STK672-442BN-E

No.A2249-21/28

Fixed current control time, t2, for each excitation mode

(1) 2-phase excitation

t2 = (2

CLOCK) - (t1 + t3) ······················· (4-9)

(2) 1-2 phase excitation

t2 = (3

CLOCK) - t1 ······························ (4-10)

(3) W1-2 phase excitation

t2 = (7

CLOCK) - t1 ······························ (4-11)

(4) 2W1-2 phase excitation (and 4W1-2 phase excitation)

t2 = (15

CLOCK) - t1 ····························· (4-12)

For the values of Vsat and Vdf, be sure to substitute from Vsat vs IOH and Vdf vs IOH at the setting current value IOH.

(See pages to follow)

Then, determine if a heat sink is necessary by comparing with the

Tc vs Pd graph (see next page) based on the calculated

average output loss, HIC.

For heat sink design, be sure to see ‘5. Thermal Design’.

The HIC average power, PdAVex described above, represents loss when not in avalanche mode. To add the loss in

avalanche mode, be sure to add PAVL (4-13, 14) using the formula (3-2) for average power loss , PAVL, for STK672-4**

avalanche mode, described below to PdAVex described above.

When using this IC without a fin, always check for temperature increases in the set, because the HIC substrate temperature,

Tc, varies due to effects of convection around the HIC.

4-2. [Calculating the average power loss, PAVL, during avalanche mode]

The allowable avalanche energy, EAVL, during fixed current chopping operation is represented by Equation (3-2) used

to find the average power loss, PAVL, during avalanche mode that is calculated by multiplying Equation (3-1) by the

chopping frequency.

PAVL=VDSSIAVL0.5tAVLfc ············································································· (3-2)

fc: Hz units (fc is set to the PWM frequency of 50kHz.)

Be sure to actually operate an STK672-4** series and substitute values found when observing operations on an

oscilloscope for VDSS, IAVL, and tAVL.

The sum of PAVL values for each excitation mode is multiplied by the constants given below and added to the average

internal HIC loss equation, except in the case of 2-phase excitation.

1-2 excitation mode and higher: PAVL(1)=0.7

PAVL ····················································(4-13)

During 2-phase excitation and motor hold: PAVL(1)=1

PAVL(4-14)