Functional description

L9524C

20/27

4.12

Advanced run-off control

In transistor mode (modes 3 to 6) the glow plugs are switched by an advanced run-off

control. The target is to minimize changes in the load current. Therefore, the PWM signals

applied to the glow plugs are phase-shifted to each other. There is a 5-step start-up

procedure at the beginning of a switching sequence. In step 1 the phase shift between the

first period of the PWM control input signal (CI) and are heated up quite simultaneously.

During the start-up procedure the phase shift becomes a value equal to the on time of one

glow plug. As a result, after the start-up procedure the glow plugs are switched on one after

the other to get minimal changes in the load current.

Figure 8.

Timing diagram of advanced run-off control

4.13

Output timing

and switching on the next one to avoid overlaps. Additionally, failures occurring during the

Figure 9.

Output timing