INTEGRATED CIRCUIT AND POWER SUPPLY CIRCUIT

To provide an integrated circuit that appropriately controls a transistor of a power supply circuit depending on a load state.SOLUTION: An integrated circuit 32 drives a transistor of a power supply circuit, the power supply circuit generating a predetermined level of output voltage to a load from an input voltage and including a transformer that includes a primary coil, a secondary coil, and an auxiliary coil and the transistor that controls a current flowing through the primary coil. The integrated circuit comprises: a first determination circuit (a control circuit 40) that determines whether the load is heavy or light; a second determination circuit that determines whether a mode is a continuous mode in which a current of the secondary coil does not become zero or a discontinuous mode in which the current of the secondary coil becomes zero when the transistor is in an off-state; an oscillation circuit 43; and a switching control circuit 44. The switching control circuit, when the load is in a light-load state, controls switching of the transistor on the basis of the determination result of the second determination circuit and an oscillation signal, and when the load is in a heavy-load state, controls switching of the transistor on the basis of the oscillation signal irrespective of the determination result of the second determination circuit.SELECTED DRAWING: Figure 2 【課題】負荷の状態に応じて適切に電源回路のトランジスタを制御する集積回路を提供する。【解決手段】１次コイル、２次コイル及び補助コイルを含むトランスと、１次コイルに流れる電流を制御するトランジスタと、を含み、入力電圧から所定レベルの出力電圧を負荷に対して生成する電源回路のトランジスタを駆動する集積回路３２であって、重負荷か軽負荷かを判定する第１判定回路（制御回路４０）と、前記トランジスタがオフの際に２次コイルの電流がゼロとならない連続モードであるか又はゼロとなる不連続モードであるかを判定する第２判定回路と、発振回路４３と、スイッチング制御回路４４と、を備える。スイッチング制御回路は、負荷の状態が軽負荷の場合、第２判定回路の判定結果及び発振信号に基づいてトランジスタのスイッチングを制御し、重負荷の場合、第２判定回路の判定結果に関わらず発振信号に基づいてトランジスタのスイッチングを制御する。【選択図】図２