Integrated circuit for controlling a switching power supply
View Patent ↗An integrated circuit for controlling a switching power supply includes a signal input terminal in addition to a switching input terminal that is also provided in a conventional integrated circuit and is a terminal to switch IC operation modes using an external control signal. The switching input terminal signal is made valid when the signal input terminal voltage is higher than a threshold voltage, such that mode switching using an external control signal is enabled. When the signal input terminal voltage is lower than the threshold voltage, mode switching is automatically conducted by switching a MOSFET ON or OFF using output signals of portions of a comparator connected to a feedback terminal to which an output voltage of a power supply device is applied.
1. An integrated circuit for controlling a switching power supply, the integrated circuit judging whether or not a load is light by comparing a comparison signal with a triangle wave or a saw-tooth wave by using a PWM comparator and switching between a standby operating mode and a normal operating mode in response thereto, the integrated circuit comprising:
a first setting terminal that manually sets, without recourse to the comparison signal, the switching between the standby operating mode and the normal operating mode, and
a second setting terminal that sets the switching between the standby operating mode and the normal operating mode either to be automatically performed based upon the comparison signal or to be manually performed without recourse to the comparison signal.
2. The integrated circuit of claim 1 , wherein the second setting terminal includes a function of setting a threshold voltage for automatically switching between the normal operating mode and the standby operating mode and is configured such that the threshold voltage is adjustable from outside the integrated circuit.
3. The integrated circuit of claim 2 , wherein the threshold voltage is generated by dividing a power supply voltage using a resistive voltage divider.
4. The integrated circuit of claim 1 , including a terminal that can set a delay time for switching between the normal operating mode and the standby operating mode after detecting an operating mode switching signal.
5. The integrated circuit of claim 4 , wherein the delay time is generated by a charge/discharge circuit comprising a constant current circuit, a switching element and a capacitor.
6. The integrated circuit of claim 1 , wherein the comparison signal is a signal fed back from a secondary side of an insulated switching power supply to a primary side thereof via a photocoupler.
7. The integrated circuit of claim 1 , wherein the comparison signal is an error signal generated by an error amplifier from a reference voltage and a signal fed back from an output of a non-insulated switching power supply.