Tweet

Posted on 17 July 2019

Transfer Mold PFC Series with Compact Package

Free Bodo's Power Magazines!

 

 

 

Its application is expected to cover home appliance and motor drives

This article presents a new version of Mini Dual In-line Package Power Factor Correction (DIPPFCTM) developed by Mitsubishi Electric Corporation for high power air conditioners and general inverter use. In the new DIPPFC series, low thermal resistance was realized by using an insulation sheet structure with high heat dissipation. Because of the low thermal resistance, package size of the Mini DIPPFC is reduced compared to the conventional large DIPPFC and input current rating is expanded up to AC 30Arms.

By Masahiro Kato, Teruaki Nagahara, Hisashi Kawafuji, Toshiya Nakano, Marco Honsberg Power Device Works, Mitsubishi Electric Corporation, Japan

 

Inverters are increasingly used in motor control systems in order to improve efficiency and controllability of the system. For this inverter market, Mitsubishi Electric developed the Intelligent Power Module DIPIPMTM with a transfer mold structure. DIPIPM’s are used for white goods such as air-conditioners and industrial motors. The inverter system involves higher harmonic current. So in the inverter system, a function to reduce the higher harmonic current is needed. Mitsubishi Electric developed the DIPPFC as a power module to reduce the higher harmonic current.

"Large DIPPFC series (AC 264Vrms/up to 20Arms)" have been on sale since 2002, and it is used for package air-conditioners. This article describes a new version of DIPPFC "Mini DIPPFC series” to expand the current rating up to 30Arms with a more compact size compared with conventional Large DIPPFC. This new version DIPPFC series contributes to the miniaturization of the inverter PCB. Figure 1 shows an outline view of the Mini DIPPFC.

Outline view of Mini DIPPFCTM

Configuration of DIPPFCTM

In recent years, high harmonic currents generated in electric power systems are restricted in all electronic equipment. Especially in the EU where IEC62019-3-2 is applied, the high harmonic current regula- tion are severe, and the application of PFC (Power Factor Correction) is advanced. The power factor correction circuit shown in Figure 2 is now widely used. This circuit is composed of the diode bridge, the switching device and the boost diode. In the DIPPFC, the highside diode of the diode bridge has the function of boost diode, and an IGBT is added in parallel with the low-side diode of the diode bridge, as shown in Figure 3.

Figure 2 - Power Factor Correction circuit (1 chip type)

Figure 3 - Power Factor Correction circuit (DIPPFCTM type)

Therefore, DIPPFC has the functions of rectification and power factor correction. DIPPFC includes a driver IC for the IGBTs as shown in Figure 2.

New package structure

Figures 4 and 5 show cross-sectional drawings of a Mini DIPPFC compared with a Large DIPPFC. DIPPFC (including DIPIPM) series are simply made up of power chips (IGBTs, diodes), drive ICs and assembly components (lead frame, Al/Au wire, resin, etc.). Bare power chips and ICs are assembled directly on a lead frame and connected by Al wire or Au wire, and then they are transfer molded.

Structure of Large DIPPFCTM

Heat dissipation structure

In Large DIPPFC, the insulating layer between lead frame and built in heat-sink is formed by epoxy resin. In order to reduce the thermal resistance, a ceramic-powder filler with high thermal conductivity was incorporated in the epoxy resin However this technology has reached its limits of insulation strength and heat dissipation through the epoxy resin because of the fluidity properties of the filler.

Structure of Mini DIPPFCTM

To solve the problem, the new heat dissipation structure with insulating resin sheet has been adopted in the Mini DIPPFC as shown in Figure 5. The insulating resin sheet does not need very much fluidity, in contrast to the epoxy resin, thus it is possible to increase the amount of filler in the resin sheet. By using this resin sheet, the thickness of the insulating layer can be thinner compared with that of the epoxy resin isolation in the Large DIPPFC. Therefore, the thermal dissipation can be improved considerably. As a result, the thermal resistance was improved 35% compared to the Large DIPPFC (as shown in Figure 6).

Comparison of thermal resistance

Compact Package size

Effective heat dissipation of the power chips is achieved by applying the new heat dissipation structure with an insulating resin sheet, thereby the power chip size could be shrunk appropriately. Through the optimization of chip size, the package size of Mini DIPPFC is considerably reduced to about 70% of the Large DIPPFC, though the current rating is up to 30Arms. Mini DIPPFC package size is shown in Figure 7.

Package size of Mini DIPPFCTM

Electrical circuit configuration and components

The internal circuitry of Mini DIPPFC comprises two IGBT chips, four diode chips and LVIC driver, which is the same as the Large DIPPFC. The LVIC is designed with necessary functions such as IGBT drive, control power supply, under voltage (UV) lockout circuit. Figure 8 shows the internal circuit of Mini DIPPFC.

Internal block diagram of DIPPFCTM

Characteristics

Optimization of power chips

In the PFC operation it is necessary to operate the switching device with a high frequency to avoid the audible tone from the reactor. The IGBT chips are designed for high speed switching with a trench gate structure. Diode chip performance can be optimized - high speed characteristics are suitable for the high-side diode (as shown in Fig. 2) and low forward voltage characteristics are suitable for the low-side diode to reduce the total power loss. So the high-side diodes are designed as fast recovery type and the low-side diodes are designed as low forward voltage type respectively. For the large DIPPFC all diode characteristics are the same. The result of the optimization is that the total power loss of Mini DIPPFC was improved 8% compared to Large DIPPFC as shown in Fig. 9. (In the condition of Vin=220Vrms, Vout=390V, ACL=0.6mH, fc=20kHz, Tj=125°C).

Comparison of module total loss

Expansion of allowable case temperature area

Because thermal resistance was improved as described above, the temperature rise between IGBT junction and module case (ΔT(j-c)) was able to be decreased by about 40% compared with Large DIPPFC. Fig. 10 shows the temperature rise between IGBT junction and module case (LT(j-c)) of Mini DIPPFC (PS51787) and Large DIPPFC (PS51259-AP).

Comparison of IGBT T(j-c)

As a result, the allowable case temperature has been increased compared with Large DIPPFC (as shown in Fig. 11). This increase of allowable case temperature and the improvement of the module total power loss as described above can contribute to the cost of the cooling system.

Allowable case temperature area

Electrical performance

The main electrical characteristics (main part and control part) of Mini DIPPFCTM are indicated in Table 1.

Table 1

Control of DIPPFCTM

PFC control IC M63914FP is recommended for control of the DIPPFC. M63914FP has several functions as: PWM control of DIPPFC, soft start function, over voltage protection, over current protection, control power supply undervoltage lockout circuit and over temperature. About 99% power factor can be achieved by using Mini DIPPFC with M63914FP. The input current and input voltage wave form which was operated by PS51787 and M63914FP are indicated in Figure 12.

Input voltage-current waveform of PS51787

View in the future

In order to improve the current rating to more than 30Arms it is necessary to develop further heat dissipation. Development of a larger current rating capacity is the next target by further improvement of thermal resistance and power device loss.

Conclusions

A new Mini DIPPFC has been developed by optimised power chips together with a high heat dissipating insulation sheet. This development contributes to the extension of the applications and miniaturization of the inverter system. Its application is expected to cover both home appliance use and general motor drives. Mitsubishi are continuously making efforts to develop devices of excellence to realize power loss reduction and save natural resources.

 

 

VN:F [1.9.17_1161]
Rating: 0.0/6 (0 votes cast)

This post was written by:

- who has written 791 posts on PowerGuru - Power Electronics Information Portal.


Contact the author

Leave a Response

You must be logged in to post a comment.