TWI617122B - Ripple compensation circuit of power supply and compensating method thereof - Google Patents

Abstract

The present invention is a compensation method suitable for a ripple compensation circuit of a power supply. The power supply includes an LLC resonant conversion circuit, and the LLC resonant conversion circuit receives an input voltage and outputs an output voltage. The compensation method includes the steps of: (a) a reference voltage Subtracting with the output voltage to generate a first error signal; (b) boosting the low frequency gain of the first error signal with a digital filter to generate a second error signal; (c) first and second error signals Adding operation to generate a modulation error signal; (d) generating a compensation signal corresponding to the modulation error signal to control the LLC resonant conversion circuit to improve the low frequency gain of the LLC input voltage and improve the response of the voltage loop compensation circuit, so that the LLC The resonant converter circuit corresponds to an output that suppresses the output voltage of the low frequency ripple.

Description

Ripple compensation circuit suitable for power supply and compensation method thereof

The present invention relates to a ripple compensation circuit, and more particularly to a ripple compensation circuit and a compensation method suitable for a power supply.

The power supply is a very common electronic product in daily life, and almost all electrical devices have a power supply for supplying power to internal components or electronic components of the electrical device. Taking an AC/DC power supply as an example, it typically includes a power factor correction (PFC) circuit and an LLC resonant conversion circuit. Wherein, the power factor correction circuit receives an AC voltage, such as a commercial power, and performs power factor correction on the AC voltage to output a transient DC voltage. The LLC resonant converter circuit receives the transient DC voltage and converts the received transient DC voltage into an output DC voltage of a different voltage level in a resonant manner.

However, when using an AC/DC power supply, there is a low frequency (generally a ripple of frequency 90 Hz to 120 Hz) due to the received AC voltage, resulting in a transition DC voltage and LLC resonant conversion output by the power factor correction circuit. The output DC voltage output by the circuit also corresponds to the presence of low frequency ripple. These low frequency ripples not only cause unnecessary power loss, but also make the AC/DC power supply operate abnormally, and also generate noise and noise.

In the prior art, the method for suppressing low frequency ripple of an AC/DC power supply with an LLC resonant converter circuit mainly adopts an analog filtering method, that is, an analog filter circuit is added at an output end of the LLC resonant conversion circuit, such as RC. A filter circuit or an LC filter circuit filters out low frequency ripple in the output DC voltage output by the LLC resonant converter circuit. Although the analog filter circuit is used and the resistance, capacitance and inductance of the relevant components in the AC/DC power supply are calculated at the time of design, the low frequency ripple can be effectively suppressed to some extent. However, this method of adding an analog filter circuit increases the production cost of the AC/DC power supply and increases the application space requirement in the AC/DC power supply.

In order to solve the above problem of increasing the analog filter circuit, in many other prior documents, the method of increasing the low frequency gain of the voltage received at the input of the LLC resonant converter circuit is used to suppress the AC/DC power supply. In the low frequency ripple of the output voltage, the method directly multiplies the output voltage outputted by the LLC resonant converter circuit and the gain of the filter to generate a gain by increasing the low frequency gain of the output voltage of the LLC resonant converter circuit. The signal directly compensates the input voltage received by the LLC resonant converter circuit through the gain signal, thereby increasing the low frequency gain of the input voltage. Please refer to FIG. 1A and FIG. 1B , wherein FIG. 1A is a gain-frequency waveform diagram of a voltage received at an input end of an LLC resonant conversion circuit compensated by a gain signal in the prior art, and FIG. 1B is a corresponding figure. Figure 1A is a phase-frequency waveform diagram of the voltage received at the input of the LLC resonant converter circuit compensated by the gain signal. However, since the above method of increasing the low frequency gain of the input voltage of the LLC resonant converter circuit is generated by multiplying the output voltage of the LLC resonant converter circuit by the gain of the filter, the zero point and the pole point are changed, so if the zero point is used, The gain signal of the pole change directly compensates the input voltage of the LLC resonant converter circuit, which produces a significant phase impact. For example, the area indicated by A in Figure 1A represents the input voltage of the LLC resonant converter circuit compensated by the increased gain. The gain is increased at a frequency of about 100 Hz. However, it can be seen from the region indicated by A' in Fig. 1B that when the voltage gain is increased as in Fig. 1A, there is a phase impact of about 90 deg to about -90 deg, which is huge. The phase impact will cause instability of the AC/DC power supply.

Therefore, how to develop a ripple compensation circuit suitable for a power supply and a suitable compensation method for overcoming the above disadvantages is an urgent need.

The purpose of the present invention is to provide a ripple compensation circuit suitable for a power supply and a compensation method thereof, wherein the ripple compensation circuit can not only improve the low frequency gain of the voltage at the input end of the LLC resonant conversion circuit, but also suppress low frequency ripple. The phase impact can be reduced to maintain the stability of the power supply. What's more, the ripple compensation circuit in this case can reduce the use space inside the power supply and reduce the production cost.

In order to achieve the above object, a preferred embodiment of the present invention provides a ripple compensation circuit suitable for a power supply, wherein the power supply includes an LLC resonant conversion circuit, and an input terminal of the LLC resonant conversion circuit receives an input voltage. The output of the LLC resonant converter circuit is the output output voltage. The ripple compensation circuit includes a subtractor, a digital filter, an adder, and a voltage loop compensation circuit. The input end of the subtractor is connected to the output end of the LLC resonant conversion circuit, the subtractor receives the output voltage and the reference voltage, and subtracts the reference voltage from the output voltage to generate a first error signal. The input end of the digital filter is coupled to the output of the subtractor for receiving the first error signal and boosting the low frequency gain of the first error signal to produce a second error signal. The input end of the adder is connected to the output end of the subtractor and the output end of the digital filter, and the adder receives the first error signal and the second error signal, and adds the first error signal and the second error signal To generate a modulation error signal. The input end of the voltage loop compensation circuit is connected to the output end of the adder, the output end of the voltage loop compensation circuit is connected with the LLC resonant conversion circuit, and the voltage loop compensation circuit receives the modulation error signal, and according to the adjustment The variable error signal correspondingly generates a compensation signal to control the LLC resonant conversion circuit to increase the low frequency gain of the input voltage and improve the response of the voltage loop compensation circuit, so that the LLC resonant conversion circuit corresponding output suppresses the output voltage of the low frequency ripple.

Another embodiment of the present invention provides a compensation method suitable for a ripple compensation circuit of a power supply, wherein the power supply includes an LLC resonant conversion circuit, and an input end of the LLC resonant conversion circuit receives an input voltage, LLC resonant conversion The output of the circuit is the output output voltage. The compensation method of the present invention comprises the steps of: (a) subtracting a reference voltage from an output voltage to generate a first error signal; and (b) using a digital filter to boost a low frequency gain of the first error signal to generate a second error. a signal; (c) adding a first error signal and a second error signal to generate a modulated error signal; (d) generating a compensation signal corresponding to the modulated error signal to control the LLC resonant conversion circuit to increase the LLC input voltage The low frequency gain, and the output of the LLC resonant converter circuit suppresses the output voltage of the low frequency ripple.

Another aspect of the present invention provides a power supply, wherein the power supply includes an LLC resonant conversion circuit and a ripple compensation circuit. The input end of the LLC resonant converter circuit receives the input voltage, and the output of the LLC resonant converter circuit outputs the output voltage. The ripple compensation circuit includes a subtractor, a digital filter, an adder, and a voltage loop compensation circuit. The input end of the subtractor is connected to the output end of the LLC resonant conversion circuit, the subtractor receives the output voltage and the reference voltage, and subtracts the reference voltage from the output voltage to generate a first error signal. The input end of the digital filter is coupled to the output of the subtractor for receiving the first error signal and boosting the low frequency gain of the first error signal to produce a second error signal. The input end of the adder is connected to the output end of the subtractor and the output end of the digital filter, and the adder receives the first error signal and the second error signal, and adds the first error signal and the second error signal To generate a modulation error signal. The input end of the voltage loop compensation circuit is connected to the output end of the adder, the output end of the voltage loop compensation circuit is connected with the LLC resonant conversion circuit, and the voltage loop compensation circuit receives the modulation error signal, and according to the adjustment The variable error signal correspondingly generates a compensation signal to control the LLC resonant conversion circuit to increase the low frequency gain of the input voltage and improve the response of the voltage loop compensation circuit, so that the LLC resonant conversion circuit corresponding output suppresses the output voltage of the low frequency ripple.

Some exemplary embodiments embodying the features and advantages of the present invention are described in detail in the following description. It is to be understood that the present invention is capable of various modifications in the various aspects of the present invention, and the description and drawings are intended to be illustrative and not limiting.

Figure 2 is a circuit diagram of a ripple compensation circuit suitable for a power supply of the preferred embodiment of the present invention. As shown in FIG. 2, the ripple compensation circuit 2 of the present invention is applied to a power supply 1, wherein the power supply 1 can be, but not limited to, an AC/DC power supply, and the power supply 1 is An LLC resonant converter circuit 3 is included. The LLC resonant converter circuit 3 converts the received input voltage Vin into an output voltage Vout in a resonant manner to provide a load to the power supply 1 for electrical connection, such as an electrical device.

The ripple compensation circuit 2 includes a subtractor 21, a digital filter 22, an adder 23, and a voltage loop compensation circuit 24. The input end of the subtracter 21 is connected to the output end of the LLC resonant converter circuit 3, and the subtracter 21 receives the output voltage Vout of the LLC resonant converter circuit 3 and a reference voltage Vref, and subtracts the reference voltage Vref from the output voltage Vout. The operation is to generate the first error signal Ve according to the difference between the reference voltage Vref and the output voltage Vout.

The input end of the digital filter 22 is connected to the output end of the subtractor 21, and has a z-domain transfer function preset, and the digital filter 22 is configured to receive the first error signal Ve and use the z-domain transfer function to boost the first The low frequency gain of the error signal Ve, which in turn produces a second error signal Ve'. In some embodiments, the low frequency gain described above is a voltage gain between 90 Hz and 120 Hz.

Please refer to FIG. 3 and cooperate with FIG. 2, wherein FIG. 3 is an architectural diagram of the z-domain transfer function of the digital filter shown in FIG. As shown in the figure, the digital filter 22 of the present invention may be, but not limited to, an infinite impulse response filter (IIR filter), and the infinite impulse response filter is pre-configured with a z-domain transfer function. That is, the following formula (1): (1) In equation (1), H(z) is the z-domain transfer function, Ve is the first error signal, and Ve' is the second error signal, and a1, a2, b1, b2 are infinite impulse responses. Filter coefficient of the filter, a first-order delay unit, Two first-order delay units A second-order delay unit obtained by multiplication. To achieve the formula (1), it is generally implemented by the architecture diagram shown in FIG. 3, wherein the reference numeral 31 is an adder, and the infinite impulse response filter passes the first error signal Ve and the second error signal Ve'. Filter coefficients a1, a2, b1, b2, first order delay unit in Fig. 3 And the adder 31 performs an operation to obtain the z-domain transfer function H(z) of the present case. Moreover, adjusting the coefficients of a1 and a2 can adjust the position of the pole setting of the filter, and adjusting the coefficients of b1 and b2 can adjust the position of the zero point setting of the filter. By adjusting the value of the filter coefficient, it can be designed at different frequencies. Filters with different gain effects. For example, by adjusting the filter coefficients of the z-domain transfer function H(z), the digital filter 22 can achieve a voltage gain between 90Hz and 120Hz, but the transmission is different. The above plurality of filter coefficients can all be designed to improve the voltage gain effect of 90Hz-120Hz, and the adjustment of the filter coefficients is a common method used by those skilled in the art, so the manner of adjusting the filter coefficients is not repeated.

Referring again to FIG. 2, the input terminal of the adder 23 is connected to the output of the subtractor 21 and the output of the digital filter 22, and the adder 23 receives the first error signal Ve and the digital output from the subtractor 21. The second error signal Ve' output by the filter 22 adds the first error signal Ve and the second error signal Ve' to generate a modulation error signal Vg.

The input end of the voltage loop compensation circuit 24 is connected to the output end of the adder 23, the output end of the voltage loop compensation circuit 24 is connected to the LLC resonant conversion circuit 3, and the voltage loop compensation circuit 24 receives the adder 23. The modulated modulation error signal Vg is outputted according to the modulation error signal Vg to generate a compensation signal Sc to control the LLC resonant conversion circuit 3 to improve the low frequency gain of the input voltage Vin received by the LLC resonant conversion circuit 3 and to increase the voltage loop. The response of the circuit compensation circuit, thereby causing the LLC resonant converter circuit 3 to output the output voltage Vout that has suppressed the low frequency ripple due to the low frequency gain of the input voltage Vin has been increased.

Please refer to FIG. 2 and FIG. 4 at the same time, wherein FIG. 4 is a flowchart of the compensation method of the ripple compensation circuit shown in FIG. 2. As shown in Fig. 4, the compensation method of the ripple compensation circuit 2 of the present invention includes the following steps. First, step S1 is executed to receive the output voltage Vout of the LLC resonant converter circuit 3 and the reference voltage Vref, and the reference voltage Vref and the output voltage Vout are subtracted to generate a first error signal Ve. Next, in step S2, the digital filter 22 receives the first error signal Ve, and uses the z-domain transfer function preset to the digital filter 22 to boost the low-frequency gain of the first error signal Ve, thereby generating the second error signal Ve'. . Then, in step S3, the adder 23 receives the first error signal Ve and the second error signal Ve', and adds the first error signal Ve and the second error signal Ve' to generate the modulated error signal Vg. Finally, in step S4, the voltage loop compensation circuit 24 receives the modulation error signal Vg, and generates a compensation signal Sc according to the modulation error signal Vg to control the LLC resonant conversion circuit 3 to improve the input voltage Vin of the LLC resonant conversion circuit 3. The low frequency gain causes the LLC resonant converter circuit 3 to output an output voltage Vout that suppresses the low frequency ripple.

Please also refer to Figure 2 and Figure 5A-5C. Figure 5A is the voltage-time series simulation result of the first error signal shown in Figure 2 of the case. Figure 5B is the figure shown in Figure 2 of this case. The voltage-time series simulation result diagram of the second error signal, and the 5C figure is the voltage-time series simulation result diagram of the modulation error signal shown in Fig. 2 of the present invention. As can be seen from the 5A-5C figure, since the digital filter 22 boosts the low frequency gain of the first error signal Ve (compared by the 5A and 5B pictures), the first error signal Ve and the second are transmitted. The modulation error signal Vg generated after the addition of the error signal Ve' suppresses the low frequency ripple accompanying the error signal Ve.

Please refer to FIG. 6A and FIG. 6B. FIG. 6A is a voltage-time series simulation result diagram of the low-frequency ripple of the output voltage of the LLC resonant conversion circuit without using the ripple compensation circuit of the present invention, and FIG. 6B is a diagram A voltage-time series simulation result diagram of the low-frequency ripple of the output voltage outputted by the LLC resonant converter circuit of the ripple compensation circuit of the present invention. It can be clearly seen from the pictures of FIGS. 6A and 6B that when the ripple compensation circuit 2 of the present invention is not used, the peak-to-peak voltage value of the low-frequency ripple of the output voltage outputted by the LLC resonant conversion circuit is 469 mV, and if the pattern is used, In the wave compensation circuit 2, the peak-to-peak voltage value of the low-frequency ripple of the LLC resonant converter circuit 3 can be reduced to 259 mV, and it is apparent that the ripple compensation circuit 2 of the present invention does have the effect of suppressing ripple.

Please refer to FIG. 7A and FIG. 7B. FIG. 7A is an amplitude-frequency pseudo-result diagram of the low-frequency ripple of the output voltage of the LLC resonant converter circuit without the ripple compensation circuit of the present invention, and FIG. 7B is a diagram. The amplitude-frequency simulation result graph of the low-frequency ripple of the output voltage outputted by the LLC resonant converter circuit of the ripple compensation circuit of the present invention. It can be clearly seen from the figures 7A and 7B that when the ripple compensation circuit 2 of the present invention is not used, the low frequency ripple of the output voltage outputted by the LLC resonant conversion circuit is located at an amplitude of about -19 dB at 110 Hz (as indicated by the area of B). However, if the ripple compensation circuit 2 of the present invention is used, the amplitude of the low-frequency ripple of the output voltage outputted by the LLC resonant conversion circuit 3 is reduced to -40.6 dB at the 110 Hz (as indicated by the area of B'), thereby being apparent It is known that the ripple compensation circuit 2 of the present invention does have the effect of suppressing ripple.

Please refer to FIG. 8A and FIG. 8B. FIG. 8A is a gain-frequency waveform diagram of the input voltage of the LLC resonant converter circuit compensated by the ripple compensation circuit of the present invention, and FIG. 8B is corresponding to FIG. 8A. The phase-frequency waveform diagram of the input voltage of the LLC resonant converter circuit compensated by the ripple compensation circuit of the present invention. As shown in the figure, compared with the prior art, since the modulation error signal is directly multiplied by the output voltage outputted by the LLC resonant conversion circuit and the gain of the filter, the modulated error signal is directly used for compensation. The input voltage of the LLC resonant conversion circuit causes a phase impact, since the low frequency gain of the first error signal Ve is first boosted by the digital filter 22 to generate the second error signal Ve', and the second error signal is utilized. Ve' is added to the first error signal Ve to generate the modulated error signal Vg, and finally the modulated voltage Vg is used to compensate the input voltage Vin of the LLC resonant converter circuit 3, so that the pole of the modulated error signal Vg is The zero point impact can be reduced, so that the phase impact of the input voltage Vin of the LLC resonant converter circuit 3 compensated by the modulation error signal Vg is also reduced. That is, as shown in Figs. 8A and 8B, wherein the region indicated by C in Fig. 8A represents the input voltage Vin of the LLC resonant converter circuit 3 compensated by the modulated error signal Vg, which is increased at a frequency of about 100 Hz. The gain, while the area indicated by C' in Fig. 8B represents the input voltage Vin of the LLC resonant converter circuit 3 compensated by the modulated error signal Vg, while increasing the gain at a frequency of about 100 Hz, there is about 15 deg. With a phase impact of about -15 deg, it can be proved that the ripple compensation circuit 2 of the present invention can reduce the phase impact while improving the low frequency gain, compared with the conventional increase of gain and the phase impact of about 90 deg to about -90 deg. Therefore, the ripple compensation circuit 2 of the present invention can maintain the stability of the power supply 1 while suppressing the low frequency ripple.

In some embodiments, the ripple compensation circuit 2 can be integrated into a microcontroller (not shown) of the power supply 1 , wherein the microcontroller is electrically connected to the LLC resonant conversion circuit 3 , mainly for controlling the LLC resonant conversion. The operation of the circuit 3, and when the ripple compensation circuit 2 of the present invention is integrated in the microcontroller, the above compensation method can be performed in a digital manner by the microcontroller, thereby compensating the low frequency of the input voltage Vin of the LLC resonant conversion circuit 3 Gain, in this way, the power supply 1 of the present case can directly suppress the low frequency ripple of the LLC resonant conversion circuit 3 through the microcontroller, so that it is not necessary to add additional hardware components as the conventional power supply, for example, RC filtering The circuit or the LC filter circuit, etc., the power supply 1 of the present invention can reduce the use of internal space and reduce the production cost. Moreover, since the storage space and computing resources of the microcontroller are limited, the digital filter 22 of the present invention is mainly composed of a digital filter 22 which is simple, efficient and low-order, such as an infinite impulse response filter. Therefore, a lower order can be used to achieve higher frequency selectivity, so that fewer memory cells are used, which does not increase the burden on the storage space and computing resources of the microcontroller.

In summary, the present invention provides a ripple compensation circuit suitable for a power supply and a compensation method thereof, wherein the ripple compensation circuit of the present invention first transmits a low frequency gain of the first error signal through a digital filter to generate The second error signal is further added by using the second error signal and the first error signal to generate a modulated error signal, and then the input voltage of the LLC resonant converter circuit is compensated by the modulated error signal, thereby adjusting the pole of the error signal The zero point impact can be reduced, so that the phase impact of the input voltage of the LLC resonant converter circuit compensated by the modulation error signal is also reduced. Therefore, the present invention can suppress the low frequency ripple while maintaining the stability of the power supply. degree.

This case has been modified by people who are familiar with the technology, but it is not intended to be protected by the scope of the patent application.

A, A', B, B', C, C': labeling area 1: power supply 2: ripple compensation circuit 3: LLC resonance conversion circuit 21: subtractor 22: digital filter 23, 31: adder 24 : voltage loop compensation circuit Ve: first error signal Ve': second error signal Vin: input voltage Vout: output voltage Vref: reference voltage Vg: modulation error signal Sc: compensation signals a1, a2, b1, b2: filtering Coefficient : first order delay unit

Figure 1A is a gain-frequency waveform diagram of the voltage received at the input of the LLC resonant converter circuit compensated by the gain signal in the prior art. Fig. 1B is a phase-frequency waveform diagram of the voltage received at the input end of the LLC resonant converter circuit compensated by the gain signal corresponding to Fig. 1A. Figure 2 is a circuit diagram of a ripple compensation circuit suitable for a power supply of the preferred embodiment of the present invention. Figure 3 is an architectural diagram of the z-domain transfer function of the digital filter shown in Figure 2. Fig. 4 is a flow chart showing a method of compensating the ripple compensation circuit shown in Fig. 2. Figure 5A is a voltage-time series simulation result diagram of the first error signal shown in Fig. 2 of the present invention. Figure 5B is a voltage-time series simulation result diagram of the second error signal shown in Fig. 2 of the present invention. Figure 5C is a voltage-time series simulation result diagram of the modulation error signal shown in Fig. 2 of the present invention. Fig. 6A is a graph showing the voltage-time series simulation results of the low-frequency ripple of the output voltage output from the LLC resonant converter circuit of the ripple compensation circuit of the present invention. Fig. 6B is a voltage-time series simulation result diagram of the low frequency ripple of the output voltage outputted by the LLC resonant converter circuit of the ripple compensation circuit of the present invention. Fig. 7A is an amplitude-frequency pseudo-result diagram of the low-frequency ripple of the output voltage outputted by the LLC resonant converter circuit without using the ripple compensation circuit of the present invention. Fig. 7B is a graph showing the amplitude-frequency simulation result of the low-frequency ripple of the output voltage outputted by the LLC resonant converter circuit of the ripple compensation circuit of the present invention. Fig. 8A is a gain-frequency waveform diagram of the input voltage of the LLC resonant converter circuit compensated by the ripple compensation circuit of the present invention. Fig. 8B is a phase-frequency waveform diagram of the input voltage of the LLC resonant converter circuit compensated by the ripple compensation circuit of the present invention corresponding to Fig. 8A.

Claims (15)

A ripple compensation circuit suitable for a power supply, wherein the power supply comprises an LLC resonant conversion circuit, an input of the LLC resonant conversion circuit receives an input voltage, and an output of the LLC resonant conversion circuit Outputting an output voltage, the ripple compensation circuit includes: a subtractor, an input end of the subtractor being connected to the output end of the LLC resonant conversion circuit, the subtractor receiving the output voltage and a reference voltage And subtracting the reference voltage from the output voltage to generate a first error signal; a digital filter, wherein one input end of the digital filter is connected to one of the output terminals of the subtractor for receiving The first error signal increases the low frequency gain of the first error signal to generate a second error signal; an adder, the input end of the adder and the output of the subtractor and the digital filter One of the output terminals is connected, the adder receives the first error signal and the second error signal, and the first error signal and the second error The signal is added to generate a modulation error signal; and a voltage loop compensation circuit, wherein an input end of the voltage loop compensation circuit is connected to an output end of the adder, and the voltage loop compensation circuit The output end is connected to the LLC resonant conversion circuit, and the voltage loop compensation circuit receives the modulated error signal, and correspondingly generates a compensation signal according to the modulated error signal to control the LLC resonant conversion circuit to improve the input. The low frequency gain of the voltage and the response of the voltage loop compensation circuit are increased such that the LLC resonant converter circuit outputs an output voltage that suppresses excessive low frequency ripple. The ripple compensation circuit of claim 1, wherein the power supply further has a microcontroller connected to the LLC resonant conversion circuit for controlling the LLC resonant conversion circuit. Operation. The ripple compensation circuit of claim 2, wherein the ripple compensation circuit is integrated in the microcontroller. The ripple compensation circuit of claim 1, wherein the digital filter is an infinite impulse response filter. The ripple compensation circuit of claim 4, wherein the infinite impulse response filter is preset with a z-domain transfer function for boosting a low-frequency gain of the first error signal, the z The domain transfer function is: , wherein a1, a2, b1, and b2 are filter coefficients of the infinite impulse response filter, Is a first-order delay unit, It is a second-order delay unit. The ripple compensation circuit of claim 1, wherein the low frequency gain of the first error signal boosted by the digital filter is a voltage gain between 90 Hz and 120 Hz. A compensation method is applicable to a ripple compensation circuit of a power supply, wherein the power supply comprises an LLC resonant conversion circuit, and an input end of the LLC resonant conversion circuit receives an input voltage, and the LLC resonant conversion circuit An output terminal outputs an output voltage, and the compensation method comprises the steps of: (a) subtracting a reference voltage from the output voltage to generate a first error signal; (b) using a digital filter to boost the first a low frequency gain of the error signal, thereby generating a second error signal; (c) adding the first error signal and the second error signal to generate a modulated error signal; (d) according to the modulation error The signal correspondingly generates a compensation signal to control the LLC resonant conversion circuit to increase the low frequency gain of the LLC input voltage, so that the LLC resonant conversion circuit correspondingly outputs the output voltage that suppresses the low frequency ripple. The compensation method of claim 7, wherein the digital filter is an infinite impulse response filter. The compensation method of claim 8, wherein the infinite impulse response filter is preset with a z-domain transfer function for boosting a low-frequency gain of the first error signal, the z-domain transfer The function is: , wherein a1, a2, b1, and b2 are filter coefficients of the infinite impulse response filter, Is a first-order delay unit, It is a second-order delay unit. The compensation method of claim 7, wherein the low frequency gain of the first error signal boosted by the digital filter is a voltage gain between 90 Hz and 120 Hz. A power supply comprising: an LLC resonant conversion circuit, an input of the LLC resonant conversion circuit receives an input voltage, an output of the LLC resonant conversion circuit outputs an output voltage; and a ripple compensation circuit, The method includes: a subtractor, an input end of the subtractor is connected to the output end of the LLC resonant conversion circuit, the subtractor receives the output voltage and a reference voltage, and the reference voltage and the output voltage are Subtracting to generate a first error signal; a digital filter having an input terminal coupled to an output of the subtractor for receiving the first error signal and boosting the first a low frequency gain of the error signal, thereby generating a second error signal; an adder having an input terminal coupled to the output of the subtractor and an output of the digital filter, the adder system Receiving the first error signal and the second error signal, and adding the first error signal and the second error signal to generate a tone An error signal; and a voltage loop compensation circuit, wherein an input end of the voltage loop compensation circuit is connected to an output end of the adder, and an output end of the voltage loop compensation circuit is coupled to the LLC resonant conversion circuit Connecting, the voltage loop compensation circuit receives the modulation error signal, and correspondingly generates a compensation signal according to the modulation error signal to control the LLC resonant conversion circuit to improve the low frequency gain of the input voltage and improve voltage loop compensation. The response of the circuit causes the LLC resonant converter circuit to reject the output voltage of the low frequency ripple corresponding to the output. The power supply device of claim 11, further comprising a microcontroller coupled to the LLC resonant conversion circuit for controlling operation of the LLC resonant conversion circuit, wherein the pattern The wave compensation circuit is integrated in the microcontroller. The power supply of claim 11, wherein the digital filter is an infinite impulse response filter. The power supply device of claim 13, wherein the infinite impulse response filter is preset with a z-domain transfer function for boosting a low-frequency gain of the first error signal, the z-domain The transfer function is: , wherein a1, a2, b1, and b2 are filter coefficients of the infinite impulse response filter, Is a first-order delay unit, It is a second-order delay unit. The power supply of claim 11, wherein the low frequency gain of the first error signal boosted by the digital filter is a voltage gain between 90 Hz and 120 Hz.