation of symbols]

 1. Input signal 2. Adder 3. Integrator 4. Quantizer 5. ΔΣ modulator 6. Gate driver circuit 7. Power switch element 8. Output 9. Feedback 10. Frequency signal 11. Error amplifier 12. Diode 13 Capacitor 14. Inductance 15. Load 16. Resistance 17. Reference voltage 18. PWM (pulse width modulation) oscillator 19. Attenuator

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[Procedure amendment]

[Submission Date] February 25, 2002 (2002.2.2)
5)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

Claims (5)

[Claims] 1. A switching power supply for ΔΣ-modulating an analog signal or a multi-bit digital signal and switching in response to the modulated signal, comprising a gate driver circuit for a power switch element switching signal, wherein the gate driver output is a ΔΣ modulator. A switching signal generator characterized in that the switching signal is fed back to the switching signal generator. 2. The switching signal generator according to claim 1, wherein the ΔΣ modulator converts an input signal to an analog signal or a multi-bit digital signal, and has at least one integrator and at least one adder. A switching signal generator, wherein an output is connected to an integrator, and at least one of the outputs of the integrator is connected to a quantizer input. 3. The switching signal generator according to claim 1, further comprising a feedback path from an output of the gate driver circuit connected to an output of the quantizer to at least one input of the adder of the ΔΣ modulator. And a switching signal generator. 4. The switching signal generator according to claim 1, wherein the gate driver circuit receives the quantizer output signal and performs one of voltage amplification and current amplification sufficient to drive the power switch element, or A switching signal generator that performs both voltage amplification and current amplification sufficient to drive a power switch element. 5. The switching signal generator according to claim 1, wherein the feedback path includes an attenuator for adapting a large amplitude pulse signal of the gate driver circuit to a ΔΣ modulator input signal level. Signal generator.