| 摘要 |
<p>A DC-DC converter has a switch 7 connected between DC input terminals (4, 5) via a primary winding (N1) of a transformer (6). The transformer (6) has a secondary winding (N2) connected to a first rectifying smoothing circuit (9) and a tertiary winding (N3) connected to a second rectifying smoothing circuit (10). In order to obtain a constant DC output voltage, a switch control pulse generation circuit (18) is connected to a control terminal of the switch (7). In order to intermittently stop on/off control of the switch (7) during light load, an intermittence instruction generation circuit (19) is connected to the switch control pulse generation circuit (18). An intermittence instruction inhibition circuit (20) judges whether a control power source voltage Vcc is lowered to a predetermined value. When the control power source voltage Vcc is lowered to the predetermined value, the intermittence instruction of the intermittence instruction generation circuit (19) is invalidated.</p> |
