| 摘要 |
The circuit arrangement is used for controlling the duty factor of an electronic switch (21) in dependence on a supplied controlling direct voltage (Ust), the switch (21) being located in an alternating-current path (U &tilde& ). Such circuits are used for preheating a control resistor for the charging controller controlling a charging-electrical storage heater. The circuit arrangement generates bursts of an alternating voltage, the relative RMS value of which across a load resistor changes in proportion to the controlling direct voltage (Ust). To achieve the object, an integrator (12/18) is provided to the input of which the direct voltage (Ust) is applied, also a Schmitt trigger (19) which is located in the output (17) of the integrator (12/18) and which controls an electronic switch (21) in the circuit of the alternating voltage (U &tilde& ). Furthermore, a feedback of the pulsed alternating voltage via a threshold switch (28) to the input of the integrator (12/18) is provided. <IMAGE>
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