CN1114258C - Digital switch converter with quantization error compensation function - Google Patents

Abstract

The present invention relates to a digital switch converter with a quantization error compensatory function, which comprises a power switch, an attenuator, an A/D converter, an adder, an adjustor, a switch controller, a driver and a compensating controller, wherein the compensating controller is provided with a first adder, a second adder, a quantizer and a delayer. A time value of a switch pulse is compensated by storing and accumulating the mantissa of the temporal quantization errors of the switch controller, and thus, the digital pulse control precision of the switch converter can be obviously enhanced.

Description

Digital switch converter with quantization error compensation function

The present invention relates to digital switch converter.

All kinds of power electronics power supplys (comprising AC/DC power supply, DC/DC power supply, inverter etc.) are widely used on the various electrified equipment, and switch converters wherein then is the core part of this class power supply.Switch converters also is the core component of switch power amplifier.Switch converters is realized the control to electric energy by the frequent power semiconductor switches that switches wherein.In recent years, along with the development of digital signal processing chip (DSP), microprocessor chip (MPU), microcomputer (MCU), programmable gate array (PLA) technical merit, digital Control Technology begins to be applied in switch converters.The control mode of common employing has pulse width modulation (PWM) control, decide the pulsewidth variable frequency control, decide that frequency displacement is controlled mutually etc., wherein controls comparatively typical again with PWM.Digital switch converter with present employing is the example (see figure 1), and it generally includes power switch, attenuator, the A/D converter that analog signal conversion can be become digital signal, adjuster (being generally ratio-integration-differential regulator), on-off controller (containing counter usually) and driver module.The voltage (electric current) of output reduces amplitude by attenuator, converts digital quantity to through A/D.The output signal of A/D and specified rate V _fRelatively produce error signal by adder, handle by adjuster.The output signal of adjuster is sent into on-off controller, produces the switching pulse conditioning signal thus.At last, by the power switch of driver module control change device, thereby influence the output V of converter _oIn said process, the signal of sending into on-off controller is a digital quantity, and the resolution of output switching pulse width then depends on the control word length of on-off controller.Usually, the output resolution ratio of adjuster can reach more than the 16Bits, far above the word length of counter in the on-off controller.The quantization error of pulse duration shows as the truncated error of controller output signal.Switch converters with the 20kHz that adopts the PWM control mode is an example, and its cycle is 50 μ s, is the PWM resolution that realizes 16Bits, and the clock frequency of counter must reach 2 ¹⁶* 20 * 10 ³KHz=1.31GHz.And be applied to the DSP of switch converters and general its clock frequency of MPU at present only about 5～50MHz, very far away apart from above-mentioned requirements.Converter is higher to the clock frequency meeting of requirement of digitial controller when the switching frequency of PWM improves.For example adopting a clock frequency is the DSP of 20MHz, and when switching frequency was 50kHz, the resolution of its PWM only was 400 (the control word length is lower than 9Bits).There is a big difference for realizing high-precision control requirement for this.More seriously, quantization error will cause the switch converters control procedure limit cycles oscillations to occur, and limit cycles oscillations more can be amplified manyfold with the output error of switch converters.

Purpose of the present invention is intended to improve the digitlization pulse control precision of digital switch converter, proposes a kind of digital switch converter with quantization error compensation function.

Digital switch converter with quantization error compensation function of the present invention, be in existing digital switch converter, to set up compensating controller and constitute, it comprises power switch, attenuator, A/D converter, adder, adjuster, on-off controller and driver, it is characterized in that between adjuster and on-off controller, inserting compensating controller, this compensating controller comprises first adder, second adder, quantizer and delayer, the output of an input termination adjuster of first adder, the output of another input termination delayer, the output of first adder inputs to quantizer and second adder respectively, the output of quantizer divides two the tunnel, the one road inputs to second adder, another road links to each other with the input of on-off controller, the input of the output termination delayer of second adder.

Delayer effect in the compensating controller is with switch periods of data delay, and its function available programs beat is realized, also can be realized by hardware, and quantizer is one to have and on-off controller control word appearance memory together.

Further specify the present invention below in conjunction with accompanying drawing.

Fig. 1 is existing digital switch converter block diagram;

Fig. 2 is that the present invention constitutes block diagram;

Fig. 3 is a kind of instantiation of the present invention;

Fig. 4 is the dsp chip schematic diagram that is used for Fig. 3 example.

With reference to Fig. 1, digital switch converter with quantization error compensation function of the present invention comprises power switch 1, attenuator 2, A/D converter 3, adder 4, adjuster 5, on-off controller 6 and driver 7, it is characterized in that between adjuster 5 and on-off controller 6, inserting compensating controller 8, this compensating controller comprises first adder 9, second adder 10, quantizer 11 and delayer 12, the output of an input termination adjuster 5 of first adder 9, the output of another input termination delayer 12, the output of first adder inputs to quantizer 11 and second adder 10 respectively, the output of quantizer 11 divides two the tunnel, the one road inputs to second adder 10, another road links to each other with the input of on-off controller 6, the input of the output termination delayer 12 of second adder 10.

Usually, on-off controller 6, compensating controller 8, adjuster 5, adder 4 and A/D converter 3 can be integrated on a slice chip specially, maybe can adopt DSP or integrated digital signal processing chips such as MPU or MCU or PLA.

During work, the voltage of output (electric current) converts digital quantity to through A/D converter 3, the output signal of A/D and specified rate V by attenuator 2 reduction amplitudes _fRelatively produce error signal by adder 4, handle by adjuster 5 and to send into compensating controller 8, switch converter switches switching instant is done to quantize compensation, switching pulse signal through quantization error compensation removes the power switch 1 of control change device through on-off controller 6, driver 7, thereby influences the output V of converter _o

If x _nBe the input variable of compensating controller, y _nBe output variable, wherein the leftover bits and pieces of each variable is designated as the sequential label.y _n ^*Be the truncation part that is sent to the on-off controller data, and y _N-1 ^*Then be the y of a switch periods of time-delay _n ^*, y _N-1 ^*Meaning be constantly truncation partly to be kept.Meanwhile, compensating controller output variable y _nIt is integer part by the error sum of adjuster output variable and last truncation.The function of compensating controller is:

1) when input variable does not comprise mantissa, y _N-1 ^*To remain unchanged;

When 2) not producing carry when the mantissa of input variable and the addition of last mantissa, mantissa is integrated in each switch periods;

When 3) producing carry when the mantissa of input variable and the addition of last mantissa, integer part is removed the truncated error that is used for compensating controller, and remaining mantissa is used for calculating next time.

4) y of mantissa _n ^*Determine by the input variable of quantizer and the difference of output variable, relevant with the quantization function of selecting.Above-mentioned statement can be replenished expression with following formula: $y_n^{*}=x_n+y_{n-1}^{*}-y_n---\left(1\right)$ $y_n=\mathrm{Trunc}(x_n+y_{n-1}^{*})---\left(2\right)$ Trunc is a quantization function in the formula 2, and effect is the integer part of getting variable.Utilize the quantization error that this compensating controller can compensating switch converter switching instant.

The rounding of quantization function can be adopted the tail method of abandoning (being that mantissa casts out) usually or be rounded up or advance a method (promptly advancing as long as mantissa is promptly arranged).

Fig. 3 is an instantiation of the present invention, and the top of Fig. 3 is to have capacitor C _i, C ₀Inductance L, diode D, the step-up switching power supply converter of power semiconductor main switch S, the below of Fig. 3 is the digit pulse control section, driver in this example adopts grid electrode drive module, and it links to each other with power semiconductor main switch S grid, and on-off controller adopts numerical control PWM module, adjuster is the PID unit, the attenuator resitstance voltage divider that links to each other with the supply convertor output, A/D are digital to analog converter, V _fThen be the given magnitude of voltage of digital form, the structure of compensating controller is identical with Fig. 2, wherein quantizer be one have and on-off controller control word appearance with memory, delayer is with the program beat or realized by hardware.It is the DSP integrated digital signal processing chip of TMS320F240 that numerical control PWM, compensating controller, PID, adder and A/D wherein also can adopt model as shown in Figure 4.The built-in CPU of dsp chip (central processing unit), timer, and hardware components such as A/D, PWM, by bus communication, program and constant are placed in the read-only memory (ROM) between the module, and variable is placed in the random asccess memory (RAM).Wherein, PID and compensate function are to utilize the program of DSP to realize.This digit pulse control device can be realized control output voltage by the switch control to the power semiconductor main switch.Test shows, adopts the present invention can make the caused limit loop voltag fluctuation of quantization error successfully be cut down 90%.

The present invention stores, accumulates by the mantissa to the digitlization pulse control unit quantization error in time in the switch converters, paired pulses is worth constantly and compensates in view of the above, thereby can reduce the caused departure of digital quantization effectively, significantly improve the control precision of switch converters.The present invention can be used for the burst length variable (for example pulse duration) of switch converters and regulate, can be under the situation that does not improve clock frequency, promote effective control word length of impulse controller, the resolution that rank are entered in refinement, the present invention helps to realize digitized accurate control on all kinds of switch converters, this exploitation and dissemination for the digital control technology of high frequency switch power converter is particularly important.

The present invention is not limited only to compensate the truncated error of PWM, can also the pulse quantization error of the switch converters that adopts other control mode be compensated.For example, for frequency conversion decide pulse width control, the digital control type switch converters of scheme such as decide that frequency displacement is controlled mutually, all can adopt the present invention to compensate its pulse controlled truncated error.

Claims (4)

1. the digital switch converter that has quantization error compensation function, comprise power switch [1], attenuator [2], A/D converter [3], adder [4], adjuster [5], on-off controller [6] and driver [7], it is characterized in that between adjuster [5] and on-off controller [6], inserting compensating controller [8], this compensating controller comprises first adder [9], second adder [10], quantizer [11] and delayer [12], the output of an input termination adjuster [5] of first adder [9], the output of another input termination delayer [12], the output of first adder inputs to quantizer [11] and second adder [10] respectively, the output of quantizer [11] divides two the tunnel, the one road inputs to second adder [10], another road links to each other with the input of on-off controller [6], the input of the output termination delayer [12] of second adder [10].

2. by the described digital switch converter of claim 1, it is characterized in that said quantizer [11] is one and has and on-off controller control word appearance memory together.

3. by the described digital switch converter of claim 1, it is characterized in that said on-off controller [6], compensating controller [8], adjuster [5], adder [4] and A/D converter [3] are digital signal processing chip or microprocessor chip or microcomputer or programmable gate array integrated digital signal processing chip.

4. by the described digital switch converter of claim 1, it is characterized in that said on-off controller [6], compensating controller [8], adjuster [5], adder [4] and A/D converter [3] are integrated on a slice chip specially.

Images