JP5709263B2 - Charger - Google Patents

Description

  The present invention relates to a charging device for charging a battery.

Generally, a charging device rectifies and smoothes an AC voltage supplied from a commercial AC power source to generate a DC input voltage, and switches the DC input voltage with at least one switching element to a desired DC output voltage. A DC / DC converter unit for conversion, and the battery is charged with a DC output voltage obtained by the DC / DC converter unit.
Here, the rectifying / smoothing unit is generally composed of a full-wave rectifying circuit including a diode bridge and a smoothing capacitor. The rectifying / smoothing unit may further include a power factor correction circuit (PFC circuit). The DC / DC converter section is generally composed of a transformer, a full-wave rectifier circuit, and an LC filter in addition to the switching element.

  Among such charging devices, in particular, regarding a vehicle-mounted charging device mounted on an electric vehicle or a hybrid vehicle, in recent years, there has been an increasing demand for downsizing. For this reason, it is preferable that the smoothing capacitor which comprises a rectification | straightening smoothing part has as small an electrostatic capacitance as possible.

  However, if the capacitance of the smoothing capacitor is reduced, the ripple amount at the DC input voltage increases when the output current (battery charging current) is relatively large. ”) Will increase. If the amount of ripple in the DC output voltage increases excessively, the amount of heat generated by the battery increases, leading to a reduction in battery life.

Therefore, for example, Non-Patent Document 1 proposes a control method intended to cancel output ripple by adding a ripple amount at a DC input voltage to a control amount of a switching element by feedforward.
As shown in FIG. 5, in the switching power supply device 200 to which this control method is applied, the feedback control amount FB for reducing the deviation between the DC output voltage V _out and the target charging voltage, and the DC input voltage V V by the ripple amount extraction unit. by adding the ripple amount R extracted from _in, the duty control amount S _duty for commanding the duty ratio of the switching element 202 is generated.

Jung-Bum Kim, Nam-Ju Park, Dong-Yun Lee, Dong-Seok Hyun, "A Control Technique for 120Hz DC Output Ripple-Voltage Suppression Using BIFRED with a Small-Sized Energy Storage Capacitor", Journal of Power Electronics, Vol 5, No. 3, July 2005, pp.190-197

By the way, in the above-described conventional switching power supply apparatus 200, when the turns ratio of the transformer included in the DC / DC converter unit is 1: N and the duty ratio of the switching element 202 commanded by the duty control amount S _duty is Duty _sw , The formula holds.

V _out = V _in × Duty _sw × N (1)

As apparent from the above equation, the DC output voltage V _out is, the DC input voltage (voltage between the terminals of the smoothing capacitor) V _in, so is represented by the product of the duty ratio Duty _sw, and the turns ratio N, the DC output voltage V the _out, will include output ripple of quantity proportional to the ripple of the DC input voltage V _in.

For this reason, in the switching power supply apparatus 200 to which the conventional control method is applied, the feedback control amount FB becomes unstable due to the influence of the output ripple, and therefore, the duty control amount S _duty that can sufficiently cancel the output ripple is generated. It was difficult.
Further, the conventional switching power supply apparatus 200 has a problem that the processing load for the filter calculation increases when the ripple amount extraction unit 201 is configured by a digital filter.

  The present invention has been made in view of the above circumstances, and the problem is that the output ripple can be sufficiently reduced even when a smoothing capacitor having a relatively small capacitance is used. In addition, an object of the present invention is to provide a charging device that can keep processing load low.

In order to solve the above-described problems, a charging device according to the present invention includes a rectifying / smoothing unit that rectifies and smoothes an alternating voltage to generate a direct-current input voltage, and a direct-current output by switching the direct-current input voltage with at least one switching element. a DC / DC converter unit for converting into voltage, and a control unit for controlling the duty ratio of the switching element, a charging device for charging a battery with the DC output voltage, at the timing t ₀ when the polarity is reversed for alternating voltage The controller further includes a zero cross detection unit that outputs a synchronization signal, and the control unit is configured to calculate α × cos (2πf _{r r} based on the ripple rate storage unit in which the expected ripple rate α is stored in advance and the synchronization signal and the ripple rate α. × t) (provided that, f _r contains a term of the elapsed time) from the ripple frequency, t is t _0, a ripple amount calculating unit for obtaining the ripple amount of the DC input voltage, full Characterized by have a duty ratio calculation unit for calculating a duty ratio of the switching element by dividing the feedback control amount obtained by the readback control ripple amount.

In this configuration, the duty ratio of the switching element is controlled based on a value calculated by dividing the feedback control amount by the ripple amount at the DC input voltage. Further, the DC output voltage supplied to the battery is proportional to the product of the duty ratio of the switching element and the DC input voltage, as shown in the above equation (1).
Therefore, according to this configuration, by multiplying the DC input voltage by the duty ratio proportional to the reciprocal of the ripple amount in the DC input voltage, even if the DC input voltage includes ripples, the output A DC output voltage that does not include ripples can be obtained.

  In addition, the structure for calculating a ripple amount can consider the 1st-3rd structure shown below, for example. According to these configurations, since the amount of ripple can be obtained only by performing a relatively simple calculation using the ripple rate α stored in advance in the ripple rate storage unit, the processing load can be reduced.

[First configuration]
When the charging device further includes an output current detection unit that detects a current value of the output current flowing through the battery, a plurality of ripple rates α corresponding to the current value of the output current are stored in the ripple rate storage unit in advance. Just keep it.
According to this configuration, the ripple amount can be obtained using the ripple rate α corresponding to the current value of the output current.

[Second configuration]
The charging device further includes a voltage detection unit that detects the voltage value of the DC output voltage, and the control unit receives the charging power command value, and the charging power command value and the detected DC output voltage voltage value And a target charging current calculation unit that calculates a target charging current value based on the above, a plurality of ripple rates α corresponding to the target charging current value may be stored in the ripple rate storage unit in advance. .
According to this configuration, the ripple amount can be obtained using the ripple rate α corresponding to the target charging current value.

[Third configuration]
When the charging device further includes a housing that houses at least the DC / DC converter unit and a temperature detection unit that detects the temperature in the housing, the ripple rate α corresponding to the temperature in the housing is determined as the ripple rate. What is necessary is just to store beforehand in a storage part.
According to this configuration, the ripple amount can be obtained using the ripple rate α corresponding to the temperature in the housing.

  According to the present invention, even when a smoothing capacitor having a relatively small capacitance is used, it is possible to provide a charging device that can suitably reduce output ripple and suppress processing load to a low level. .

It is a block diagram of the charging device which concerns on one Embodiment of this invention. It is a figure related to the DC / DC converter part with which the charging device of FIG. 1 was equipped, Comprising: (A) is a circuit diagram which shows a specific example, (B) is a timing chart for demonstrating operation | movement. It is a block diagram of the control part with which the charging device of FIG. 1 was equipped, and its peripheral part. 3 is a timing chart for explaining the operation of the charging device of FIG. 1. It is a block diagram of the switching power supply device to which the conventional control method is applied.

  Hereinafter, a preferred embodiment of a charging device according to the present invention will be described with reference to the accompanying drawings. In the following, an in-vehicle charging device mounted on an electric vehicle or a hybrid vehicle will be described as an example, but the present invention is also applicable to a charging device used in other fields.

[First Embodiment]
FIG. 1 is a block diagram of a charging device 1 according to the first embodiment of the present invention.
As shown in the drawing, the charging device 1, a commercial AC power source (AC100V, 50Hz / 60Hz) DC output voltage alternating-current voltage supplied to be supplied to the battery 101 such as a lithium-ion battery from an AC power source 100, such as V _out And mainly includes a rectifying / smoothing unit 2, a DC / DC converter unit 3, a control unit 4, and various sensors 5-11.

  The rectifying / smoothing unit 2 includes an AC filter unit 21, a protection unit 22, a rectifying unit 23, a power factor improving unit 24, and a smoothing capacitor 25. Among them, the AC filter unit 21 removes AC voltage noise, and the protection unit 22 protects the subsequent circuits from surges and inrush currents. The rectification unit 23 is formed of a diode bridge, and full-wave rectifies the AC voltage that has passed through the protection unit 22. The smoothing capacitor 25 smoothes the alternating voltage after full-wave rectification and turns it into direct current. The power factor improvement unit 24 improves the power factor by correcting the waveform.

According to the rectifying and smoothing portion 2, it is possible to generate a DC input voltage V _in the alternating voltage rectified and smoothed to. The generated DC input voltage V _in becomes an input voltage of the DC / DC converter unit 3.
Note that the rectifying / smoothing unit 2 only needs to include at least the rectifying unit 23 and the smoothing capacitor 25, and the AC filter unit 21, the protection unit 22, and the power factor improving unit 24 may be provided as necessary.

DC input voltage V _in is the average value V _ave, the amplitude of one side of the ripple V _Ripplestart, when the ripple frequency is f _r, can be expressed by the following equation.

V _in = V _ave −V _ripple × cos (2πf _r × t)
_{= V ave × {1-V} ripple / V ave × cos (2πf r × t)}
_{= V ave × {1-α} × cos (2πf r × t)} ··· (2)

Here, α is a ripple rate.
The ripple frequency _fr is twice the frequency f of the AC voltage supplied from the AC power supply 100. The time t is the elapsed time from the timing at which the polarity of the AC voltage is inverted.
Thus, the DC input voltage V _in, as shown in FIG. 4, shows the minimum value of the "V _ave -V _ripple" at the timing when the polarity of the AC voltage is inverted, "V _ave + V at the timing when the AC voltage reaches its peak The maximum value of “ _ripple ”.

As shown in FIG. 2A, the DC / DC converter unit 3 is a full bridge type DC / DC converter including a bridge circuit unit 31, a transformer 32, a rectifier unit 33, and an LC filter unit 34. It is.
The DC / DC converter unit 3 switches the DC input voltage V _in by the four switching elements Q _{1 to} Q ₄ and converts it to a desired DC output voltage V _out .

In the four switching elements Q _{1 to} Q ₄ constituting the bridge circuit unit 31, the switching elements Q ₁ and Q ₄ constitute a first pair, and the switching elements Q ₂ and Q ₃ constitute a second pair. As shown in B), the switching elements constituting the same pair are simultaneously turned on or off under the control of the control unit 4. The switching elements Q ₁ and Q ₄ constituting the first pair and the switching elements Q ₂ and Q ₃ constituting the second pair are alternately turned on or off.

The ON times of the switching elements Q _{1 to} Q ₄ during one switching period T _sw are all T _d . In the charging device 1 according to the present invention, the control unit 4 adjusts the ratio of the ON time T _d to one switching period T _sw (in the present invention, this ratio is “duty ratio Duty _sw ”). The output voltage _Vout is finely adjusted, and the output ripple is reduced.

As shown in FIG. 2A, the turns ratio of the transformer 32 is 1: N. For this reason, the peak value of the voltage V _d after full-wave rectification by the rectifier 33 is “V _in × N”, and the voltage value of the DC output voltage V _out obtained by smoothing the voltage V _d by the LC filter 34 is “V _d × Duty _sw ”.
From the above, in the charging device 1 according to the present embodiment, the following expression is established.

V _out = V _in × Duty _sw × N (3)

FIG. 3 is a block diagram of the control unit 4 and its peripheral parts. As shown in the figure, the control unit 4 is composed of, for example, a microcomputer, and among the charging power command value sent from the host controller via the CAN communication line and various sensors provided in the charging device 1, The switching elements Q _{1 to} Q ₄ of the DC / DC converter unit 3 are controlled based on detection results of the zero cross detection unit 6, the voltage detection unit 10, and the output current detection unit 11.

The zero-cross detector 6 detects a timing t _{0 at} which the polarity of the AC voltage supplied from the AC power supply 100 is inverted, and outputs a pulsed synchronization signal (see FIG. 4) at the timing t ₀ . The voltage detection unit 10 detects the voltage value of the DC output voltage _Vout output from the DC / DC converter unit 3, and outputs a signal corresponding to the voltage value.
The output current detector 11 detects the current value of the output current flowing through the battery 101 (charging current of the battery 101), and outputs a signal corresponding to the current value.
The output signals of the voltage detection unit 10 and the output current detection unit 11 may be analog signals or digital signals, but in the case of analog signals, an AD converter (not shown) provided in the control unit 4 Is converted into a digital signal. Moreover, it is preferable that the output signal of the voltage detection part 10 and the output current detection part 11 is input into the control part 4 via a suitable insulation circuit.

The control unit 4 includes a reception unit 41, a target charging current calculation unit 42, a duty ratio calculation unit 43, a PWM unit 44, a ripple rate storage unit 45, and a ripple amount calculation unit 46. Among these, the receiving unit 41 receives the charging power command value sent from the host controller and passes it to the target charging current calculation unit 42. The target charging current calculation unit 42 divides the commanded charging power value by the voltage value of the DC output voltage _Vout detected by the voltage detection unit 10 to calculate a target charging current value.

The duty ratio calculation unit 43 is based on a feedback control amount FB for reducing the deviation between the calculated target charging current value and the current value detected by the output current detection unit 11, and a ripple amount R described later. The duty ratio Duty _sw is calculated, and the duty ratio Duty _sw is output to the PWM unit 44.
The PWM unit 44 has a function of _receiving a duty ratio Duty _sw and outputting a PWM signal having a cycle T _sw and an on-time _Td .

The duty ratio calculation unit 43 is additionally provided with a limiter as necessary. When the result of each calculation for calculating the duty control amount S _duty overflows or underflows, the limiter performs processing for fixing the calculation result to a predetermined upper limit value or lower limit value.

In the ripple ratio storage unit 45, an expected ripple ratio α (= V _ripple / V _ave , see FIGS. 4 and (2)) is stored in advance. There are various ways of predicting the ripple rate α, but in this embodiment, focusing on the fact that there is a certain correlation between the current value of the output current and the ripple rate α, it can be obtained experimentally or by simulation. The ripple rate α under various output current conditions is stored.
Therefore, by referring to the ripple rate storage unit 45, the ripple rate α can be specified only by specifying the current value of the output current. That is, the ripple rate α can be specified without performing extraction using a digital filter.

Based on the current value detected by the output current detection unit 11, the synchronization signal output from the zero cross detection unit 6, and the ripple rate α read from the ripple rate storage unit 45, the ripple amount calculation unit 46 uses the following equation. The ripple amount R is obtained.

R = 1-α × cos ( 2πf r × t) ··· (4)

Ripple frequency f _r can be determined by certain compute the inverse of the time (period of the synchronization signal) T _r to the next synchronization signal from the synchronization signal is outputted is outputted. The time t is an elapsed time from the time t ₀ when the synchronization signal is output.
According to the above equation (4), as shown in FIG. 4, the minimum value of “1-α” is shown at the timing when the polarity of the AC voltage is inverted, that is, at the timing t ₀ when the synchronization signal is output, and the AC voltage The ripple amount R indicating the maximum value of “1 + α” is obtained at the timing when reaches the peak. That is, it is possible to obtain a ripple amount R in synchronization with the ripple in the DC input voltage V _in.

Refer to FIG. 3 again. The duty ratio calculation unit 43 calculates the duty ratio Duty _sw by dividing the feedback control amount FB by the ripple amount R.

_{Duty sw = FB / {1-} α × cos (2πf r × t)} ··· (5)

(3) by substituting the V _in the expression (2), further, substituting Duty _sw (3) equation Duty _sw to (5),

_{V out = V ave × {1} -α × cos (2πf r × t)} × Duty sw × N
_{= V ave × {1-α} × cos (2πf r × t)} × FB / {1-α × cos (2
πf _r × t)} × N

Next it is offset by (2) "1-α × cos (2πf r × t)" in the formula (5) wherein "1-α × cos (2πf r × t)". As a result, the DC output voltage V _out is expressed in the form of the following equation that does not include a term relating to ripple.

V _out = V _ave × FB × N (6)

As described above, according to the charging device 1 of the present invention, by controlling the duty ratios of the switching elements Q _{1 to} Q ₄ based on the value proportional to the inverse of the ripple amount R _in the DC input voltage Vin. Therefore, the output ripple can be surely offset.
The target charging current value can be obtained, for example, by dividing the charging power command value by the voltage value of the DC output voltage _Vout detected by the voltage detection unit 10.

[Second Embodiment]
In the charging apparatus according to the second embodiment, focusing on the fact that there is a certain correlation between the target charging current value and the ripple rate α, various target charging current conditions obtained experimentally or by simulation are used. Is stored.
According to the charging device according to the present embodiment, the ripple rate α can be easily specified based on the target charging current value, so that a digital filter is not necessary.

  Since the other configuration of the charging device according to the present embodiment is the same as that of the charging device 1 according to the first embodiment, the description thereof is omitted.

[Third Embodiment]
The charging device according to the third embodiment includes a housing that houses at least the DC / DC converter unit 3 and a temperature detection unit 7 that detects the temperature TH ₁ in the housing (see FIG. 1). In the charging device according to this embodiment, focusing on the fact that there is a certain correlation between the temperature TH ₁ in the housing and the ripple rate α, various temperature conditions obtained experimentally or by simulation. Is stored.
According to the charging device according to the present embodiment, the ripple rate α can be easily specified based on the temperature TH ₁ only by specifying the temperature TH ₁ in the housing, so that a digital filter is not necessary.

  Since the other configuration of the charging device according to the present embodiment is the same as that of the charging device 1 according to the first embodiment, the description thereof is omitted.

Note that the signal corresponding to the temperature TH ₁ output from the temperature detection unit 7 may be an analog signal or a digital signal like other output signals, but if it is an analog signal, the control unit 4 is converted into a digital signal by an AD converter (not shown) provided in 4. Moreover, it is preferable that the output signal of the temperature detection part 7 is input into the control part 4 via a suitable insulation circuit.

As mentioned above, although preferable embodiment of the charging device which concerns on this invention was described, this invention is not limited to said structure.
For example, the ripple amount calculation unit 46 may have a cosine table in which the calculation result of the cos function is stored in advance. According to this configuration, it is not necessary to calculate the cos function each time a new ripple amount R is calculated, and the processing burden can be further reduced.
The frequency f of the AC voltage supplied from the AC power supply 100 so 50Hz or 60 Hz, the ripple frequency f _r becomes either 100 Hz, the 120 Hz.
Therefore, the cosine table and cosine table when the ripple frequency f _r of 100 Hz, it is preferable that the ripple frequency f _r contains a cosine table when the 120 Hz.

  Moreover, in the said embodiment, the ripple rate corresponding based on either the current value (1st Embodiment) of output current, target charging current value (2nd Embodiment), and the temperature in a housing (3rd Embodiment). Although α is specified, the ripple rate α can also be specified by a combination thereof. For example, when specifying the ripple rate α based on the current value of the output current and the temperature in the housing, by storing a plurality of correspondence relationships between the ripple rate α and the output current for each temperature, the ripple rate α Can be specified.

  Further, the method of the DC / DC converter unit 3 is not limited to the full bridge method, and various methods such as a flyback method and a push-pull method can be adopted.

  Further, among the various sensors 5 to 11 shown in FIG. 1, the input voltage detection unit 5, the input current detection unit 8, and the converter temperature detection unit 9 that are not mentioned in the description of each embodiment are omitted. Can do.

DESCRIPTION OF SYMBOLS 1 Charging apparatus 2 Rectification smoothing part 3 DC / DC converter part 4 Control part 5 Input voltage detection part 6 Zero cross detection part 7 Temperature detection part 8 Input current detection part 9 Converter temperature detection part 10 Voltage detection part 11 Output current detection part 21 AC filter unit 22 Protection unit 23 Rectification unit 24 Power factor improvement unit 25 Smoothing capacitor 31 Bridge circuit unit 32 Transformer 33 Rectification unit 34 LC filter unit 41 Reception unit 42 Target charging current calculation unit 43 Duty ratio calculation unit 44 PWM unit 45 Ripple rate Storage unit 46 Ripple amount calculation unit

Claims (4)

A rectifying / smoothing unit that rectifies and smoothes an AC voltage to generate a DC input voltage, a DC / DC converter unit that switches the DC input voltage with at least one switching element to convert it to a DC output voltage, A control unit for controlling a duty ratio, and charging a battery with the DC output voltage,
A zero cross detector that outputs a synchronization signal at a timing t ₀ when the polarity of the AC voltage is inverted ;
The controller is
A ripple rate storage unit in which the expected ripple rate α is stored in advance;
Ripple at the DC input voltage including a term of α × cos (2πf _r × t) (where f _r is a ripple frequency and t is an elapsed time from t ₀ ) based on the synchronization signal and the ripple rate α. A ripple amount calculator for determining the amount;
A duty ratio calculation unit for calculating a duty ratio of the switching element is divided by the front cut pull amount feedback control amount obtained by the feedback control
Charging apparatus characterized by have a. An output current detector that detects a current value of an output current flowing through the battery;
In the ripple rate storage unit, a plurality of the ripple rates α corresponding to the current value of the output current is stored in advance,
The charging device according to claim 1, wherein the ripple amount calculation unit obtains the ripple amount based on the ripple rate α corresponding to the detected current value of the output current . A voltage detection unit for detecting a voltage value of the DC output voltage;
The controller is
A receiving unit for receiving the charging power command value;
A target charging current calculation unit that calculates a target charging current value based on the charging power command value and the detected voltage value of the DC output voltage;
Further comprising
The ripple rate storage unit stores in advance a plurality of the ripple rates α corresponding to the target charging current value,
The charging device according to claim 1, wherein the ripple amount calculation unit obtains the ripple amount based on the ripple rate α corresponding to the detected voltage value of the DC output voltage . A housing that houses at least the DC / DC converter section;
A temperature detection unit for detecting the temperature in the housing;
The ripple rate storage unit stores a plurality of the ripple rates α corresponding to the temperature,
The said ripple amount calculation part calculates | requires the said ripple amount based on the said ripple rate (alpha) corresponding to the detected said temperature, The charging device as described in any one of Claim 1 to 3 characterized by the above-mentioned.

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